(Solved): 6. A saturated sand sample is subjected to a triaxial test. Initially the specimen is consolidated ...

6. A saturated sand sample is subjected to a triaxial test. Initially the specimen is consolidated under an isotropic pressure of 25 kPa with free drainage from the specimen. Next, the drain valve is closed and isotropic loading continues until the pressure of the water chamber reaches 75 kPa. Finally, shearing is induced by loading the specimen according to the total stress path sketched below (not to scale). At failure, the chamber pressure was 40 kPa, and the pore water pressure was 29 kPa. a. What was the pore water pressure after the initial consolidation to 25 kPa? [0 kPa, bc specimen was drained] b. What pore water pressure can be expected to have developed when consolidation reached 75 kPa? [50 kPa] c. What was the effective major principal stress (o:) at failure? [46 kPa] d. Sketch the Mohr circle of effective stresses at failure. e. What can be assumed about the effective cohesion of this soil? Why? [c'=0, because it is a sand] f. Analytically determine the effective friction angle of the soil under the assumption made in e. [4'=38"] Total Stress Path: q (kPa) 4 1 p (kPa) 75