Q.4/ A normally consolidated (N.C) clay was found to have p-15°, q'= 30°. The soil specimen was tested in a consolidated undrained triaxial test (CU) under a cell pressure 150 kN/m². Determine four of the followings: a) Deviator stress at failure b) Major principal stresses at failure c) Minor principal stresses at failure

2. A soil specimen is subjected to a tri-axial test. The soilspecimen is cohesionless. If the shear stress that causesfailure is 280 kPa and the normal stress at failure is only480 kPa.a) Determine the angle of shearing resistance,b) Determine the angle that the failure planemeasured from the major principal plane.c) Determine the total axial stress at which failure isexpected to occur.

A sample of dry sand is tested in direct shear. Theshear box holding the sample has a circular crosssection with a diameter of 50 mm. The normal(compressive) load imposed is 200 N. The sam-ple shears when the shear force is 130 N.(a) Determine the test normal stress and shearstress at failure.(b) Determine the angle of internal frictionfor this soil.(c) What is the probable condition of the testedsample (dense, loose, etc.)?

The table below contains data obtained from 2 CU triaxial tests on similar clay specimens. Specimen no. Cell pressure during consolidation (kPa) Deviatoric stress at failure (kPa) 269 Pore water pressure at failure (kPa) 264 400 379 1 2 462 689 Calculate the cohesion, c (kPa) of the clay soil in terms of total stress. Enter answer to 1 d.p. and don't enter units.

a）For clays, the failure line (one that connects the peak failure stresses) in the normally consolidated range does not have a cohesion intercept, whereas the failure line in the overconsolidated range has a cohesion intercept. T or F B）During the shearing phase of a CU test, the void ratio of a NC consolidated clay specimen will: 1 decrease. 2 could increase or decrease. 3 remain a constant. 4 increase. C)What does the cohesion (that appears in the Mohr-Coulomb criterion) of OC clays depend on? 1the preconsolidation pressure. 2whether the failure stresses are total or effective. 3the soil type. 4everything listed here.

2. A series of consolidated, undrained triaxial tests were carried out on specimens of a saturated clay under no backpressure. The test data at failure are summarized: Confining Pressure (kPa) Deviator Stress (kPa) Pore Water Pressure (kPa) 150 192 80 300 341 154 450 504 222 a. Draw the Mohr circles and find the cohesion and friction angles in terms of effective stresses. b. Compute Skempton’s A-parameter at failure for all three specimens. c. Is the soil normally consolidated or overconsolidated? Why? d. Another specimen of the same clay that was consolidated under a cell pressure of 250 kPa was subjected to a consolidated, drained triaxial test. What would be the deviator stress at failure?

During the shearing phase of a CU test, the void ratio of a NC consolidated clay specimen will: 1decrease. 2could increase or decrease. 3remain a constant. 4increase.

5- The shear strength of a normally consolidated clay can be given by the equation tf o'tan 27°. Following are the results of a consolidated-undrained test on the clay. • Chamber-confining pressure = 3,130 lb/ft² Deviator stress at failure = 2,510 lb/ft² a) Determine the consolidated-undrained friction angle b) Pore-water pressure developed in the specimen at failure

Foundation: Direct Shear Test

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