Question 1: (30 Marks)
A series of three direct shear test were performed on samples of dry sand. The internal dimensions of the direct shear box are 100 mm x 100 mm on plan, by 60mm depth. The results of the direct shear test are given in the table below:
Table 1
| Test No. | Normal Force (N) | Shear Force (N) |
| 1 | 200 | 167.8 |
| 2 | 600 | 503.5 |
| 3 | 1000 | 839.1 |
a)Determine the effective shear strength parameters c′ and φ′, of the sand. (12.5 marks)
b)A sample of the same sand has 50 mm diameter and 100 mm high is testedusing consolidated drained (CD) triaxial compression test at cell pressure of30 kPa. Determine the axial deviator failure load knowing that the sample willdeform 12 mm vertically and 2 mm laterally. (12.5 marks)
c)What angle relative to horizontal will the soil sample in (b) will fail at? (5 marks)
Question 2: (35 Marks)
Figure 1 below shows the cross-section of a proposed cutting in a cohesive soil. The undrained shear strength of soil, cu, may be taken as 25 kN/m2 for the upper layer and 42 kN/m2 for the lower layer, and the unit weight is 19 kN/m3 for both layers. Use the mass procedure method to calculate the factor of safety against sliding along the slip circle shown in the figure for the following cases:
a)Ignoring the possibility of tension cracks. (15 marks)
b)Allowing for a tension crack full of water. (20 marks)
Question 3: (35 Marks)
Draw the distribution of the lateral pressures (active and passive earth pressures, and hydrostatic pressure) acting on the smooth sheet pile wall shown in Figure 2. Calculate the total thrust on the wall and determine its point of application from the Point (O) shown in the figure. Tabulate your answers and give details of all necessary calculations.
