INTRODUCTION

Several large structures, such as dams, tunnels, power houses, etc. require huge quantities of

concrete and other building materials which justify mechanical handling and processing. This requires

special aggregate and concrete preparation plants.

Construction equipment is an important aspect of construction planning Varying with the

degree of mechanization on a project, the cost of this equipment may range from 10 to 30% of the total

cost of a construction project. Besides being a sizeable portion of the capital investment the proper

selection and application of this equipment is essential to achieve the construction targets, and to keep

construction costs low. For developing countries, in particular, the correct planning and utilization of

this equipment is of utmost importance in view of the large content of foreign exchange involved in the

acquisition and maintenance of this equipment. The low availability (below 50%) of this equipment on

projects in this country points to the vital need in this regard. It would be worthwhile to keep

informed on the extent of indigenous manufacture while selecting equipment for a project.

Planning and selection of proper type, size and make of equipment is absolutely necessary if

construction targets are to be met and costs kept low. The site geology, topography, climate and location

will influence equipment selection. The planner must decide between old and new machines, between

different makes of the same type and between standard and non standard sizes. His choice should be

made as far as possible, on objective considerations, past experience and on information from similar

works executed in the recent years or under execution at the time. Products of established leading

manufacturers are generally likely to be less expensive in the long run than those of comparatively

unknown manufacturers, and should be preferred on large and important jobs.

Performance calculations for equipment considered for selection have to be made in order to

select adequate capacity in size and number. These calculations should be based on factual or

recommended values of cycle times or outputs. Proper sizing of equipment that is required to work as a

team must be done so that the different units match with each other. Waiting by one equipment for the

product or services of another piece to equipment essentially results in lost production and increased unit

costs.

Economics of construction equipment to compute the hourly working rates is another important

aspect of equipment management. Since the acquisition of construction equipment amounts to capital

investment proper cost accounting of these assets is necessary. Upkeep of equipment records on the

project invariably aids in this task.

Preventive maintenance and field repairs of construction equipment assume great importance in

view of the fact that this equipment is usually employed under severe job conditions of geology,

topography and climate As the machines are scattered over a wide area proper supervision becomes

difficult and the equipment is likely to be handled in a rough way by the operating personnel. Proper care

and maintenance of the machinery is. therefore, increasingly important.

Recently, advances have been made in analytical methodology using techniques of systems

analysis in problems of equipment management. Though sophisticated in approach, these techniques can

be employed in equipment problems through proper education and training methods help in a realistic

assessment of the capabilities.

India’s critical need for power

Severe power shortage is one of the greatest obstacles to India’s development. Over 40

percent of the country’s people -- most living in the rural areas -- do not have access to electricity

and one-third of Indian businesses cite expensive and unreliable power as one of their main

business constraints.

India’s energy shortfall of 10 percent (rising to 13.5 percent at peak demand) also works

to keep the poor entrenched in poverty. Power shortages and disruptions prevent farmers from

improving their agricultural incomes, deprive children of opportunities to study, and adversely

affect the health of families in India’s tropical climate.

Poor electricity supply thus stifles economic growth by increasing the costs of doing

business in India, reducing productivity, and hampering the development of industry and

commerce which are the major creators of employment in the country.

Hydropower development -- a key government initiative

To boost economic growth and human development, one of the Government of India’s

top priorities is to provide all its citizens with reliable access to electricity by 2012. To ensure

that the uncovered 40 percent of Indian homes get electricity by 2012, and to serve rising

demand from those already being served by the power grid, the government estimates that the

country will need to install an additional 100,000 Megawatts (MW) of generating capacity by

2012, expanding grid-based generation to about 225,000 MW. Given that India added about

23,000 MW during the last Five Year Plan of 2002-2007, this will be quite a quantum jump.

The Government of India has decided to acquire an increasing portion of this additional power

from the country’s vast untapped hydropower resources, only 23 percent of which has been

harnessed so far. India’s energy portfolio today depends heavily on coal-based thermal energy,

with hydropower accounting for only 26 percent of total power generation. The Government of

India has set the target for India’s optimum power system mix at 40 percent from hydropower

and 60 percent from other sources.

Advantages of hydropower

When developed in accordance with good environmental and social practices,

hydropower plants have the advantage of producing power that is both renewable and clean, as

they emit less greenhouse gases than traditional fossil fuel plants and do not emit polluting

suspended particulate matter (from the high ash-content of indigenous coal).

Hydropower plants can also start up and shut down quickly and economically, giving the

network operator the vital flexibility to respond to wide fluctuations in demand across seasons

and at different times of the day. This flexibility is particularly important in a highly-populated

country like India where household electricity demand is a significant portion of total demand

and this demand in concentrated in a short period of time (usually in the evening). As an

illustration, if the approximately 150 million households in India were to turn on two 100 watt

light bulbs at 7 pm, the power system would experience an instantaneous surge in demand of

about 30,000 MW! Today, this peak demand is often met by households turning on small

gasoline and diesel generation units, which, in addition to being polluting, are a serious health

hazard in congested areas. And, with rising wealth, households are switching on a lot more than

two light bulbs. Although hydropower plants are subject to daily and seasonal variations in water

flows (which affects the production of electricity at that point in time), they are not subject to the

fluctuations in fuel costs that trouble thermal power plants.

While hydropower plants have large up-front capital costs, they also have long and

productive lives, which significantly help reduce costs over time. For example, the Bhakra

Nangal plant, now more than 40 years old, has operating costs of only Rs 0.10 or US$ 0.002 per

unit. Hydropower plants are thus generally cheaper in the long run than natural gas-based plants,

which are constantly at risk from fuel price increases in the global market.

While India plans to develop mainly run-of-the-river projects, multipurpose hydropower

plants with water storage facilities can help manage critical water resources in an integrated

manner by serving as flood controllers as well as sources of irrigation and much-needed drinking

water. The Tehri Dam in Uttarakhand, for instance, which was commissioned in 2006, today

caters to one-third of the drinking water needs of Delhi, India’s capital.

Besides which, India’s hydro-resources are largely available in some of the least-

developed parts of the country and hydropower plants, if designed appropriately offer significant

potential for regional development and poverty alleviation. Hydropower projects that forge

equitable systems of benefit-sharing and implement targeted local area development can help

local communities improve the quality of their lives quite significantly.

Challenges of hydropower development

While hydropower plays an important role in the energy and development strategies of

India, such natural resource projects are inherently challenging. Environmental and social

impacts are inevitable but they can be mitigated. Hydropower development in India has seen

significant strides in understanding and addressing these impacts and the lessons learned from

past engagements are now being incorporated in project selection and design.

These lessons, coupled with suggestions from civil society, have resulted in changes to

the laws and regulations that govern hydropower development today. As a result, there have been

improvements on the ground, including greater public consultation with people affected by such

projects; better monitoring of the environmental and social aspects of projects; and

improvements in resettlement policy and practice. The Government has also ensured that the

methodology used by Central power agencies to select sites has improved, as has the capacity of

various hydropower developing agencies to deal with complexities in project identification,

engineering and design.

World Bank assistance

The Government of India has requested World Bank support for its plans to increase the

country’s hydropower capacity. It has also requested Bank assistance to help its power sector

agencies build on their recent achievements with the aim of attaining international standards in

hydropower design, construction and operation.

The World Bank aims to assist the Government of India in meeting its targets for

hydropower expansion in a sustainable manner. This entails not just ensuring financial,

economical, and technical soundness but also meeting social practices which have been

developed by the industry in recent years, and safeguarding environmental assets for future

generations.

The Bank has been engaged in hydropower in India since the late 1950s. Several of its

past engagements have been difficult, with Bank support for a number of potential hydropower

projects, including the Sardar Sarovar project on the river Narmada, being cancelled before they

were commissioned. The two most recent Bank engagements, the Nathpa Jhakri and Koyna IV

projects which were completed in 2002 and 1998 respectively, have benefited from the lessons

of earlier hydropower development, including more socially and environmentally sensitive

safeguard policies.

Proposed hydropower projects in India

At the request of the Government of India, the World Bank is evaluating two hydropower

projects in the country -- the Rampur Hydropower Project downstream from Nathpa Jhakri on

the River Satluj in Himachal Pradesh and the Projection the River Alaknanda in Uttarakhand.

While the Rampur Project is in the project appraisal stage, the Vishnugad-Pipalkoti project is in

the early stages of preparation.

The World Bank is also assisting the state governments of Himachal Pradesh and

Uttarakhand adopt a river-basin approach in the planning and development of cascaded

hydropower systems. The two mountain states that have made hydropower generation a

significant development priority, have asked for Bank assistance in initiating a River Basin

Development Optimization Study that uses the Satluj and Alaknanda rivers as case studies. The

Study aims also at forging effective and equitable systems of cost-and benefit-sharing among all

stakeholders, including developers and operators, affected local communities, and host states.

Types of Hydroelectric Plants:

Classification according to functional basis:

According to functional basis hydroelectric plants may be classified as

(i) Base-load plants and (ii) Peak-load plants.

(i) Base-load plants.

Base-load plants are those which are capable of substantially continuous operation in the base of the load curve throughout the year. Both run-of-river plants as well as storage plants can be used as base-load plants. When run-of-river plants without pondage are used as base load plants, their full plant discharge is seldom more than the minimum flow of river.

(ii) Peak-load plants.

A peak-load plant is one designed and constructed primarily for taking care of the peak-load of a power system. Pumped-storage plants are peak-load plants. Run-of-river plants with pondage can operate both as peak-load and base-load plants as river flow permits.

Classification on the basis of head

On the basis of head hydroelectric plants may be classified as (i) Low head plants, (ii) Medium head plants, and (iii) High head plants.

(i) Low head plants.

A low head plant is the one which is operating under a head less than about 30 m. Run-of-river plants are usually low head plants. For low head plants generally axial flow turbines such as Kaplan turbines are used.

(ii) Medium head plants.

A medium head plant is the one which is operating under a head between 30 and 250 m. The lower ranges of medium head may be made available by utilizing a steep slope or a fall in a river or a channel where run-of-river plants may be provided. However, the higher ranges of medium head may be obtained by constructing dams and hence these are storage plants. Again for lower ranges of heads for these plants axial flow turbines may be used. But for higher ranges of head for these plants usually mixed flow turbines such as Francis turbines are used.

(iii) High head plants.

A high head plant is the one which is operating under a head more than 250m. These heads may be obtained by constructing dams of sufficient height and installing the power plant either at the toe of the dam close to it or in a deep depression available at some distance away from the dam. Thus these are invariably storage plants. For these plants usually impulse turbines such as Pelton wheel turbines are used.

It may however be stated that the above noted head ranges for the different types of hydroelectric plants are arbitrary. Moreover, with the advances in the turbine design it has become possible to use axial and mixed flow turbines for higher heads. Consequently the ranges of head indicated above also move up.

Classification on the basis of plant capacity

On the basis of plant capacity the hydroelectric plants may be classified as (i) Micro hydel plants, (ii) Medium capacity plants, (iii) High capacity plants, and

(iv) Super plants.

(i) Micro hydel plants. A micro hydel plant is the one which has a capacity less than 5 MW.

(ii) Medium capacity plants. A medium capacity plant is the one which has a capacity in the range 5 to 100 MW.

(iii) High capacity plants. A high capacity plant is one which has a capacity in the range of 101 to 1000 MW.

(iv) Super plants. A super plant is the one which has a capacity more than 1000 MW.

Firm (or Primary) Power and Secondary (or Surplus) Power

Firm (or primary) power is the power which a plant can deliver throughout the year or 100 percent of time. Secondary (or surplus) power is the power in excess of firm power which a plant can deliver only for a part of the year or for some percentage of time. Thus for a run-of-river plant without any storage the firm power would correspond to the minimum flow of the river which would be available throughout the year. However, by providing the storage the firm power can be considerably increased. Similarly, by having one or more thermal plants which can be utilized to generate extra power when hydroelectric generation is low, a part of the secondary power can be converted into firm power.

