Lakshitha Senarathne BSc (Hons), AMIE(SL)

Earthworks are engineering works created through the processing of parts of the earth's surface involving quantities of soil or unformed rock.

1. Excavation 2. Trenching work 3. Stabilising ground 4. Formation of slopes 5. Cutting & Embankments

5  In construction terms, excavation is the process of removing earth to form a cavity in the ground.  On small sites or in confined spaces, excavation may be carried out by manual means using tools such as picks, shovels and wheelbarrows. Larger scale excavation works will require heavy plant such as bulldozers and backactors.

This involves the removal of the exposed layer of the earth’s surface, including any vegetation or decaying matter which could make the soil compressible and therefore unsuitable for bearing structural loads. The depth will vary from site to site, but is usually in a range of mm Topsoil Excavation

This involves the removal of the layer of soil directly beneath the topsoil. The removed material (referred to as 'spoil') is often stockpiled and used to construct embankments and foundations Earth excavation

This is the removal of material that cannot be excavated without using special excavation methods such as drilling (by hand or with heavy machinery) or blasting with explosives Rock excavation

This is the removal of excessively wet material and soil that is unsuitable for stockpiling Muck excavation

This is the removal of a combination of the above materials, such as where it is difficult to distinguish between the materials encountered Unclassified excavation

 Process of excavation whereby the material that is cut or stripped.  The removed topsoil and earth can be used as fill for embankments, elevated sections, form a level surface on which to build, as elevated sections of the site are ‘cut’ and moved to ‘fill’ lower sections of the site Cut and fill excavation

 A trench is an excavation in which the length greatly exceeds the depth.  Shallow trenches are usually considered to be less than 6 m deep, and deep trenches greater than 6 m.  Trench, or footing, excavation is typically used to form strip foundations, buried services, and so on. The choice of technique and plant for excavating, supporting and backfilling the trench depends on factors such as; the purpose of the trench, the ground conditions, the trench location, the number of obstructions, and so on Trench excavation

 The common techniques that are used include:  Full depth, full length: Suitable for long narrow trenches of shallow depth, such as pipelines and sewers.  Full depth, successive stages: Suitable for deep trenches where works can progress in sequence, reducing the risk of collapse.  Stage depth, successive stages: Suitable for very deep trenches in confined areas, deep foundations and underpinning. 13

 A basement is part of a building that is either partially or completely below ground level Basement excavation

 This typically involves stripping topsoil and cut-and-fill Road excavation

 This typically involves the removal of material for the footing and abutments of bridges. The work may be subdivided into wet, dry and rock excavation. Underwater excavations may require special methods of drill and blast Bridge excavation

 Dredging is the process of excavating and removing sediments and debris from below water level, typically from the bottom of lakes, rivers, harbours etc Dredging

 To excavate the earth and to load the trucks  Capable of excavating all types of earth except hard rock  Size varies from 0.375m3 to 5m3.  Basics parts of power shovel including the track system, cabin, cables, rack, stick, boom foot-pin, saddle block, boom, boom point sheaves and bucket POWER SHOVEL/ EXCAVATOR

 Suitable for close range of work  Capable of digging very hard materials,  Can remove big sized boulders.  It is used in various types of jobs such as digging in gravel banks, clay pits, digging cuts in road works, road-side berms, etc. 19 Application

 Class of material  Depth of cutting  Angle of swing  Job condition  Management condition  Size of hauling units  Skill of the operator  Physical condition of the shovel 20 Factors affecting output

 Also known as hoe, back shovel and pull shovel  It is used to excavate below the natural surface on which it rests.  Generally used to excavate trenches, pits for basements and also for grading works, which requires precise control of depths.  The basic parts are boom, Jack boom, Boom foot drum, Boom sheave, Stick sheave, Stick, Bucket and Bucket sheave BACK HOE LOADER

 It is the most suitable machine for digging below the machine level, such as, trenches, footings, basements etc.  It can be efficiently used to dress or trim the surface avoiding the use of manual effort for dressing the excavated the surface. 22 Application

