Question

A 6 m deep slope is going to be excavated in a deep soil deposit. The geometry of the slope is shown in
the following figure. Assume. The soil has the following properties:
t = 20 kN/m3, cu = 20 kPa,  = 5o
Water table is well below the toe of the embankment.
(a) Calculate the slope batter angle, , for which slope failure would occur.
(b) Assume a slope batter angle of  ranging from 40o to 60o with an incremental step of 2.5o.
Accordingly, determine the factor of safety for this slope.
(c) Plot the factor of safety against the slope batter angle.
(d) If the water table raises to a level 2 m above the toe of the slope, discuss any possible effect that this
water table may have on the factors of safety calculated in part (b).
NOTE: Taylor’s charts may be used in this question.

Q5 (An excel file should be submitted to [email protected]) A 6 m deep slope is going to be excavated in a deep soil deposit. The geometry of the slope is shown in the following figure. Assume. The soil has the following properties: Y 20 kN/m' c,-20 kPa, φ' 5° Water table is well below the toe of the embankment. (a) Calculate the slope batter angle, a, for which slope failure would occur. (b) Assume a slope batter angle of α ranging from 40° to 60 with an incremental step of 29. Accordingly, determine the factor of safety for this slope. (c) Plot the factor of safety against the slope batter angle. (d)If the water table raises to a level 2 m above the toe of the slope, discuss any possible effect that this water table may have on the factors of safety calculated in part (b). NOTE: Taylor's charts may be used in this question. 6m ot

Answer 1

"(a) when water table is well below FOS = c/r_t H cos alpha sin alpha + tan phi/tan alpha 1 = 20/20 times 6 times cos alpha sin alpha + tan 5 degree/tan alpha 1 = 1/6 cos alpha sin alpha + 0.0875/tan alpha By hit and trail alpha = 14.89 degree (b) FOS = 1/6 cos alpha sin alpha + 0.875/tan alpha (c) (d) The water table is 2m above the toe of the slop H = 6m h = 2m FOS = C/[r_t(H - h) + r_sat(h)] cos alpha sin alpha + r_t(H - h) + r_sat times h times tan phi/r_t(H - h) + r_sat times h times tan alpha r