Geomaechanics Assignment

Question 1. [7 marks]

Based on the site investigation and laboratory testing, the following table provides the information

of the slope.

Unit weight su (or cu ) c ' ? ' Slope angle Slope height

( kN m3 ) ( kN m2 ) ( kN m3 ) (°) (°) (m)

? 16 d ?

? 18 sat ?

40 5 20 45 10

d H ?1

? Estimate the short?term factor of safety (F) for the slope.

? If the slope is well drained, and therefore it is totally dry. Estimate the long?term factor of

safety.

? Can you make any conclusion by comparing the above obtained factors of safety.

Using Taylor's Charts, and assuming that the soil is infinitely deep, the short term factor of safety (F) would be:

N = C = 0.06 (taken from chart)

? H F

Hence

F = 40 = 3.73 which indicates it is stable.

18*10*0.06

Determining the long term factor of safety:

F = tan ?' = tan 20 = 0.364

tan ? tan 45

These results show that in the short term, while the soil is still saturated, the slope will be stable but in the long term, when the slope becomes