Load factor, Utilization factor and Capacity factor

Load factor is defined as the ratio of the average load during a certain period to the peak or maximum load during that period. The load factor is thus related to a certain period and therefore these are expressed as daily load factor, weekly load factor, monthly load factor and yearly load factor.

The load factor of a power plant would vary greatly with the character of the load. The load factor for a power plant serving a highly industrialized area may be as high as 80%, but in residential areas me i factor may be as low as 25 to 30%.

Utilization factor (or Plant-use factor) is defined as the ratio of the peak load developed during a certain period to the installed capacity of the plant. It thus represents the maximum proportion of the installed capacity utilized during any period. In the case of a hydroelectric plant, with constant head, utilization factor would also be the ratio of water actually utilized for generating maximum power corresponding to peak load to that available in the river, and usually there will be little difference in this factor whether expressed as a ratio of power or water. For a hydroelectric plant, utilization factor commonly varies from about 0.40 to 0.90, depending on plant capacity, load factor, available pondage and storage etc.

Capacity factor (or plant factor) may be defined as the ratio of the energy that the plant actually produces during any period to the energy that it might have produced if operated at full capacity throughout this period.

Capacity factor will be identical with load factor when the maximum or peak load just equals the plant capacity. For a hydroelectric plant, capacity factor commonly varies from about 0.25 to 0.70 or more depending on load factor, plant capacity, available pondage and storage etc.

The thermal plants may be operated at any desired capacity factor, whereas the capacity factor at which hydropower plants may operate is usually limited by the variation in the flow of water in the river. Theoretically a thermal power plant might operate at 100% annual capacity factor, but practically because of the necessity for an annual maintenance period the maximum annual capacity factor is much lower and usually it does not exceed 80%. Moreover there is always a decline in the annual capacity factor of thermal power plants with their age.

General arrangement of a hydroelectric project:

A hydroelectric development ordinarily includes a diversion structure (dam, weir or barrage), a conduit (penstock) or a channel (or canal) to carry water to the turbines, turbines and governing mechanism, generators, control and switching apparatus, housing for the equipment, transformers, and transmission lines to the distribution centers. In addition, trash racks at entrance to the conduit, channel and penstock gates, a forebay, surge tank and other appurtenances may be required. A tailrace, or waterway, from the powerhouse back to the river has to be provided if the powerhouse is situated so that the water after flowing through the turbines is not discharged directly into the river. It may however be stated that no two power developments are exactly alike and each will have its own unique problem of design and construction. The type of plant best suited to a given site depends on several factors, including head, available flow and general topography of the area.

In general hydroelectric developments may be classified as (i) Concentrated-fall development, and (ii) Divided fall development.

A concentrated-fall hydroelectric development the one in which the power house is located close to the dam on the downstream side. The powerhouse may be located at one or both ends of the dam

In a divided fall hydroelectric development the powerhouse is located at a considerable distance away from the dam and water is carried to the power house through a canal, tunnel or penstock. This type of development is adopted to utilize a steep fall in the ground surface which might be available at some distance away from the dam. Thus in this case with favorable topography it is

possible to achieve a high head even with a low dam. Moreover, with this arrangement, head variations in the reservoir may be small as compared with the total head, and the turbine can operate near optimum head (peak efficiency) at all times.

Components of hydroelectric development

The various components of hydroelectric developments are described below.

Diversion Structures: The diversion structures commonly used are dams, weirs and barrages. A diversion structure is constructed across a river at suitable site to develop storage of water and to create head for the generation of power. In order to control the supply of water from the storage certain gates and valves are used. The different types of gates used are plain sliding gates, wheeled or roller gates, etc. Similarly the common types of valves used are butterfly and needle valves.

Waterway:

A waterway is passage through which water is carried from the storage reservoir to the power house. It may consist of tunnel, channel (or canal) or penstock. If a hill intervenes the reservoir

and the power house, then a tunnel may be driven to provide the necessary waterway. The tunnel may be circular or horse-shoe shaped, lined or unlined, lined with concrete or reinforced concrete or steel depending on the nature of the rock through which it is driven. It may flow full as a pressure conduit or partly full as a channel.

Water may be conveyed from the reservoir to the turbines through penstocks or through a channel (called power channel or power canal) followed by penstocks. In the later case at the end of the channel a forebay is provided from which water is conveyed to the turbines through the penstocks.

Penstocks:

Penstocks are the pipes of large diameter used for conveying water from the reservoir to the turbines. These are usually made of steel. However, reinforced concrete, cast iron and wooden penstocks are also used for low heads and relatively small developments. The thickness of the penstock is determined on the basis of the magnitude of stresses developed due to static pressures as well as water hammer pressures which may be developed due to sudden reduction in the flow caused by the governor when the load is suddenly reduced. Long penstocks are usually

provided with a surge tank to absorb water hammer pressures and to provide water to meet sudden load increases.

A penstock is usually supported on piers, but when it is laid along slopes or encounters change in alignment, it should be supported on anchor blocks. As far as possible sharp bends in a penstock should be avoided because of the head loss and the large forces required to anchor the penstock. Air valves are provided at the sections of the penstocks where there are steep changes in the gradient.

In the case of long steel penstocks, expansion joints should be provided to take care of expansion and contraction due to changes in temperature. Long penstocks are usually branched at the lower end to se several turbines. However, in the case of short penstocks, separate penstocks ordinarily used for each turbine.

Penstocks are usually provided with head gates which can be closed to permit repair of the penstock. An air-inlet valve and air duct connecting the penstock with the open air, should be provided immediately on the downstream of the gate. The air-inlet valve permits air to enter the penstock when the head gate is closed and the turbine gate is open, and thus prevent collapsing of the penstock which may occur due to sudden drainage of the penstock. A sufficient water depth should be provided above the penstock entrance to avoid formation of vortices which may carry air into the penstock and result in lowered turbine efficiency and undesirable pressure surges. This problem may more commonly arise in the case of penstocks taking off from the forebays. The entrance to the penstock should be properly designed to minimize the loss of head.

Forebay:

A forebay is an enlarged body of water provided just in front of the penstocks. It is provided in the case of run-of-river plants and in the case of storage plants when the power house is located at a certain distance away from the dam and water is carried from the reservoir to the power house through a channel. However, if the power house is located close to the dam then since the penstocks directly take water from the reservoir, the reservoir itself will act as forebay. The main function of the forebay is to provide a small balancing storage upstream of the power house to store temporarily the water rejected by the plant when the load is reduced and to provide water to meet the instantaneous increased demand on account of increased load while the flow in the channel is being accelerated. The forebay may be developed by enlarging the channel just upstream of the intake for the penstocks leading water to the turbines in the power house. The forebay must be provided with a spillway or wasteway, so that excess water can be disposed of safely if the need arises.

Intake Structures: The

water from the reservoir or forebay is let into the penstocks through intake structure. The main components of an intake structure are trash racks and gates. The trash rack is provided to prevent the entry of debris into the water passage of the hydropower plant which may otherwise damage the wicket gates and turbine runners, or choke up the nozzle of impulse turbines. A debris cleaning device is usually fitted on the trash rack. Further if ice may get deposited on the trash rack, a heating element or some other ice removing equipment is also provided. The trash racks are provided ahead of the gates. The gates along with their hoisting arrangements are provided to control the entry of water into the penstocks.

Surge Tanks:

A surge tank is a cylindrical open-topped storage tank which is connected to the penstock at a suitable point. Surge tanks are provided in the case of hydroelectric developments having long penstocks. These are provided to relieve the penstocks of excess pressure caused by water hammer and to provide additional supply of water when the turbines are in need of more water on account of increased load. A surge tank however, provides protection against water hammer pressure for only that portion of the penstock which lies on the upstream of it. As such surge tank should be provided as close to the power house as is possible according to the site conditions.

When the load on the turbine is steady and normal, a constant water surface will be maintained in the surge tank, which will be lower than the reservoir surface by an amount equal to the friction head loss in the portion of the penstock connecting the reservoir and the surge tank. When the load on the generator is reduced, turbine gates are closed by the governor to reduce the flow through the turbine and the water moving towards the turbine has to move backwards. The rejected water is then stored in the surge tank and water level in the surge tank rises. The retarding head so built up in the surge tank reduces the velocity of flow in the pipeline corresponding to the reduced discharge required by the turbine. When the load on the generator increases, the governor opens the turbine gates to increase the rate of flow entering the runner. The increased demand of water by the turbine is partly met by the water stored in the surge tank. As such the water level in the surge tank falls. In other words, the surge tank develops an accelerating head which increases the velocity of flow in the penstock to a value corresponding increased discharge required by the turbine.

In general the surge tanks may be classified as (i) Simple surge tanks and (ii) Differential surge tanks.

A simple surge tank is a cylindrical open-topped tank connected to the penstock through a central vertical riser pipe or an orifice. A differential surge tank is also a cylindrical open-topped tank connected to the penstock through a central vertical riser pipe but in this case the riser pipe extends vertically into the tank upto considerable height and at the lower end of the riser pipe within the tank small ports or holes are provided. The main advantage of a differential surge tank is that for the same stabilizing effect its capacity may be less than that of a simple surge tank. This is so because in a differential surge tank retarding and accelerating heads are developed more promptly than in a simple surge tank in which the heads only built up gradually as the tank fills.

The surge tanks must be high enough so that there is no spilling of water from the tank even with a full load change. This would, however, require a very high surge tank involving large cost if it is provided close to the power house. As such in order to reduce the height and hence the cost of the surge tank, it is generally provided at a point where the ground surface has a steep fall and the penstock drops rapidly to the power house. The height of a simple surge tank may also be reduced by providing an internal bellmouth spillway (with its crest upto the desired maximum water level in the tank) which permits the overflow of water from the tank and the same can be conveniently disposed of. However, the main drawback of this arrangement is that considerable amount of water is allowed to be wasted.

Power house:

The power house of a hydroelectric development houses the various hydraulic and electric equipments. The various hydraulic equipments are turbines, gates or gate valves, governors etc. The various electrical equipments include generators, transformers, switching equipment, transmission lines and transmission structures, auxiliary electrical equipments etc.

The power house consists of two main parts, a substructure to support the hydraulic and electrical equipment and a superstructure to house and protect this equipment. The generating units are always placed in a row at right angles to the direction of flow through the power house.

An important feature of the superstructure is a travelling crane, spanning the width of the power

house and of sufficient capacity to lift the heaviest single piece of equipment. This crane is needed to remove and carry turbine, generator or other equipment for servicing repairs or replacement. A switch yard for the transmission of power is usually located outdoors near the power house.

Tailrace:

The tailrace is the channel into which the water is discharged after passing through the turbines. If the power house is close to the stream, the outflow may be discharged directly into the stream. On the other hand if the power house is located away from the stream the tailrace is formed by constructing an artificial channel between the power house and the stream.

Selection of suitable types of turbines:

The most commonly used turbines are Francis turbines, Kaplan turbines and Pelton wheel turbines. In addition to these three types of turbines, the other types of turbines which are also used though not very commonly are Deriaz (or Diagonal) turbines and Tubular turbines. The selection of a suitable type of turbines is usually governed by the following factors:

(i) Head and Specific Speed: It has been found that there is a range of head and specific speed for which each type of turbine is most suitable. However, as a general rule, it may be stated that as far as possible a turbine with highest permissible specific speed should be chosen which will not only be cheapest in itself but its relatively small size and high rotational speed will reduce the size of the generator as well as power house. But the specific speed cannot be increased indefinitely because higher specific speed turbine is generally more liable to cavitations. However, the cavitations may be avoided by installing the turbine at a lower level with respect to the tail race.

