Construction and Supervision2

2.1 INTRODUCTION

The executing agencies/contractors would submit the overall work programme and get it approved. Laboratory should be established wherever required as per the contract and the construction materials should be approved. Proper and timely mobilization of required staff and machineries by the contractor is essential. A system may be established for regular review meetings with the management of the contractor and the consultant. Monthly meeting by higher authority and weekly meetings by the Resident Engineer/ Executive Engineer to review work progress help to a great extent. The scheduled time of completion may be shortened (i.e., one year time of completion may be shortened to ten months) and the work programme may be made accordingly to facilitate meeting targeted time of completion. Problems and solutions are easily sorted out during such interactions. Method of supervisory consultancy, assisting the engineer (in this case representative from the employers’ side) is more preferable for smooth and timely completion of work. The system of requests for test (RFT) method and approval on the same day helps keep the rapid progress of the work. Wireless system with the client, contractor and consultant is more effective for taking prompt decision on any problem. The overall aim of all concerned should be to maintain coordination for successful completion of the work as per requirement of the contract.

2.2 CONSTRUCTIONAL ACTIVITIES

Design and construction of road projects are totally different from each other and when it comes to execution in practice it becomes a very challenging task. The construction of road projects is not only dealt with steps to be followed according to the design considerations and conventional methodology, but also to adopt some technical strategies to overcome different problems that arise at the site. For this, effective measures from the site or project engineer plays an important role. Some important constructional activities are mentioned and described in detail and are as follows.

10 Fine-Tuning of Road and Building Projects

face. This helps in the formation of proper joints between old and widening portions of the road. The excavated faces should not be left open for long to weathering action. Infi ltration of rainwater and movement of vehicles near the excavated face damages the existing road.

(iii) It is important to review the crust condition of the existing road at the time of taking up the widening work. There is normally a gap of some years between the period of initial survey and work execution. Some of the existing crusts get damaged more during this period due to various reasons and they may need reconstructions instead of mere strengthening.

(iv) Existing road with clay sub-grade when widened on either side with soil of higher density behave differently. Differential settlements are likely to take place in such areas. Each such case may be examined properly before execution of the work.

(v) Construction of embankment in low-lying waterlogged and swampy areas needs special attention. The normal solution is to remove the mud and provide proper drainage from construction stage with vertical and horizontal cut-off. Provision of deep drain on sides provides the vertical cut-off and laying layers of sand at bottom of embankment provides the horizontal cut-off. Proper height of embankment here should be ensured while considering the bottom of drainage layer above HFL.

(vi) While conducting tests for compaction, the MOD of the inside material should be given more importance rather than the MDD determined for the borrow areas.

(vii) Care should be taken to ensure that proper degrees of compaction are achieved at edges.

(viii) Surface regularity should be achieved as per codal provision. Surface regularity of earth work in embankment affects regularity of the GSB layer.

(ix) Cross-section is generally available at 20 m interval for straight reaches and at 10 m interval for curves. Interpolation of levels should be done for intermediate locations, to construct best possible curves and irregular ditch locations. More attention is required for transitions and apex locations.

(c) Granular sub-base

This layer should be constructed with a granular mix of specified gradation limit for the size of ingredients. Generally, the materials are rarely available with required composition form and therefore mix should be prepared by physically mixing sand, moorum, pebbles or crushed aggregates to achieve the required gradation and CBR value followed by resilient modulus.

12 Fine-Tuning of Road and Building Projects

Fig. 2.1 Application of prime coat over granular course through spreader.

A tack coat material in the form of performance grade (PG) binder or a bitumen emulsion thin layer is applied between bituminous concrete and dense bitumen macadam to promote the bonding between them and the tensile strength as well as shown in Fig. 2.2.

Fig. 2.2 Tack coating over dense bitumen macadam (DBM) through spreader.

(g) Bituminous concrete (BC)

This has to be laid over the DBM in the same manner as the DBM is laid over the WMM. However, the surface of the DBM has to be cleaned properly and the tack coat should be applied as per required quantity. Surface regularity should be checked frequently. Test pit holes should be filled up properly.

(h) Hard shoulder and earthen shoulders

These works should be taken up immediately following the carriageway construction. The surface slopes of the shoulders should be maintained properly to allow surface drainage. The hard shoulder may have premixed

Construction and Supervision 13

carpet top instead of surface dressing. Surface dressing where provided should be covered with seal coating immediately. Such work should be avoided just before monsoon in order to prevent penetration of rainwater reaching the unconsolidated layers, without having proper binding due to bleeding of the bitumen.

(i) Slope dressing

Both the sides of the road should be trimmed immediately after construction of the shoulders.

(j) Turfing/ Pitching

Drains along with protection work like turfing and pitching should be taken up as slope protection work. The turfing and pitching should cover the 300 mm rounded edge of the earthen shoulder. The top of the turfing and pitching may be kept at 25 mm lower levels at the edge of the earthen shoulder so that surging water can flow easily from the shoulders over the turfing or the pitching as shown in Fig. 2.4.

