CONSTRUCTION TECHNOLOGY

Question 1

What are the different types of foundations?

Answer 1

Strip, pile, raft and pad

Question 2

What are the advantages of strip foundations?

Answer 2

Useful to transfer continuous loads
good for clays and seasonally changing soils
useful where ground conditions are good

Question 3

What are the disadvantages of strip foundations?

Answer 3

Not conducive for taller buildings of a heavier load
Due to excavation and curing time it takes a lot of time
Requires a lot of concrete so can be high cost
Complicated formwork

Question 4

What are the advantages of pile foundations?

Answer 4

Useful for large structures
Well suited for very poor ground conditions
CFA is as quick as excavation and consecutive pouring

Question 5

What are the disadvantages of pile foundations?

Answer 5

Expensive
Can be noisy and intrusive
Plant hire required is additional costs
Needs piling mat and rig
Bored piles takes a long time
Transferring pre-cast piles is difficult

Question 6

What are the advantages of raft foundations?

Answer 6

Good for poor ground conditions and small buildings

Question 7

What are the disadvantages of raft foundations?

Answer 7

Not suitable for large loads
Requires lots of concrete
Requires sturdy formwork

Question 8

What are the advantages of precast concrete?

Answer 8

Better QAQC in the factory
reduced time on site and associated preliminaries cost
Reduces the time you need to wait for it to cure on site, better programme

Question 9

What is substructure?

Answer 9

All elements of work that are undertaken below the damp proof course that provides the basis for the superstructure to be constructed upon (Foundations)

Question 10

What is the purpose of soil investigation and ground conditions surveys?

Answer 10

To determine the suitability of the site for the proposed works and determine and adequate and economically viable foundation design.
The investigation should determine the potential difficulties associated with the ground conditions (which may need to be allowed for in the cost plan).
Assist with identifying a suitable foundation solution.

Question 11

What are the main components of concrete?

Answer 11

Cement
Aggregate (natural rock, crushed stone, gravel)
Water

Question 12

What is a borehole?

Answer 12

This can be used to investigate soil or for a geothermal heating solutions.
Boreholes are the most suitable method of soil investigation when foundations are over 3m deep.
Geothermal boreholes are permanent boreholes that use the Earth’s natural heat to raise the temperature of circulated water.
This is a closed system and can be used to heat the building above which is adopted as a sustainable technology.

Question 13

What are piles?

Answer 13

A series of columns constructed or inserted into the ground to transmit the load of a structure to a lower level of subsoil.
They are used where no suitable foundations conditions are present nearer to ground level or in areas where there is a high water table.

Question 14

What are the different types of piles?

Answer 14

Sheet
Secant
Bored
Pre-cast

Question 15

Sheet Piles

Answer 15

A deep trench is excavated and concrete is poured in situ.
The piles can be used to form basement walls or act as retaining walls.

Question 16

Secant Piles

Answer 16

Interlocking piles of different hardness and diameters, bored to provide a combination of foundations and basement walls.
They support in providing a waterproof structure and are often seen when a top down construction method is used.

Question 17

Bored Piles

Answer 17

An auger is used to excavate the soil and then concrete is poured in once complete.

Question 18

Pre-cast Piles

Answer 18

Piles are hammered into the ground. This is not often favoured due to the high noise levels associated with installation and the lack of flexibility in terms of depth required.

Question 19

What are the different ways that piles transfer their load to the surrounding ground?

Answer 19

End bearing piles: transfer load through low bearing capacity soil to a strong stratum such as rock/dense sand
Friction piles: bear on frictional resistance between their outer surface and the soil in contact.
Settlement reducing piles: incorporated beneath the central part of a raft foundation in order to reduce differential settlement to an acceptable level.
Tension piles: resist uplifting forces that might otherwise cause the structure to be extracted from the ground due to uplifting forces such as hydrostatic pressure, seismic activity or overturning movement.