Jain Sir Paper Jan-mar 2013

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Paper No. 586 “Disaggregated Modeling of Mode Choice by Ann - A Case Study of Ahmedabad 3 City in Gujarat State” P. S. Ramanuj and P. J. Gundaliya

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R.K. Srivastava, K.K. Shukla and S.K. Duggal

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P. K. Jain

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Journal of the Indian Roads Congress, January-March 2013

1 INTroduCTIoN

The 20th century has witnessed an accelerated industrialization world wide to result in to the life style changes which has taken place with concentration of population at settlements with high industrial base.

The factors like the economic growth, increased income and the mobility motive have encouraged the people to opt for private vehicles. Also, the inadequate availability, substandard quality and service of city’s public transportation have further accentuated the trend of using private vehicles in the state. Though there have been considerable improvements in the service of public transport facilities in most of the cities with growing economy, there still remains a considerable gap between demand and supply of transport facility.

Principal concerns of the planners of urbanization are the evolution in the usage pattern of the urban land and demand profiles of the related transportation. Appreciable efforts have been made till date to understand intricacies involved in dynamic system

of human settlements which form the vital basis for transportation planning. In the transport planning, mode split is a complex entity and the model for mode split can be developed by using various behavioural theories. The nature of traffic on the roads results from individual decisions taken by the travelers for choosing the mode of travel but it is, however, very complex and difficult to predict human behaviour.

2 oBJeCTIVe of The sTudY

The main objectives of present study are:

i) To understand the travel pattern in the study area.

ii) To develop an Ann based choice model.iii) To understand the influence of the various

parameters in the functioning of the model.

iv) To develop a choice model based on regression technique.

Paper No. 586

dIsaggregaTed modelINg of mode ChoICe BY aNN -a Case sTudY of ahmedaBad CITY IN guJaraT sTaTe

P. S. Ramanuj* and P. j. Gundaliya**

aBsTraCT

Traveling is an integral part of today’s life style for people across the world. The increased traveling has led to a number of serious problems like congestion, noise pollution, air pollution, greenhouse effect etc. In the transportation planning, the choice of a transportation mode is one of the most important parameter and it is difficult to predict the same as it depends on human behaviour which is very complex in nature. By far, most of the Discrete Mode Choice models are based on the principle of “random utility maximization” derived from the Econometric theory. However, in the present study the Artificial Intelligence technique is used for modeling of the Mode choice behaviour.

Further, an attempt has been made to predict the mode choice by using neural network technique. The present study is aimed at introducing a new modeling technique Artificial Neural Network abbreviated as ANN. An ANN is inspired by biological neurons as it learns from past. The ANN is best suited for the problems where input variable are complex in nature1. The study provides guidelines in deciding network architecture for the behaviour model. For efficient use of Ann technique it is required to decide types of activation functions, the number of neuron/s in different layers and the amount of data used for the training. The data used for the present study were collected from the household travel survey conducted in the Ahmedabad city of Gujarat state for the Public Transportation System. In the study an attempt has been made to find out the sensitivity of the various parameters in the model. Same data is also analyzed by linear regression method to obtain utility function and finally the output of ANN model is compared with the regression model.

* Lecturer in Civil Engg. Deptt., L.D. College of Engg., Ahmedabad, E-mail:[email protected]** Assistant Prof., Civil Engg. Deptt., L.E. College of Engg., Morbi, E-mail:[email protected]

Written comments on this Paper are invited and will be received upto 15th May, 2013

Ramanuj and Gundaliya on


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v) To compare the reliability quotient of Ann model with that derived from the regression model.

3 lITeraTure reVIeW

Travel demand theory was introduced in context of trip generation. The core of the field is a set of models which were developed on the basis of the work done by Warner (1962) who investigated classification techniques using models from biology and psychology2. Beginning with Warner (1962) and followed by the work of other early investigators, disaggregate demand models emerged. Here the analysis can be termed as disaggregate since the individuals are the basic units of observation, yet aggregate since these models yield a single set of parameters describing the choice behaviour of the population. Behaviour has to be taken into account since the theory uses the concepts of ‘consumer behaviour’ from the discipline of economics and ‘choice behaviour’ concepts from the discipline of psychology. Researchers at the University of California, Berkeley especially Daniel McFadden and the Massachusetts Institute of Technology (Moshe Ben-Akiva) have developed what has been known as Choice Models, Direct Demand Models (DDM), Random Utility Models (RUM) or, in its most prevalent form, the Multinomial Logit Model (MnL)3. Particularly, the use of neural computing for transportation application began much more recently and work to date has been of an explanatory nature. Faghri and Aneja (1996) have found that Ann based models capture the relationship between trip production rates and the independent variables more accurately than regression model4. Recently Sikdar P. K. and Sekhar R. (2005) have used Ann for mode choice. Their article reported the result of an analysis of the mode-choice behaviour of commuters in nagpur. In their study mode choice behaviour model has been developed by using Ann techniques. A multilayer feed forward neural network was considered and back propagation algorithm was selected for training. The relative importance of input variables is found by the proportioning of weight algorithm which was suggested in the paper of Sikdar P. K. and Sekhar R., (2005)5. Yarlagadda, Amith and

Srinivasan S.(2007) conducted a detailed study for understanding the school-travel behaviour of children and the related interdependencies among the travel patterns of parents and children6.

4 arTIfICIal Neural NeTWorK

Artificial neural network is a system loosely modelled on the human brain. aNN models have become more popular in recent years and are being used in diversified fields like financial analysis, cognitive science, decision making problems and pattern recognition. Ann can also be applied to dynamic traffic pattern classifications as was done by Jiuyi and Faghri. Evaluation of applications developed on neural network theory in the field of transportation engineering is presented by Faghri and Hua (1992)7.

The fundamental building block of Ann is a neuron, which is a processing element. A schematic diagram of a typical with neuron is shown in Fig.1

A set of inputs labeled X1, X2,.., Xn are applied to the artificial neuron, each representing the output of another neuron. These inputs collectively referred to as the input vector ‘X’, corresponding to the signal into the synapses of a biological neuron. Each signal (input) is multiplied by an associated weight Wji before it is applied to the summation block, labeled ΣWijXij –bj .

The set of weights collectively referred to as the weight vector ‘W’, corresponds to the strength of a single biological synapses connection. The operations described here constitute a linear-combiner. In addition, it has a bias term b, a threshold value that has to be reached or exceeded for the neuron to produce a signal. A non-linearity or activation function that acts on the other neurons.

Fig. 1 Model of neuron


diSaGGReGated modelinG of mode ChoiCe by ann - a CaSe Study of ahmedabad City in GujaRat State 5

The output of the neuron can be expressed mathematically as

Oi=fi(ui) ...1

Where

i and j is number of neuron in the layers.

The purpose of the activation function is to ensure that the neuron response is bounded i.e. actual response of the neuron is conditioned, or damped, in response to a large or small activity stimuli and thus, is controllable. The various types of activation function used are shown in Fig 2.

aNN learning: Learning is the process by which the Ann is able to produce a correct output corresponding to a given input. It is somewhat similar to the condition when the network is able to generate the correct response to a given stimulus. The network learns either by a

supervised learning algorithm or by an unsupervised learning algorithm8.

The most popular activation functions are hard limiter and sigmoid. The proper activation function can be selected by experience or by trial and error in such that it can correlate input output relation efficiently.

Fig. 2 Typical activation function

Table 1 Number of registered Vehicles in ahmedabad

YearNo. of yearly

registered vehicles

Growth Rate Comparing

previous Year

1996-97 78525

1997-98 81121 3.30

1998-99 82585 1.80

1999-00 92286 11.70

2000-01 69811 -24.35

2001-02 74952 7.36

2002-03 91643 22.26

2003-04 109161 19.11

2004-05 136982 25.48

005-06 147560 7.72

2006-07 158290 7.27

(Source: Regional Transport Office, Ahmedabad)

Network architecture: In general, network architectures may be fundamentally classified into three different classes as listed.

a) single layer feed forward networks: It is the simplest form of a layered network. In this network, an input-layer of source nodes projects onto an output-layer of neurons.

b) feed forward networks: In this form of the network one or more layer, known as hidden layer, are added whose computational nodes are correspondingly called hidden neurons or hidden units as shown in Fig 3. The function of hidden neuron is to intervene between the external inputs and the network output in such a way that the accurate result is obtained.



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Fig. 3 Multiplayer neural network

For a given model a training set of input-output pairs, {(x(k), d(k))}, k=1,2 ……..,p, the back propagation algorithm performs two phases of data flows. First, the input pattern x(k) is propagated from the input layer to the output layer and as a result of this forward flow of data, it produces an actual output y(k). Then the error signals resulting from the difference between d(k) and y(k) are back propagated from the output layer to the previous layers for them to update their weights.

5 sTudY area aNd daTa sourCe

Ahmedabad is the commercial capital of the Indian State of Gujarat. It is located about 500 kms north of Mumbai and 1000 kms South West of new Delhi. Formerly it was known as the textile capital of India, it is also a major industrial and financial city contributing about 14% of the total investments in all stock exchanges in India and 60% of the total productivity of the State9,10. Due to the technological development in the automobile industry, there is a marked increase in the number of vehicles plying on road. As per Regional Transport Office (RTO), Ahmedabad, there is an average increase of number of vehicles by 9 to 10 % per annum10.

Table 1 summarizes number of vehicles registered yearly in Ahmedabad in the last decade. Table 1 also shows the percentage increase compared to previous year. It may be noted that year 2000-01 shows negative growth rate due to the earthquake and riots in Ahmedabad City.

The household survey was conducted for determining the feasibility of Bus Rapid Transit System (BRTS) project and to find the percentage of switch over to the use of public transportation by the traveling class11. For this, nine spots were identified for the data collection. Targets sampled per spot are 100-200 based on their economic conditions. From 9 identified spots a total of 1399 samples were surveyed out of which 1348 samples are filtered and used in the study.

6 mode ChoICe

Increased number of privately owned vehicles and the substandard quality and service of public transportation may be responsible for rapid generation of private trip. The traffic congestion patterns on the roads are directly influenced by the individual decisions made by commuters in choosing the mode of transport, time, route etc. Mode choice analysis is the third step in the conventional four-step transportation forecasting model, after the trip generation and trip distribution but before it comes to the assignment of route. A mode choice or modal split model is concerned with the trip maker’s behaviour regarding the selection of travel mode. It is usually assumed that various modes of urban transport are open to the trip- maker. An individual’s choice of travel mode is influenced by the following four main sets of factors12.

a) Personal characteristics: such as age, sex, income, car ownership etc.

b) Characteristics of the transport system: Such as travel cost, time, comfort, convenience, prestige etc.

c) Characteristics of trip: Such as purpose, length, urgency, peak, off peak etc.

d) Characteristics of the trip end: Such as home and work based trip, density etc.

c) feedback or recurrent Network: It distinguishes itself from a feed forward neural network in that it has at least one feedback loop. Feed back loops involve the use of particular brands composed of unit-delay elements, which result in a non-linear dynamical behaviour. The Feedback network learns new knowledge by adjusting these connection weights every time it propagates through feedback. The back propagation-learning algorithm is most useful in modeling and processing of many quantitative phenomena using neural networks.



In each of the above mentioned cases, the trip maker will make a choice based on only those characteristics which he perceives. They may well be less than the total set.

6.1 mode Choice model

Mode choice models can be aggregate or disaggregate. Aggregate models are based on zonal information whereas disaggregate models are based on household data and individual data or either of the two. Aggregate demand (first-generation) transportation models are either based on relations observed for groups of travelers, or on average relations at a zonal level. On the other hand, disaggregate demand (second-generation) models are based on observations of choices made by individual travelers13. The most common theoretical base for generating discrete choice models is the random utility theory.

6.2 random utility Theory

The utility is mathematically represented as a linear function of the attributes of the journey weighted by the coefficients which attempt to represent their relative importance as perceived by the traveler.

Model may further assume that the utility uin can be represented by two components:

i) A measurable systematic part ‘Vin’, which is the function of the measured attributes; and

ii) A random part ‘εin’, which reflects the measurement or observational error along with the taste of the individual.

The utility associated by individual n to alternative i, denoted by Uin is a random variable such that

uin=Vin+εin ... 2

Where, Vin∈r is the deterministic or systematic, component of the utility, and εin is a random term. If zin is a vector of attributes of alternative i for individuals

n, and sn is a vector of socio-economical characteristics for individual n, we have

Vin=Vin(β, zin,sin) ...3

Where, β is a vector of unknown parameters which are to be estimated. For simplification, it is a common practice to merge zin and Sn into a vector of attributes, denoted by xin. Therefore, we have a simpler formulation

Vin=Vin(β, xin ) ...4

The probability that individual n selects alternative i is given by

P (i\Cn ) = P (uin > uin ∀j ∈CN) ...5

The expression for this will depend on the distribution of random error term εin. In case the random residuals are independently and identically distributed (IID) Gumbel distributed, the expression will reduce to well-known Multinomial Logit Model (MnL) or if it is normally distributed then it will reduce to probit model, or if the random residuals are separately IID Gumbel distributed then it will reduce to Hierarchical nested Logit (nL) model. In case of Revealed Preference (RP) data this random error term (εin) is associated with the independent variables. This error can be assumed to be same for estimation and prediction cases and hence, the utility function estimated can be used directly for the prediction purposes.

7 aNN modelINg

Considering previous study outcomes and existing scenario the following variables are identified for the model development as listed in Table 2.

The general neural has a set of n inputs xi, where the subscript i take values from 1 to n and indicates the source of the input signal. The inputs to the neuron may come from the environment in which it is embedded or outputs of other neurons depending on the layer that the neuron is located in. Each input xi is weighted before reaching the main body of the processing element by the connection strength or the weight factor wi.



8

Multilayer feed forward neural network with signal hidden layer was considered as it is enough for complexity of the present data and back propagation algorithm was selected for training the network in which the error is propagated from the output layer backward with adjustment of the synaptic connection weights up to input layer.