(k) Drains and protection works

The type of drain will depend on availability of land, location and height of the embankment. V-Shaped concrete lined drains can be adopted

Fig. 2.3 Road marking with thermoplastic paint with machine for different purpose.

14 Fine-Tuning of Road and Building Projects

conveniently in both rural and urban areas. Well planned crossroad at limited locations of the drain will help in control of traffic approaching the main highway. This drain will restrict random entry of traffic to the highway in rural as well as urban areas and there will be reduction of accidents. Sill of roadside drains should be minimum 300 mm below the GSB bottom level so that the road will not be affected with rise of water table inside the neighboring land during rainy season, and it will act as cut-off. Roadside top of masonry drain should also be kept at 50 mm lower level to allow free flow of surface water from the road. If the wall of the drain would be at a higher level than the road, the surface drainage would be obstructed and there would be longitudinal rain cut and scouring effect on side of the road. The purpose of such a drain will not be much fruitful.

(l) Road furniture

The delineator, guard post, signboard and guard rail are considered road furniture. The delineators should be fixed with greater gaps than the guard posts. Reflecting portion of the delineators may be painted rather than fixing the metallic reflectors as it prevents theft of the reflector. Provision of guard posts on both sides of road on curves creates a balanced safety condition. Use of guard posts may be encouraged. Signboards may be fixed on roadsides at different heights to protect these from vandalism and damages. A minimum gap height of about2.5 m above road level should be maintained.

(m) Road marking

Thermoplastic paint when used should be applied at a proper temperature. The road surface should be cleared properly. Excessive bitumen may be removed from bleeding areas of the road and the road surface should be stabilized before application of paint as shown in Fig. 2.4.

Fig. 2.4 (a) Turfing of highway embankment near Grand Prairie, Texas. (b) Stone pitching on highway embankment near district Killa Saifullah.

Construction and Supervision 15

(n) Cross-drainage structures

Old structures retained in position should be properly checked for structural stability. Substructures and floor protections of the old structures need additional attention. It should always be insisted to complete checking of reinforcements, shuttering and gradation of materials, etc. on the previous day of the date of concreting.

(o) Steps for road safety measure

During construction of road, safety of the road should be sincerely taken into consideration. The safety measures for road users include installation of traffic related information throughout on road markings, roadside informatory signs, signalized intersections through manual or automatic systems, etc.

(p) Arboriculture

Roadside plantation of tree and plantation of plants in the medium of road should be planned from the beginning.

(q) Provision of utility service

Separate planning from the beginning should be made to provide passage for utility services.

(r) Provision for boundary line

Boundary pillars should be fixed from the beginning to identify the boundary line.

(s) Guarding against encroachment

The boundary trench line, utility services line and pathway for cultivators can restrict the encroachment. All types of possibility for preventing encroachment should be taken care of.

(t) Common aspect

Work activities should not be held up for want of clearance from the supervising staff. Work pattern of the staff should be so arranged so that the executing agency (contractor) gets assistance readily as required under the contract conditions.

2.3 MAINTENANCE STRATEGIES

Maintenance contracting and its implementation require well drafted detailed contract document clearly specifying the contract conditions, tasks and quality requirement. Laying down of performance standards, time limits for rectification of defects and setting up of arrangements for strict monitoring are essential to achieve the specified level of service of road users. In the light of the above, the following maintenance schedules

Construction and Supervision 17

2.3.4 Protection of Slopes of Embankment (i) Turfi ng and pitching have been provided at essential places as

per observation in the past. However, rain cuts at other locations may be observed from time to time and turfi ng may be taken up suitably, covering 300 mm lap from the formation edge on the earthen shoulder.

(ii) The turfi ng should always be done in a manner so that the top level of turfi ng remains fl ush with the earthen shoulder with 4% camber for allowing free fl ow of water from the earthen shoulder to the side slopes as shown in Fig. 2.3.

2.3.5 Drains (i) Care should be taken to see that the drains are cleared regularly

and there is no obstruction to the fl ow of water. (ii) Both earthen and masonry drains may be cleared periodically but

care should be taken to do it at least before and after monsoon. (iii) As far as obstruction of fl ow inside drain is concerned the drains

should be covered and a proper bed slope should be provided.

2.3.6 Road Furniture (i) The guard posts, delineator posts, including signboard posts and

grills/pedestrian guard rails, kerbs of bus bays and junction may be painted every three year interval as recommended by the consultant.

(ii) Damaged road furniture may be replaced suitably.

2.4 CONCLUSION

The successful execution of the ADB funded Sambalpur-Rourkela road project has brought in certain institutional improvements and has led to enlargement of our vision in handling major road projects. Many critical problems with right solution have been experimented and found successful. These have also enlightened young engineers. It can be said with confidence that execution of this road has led to promotion of new technology for road construction in the state. The present book high- lights the engineering challenges in design, execution and maintenance of this important road project.