(ii) Part Load Operation:

The turbines may be required to work with considerable load variations. As the load deviates from the normal working load, the efficiency would also vary. At part load the performance of Kaplan and Pelton turbines is better in comparison to that of Francis and Propeller turbines. The variability of load will influence the choice of type of turbine if the head lies between 150 m to 300 m or lies below 30 m. For higher range of heads Pelton wheel is preferable for part load operation in comparison to Francis turbine, though the former involves higher initial cost. For heads below 30 m, Kaplan turbine is preferable for part load operation in comparison to Propeller turbine.

Type of Hydroelectric Plants:

1. Classification based on Storage Characteristics

Run-of-river plants Storage or Reservoir plants Pumped-Storage plants Tidal Plants

2. Classification according to functional basis

Base-load plants Peak-load plants

3. Classification on the basis of head

Low head plants Medium head plants High head plants

4. Classification on the basis of plant capacity

Micro hydel plants Medium capacity plants High capacity plants Super plants

Component of hydroelectric project:

1. Intake arrangement

Dam Storage reservoir Diversion structure or spill way De-silting basin Trash rack Gates

2. Water conductor system

Power channel / Duct Tunnel Surge shaft / Surge tank Drop shaft Pressure shaft Penstock with penstock protection valve ( Butterfly valve )

5. Power house

a.) Mechanical Component

Distributer / Spiral casing Spherical valve or Main inlet valve Turbine EOT Crane

b.) Electrical component Generator Transformer Switchyard Transmission line

c.) Power house auxiliaries

Cooling water system Compressed air system De-watering system Drainage system Air conditioning system Control & monitoring system Fire protection system

Different type of Dam:

1. Classification Based on Function:

Storage Dam or Impounding Dam Detention Dam Diversion Dam Coffer Dam Debris Dam

2. Classification Based on Hydraulic Design

Overflow Dam Non-overflow Dam

3. Classification Based on Material of Construction

Rigid Dam Non-rigid Dam

4. Classification Based on Structural Behaviour

Gravity Dam Arch Dam Buttress Dam Embankment Dam

5. Classification Based on Size

Small

Intermediate Large

Reservoir :

During extremely low flows it may not be possible to meet the demands of the consumers

if water is drawn directly from a river. As such it is essential to create a reservoir or an artificial

lake by constructing a dam across the river which can retain the excess water from periods of

high flows for use during the periods of low flows or droughts. In addition to conserving water

for later use, the storage of floodwater may also reduce flood damage on the downstream of the

reservoir.

Spillway :

A spillway is a waterway provided to dispose of surplus flood waters from a reservoir

after it has been filled to its maximum capacity. Spillways are invariably provided for all the

dams and this act as safety valves for the dams. It may be located either within the body of the

dam or at one end of the dam or entirely away from the dam as an independent structure. It is

essential to provide a spillway of sufficient capacity (or outflow rate through the spillway) so

that the surplus flood water is discharged keeping the water level in the reservoir below some

predetermined maximum level and no damage is caused to the dam.

Spillways crest gates :

By installing gates over the crest of the spillway additional storage can be made

available. Gates can be provided on all types of spillways except siphon spillways for which

gates are not required because the rise of water level during floods is small as compared to other

spillways. For an non-gated spillway the useful storage in the reservoir can be maintained only

up to the level of the crest of the spillway.

Earthen dam

An embankment dam is a massive artificial water barrier. It is typically created by the

emplacement and compaction of a complex semi-plastic mound of various compositions of soil,

sand, clay and/or rock. It has a semi-permanent waterproof natural covering for its surface, and a

dense, waterproof core. This makes such a dam impervious to surface or seepage erosion. The

force of the impoundment creates a downward thrust upon the mass of the dam, greatly

increasing the weight of the dam on its foundation. This added force effectively seals and makes

waterproof the underlying foundation of the dam, at the interface between the dam and its stream

bed. Such a dam is composed of fragmented independent material particles. The friction and

interaction of particles binds the particles together into a stable mass rather than the use of a

cementing substance. They are of two types:

Earth-fill dam Rock-fill dam

Earth-fill dams, also called earthen, rolled-earth or simply earth dams, are constructed as

a simple embankment of well compacted earth. A homogeneous rolled-earth dam is entirely

constructed of one type of material but may contain a drain layer to collect seep water. A zoned-

earth dam has distinct parts or zones of dissimilar material, typically a locally plentiful shell with

a watertight clay core. Modern zoned-earth embankments employ filter and drain zones to collect

and remove seep water and preserve the integrity of the downstream shell zone. An outdated

method of zoned earth dam construction utilized a hydraulic fill to produce a watertight

core. Rolled-earth dams may also employ a watertight facing or core in the manner of a rock-fill

dam. An interesting type of temporary earth dam occasionally used in high latitudes is

the frozen-core dam, in which a coolant is circulated through pipes inside the dam to maintain a

watertight region of permafrost within it.

Rock-fill dams are embankments of compacted free-draining granular earth with an

impervious zone. The earth utilized often contains a large percentage of large particles hence the

term rock-fill. The impervious zone may be on the upstream face and made of masonry, concrete,

plastic membrane, steel sheet piles, timber or other material. The impervious zone may also be

within the embankment in which case it is referred to as a core. In the instances where clay is

utilized as the impervious material the dam is referred to as a composite dam. To prevent internal

erosion of clay into the rock fill due to seepage forces, the core is separated using a filter. Filters

are specifically graded soil designed to prevent the migration of fine grain soil particles. When

suitable material is at hand, transportation is minimized leading to cost savings during

construction. Rock-fill dams are resistant to damage from earthquakes. However, inadequate

quality control during construction can lead to poor compaction and sand in the embankment

which can lead to liquefaction of the rock-fill during an earthquake. Liquefaction potential can

be reduced by keeping susceptible material from being saturated, and by providing adequate

compaction during construction

Activities & equipments involved in embankment dam construction

1>Site clearance: site clearance involved cleaning & clearing o fland, grabbing, the plants &

trees.

Equipments: dozer, ripper, hoe, scrapper, wood-cutter.

2>Excavation : excavation means it is cutting the heaped part & filling extra earth in pits.

Equipments :

Excavation : bulldozer, scraper, reaper, scraper, hoe, power shovel, clamshell, dragline.

Hauling : trucks, tractors, scrape.

3>Compaction & leveling :It is the placing the different gravels, boulder & fine soil layers in

layers with stabilizing, & curing till the optimum moisture content is achieved.

Equipment :

Placing: shovels, hoe, loader.

Vibrating : vibrators, self vibrating plats and manually propelled compactors, rollers.

4>Sheet piling : sheet piling is piling in upstream side, centre and downside to minimize the

underground seepage flow. It is done by excavation, stabilization, drilling.

Equipments:

Drilling : auger drill, pneumatic drills.

Concrete Dam:

Concrete dams are built in four basic shapes. The concrete gravity dam has weight as its

strength. A cross section of this dam looks like a triangle, and the wide base is about three-

fourths of the height of the dam. Water in the reservoir upstream of the dam pushes horizontally

against the dam, and the weight of the gravity dam pushes downward to counteract the water

pressure. The concrete buttress dam also uses its weight to resist the water force. However, it is

narrower and has buttresses at the base or toe of the dam on the downstream side. These

buttresses may be narrow walls extending out from the face of the dam, much like the "flying

buttresses" supporting cathedral walls or a single buttress rather like a short dam may be built

along the width of the toe of the dam.

Gravity Dam Arch Dam

In a gravity dam, stability is secured by making it of such a size and shape that it will

resist overturning, sliding and crushing at the toe. The dam will not overturn provided that

the moment around the turning point, caused by the water pressure is smaller than the moment

caused by the weight of the dam. This is the case if the resultant force of water pressure and

weight falls within the base of the dam. However, in order to prevent tensile stress at the

upstream face and excessive compressive stress at the downstream face, the dam cross section is

usually designed so that the resultant falls within the middle at all elevations of the cross section

(the core). For this type of dam, impervious foundations with high bearing strength are essential.

In the arch dam, stability is obtained by a combination of arch and gravity action. If the

upstream face is vertical the entire weight of the dam must be carried to the foundation by

gravity, while the distribution of the normal hydrostatic pressure between vertical cantilever and

arch action will depend upon the stiffness of the dam in a vertical and horizontal direction. When

the upstream face is sloped the distribution is more complicated. The normal component of the

weight of the arch ring may be taken by the arch action, while the normal hydrostatic pressure

will be distributed as described above. For this type of dam, firm reliable supports at the

abutments (either buttress or canyon side wall) are more important. The most desirable place for

an arch dam is a narrow canyon with steep side walls composed of sound rock. The safety of an

arch dam is dependent on the strength of the side wall abutments, hence not only should the arch

be well seated on the side walls but also the character of the rock should be carefully inspected.

Different Construction Activities:

1. Site Clearing

2. Excavation

3. Moving & Hauling

4. Piling work

5. Dewatering

6. Frame work

7. Concreting

8. Grouting

9. Drilling

10. Placing

11. Breaking work

12. Compaction & Leveling

13. Surface treatment

Activities & equipments involved in embankment dam construction

1. Site Clearing

2. Excavation

3. Moving & Hauling

4. Piling work

This above activities detail is mention in Earthen Dam section.

5. Dewatering: Removing water from the duck or Excavated area.

Equipment used:

Reciprocating pump Centrifugal pump

6. Concrete work:

Equipment used:

(a) Mixers :

Tilting mixer No tilting mixer Rotary mixer. Transit mixer

(b) Transportation of concrete

Metal pans Buggies-either hand operated or power operated Belt conveyer system Buckets handled with cranes Pump & pump lines

Pneumatic concrete placer

(c) Vibrators :

Needle vibrator Platform vibrator

7. Grouting : Grouting work is used for filling the void in concrete Equipment : Grouting pump.

8. Breaking work:Equipment used:

Hydraulic Rock Breaker Hydraulic Hammer Stone Crushing Machine

9. Compaction & LevelingThis above activity detail is mention in Earthen Dam section.

Planning and selection of equipments:

Modern construction industry is of a complex work. Projects are big and complicated in nature. There may be more than one sites has to be handled at same time. In modern era planning takes most important thing prior to commencement of work by which one will decide what work to be done, how to do, sequence of work, how to optimize the time and cost of project, how an equipment can be optimistically used in the construction. With increase in the scope, complexity and nature of work, every single work is executed by different equipments.

The selection of the equipment is also of upmost priority of work is important. Before start of execution nature of work should be properly defined by checking, inspecting and testing job site. Equipments are very costly, so they have to be selected by a specialist person. Equipments are also very typical to handle, maintain and repair. They need specialized person for driving, who must be training. Nature of work affects the selection procedure. Use of equipment offers certain advantages such as:

Tough work which is beyond the scope of manual labour can be performed effectively and efficiently.

At the time when human labour is uncertain, machines are the only alternative, further these equipments are not affected by social and economic condition of the region.

Due to us of machine, proper planning of work can be made, which consequently reduces the overall cost of the project.

For huge work or when large quantities of material to be transported from one to other, use of equipment is always cheaper.

Equipment help in rapid industrialization of the country.

Roll of IT in the development of equipment will make work easier and with automation it will decrease labors on the site.

Drawbacks:

It creates unemployment problems to human labour as well as to the national economy. Equipments are required to be maintained properly. If they are under repair, work

progress stops completely. Hence it is essential to have stand byes may increase the total cost of project.

It may require the investigation which may not be easy for all the contractors. If it is to be imported, valuable foreign exchange disturbes the balance of the foreign

trade. It is problem to transport heavy equipment to job site. Construction equipments are more power consumptive than any other. Some times for unique site equipments are established specifically.