Table 2 Variables Consider for mode Choice analysis

sr. No

description of Variables

Values

1 Household size Discrete

2 no. of car in Household Discrete

3 No. of 2-wheeler in Household Discrete

4 no. of Bicycle in Household Discrete

5 Household income (Rs) 1-<=2500 ; 2- 2501-5500 ; 3-5501-10000 ; 4-10001-15000; 5- >15000

6 Gender of traveler 1 Male; 2 Female

7 Age of traveller in years Discrete

8 Status of traveller 1 student ; 2 working

9 Distance travel (km) Discrete

10 Total travel time in minute Discrete

11 Travel cost (Rs) Discrete

The designing of network architecture includes identifying the number of layers, the number of nodes in each layer and synaptic connections between the nodes of the different layers. In the present study, a neural network topology is used which consists of input layer having 11 nodes, the hidden layer and output layer

having 6 nodes. One of the objectives of the present study is to evaluate the optimal neural network design developed for the present problem and to determine the relative interdependencies of the variables. MATLAB has been used for developing the software for the Ann model. Analysis of network sensitivity involves training each network by using different architecture, by varying number of hidden nodes and calculating the reliability level in the network.

7.1 optimization of the Network

The optimum network for the present problem is the one that yields the highest network performance level and has a minimum number of nodes in the hidden layer. The neural network reliability level (Refer Table 3) represents the accuracy of the model. It is observed that reliability increases by increasing the number of hidden nodes in hidden layer up to a certain extent. Less number of neurons causes inadequacy in mapping between input and output variables. While more number of neurons may be responsible for the over fitting of the model. To avoid over fitting of the model a validation check is introduced in the model. The optimum number of hidden nodes for mapping between input and output variables is considered as 18 which is shown in Fig 4. An optimum neural network in the present study is designed using 11 input nodes, 18 hidden nodes and 6 output nodes.

7.2 data division

It is a common practice to split the available data into sub-sets; namely a training set, an independent validation set and a testing set. Typically, Anns are unable to extrapolate beyond the range of data used for training14. Consequently poor forecast results when the validation data contain the values outside the range of those used for the training. The basic idea is to withhold the small subset of the data for the validation set and to train the network on the remaining data. After generalization with training and validation, the model is tested for data which is not used in above process. In the present study 20% data



Fig. 4 network Sensitivity with no. of Hidden nodes

It is clear from the Table 4 that optimum accuracy in all phases is found by allocating the data for training, validation and testing in the combination of 70%, 10% and 20% data respectively.

Table 4 sensitivity of NN Performance for Various Combination

Trial No.

No. of sample/(% of total sample) Network accuracy(%)

Training Validation Training Validation Testing

1 1079(80%) - 94.53 - -

2 1051(78%) 28(2%) 92.29 88.88 85.13

3 1011(75%) 68(5%) 90.11 88.06 83.52

4 944(70%) 135(10%) 94.49 90.31 89.55

5 810(60%) 269(20%) 85.43 77.61 80.67

6 674(50%) 405(30%) 91.54 82.18 79.18

7 539(40%) 539(40%) 88.87 71.59 75.47

7.3 mode-Wise accuracy in Various Phases

The multilayer feed forward neural network with 11 neurons in input layer, 18 neurons in hidden layer and 6 neurons in output layer is found optimum during the process of optimization and it is thereby froze. Data set divisions is done over a number of trials after reserving 20% data for testing model and optimum result is obtained when the data set is distributed 70% in training, 10 % validation and 20% independent data in testing. Mode-wise prediction success in different phases for the model is shown in Table 5, 6 and 7.

During training (refer Table 5) average prediction accuracy is found 95% which includes 100% accuracy in the car prediction (72/72) and minimum 87.1% accuracy (54/62) in the prediction of walking mode.

Table 5 Prediction Success in Trainingactual mode

Predicted mode Choice (Training)

Individual match(%)

Car 2 wh auto Bus Bicycle WalkCar(72) 72 0 0 0 0 0 100TW(486) 0 470 16 0 0 0 96.7Auto(68) 0 1 59 8 0 0 86.8Bus(133) 0 0 9 122 2 0 91.7Bicycle (123) 0 0 0 5 115 3 93.5

Walk(62) 0 0 2 1 5 54 87.1

Total(944) Correctly classified-892; Missed classified-52; Accuracy(%)-95

is randomly selected of the total data set and set apart to be used for testing the model accuracy without any bias. Remaining 80% data sets should be used for the training and validation purpose. Various combinations of training and validation data set size were used for the said purpose. Table 4 illustrates the Ann accuracy in training, validation and testing.

Table 3 sensitivity analysis for hidden Neuron

No. of hidden node

Correctly Classified

reliability level (%)

r2

4 1005 74.55 0.7933

6 1267 93.99 0.9619

8 1177 87.31 0.9230

10 1268 94.07 0.9620

12 1267 93.99 0.9613

14 1252 92.88 0.9570

16 1289 95.62 0.9751

17 1236 91.69 0.9479

18 1298 96.29 0.9792

19 1292 95.85 0.9760

20 1291 95.77 97.08



10

The Multi Regression model generates the relationship between one dependent and one or more independent variables. Generally regression analysis can be used to develop a mathematical relationship between independent and dependant parameters.

Table 7 Prediction success in Testing

actual mode

Predicted mode Choice(Testing) Individual match(%)

Car 2 wh auto Bus Bicycle Walk

Car(23) 21 1 1 0 0 0 91

TW(143) 0 3 140 0 0 0 98

Auto(15) 0 3 4 8 0 0 53

Bus(30) 1 28 1 0 0 0 93

Bicycle(37) 0 1 0 1 32 3 86

Walk(21) 0 0 1 0 7 13 62

Total(269) Correctly classified-242; Missed classified-27; Accuracy(%)-90

In the validation as shown in the Table 6 total prediction accuracy is found 85% which includes maximum accuracy of 92% in car prediction (22/24) and minimum accuracy of 46% (11/24) in the prediction of walking mode.

The model is tested by separated 20% data sets and the total prediction accuracy is found to be 90% which includes maximum 91% accuracy in car prediction (21/23) and minimum 62% accuracy (13/21) in the prediction of walking mode. Total missed classified mode is only 27 out of 269.

Table 6 Prediction Success in Validation

actual mode

Predicted mode Choice (Validation)

Individual match(%)

Car 2 wh auto Bus Bicycle Walk

Car(24) 22 0 2 0 0 0 92

TW(135) 5 1 129 0 0 0 96

Auto(25) 0 7 8 10 0 0 40

Bus(29) 0 28 0 1 0 0 97

Bicycle(32) 0 0 0 1 28 3 87

Walk(24) 0 0 1 1 11 11 46

Total(269) Correctly classified-228; Missed classified-41; Accuracy (%)-85

8 relaTIVe ImPorTaNCe of The INPuT ParameTers

neural network is quite good for the purpose of classification, but it fails to provide a basis for modeling a set of casual factors. Ann performance is good in predicting the observed choice correctly; however it suffers from accurate interpretation of the significance of input variables due to lack of required statistical computation tools. This is because Ann learns parameter behaviour by encoding it in a numerically assignable weight. This Black box image of the neural network is revealed by finding the effect of the variables on the output.

The relative importance of input variables is found by the proportioning of weights 5. For this purpose, all the variables are kept at its mean value except one variable and the relative change in the output with respect to change in that variable from mean up to half the value of standard deviation is determined.

The procedure is to be repeated for the all variables. In the present study, it is found that relative importance of the distance traveled, traveling cost, traveling time, and vehicle ownership is more which is shown in Fig 5.

Fig. 5 Relative Importance of Various Parameters



Regression model is developed using the same data used by artificial neural network model. Eleven input parameters and targeted vehicle mode choice are used. The input parameters are assumed independent from each other. The model development is done by regression function LINEST of the Ms Excel 2003 software. A utility function depicts the various modes of transportation. The utility function value from 1 to 6 indicates Car, Bus, Two wheelers, Auto, Bicycle and walking respectively. The utility function obtained for the data for a linear relationship is given as Eq. 6. This shows that variable X10 (Total travel time) and X11(Travel cost) are maximum influencing parameters.

U = –0.03973X1–0.19798X2–0.14226X3+0.097131X4– 0.11593X5+0.01285X6–0.15435X7–0.07586X8+ 0.1821X9–0.51298X10–0.51403X11+0.910347 ...6

The utility function depicting the non-linear relationship between the parameters is given in equation 7. This shows that variable X10 (Total travel time) and X11 (Travel cost) are maximum influencing parameters, however the effect of X11 is more as compared to X10 which is also observed in Ann analysis.

log U= –2.66413 – 0.03929log X1 – 0.2250X2 + 0.04027X3+0.03807X4–0.11398X5+0.00128X6–0.17947X7+0.01267X8+0.26848X9–0.32181X10–0.64011X11 ...7

where X1 to X11 are parameters as depicted in Table 2 respectively.

8.1 Comparison with aNN model

Mode choice modeling is a behavioural model and (system transfer function) input output relationship is non-linear and complex.

Table 8 Comparison of aNN and regression modelaNN model

linear regression

model

Non-linear regression

modelMSE 0.0965 0.999 0.9747

R2 0.9792 0.4272 0.4856% accuracy 90 43.6 44.40

Therefore, the prediction accuracy of the regression model is quite less as compared to Ann model. Table 8 shows comparison of different models.

CoNClusIoN

In the present case Artificial Neural Network model is developed using 1348 data collected from various areas of Ahmedabad city in Gujarat state at a micro trip level. The data is normalized before using in the model. 18 hidden nodes are found to be best for this model subject to compliance of certain conditions for over fitting. The distribution of the entire data for training and validation is done through various trials with 20 % data exclusively set apart for testing. The optimum performance is found when the data distributed for the training and validation and testing is 70%, 10% and 20% respectively. The accuracy achieved in the model respectively in training, validation and testing is 95%, 85% and 90%.

The black box image of the neural network is clarified by finding out relative importance of the explanatory variables considered for model calibration through proportioning of weights algorithm. It is observed that the parameters which highly affect the mode choice are Travel cost, Travel time, Travel distance, Vehicle ownership and Household income.

Linear and non-linear Regression model are also developed for the same data but the result obtained is quite poor as compared to Ann Model. Mean squared error in regression model is 0.9747 compared to 0.0965 for Ann model. Similarly, R2 in linear regression model is 0.427, for non-linear regression model is 0.485 while in ANN model it is 0.9792. Being highly compatible, Ann model should be used for the planning of various transport facility.

refereNCes

1. Yegnanarayana, B. (2001), “Artificial Neural networks”, Prentice-Hall of India Private limited, new Delhi, India.

2. Warner S. (1962), “Strategic Choice of Mode in Urban Travel: A study of Binary


12

Choice northwestern University Press”, The Transportation Centre.

3. Ben-Akiva, M. and Lerman S. (1985), “Discrete Choice Analysis: Theory and Application to Travel Demand”, MIT Press, Cambridge, Massachusetts.

4. Faghri, A. and Aneja, S. (1996), “Artificial neural network-Based Approach to Modeling Trip Production”, Transportation Research Record, Journal of TRB, vol 1556, pp. 131-136.

5. Sikdar, P.K. and Sekhar R. (2005), “Analysis of Artificial Neural Networks for Mode Choice Modeling” START- 2005, International Conference, IIT Kharagpur, India.

6. Yarlagadda, A.K. and Srinivasan, S. (2007), “Modeling Children’s School Travel Mode and Parental Escort Decisions”, Transportation, Volume 35, number 2, pp. 201-218.

7. Faghri, A. and J. Hua, “Seasonal Roadway Classification Using Neural Networks. Applications of Artificial Intelligence Techniques

in Transportation Engineering”, Engineering Foundation, pp. 363–381 (1992).

8. www.mathworks.com last accessed on 2nd Jan, 2009.

9. www.censusindia.gov last accessed on 23rd Dec., 2008.

10. Rathod S. and Gundaliya P.J. (2008), “Mode Choice Model for Motorized Trips for Students - A Case Study of Ahmedabad City” TPMDC 08, IIT Bombay.

11. www.gidb.org last accessed on 30th Dec., 2008.

12. Saxena, S.C.(1989), “Traffic Planning and Design”, Dhanpat Rai Publication (P) Ltd., new Delhi.

13. Ortúzar, J. and Willumsen, L.G., “Modelling Transport”, Third Edsition, Wiley Publication.

14. Flood, I., and Kartam, n. (1994a), ‘‘neural networks in Civil Engineering. I: Principles and Understanding.’’ J. Comput. Civ. Eng., 8 (2), pp. 131–148.

The views expressed in the paper are personal views of the Authors. For any query, the authors may be contacted at:E-mail:[email protected], [email protected]


diSaGGReGated modelinG of mode ChoiCe by ann - a CaSe Study of ahmedabad City in GujaRat State


1 INTroduCTIoN

India is a country where a large population lives in villages with their livelihood mainly depending upon agriculture. Further because of stringent environmental rules, industrial growth is shifting towards villages. Both of these activities require a better means of communication which can be provided by good conditioned roads. Most of the village roads have very low volume of traffic, consisting mostly of rural transport vehicles, like agricultural tractors/trailers, light goods vehicles, buses, animal drawn vehicles, motorized two-wheelers and cycles. Some of the village roads may also have light and medium trucks carrying sugarcane, timber, quarry materials, etc. The percentage of village roads is much higher compared to other category roads like nH, SH, MDR and ODR. Therefore, village connectivity assumes not only greater significance in the development of the country but a challenging task also. As of now flexible pavements are in use for village connectivity program because of low initial cost of construction. But due to high cost of maintenance, sensitivity to water logging and lack of institutional set up for their maintenance village roads deteriorate very fast, especially in alluvial regions. Every year several kilometers of village roads are washed away by floods and water logging. Moreover, the nature of traffic is

Paper No. 587 sTudY of ComPosITe effeCT of CoNCreTe Base IN rIgId

PaVemeNT for VIllage roads IN alluVIal regIoNR.K. SRivaStava*, K.K. ShuKla** and S.K. duGGal***

aBsTraCT

A composite rigid pavement removing the separation layer between lean concrete and pavement quality concrete is proposed for village roads. Grade of concrete considered in the present work is up to M20. Composite effect of lean concrete (LC) and pavement quality concrete (PQC) has been investigated. The proposed rigid pavement with the proposed grade of concrete comes out to be economical and safe even for soils having low value of modulus of sub-grade reaction in alluvial regions.

also changing due to industrial growth in nearby areas. Thus, for village roads there is a need to think about the option of rigid pavement as a substitute of flexible pavement.

