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CE5011 exam 2017 2018 – Saved

- (a) A student carried out direct shear tests on four specimens of a certain soil and obtained the following data:

Test No. Total normal stress (IN m-2) Total shear stress at failure (IsN, m-2) 1 20 22 2 40 36 3 60 32 4 80 80

(D

Plot an appropriate graph on the graph paper provided and determine the shear strength parameter values. Figure Q8 is at the end of this paper. Please detach, write your i.d, number and attach to your answer booklet

(5 marks)

(ii) If only the first three test results were available, discuss what you could interpret from those results about the shear strength of this soil, and what the implications would be for a site investigation requiring this information.

(b) Explain the differences between, and engineering implications of:

(U Normally-consolidated and over-consolidated soil

(ii) Drained and uftdTajned shear strength

(5 marks)

(3 marks)

(3 marks)

What is the total normal stress on a failure plane if there is 28 kN m-2 of pore pressure giving an effective normal stress at failure of 59 klt m-2 in a soil with measured shear strength parameters of c’ = 17 issF,’„a, and 4′ = 31°? (2 marks)

(ii) What is the shear strength of this soil according to the Mohr Coulomb failure criterion? (2 marks)

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