Factors of deciding the type of equipment:

Nature and magnitude of work. For heavy lifting and transporting of materials and machineries. Cost of equipment Job site conditions like, climate, place, geography, type material to handle. External or internal power supply. Fuel requirement and power consumption for work. Quality, work precision and duration of work

There are following aspects to be considered at selection stage;

Suitability for job with specific reference to climatic and other conditions. Size of equipment Standardization and variety reduction Type of prime mover Degree of utilization Suitability of local condition Adaptability Technical considerations

The of size of equipment is indicated as either minimum number of large size of machines or more no of small/ medium sized machines. A main advantage of selection of large size of equipment is that they are generally sturdy and tuned to tough working conditions. The size of standby equipment will also be a consideration in selection of equipments. As far as possible multiple uses of units is preferred first. Basic units of equipment comprises of prime mover and hydraulic system are available with wide variety of attachments to perform a a variety of functions.

Persons who are involved in construction industry always prefer to purchase standard equipment for following reasons.

Less initial investment and more reliability Can be held from market easily with short notice period. Easy to repair and dispose off More resale value Can be used many times for similar nature of works

In general special equipments are defined as equipment manufactured for a single construction project or for a specific job. Special equipments are purchase after doing the deeper analysis. As it requires high initial investment and has restricted usage, A factor that must be considered while purchasing an equipment is easy and with which replacement parts can be obtained easily.

Technical consideration includes the following points:

Strength Variable stability Resistance to wear Heat resistance Reliability Maintainability Planning for construction equipment

A type of equipment selected depends on the type of work, amount of work, site condition and type of work to be handled. The number and size of equipment depend on amount of work, working days available, shift of work, and availability of labour.

Along with planning of selection of equipment, planning of equipment operations, its relation with other jobs under execution etc. should be done properly. If proper planning of operation of equipment and surrounding equipment is not done properly, availability of equipment will be less and its use will be less. Either equipment will remain idle or work is not taken from equipment of its capacity. Arrangement must be made for its repairs and maintenance. Topographical condition where it would be placed should be considered while selection of equipment and planning execution, operation of equipment.

Factors affecting the selection of equipments

Downtime cost

Downtime cost is that cost that machine is not under working. it happens when machine is under repairing, or adjustments. It increases with usage. Hence, due to productivity of machine decrease and production cost per unit increases. The loss of money is because machine is not under usage due to downtime that’s why it is called downtime cost.

Obsolescence cost

Due to continuous improvement of machines, the production cost per unit of new machine decreases. The advantage can be gained only by replacing the old equipments by new improved one. But it is tendency to use older one with continuous repairs till it becomes useless.

Hence a person who has gained this older equipment sustains loss in thh form decrease in the profit is called obsolescence cost. Failure to take advantage of new equipment results in higher than necessary production cost for the owner of old equipment. The production cost for equipments is reducing by approximate 3 to 5 percent due to improvement of machineries.

Depreciation

Every asset has got useful life whether fixed or movable has got certain useful life. Its book value goes on decreasing with time. This decrease in value of asset with use or age or obsolescence is defined as depreciation. Due to continued decline in value of properties of assets their cost must be amortized over useful and economical life so that owner can recover his investment, if and when need be and has the capital available when replacement of the asset or property becomes necessary. Because property value generally decreases in value, it is desirable to consider the effect of depreciation on the project cost.

Cycle time

It is the time taken by machine to complete one full cycle of operation. It consists of fixed value and variable time. Variable time is the time spent on travelling hence is function of travelling distance, time spent, and speed of equipment other than travelling like loading, unloading, turning, dumping. It is of ideal requirement that equipment work for an hour means 60 minutes but it seldom works for 50 minutes. In case of night It works for about 45 minutes per hour.

Economic and useful life of equipment

The owner of equipment is always interested to keep production time minimum. The period through which the equipment gives maximum profit is called as economic life of an equipment. Useful life of equipment is its life in years to which it can be used economically. Hence, many of times economic life of equipment is called as a useful life. But in real in economic life periods profit will be maximum. Economic life is always less than the useful life. Factors which affect the economic and useful life are:

Depreciation and replacement Amount invested in equipment Maintenance and site conditions Downtime and obsolescence time

It is always necessary to replace used equipment at end of its useful life. The cost of maintenance and repairs generally increase in geometric proportion with increase in age of an

equipment. Apart from pure economic consideration, replacement it is also required due to obsolescence cost, non availability of spare-parts, etc.

Productivity of equipment

The manufacturer generally provides the information regarding productivity, rating of an equipment under different conditions. On site it is prudent that output is always less than the quoted rating by manufacturer. In general utilization factors remains from 0.6 to 0.8, depends on quality of work and conditions at site. It is always advisable by a good planner to compare the scope and quantity work completion with different no. and sizes of equipments for same quantity of work and then to select equipment.

CLASSIFICATION

Machines and mechanisms used in construction can be classed in respect to the kind of job, nature of working process, the operation conditions, the type of drive, the capacity (output), the type of running gear, universality and the kind of control.

Equipments are used on almost all the project in one form or the other.

Equipments are classified as shown below:

1. Hauling Equipments

(a) Tractors

Crawler mounted Wheel mounted

(b) Trucks

(c) Dumpers.

2. Earth moving machines

(a) Bulldozers and Anglodozer

Crawler mounted Wheel mounted Tractor mounted

(b) Rippers

Crawler mounted Wheel mounted Tractor mounted Scrappers

(c) Scrapers

Crawler tractor mounted Wheel tractor mounted.

3. Hoisting equipments

a) Chain hoist or Jib hoistb) Chain-pulley blockc) Jacksd) Winch hoiste) Cranes

Dorric crane Mobile crane Tower crane Hydraulic crane Gantry crane Lift crane.

4. Excavating and Hauling equipment

(a) Power shovel

Wheel mounted Crawler mounted Tractor mounted

(b) Hoe or drag shovel

(c) Clamshells

(d) Draglines

(e) Dredgers

Dipper dredger Ladder dredger Suction dredger

5. Earth compactors

a) Tamping rollersb) Smooth wheel rollersc) Pneumatic tyred rollersd) Vibrating rollers

e) Self propelled vibrating plat, and/or shoesf) Manually propelled vibrating plates g) Manually propelled compactors

6. Pneumatic equipments—Air compressors :

Stationary Compressor Portable compressor Reciprocating compressor Rotary compressor Centrifugal compressor Axial flow compressor

7. Conveying equipments

a) Belt conveyer systemb) Pneumatic conveyor c) Ropeways

8. Rock drilling equipment

Jack hammer Drifter Wagon drills Track mounted drills Percussion drills Rotary percussion drills Blast hole drills Diamond drills

9. Blasting equipments

10. Pumping and Dewatering equipments

(a) Reciprocating pump

(b) Centrifugal pump

11. Pile driving equipments hammers

Steam hammer Hydraulic hammer Diesel hammer Single-acting hammer Double-acting hammer Differential acting hammer

12. Crusher

(a) Primary crushers

Jaw crusher Gyratory crusher Hammer mill crusher

(b) Secondary crushers

Cone crusher Roll crushers Hammer mill crusher Tertiary crusher Roll crushers Rod mill crusher Ball mill crusher

13. Concrete mixing plants

(a) Concrete mixing batchers

(b) Mixers :

Tilting mixer No tilting mixer Rotary mixer. Transit mixer

(c) Transportation of concrete

Metal pans Buggies-either hand operated or power operated

Belt conveyer system Buckets handled with cranes Pump & pump lines Pneumatic concrete placer

(d) Vibrators :

Needle vibrator Platform vibrator.

14. Miscellaneous equipments

a) Welding equipments b) Grouting equipments c) Tar mixing equipments

15. Special Tunneling equipments

Drilling jumbo Explosives Ventilating fans and ducts Temporary supports Mucking equipment Rock loaders Concreting gantry Machine tunneling

Other Methods of Classification

With respect to the degree of mobility (universality), machines are classified as stationary and mobile, the later, depending on the manner of gauging up, may be of the self propelled, semi trailer and trailer types. As to the type of the running gear, machines may be crawler, pneumatic tyre, rail mounted, and walking.

With respect to the system of control, hand operated and automatic machines are distinguished and with respect to the means of control, they are classified as mechanically controlled, hydraulically controlled, pneumatic controlled and electrically controlled machines, borne machines have combined control for example hydro-mechanically controlled machines.

General purpose self-propelled vehicles find an even widening field of application. These usually consist of a base vehicle and a set of change mounted or semi-trailed and sometimes trailed working equipment. Tractors, trucks are used as a base vehicle.

The design and performance features of machines are evaluated by their basic parameters, including the power rating, horse power, bucket capacity for excavator and scrapper, blade size for a bulldozer, drilling diameter etc.

The requirements imposed on machines include social, design, usage and economy.

A class of machine is subdivided into groups according to the nature of working process involved. For instance earth work machines are divided into excavation machines (excavators) and earth moving machines.

With respect to duty, machines of various groups are classed as intermittent (cyclic) action (for instance, single bucket excavators) and continuous action machines (for instance multi bucket excavators).

Machines of all types must be available in a number of standard size, differing from one another in the power rating of the drive, in mass, size of working members, over all dimensions,

but being at the same time of almost similar design.

With respect to the main drive, machines are distinguished as powered by an electric motor, an internal combustion engine, by pneumatic and hydraulic motors, or as a combination of two, a diesel electric.

1>HAULING EQUIPMENTS

To Haul means to carry, hence an equipment used to carry, materials from one place to other is called an hauling equipment. Their function is simply to transfer. Tractors, dumpers and trucks are used to haul the material.

A tractor is a multipurpose machine varies from light models used small haulage and agricultural works to heavy crawler units for large and heavy works. It is one of the most important equipment and is indispensable on most of the projects whether small or big.

The primary function of a tractor is to pull or push loads but they are also used to mount other equipments also such as shovels, rippers, bulldozer blades, hoes etc. These tractors may be (i) Crawler mounted or (ii) Wheel mounted.

If a tractor is mounted on crawler it is called crawler mounted tractor and if rubber tyres have been used it is called wheel mounted. These tyres are called pneumatic tyres.

from one place to other. These because of high speed and more capacities provide relatively low hauling cost. Trucks may be classified as four wheel or six wheels, gasoline engine or diesel engine 3 gears or 4 gears, capacity in term of weight or in volume etc. Hence trucks should be selected as per works to be carried with them.

These equipments have got life of 8 to 10 years(9000 to 16000 hrs.) depending on it’s horsepower varies from 100HP to 300HP. Wheeled tractors have been developed at speed more than 50kmph.

Crawler type tractors

Crawler types are tractors are developed for heavier jobs at site, or where the location of job site in undulating land or at territorial areas. They are more costlier than wheeled type tractors. Operation and maintenance of crawler type tractors are more & it requires the skilled operators. Crawler type tractors are mostly used in the soft grounds and slop surfaces.

Trucks

Trucks are used on sites for transportation of materials like cement, aggregate, coal, steel, earth, sand or other machineries. They have high speed than tractors. Trucks are generally on the long distance material transportation.

Specifications.

Capacities — 0.4 m3 to 20 m3

Speed = 10 to 50 kmph (max. 100 kmph)

Carrying capacity

light trucks — 1/2 to 1 Tons (0.5 KN to KN)

Medium — 1.5 to 3 Tons. (15 KN to 30 KN)

Heavy — 3.5 to 10 Tons. (35 KN to 100 KN)

Common trucks are 4 x 2 wheel i.e. 2 front or driving wheel and 4 rear wheel.

Many times to main body of trucks, service trailers of huge size are attached. Trailers of 13 m length having 16 tyres are usual. Even trailers having 40 wheels for transportation of heavy equipment have been manufactured by various firms as shown.