Rigid pavement is an alternative to flexible pavement where the soil strength is poor, aggregates are costly and the drainage conditions are bad. However, they demand a high degree of professional expertise at the design stage and construction besides high initial cost. Prasad1 carried out life cycle cost analysis comparison between rigid and flexible pavements and concluded that cost difference is negligible considering the cost of maintenance and vehicle operating cost. Further, rigid pavement is a better option from climatic and environmental considerations. Also, cement concrete pavement is the best option for locations having cement and fly ash in close proximity and sub-grade soils having low CBR values. Kadiyali and Dandvate2 made a comparative study of economics of rigid and flexible pavements and observed that rigid pavement is far more economical than flexible one based on overall economic considerations. This generalization is valid for all zones of the country and is independent of sub-grade characteristics3,4. For low traffic volume roads, i.e. village roads and streets, a rural road manual has been introduced by IRC where cement concrete roads are preferred in populated areas/streets to meet the

* Chief Engineer, Hq.1, U.P. P.W.D. Lucknow, E-mail: [email protected]** Professor, Applied Mechanics Department *** Professor,Civil Engineering Department

Written comments on this Paper are invited and will be received upto 15th May, 2013 } MnnIT Allahabad

SRivaStava, ShuKla and duGGal on


14

problems of maintenance due to poor drainage etc. As most of northern parts of India belong to alluvial region having soft soil and poor drainage conditions, lot of expenditure is being incurred every year to maintain the flexible pavements in their congenial condition and this necessitates the use of cement concrete road.

IRC:SP:62-20045 provides guidelines regarding design and construction of cement concrete pavement for rural roads. Minimum grade of concrete specified for rigid pavement is M 30. Such a high grade of concrete is not easy to achieve in villages and remote areas because of the requirement of fully modernized mode of construction. The grade of concrete therefore needs reconsideration. IRC:SP:62-2004 specifies M 30 grade of concrete and a separation layer of 125 micron thick polythene sheet between lean concrete (LC) as a base and pavement quality concrete (PQC) as wearing surface to reduce the friction without taking structural advantage of LC layer. Composite effect of LC and PQC needs to be investigated by removing the separation layer.

In the present work an attempt is made to consider the combined effect of LC and PQC by removing the separation layer between LC and PQC. Minimum grade of concrete proposed herein is M 20 in place of M 30 as specified by IRC. Cost comparison between composite rigid pavement and plain concrete pavement is made and it is found that cost reduces approximately by 20%.

2 desIgN of ComPosITe rIgId PaVemeNT

A composite rigid pavement without separation layer between LC and PQC is designed for the village roads. Design load is taken 30 kn single wheel load as it serves isolated roads where traffic consists of agricultural tractors/trailers, light commercial vehicles, motorcycles buses etc. The fatigue damage is not considered for these roads as percentage and frequency of heavy vehicles are almost negligible. The tyre pressure for village link roads does not exceed 0.50 n/mm2. The width of the roads is taken as 3.0 m. For through roads design single wheel load of 51 kn, width 3.75 m and

tyre pressure 0.7 n/mm2 is considered.

Total stresses induced in the pavements at edges, interior and corners are considered. The critical condition occurs when the wheel load is placed at the edges. Maximum variation in the temperature takes place during day time between 12 to 4 pm. Thus the critical thermal condition occurs during this period. During this period the chances of the vehicles having single axle load of 30 kn and 51 kn passing through village roads are rare. A maximum stress due to temperature variation and wheel load occurring simultaneously is almost not possible. However, stresses are computed for the critical condition, assuming that such situation may arise.

If pavement slab is laid over LC layer without separation layer and assumed bonded with the base concrete, a reduction in flexural stress in pavement is possible which ultimately will reduce the thickness of the pavement slab. Equivalent PQC thickness of higher modulus corresponding to thickness of LC can be calculated using the relationship (Kumar et al.6):

he = (ELC/EPQC)1/3 hLC ...1where,

ELC = Modulus of Elasticity of LC

EPQC = Modulus of Elasticity of PQC

hLC = Thickness of LCModulus of Elasticity of concrete is given by:

E = 5000 √fck (n/mm2)

where,

fck is the characteristic strength of concrete in n/mm2

Thickness of composite rigid pavement and thickness of PQC laid M-10 concrete.

The design of composite rigid pavement without separation layer between LC as base and PQC is carried out. Design parameters considered are:

Tyre pressure = 0.50 n/mm2 for 30 kn single wheel load

= 0.70 n/mm2 for


Study of ComPoSite effeCt of ConCRete baSe in RiGid Pavement foR villaGe RoadS in alluvial ReGion 15

51 kn single wheel load

Modulus of Elasticity for PQC (M 20 Grade Concrete)

EPQC= 22,360 N/mm2

Modulus of Elasticity for LC (M 10 Grade Concrete)

ELC= 15,800 n/mm2

Poisson’s ratio = 0.15

Maximum joint spacing (L) = 4.5 m

Design life = 20 years

Coefficient of thermal expansion = 10.0*10-6/0C

Thickness of PQC, hPQC = 100 mm for 30 kn single wheel load

= 150 mm for 51 kn single wheel load

Thickness of LC, hLC = 100 mm

Equivalent thickness of PQC

he= 89 mm

In the present work equivalent thickness of PQC corresponding to LC layer is taken as 80 mm.

Thickness of composite pavement LC+PQC = 80+100 = 180 mm. for pavement width 3.0 m,

Thickness of composite pavement LC+PQC = 80+150 = 230 mm. for pavement width 3.75 m,

Temperature variation = 12.86 0C and 13.820C

for 180 mm and 230 pavement thickness (Zone-I), respectively = 16.08 0C and 16.820C for 180 mm. and 230 mm.` pavement thickness (Zone-II), respectively.

The design parameters based on CBR values are shown

in Table 1. The stresses in the composite rigid pavement due to wheel load and temperature variation across pavement thickness are calculated at the edge, corner and interior of the pavement and shown in Tables 2 to 9. Stress due to temperature is also calculated at 70% of the temperature variation across the thickness, to account for non-linearity of the temperature variation across the thickness. This reduces the tensile stresses, resulting in further economy. The total stress obtained for the composite rigid pavement is found to be less than the permissible value. The cross-sectional details of the composite pavement are shown in Figs. 1 to 4. Tables 10 and 11 show the kilometer wise cost comparison between Plain Cement Concrete with separation layer and composite rigid pavement without separation layer for single wheel load of 30 kn and 51 kn, respectively. It has been observed that there is saving of more than 20% when composite effect is considered without separation layer.

s.No.

Width of Pavement

(m)

modulus of sub-grade reaction k

(kg/cm2/cm)

single axle load(kN)

Thickness of PQC

(cm)

Thickness of Base layer(cm)

Permissible stress

(N/mm2)

1. 3.0 4.2/2.1 30 10.0 10.0 3.75

2. 3.75 4.2/2.1 51 15.0 10.0 3.75

Table 1 design Parameters Based on CBr Values

Table 2 stresses at edge for Composite rigid Pavement with 10 cm lC (axle load: 60 kN)

Zone-Is.

No.%

CBr modulus of sub-grade reaction, k(kg/cm2/cm)below lC

stress(N/mm2)

Total stress(N/mm2)

Temperature t=12.860c

load Temperature (t 0c)

t 0.7t t 0.7t

1. 2.0 2.1 1.35 0.95 2.17 3.52 3.12

2. 5.0 4.2 1.708 1.19 2.01 3.71 3.200



16

Table 4 stresses at Corner for Composite rigid Pavement with 10cm lC (axle load: 60 kN) Zone-I

s.No.

%CBr

modulus of sub-grade reaction, k (kg/cm2/cm)

below lC

stress (N/mm2) Total stress (N/mm2)

Temperature t=12.860c load Temperature (t 0c)

t 0.7t t 0.7t

1. 2.0 2.1 0.30 0.21 2.15 2.45 2.36

2. 5.0 4.2 0.33 0.22 2.04 2.37 2.26

Table 5 stresses at edge for Composite rigid Pavement with 10cm lC (axle load: 102 kN) Zone-I

s. No. %CBr

modulus of sub-grade reaction, k

(kg/cm2/cm) below lC

stress(N/mm2)

Total stress(N/mm2)

Temperature t=13.82 0c load Temperature (t 0c)

t 0.7t t 0.7t

1. 2.0 2.1 0.93 0.65 2.36 3.29 3.01

2. 5.0 4.2 1.40 0.98 2.19 3.59 3.17

Table 6 stresses at Interior for Composite rigid Pavement with 10cm lC (axle load: 102 kN) Zone-I

s. No. %CBr


below lC


Temperature t=13.82 0cload

Temperature (t 0c)

t 0.7t t 0.7t

1. 2.0 2.1 1.06 0.74 1.4 2.46 2.14

2. 5.0 4.2 1.58 1.11 1.30 2.88 2.41

Table 3 stresses at Interior for Composite rigid Pavement with 10 cm lC (axle load: 60 kN) Zone-I

s. No.

% CBr


below lC


Temperature t=12.860c load Temperature (t0c)

t 0.7t t 0.7t

1. 2.0 2.1 1.45 1.01 1.318 2.760 2.32

2. 5.0 4.2 1.89 1.32 1.22 3.11 2.54



Table 7 stresses at Corner for Composite rigid Pavement with 10cm lC (axle load: 102 kN) Zone-I

s. No. %CBr

modulus of sub-grade reaction, k(kg/cm2/cm)below lC

stress(N/mm2)

Total stress(N/mm2)

Temperature t=13.82 0cload

Temperature (t 0c)

t 0.7t t 0.7t

1. 2.0 2.1 0.60 0.43 2.15 2.75 2.58

2. 5.0 4.2 0.66 0.46 2.04 2.70 2.50

Table 8 Critical stresses at different locations in Composite rigid Pavement with 10 cm lC (axle load: 60 kN, CBr = 5) Zone-I

s. No.

location modulus of sub-grade reaction, k

(kg/cm2/cm) below lC

stress(N/mm2)

Total stress(N/mm2)

Temperature (0.7t) load

1. Edge 4.2 1.19 2.01 3.20

2. Interior 4.2 1.32 1.22 2.54

3. Corner 4.2 0.22 2.04 2.26

Table 9 Critical stresses at different locations in Composite rigid Pavement on 10 cm lC(axle load: 102 kN, CBr = 5) Zone-I

s. No.

location modulus of sub-gradereaction, k(kg/cm2/cm) below lC

stress(N/mm2)

Total stress(N/mm2)

Temperature (0.7t) load

1. Edge 4.2 0.98 2.19 3.17

2. Interior 4.2 1.11 1.30 2.41

3. Corner 4.2 0.46 2.04 2.50

Fig. 1 Cross Section of Composite Rigid Pavement for Dead End Village Link Road.



18

Fig. 3 Cross Section of Rigid Pavement for Through Village Road with DLC

Fig. 4 Cross Section of Rigid Pavement for Dead End Village Road with DLC

Fig. 2 Cross Section of Composite Rigid Pavement for Through Village Road



Table 10 Per km. Cost Comparison between PCP and Composite rigid Pavement for dead end Village link road (with single Wheel load of 30 kN)

s. No.

Plain Concrete Pavement Composite Cement Concrete Pavement

Item measurement Qty. rate (rs.)

amount measurement Qty. rate (rs.)

amount

1. M 30 Grade Cement Concrete

1×1000×3.0×0.15 450 m3 4913 per m3

2210850.00

2. number of Joints

1000

4.5

223 No. 3000 per Joint

669000.00 1000

4.5


669000.00

3. M 20 Cement Concrete

- 1×1000×3.0×0.10 300 m3 4555 per m3

1366500.00

4. LC of Grade M 10

1×1000×3.0×0.10 300 m3 3744 per m3

1123200.00 1123200.00

5. Polythene 1×1000×3.0 3000 m2 5 per m2 15000.00Total: 4018050.00 3158700.00

Saving = 21.39%

Table 11 Per km. Cost Comparison between PCP and Composite rigid Pavement for through Village road (with single Wheel load of 51 kN)

s. No.

Plain Concrete Pavement Composite Cement Concrete Pavement

Item measurement Qty. rate (rs.)

amount measurement Qty. rate (rs.)

amount

1. M 30 Grade Cement Concrete

1x1000x3.75x0.20 750 m3 4913 per m3

3684750.00

2. number of Joints

1000

4.5


892000.00 1000

4.5


892000.00

3. M 20 Cement Concrete

1x1000x3.75x0.15 562.5 4555 2562187.50

4. LC of Grade

M 10

1x1000x3.75x0.10 375 m3 3744 per m3

1404000.00 1x1000x3.75x0.10 375 m3 3744 per m3

1404000.00

5. Polythene 1x1000x3.75 3750 m2 5per m2 18750.00Total: 5999500.00 4858187.50

Saving = 19.02%


20

dead end and through village roads, respectively. It can be seen that induced stresses in the pavement are almost same for k values beyond 6. Total stress in the composite pavement on sub-grade having k value as low as 2 and that even for 100 mm thick pavement is less than the permissible value. Thus, utilizing the composite effect the rigid pavement will be economical.

The views expressed in the paper are personal views of the Authors. For any query, the author may be contacted at: E-mail: [email protected]


Study of ComPoSite effeCt of ConCRete baSe in RiGid Pavement foR villaGe RoadS in alluvial ReGion

Fig. 5 Design Curve for Composite Rigid Pavement for Dead End Village Link Roads

3 desIgN CurVes for ComPosITe rIgId PaVemeNT

The stresses induced in composite rigid pavement, taking into account the effect of base concrete, which is of lower grade, than that of concrete pavement are calculated for different values of sub-grade modulii and pavement thicknesses. The design chart showing the variation of the stresses with pavement thickness for different k values are shown in Figs. 5 and 6 for

Fig. 6 Design Curve for Composite Rigid Pavement for Through Village Roads

4 CoNCludINg remarKs

The design of composite rigid pavement without separation layer between LC and PQC is carried out. It is observed that the advantage of composite rigid pavement is appreciable. LC layer below concrete slab increases the strength of pavement and consequently thickness of slab can be reduced. The minimum grade of concrete used can be reduced to M 20 in place of M 30. It is found that the composite design is safe, even for the smallest value of modulus of sub-grade reaction (k = 2.1 kg/cm2/cm) specified by IRC SP 62: 2004. The concept of composite effect of LC and PQC may be very useful in alluvial regions having poor soil strength. It has been found that composite rigid pavement is economical by 21.39% and 19% than PCP for dead end road and through village road, respectively.

5 refereNCes1 Prasad, B. (2007), “Life Cycle Cost Analysis

of Cement Concrete Roads vs. Bituminous Roads”. Indian Highways, Sept. 2007, pp. 19-28.

2 Kadiyali, L.R. and Dandavate, M.G. (1984), “A Comparative Study of the Economics of Rigid and Flexible Pavements”, The Indian Concrete Journal, Vol. 58, no. 11, 1984.

