Substructure

Question 1

What are the components of concrete?

Answer 1

Cement
Aggregate (fine/course)
Water

Question 2

Why is concrete reinforced?

Answer 2

Strong in compression, weak in tension

Tensile forces will pull concrete apart concrete from bottom

Question 3

What is and are the components of a strip foundation?

Answer 3

Suitable for most subsoils
Low to medium rise buildings (domestic)
Foundation can be reinforced

Question 4

What is a raft foundation? Build up and what is it used for?

Answer 4

Covers entire footprin, usually 150-300mm thick but can be thicker
Used when ground conditions are poor
Spread load from walls and columns

screed
waterproof membrane
Concrete raft
concrete blinding layer
hardcore layer

Question 5

What is a pile cap?

Answer 5

Links piles together through an RC cap

They can be linked through ground beams

Question 6

What is the construction sequence of a pile cap

Answer 6

Excavation and disposal
Formwork
Reinforcement
Concrete pour

Question 7

What is sheet piling?

Answer 7

Steel sheet driven into the ground

Excavation performed once the perimeter is formed

Question 8

What is a secant piled wall?

Answer 8

A secant pile wall consists of overlapping (secant) piles to form structural or cutoff walls and achieve the required water tightness.

Stronger concrete used for secondary pile 10N/mm)
Cost effective solution to diaphragm wall

Question 9

What is the difference between displacement and replacement piling?

Answer 9

Displacement driven into the ground without excavation

Replacement replacing existing soil e.g. CFA piling

Question 10

What is a retaining wall?

Answer 10

Used to retain or prevent material collapsing

Question 11

What is a ground beam?

Answer 11

Links piles together for rigidness

Provides a platform for the superstructure

Question 12

What is a ground bearing and suspended slab?

Answer 12

Ground bearing: Slab that is supported by soil
Suspended floor slab: Supported on beams/piles

Question 13

How are earthworks supported and why?

Answer 13

Temporary wooden supports
Stop displacement or caving in of excavation

Question 14

Describe the different ways of dealing with ground water in excavations?

Answer 14

Temporary or Permanent
Permanant; impermeable barrier stops flow of water to the ground
Temporary; lower water table through subsoil drainage techniques (sump pumps)

Question 15

How was the substructure houses for Eastfields water-proofed?

Answer 15

Damp proof membrane

Question 16

Explain activities involved when piling?

Answer 16

Measure in line with Section 1 of NRM1

Forming pile mat
Mobilisation/moving of pile rig
Pouring insitu RC piles
Cutting top of piles
Pile Caps
Pile testing
Pile casings if applicable

Question 17

How would you increase waterproofing to concrete?

Answer 17

Waterproofing additive

Waterproof membranes

Question 18

Why use secant wall piling and not contiguous?

Answer 18

Secant wall piling generally reduces the chance of water entry into the basement.

Question 19

How do you construct a crane?

Answer 19

Mini Piles
Excavation
In Situ Concrete
Reinforcement
Erection of crane using mobile crane

Question 20

Why would you use piling?

Answer 20

Subsoil is not strong enough to take the load bearing capacity of the superstructure.