Dumper

Dumper is a heavy duty truck with a strongly built body which is hinged at back and is fitted with a hydraulic ram on the underside to lift the front of the body and tilt it backward into the dumping position. A tail gate may be fitted at the rear of the body or the body may have a chute like shape in the rear with inside corners rounded and sides tapered to facilitate dumping which is most popular now-a-days.

Useful life of dumpers is generally 8 to 12 yrs i.e. 10000 hours to 15000 hours depending on their capacity. The life is also expressed in terms of km i.e. 200000 km.

Dumpers have generally capacity of 4.5 m3. Angle of tilt varies from 45’ to 62’.dumpers have capacity of more than 300MT have been manufactured and used for specific works. The usual dimensions ate 6.23 * 2.29 * 2.64 m3. The main advantage is that while unloading labors are not required.

2>EARTH MOVING MACHINES

These equipments are used to cut the earth or trees or rocks and then move them to a distance required. Equipments like Bulldozers are also used for leveling of the ground, cleaning land of timber, stumps, spreading earth fill etc. These equipments are very common of all the earth moving machine, a bulldozer is most useful and most of project sites require its use in one form or the other.

Bulldozer and Anglodozer

Bulldozer is basically pushing unit consist of a tractor either crawler mounted or wheeled to which a cutting blade is mounted at the direction perpendicular to the direction of travel. There is no difference in bulldozer and an anglodozer except that the cutting blade is set at an angle with the direction of travel.

The angle dozers push the load at angle of approximately 30’ to the direction travel of the tractor. It is specially used in the side hill works where material is to be piled on the side of line of travel.

Bull dozers push the material in forward direction while anglodozer pushed it on one side only. if attached blade can move 20 to 25cm then it is called as a tilted dozed. The size of bull

doer is decided by length, height and capacity of the blade. Bulldozers are collecting all the earth & soil undulation above its level of blade and collect in the bucket.

Ripper and Scraper

Rippers are used for rocks ripping whilst scrapers are used to scrap the surfaces. To rip means to take out by cutting or tearing hence a equipment used to cut or to tear a rock and to take it out is called ripper. As shown in Fig. 5.10 a cutting edge is attached to tractor which is quite strong to rip rock or very hard soil when pushed with it. It has been found that rocks which propagate round waves at low velocities are ripable. Tractored rocks, large grain size faults or weakness in any plan favors use of ripping. Sedimentary rocks also can be ripped easily.

Scraper is used mainly for earthwork operations of roads. Scraper consists of a scrap with a cutting edge. The excavated material is collected in the body of a scraper or bucket and then removed to the place of dumping, operation of a scraper consists of:

1. Lowering the front-end of the bowl until cutting edge attached, extended across the width of the bowl enters the ground and at the same time, raising the front apron to provide an open slot through which the earth may flow into the bowl. As scraper is pulled forward a strip of earth depending on cutting edge depth is forced into bowl. This operation is continued till the bowl is filled.

2. At this time when no earth is forced in bowl, i.e. bowl is full, the cutting edge is raised and the apron is lowered to prevent spin g during the haul trip.

3. Once it is taken to a place of dumping the cutting edge lowered to the desired height, apron is raised and earth is forced out between the blade and apron by means of a movable ejector mounted at the rear of the bowl.

It is a combination of cutting or scraping, loading and hauling. The capacity of a scraper depends on capacity of bowl. Output of a scraper depends on capacity of tractor, type of material to be handled, haul distance and other general conditions like weather, management etc.

Rippers or scrapers are classified on the basis of tractor whether it is wheel mounted or crawler mounted. Scrapers are also classified as single engine, twin engine, two bowl or multi-bowl, multi-engine etc. depending on its action. Similarly rippers are also classified on the basis of ripping blade like twin shanks ripper, towed type etc, scrapers are also classified as motorized and towed. In the motorized unit scraper is self-powered, whilst in towed it is like a tractor on 2 axles hauled by separate tractor usually a crawler. Many a time a pusher is also provided for extra power.

The capacity of scraper varies from 7.6 cubic m3 and above. The useful life of equipment is about 8 to 10 years (i.e. 9000 to 10,000 hours).

A thumb rule to determine output of a scraper is by formula =

Output in cubic metre per hour = 100 C/(3.28D + 3)

where C = Struck capacity of scraper in cubic metre, and

D = Haul distance (one way) in hundred of metres.

3>HOISTING EQUIPMENT

Hoisting means an operation consisting of lifting a load from one location to transport it if required to a reasonable distinct location and un-load it down. Equipment used for one or all of these are called hoisting equipment.

The hoists are used to lift the material & to haul it at required place, in the range of hoists. It does not mean the transportation of material but put it on platform or package it, generally hoists are connected with tractors or trucks for transport of hoists. They are generally settled on the crawler mounted wheels. Types of hoists are;

Jib hoists or chain hoists Transportable tower hoist or platform hoist Mobile hoists

The scaffolding type of hoists is easily developed by connecting some steel tubes with pulley arrangement, hook and jib frame. These types of scaffold hoists are developed at congestible sites specially at small building sites.

Scaffold hoist or chain which can be fitted to existing tubular scaffolding at a point just above the level to which the load is to be lightest type of powered builder hoists. The frame of this hoist can be fitted to existing tubular scaffolding upright in a few minutes and thereafter swivels on the upright. The scaffolding jib hoist is very useful on small building jobs where tower hoist in uneconomical or when it is not possible to own tower hoist at the site due to congestion or other reasons.

Chain hoist consist of gears, sheaver and chains. These are made in capacities 0.25 to 50 tones and are low in the first cost and easy to operate. Hand operated chain hoists are very much used in isolated locations where no motive power is have slow lifting speeds.

The transportable tower hoist consists of a vertical mast, carriage travelling on the mast and a power operated winch it is also called as a platform hoist. The transportable tower hoist is very much used on building construction. It takes time to erect, but once it erected it can be quickly extended to cater higher lifts as required It is great saver of man power as only two men are needed to operate it, one ground and the other at discharge level.

Cranes

Cranes are used in construction for lifting and erecting of precast units.types of cranes are classified as below:

1) Non-swing type

Tower crane. Climbing

2) Swinging cranes

Derrick cranes also known as scotch derrick or stiff legged derrick Mobile crane.

For different load lifting, different cranes are used. Cranes are economical only if used for large works. The used life of cranes varies from 10 to 20 years ( 12,000 to 30,000 hours )

Derricks crane

Derricks crane is mounted on a wide frame for stability. Its load carrying capacity is 5 to 10 tones and jib length 30 m long. It is mainly used for building frames. Mobile crane is us for low building works i.e. up to 1 to 2 storey height. It is mainly us for factory columns, trusses, frames etc. For very tall building climbing crane is generally used.

The derrick is a form of crane which widely used in civil engineering practice as a lifting crane, as a grabbing crane and oi occasion for pile driving. Derrick cranes are usually large structure with long jibs giving a wide out reach and a high lift. Derrick with capacities 30 tonnes jib length 50 m are common now-a-days in civil engineering works. There are mainly two types of derricks which an used on large projects.

The Guy derrick. Scotch derrick.

Tower crane

These are the swinging type cranes mounted on high steel tower. These cranes are vary useful for high rise buildings particularly for tall structures in congested areas and in assembly of high industrial plants with elements of steel structure. It can also be used for loading and unloading of heavy structural pieces. The tower on which crane mounted has a truss structure welded from angle bars and channels. Tower extension pieces are generally provided which are bolted to the main tower structure. Jib is attached to the last tower. The life of this crane is about 70 years i.e. 30,000 hours.

Hydraulic crane

This type of crane has become popular due to its unique properties such as its boom length and angle can be changed easily and quickly during operation. Further it has all the advantages of hydraulic power device. These are of two types :

(i) Telescopic boom crane. (ii) Cable operated boom crane.

The telescopic crane has fast speed, mobility and maneuverability. Its boom length can be increased at the rate of 110 metre/minute and reduced 104 metre per minute. It is not easy with cable operated crane. These crane operate hydraulically and have very smooth operation without jerks. These are usually truck mounted, very massive cranes upto a capacity of 1900 tonnes have been developed. Boom length up to 57 m and boom height up to 118 m have also been manufactured.

Fork Lift

It is a type of crane used to lift boxes etc. from one place and to keep them at the other side on another set of boxes or platform. Blades are inserted in horizontal gap of boxes and then mobile unit goes behind along with blade. The portion above that gap gets loaded over these fork blades and then these boxes are transferred to other place. These cranes are very common in factories, stores etc. fork-lift trucks are available with a load lifting capacity from 3 to 5 tonnes a load lifting height up to 6 m. The load hoisting speed is within J-5U m/min, and their no-load travelling speed is up to 30 km/hr, and when loaded, up to 20 km/hr.

The fork is suspended from a hoisting device consisting of main (fixed) frame 1 and movable frame 2. The fork is secured to carriage 4 which is suspended from the movable frame. The frame with the carriage is lifted by a single acting hydraulic (ram) 3 mounted on the main frame.

The main frame is pivoted on the truck frame and can be tilted together with the carriage in the vertical plane through an angle oi 3-4 degree forward and 12-15 degree backward with the aid of two hydraulic cylinders.

Jacks

Jacks are equipments used for applying pressure. They may be mechanical or hydraulic in operation and have a wide range of sizes from the small automobile jack to one of 100 tonnes capacity or more. Mechanical jacks may be of lever, screw or gear type. Screw jack works on principle of inclined plane. Hydraulic jack works on the principle that pressure exerted by a liquid on a surface is proportional to the area of the surface. From small portable hydraulic jacks to heavy car serving station lifts all work on this principle.

Hydraulic jacks in which pressure is excited by a liquid is most common. These have large capacities in small dimensions. The lift is provided by oil under pressure. These jacks can exert a pressure up to 200 tonnes and more. It consists of a cylinder of oil in which a piston moves under pressure of oil sent from a reciprocating pump. To release oil pressure a release screw is provided.

4>Excavating and Hauling Equipment

There is a wide range of excavating and hauling equipment available commercially, to which include shovel, dragline clamshell etc and a hauling unit either crawler mounted or trucks mounted (wheel mounted). To select proper equipment for particular job great care is required. These equipment as the name indicates consists of an excavator hauling unit also has a revolving unit through which an excavator can be swing to any direction horizontally. This combination of travel unit and revolving unit is called basic shovel to which different attachment are made to produce different excavating and hauling equipment.

REVOLVING UNIT CRAWLER MOUNTED TRUCK MOUNTED

Thus the basic shovel has the means of propulsion of the machine, of revolving the super structure around, and of operating the head or rig attached to it. With the further addition of the rig the basic shovel changes in to a complete machine of any type as required.

The capacity of digging varies for different soils. Earths like dry sand, loose earth, loose gravel, muck cinders, ashes etc can be lifted more efficiently. Dipper fill factors for such materials is about 85% to 110% and classed as easy digging. Wet clay, dry gravel etc is materials not very difficult to dig can be cut and lifted easily. Dipper fill factor for such materials is about

80 to 95%. Materials requiring some breaking by light blasting are termed as hard digging materials and have a dipper fill factor of about 70 to 90%. Heavy wet stick clay gravel with large boulder, cemented gravel etc come in to category of granite and sandstone. Hard and tough racks are required to be blasted. Their efficiency varies from 40 to 80% only.

Power Shovel

This is an equipment used for excavating all classes of earth except solid rocks. It is best suited equipment for close range work and have good control of digging. As shown dipper stick is attached in the centre of boom. Dippers used very in capacity from 3 cubic metre to 5 cubic metre as per requirements. The output of a power shovel mainly depends on type of material to be handled and depth of cut. Approximate hourly shovel handling capacities in cubic meters per hour for different material as shown below. It also has shown the optimum depth of cut for different shovel dipper capacity cubic metre.