3 Taunk, G.S. (1998), “Rigid Pavements Vs Flexible Pavements”, Indian Highways, Feb.1998, pp. 5-11.

4 Roy, S., Suresh, R., Reddy, K.S. and Pandey, B.B. (2009), “Flexible-Rigid Pavement with Different Materials- A Sustainable Solution for Village Roads”, Journal of Indian Road Congress, Oct.-Dec.2009, pp. 261-273.

5 IRC:SP:62-2004 (2004), “Guidelines for the Design and Construction of Cement Concrete Pavements for Rural Roads”, The Indian Road Congress, 2004.

6. Kumar S. Santosh, Srinivas, T., Suresh, K. and Pandey, B.B. (2006), “Mechanistic Design of Concrete Pavement”, Journal of Indian Road Congress, 67-3, pp. 209-224.


1 IntroductIon

Flexible pavements with bituminous surfacing are widely used in India for construction of roads and runways. The increased volume of traffic, overloading of axles in excess of permissible limits[1] and higher tyre pressure, have caused widespread problems with the performance of these pavements[2]. The statistics of various performance studies indicate that useful life of bituminous surfacing has declined from average value of 6-8 years in past to about 4-6 years in recent years. It is well known that under the prevailing heavy traffic, overloading and extreme environmental conditions, conventional bituminous overlay, in general, are not meeting the durability requirement. The accelerated deterioration of bituminous overlay burdens the maintenance budget, which in turn affects the availability of funds for new developments. It is a global view[3] that the quality and longevity of pavements, must, be ensured in order to reduce cost of maintenance.

Paper no. 588

Full Scale FIeld PerFormance Study on SBS modIFIed and conventIonal BItumen In BItumInouS concrete

SurFace SuBjected to Heavy traFFIcP. K. Jain*

aBStract

In this paper findings of long term full scale comparative performance of SBS modified and conventional bituminous mixes under overloading conditions with high pavement temperature are reported. The laboratory results show that the performance of SBS modified bitumen is superior to conventional 60/70 bitumen. The resistance to rutting, and moisture sensitivity of bituminous concrete with PMB-40 (SBS modified) is observed better than conventional 60/70 (VG-30) bitumen. The values of stiffness modulus of bituminous mixes with PMB-40 (SBS modified) are observed higher than conventional 60/70 bitumen. Paper also deals with structural evaluation (By Deflection Test) and functional evaluation (By Roughness Test) of the selected road sections with SBS modified and conventional bitumen in Bituminous Concrete (BC) wearing coat, periodically for 60 months at an interval of about six months. The study includes the assessment of the performance of the test sections based upon the time series pavement performance data (Deflection, Roughness and Distresses).The progression of roughness in SBS modified surface is found less compared to surface laid with conventional 60/70 bitumen. The deflection of pavement is also marginally less in case of surface laid with SBS modified bitumen. The rut depth of sections is also observed less than 8 mm in case of SBS modified bitumen as compared to 10-12 mm in 60/70 bitumen sections, supporting laboratory test data of rut depth studies done using wheel tracking machine. The results indicated delayed pavement deterioration, besides higher service life of wearing course, when SBS modified bitumen is used in 40 mm thick BC surface on a portion of National Highway. The estimated extension in life is 50-75%.

* Chief Scientist (Head, Flexible Pavement) and Coordinator (A cSIR), CSIR-Central Road Research Institute, New Delhi – 110 025 E-mail: [email protected]

Written comments on this Paper are invited and will be received upto 15th May, 2013

Conventional/unmodified bituminous binders[4] such as VG-10 (80/100), VG-20 (60/70) or VG-30 (50/60) grade, in general perform well in many situations on majority of the roads. However, in a given specific location/situation, performance of these bituminous binders falls below the acceptable level, such as on roads subjected to heavy traffic loads and volumes as well as due to the ever increasing expectations from the road users, in terms of improved performance by way of better rideability and comfort level. The higher volume of commercial vehicles (trucks) as well as the overloading of axles, especially at road sites experiencing extreme climate such as cold as well as hot climatic condition causes higher stresses onto the pavement, eventually resulting into the development of pre-mature distress[2] (fracture or deformation). To meet such growing demands and challenges, highway engineers have the option to select and use high performance bituminous binders from a wide range of modified binders, made with different types of modifiers (polymer modification). The use of modified

jain on


22

bituminous binders[3] offer a good solution for such situations and assists in (i) reducing the frequency of maintenance required at particular locations, and (ii) providing a much longer service life of the maintenance treatments applied[5].

The degree of improvement in the pavement performance and type of modification required[6] varies, which eventually depends upon the needs of a specific site with respect to the traffic volume, axle loading and pavement temperatures. To prevent deterioration process of flexible pavement under overloading and extreme temperature conditions, several types of measures may be adopted effectively such as improved design, use of high performance materials and use of effective construction technologies[7]. Adequate findings for specific site conditions in India on performance of different types of modified bitumens are not available to profession to take scientific decision to choose types of modification. Therefore, a study was undertaken to monitor full scale periodic performance for observation of pavement deterioration trends, using elastomers (SBS) modified bitumen.

2 lITeraTure surVeY

Despite the large number of polymer products, there are relatively few types, which are suitable for bitumen modification and are incorporated in the specifications [8-9]. To achieve the goal of improving bitumen properties, a selected polymer or blend of polymers also create a secondary network or new balance system with bitumen as binder is needed. The degree of modification depends on the properties of the polymer, polymer content and nature of the bitumen. Vanbeem and Brassier[10] reported findings of study on bituminous binders of improved quality containing SBS thermoplastic rubber. Subsequently, a number of laboratory studies[11-30] were conducted on modification of bitumen using SBS block copolymer. Isaacson and Lu[11] investigated properties of modified binders and showed that elastomeric binders increase both rut resistance and fatigue life of bituminous mixes. Jain and Coworkers [12-15]

conducted extensive laboratory studies to investigate laboratory performance of SBS modified bitumen. Audery etal[16] investigated the influence of polymer modification, moisture conditioning and long term aging on bond strength of binders was measured by means of modified pull off test. Recently, Somna and Coworkers[17] investigated efficacy of modified bitumen in terms of suitability of various commercially available modified binders. Shivani and Veeragavan[18] investigated fatigue behavior of (SBS) modified bituminous concrete mixture. An increase of 2 to 2.5 times in value of resilient modulus is also reported. The fatigue life of SBS modified mix was observed 2.1 to 2.4 times compared to 60/70 bitumen. Bouldin and Collins[19] investigated effect of rheology on rutting resistance of SBS modified bitumen. The findings suggest a need for different calibration factor in PMB mixes due to enhanced performance for use in rutting and fatigue cracking prediction equations. Srivastava etal[20] investigated implication of materials characteristics of SBS modified bitumen on thickness of overlays. Jain and Coworkers[15] investigated relationship between rheological properties of SBS modified binders and mechanical properties of their mixes. Polymer modified bitumen especially those prepared with elastomers are commonly used in US for flexible pavements carrying high volume of traffic. Von Quintus and Coworkers [21] conducted extensive study on SBS modified bitumen, and reported 50-100 percent extension in service life further supported by mechanistic – empirical distress prediction model, which confirmed findings of studies done by CRRI[12-15]. A number of laboratory studies have been conducted on elastomeric modification and beneficiation accrued[22-33]. Studies for specific site conditions such as overloading and high temperature are to select type of modification felt essential. This paper deals with findings of full scale performance study on SBS modified bitumen in bituminous concrete conforming to Indian standards[8-9].

3 eXPerImeNTal

Experimental work of the study was carried out in two phases viz laboratory investigations and field studies.


full SCale field PeRfoRmanCe Study on SbS modified and Conventional bitumen in bituminouS ConCRete SuRfaCe SubjeCted to heavy tRaffiC 23

The description of experimental work is given as under:

laboratory Investigations

Materials: PMB-40 conforming to IS: 15462[8-9] and 60/70 bitumen conforming[4] to IS: 73-1992 were used in this study. The properties of PMB-40

and 60/70 grade bitumen are given in Table 1 and 2. Rheological properties[15] of PMB-40 and 60/70 penetration grade bitumen are given in Table 3. The properties of aggregates and grading of aggregates used for preparation of mixes are presented in Table 4 and 5. The rheological properties of bitumen and modified bitumen were investigated as reported earlier[15].

Table 1 Properties of SBS Modified PMB - 40

Properties PmB-40-e Test methodValue limit

Penetration at 25°C, 100 g, 5 sec., 0.1 mm 33 30-50 IS:1203Softening point, (R&B), °C 64 60 (min) IS:1205Elastic recovery of half thread in ductilometer at 15°C, % 76 75 (min) IS:15462Separation, difference in softening point, R&B, °C 2 3 (max) IS:15462Viscosity at 150°C, Poise 7.7 3-9 IS:1206

Test on residue of Thin film oven TestLoss in weight, % 0.1 1.0 (max) IS:9382Increase in softening point, °C 2 5 (max) IS:1205Reduction in penetration of residue, at 25°C, % 21 35 (max) IS:1203Elastic recovery of half thread in ductilometer at 25°C, % 51 50 (min) IS: 15462

*PMB - 40 (SBS modified bitumen)

Table 2 Properties of 60/70 Penetration grade Bitumen

designation Test Values

limits as per Is: 73 Test method

Penetration at 25°C, 0.1 mm, 100 gm, 5 sec 66 60-70 IS: 1203Softening point, (R and B), °C 46 Min. 45 IS: 1205Ductility at 27°C, cm 75 Min. 75 IS: 1208Viscosity @ 60°C in Poise 2600 Min. 2400 IS: 1206Viscosity at 135°C, cSt 310 Min. 300 IS: 1206

Table 3 rheological Properties of PmB-40 and 60/70 Penetration grade Bitumen[15]

Binder Type g* at 60°C, kPa Sin δ, at 60°C G* Sin δ at 60°C, kPa

G*/ Sin δ at 60°C, kPa

Temperature (°C) for 1.0 kPa value

of G*/Sin δPMB-40 (E) 6859 0.981 6735 6.98 7760/70 (M)* 1920 0.996 1921 1.92 64

*60/70 grade bitumen from Mathura Refinery

jain on


24

Table 4 Properties of aggregates (Quartzite)

Properties Test Value morTh limits method

Impact Value, % 18 Max 30 IS:2386 (P-4)

Water absorption, % 0.9 Max 2 IS: 2386 (P-6)

Stripping, % 5.0 Max 5 IS: 6241

Combined Flakiness and Elongation Indices,

29 Max 30 IS: 2386 (P-1)

Table 5 Grading of Aggregates in Bituminous Concrete (MoRTH Specification Clause 509)

Is sieve (mm) grading, % passing morTh limits (gr. II)

19.0 100 100

13.2 91 79-100

9.5 79 70-88

4.75 61 53-71

2.36 49 42-58

1.18 40 34-48

0.600 32 26-38

0.300 33 18-28

0.150 16 12-20

0.075 7 4-10

Binder Content, % 5.2 5-7

Preparation of bituminous mixes: The binder was heated to produce kinematic viscosity of 170 cSt and 280 cSt for determination of the laboratory mixing and compaction temperature. Mixing temperature can be taken as the temperature that produces a uniform and sufficient coating on coarse aggregates. Mixing temperatures of 180°C and a compaction temperature of 160°C were selected for SBS modified bitumen mix. These mixes were designed by Marshall method as reported earlier[34].

methodology for Testing

The prepared specimens were subjected to determination

of performance properties’ through established test methods. The details of tests are given below.

retained stability

Retained Stability is the measure of moisture induced striping in the mix and subsequent loss of stability due to weakened bond between aggregate and binder. The test was conducted using the normal Marshall samples. Samples placed in water bath at 60ºC for half an hour as well as for 24 hour were used and their stability was determined. This test is conducted to know whether the mix is greatly susceptible to moisture damage or not.



The minimum value of Retained Stability of bituminous mixes is 75%.

Indirect Tensile strength (ITs)

This test method measures the splitting tensile strength by the application of a diametric compressive force on both unconditioned (dry) and conditioned (wet) cylindrical bituminous mix specimens placed with its axis horizontal between the plates of a compressive testing machine. Tensile strength ratio is determined according to AASHTO T283, which is the ratio of wet tensile strength to the dry tensile strength of Marshall Specimens. The test was conducted at 25°C temperature on the samples conditioned for 24 h at 60°C and the load at which the specimen fails is taken as failure load of the bituminous mixture.

Indirect tensile strength of the specimen is calculated as follows:

Where,

T = Indirect tensile strength in kg/sq.cm

P = Load at which failure of sample occurred in kg

t = Thickness of sample in cm

d = Diameter of sample in cm

The tensile strength ratio (TSR) is calculated as follows:

Where,

T1= Average Tensile strength of unconditioned specimen

T2= Average Tensile strength of conditioned specimen

Wheel Tracking Test

Rutting is caused by the permanent deformation of pavement under wheel path. The susceptibility of bituminous mixtures to permanent deformation is measured by Wheel Tracking Device (WTD). The WTD is destructive test and it involves direct contact between the loaded wheel and the rectangular test specimens. The test was conducted on the prepared slab specimen of 300X300X50 mm at optimum binder content containing fly ash and stone dust. The test was conducted as per BS: 598-1998. The total numbers of 20,000 passes were applied at 45°C and resulting rut depth was measured.

resilient modulus Test

Resilient Modulus is an important parameter to determine the performance of pavement, to analyze the pavement response to repeated traffic loading. The test was done by measuring the indirect tensile strength in repeated loading using Universal Testing Machine consisting of Control and Data Acquisition System (CDAS), personal computer and related integrated software. The test follows the ASTM Designation D 4123-82. Specimens at their optimum bitumen content were prepared and loaded by diametrical force in pulse loading. Test parameters were ; condition pulse count 5, condition pulse period 3000 ms, test pulse period 2000 ms, rise time 50 ms, peak loading force 1000 n and poisons ratio 0.35. Resilient modulus tests were conducted on all samples to evaluate mixture ‘temperature susceptibility’ and for use as a reference to earlier testing. Though it was once believed that stiffer pavements had greater resistance to permanent deformation, it has been concluded that resilient modulus at low temperatures is somewhat related to cracking, as stiffer mixes (higher MR) at low temperatures tend to crack earlier than softer mixtures.

Properties of designed bituminous concrete mixes are given in Table 6, 7 and 8. The summary of data analysis is given in Table 9.