 The drag line is so name because of its prominent operation of dragging the bucket against the material to be dug.  Unlike the shovel, it has a long light crane boom and the bucket is loosely attached to the boom through cables.  Because of this construction, a dragline can dig and dump over larger distances than a shovel can do.  Drag lines are useful for digging below its track level and handling softer materials.  The basic parts of a drag line including the boom, hoist cable, drag cable, hoist chain, drag chain and bucket DRAG LINE

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 It is the most suitable machine for dragging softer material and below its track level  It is very useful for excavating trenches when the sides are permitted to establish their angle of repose without shoring.  It has long reaches.  It is mostly used in the excavation for canals and depositing on the embankment without hauling units. 25 Application

 This is so named due to resemblance of its bucket to a clam which is like a shell-fish with hinged double shell.  The front end is essentially a crane boom with a specially designed bucket loosely attached at the end through cables as in a drag line.  The capacity of a clam shell bucket is usually given in cubic meters.  The basic parts of clam shell bucket are the closing line, hoist line, sheaves, brackets, tagline, shell and hinge CLAM SHELL

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 Used for handling loose material such as crushed stone, sand, gravel, coal etc.  Main feature is vertical lifting of material from one location to another.  Mainly used for removing material from coffer dam, sewer main holes, well foundations etc. 28 Application

 Used for excavating trenches for laying pipelines, sewer, cables etc.  Operation is quick giving the required depth or width.  Two types of trenching machine wheel type, ladder type TRENCHING MACHINE

 Unique machine for digging and long-distance hauling of plough able materials.  self-operating machine  It is not dependent on other equipment.  Wheels of machine cause some compaction.  The basic parts of scrapers are the bowl, apron and tail gate or ejector SCRAPERS

 The heavy blade attached to the tractor pushes the material from one place to another.  The tractor can be of the crawler or the wheeled type.  Classification of bull dozer 1.Position of blades Bull dozers in which the blade perpendicular to the direction of movement Angle dozers in which the blade is set at an angle with the direction of movement BULL DOZER

2.Based on mountings Wheel mounted Crawler mounted 3.Based on the control Cable controlled Hydraulically controlled 32

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 For spreading the earth fill  For opening up pilot roads through mountainous and rocky terrains.  Clearing construction sites.  Maintaining haul roads  Clearing land from the trees and stumps  back-filling trenches at construction sites by dragging the earth from one place to another 34 Application

 The equipment used for transportation of material are known as hauling equipment or simply haulers.  Haulers may operate on the roadways or railways  It involve transportation of building materials, carriage and disposal of excavated earth haulage of heavy construction equipment. 35

 These are used for earth moving purpose.  The selection of the type of dump trucks for a specific job depend on the soil condition.  These are heavy duty trucks with strongly built body which is hinged on the truck chassis at the rear end and one side respectively, and can be fitted to the rear in the case of rear dump and to the hinged side in case of the side dump, through the action of hydraulic jacks.  These trucks are suitable for use in hauling wet clay, sand, gravel, quarry rocks etc Side/Rear Dump trucks

37 Side Dump Truck Rear Dump Truck

 These are similar to semi-trailers in which their front is supported on the rear of the hauling tractor and their rear is resting on their own wheels.  The body of the truck remains in the same position and the discharge of the material takes place through its bottom after opening of two longitudinal gates.  The gates are hinged to the side of the body.  These trucks are suitable for use in hauling free flowing material, such as, sand, gravel, dry earth, hard clay etc Bottom dump trucks

39 Bottom Dump Truck

 High speed pneumatic wheeled trucks  Short chasis  Strong bodies  Loading, hauling and dumping is done very fast as compared to other equipment  Suitable for short hauls on rough roads  Specially where a shuttle movement is required Dumpers

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Dewatering is the process of removal excess water from saturated soil. It is a necessary process when it comes to many construction projects, particularly when the construction is for underground projects

1. Sumps And Ditches 2. Shallow Well System 3. Deep Well System 4. Well Point System 5. Vacuum Method 6. Cement Grouting 7. Chemical Process 8. Freezing Process 9. Electro-Osmosis Method Factors such as the type of soil and the nature of the construction site will influence for selecting a dewatering method