If depth of cut is small dipper will not get filled completely in one pass and hence will reduce the output per unit period of time. As the angle of swing increases firm 45° to 180° the output decreases by unit to approximately 40 per cent at 180° swing.

Tractor shovel is extensively used now-a-days to handle and transport if required bulk material such as earth, coal etc. It is also used to load truck by loose material as shown. These are also of two types, i.e. crawler tractor mounted or wheel tractor mounted. These are also classified on the basis of capacity of bucket. The capacity of these bucket varies from 1.8 m3 to 4 m3 heaped.

Hoe

It is an excavating equipment of power shovel group hence it is also called as Back shovel or pull shovel. It is used to excavate below natural surface of ground on which machine rests. It consists of a dipper which can be lowered down to a level below the level of machine. This equipment is used to excavate trenches, pits. Most effective digging action occurs when the dipping stick is at right angles to the boom. It is also known as earth excavator.

Single bucket excavator and loader

Many a time a single bucket with attachments is used to excavate and lift loose material. It is then loaded into trucks and discharged to a desirable place. Such single bucket excavator has become very common. Owing to their versatility, mobility and possibility, construction excavators are very effective for small and detached construction project and for excavating handling and operation on larger construction projects. The operation of excavating and lifting materials and then unloading to the truck & trolley.

Clamshells

This equipment is used to lift and handle loose material like sand gravel, crushed stone, coal etc. the buckets of clamshell varies in capacity from 0.25 m3 to 2 cubic metres. These can be attached to a long boom to increase the working area. The actual capacity of bucket is defined by various methods. A more accurate capacity is given by water level capacity, i.e. capacity of bucket filled with water and leveled. It is measured in litres or cubic metre. The plate line and heaped measure capacities are expressed in cubic metre.

Use of clamshells has become very common now-a-days. Buckets used for clamshells are of various types heavy duty type used for excavation: medium duty type for general purpose and light duty type for light materials. Clamshell buckets with teeth are used for excavating purpose and buckets without teeth are used for lifting. If with teeth they form a inter lock between two halves of bucket and have grip with each other. Clamshells in general are used mainly for lifting materials.

Dragline

The dragline is one of the most flexible excavating tool. It has more reach than a shovel both for excavating as well as for disposal. It can dig far below its base as well as at almost any other location. It can be used even in underwater. However, it cannot handle hard digging so efficiently as it is done by shovel. The boom has a fixed angle to horizontal and is generally 30 to 37°.

There is not much difference between a shovel and a dragline. These can be changed simply by changing the boom, different buckets are used for different material to be handled with it. Heavy duty bucket used for excavation of heavy materials whereas medium duty are used for general work and light duty bucket are used for light materials. The bucket size varies from 1.15 m3 to 27 m3 consequents the weight of empty bucket varies from 1450 kg to 32,250 kg. The life of equipment varies from 10 to 25 years (12000 to 40000 working hours) depending on bucket capacity and type of manufacture. The usual bucket capacity varies from 1.15 m3 to 3 m^3.

As other equipments, it also operates by swinging its bucket out on to the material to be excavated, then hauling it back towards the base machine, excavation and filling as it comes on. It is generally used for bulk excavation of a reasonable light nature working below trucks level. It is mainly used for excavating trenches when sides are permitted to establish their angle of repose without shoring, compare with power shovel, these have got less efficiency. As usual drag-line are also classified on the basic of their mounting i.e. weather truck mounted, crawler tractor mounted or wheel mounted. An approximate hourly dragline capacity in cubic metre varies for different soils. It is approximately 70 per cent that of shovel reason being small capacity of bucket and more boom length. Due to more length to boom it can cut to a greater

depth compare to the power shovel by about 50 to 60cm. with more swing angle capacity reduces by 30%.

Boom-length :15—24m

Capacity : 2700—5400 kg

Boom-angle : 20°—45°

Dumping radius : 12 to 26 m3

Dumping height : 3 to 13 m

Maximum digging depth : 12 to 6 m

Speed-crawler wheel and trucks : 2 km per hour 50 kmph

Dredger

Dredger means the excavation of bed of river, lake or sea for purpose of deepening.

This excavation is generally done at docks and harbors to increase the depth of water way to provide sufficient draft for ships. A dredger is an equipment used for dredging. Following are the common dredgers used now-a-days.

Dipper dredger. Ladder dredger of continuous bucket dredger. Suction dredger or Hydraulic dredger. Grapple dredger.

Dipper dredger consists of a floating vessel to which a shovel or dragline is mounted whilst in grapple dredger, a clamshell is attached instead of shovel or dragline. These dredges can excavate to a depth of 0.5 m to 20 m. Ladder or bucket dredger consist of a bucket elevator mounted on a ladder, i.e. is a sort of belt conveyer system.

The speed of it varies from 20 to 30 km per hour and capacity of individual buckets being 85, 140 or 225 liters. This system is only suitable for soft ground or for loose filling like sand and gravel.

A section on hydraulic dredge consists of a suction pipe carrying at the lower end a cut of some sort. This suction pipe is connected to a centrifugal pump having a long delivery pipe for discharging the loosen soil to specially selected spot on shore needing reclaiming or filling. This type of dredge is very effective in beds of sand, silt, mud and clay. Gravel and soft rocks are easily reduced by the cutter up to 60 m depth, this can be used efficiently.

5>EARTH COMPACTORS

Compaction of the earth to increase its density the K increasing its bearing power and strength and to give impermeability/ on earth structure?) Compaction is also done to tar pavement to increase its bearing power. Many type of rollers are used to compact them. To produce desired compaction, number of passes given should be sufficient.

Many types of compacting equipments are available like plain steel rollers, vibration rollers, temping rollers, pneumatic tired rollers etc. They are also classified as manually propelled or mechanically operated. Self-propelled vibrating plates or shoes are also used for compacting the surfaces. Selection of a type of a roller depends on class of work and type of surface to be compacted.

Plain steel rollers or smooth drum roller weighing from 5 to 15 tonnes are used for ordinary rolling works where deep compaction is not required, for ex. road work for compaction of tar road. Steel rollers also called as smooth wheel roller. It consists of two axles and three wheel of which front wheel is used for steering whilst rear two wheels are used for driving the unit. Two wheel tandom and vibrating road roller. A three wheel tandom roller differs from two wheel in that it has three drums and three axles are more effective. There rollers are designated in terms of weight which is stated in tonnes. A 8/10 tonnes indicates that, minimum weight of machine in 8 tonnes and can be ballasted to give a maximum weight of 10 tonnes.

For compacting earthwork in the embankment or canals compaction is required to be done at great depths. Sheep foot temping roller which consist of a hollow steel drum around the periphery of which welded projections or feet just like that of sheep usually 15 to 20 mm long are used. The soil is compacted and consolidated when compression by projecting teeth is more than 12mm deep on the surface has been rolled 16 to 20 times. the top layer s finished with smooth rollers. The below feet is 4 to 7 kg/cm2 for light rollers and 28 to 70 kg/cm2 for giant rollers. This be attached to hauling unit like tractor. These rollers are 0.9 to 1.5 m in length and 0.75 to 1.5m in diameter. These rollers have weight varying from 2 to 13 tonnes. These rollers transmit a pressure of 10 to 50 kg/sq cm & some times 70 kg/sq cm. About 12 no. of passes are enough for average ground.

The grid rollers consist of steel grill fixed along periphery of wheel of cast alloy steel. The grid combines soil and produces high pressure at point of intersection of the base hence the rock gets crushed and compacted. These rollers have generally 7 to 9 tonnes capacity & they are used in rocky soils.

Pneumatic tyred rollers are compact the soil through static weight, kneading and vibrating. It consists of ballast-box mounted between two axles. The tyres are arranged such that tracks of forward wheels in between the tracks of rear wheels. Compaction occurs due to these tyred wheels. No. of tyres can be 4 or more. The maximum load may be in the range of 180 to 185MT. These rollers can compact up to depth of 60ccm and are useful always in the soils except rocky soils.

Hard rollers can also be used by filling soil, sand & water in the hollow steel cylinder to increase the weight.

6>PNUMETIC EQUIPMENTS: AIR COMPRESSORS

Compressed air is considered as an indispensable construction tool. It is used extensively on construction projects for drilling rock or other hard formations, loosening earth, operating air meters, hand tools, pumps, mucking operation, cleaning etc.

When air is compressed it receives energy. This energy is transmitted through a pipe or hose to the operating equipment, where a portion of the energy is converted into mechanical works. The operation of compressing, transmitting and using air results in a loss of certain energy which gives overall efficiency less than 100%.

Air compressor is the machine used to increase the pressure of air by reducing it’s volume. The capacity of a compressor is the actual volume of free air drawn into a compressor per minute and expressed in cubic metre. The quantity of compressed air required for different work varies from 0.5 to 1 cubic metre per minute for chipping hammers clay diggers to about 7.5 to 8 cubic metre per minute for hoist drifters.

7>CONVEYING EQUIPMENT

A conveyor is an equipment which is capable of carrying material in a continuous stream and usually has as its distinguishing feature, some kind of an endless chain or belt which by its motion constitutes the primary device of the conveyor. Aerial transportation like rope ways, cable ways etc. are also conveying equipment. Conveying may be horizontal or vertical or inclined which is most common. An elevator or lift is also a vertical conveyor.

Its use in field of construction has increased extensively. It is most satisfactory and economical method of handling and transporting materials like earth, aggregate, concrete, mine ore etc. It's use in the form of ropeways, cable ways for transportation of men and materials in hilly regions has become a pleasure now. These have been used in offices, libraries, for handling office material, books etc.

A conveyor for transporting material for a short distance may be portable unit or a fixed installation. For transporting materials to a considerable distance a number of flights are used, each flight being a complete conveyor unit. These are arranged in series such that material from one will be shifted to next one automatic. This system to handle and transport materials to a considerable distance by a belt conveyor is not very common in India. Ropeways and cable-ways become very common in mines and in hilly regions, and have been found economical and more feasible. They are certainly economical for mass concreting work in dam sites and at crushers sites to transport and to load crushed aggregate to trucks and dumpers.

Belt

The belts used in conveyors may be of rubber, canvas woven wire, steel etc. depending upon type of work to be done. Canvas stitched canvas belts, as these are sometimes called are made of duck or canvas of good quality. These are made into plies and stitched together with a sewing machine and water proofed with suitable compound. The suitability of belt to be used under different environment depends on quantity of surface coat of the belt. These belts are used to handle ores, coke, aggregate, clay etc. These belts can withstand a temperature of 250°F.

Balata is a tree gum found in West Indies used to join water proofed cotton duck plies and called as balata belt. These are better than rubber belts.

Wire mesh belt consist of an assembly of flattened helical coils of wire of steel or brass or an alloy woven together to form a flexible band with sufficient rods or cross wires woven at intervals to act as hinge. These belts are used at places where other fiber belts cannot be used either due to higher temperature or due to wetness.

Steel belts consist of bends of steel cold rolled, hardened and tempered. They are usually made about 1 mm thick, 80 cm or more in breadth and 110 m long. These belts are always flat and can be widened by joining two or more belts widthwise.

Rubber belts are most popular that are used in belt conveyor. These are made of rubber covered cotton or rayon laid up in plies and are suitable for all kind of services. Now-a-days synthetic rubbers are becoming very common. A wire cable reinforced belt is also becoming popular in ore conveying.

It is necessary to select a belt with sufficient strength to resist maximum tension likely to occur. Further it should be wide enough to transport the material at required rate. The quantity of material that can be transferred depends on the type of belt and its load carrying capacity, slope, angle of repose of material to be handled and speed. If buckets are attached to a belt its load carrying, increases.

