2. Stages of building construction
1. Preliminary works
2. Foundations
3. Ground floors
4. Frames and upper floors
5. Stairs
6. Roofs
7. Walls and partitions with doors and windows
8. Mechanical and electrical works
9. Internal and external wall, floor and ceiling finishes
10. External works
2
3. Topics
Site and soil investigation
Site clearance and setting out
Site facilities
Excavation and timbering
Site plant and equipment
Health and safety measures on site
Scaffolding
3
4. References
Chudley, R & Greeno, R 2005, Construction Technology
Part 1.1 Site Works and Setting Out
Part 1.4 Excavations and Timbering
Part 1.5 Scaffolding
Part 2.1 Trench and Basement Excavation
Chudley, R & Greeno, R 2006, Advanced Construction
Technology, Part 2 Plant and Equipment
Chudley, R & Greeno, R 2010, Building Construction
Handbook
Part 2 Site Works
Part 3 Builders Plant
Part 4 Substructure 4
5. Week 3 Lecture: Preliminary Works
Site & Soil Investigation
5
6. _site investigation__ is to collect systematically
and record all the necessary data which will be
needed or will help in the design and construction
processes of the proposed work.
The collected data should be presented in the form
of fully annotated and dimensioned plans and
sections.
Anything on adjacent sites which may affect the
proposed works or conversely anything
appertaining to the proposed works which may
affect an adjacent site should also be recorded.
6
8. Site investigation is all-embracing, taking into
account such factors as location, topography,
accessibility, space, existing services and any local
restrictions.
Soil investigation could be part of or separate from
the site investigation.
Soil investigation_ is a means of obtaining data
regarding the characteristics of subsoils by
providing samples for testing or providing a means
of access for visual inspection.
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9. Purposes of soil investigation:
To determine the suitability of site for the
proposed construction project.
To determine an adequate and economic
foundation design.
To determine the difficulties which may arise
during the construction process and period.
To determine the occurrence and/or cause of all
changes in subsoil conditions.
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10. During the soil investigation, soil samples should
be taken from positions on the site which are truly
representative of the area but are not taken from
the actual position of the proposed foundations.
Soil samples can be obtained as disturbed or
undisturbed samples.
10
11. __disturb soil sample___
These are soil samples obtained from trial pits and
boreholes.
The method of extraction disturbs the natural
structure of the subsoil.
__undisturb soil sample____
These are soil samples obtained using sampling shells.
The method of extraction preserves the natural
structure and properties of the subsoil.
This method of obtaining soil samples is suitable for
rock and clay subsoils only.
But difficulties can be experienced in trying to obtain
undisturbed soil samples in other types of subsoil. 11
13. The test results of
soil samples are
usually shown on a
drawing which gives
the location of each
sample and in the
form of a hatched
section.
As a general guide,
the cost of site and
soil investigation
should not exceed
1% of estimated
project costs.
13
14. The nature and bearing capacity of subsoils can be
determined by the following soil investigation
methods:
Trial pits
boreholes
14
15. Method chosen will depend on several factors:
Size of contract
Type of proposed foundation
Type of soil sample required
Type of subsoil which may be encounter
As a general guide, the most suitable methods in
terms of investigation depth are:
_trial pits_: small contracts where foundation
depths are not likely to exceed 3m;
_boreholes__: medium to large contracts with
foundations up to 30m deep.
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16. _trial pits__
The pits can be hand- or machine-excavated to a
plan size of 1.2 x 1.2m.
Subsoil can be visually examined in-situ on the
faces of the excavated pit, and samples taken for
further laboratory tests.
The spoil removed will provide disturbed samples
for testing purposes, whereas undisturbed samples
can be cut and extracted from the walls of the pit.
Suitable for dry ground which requires little or no
temporary support to sides of excavation.
For exploration of shallow depth up to 3m, this is
usually more economical than boreholes. 16
18. __boreholes____
These enable disturbed or undisturbed samples to
be removed for testing.
Disturbed samples can be obtained by using a
rotary flight auger fixed to a tripod .
Undisturbed samples can be obtained from
cohesive soils using 450mm long x 100mm
diameter sampling shells, which are driven into the
soil to collect the sample; upon removal the tube is
capped, labelled and sent off to laboratory for
testing.
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22. Week 3 Lecture: Preliminary Works
Site Clearance & Setting Out
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23. When a contractor is given possession of a
construction site, he will be provided with the site
layout plan and the detailed drawings necessary
for him to construct the building.
_site clearance_ shall be undertaken first, which
may involve the demolition of existing buildings,
grubbing out of bushes and trees, and removal of
soil to reduced levels.
Then the precise placing of a building on a
construction site is determined by _setting out__.
23
24. 1. The first task of setting out is to establish a
baseline from which the whole building can be
referred to.
2. A steel or linen tape (30m would be a suitable
length) can be used for on site measuring.
24
25. 3. After the baseline has been set out, marked and
checked, the main lines of building can be set
out by having each building corner being marked
with a timber peg fixed with nail and string.
25
26. 4. A check should now be made of the setting out
lines for right angles and correct lengths.
