QI a) The results of consolidated undrained (CU) tests on three similar specimens of a fully saturated clay soil at failure are given below:- Parameter (kN/m²) Specimen 1 Specimen 2 Specimen 3 Cell Pressure 350 400 500 Deviator Stress at Failure 143 208 312 Pore Pressure at Failure 326 354 418 i) Determine the effective stresses o' and ' for each specimen. (3 marks) ii) Plot the related Mohr circles and determine the effective stress shear strength parameters c' and '. iii) Briefly explain the principle of triaxial test. (4 marks) (4 marks) b) A reinforced concrete retaining wall is constructed to support the temporary haul road as shown in Figure Q.1. At the wall crest, a surcharge load of 20 kN/m² is applied on the horizontal soil surface. The ground water table (GWL) is found at the interface of two soils. Rankine's theory on lateral earth pressure is assumed. i) Determine the total horizontal thrust in kN per unit width of the wall due to the active lateral pressure, surcharge and the hydrostatic pressure. (11 marks) ii) Determine the location of the line of thrust from the bottom of the wall. R.C. Retaining Wall Temp. Haul Road Surcharge 20 kN/m² Compacted Fill c'=0 kN/m² 4'-33° Yb-20 kN/m³ Clay c' =0 kN/m² '-35° Ysat 19 kN/m³ 7w 9.81 kN/m³ Figure Q.1 5m GWL (3 marks)