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Table 6 Properties of designed Bituminous Concrete mixes

Binder Type stability, kg, 60°C

flow, mm, 60°C

marshall Quotient

kg/m

retained stability, Kg. 24 hrs, 60°C

retained stability %,

60°C

retained ITs, %

PMB-40 (E) 1560 3.6 433 1451 93 86

60/70 1203 3.2 376 1058 88 82

Table 7 Properties of designed Bituminous Concrete mixes

Binder Type Indirect Tensile strength, kg/m2

25°C

Indirect Tensile strength, retained

%

stiffness modulus, at 35°C, mPa

rut depth, mm,at 45°C

PMB-40 (E) 10.6 86 2070 6.2

60/70 (M) 8.4 82 1597 12.1

Table 8 results of resilient modulus for BC mixes

Binder Type resilient modulus, mPa

25°C 35°C 45°C

PMB – 40 (E) 5218 2070 952

PMB 60/70 3828 1597 682

Table 9 summary of findings from data analysis

Binder Type rut depth, mm fail temperature°C by dsr

PMB- 40 (E) 6 76

PMB-60/70 12 64

field Investigations

Construction of test sections: Construction of experimental sections was done as per guidelines laid down in MoRTH specifications[36]. The particulars of

test sections are given in Table 10. These test sections were constructed during December 2005-Macrh 2006 after conducting pavement evaluation and needed strengthening.

Table 10 Particulars of Test sections at Nh-1 (outer ring road)

Test section Number Carriageway Chainage (km) Binder Type

1A Delhi-Karnal (LHS) 9.750-9.950 Modified (SBS)

2A Delhi-Karnal(LHS) 10.000-10.200 Modified (SBS)



3A Delhi-Karnal(LHS) 11.500-11.700 neat(60/70)

4A Delhi-Karnal(LHS) 13.000-13.200 neat(60/70)

5A Delhi-Karnal(LHS) 14.400-14.600 Modified(SBS)

6A Delhi-Karnal(LHS) 15.000-15.200 Modified (SBS)

1B Karnal-Delhi(RHS) 9.750-9.950 Modified(SBS)


3B Karnal-Delhi(RHS) 11.500-11.700 neat (60/70)

4B Karnal-Delhi(RHS) 13.000-13.200 neat (60/70)

5B Karnal-Delhi(RHS) 14.400-14.600 Modified (SBS)


Performance observation: The experimental sections constructed, as indicated in Table 10, were monitored periodically after every six months for a period of five years (2006 to 2011) for their performance. The key parameters related to performance, measured on the test sections periodically, are described below:

I Traffic and Axle Load Studies: Performance of surfacing is always influenced by traffic intensity as well as loading of vehicles plying on the road. Hence, the traffic survey is very vital to study performance of roads and thus the survey was conducted at one location. The survey was conducted for 48 hours round the clock by engaging skilled enumerators, separately for up and down carriageway covering all types of commercial vehicles thrice during the study. The information on actual damaging effects of the commercial vehicles

Fig. 1 MSA Progression with passage of time

plying on the road is necessary to evaluate the actual quantum of traffic stresses in the form of MSA as per IRC: 37-2001. VDF was estimated on the basis of the earlier studies[36]. The tyre pressure of vehicles was in the range of 5.6 to 6.6 kg/cm2. Progression of MSA with passage of time is illustrated in Fig.1.

II measurement of Pavement surface distress: Surface distress is the physical manifestation of internal damage within a pavement structure and is developed on the pavement surface with passage of time due to a variety of influencing factors such as traffic and climate. The pavement surface distress is one of the important indicator of the pavement’s functional as well as structural condition and eventually the performance of specifications/treatments. Surface distress was measured to find out their type, extent and severity. For taking measurements and recording data of different types of distress, each test section was divided into subsections of 50 m each with clearly marking the start and end points. The each subsection was further divided into two equal longitudinal strips (left and right). The different type of distresses (cracking, pothole, raveling, shoving, settlement/depression, bleeding and patchwork) were marked and carefully measured and recorded separately. In case of

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longitudinal and transverse cracks, the affected area is taken as the product of actual length of crack and 0.3 m width of strip. Progressions of surface distresses with passage of time are plotted in Figs. 2 to 5. The data of Pavement Condition Rating (PCR) on 100 point scale (Annexure A & B) for all the test sections, at the interval of 6 months for 10 observations were collected and plots are given in Figs. 4 and 5.

III roughness measurements: Serviceability in terms of road user’s comfort and vehicle operation cost are directly influenced by the roughness offered by a pavement surface. The roughness measurements on the test sections were taken at two wheel paths viz. left, and right with a calibrated towed Fifth Wheel Bump Integrator. The left and right wheel paths were identified at a distance of 1.5 m from the edges. The vehicle, towing the bump integrator, was run at a constant speed of 32+1 kmph between the ‘start’ and ‘end’ points of each section, on each wheel path for at least three times, to get the consistent value. The tyre pressure of towing vehicle and fifth wheel was maintained at 2.0 kg/cm2

and the oil in dashpot was maintained at the required level. The calibration of BI unit was carried out with Dipstick. For calibration purpose, a number of road sections with a wide range of roughness values were covered to make the exercise meaningful. Sections of 100 m long were selected for the purpose. Wheel path and start/end points of the sections were marked with paint. Progression of roughness with passage of time are plotted is Figs. 6 to 9.

Fig. 2 Progression of distresses with passage of time in LHS carriageway (One performance observation is taken

at the end of 6 months interval)

Fig. 3 Progression of distresses with passage of time in RHS carriageway (One performance observation is taken


Fig. 4 Relationship between performance rating and duration of service (LHS carriageway) (One performance observation is taken


Fig. 5 Relationship between performance and duration (RHS carriageway) (One performance observation

is taken at the end of 6 months interval)

Fig. 6 Relationship between progression of roughness and passage of time (LHS) (One performance observation




IV measurements of Pavements Deflection: Structural condition of test sections has been evaluated by the pavement response in terms of deflection under a standard rear axle load of 8170 kg by a loaded truck, having a tyre pressure of 5.6 kg/cm2. Deflection measurement were taken at 11 points in a 200 m long section, in a staggered manner. The measurements were done as per CGRA procedure, laid down in IRC: 81-1997[24], by taking three consistent readings at each measurement atmospheric and pavement temperatures were also measured and recorded at the start and end of deflection measurements. Necessary corrections for temperature and moisture were applied to get the corrected rebound deflections as per the factors suggested in IRC: 81-1997. Data are plotted in Figs. 10 and 11.

discussion of results

Properties of bituminous mixtures: Data of designed mixes given in Tables 6, 7, 8 and 9 indicate superior properties of SBS modified bituminous mixes as compared to mixes of 60/70 bitumen. It can be seen from the data, values of Marshall Stability are 30

Fig. 7 Relationship between progression of roughness and passage of time (LHS) (One performance observation


Fig. 8 Relationship between progression of roughness and passage of time (RHS) (One performance observation


Fig. 9 Relationship between progress of roughness and passage of time (RHS)

Fig. 10 Change in deflection with passage of time (LHS) (One performance observation is taken at the end of 6 months interval)

Fig. 11 Change in deflection with passage of time (RHS) (One performance observation is taken at the end of 6 months interval)

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percent higher for PMB-40 mix as compared to mix of 60/70 grade bitumen. Similarly, values of Marshall Quotient are also 15% higher for PMB-40 mix over conventional mix. The values of Marshall Quotient (Stability in lbs flow in 0.01 inch units) are observed two times of prevailing tyre pressure of commercial vehicles. The higher value of retained Marshall Stability (>90 percent) and indirect tensile strength (>85), indicate better resistance of PMB mixture to stripping and moisture damage. Improved resistance to cracking using PMB-40 as binder is expected on account of higher value of indirect tensile strength of PMB-40 mixes, which is 26 percent higher than conventional mixes. Resilient modulus is an important parameter, and its values at different temperature are significant from pavement design point of view. The thickness of layers of bituminous mixes depends upon values of resilient modulus at 35°C. The value of resilient modulus is 40% higher for SBS modified bitumen at 45°C. The value of resilient modulus at 35°C is 30% higher over conventional mixture of 60/70 bitumen. The data of rutting given in Table 7 indicate that SBS modified mixes are highly resistance to rutting and deformation at higher temperature. It can be seen from Table 8 that rutting of SBS modified mix after 20,000 cycles is 6 mm as compared to 12 mm in the mix of 60/70 bitumen. Therefore, SBS modified mix is highly resistant to damage of surface due to higher tyre pressure and effects of overloading at higher temperature.

Performance observation of Test sections

Measurements of surface distress and roughness are the basic parameters to evaluate functional condition of a pavement, while the pavement deflection is an indicator

of its structural condition. Development of distress on the pavement surface is a time based progressive mechanism with increasing traffic loads. Failure of bituminous surface as well as the pavement occurs in several modes such as deformation (rutting and formation of pot holes), which eventually contribute to progression of roughness with passage of traffic. The overloading of axle further contributes to faster progression of distress on road surface. The increase in MSA with passage of time is shown in Fig. 1. It can be seen that about 80 MSA traffic is passed on RHS carriageway (Delhi bound) while 50 MSA has been passed in 5 years on LHS (Karnal bound carriageway). Therefore, faster deterioration of surface is expected on Delhi bound carriageway. Data plotted in Figs. 2 and 3 indicate development of more distress on Delhi bound carriageway as compared to Karnal bound carriageway. Further, it can be seen that distress progression (Figs. 2 and 3) is higher for sections of 60/70 grade bitumen compared to SBS modified bitumen. In majority of test sections of unmodified bitumen distress is in the range of 4 to 8 percent. However, distress is in the range of 2 to 4 % at the end of 60th month for SBS modified bitumen. The major distress is in the form of cracking and ravelling. Plots of Pavement Condition Rating (PCR) on 100 point scale (Annexure A and B) are given in Figs. 4 and 5. It can be seen that decrease in PCR is faster in case of unmodified bitumen sections as compared to modified bitumen sections. The decrease in PCR is observed higher on Delhi bound carriageway due to passing of higher number of MSA. The value is above 75 (very good) for modified bitumen sections as compared to 60-74 (good) for unmodified bitumen sections at the end of 5th years of service 10th

observation.

Table 11 Pavement serviceability Index (PsI) Concept

Parameters excellent Very good good fair Poor Very Poor failedPSI 10 8 6 4 3 2 1PCR 90-100 75-89 60-74 50-59 40-49 30-39 <30Cracking, % <1 <3 3-7 8-12 13-20 21-25 >25Total Surface Distress, % <1 <5 5-10 11-15 16-25 26-30 >30

Roughness (mm/km) <1500 1501-2000 2001-2500 2501-3000 3001-3500 3501-4000 >4000

Deflection, mm <0.50 0.50-0.60 0.61-0.75 0.76-1.00 1.00-1.25 1.26-2.00 >2.0



Table 11 indicate Pavement Serviceable Index (PSI) concept adopted for analysis of data. If performance of test sections evaluated on the basis of this concept (Table 11), SBS modified bitumen sections falls in the category of very good with 6-7 PSI (very good) after lapse of 60 months. However, sections with unmodified bitumen fall in the category of 4-5 PSI (fair to good). The PSI of unmodified bitumen is in the range of 6-7 after 30-36 months service. Therefore, 2-3 years extension in service life of bituminous surface is observed using SBS modified bitumen in a bituminous surfacing of flexible pavement subjected to overloading and seven days average highest pavement temperature (64°C). The plot of PSI vs MSA is shown in Fig. 12. A fair to good condition of PSI i.e. 5 may be considered as life of surfacing. In the present case, stage of 5 PSI is observed after passage of 60 msa, for 60/70 bitumen. The stage of 5 PSI is expected after 100 msa in SBS modified bitumen section. Therefore, surface of SBS modified bitumen can take 90% higher loads.

The rate of roughness progression is a vital factor for assessment of performance of a road surfacing. It can be seen from the Figs. 6 to 9 that the roughness level was around 1500 mm/km for all the test sections of modified and unmodified bituminous surfacing when the first observation of the performance study was made. The roughness of modified bitumen sections was slightly higher at the time of first observation. The PSI of modified bitumen sections was in the range of 8 to 9 at the beginning. It is observed from the roughness progression trends (Figs. 6-9) with time that there is only about 25 percent increase in roughness for all the test sections except sections of unmodified surfacing. Majority of test sections of unmodified bituminous surfacing shows higher roughness compared to modified bituminous surfacing. It is clear from the trend that progression of roughness is slow in case of modified test sections as compared to sections of unmodified bituminous surfacing.

It can be seen from the Figs. 10 and 11 that observed rebound pavement deflection were in the range of 0.4-0.5 mm for all the test sections during the first observation of the study, indicating the structurally

sound condition of the pavement after construction of test sections. The thickness of overlay was designed by Benkelman Beam methods before construction of test sections. The values of deflection observed and less for modified bitumen section, which may be attributed to higher values of resilient modulus (Table 9). It has been observed during the study that the pavement deflection values are higher in post monsoon performance observation in comparison to pre-monsoon observation. The pavement deflection of all the test sections increased with respect to increase in traffic and reached in the range of 0.8-1.1 mm at the time of last observation. The values for modified bitumen sections observed in the range of 0.8 to 0.9 mm as compared to 0.9 to 1.1, for unmodified bitumen sections.

Fig. 12 Relationship PSI vs MSA (One performance observation is taken at the end of 6 months interval)

4 CoNClusIoNs

i) Rheological properties of SBS modified bitumen (SHRP parameters) indicate higher pavement fail temperature as compared to conventional 60/70 bitumen. PMB-40 (SBS modified) qualifies as PG-76 grade indicating its suitability for a pavement subjected to highest pavement temperature of 76°C which is maximum temperature in India.

ii) Properties of mixes (strength parameters) like Marshall stability, Marshall Quotient, Indirect tensile strength of SBS modified mixes are higher than conventional bitumen mixes Resistant modulus of SBS modified mixes at different temperatures is 1.25

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to 1.75 times higher compared to 60/70 bitumen.

iii) Rutting of SBS modified mix is half (6.2 mm) as compared to conventional 60/70 grade bitumen mix (12.1 mm).

iv) Progression of roughness and distress is less in case of SBS modified bitumen as compared to 60/70 bitumen.

v) Deflection of SBS modified bitumen pavement is less as compared to conventional bitumen.

vi) Pavement Serviceability Index values of SBS modified bitumen after 5 years and conventional bitumen after 3 years are same, indicating 2-3 years extension in life of surfacing under heavy traffic and high pavement temperature conditions.

acknowledgments

Author is thankful to Dr. S. Gangopadhyaya, Director (Central Road Research Institute) for kind permission to publish this paper. Thanks are due to Sh. Y. V. Rao for help in collection of roughness data.

refereNCes

1. Kandhal, P.S. and Dhir, M.P., “Use of Modified Bituminous Binders in India-Current Imperatives”, Journal of the Indian Roads Congress, Vol., 72-3, (2011), pp 175-189.

