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Introduction:

A building is a man-made structure with a roof and walls standing more or less permanently in one place,

such as a house or factory. Buildings come in a variety of shapes, sizes and functions, and have been

adapted throughout history for a wide number of factors, from building materials available, to weather

conditions, to land prices, ground conditions, specific uses and aesthetic reasons. To better understand the

term building compare the list of nonbuilding structures.

Earthworks are engineering works created through moving or processing of part of earth surface involving

the quantities of soils, rocks and other sediments.

If we apply the earthworks in building construction there are three involved Components:

Foundation

Water System (such as groundwater, drainage etc.)

Basement

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Earthworks in Buildings

Components of the Building:

1. Superstructure

Construction above the basement or foundation

supported by an infrastructure which in turn is

supported by the substructure.

2. Substructure

Basic framework or foundation that supports a

superstructure, and is supported by an

infrastructure.

3. Foundation

The foundations of the building transfer the

weight of the building to the ground. While

'foundation' is a general word, normally, every

building has a number of individual

foundations, commonly called footings.

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Process and parts of Building Construction ( Superstructure and Substructure)

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Earthworks in buildings

Foundation

Major component of building earthworks. The structure, that transmits the load of the building to the soil.

Choosing a kind of foundation depends on:

the ground conditions the groundwater conditions the site, the environment (the buildings nearby) the structure of our building

Requirements:

structural requirements: safe, be able to carry the load of the building constructional requirements: schedule, minimal resources, minimal cost

Foundation Components

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Steps in establishing Foundation

1. Site Preparation

Remove trees and any debris Remove top soil (4-6 below surface)

2. Site Layout

Ensure lot lines are known & setbacks are complete Layout building perimeter Use batter boards Establish building corners & building perimeter Use surveying instruments

3. Excavation Excavate foundation along line created by batter boards

Excavate remainder of soil inside perimeter

Dont excavate inside soil if slab on grade

If deep foundation, taper edges to prevent collapse

If soil unstable, or very deep - use shoring

4. Pour Footings

Construct formwork (if required)

Install reinforcement (rebar) for footings

(protrudes above footing to tie-into foundation wall)

Pour concrete footings

Smooth / finish surface

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Types of Foundation:

1. Shallow Foundation

also called spread footings or open footings. The 'open' refers to the fact that the foundations

are made by first excavating all the earth till the bottom of the footing, and then constructing

the footing.

During the early stages of work, the entire footing is visible to the eye, and is therefore called

an open foundation.

The idea is that each footing takes the concentrated load of the column and spreads it out over

a large area, so that the actual weight on the soil does not exceed the safe bearing capacity of

the soil.

Several kinds of shallow footings

a. Individual footings

Individual footings are one of the most simple and common types of foundations. These are used

when the load of the building is carried by columns. Usually, each column will have its own footing.

The footing is just a square or rectangular pad of concrete on which the column sits. To get a very

rough idea of the size of the footing, the engineer will take the total load on the column and divide it

by the safe bearing capacity (SBC) of the soil.

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c. Raft Foundations Raft Foundations, also called Mat Foundations, are most often used when basements are to be constructed. In a raft, the entire basement floor slab acts as the foundation; the weight of the building is spread evenly over the entire footprint of the building. It is called a raft because the building is like a vessel that 'floats' in a sea of soil.

Mat Foundations are used where the soil is week, and therefore building loads have to be spread over a large area, or where columns are closely spaced, which means that if individual footings were used, they would touch each other.

b. Strip footings

Strip footings are commonly found in

load-bearing masonry construction,

and act as a long strip that supports

the weight of an entire wall. These

are used where the building loads are

carried by entire walls rather than

isolated columns, such as in older

buildings made of masonry.

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2. Deep Foundations

The load-bearing layer is in deeper location

The loads of the building are too heavy

Kinds of Deep Foundation

a. Pile Foundation

A pile is basically a long cylinder of a strong material such as concrete that is pushed into the

ground so that structures can be supported on top of it.

Pile Materials

Steel; H- piles, Steel pipe

Concrete; Site cast or Precast

Wood; Timber

Composite

Pile foundations are used in the following

situations:

1. When there is a layer of weak soil at the surface.

This layer cannot support the weight of the

building, so the loads of the building have to

bypass this layer and be transferred to the layer

of stronger soil or rock that is below the weak

layer.

2. When a building has very heavy, concentrated

loads, such as in a high rise structure.

Pile foundations are capable of taking higher

loads than spread footings.

Top View of the Materials

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There are two types of pile foundations, each of which works in its own way.

Pile Construction:

End Bearing Piles In end bearing piles, the bottom end of the pile rests on a layer of especially strong soil or rock. The load of the building is transferred through the pile onto the strong layer. In a sense, this pile acts like a column. The key principle is that the bottom end rests on the surface which is the intersection of a weak and strong layer. The load therefore bypasses the weak layer and is safely transferred to the strong layer. Friction Piles Friction piles work on a different principle. The pile transfers the load of the building to the soil across the full height of the pile, by friction. In other words, the entire surface of the pile, which is cylindrical in shape, works to transfer the forces to the soil.

