Settlement of bored piles

Question 1

What is the key geotechnical design criteria for foundation engineering?

Answer 1

GROUND DISPLACEMENTS

Question 2

In the non-linear model for settlement, in what range should TAUmob/Cu be used (regarding a typical triaxial test)?

Answer 2

0.2 < X < 0.8 - moderate strain range

Question 3

What assumptions are made in the calculation for soil settlement? (4)

Answer 3

1) Pile is assumed to be rigid
2) There is no slip between the soil-pile interface
3) Concentric circles of influence around the pile shaft, ignoring resistance at the toe
4) M is assumed constant down the length of the pile, average value taken half way down

Question 4

What is M?

Answer 4

Mobilisation factor

Question 5

How do you arrive at the soil settlement equation?

Answer 5

1) Rearrange the mobilisation factor equation for gamma
2) Sub in the taumob mini equation
3) integrate between r0 and infinity wrt r0 for downward displacement of pile, w
4) for the settlement ratio - w/r or w/D

Question 6

What is the pile compressibility equation?

Answer 6

w = Qh/2 X 4/piD^2 X L/Ec

Question 7

What is the head load transferred through?

At the … factored down by…

Answer 7

Shaft friction at the average cu surrounding the pile, factored down by M.

Question 8

What is the equation for head load?

Answer 8

Cu(bar)/M X piDL

Avrg UD shear strength factored down by M, multiplied by the area.

Question 9

What is the major variable in these calcs?

Answer 9

M, mobilisation factor

Question 10

F = aM, what value of F gives a lower realistic limit for design, dictating a and M values

Answer 10

1 - lumped FoS