2. Sikdar, P.K., Jain, S.S., Bose, Kumar, S., “Premature Cracking of Flexible Pavements” Journal of Indian Roads Congress, Vol. 63-3, (1993), pp. 355-398.

3. Isacsson U. and Lu. X, “Testing and Appraisal of Polymer Modified Road Bitumens”, RILEM Report no. 17(1998), pp. 13-38.

4. IS: 73-1992 “Specification-Paving Bitumen”

5. Goodrich, J. L. “Asphalt and Polymer Modified Asphalt Properties Related to the Performance

of Asphalt Concrete Mixes”, Proceedings of Association of Asphalt Paving Technologies, Vol. 57, (1998) pp. 116.

6. Button, J.W., “Summary of Asphalt Additives Performance at Selected Sites” TRR 1342 (1992), pp. 67-75.

7. Shuler, T.S., Collins, J.H. and Kirkpatrick, J.P., “Polymer Modified Asphalt Properties related to Asphalt Concrete Performance”, ASTM, STP 941, (1987) pp. 179.

8. IS: 15462-2004, “Polymer and Rubber Modified Bitumen – Specification”.

9. IRC: SP-53-2002, “Guidelines on Use of Polymer and Rubber Modified Bitumens in Road Construction”, Indian Roads Congress, new Delhi.

10. Vanbeem, E.J. and Brassier, P., “Bituminous Binders of Improved Quality Containing Cariflex Thermoplastic Rubber” Journal of the Institute of Petroleum, Vol. 59. (1973).

11. Isacsson, U. and Lu, X., “Laboratory Investigation of Polymer Modified Bitumen”, Proceedings of Association of Asphalt Paving Technologists, Vol. 68, (1999) pp. 35.

12. Shukla, R.S. and Jain, P.K., “Improvement of Waxy Bitumen by the Addition of Synthetic Rubbers, Polymers and Resins” , Highway Research Bulletin no. 38, (1984) p. 17.

13. Bose, S. and Jain, P.K., “Laboratory Study on Use of Organic Polymers in Improvement of Bituminous Road Surfacing”, Highway Research Bulletin, Vol. 38, (1989), pp. 63-79.

14. Jain, P.K., Sangita, Bose, S. and Arya, I.R., “Characterization of Polymer Modified Asphalt Binders for Roads and Airfields”, ASTM STP 1108 (1192), pp. 341-355.


Full Scale Field PerFormance Study on SBS modiFied and conventional Bitumen in BituminouS concrete SurFace SuBjected to Heavy traFFic 33

15. Jain, P.K., Sikdar, P.K., Kumar, Shanta and Kamraj C., “Studies on Correlation of Rheology and Performance Characteristics of Mixes of Modified Binder for Roads in High Temperature Areas”, Highway Research Bulletin, Indian Roads Congress No. 3, November (2006).

16. Copeland, Audrey R., Youtcheff, Jack and Shenoy, Aroon, “Moisture Sensitivity of Modified Asphalt Binder – Factors Influencing Bond Strength”, Journal of the Transportation Research Board, No. 1998 (2007) pp. 18-28.

17. Nishal, Somna, Sangita, Sharma B.M. and Sengupta, J. B. “A Laboratory Study on Etticacy of Conventional and Modified Bituminous Binder in Construction of Roads”, Indian Highways, Vol. 40, No 1, (2012), pp. 13-21.

18. Gupta, Shivani and Veeraragavan, Dr. A. “Fatigue Behaviour of Polymer Modified Bituminous Concrete Mixture” Journal of the Indian Roads Congress (2009), Vol. 70-1, pp. 55-64.

19. Boulden, M. G. and Collins J. H., “Influence of Binder Rheology on Rut Resistance of Polymer Modified and Unmodified Hot Mixes”, ASTM STP 1108 (1992), pp. 60-61.

20. Srivastava A., Hopman, Piet C., Molenaar, Andre A. “SBS Polymer Modified Asphalt Binder and its Implications on overlay Design”, ASTM STP 1108 (1992), pp. 309-329.

21. Quintus, Von, Malleha, H.J. and Buncher, M.S. “Quantification of Effect of Polymer Modified Asphalt on Flexible Pavement Performance”, (2007) TRR – 2001.

22. Goodrich, J.K. “Asphalt and Polymer Modified Asphalt Properties Related to the Performance of Asphalt Concrete Mixes. Proceedings Association of Asphalt paving technologists Vol 57 (1998) p. 116.

23. Shuler, T.S., Collins, J.H. and Kirkpatrick, J.P., “ Polymer Modified Asphalt Properties Related to Asphalt Concrete Performance”, ASTM, STP 941, pp. 179, (1987).

24. King, Gayle, King, H., Pavlovich, R.D, Epps, A.L. and Kandhal, P.S., “Additives in Asphalt, Journal of Association of Asphalt Paving Technologies, Vol. 68A (1999).

25. Chen, J.C., Liao, M. and Shiah, M. “Asphalt Modified by Styrene - Butadiene - Styrene Triblock Copolymer Morphology and Model”, J. Material, Civil. Engg., Vol. 14, No. 3, (2002), pp. 224.

26. Maria, C.C.L., Sandra, A.S. and Jorge, B.S., “Characterization and Thermal Behavior of Polymer Modified Asphalt”, Mat. Research Vol. 7, No. 4, (2004), pp. 529.

27. Collins, J.H., Boulain, M.G., Gelles, R. and Barker, A. “Improved Performance of Paving Asphalt by Polymer Modification Proc Asphalt Pav. Tech.”, Vol. 60 (1991) pp. 43-79.

28. “Performance of Modified Bitumen on NH-2”, CSIR-Central Road Research Institute, Technical Report (2000), pp. 1-200.

29. Mehndiratta, H.C., Kumar, Praveen, Borapureddy, A. Durga Prasad, and Singh, K. Lakshman, “Relation step between Rheological and Conventional Properties of Bitumen”, Highway Research Krulleliy.

30. Collins, J.H., Bouldin, M.C., Gelles, R. and Berker, A., “Improved Performance of Paving Asphalt by Polymer Modification”, Proceedings of Association of Asphalt Paving Technologists, Vol. 60, pp. 43 (1991).

31. Palit, S.K., Reddy, K.S. and Pandey, B.B., “Performance Evaluation of Crumb Rubber Modified Asphalt Mixes.” J. Materials, Civil Engg., Vol. 11, No. 6 (2002), pp. 527.

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32. Panda, M. and Mazumdar, M., “Engineering Properties of EVA Modified Bitumen Binder for Paving Mixes”, J. Materials, Civil Engg. Vol. 11, No. 2 (1999), p. 131.

33. Panda, M. and Mazumdar, M., “ Utilization of Reclaimed Polyethylene in Bituminous Paving Mixes”, J. Materials, Civil Engg., Vol. 14, No. 6 (2002), p. 527.

34. Jain, P.K., Kumar, Shanta, Sengupta, J.B., “Mitigation of Rutting in Bituminous Roads by

Use of Waste Polymeric Packaging Materials”, Indian Journal of Engineering & Material Science, No 6, Vol. 18 (2011).

35. Jain, P.K., Rongali, Uma Devi, Chourasiya, Anita and Mittal, Abhishek, “Studies on Performance of Warm Polymer Modified Bituminous Mixes”, Indian Journal of Engineering & Material Science (Communicated).

36. Specifications for Road and Bridge Works (Ministry of Road Transport and Highways) 4th Revision, 2004.

faCTors maXImumPoINTs

PerformaNCe PoINTs aWardedsPeCIfICaTIoNdaTe of laYINgloCaTIoN 0-25 m 25-50 50-75 75-100 100-125 125-150 150-175 175-200surfaCe aPPearaNCeSatisfactoryHighly Dry/Slightly RichDry/RichVery Dry/Very Rich

10753

CraCKINgno CracksFine hair cracksLocal CracksScatteredExtensive

20161284

reVellINgnoneFew SomeExtensive

2015105

annexure a

CeNTral road researCh INsTITuTe

fleXIBle PaVemeNT dIVIsIoN

name of the Road:_____________________________ Carriageway Width (m):____________________

Category of the Road:___________________________ Date of Observation:_____________________

Chainage of Test-Section: Km_________ to Km______________ Weather Condition:_______________________

Type of Wearing Course________________________________ Area of the Section:______________________

The views expressed in the paper are personal views of the Author. For any query, the author may be contacted at: E-mail: [email protected]



PoTholes/PaTChesnoneFew SomeExtensive

40302010

surfaCe uNeVeNNessnoneFewSomeExtensive

10753

ToTal 100remarKsgradingVery good/good/fairfair/Very/Poor

annexure B

CeNTral road researCh INsTITuTe fleXIBle PaVemeNT dIVIsIoN

name of the Road:_____________________________ Carriageway Width (m):____________________

Category of the Road:___________________________ Date of Observation:_____________________

Chainage of Test-Section: Km_________ to Km______________ Weather Condition:_______________________

Type of Wearing Course________________________________ Area of the Section:______________________

Chainage of sub section

CrackingPatch work

Potholesdepression/settlement

ravelling Bledding shovingTotal

distress

Type area % area % area % area % area % area % area % area %

0-25 LeftRight

25-50 LeftRight

50-75 LeftRight

75-100 LeftRight

100-125LeftRight

125-150 LeftRight


36

Checked by-name:__________________ Recorded by name:_____________

Signature:_________________________ Signature:_____________________

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full SCale field PeRfoRmanCe Study on SbS modified and Conventional bitumen in bituminouS ConCRete SuRfaCe SubjeCted to heavy tRaffiC

150-175 LeftRight

175-200 LeftRight

Total

Remarks


1 INTroduCTorY CauTIoNs

- The Arabian Gulf waters are very highly charged with the attacking chlorides, sulphates and moluscs – the tripple killers of structure durability.

- The Sea-link alignment may have to provide for navigation channels.

- Effect of associated dredging and the location and extent of island–embankments on the following may have to be studied :

l the delicate balancing of water and salt exchange across the causeway for zero environmental effect on the life and living of the protected species of Dugongs (marine cows) Turtles, and other marine life

l the unobstructed migration and spawning of shrimps, and

l minimum disturbance to the under-sea fresh water acquifers in certain areas,

These may be only some of the challenges to meet.

- Hence evolving and fixing the various requirements and parameters for these structures call for unstinted clinical attention

for their alignments, location, design and construction in keeping with zero environmental impact.

2 CoNsTraNTs

2.1 heavy Concentration of sulphates and Chlorides:

- The Arabian Gulf is a nearly 1000 km. long rather narrow finger of Arabian Sea, going all the way west to Kuwait.

- Thus, not being an ‘open sea’, this body of water is relatively still and remains relatively unchurned

- These high concentrations of Sulphates & Chlorides badly ATTACK concrete and steel eventually under the prevalent high humidity & Temperature.

2.2 Since moluscs (living marine organisms in these waters) are known to have ‘bored’ (and eaten away) upto 150 mm. deep, 25 mm. dia. holes in limestone aggregates, it is essential to use Gabro aggregates in foundations and substructure upto 2-3 m above splash-level which the Moluscs do not seem to relish.

2.3 Possible damage to subterranean natural Water AQUIFERS (where they exist) in case the ‘deep’ bridge foundations puncture these aquifers.

Paper No. 589

guIdelINes for desIgN & CoNsTruCTIoN of mega CoasTal sea-lINKs IN The araBIaN gulf

& sImIlar surrouNds v.K. Raina*

* Director (Technical) ITnL (IL&FS Group), Professor Emeritus, CoEP, E-mail: [email protected] Written comments on this Paper are invited and will be received upto 15th May, 2013

Raina on


38

2.4 any ‘disturbance’ to ‘free exchange’ of water and salts (across the causeway) owing to obstructions caused by bridge–substructure, by dredging of sea–bed channels, and by the embankments, can be disastrous to the living-cycle of DUGOnGS, Turtles and other protected marine life in the effected areas.

2.5 These obstructions can also play havoc with the migratory routes and spawning grounds of SHRIMPS if they abound in the area.

2.6 Driver Fatigue……..the alignment and vertical and horizontal Profiles of the causeway have to be such as to cause minimal fatigue-effect from driving in the monotony of water continuum, made worse by sun-glare.

NoTe: Transversely placed culverts can be made in some of the embankments to improve free exchange of water and salt and to benefit shrimp spawning and migration.

3 BasIC CoNsTruCTIoN-maTerIals & TheIr suPPlY sourCes

material Potential sourceStone fill UAE, Iran, OmanSand fill, offshore1) Locally dredged materialSand fill, onshore2) Local sourcesGeotextile Europe, Far East, USAStructural concrete - Coarse aggregates from UAE and Saudi Arabia, Fine aggregates

either locally dredged sea sand or desert sand from Saudi Arabia, - Cement from Qatar, Europe, Far East or USA.

Reinforcement Europe, Far East, USA, Saudi Arabia, QatarCable stay tendons and Prestressing Steel

Europe, Far East, USA

Structural steel Europe, Far East, USARoad Base materials UAE, Oman, Saudi ArabiaAsphalt Coarse aggregates from UAE, Oman Saudi Arabia, Bitumen from sources

in the Gulf AreaCrash Barriers & Railings Europe, Far East, USABuilding work Miscellaneous sourcesLandscaping Local sources

1) Sand fill in embankments, rest areas and protection islands2) Sand fill/imported fill in embankments for interchanges & link roads in on-shore portions.

4 BrIef summarY of WorK reQuIred To Be doNe INITIallY

a) Planning study: review of the existing and planned land use and drawing up Conceptual Local Area Plans for the areas adjacent to the Causeway landing points.

b) Traffic Study: detailing of the Traffic Study for the selected alignment. The traffic forecast for the ‘average daily traffic’ in various years, eventually reaching ?? in 2050.

c) Topographic survey: Detailed survey of atleast a 300 m wide corridor around the onshore


GuidelineS foR deSiGn & ConStRuCtion of meGa CoaStal Sea-linKS in the aRabian Gulf & SimilaR SuRRoundS 39

part of the alignment to create a digital terrain model, and staking of the selected alignment.

d) utility survey: on existing and planned services.

e) Bathymetric and geophysical surveys: Close grid Bathymetric and Geophysical Surveys around and along the selected alignment.

f) geotechnical Investigations and evaluation: onshore boreholes, trial pits and offshore boreholes along with laboratory testing.

