Substructure- Foundations

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 footprint
Used when ground conditions are poor
RC to load bearing walls

Question 5

What is an interlocking pile?

Answer 5

Similar to contig pile, gap filled with soft pile
Typically not reinforced, weak conc mix (c40)
Reduces water ingress
Cement/bentonite mix (1N/mm2)

Question 6

What is a secant piled wall?

Answer 6

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

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 the difference between displacement and replacement piling?

Answer 8

Displacement driven into the ground without excavation

Replacement is CFA piling

Question 9

What is a retaining wall?

Answer 9

Used to retain or prevent material collapsing

Question 10

What is a pile cap?

Answer 10

Links piles together through an RC cap

They can be linked through ground beams

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 slab?

Answer 12

Typically the GF slab
Reinforced
Commonly supported by piles, caps and beams

Question 13

How are earthworks supported and why?

Answer 13

o Temporary wooden supports
o Stop displacement or caving in of excavation
o Open or closed

Question 14

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

Answer 14

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

Question 15

How was the substructure in the last question 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

Question 21

Basement grades

Answer 21

Grade 1 – Some water seepage and damp is tolerable depending on the intended use.
Grade 2 – No water penetration is acceptable
Grade 3 – No dampness or water penetration is acceptable