Strength criteria for intact rock are essential for the safe design of many engineering
structures. These criteria have been derived mainly from tests in the compressive stress
region. Very few results have been published for confined, direct tensile tests on intact rock.
No appropriate criteria are available for addressing the issue on tensile strength of intact
rock at current stage. We present the results of direct triaxial tensile tests on Longmaxi
Shales under varying confining stresses. These and the results from previous tests in marble …