Select all true statements. 1-Direct shear tests are useful to establish the Mohr-Coulomb envelope for intact rock. 2-In the stress-strain curve, yield occurs when the deformation becomes plastic.  3-When discontinuities are present in a rock mass, failure can occur along intact rock or along discontinuities. 4- In the stress-strain curve, strain-softening is observed between the yield point and the peak strength.  5-A lower Geological Strength Index (GSI) implies smaller Mb and s rock constants and a poor-quality rock mass.

In a zone with a constant stress gradient of a mechanical- structural element, the stresses acting in the "x" direction are Ox = 5900 psi and Txy = 1950 psi. Determine the allowable values if the maximum shear stress is limited to Tmax = 2500 psi. for Ty

Samples from sandstone were collected from two different depths (80m and 200m) and triaxial shearing tests were performed to estimate the shear strength parameters. From each depth, two different specimens were tests at distinct isotropic confining pressures and from the experiments the deviatoric stress at failure was assessed. The results from these experiments are summarized in Table 1.1. Table 1.1 – Results of triaxial shearing tests at failure for the sandstone samples collected from different depths (Question 1) Specimen No. q (MPa) at failure Collection оз (MPa) depth (m) 1 80 0.600 3.325 2 80 1.800 8.179 3 200 0.600 5.310 4 200 1.800 11.103 (a) Determine the angle of shear strength and cohesion of the sandstone for each of the two different depths using the Mohr-Coulomb (linear) failure criterion based on total stress principle. (b) During the triaxial test measurements, local strain gauges were attached to the specimens for high quality measurements to be performed. It was…

For the rock element, shown: Calculate the following stresses of interest Maximum Principal Stress Minimum Principal Stress Maximum Shear Stress Normal Stress at Failure Plane A-B Shear Stress at Failure Plane A-B SHOW COMPLETE SOLUTION