Earthwork or Groundworks Module 2nd -BCT301 Building Construction Technology Course and Equipment Lecturer’s name: Saad Talaat BILBAS University: Erbil Polytechnic University College: Engineering Department: Civil #Building and Construction Technology

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Earthworks or Groundworks
o Earthworks
An embankment or other construction made of earth; especially one used as a field
fortification ,or the operations connected with excavations and embankments of earth, or a
work of art consisting of a portion of land modified by an artist as shown in Figure 8.
o Site investigation
To select a foundation from tables, or to design a foundation, it is necessary to calculate the
loads on the foundation and determine the nature of the subsoil, its bearing capacity.
Where the nature of the subsoil is known from geological surveys, adjacent building
work or trial pits or borings.
Figure 8: Earth Work

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o Site visit:
A visit to the site and its surroundings should always be made to record everything relevant
from a careful examination of the nature of the subsoil, vegetation, evidence of marshy
ground, signs of ground water, and flooding.
o Top Soil:
This layer of top soil, which is about 100 to 300 mm deep, is some times referred to as
vegetable top soil. It is loosely compacted, supports growing plant life and is unsatisfactory
as a foundation. It should be stripped from the site of buildings because of its poor bearing
strengths and its ability to retain moisture and support vegetation which might adversely
affect the health of occupants of buildings as presented in Figure 9
Figure 9: Top Soil

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o Sub Soil:
Subsoil is the general term for soil below the top soil. It is unusual for a subsoil to consist of
gravel, sand or clay by itself as shown in Figure 10
Figure 10: Sub Soil

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o Excavation
As shown in Figure 10, after the site has been cleared and the approximate location of the
corners of the building have been established , excavation can be begun depending on the soil
type, slope, complexity of the building, the availability of equipment, a number of machines,
ranging from road grader to backhoe to bulldozer, may be used. If the house is to be built on a
rocky site, a blasting contractor might also be employed. The excavator first removes from the
surface all soil containing organic matter with in footprint of the house. This mixture of top
soil and plant material (grass and small roots) is stockpiled for future use a backfill.
Figure 10: Excavation Work

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o Volume of H:
• H > 0.25m (avoiding top soil) as presented in Figure 11
• Bearing: the foundation should bear on natural soil.
• At depth near, so offer from frost action (H>=0.5m).
o Bearing:
• B.C = 10 --- 15 Ton/m2
(KPa)
• If the soil volume under the foundation is changed uniformly so that no damage would be
caused to the building.
• But after raining seasons, the soil at top tends to become much water than the soil under
foundation. Therefore, after raining the soil at exterior expanded more than at the under
foundation and thus when the sun shines the soil at exterior dries out more quickly and
shrinks more than the soil at under foundation
• The concrete foundation tiles slightly.
• Cracking will be happened on walls as shown in Figure 12
Figure 11: Typical Foundation
Figure 12:
Wall cracking

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o Bulk Fill
It is all that material placed in the fill, from the ground surface after clearing and removing of
top soil as presented in Figure 13
.
Figure 13: Bulk Fill Earthwork

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o Borrow
It is excavation and importing from outside the construction batter limits as shown in
Figure 14
.
Figure 14: Borrow Earthworks
o Rock
It is any igneous, sedimentary, or metamorphic stone which is solidly bonded or cemented
together and which occurs in masses, ledges, seams or layers as presented in Figure 15
Figure 15: Borrow Earthworks

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o Cut
It is excavation within the construction scope as exhibited in Figure 16.
Figure 16: Cutting Earthworks

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o Granular Fill Material
It is material which has been placed in the fill and which contains less than 35% passing a
75μm sieve and has a sand equivalent greater than no. 20 as shown in Figure 17
Figure 17: Filling Earthworks

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o Overbreak
It is the excavated material removed by contracting operations from outside the construction
properties, but not authorized as a borrow such as explained in Figure 18
o Side Drain
It is an open drainage excavation often at the toe of a fill earthwork as discovered in Figure 19
Figure 18: Filling Earthworks
Figure 19: Side drain Earthworks

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o Subgrade
It is defined as that layer of material at the top 1.0 m of the construction measured down from
the underside of the sub-base course. It may be filled or insitue material as mentioned in Figure
20
o Surface Water Channel
It is a water channel formed at the subgrade surface at the edge of the road as shown in Figure
21.
Figure 20: Subgrade Earthworks
Figure 21: surface Water Channel