A. CFA technology

Drilling continuously until planned depth

(using guiding tube if necessary) Placing the concrete and removing

the drill Placing reinforcement (vibration)

(CFA= Continuous Flight Auger)

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b. Slurry walls

A deep, narrow trench filled with

concrete (and reinforcement)

Functions

Retaining wall during excavation

(can be watertight)

Foundation

Wall of the basement

B. Soil-Mec technology

Boring until planned depth (using a guiding tube)

Using bentonite mud (slurry) under the groundwater level

Placing reinforcement Placing the concrete and removing the

guiding tube

C.Franki technology (bulb pile or compacted concrete

pile)

Filling concrete in a steel pipe (creating a plug)

Pushing down the pipe using a heavy drop hammer

Fastening the pipe and creating the foot Placing the concrete and compacting while

removing the pipe (reinforcing)

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Excavation

In general, excavation means to loosen and .take out materials leaving space above or below ground.

Sometimes in civil engineering term earthwork is used which include backfilling with new or original

materials to voids, spreading and levelling over an area.

Excavation and earthmoving plants

Advantages of using mechanical plant in excavation :

a) work done quicker,

b) avoid dangerous condition of work by human workers, say, existence of ground water or collapse of soil,

c) achieve greater depth,

d) use fewer manpower and work done in lower cost (for larger scale work only)

Disadvantages

a) involve larger running and maintenance costs,

b) require a larger operating area,

c) access provision to working area,

d) less flexible in work planning,

e) idling time increase cost of work

Excavation in most situations nowadays is done by mechanical means. However, the exact method to be adopted still depends upon a number of factors:

1. Nature of subsoil affect type of machine used and the necessity of soil protection.

2. Size of excavation affect type of machine used and method to excavate.

3. Scale of work large volume of excavation may involve complicated phasing arrangement and work

planning

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4. Ground water condition affect degree of protection (watertight sheet piling or dewatering may

required.)

5. Surrounding condition impose certain restrictions and precautions (eg. diversion of a government

drain, or underpinning work to the nearby building foundation)

Deep excavation

Deep excavation, unlike a shallow one, often requires to protect the sides of cut using

suitable support. Besides, the problem of ground water cannot be avoided. There are methods

to overcome this, such as:

1. Dumpling method

This is used where there are buildings or street in the proximity. The method is to construct a

series of retaining wall in trench, section by section, around the site perimeter ,leaving a

centre Called "dumpling"

2. Diaphragm walling

This method need to construct a R.C. retaining wall along the area of work. Because the wall

is designed to reach very great depth, mechanical excavating method is employed. Typical

sequence of work includes:

a. Construct a guide wall guide wall is two parallel concrete beams running as a guide to the

clamshell which is used for the excavation of the diaphragm wall.

b. Excavation for the diaphragm wall In normal soil conditions excavation is done using a

clamshell or grab suspended by cables to a crane. The grab can easily chisel boulder in soil

due to its weight.

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c. Excavation support excavation for the diaphragm wall produces a vertical strip in soil which can

collapse easily. Bentonite slurry is used to protect the sides of soil. Bontonite is a naturally

occurring clay which, when added to water, forms an impervious cake-like slurry with very large

viscosity. The slurry will produce a great lateral pressure sufficient enough to retain the vertical soil.

d. Reinforcement reinforcement is inserted in form of a steel cage, but may require to lap and

extend to the required length.

e. Concreting - concreting is done using tremie. As Concrete being poured down, bontonite will be

displaced due to its density is lower than concrete. Bontonite is then collected and reuse. Usually

compaction for concrete is not required for the weight of the bontonite will drive most of the air

voids in concrete.

Joining design for the diaphragm wall Diaphragm walling cannot be constructed continually for a

very long section due to tremendous soil pressure. The wall is usually constructed in alternative

section. Two stop end tubes will be placed at the ends of the excavated trench before concreting. The

tubes are withdrawn at the same time of concreting so that a semi-circular end section is formed. Wall

sections of this type are built alternatively leaving an intermediate section in between .

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Cofferdams

A cofferdam may be defined as a temporary box structure constructed in earth or water to exclude soil or

water from a construction area, such as for foundation or basement works.

Use of cofferdam suitable for excavation of larger scale can be of :

a) Sheet pile cofferdam Also known as single skin cofferdam. Interlocking type steel sheet pile is used

and can use for excavation up to 15m. Sheet pile in this case acts as a cantilever member to support the

soil therefore adequate depth of pi le or suitable toe treatment may be required. In addition, cofferdams are

need to be braced and strutted or anchored using tie rods or ground anchors.

b) Double skin cofferdam This works similarly like the sheet pile to form a diaphragm. However, the

diaphragm is double-skinned using two parallel rows of sheet pile with a filling material placed in the void

between. This creates somewhat a gravity retaining structure and increase the ability to counteract the soil

behind. However, more working space is required.

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Sheet Steel Piling

Steel, amongst other materials such as timber, is most effective to be used as sheet pile due to its high

tensile as well as their interlocking ability. It can be used as timbering to excavation in soft and/or

waterlogged soils especially in congested site where there is no enough space for complicated shoring.