These are used as basis for a geotechnical evaluation to establish feasible foundations for bridges and embankments.

g) marine and environmental Impact studies: marine surveys and measurements and the numerical hydraulic modelling for concluding on the ‘Zero environmental Impact’ on free exchange of water and salt across the causeway.

5 CoNCePTual desIgN, TIme aNd CosT sTudY

t Conceptual design:

Required for the following components of the project:

~ alignment

horizontal alignment and vertical profile, including for the interchanges onshore.

~ Bridges

Aggregate bridge length ??, with ?? main navigation span bridges, made as ?? (e.g. cable stayed), with main spans of ?? .

All other bridges to be low level and elevated viaduct bridges

…….generally using the concept of long pre-cast units for foundations, substructure as well as superstructures made onshore and placed by heavy marine lifting equipment). ….. see items #8 to #13 ahead for details.

~ embankments and dredging:

Aggregate of about ?? Length of the Causeway will be made as ‘embankment’ using dredged fill as core material with stone bunds and armour slope protection at the sides.

Extended embankments at ?? locations to provide rest and turn-around facilities for the Causeway users.

~ Tolling and Border facilities:

Tolling facilities may be located onshore along with the Causeway Operation & Maintenance complex.

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~ utilities and services

Utilities and Services required for the Causeway itself in addition to space provision for possible future additions.

t Construction Time

The expected construction period of ?? months as a realistic, albiet tight construction programme.

t Construction Cost

refer to Item # 17 ahead: - nearly us$3,700/sq.m of o/a length (i/c embankments) and 30 m width as in Bahrain-Qatar Causeway (year: 2012)…. but this cost figure will be higher if the length of embankments reduces and those of Bridges increases – NoTe !!!

a) Cost estimate for the off-shore part of the Causeway including services and all onshore facilities and interchanges, -including say 10% per year escalation of price, with rates and costs based on ?? (date) values and best guesses of Contractor’s Direct Costs, but perhaps excluding items such as:

(i) ‘Financing’ cost: as this will require a cash flow analysis, which may be premature at this stage of the project due to the fact that ‘funding arrangements’ may not have yet been defined.

(ii) Cost of Land Acquisition and compensations for proprietary rights.

(iii) Land for work sites and the area required for the Causeway.

(iv) Allowance for Contingencies covering Extra works and Unforeseen Conditions during the construction period (normal and prudent practice for any construction work subject to uncertainties).

(v) Costs of ‘Design-Review’, Construction ‘Supervision’ and ‘Construction-Management’ by the Client’s organisation and the Consultant steering the project.

(vi) Cost of ‘funding arrangements’, as appropriate (i/c any commitment charges), and

(vii) Cost of environmental monitoring from the start of the project up to a certain period after completion of the causeway.

b) The ‘CAPITAL (i.e. initial) COST’ includes all the expenses related to the ‘InITIAL construction’ of the Causeway.

This will include:

- ‘Planning’ & ‘Feasibility’ Studies

- Conceptual and Detailed DESIGn, Drgs., Documentation

- Construction, including Materials, Equipment and Labour

- Supervision and management of construction

- Project financing cost

- Insurance and taxes and duties during construction



- The profiles should:

l avoid wave loads and severe salt water spray on superstructures AnD:

l ensure free vertical clearances as required for the bridges …

7 INsTallaTIoNs aNd serVICes

- Provision of power, water and sanitary systems at Border Stations and Rest Areas.

- Road lighting system all along the Causeway.

- Illumination of bridge structures and embankments.

- Illumination and marking of navigation spans of bridges.

- Traffic Monitoring and Surveillance System (TMSS) to secure safe and efficient use of the Causeway facilities.

- Electroinic Payment Systems for collection of toll and transfer of information to banking systems and administrative systems at the Causeway Authority.

- sCada: ‘Supervisory Control And Data Acquisition’ System for collection of all measurement data and information on the status of Causeway systems.

- Communication systems : for internal and external communication by the Causeway Authority and communication by the travellers.

- Client’s general Overhead costs

- Equipment and Furnishings required but nOT included under the contract(s)

- Inspection and Testing

The ‘oPeraTIoN and maINTeNaNCe’ CosT in subsequent years, over the Causeway life cycle, includes the following expenses:

- Operating staff

- Labour and Materials for Maintenance and Repairs

- Periodic renovations

- Insurance and taxes

- Financing costs

- Utilities

- Client’s other expenses

NoTe:

i) ACTUAL COSTS ‘quoted’ by contractors will NOT always follow straight scientific principles, because there can be nOT-so-SCIEnTIFIC ‘Compulsions’ of ‘Strategy’ and ‘Tactics’ in given circumstances of prevailing Market Forces and Competition !!!

ii) See item # 17 ahead for Approx. “Tender Price weightages”.

6 alIgNmeNT & laYouT

- Large radii horizontal curves in the Alignment assure a view to the oncoming parts of a long Causeway, variation in the view and avoidance of SUn’s GLARE over longer distances.

- This also assures a free view over the sea area and other Causeway elements along the causeway.

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8 desIgN BasICs BorN ouT of eXIsTINg resTrICTIVe CoNdITIoNs: ….i.e. The ‘Conceptual’ ….

(…in a flow-chart format)



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10 heNCe some KeY guIde-lINes for aChIeVINg a raTIoNal desIgN IN PresTressed ‘CoNCreTe’ (WhICh YIelds a CosT- effICIeNT aNd more duraBle sTruCTure) are:

a) relatively ‘short’ span lengths: this is the economical best solution for relatively shallow foundations for the stated substrata conditions

b) Prefabrication in a precast yard on–shore: ‘maximum work on-shore/and minimum work at sea’ is the best solution both for ‘economy’ and ‘durability’.

c) Prestressed Concrete: this material preferred in achieving specified design requirements and ‘durability’ with low maintenance cost

d) repetition in Prefabrication: results in a rational and cost effective solution

e) large Prefabricated elements: shortens construction time and reduces cost but limits weights to 1000 to 1600 T (…..because of limitation on available DRAUGHT).

f) minimum draughT required for the barges mounted with cranes to carry heavy (500T to 1600T) P/c elements:

- The average 5 to 6 m deep stretches along the alignment will allow just about enough draught for these barges to carry about 1000 to 1600 T P/c elements after allowing for waves and clearance under keel for a weather-independent and safe construction progress.

- This sets the weight limit if these stretches do not have to be dredged generally.

- Bridge to be replaced by Embankment in shallower stretches but this curtaining can adversely effect free exchange of water and salt across the causeway &

hence it may be necessary to resort to dredging and provide Bridge cf. Embankment.

g) The selection of a limiting LIFTInG CAPACITY of 1000 to 1600 ALLOWS the construction to be carried out with lifting equipment that has been tried successfully and that can be obtained in the construction market albeit at cost ! ….Reference: King Fahad Causeway ((26 km. long Saudi-Bahrain Sea-link)

Such ‘cost’ becomes necessary for meeting requirements of Construction for respecting durability and fast track completion of work.

h) Longer spans, requiring heavier lifts, would increase the required draught, and hence the water depth, and hence the dredging requirement. !!!

This would require additional dredging in ‘localised areas’ and for ‘deeper dredging’ for the entire length some Bridges.

Due consideration has to be given before the idea of heavier lifts is given-up.

i) For an oceanic structure, a relatively short span of 50 m. may be considered adequate in view of relatively shallow depth of foundations but the cost difference between 50 m span and longer spans up to 65 m is within a few percent. This can be looked into in the detailed design.

j) Infact even the span articulation of ‘50 m spans with 8 m cantilever arms’ and ‘34 m drop spans’, as in the King Fahad Causeway (KFC), could also be looked into in detailed design stage, yielding a determinate structural system too – provided the water depth is atleast 7 m to provide ample effective Draught.

11 CoNCePTual desIgN

a) The conceptual design for the Viaduct Bridges may have span lengths of about

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50 m (o/a deck width nearly 30 m all bridges) with superstructure consisting of two independent precast prestressed concrete box girders (each carrying two lanes a footpath and part of the central verge).

b) p.s.c Box-Girders may be prefabricated generally in SPAn-LOnG butterfly modules (centre of span to centre of span) and installed from barge or crane, with about 25 m outstanding arms.

c) 350 m distance between successive Expansion Joints for majority length of the

viaducts (18+25+6 @50+7= 350 m semi-continuous units). At Abutment-ends: (18+6@50+10= ) 328 m semi-continuous units.

VIaduCT BrIdge INsTallaTIoNs aNd serVICes

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d) A halving-joint ‘articulation’ at a distance of 7 m from pier–support may be chosen as the structural detail at Expansion Joints.

e) A prestressed halving joint is considered complicated to construct but functions well when analysed, designed, detailed, laboratory-tested and then constructed professionally – as was successfully done for the King Fahad Causeway (Sea-link).

longer delays during installation of numerous such foundations in the open sea.

12 ‘CoNsTruCTIoN’ aNd ‘ereCTIoN’ CoNCePT

a) The conceptual study suggests adoption of large prefabricated prestressed concrete elements for foundations, for substructure as well as for superstructure.

b) for superstructure:

l Typical p.s.c. box units may be fabricated in ‘span-long’ (or longer) lengths.

l These very long p.c. psc box units (50 m. or longer) may be constructed as being balanced cantilevers about mid length point and placed as such on piers (their internal double cantilever post-tensioning cables installed and stressed in the precast yard).

f) Externally installed continuity cables in the supersturcture may be placed to facilitate easier erection and to accommodate discrete angular changes at in-situ stitches without introducing kinks in the post-tensioning.

Adjoining cantilever tips of successive butterfly units in a semi-continuous unit are stitched together by c.i.s. stitches and continuity cables threaded and stressed.

g) Conceptual Substructure Configuration

- The (drilled) pile foundation working is less prone to adverse weather conditions in comparison with open and caisson foundation working, with the benefit of an almost uninterrupted construction cycle.

- INTeruPTIoNs are likely to be more problematic for the open and caisson foundation where adverse weather conditions will cause



l After their erection at site as double cantilever butterflies, the external continuity cables may be installed and stressed after concreting/grouting of in-situ ‘stitches’ between successive elements.

l Precast prestressed elements are carried by crane or barge to the location of installation and then lifted into their final positions.

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l The elements are erected with utmost care as balanced double cantilevers with the pier support at the centre of gravity for each p/c psc double-cantilever ‘butterfly’ element.

l Positioning the lifting points is of paramount importance as also the presence of fair weather and wind.

l It is necessary to erect these double-cantilever elements on temporary jacks with the capacity to adjust the final positioning in both vertical and horizontal directions.

l Once the double cantilever girder is located correctly the permanent Bearings are built into the structure.

l The next step in the erection scheme will then be to construct the “in-situ stitch” between the adjoining cantilever tips of successive girders (between the Halving Joints) thereby making the unit between the Expansion Joints semi continuous.

l At the prescribed cured age of the in-situ stitch, the external continuity tendons can be installed and tensioned.

l The temporary post-tensioning bars can then be released and removed.

c) for substructure and foundation:

- Boring (drilling) large dia. vertical “holes” for piles

- Two jack-up platforms may be used for drilling the large dia. Holes in the sea bed for p.c. p.s.c. tubular piles. Two adjacent positions could be drilled by using two drilling rigs from each platform.

- After installation of the steel ‘casing’ by crane from the jack-up platform, the drill is lowered in and drilling into the hard layers is carried out to the required founding levels.

- The pre-cast p.s.c. tubular piles, varying in length (with a maximum weight of approximately 400 T after assembly) will be transported to the yard’s port by the large travelling gantry crane.

- There the pile will be taken over by a special pile barge. Once at the site, the pile will be lifted up above the casing by 1000 T floating derrick and lowered into the bore hole.

- Finally the annular space between the outside surface of the pile and the surface of bore hole will be filled shut with cement grout.

t rate of drilling for the nearly 4.75 m dia. pile holes can be between 1.0 to 1.5 m per hour in rock ...Imagine CHEWInG through so much rock so fast !!!

t On an average, 4 to 4.5 Piles (i.e. FOUR-and-a-HALF Foundations –based on one such Pile per foundation) can be placed in position per week ( perhaps nothing can be faster !! )

Placing p/c p.s.c. tube pile in a pre-drilled hole



t for Viaduct Bridges

- The substructure could comprise of p.c. p.s.c. tubular single (or double) pile (depending on height of deck) and single p/c p.s.c. tubular pier shaft unit.

- The steel casing, mentioned earlier, supports the surrounding soil while drilling and while installing the prefabricated pile unit.

- The steel casing is withdrawn while grouting the annular space between soil and pile.

- Installation of pile casings, bottom seal concreting and grouting are carried out from the jack-up platform:

l working for two adjacent piers simultaneously.

- To allow for the variation in pier and pile length due to variable elevation of roadway and pile tip, a large number of different-length precast pier and pile units has to be considered.

- A selection of pile ‘adjustment-sections’ in intervals of 0.3 m should allow for any late decision of final pile tip elevation.

- The ‘adjustment-sections’ can be added to the bottom of the pile at the last minute before it is prestressed and transported for installation.

- Confirmatory Geotechnical investigations

have to be done for each pile (at its exact final location during construction) for deciding its exact length.

- Despite all this, where the founding level may, at the last minute, require to be taken slightly deeper still, suitable concrete pedestal can be cast under–water in the pre-drilled hole and then the already prefabricated psc pile installed on it.

assembling a precast pile, then prestressing it

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13 PrefaBrICaTIoN Yards

a) One or more prefabrication yards will need to be established on-shore at a location where a temporary harbour facility, with 5-7 m water depth, can be constructed.

b) The fabrication yard provides areas for steel fixing, pre-casting of units, pre-assembly, prestressing, storage, concrete batching facilities, offices and stores, workshops, etc.

c) The temporary harbour is to be protected by breakwaters and has “load-out” facilities for the prefabricated elements and ‘quays’ for unloading of concrete aggregates, cement, reinforcement, etc., and berthing and service of marine construction plant.

d) A single construction yard for fabrication of all p.c. elements may be the most cost efficient arrangement.

e) Should it be decided of establish more fabrication yards, each facility should be dedicated to fabrication of one type of elements e.g. piers or deck units, to reap the benefit of repetition in production at same site.

f) In a long causeway, a second fabrication yard with a parallel production would be an advantage because this provides a full back-up.

