Reference no: EM133293285
Question 1: The soil profile at a site for a proposed office building consists of a layer of fine sand 10.4 m thick above a layer of soft, normally consolidated clay 2 m thick. Below the soft clay is a deposit of coarse sand. The groundwater table was observed at 3 m below ground level. The void ratio of the sand is 0.76 and the water content of the clay is 43%. The building will impose a vertical stress increase of 140 kPa at the middle of the clay layer. Estimate the primary consolidation settlement of the clay. Assume the soil above the water table to be saturated, Cc = 0.3, and Gs = 2.7.
Question 2: A sample, 75 mm in diameter and 20 mm high, taken from a clay layer 10 m thick, was tested in an oedometer with drainage at the upper and lower boundaries. It took the laboratory sample 15 minutes to reach 50% consolidation.
(a) If the clay layer in the field has the same drainage condition as the laboratory sample, calculate how long it will take the 10-m clay layer to achieve 50% and 90% consolidation.
(b) How much more time would it take the 10-m clay layer to achieve 50% consolidation if drainage existed on only one boundary?
Question 3: An unconfined compression test was carried out on a saturated clay sample. The maximum (peak) load the clay sustained was 127 N and the vertical displacement was 0.8 mm. The size of the sample was 38 mm diameter x 76 mm long. Determine the undrained shear strength.
Question 4: The following results were obtained from direct shear tests on specimens of a sand compacted to the in-situ density. Determine the value of the shear strength parameter cif.
| Normal stress (kN/m7) |
50 |
100 |
200 |
300 |
| Shear stress at failure (kN/m2) |
36 |
80 |
154 |
235 |
Would failure occur on a plane within a mass of this sand at a point where the shear stress is 122kN/m2 and the effective normal stress 246 kN/m2?
Question 5. The results shown in Table below were obtained at failure in a series of triaxial tests on specimens of a saturated clay initially 38mm in diameter by 76mm long. Determine the values of the shear strength parameters with respect to (a) total stress and (b) effective stress.