Reference no: EM132961536

UBGMTA-15-M Advanced Soil Mechanics - University of the West of England

Question 1

(a) The safety of any geotechnical structure is dependent on the strength of the soil, explain.

(b) Define the critical state parameters

(c) Briefly explain three (3) soil models used to interpret the strength of soils

(d) Write briefly on Eurocode 7 geotechnical design method and state three ways in which this method differs from the tried and tested British Standards design method (BS 8004 Code).

Question 2 (a) Prove that

Knc = 6 - 2M_c/6+M_c

Where K_nc=0 Coefficient of earth pressure at rest for normally consolidated soil

(b) Show that the effective stress path in one-dimensional consolidation is

q/p' = 3M_c/6-M_c

(c) Soil investigation at a site gave the following information. Fine sand exists to a depth of 10.6m and below this lies a soft clay layer 7.6m thick. The water table is at 4.6m below the ground surface. The effective unit weight of sand is 10.4 kN/m³, and the bulk unit weight above the water table is 17.6 kN/m³. The water content of the normally consolidated clay is 40%, its liquid limit is 45%, and the specific gravity of the solid particles is 2.78. The proposed construction will transmit a net stress of 120 kN/m² at the centre of the clay. Calculate the average settlement of the clay layer.

Question 3
Figure Q1 shows a soil element at a depth of 5 m in a very soft, Ko - consolidated clay, with groundwater level at ground surface. Calculate the;

(a) Initial stresses

(b) Mean effective stress at initial yield

(c) Estimate stresses at initial yield

Figure Q1. A soil element at 5m depth

Question 4

A square footing at a depth of 1.5m founded on medium strength clay is required to carry an imposed permanent action, VGK of 250KN and imposed variable action, VQK of 110KN excluding self weight of footing. The dimension of the footing is 2.y (m) X 2.y (m), where y is the last digit of your student identity number. The clay has the following characteristic: Undrained shear strength, Cuk = 45kPa Effective cohesion, C'k = 5kPa
Characteristics angle of shear resistance, φ'k = 25o

Weight density of clay, γ = 21kN/m3 and weight density of concrete, γcon = 25kN/m3, take foundation slab thickness = 0.6m.
If water table is currently at 1m below ground surface, verify the ultimate limit state under drained conditions using design approach 1 combination 2 of the Eurocode 7, and design depth of water table dw,d = 0m.

Question 5

Verify the serviceability limit state for the footing in Question 4 using ultimate limit state and immediate settlement calculations. Take the undrained Young's modulus of the clay, Eu = 500cuk, and settlement factors µ₀ = 0.93 and µ₁ = 0.4.