Ground anchor

Ground anchor is basically a pre-stressing tendon embedded and anchored into soil or rock to provide

resistance to structural movements by a tying back" principle.

Common applications are :

1. General slope stabilization

2. Tying back/stabilizing a retaining structure

3. Tying back/stabilizing for diaphragm walls, but for a temporary nature during excavation

4. Tying back the entire building from up possible uplifting

Ground anchor can be classified into:

1. Rock anchor for anchorage in rock

2. Injection anchor suitable for most cohesive and non-cohesive soils

Method to form a ground anchor

A hole is predrilled on soil or rock in position carefully calculated. For rock anchor, an anchor bar with

expanded sleeves at the end is inserted into the hole. A dense high strength grout is injected over a

required length to develop sufficient resistance to hold the bar when it is stressed. Stressing is by hydraulic

mean and when the stress is developed, the head of the bar is hold by an end plate and nut.

For injection anchor, a hole should be bored usually with an expanded end to increase anchorage ability.

The pre-stressing bar is placed into the bore hole and pressure grouted over the anchorage length.

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Earthwork in Basements:

CONSTRUCITON OF BASEMENT USING TRADITIONAL METHODS

Construction of basement is difficult for it must be carried out below deep ground in adverse condition such

as existence of ground water, muddiness or limited working space. Besides, works are needed to be done

amidst layers of props, struts, walings and shores, which cannot be removed until the permanent works are

completed and capable of carrying the final loads. For each case of basement construction, the method of

soil support, sub-soil condition, structure of the basement as well as the layout requirement of the entire

building must be taken into consideration before designing the method of works.

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Method of constructing ordinary basement

One of the most effective methods to construct ordinary basement is by the use of diaphragm wall or sheet

pile wall (cut-off) which serves as a retaining structure during excavation and as the sides of the basement

walls. When the central soil is removed during excavation, the cut-off wall should be properly supported for

works. Below are some method suggested.

1. Use of lattice beams

A series of lattice beams or steel trusses

are installed so that they span between the

top of opposite diaphragm walls enabling

them to act as propped cantilevers. The russ

trusses can be removed after the internal

floors have been constructed and

receiving all the lateral forces from soil.

2. Use of Ground Anchors

Diaphragm walls are exposed by carrying out

the excavation in stages and ground anchors

are provided to stabilize the walls as the works

proceeds. This method is most effective for

basement of very large span or without

intermediate floors as lateral support

Basement Excavation Support using Lattice Truss

Basement Excavation Support using Ground Anchors

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3. Construct floor slab as support floor slab as support (top-down method)

After the perimeter diaphragm walls

have been constructed, the ground

floor slab and beams are cast

providing tip edge lateral support to

the walls. An opening is left in the slab

for labours, material or plant as access

to continue excavation to the lower

stages. This is repeated until the

required depth is reached.

4. cast the centre basement slab to support struts

Centre area between the diaphragm walls

can be excavated leaving an earth berm

around the perimeter to support the walls

whilst the lowest basement floor in centre

can be constructed. Slots to accommodate raking struts acting

between the wall face and the floor slab

are cut into the berm. Final excavation and

construction of the remaining of the

basement can take place in stages around

the raking struts.

Basement Excavation Support using Ground floor slab

(top-down method)

Basement Excavation Support using Shore or Strut

from a Central Basement Slab cast in advance phases

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Waterproofing the basement

A water-tighted basement wall is an essential element to waterproof a basement. |However, due to the

basement walls are often constructed under complicated phases to match with the excavation sequences

and this may increase the possibility of leaking, therefore, careful construction joining design is essential to

ensure the basement structure is perfectly water-proved. Very often the providing of water stops into these

joints is helpful. However, the most widely used method to water-proof a basement is to provide a cavity to

the wall of the basement (by building a skin wall to the sides). The ground water leaks into the basement

can then be collected through concealed channel to a sump pit and remove by pumps.

Earthworks in a Water System

The spacing between drains will vary between 10m for

clay soils to 50m for sand. Subsurface drains are usually

formed from buttjoined clay pipes laid in narrow

trenches. In cases where it is desirable to catch water

running on the surface, the trench is back-filled nearly to

the top with rubble either continuously along the trench

or in pockets. A trench filled with rubble or broken stone

will provide passage for water and is effective in dealing

with flows on the surface. Pipes and trenches belonging

to the main site drainage system may cause uneven

settling if allowed to pass close to or under buildings.

Where needed a separate drain, that surround the

building and installed not deeper than the footing, is

used to drain the foundation trench.

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References

http://cee.engr.ucdavis.edu/faculty/boulanger/

http://en.wikipedia.org/wiki/Foundation_(engineering)

http://www.foundationengineering.info/photo_galleries/08/footing_construction/

www.wikipedia.org

http://www.wikihow.com/ How to build a concrete foundation in 7 steps/

Civil Engineering Construction by J.M. Antill, Paul Ryan and G.R. Easton (McGraw Hill 1988)

Civil Engineering Technology by B.G. Fletcher and S.A. Lavan; (Butterworths 1982);

Introduction to Civil Engineering Construction by Roy Holmes (College of Estate Management, 1996)