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Nominal Maximum Particle Size Maximum Layer Thickness
Up to 100 mm 200 mm
100 mm to 200 mm 1.5 times the 85 percentile size
Over 200 mm Refer contract documents where applicable
In term of Layer thickness, the maximum thickness of each layer of fill before
compaction shall be in accordance with Tables 1 below unless field trials show, to the
satisfaction of the Engineer that the specified compaction is obtained with thicker
layers.
Table 1: Bulk Fill

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o Shoring and Timbering
The length, breadth and depth of trench should be as per drawing and design given in the
map. Where the soil is wet or cohesion less the side slopes are supported by the use of cross
bars and side shutters (planks) in order to prevent the collapse of the trench. This is called
shoring and timbering. The details of shoring and timbering are given in Figures 23 and 24.
Figure 22: Loose Timbering

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Figure 23: Close timbering
o Unit of measurement of Earthwork
The unit of measurement of earth work is cubic meter (meter3). If the length of trench = 1 m,
breadth 1 m and depth 1 m then the total earthwork is 1 m × 1 m × 1 m = 1 cub meter.
Vol. of earth work (length × breadth × depth)
If the shape of the trench is trapezoidal
Vol. of earth work =
𝑩𝟏 𝑩𝟐
𝟐
x Height x Length

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o Frost action:
• Evasion of the soil due to freezing of the water in the soil near the natural ground level.
• Compact granular subsoil does not suffer volume change.
• The water in soil more than (0.5m) below N.G.L. does not usually freeze.
• Freezing of the water in the soil near the natural ground level.
• Granular subsoil does not suffer volume change.
o Temporary timber support:
It is used to uphold the sides of the excavation to avoid collapse of the trenches sides‘. Also,
nature of the soil being excavated will allocate at what depth of the trench timber support to
the sides should use.
• Soft granular soil readily crumbles and the sides of trenches in such soil may have to be
supported for the full depth of the trenches.
• Clay soil does not usually require support up to 1.5m (dry weather).
Case (1):
Deep Trenches in Clay Soil.

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Case 2:
Soft Soil (Loam).
Case 3:
Dry Granular Soil (sand)

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o Base of the Trench
• The base of the trench should be made flat and all loose soil should be removed from
it.
• If by mistake the depth of the trench becomes more than the required depth, it should
not be filled by loose soil rather it should be filled with lean concrete such as 1:3:6 or
1: 4 : 8 or 1 : 5: 10 and made flat.
• If it is required to construct a soil embankment, at least 10% more soil should be
added for instance; if the designed height of the embankment is 6.0 m, the
embankment of 6.6 m height should be constructed initially to allow for the
settlement of soil at later stage.
so, embankment height = 6+0.6
= 6.6m
• In case of deep cutting or filling a side slope of 1 : 1 or 1 : 2 (i.e. 1 vertical and 2
horizontal) is usually maintained.
• If it is required to put new soil over old soil, Benching is required to be done so that a
perfect bonding between old and new soil is achieved. Benching means construction
of steps.
• Grass should be planted on the slope to check the soil erosion; in order to maintain
the slope of the embankment.
Figure 25: Trench Side Slope

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Figure 26: Lean Concrete Trench Base
Figure 27: Grass planted on the side slope to check the soil erosion
Figure 28: Stabilization and benching of Cover Soil
Figure 29: Stabilization and benching of Cover Soil

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Also, apart from the above earthwork is required to be carried out in the construction of roads.
During construction of roads two types of situation can arise i.e. it may require either cutting
or filling. During excavation we may get different types of soil layers. For this a reformed line
is required to be made for controlling the soil texture and depth of the road/embankment as
presented in Figures 30.
Figure 30: Embankment Construction Layers

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Furthermore; Figure 31 above aids in explaining the cutting or filling which has been done
as per the drawing. Catch water drains are made on the sides of the cutting which takes out
and run off water from road surface.
Figure 31: Cross section of a road

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o WBM Road
It is coming from Water Bound Macadam. The word Macadam comes from the name of
Scottish Engineer JOHN L. MACADAM. So, the WBM is the pavement base course made of
crushed or broken aggregates which they are mechanically interlocked by rolling, and voids
filled by screening and binding material with the assistance of water as shown in Figure 32
below.
o Materials to be used in WBN road
• Crushed trap rock – most suitable
• Crushed slag
• Burnt Brick bats
• Aggregate
• Laterite
• Screenings to be used as filler material
o Salient Features of WBM Roads
• Low cost
• Thickness range: 8cm to 30cm
• Camber: 2.5% to 3% or 1:36 to 1:48
• Surface is better than earthen road, but rough as compared to bituminous or
concrete roads
• Can be used as a Base Course for Bituminous or concrete roads