Idler

These provide the supports for a belt conveyor and provide necessary toughness to the belt. These may be flat or toughing. Flat idlers are used mainly to convey piece goods at lower speed. One common form of toughing idler It consists of 3 rollers placed edge to edge and free to move on bearings. The central roller being horizontal and outer one inclined at 20°. For wide belts even 5 rollers are used. Diameter of rollers used is generally 10 to 20 cm depend! capacity. Large diameter gives less friction and better belt protection. Spacing of idlers varies from 60 to 150 cm. There are also many types like return idler, training idler. There is slight variation in construction but the main object is to support belt. Return idlers are used to support empty belts hence spacing is increased to 3 m centre to centre.

Driving Unit.

Driving unit mainly is a three phase induction motor electrically operated or hand operated for emergency conditions Alternatively a compressed air may be used. The external power required to drive a belt conveyor depend on

Load to be moved. Angle of movement whether horizontally, vertically or at an inclination. Number of idlers. Friction offered by idlers belts and pulleys. Number of pulleys to be driven.

Hence horse power of motor should be sufficient to complete operation efficiently. Along with 3-phase induction motor, driving unit consist of head pulley, tail pulley and intermediate pulley. More the number of pulleys less will be the driving force required. These pulleys are arranged in tandem to increase more contact area with the belt. Speed controllers are also installed.

Take ups

Conveyor belt take ups are used to adjust the length of belt as it changes due to change in temperature during its operation. A screw take up as is used to increase the length of conveyor. It is adjusted by moving the head or toil pulley. It is good method of adjustment for small pulley. "Hold backs" are used to prevent the load from coining back in case of power failure. It should be strong enough to resist the force by the load during power failure. Take ups are also of type vertical gravity take or horizontal take up.

Feeders

The purpose of the feeder is to feed materials to belt at a uniform rate. Many a times instead of discharging material to belt directly it a chute which reduces to possibility of impact on a belt. Many types of feeders are available. They are classified on the basis of method used to feed.

Apron feeder consists of a moving flat, rubber covered belt. It receives material from a gated hopper and transfers it to belt. A reciprocating feeder is used in which a plate placed under a hopper in operation to produce reciprocating effect, due to which the material moves on to the conveyor belt. A rotary vane feeder consists of a number of vanes mounted on a horizontal shaft. These vanes deliver measured amount of material to the conveyor.

Trippers are sometimes used when material is required to be removed before it reaches the end. But it is used rarely as it requires extra power further, it is rarely required to remove material in between.

8>ROCK DRILLING EQUIPMENT

Before excavation of rock is started it is necessary to consider various factors such as structural arrangement of rock strata, nature of rocks to be encountered, the possible presence of water, and the resistance of exposed rocks to weathering influence. The structural arrangement of rock strata affects considerably the side slopes to be adopted in design. It also affects underground water problem, line of movement etc.

Of great importance is the nature of the rock to be excavated. Nature of rock means its properties of a particular type of rock to be encountered all over the area to be excavated for ex. sandstone can vary from a hard and compact rock to material that is little better then that of compacted sand. Adequate drainage facilitation are naturally an important feature of all rock excavation work.

The usual methods of rock excavation are drilling and blasting. Relatively soft rock can be excavated by drilling operation whilst for hard rock blasting is essential. It also depends on amount of w be excavated It is surprised to note that, no more advance t0 technique of rock excavation methods have developed basically equipments used for drilling, the nature of explosive for blasting improved to a great extent to improve the efficiency of rock removal. One man drilling rigs have developed correspondingly the adoption of removable bits and the improvement in the wear & tear properties of the bits have led to great advances in handling of drill bits, and therefore in the operation of drilling in general.

Drilling rock.

Drills are used to excavate holes in the rocks for blasting. After, the holes being made, they are filled with explosives and blasted. These operations are necessary to loosen the rocks in order that excavating equipment may handle it.

There are various types of drilling equipments used to drill the holes. The type to be selected depends on type of rock, amout of work and the size of hole. Bits are needed to drill the rock. Bit is a cutting equipment attached to drilling rod to disintegrate the rock. The success of drilling operation depends on the ability of this bit to remain sharp under the impact of the drill.

Rock bits or steel bits made of steel and varying in size from 2.5 to 11 cm and can be resharpened two to six times. The depth of hole that can be drilled with it depends on type of rock and varies from a few centimetres to several metres.

Carbide insert bits consists of a very hard metal tungusten carbide embeaded in steel. These are used when rocks are very abrasive and steel bits do not work properly. These are also as illustrated in Fig. 5.53. Initial cost of these bits is more but over all they are found to be economical.

BIT OF CARBIDE ALLOY

Before drilling starts, it is imperative to carry out preparatory work including building of access roads and leveling of working areas, setting out of work which ensures efficient drilling. If required holes may be drilled by mobile or truck-mounted rigs.

Rigs for cable drilling are used to make wells up to 400 mm in diameter and up to 200 m deep. The drilling process consists in alternately breaking of rock by drilling tool impacts and removing of debris from the well. The breakage time in the overall drilling cycle increases with the hardness of rock. The effectiveness of drilling depends on the correct choice of bit shape, height of lift and frequency of impacts of the drilling tools which produce impacts of maximum energy.

Drills used for excavation are broadly classified as :

1. Abrasion Drills

Blast hole drill Diamond drill Shot drill.

2. Percussion Drills

Churn drill Jack hammer Drifter and wagon drills Piston drill Stop hammer.

Abrasion Drills

(i) Blast hole drill. : It consists of a steel rod to which a roller b is attached at its bottom. The bit is rotated and drilling proceeds d to abrasion between drill bit and surround rock. Compressed air may be used for its rotation. Disintegrated rock is removed by the steam of compressed air and it cools the bit also. It is self-propelled and mounted on any hauling equipment. For soft and medium rocks it is very suitable. The usual life of it is 10 years, i.e. 10,000 hours.

(ii) Diamond drill. : It is also rotary drill and mainly used in exploration work1 and in foundation treatment. To extract cores from the interior of the earth, these drills are very useful. These drills can drill to a depth varying from a few metre to a four to five thousand metres also effectively and can penetrate to very hard rock. Rate of drilling varies from 30 cm to several metres per hour. These costs initially more but they are certainly economical for longer use. These can be attached to any hauling units further these can drill to any desired direction from vertical downward to upward.

A drilling rig consists of diamond bit, a core vassel, a jointed driving tube and a rotary head to supply the driving torque. Water is pumped through driving tube to remove the cuttings. The pressure on the bit is regulated through hydraulic feed swivel head.

(iii)Shot drills. : A shot drill is a tool which depends on the abrasive effect of chilled steel shot. To penetrate the rock the bit consists in the form of a section of steel pipe with a scratched or a roughened lower end. The bit is rotated and cuttings are removed by water which is supplied through the drill rod. Standard shot drills can drill holes to a depth of about 200 metres and more

with varying diameter from 6 to 50 cm. Very hard rocks can also be drilled with shot drills. It is vary mainly used for vertical holes only.

Percussion Drills

(i) Churn drill. It consists of a long steel bit which is lifted up and dropped down to give an impact for disintegration of the rock. It can drill vertical holes of 15 cm diameter or more to a considerable depth in any type of rock. It works mechanically.

(ii) Jack hammer. It is an air operated portable drill use primarily for drilling vertical holes downward hence they are also known as sinkers. It moves vertically up and down by compressed air which transmits an impact to the bit through drilling rod. It is classified according to the weight of hammer such as 20 kg. or 25 kg. About 2000 blows per minute are transferred which produces the hammer effect for drilling operation. These are used to drill holes of diameter 5 to 6 cm and of a depth varying from 3 to 6 m. The cutting can be removed by air or by water. These can be mounted on tripod to have more stability. These are used only on very hard ground as tripod is required to be shifted slightly for adjustment of drilling operation.

(iii) Drifter. Drifter is a heavy rock drill similar to jack hammer and weigh from 45 to 68 kg and more. But it is very large hence requires mechanical mounting to work with. It can drill holes of diameter of II cm and upto a depth of 12 metre with steel charge of 4.6 metres. These holes can be drilled either horizontally or vertically. Drifter are used generally for tunnel excavation work or for making holes for the mining. The cutting is removed either by air or by water. It is also called as sinker.

When it is mounted on a wheeled frame it is called a wagon drill, and becomes portable one. This wheel frame is commonly made of tubular section. Wagon drills are suitable for use in drilling relatively dead holes in non-abrasive and hard soils as heavier drills can be employed with longer steel changes. Due to tubular frame, steel is accurately guided and bit end is kept well pressed. It can be used for drilling at any angle. Wagon drijls are commonly used for quarrying operation.

If it is mounted on truck, it is called truck-mounted drill and can move quickly to any new site and then works hydraulically or by compressed air.

(iv) Piston drills. It is also a self-propelled percussion machine which is mounted on crawler tractor. In this a hollow tube is attached to the piston. The stroke and rotation of the piston is through this attached tube and it is so adjusted to give best performance for the particular type of rock being drilled, carbide insert drills are also available attached to the tube. Piston drills are up to 15 cm in diameter can drill to a depth of 20 m or so.

(u) Stop hammer. Jack hammer are used for drilling downward. Stop hammer is a modified form of jack hammer and hence can be used to drill overhead as required in core mining tunnels.

Other Types

Fusion piercing. When a mixture of oxygen and a flux bearing fuel such as kerosene are burnt and sent through end of a blowpipe, a fusion piercing effect is produced at the other end of blow pipe. When this flame is directed to the rock a high temperature of fusion flame about 4000°F causes some types' of rocks to flake out. A water spray, directed on the heated rock, quenches the rock into small fragments which are blown out of the hole by the expanding steam

Selection of drilling method and equipment

Holes are drilled by many reason, they are

(i) To receive charge of explosives for blasting of rocks (ii) For exploration work. (iii) For injection of grout material.

Within practical limits one which will produce the greatest overall economy along with efficiency for particular project is the most satisfactory. Following are the factors that affect the selection of the equipment.

1. Nature of terrain.2. Required depth of hole which consequently depends on purpose of drilling.3. Size of the project and extent to which rock is to be broken.4. Availability of water to decide dry drilling or wet drilling.5. Core size required for exploration diamond drills can be used for small cores whilst

short drills are preferred for large. Up to 7.5 cm dia cores, diamond drilling is most satisfactory. For cores of 20 cm and more shot drills are best suited. To drill holes of about 15 cm in diametre and 15 to 90 m deep, blast hole or rotary drills are best suited.

9>BLASTING EQUIPMENT

The process of loosening and breaking the large mass of rock into smaller ones by the help of blasting powder is called blasting. The functions of blasting a rock mass are :

1. To produce stone for masonry work and ballast for concrete and road metalling.2. To excavate foundation for building road formation in rocks.

3. To excavate for tunnel work.

When the rock is solid, un-fissured and very hard, blasting by means of some explosive is necessary. It must be remembered that the aim of blasting is to loosen and separate out as much rock as possible out of the rock mass and not to shatter the rock into pieces.

Detonators

Two types of detonators are manufactured — plain detonators and instantaneous electric detonators.

The plain detonator, for use with safety fuse, contains a base charge of pentaerythritol tetranitrate with a primary charge of ASA composition (lead oxide, lead styphnate and aluminium powder) in an aluminum tube. It is manufactured in No. 6 strength only. The base of the tube is conical which gives an intense local shock due to the 'Munroe effect'.

Instantaneous electric detonators are also made in No. 6 strength with either aluminium or copper tube; the former can be used in almost all workings, except underground coal mines where mining regulations specify the use of copper electric detonators only.

The specifications and firing characteristics of these detonators are given below :

1. Leading Wires : 24 SWG tinned iron covered with yellow

PVC in the case of copper detonators, and blue PVC in the case of aluminium detonators.

