mod6 Flashcards
1
Q
why do we use deep foundations
A
- soil at the surface is soft
- large horizontal loads present on uplift
- scour can occur
2
Q
end-bearing pile
A
- pile derives much of its carrying capacity from the resistance of the stratum at the toe of the pile
- bearing stratum is hard and relatively impenetrable material, such as rock or very dense sand or gravel
3
Q
friction pile
A
- pile does not reach an impenetrable stratum
- derives its carrying capacity partly from the end-bearing and partly from skin friction between the pile shaft and surrounding soil
4
Q
displacement pile
A
- pushes soil out radially and down vertically when it is installed
- usually leads to high horizontal stresses in the soil acting on the pile shaft, improving the shaft resistance
5
Q
examples of displacement piles
A
- driven piles
- driven and cast-in-place piles
- jacked or pressed-in piles
6
Q
non-diplacement pile
A
- constructed by boring a hole in the ground and filling with concrete, reinforced with steel reinforcing if on-shore or by a steel tube or “insert pile” if offshore
7
Q
examples of non-displacement piles
A
- bored and cast-in-place piles
- concrete or grout intruded piles
8
Q
axial capacity
A
arises from base and shaft resistanc
9
Q
lateral capacity
A
arises from horizontal soil pressure acting along the shaft
10
Q
“friction fatigue”
A
for displacement piles
- lower shear stresses in the top of the pile where soil has undergone most shearing than towards the tip
11
Q
Horizontal pile loads may be due to:
A
- wind
- wave action
- vehicle braking and acceleration
- soil loads
12
Q
4 main factors on selection of pile types
A
- location
- ground conditions
- durabilty
- cost
13
Q
piles for water based works
A
- driven piles
- driven and cast-in-place piles
14
Q
piles for moderate land, unhampered site
A
- bored piles
- driven and cast-in-place piles
15
Q
piles for land with proximate structures
A
- bored and cast-in-place piles
- jacket piles
