In: Civil Engineering
A direct shear test is conducted on a large specimen of dry sand (square cross section with following dimensions: 7.5 cm x 7.5 cm x 3.0 cm [height], Mass = 271.0 g) with a normal stress of 500 kPa. Failure occurred when the horizontal force was 1.96 kN. For the same sand, tests were also conducted to determine the specific gravity and the maximum and minimum void ratios. These tests yielded the following results: Gs= 2.65, emax=0.80, emin = 0.45. a) Calculate the relative density of the sand specimen b) Determine the friction angle of the soil. c) A triaxial specimen (H= 8.0 cm, D = 3.8 cm, Dr~45%) is prepared using the same sand. The test is performed on a saturated specimen with a chamber pressure of 500 kPa and an initial value of the pore pressure u of 100 kPa. Assuming that the results of the direct shear test can be used to predict those of the triaxial test, at what value of the total axial stress does the triaxial specimen fail?