2. Electrical resistance with 1.8 m, 2.5-3.8 ohms leading wires3. Firing characteristics.

10>Tunneling Equipment

Tunnel Constitute one of the most important classes of heavy construction works unavoidable in many river valley project, railways and road constructions, and mining and sewage schemes. Two principle applications of tunnels are in conducting water and conducting rail and road traffic.

In India great deal of tunnel construction has taken place in the execution of several river valley project, such as the Bhakra Dam, Beas Dam, Beas-Sutlej link, Yamuna hydro-Electric Project, Koyna Project and Idikki project.

Methods Of Tunneling:

Tunneling Methods may be broadly classified into two categories:

1. The Conventional “drill and Shoot” method

2. The Recent “mole” Tunneling

Drilling jumbo:

The Drilling Jumbo is a portable structure made of steel members in a shape and size such that it

is capable of moving in and out of a tunnel. it is capable of moving in and out of a tunnel. The

jumbo provides one or more working platforms on which rock drills of the drifter class are mounted and operating staff is able to stand and move during drilling operation. The platform decks are adequately spaced depending upon the size of the tunnel. The lowest deck should be so provided that a space of 10 ft X 12 ft (3 m X 3.6 m) is available in the centre to allow for traffic under the jumbo. Alternatively, the lower member may be hinged to provide passage of mobile equipment underneath. In small diameter tunnels (less than 5m diameter) this arrangement permits the jumbo to stay on in the tunnel after drilling. Jumbos in large tunnels are usually rail mounted, but pneumatic wheels are also employed to lend flexibility of movement outside the tunnel. Wheel mounted articulated rigs are available which are fitted with a number of booms bearing the drills. These rigs are easy to move in and out of the tunnel.

The jumbo permits the drills to be located in any desired position to conform to drilling pattern used. The drills are mounted ladders or on pusher legs. Use of feed legs improves drilling rate but demands skilful operation. These are hydraulic oil compressed air powered and support the drills which can be placed in in any position in only a few seconds.

Explosives:

Ammonium nitrate explosives are used in large diameter holes and are available in cans varying from 4 to 12 in. (100 mm to 300 mm) in diameter and from 16 to 24 in. (400 mm to 600 mm) in length. The cans weigh from approximately 11 to 75 lb. (5 to 35 kg). The cans are waterproof and can be used in wet rocks. These explosives are less expensive and are also much safer in handling than dynamites. They however, need special primers for detonation.

Ventilating Fans and Ducts:

Exhausting the fumes produced by blasting and providing suitable quantity of fresh air for normal ventilation are necessary in tunnelling work. Air may be blown into the tunnel through electrically driven blowers, or stale air may be exhausted through an electrically driven fan causing convection currents to take fresh air into the tunnel. Both, exhausting and blowing in may be used and the same installation utilized through suitable manipulation with valves in the ducts.

Temporary Supports:

Temporary supports are required in tunnels to support the ground adjacent to the tunnel, immediately after blasting and before proceeding to clear the muck. Rock falls may result from faults and folds in the formation and these may be so severe that the tunnel bore may be totally filled up with rock collapse and damage may be caused to machines and workmen. A total stoppage of construction may result.

Steel H-beams properly bent to conform to the shape of the tunnel (called ribs) have been used as temporary support. Two or more pieces are bolted or welded together to cover the entire curvature, and these are spaced from as close as 18 in. (450 mm) to as far as 6 to 8 ft (1.8 to 2.4 meters) depending upon the nature of the rock supported. In early work timber was used to support tunnel roof which gave the operation the name of "timbering". Steel, however, provides thinner sections, is easily installed and serves supplemental to steel reinforcement.

The space between the ribs is filled up with heavy pieces of timber or precast concrete sleepers or steel plates. Extending from rib to rib, this installation called lagging prevents broken and loose rock from falling over the equipment and personnel working inside the tunnel. The space between the lagging and the rock in situ is filled with timber, rock gravel or lean concrete (called initial concrete).This supports the natural formation and prevents its shifting towards the tunnel roof.

Rock bolts are specially suited to support in soft rock and earth. These are steel bolts installed in holes drilled through the loose mass into stable rock capable of supporting the load of loose rock.

Mucking Equipment:

This equipment includes loaders for excavated rock and carriers for its removal. Restrictions of space and the necessity for making mucking operations automatic and speedy make the selection of this equipment vitally important. The choice of drive, whether diesel powered or electrically-powered is another important aspect of selection. Diesel equipment may need fitting of scrubbers

to reduce ventilation problems. For carrier units selection has to be made between the rail mounted and pneumatic wheel mounted equipment.

Rock Loaders:

Loading of rock in tunnels may be done through standard earth loading machines like the full revolving power shovel and tractor loader or through special equipment called muckers. Where inside dimensions of the tunnel permit use of standard machines or articulated models, loading may be accomplished at low cost. If, however, space restrictions inhibit even short boom power shovels or articulated loaders, use of mucking machines becomes unavoidable. The loaders may be crawler or wheel mounted and may run on tunnel bottom or on rails. They may be powered by compressed air or by electricity, Diesel or gasoline prime are rarely used.

Tunnel Concreting:

Tunnels used as water conductors are usually concrete lined to prevent seepage of water. Traffic tunnels may be concreted only in portions where rock formation needs additional support. Alternatively, masonry is employed instead of concrete in these tunnels.

Concreting operations include: fixing of reinforcement and form work, supplying mixed concrete inside the tunnel at the point where it is to be placed, placing the concrete and compacting it after placement. The reinforcement steel, bent to the required shape, is transported in sections and assembled inside the tunnel with the help of a jumbo. The drilling jumbo with some modifications may be used or a special reinforcement jumbo may by constructed.

Tunnel forms may be made of steel or wood or a combination of steel and wood. Comparative economies should be studied before one of these is selected and the form should be designed to resist concrete pressure during placement. Forms are mounted on a traveller unit called concreting gantry. The gantry is equipped with adjustable jacks or screw ratchets for extending the form into position and then collapsing the form into position for concreting and then collapsing it slightly to pull it away after concrete has set initially. The gantry is then moved to next position for concreting another section of tunnel length. Along the side walls and roof of the form, hinged doors are provided which permit placement. Temporary openings may also be used for pouring concrete behind the forms. The proper design of concreting gantry is essential for success of a concreting operation in tunnels.

Additional equipment on concreting gantry includes : travelling trolley for concreting sides, top hopper for concreting arch, belt conveyors, pouring pipes, concrete placing pump, pneumatic concrete placer and air, water and electricity supply connections. The concrete in invert and sides of the tunnel is generally gravity poured while the arch is concreted through concrete placer or pumpcrete.

Machine Tunneling:

In the advanced countries of Europe and in U.S.A. the technique of tunnelling has been completely mechanized and made easier, less expensive and Safer through use of tunnelling machines, also called moles. These machines cut or pulverize the rock in entire section of the tunnel, convey the cuttings and advance into the bore in the continuous manner, giving high rates of driving. The bore is cut to a precise diameter and the danger to overlying structures, pavements and utility lines due to blasting in conventional drilling is completely eliminated. The tunneling Machines have arrangements for transporting and fixing steel supports, concreting the interior and grouting around the bore. Since the machines are operated by electricity and there is no blasting involved, ventilation requirement are very little. In countries where facilities for manufacturing these exists and spare parts and technical know-how are easily available, use of moles results in less expansive drilling. The magnitude of work should, however, justify the heavy investment in procuring the machine.

10>PUMPING & DEWATERING EQUIPMENTS

RECIPROCATING PUMPS

Reciprocating pumps are those which cause the fluid to move using one or more oscillating

pistons, plungers or membranes. Reciprocating-type pumps require a system of suction and

discharge valves to ensure that the fluid moves in a positive direction. Pumps in this category

range from having "simplex" one cylinder, to in some cases "quad" four cylinders or more. Most

reciprocating-type pumps are "duplex" (two) or "triplex" (three) cylinder. Furthermore, they can

be either "single acting" independent suction and discharge strokes or "double acting" suction

and discharge in both directions. The pumps can be powered by air, steam or through a belt drive

from an engine or motor. This type of pump was used extensively in the early days of steam

propulsion (19th century) as boiler feed water pumps. Though still used today, reciprocating

pumps are typically used for pumping highly viscous fluids including concrete and heavy oils

and special applications demanding low flow rates against high resistance.

CENTRIFUGAL PUMPS

A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure and

flow rate of a fluid. Centrifugal pumps are the most common type of pump used to move liquids through a

piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by

the impeller, flowing radially outward or axially into a diffuser or volute chamber, from where it exits into

the downstream piping system. Centrifugal pumps are typically used for large discharge through smaller

heads. The screw centrifugal pump is a popular choice for handling delicate products such as food and

crystals. Its low shear characteristic reduces emulsification when pumping mixtures making it ideal for

pumping oily water and Return Activated Sludge [RAS] as it does not damage the floc. The pump's ability

to pass long fibrous materials such as rope without clogging makes it a frequent choice for municipal

waste water applications. A screw centrifugal pump typically has an operating efficiency of 70% to 85%. It

has a relatively steeply rising head/capacity curve shape giving it good flow control capability over its

allowable operating range.

12>PILE DRIVING EQUIPMENTS

Diesel hammer

A modern diesel pile hammer is a very large two-stroke diesel engine. The weight is the piston,

and the apparatus which connects to the top of the pile is the cylinder. Pile driving is started by

having the weight raised by auxiliary means — usually a cable from the crane holding the pile

driver — which draws air into the cylinder. The weight is dropped, using a quick-release. The

weight of the piston compresses the air, heating it to the ignition point of diesel fuel. Diesel fuel

is added/injected into the cylinder. The mixture ignites, transferring the energy of the falling

weight to the pile head, and driving the weight back up. The rising weight draws in more fuel-air

mixture, and the cycle starts over until the fuel runs out or is stopped by the pile crew.

Hydraulic hammer

A hydraulic hammer is a modern type of piling hammer used in place of diesel and air hammers for

driving steel pipe, precast concrete, and timber piles. Hydraulic hammers are more environmentally

acceptable than the older, less efficient hammers as they generate less noise and pollutants.

Specialty equipment which installs piles using hydraulic rams to press piles into the ground. This system

is preferred where vibration is a concern. There are press attachments that can adapt to conventional pile

driving rigs to press 2 pairs of sheet piles at a time. Additional types of press equipment sit on top of

existing sheet piles and grip onto previously driven piles. This system allows for greater press-in and

extraction force to be used since more reaction force is developed. The reaction based machines operate

at only 69dB at 23ft allowing for installation and extraction of piles in very close proximity to noise and

vibration sensitive areas where traditional methods may threaten the stability of existing structures.

Vibratory hammer

Vibratory pile hammers contain a system of counter-rotating eccentric weights, powered by

hydraulic motors, and designed in such a way that horizontal vibrations cancel out, while vertical

vibrations are transmitted into the pile. The pile driving machine is lifted and positioned over the

pile by means of an excavator or crane, and is fastened to the pile by a clamp and/or bolts.

Vibratory hammers can either drive in or extract a pile; extraction is commonly used to recover

steel "H" piles used in temporary foundation shoring. Hydraulic fluid is typically supplied to the

driver by a diesel engine powered pump mounted in a trailer or van and connected to the driver

head through a set of long hoses. When the pile driver is connected to an Excavator, it is

powered by the excavator's own diesel engine. Vibratory pile drivers are often chosen to mitigate

noise, as when the construction is very close to residence or office buildings, or when there is not

enough vertical clearance above the foundation to permit use of a conventional pile hammer (for

example when retrofitting additional piles to a bridge column or abutment footing). Hammers are

available with several different vibration rates, ranging from about 1200 vibrations per minute to

about 2400 VPM; the vibration rate chosen is influenced by soil conditions at the site and other

factors such as power requirements and purchase price of the equipment.