The prefabrication yard is arranged such that pile units, pier units and deck units are constructed ‘between the tracks’ of a 1000t gantry crane.

14 ProJeCT magNITude

a) For a ‘large’ project, a decision on the number and scope of contracts constituting it may be critical to the eventual success of the project.

b) Having multiple contracts will give the Employer more control than under a single contract for the entire project, and it may be

more economical because of maximising competitive pricing.

c) On the other hand, multiple contracts will require more interface management from the Client’s organisation.

The contract “packaging” could perhaps be divided into the following contracts:

lContract No 1: The Off-shore portion

lContract No 2: The on-shore portions

d) The ‘offshore’ part of the Works could perhaps be done on “design-and-Build” basis, while the “on-shore” works need not necessarily be of a “Design-and-Build” nature – could be done as traditional ITem-raTe construction contracts.

The characteristics and scope of each contract will determine the party responsible for the design of the Works.

e) Under a desIgN+BuIld contract, the “desIgN resPoNsIBIlITY” is assigned to the Contractor.

Obviously he is likely to economise in terms of his costs, which may be at the expense of quality.

heNCe, it is considered essential that the emPloYer has the appropriate TeChNICal eXPerTIse on hIs side in order to ensure that his requirements are elaBoraTed in the tender documents aNd …..are aChIeVed in practice !!!

under a design + Build contract :

‘VarIaTIoNs’ should be ‘instructed & understood ’ as ‘varied requirements with which the Contractor’s ‘design’ MUST COMPLY’, and NoT as a ‘varied design as if INsTruCTed by the employer’ (- nO !!), and



the ‘consequences’ of such variations and ‘cost-repercussions’ should be agreed to in advance, so as to minimise any disputes later.

Although Design-Build may appear somewhat inflexible in the sense of the employer having a limited involvement in the detailed design, but it does enable him to have the BeNefITs of:

i) lump-sum pricing,

ii) the Contractor’s undivided liability for the works (including for design), and

iii) the potential saving (in cost and time) due to a degree of ‘overlap’ of the Contractor’s “design and construction Activities” – because both are his own and he must adjust them to suit his WORK !!!

iv) the potential saving (in COST and TIME) due to the fact that the “contractor’s design” can be geared towards construction methods & principles & details for which he has just the right Experience and Resources.

The effect of “overlap” of HIS OWn design and construction activities can lead to a SHORTER contract PERIOD than in an “Employer-DESIGnED” contract (where entire design must be completed first and only then the Documents put together and Tenders invited only thereafter).

15 rIsKs aNd eXTerNal INflueNCes:

a) The Causeway Project can be exposed to RISKS BOTH during Construction AnD Operation, which could potentially lead to a DELAY in costruction, an economic loss, a negative impact on the environment and/or loss of life !!!

b) In the allocation of risks, the foremost principle is that the Employer, the Contractor and the

Employer’s Representatives should act in a spirit of mutual trust and cooperation.

c) The sound PRInCIPLE OF RISK ALLOCATIOn is to ALLOCATE the RESPOnSIBILITY for the RISK to the party which had the BEST “OPPORTUnITY” to FORESEE & MAnAGE the RISK.

d) Many clients want to allocate ALL RISKS to the COnTRACTOR, without realising that in doing so they inevitably will ‘pay a high price for such risk- allocation’.

e) A professional Contractor will carefully evaluate all risks associated with a contract and then factor them in and PRICE it ACCORDInGLY.

f) Risk ‘identification’

The following hazards are the possible causes of risk:

- Unforeseen ground conditions (always a risk)

- Major currency fluctuations.

- Inflation.

- Extreme weather and sea conditions.

- Accidental impact with fresh water aquifers – if encountered.

- Accidental impact to third party installations, pipelines, etc.

- Traffic accidents involving construction vehicles

- Impact on navigation and fisheries from marine ‘construction-activities’

- Impact of increased amount of silt in the water from dredging and embankment construction

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g) risk ‘allocation’

- The Contractor may allocate the risk of currency fluctuations and inflation to the Employer, and typically some such adjustments to the tender price could be made during the contract period under ‘Escalation’ clause.

- The CoNTraCTor should be ‘responsible for’ and ‘carry the risk of’ CoNTrollINg the Planning, the Design (if his), the Construction, and the Safety.

- The risk towards the unforeseen ground conditions, climatic risks and contamination of aquifers could be dealt with by setting predetermined “values” in the contract.

- The onus of majority of the risks still lies with the Contractor, AnD the fact that such “values” have been ‘pre-specified’, and as such “have been BID upon”, is advantageous to the Employer – even at some additional BID-cost !!

- It also means that any dispute arising could be settled better by referring to these “predetermined” aspects.

- The risk towards the Environment and for containing the possible damage there-to should rest with the Contractor….

for instance: ‘containing’ dredging and reclamation of spill within set parameters.

16 CoNCePTual CoNsTruCTIoN Programme

a) The COnSTRUCTIOn TIME is governed by TWO CRITICAL PERIODS of ACTIVITY , viz :

- Mobilisation and construction of temporary works:

- Fabrication and installation of viaduct bridges

and approach spans to the main bridges:

b) Construction of Embankments, Road works, Buildings and Toll stations is nOT critical for the overall construction time AnD can be carried out simultaneously with the off-shore work.

c) The Construction Programme is divided into following maIN aCTIVITIes:

i) Mobilisation & site installation

ii) Design

iii) Soil investigations

iv) Procurement

v) Temporary works

vi) Embankment construction

vii) Pre-fabrication

viii) Viaduct bridges

ix) Main bridges (over navigation spans, if any)

x) Road works on embankments

xi) Interchanges and Road works

xii) Buildings and Toll stations

xiii) M&E installations

xiv) Landscaping and finishing

xv) Commissioning

d) a description of the oVerlaPPINg main elements of work in the programme is indicated below:

I mobilisation and site Installation

- Mobilisation and site installation includes land surveys, purchases, permits, recruitment and movement and the establishment of camps and major work sites for prefabrication of large concrete units.



- It includes design and construction of camps and living quarters for staff and workmen.

II design

Design activities are commenced upon award of Contract based on the conceptual design and supplementary geotechnical investigations made available to the tenderers during the tender process.

III soil Investigations

Supplementary Detailed geotechnical investigations are carried out in parallel with the design.

IV Procurement

- This activity comprises sourcing and procurement of major materials and subcontracts.

- It includes design, fabrication, commissioning of construction plant and a large fleet of specialist marine equipment.

V Temporary Works

Temporary works are extensive, involving the preparation of work sites, dredged channels and harbour facilities for the prefabrication yards and establishment of minor work sites at landing points on embankments, and include all the Lifting Equipments, Cranes, Barges, any Jack-up-Platforms, Drilling Equipment, etc.

VI embankment Construction

- The required number of the landing points are assumed strategically located at “deep water” for placing and storing of materials.

- If necessary, the work can be accelerated by allocation of more resources.

- The activity is non-critical for the overall

completion of the Causeway.

VII Prefabrication (Precasting)

- Generally, Prefabrication is planned to be carried out on two production lines - one for pier and the other for deck units, respectively.

- This, for a major project, should push for and enable a theoretical output of two pier units and two deck units per working day !!! (ref. KFC).

- Allowing for LEARnInG PERIOD and DOWn TIME, the AVERAGE OUTPUT can be upto 4 units per production-line per week.

- A ‘phased’ start up of each production should allowed for.

- Fabrication of pre-cast pier and deck units is time critical to the construction duration.

VIII Viaduct Bridge Construction

- The viaduct bridge elements are erected by large floating cranes.

- The construction duration is matched with fabrication of pre-cast units in order to keep the overall construction time to a minimum, but this requires considerable and costly resources, depending on the project size.

- The marine activity is exposed to down time from wind and waves.

- Erection of viaduct bridges is ‘TIME- CRITICAL’ to the programme.

IX. main Bridges - if any (...may be cable stayed or p.s.c. box girders built in free cantilever, etc.)

These bridges are constructed with a lag time between them, allowing e.g. the pylon construction and installation of cable stays to

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be carried out by COnSECUTIVELY using the SAME resources.

X road Works

- Laying of sub-base is anticipated to commence shortly after compaction activities for subgrade are completed on the embankments.

- This activity may nOT be time critical. Road base and wearing course will be laid after substantial completion of the works.

XI INTerChaNges and road Works

- This activity may nOT be time critical.

- It will however start ‘ahead’ of the road works on the fixed link to create a convenient interface.

- Work on the interchanges can be carried out concurrently with the road works.

XII INTerChaNges and road Works

- This activity may nOT be time critical. It is desirable that the “land works” start as early as possible in order to create a more convenient access to the work site.

- Work on the interchanges can be carried out concurrently with the road works.

XIII Buildings and Toll stations

- Buildings and toll stations at the landfall sites can commence shortly after completion of the design whereas commencement of building works for the rest areas must await the reclamation and compaction activities, as required.

- Building and toll stations are not considered critical activities in the programme.

XIV. m&e Installations

M&E installations can commence when the embankment and bridge construction is substantially completed or buildings and toll stations have been constructed at the landfalls.

XV. landscaping and finishings

Landscaping and finishing will proceed after substantial completion of the construction works.

XVI. Commissioning

The proper completion and functioning of the Causeway will be documented generally through a few months commissioning period leading to the inauguration.

17 aPProX. “PrICe - WeIghTages” (excluding items indicated earlier in item #5.)

Assuming aggregate length of off-shore Bridges to be about 25% more than aggregate length of off-shore embankments, cost of on-shore work nearly 20% of off-shore work, water depth permitting only about 3 m effective depth of draught (average. Water depth about 5 - 6 m.) …..as in the case of the proposed B-Q Causeway which has a 40 km. coast to coast portion – 22 km. of Bridges and 18 km. of embankments – and an aggregate of 12 km. of flyovers/interchanges in land portions TOTAL length 52 kms. and width of Bridges nearly 30 m. :



main Item Cost Weight % of o/a total

Preliminaries 100 18%General 9Temporary Works 14Site Facilities 38Major Construction Equipment 33Miscellaneous 6Dredging, Embankment and Excavations 100 16 %Embankments and rest areas 71Earthworks for bridges 19Dredging and depositing 10Structures – Bridges (off-shore) 100 25 %Piling and Foundation 25Piers 9Superstructure 50Major bridge erection / installation works 16Structures – Interchanges (off-shore) 100 1.5 %Interchanges 80Overpass bridges on rest areas 20Road works 100 5%Road works on embankments (incl. rest areas) 30Road works on bridges 40Interchanges and Link roads 30Terminal areas, toll stations and buildings 100 1.5 %Border Facilities (Onshore) 63Rest Areas 23Tolling Facilities 14engineering Installations 5 %Contractor’s Overhead costs 100 21 %Detailed Design and suppl. geo. Surveys 14


58

Bonds and Insurances 7Testing, commissioning and defects liability 9Staff salary 19Contractor’s margin 51adjustment for escalation (for one year) 7%Total estimated tender price1) * 100 %

1) variation expected to be within +/- 20%. * see top of next page*nearly US$3,700/sq.m of o/a length (i/c embankments and onshore works) and 30 m width ( Bahrain-Qatar Causeway…year 2012) …. BUT this cost figure will be higher if the length of embankments reduces and those of Bridges increases - NOTE !!!

18 oPeraTIoN & maINTeNaNCe (o&m) CosTs

- ‘aNNual’ o&m cost during the expected lifetime of the Causeway is expected to be in the range of 1-1.5% of the construction cost.

- This is an average figure that covers substantial timely variation throughout the service life of the Causeway (little maintenance repair is expected in the first 15-20 years after inauguration).

- ...........‘average annual’ ‘BrIdge’ maINTeNaNCe cost. is expected to account for approximately 0.50 - 0.75 % of the original construction cost.

- ....whereas the amount for ‘emBaNKmeNT maINTeNaNCe’ is expected to be substantially lower, probably about 0.25% of the original construction cost.

- The o&m cost is listed as an ‘average yearly cost’ during the expected lifetime of the Sea-link (Causeway).

The views expressed in the paper are personal views of the Author. For any query, the author may be contacted at:E-mail: [email protected]

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iv) SOAR-22 “State-of-Art-Report: Areas of Application and Techniques of Instrumentation in Traffic Engineering” Price `600 + `30 for Packing and Postage

v) Souvenir/Technical Papers-Seminar on “Recent Trends in Highways Development” 10 & 11 October 2012 Price `600 + `40 for Packing and Postage

b) Revised Publications: i) Second Revision of IRC:53-2012 “Road Accident Recording Forms A-1

and A-4 Price `200 + `20 for Packing and Postage

ii) Third Revision of IRC:67-2012 “Code of Practice for Road Signs” Price `1000 + `40 for Packing and Postage

iii) First Revision of IRC:103-2012 “Guidelines for Pedestrian Facilities” Price `600 + `40 for Packing and Postage

Copies of these publications can be obtained from IRC Office against cash payment or can be purchased online through IRC website: www.irc.org.in. For more details please contact + 91 11 2338 7759 or E-mail: [email protected]

* Students pursuing BTech/MTech/Phd courses can avail 25% discount on purchase of IRC publications.


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statement about ownership and other particulars about Newspaper (JourNal of The INdIaN roads CoNgress)

to be published in the first issue of every year after the last day of february

form IV (See Rule 8)

1. Place of Publication … Delhi

2. Periodicity of its Publication … Quarterly

3. Printer’s Name … Madan Lal Goel

Nationality – whether citizen of India … Indian (if foreigner, state the country or origin) Address … M/s. Aravali Printers & Publishers (P) Ltd. W-30, Okhla Industrial Area, Phase-II, New Delhi-110020

4. Publisher’s Name … Vishnu Shankar Prasad

Nationality-whether citizen of India … Indian (if foreigner, state the country or origin) Address … Secretary General, Indian Roads Congress, Jamnagar House, Shahjahan Road, new Delhi-110011

5. Editor’s Name … Vishnu Shankar Prasad

Nationality-whether citizen of India … Indian (if foreigner, state the country or origin) Address … Secretary General, Indian Roads Congress, Jamnagar House, Shahjahan Road, new Delhi-110011

6. Names and address of individuals … Indian Roads Congress, who own the newspaper and partners of Jamnagar House, Shahjahan Road, shareholders holding more than one new Delhi-110011. percent of the total capital

I, Vishnu Shankar Prasad, Secretary General, Indian Roads Congress, hereby declare that particulars given above are true to the best of my knowledge and belief.

Vishnu shankar PrasadDated: 1 March 2013 Publisher


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