5. There are several methods of checking whether a
right angle has been established:
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_3-4-5 triangle
Theorem of pythagorus_
32. Before a foundation can be constructed, it is
necessary to undertake excavation and timbering.
32
33. Types of excavation
Excavation is carried out to remove earth to form a
cavity in the ground.
Excavations may be classified as shallow, medium
or deep as follows:
Shallow – up to 1.5m deep;
Medium – 1.5 – 3.0m deep;
Deep – over 3.0m deep.
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36. 2. __ reduce level excavation ____
Carried out below oversite level to form a level
surface on which to build.
Consists of cutting and filling operations.
The level to which the ground is reduced is called
the formation level.
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38. 3. __trench excavation____
Long and narrow
excavation primarily
for strip foundations,
ground beams and
buried services.
Excavation can be
carried out by hand or
mechanical plant.
Sides of excavation can
be battered or straight.
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43. Types of timbering
Timbering is the temporary supports to the sides
of excavation.
Sometimes called planking and strutting.
Purposes of timbering to sides of excavation:
To uphold the sides of excavation to avoid
collapse of sides.
To protect the labours while in the excavation.
To avoid the wasteful labour of constantly
clearing falling earth from the excavation
bottom.
43
44. The material most used for temporary support to
the sides of excavation is rough sawn timber.
The timbers used are struts fixed across the width
of trench, supporting walings and vertical sheeting.
Whichever system of timbering is used, there
should be as few struts fixed across the width of
trench as possible as these obstruct ease of working
in the trench.
Struts should be cut to fit tightly between walings
and secured with wedges so that they are not easily
knocked out of place.
44
46. Trench excavation & timbering
Long and narrow trenches in firm soil may be
excavated to the full depth by mechanical
excavators first, then enabling the support
timbering to be placed in one continuous
operation.
Weak and waterlogged ground must be supported
before excavation commences by driving timber
runners or steel trench sheeting to a position
below the formation level, or by a ____________
procedure.
46
47. In the drive and dig procedure, the runners can be
driven to a reasonable depth of approximately 1.5m
followed by an excavation cut of 1.2m and then the
operation repeated until the required level has been
reached.
This will make the driving of runners easier and
enable a smaller driving appliance to be used.
47
49. Plant and equipment available for use at a construction
site can be classified into: small powered equipment,
earth moving and excavation plant, transportation
plant and concreting plant.
The choice of site plant and equipment to be used in
any construction activity is a complex matter taking
into account many factors such as volume of soil
involved, nature of site and time elements.
At this stage, only the basic types of site plant for
excavation activities will be considered here.
On small contracts such as house extensions,
excavation is effectively carried out by hand, but on
large works it will be more economic to use some form
of plant. 49
51. _mechanical shovel___
Take off layers of soil in buckets.
It can be raised, lowered or tilted to deposit the earth
into a dumper and removed elsewhere on site.
__bulldozer_
Push the soil layer by layer to one side and pile it up
nearby.
It does not dig or lift out the soil.
__dumper___
This truck can perform many tasks on a building site,
including the movement of soil over short distances.
The body of dumper can dip forward and deposit the
soil in the required position.
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54. _backactor___
These machines are designed to excavate in a
backward motion and are suitable for bulk
excavation work.
These machines are available as cable rigged or
hydraulic excavators.
Cable rigged backactors are usually available
with larger bucket sizes and deeper digging
capacities than the hydraulic machines.
But hydraulic machines have a more positive
control and digging operation and are also easier
to operate.
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55. _face shovel___
These machines are designed to excavate
forward above their own wheel or track level and
are suitable for bulk excavation work.
In basement work, they will require a ramp
approach unless they are to be lifted out of the
excavation area by means of a crane.
Face shovels are available as cable rigged or
hydraulic machines.
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57. Week 3 Lecture: Preliminary Works
Health & Safety Measures on Site
57
58. Possible accidents during
the excavation & timbering
works:
Falls
Cave-ins
Drowning
Materials/equipments
falling into excavation
Damage of underground
services
Explosions
58
59. A suitable fence or barrier must be provided to the
sides of excavation.
Timber or other suitable material must be
provided and used to prevent danger from the fall
or dislodgement of materials forming the sides of
excavation.
Excavation support need to be installed or
supervised by adequately trained, suitably
knowledgeable and experienced personnel.
Prior to general access being given, an inspection
of excavation by a competent person (usually the
main contractor’s safety supervisor) must be made
to ensure that work can proceed safely. 59
62. Materials must not be placed near the edge of any
excavation, nor must plant be placed or moved
near excavation so that persons working in the
excavation are endangered.
For small pits, such as manholes and other limited
excavation, the void may be covered.
Underground services must be foreseen, located,
identified and assessed for risk to labours working
in excavation.
62
64. Scaffoldings are temporary working platforms
erected around the perimeter of a building or
structure to provide a safe working place at a height.
They are usually required when the working height
is 1.5m or more above the ground level.
Scaffolding can be of tubular steel, tubular
aluminium alloy, timber or bamboo.
There are TWO (2) basic forms of scaffolding
namely putlog scaffolds and independent scaffolds.
Special scaffolds are also available for use, such as
slung, suspended, truss-out and gantry scaffolds, as
well as the easy to erect system scaffolds.
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