 A sump is merely a hole in the ground from which water is being pumped for the purpose of removing water from the adjoining area.  They are used with ditches leading to them in large excavations. Up to maximum of 8m below pump installation level; for greater depths a submersible pump is required.  Shallow slopes may be required for unsupported excavations in silts and fine sands. Gravels and coarse sands are more suitable.  If there are existing foundations in the vicinity pumping may cause settlement of these foundations. Subsidence of adjacent ground and sloughing of the lower part of a slope (sloped pits) may occur Sumps and Ditches

 The sump should be preferably lined with a filter material which has grain size gradations in compatible with the filter rules. 46 Submersible Pump

 A hole of 30 cm diameter or more is bored into the ground to a depth not more than 10 m below the pump level. A strainer tube of 15 cm diameter is lowered in the bore hole having a casing tube.  A gravel filter is formed around the strainer tube by gradually removing the casing tube and simultaneously pouring the filter well so formed.  The suction pipe from a number of such wells may be connected to one common header connected to the pumping unit Shallow Well

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 Shallow wells can be installed with effective filters which can allow them to pump ‘clean’ water with much lower levels of suspended solids compared to sump pumping. This makes it easier to meet water quality limits at the discharge point.  Shallow wells, if installed to sufficient depth, can act as a form of pre-drainage dewatering, where groundwater levels are lowered in advance of excavation and can be held significantly below current dig levels. 49 Application

 This system is more suitable when the depth of excavation is more than the 16m or where artesian water is present.  15 to 16 cm diameter hole is bored and a casing with a large screen is provided. A submersible pump is installed near the bottom of the well Deep Well

 Deep well dewatering is normally suited to relatively deep excavations where permeability is between moderate (e.g. sands) to high (e.g. gravels).  Deep wells can be less effective is in low permeability soils. In these cases the well yields can be very low. Such low well yields can make it difficult to select suitable submersible pumps that can operate reliably and efficiently at low flow rates. 51 Application

 The main components of a well-point system are: 1.well points 2.Riser pipe 3.Swinger arm 4.Header pipe 5.pumps Well Point System

 Well points are for lowering water table by 5-6 m in soils with a coefficient of permeability between 10-4 to 10-6 m/sec.  The riser is surrounded by a coarse sand filter in order to facilitate the flow of water towards the well points. 53 Multi-Stage Well Point

 Installation is very rapid. The equipment is reasonably simple and cheap.  As water is filtered while removing from the ground, soil particles are not washed away. Hence, there is no danger of subsidence of the surrounding ground.  As the water is drawn away by well points from the excavation, the sides of excavation are stabilized and steeper side slopes can be permitted. 54 Advantages

 Single stage well point system is suitable for lowering water table by 5 to 6m only. For deeper excavations, where water table is to be lowered for a depth greater than 6 m, multi-stage well point system is required.  It is essential to continue pumping once it has been started until the excavation is complete. If it is stopped in between, it may prove to be disastrous.  In case of the ground consisting of stiff clay, gravel or boulders, well points are installed in drilled holes, which increases the installation cost. 55 Disadvantages

56 5. Vacuum System

 The material commonly used for grout include: Cement And Water Cement, Rock Flour and Water Cement, Clay and Water Cement, Clay, Sand and Water Asphalt Clay And Water Chemicals Cement Grouting

The desirable properties of chemical grouts:  It must be able to modify the properties of soil as desired  It may either increase the strength or decrease the permeability of soil  It must be cheap, non-toxic, non-explosive  It must be in the form of a liquid with low viscosity so that it can be readily placed in the soil  It must be non-corrosive, so that it can be handled with common pumps and piping  It must be possible to control the gel time by suitable means Chemical Grouting

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 It can be used for sealing narrow cracks of about 0.5 mm width  It become hard in cold as well as warm temperature  It can bond the moist as well as dry surface  It has practically the same viscosity as water and hence it can be injected into any soil and fine cracks into which the water can be injected 60 Advantages

61 8. GROUND FREEZING

 The freezing process is readily accomplished where other methods may be difficult or impossible.  The freezing does not affect the current water table. 62 Advantages Limitations  The area to be covered by this process should be as small as possible.  The freezing process is suited for work of comparatively short duration.

63 9. Electro-Osmosis Process

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65 Suitability of Different Methods