Journal
ROCK MECHANICS AND ROCK ENGINEERING
Volume 50, Issue 6, Pages 1425-1438Publisher
SPRINGER WIEN
DOI: 10.1007/s00603-017-1179-1
Keywords
Rock mechanics; Tension; Shear; Failure criterion; Tension-shear device
Funding
- National Natural Science Foundation of China [41472245, 41672300]
- Fundamental Research Funds for the Central Universities [106112016CDJZR208804]
- Scientific Research Foundation of State Key Lab. of Coal Mine Disaster Dynamics and Control [2011DA105287-MS201502]
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Tension-shear failure is a typical failure mode in the rock masses in unloading zones induced by excavation or river incision, etc., such as in excavation-disturbed zone of deep underground caverns and superficial rocks of high steep slopes. However, almost all the current shear failure criteria for rock are usually derived on the basis of compression-shear failure. This paper proposes a simple device for use with a servo-controlled compression-shear testing machine to conduct the tension-shear tests of cuboid rock specimens, to test the direct shear behavior of sandstone under different constant normal tensile stress conditions (sigma = -1, -1.5, -2, -2.5 and -3 MPa) as well as the uniaxial tension behavior. Generally, the fracture surface roughness decreases and the proportion of comminution areas in fracture surface increases as the change of stress state from tension to tension-shear and to compression-shear. Stepped fracture is a primary fracture pattern in the tension-shear tests. The shear stiffness, shear deformation and normal deformation (except the normal deformation for sigma = -1 MPa) decrease during shearing, while the total normal deformation containing the pre-shearing portion increases as the normal tensile stress level (|sigma|) goes up. Shear strength is more sensitive to the normal tensile stress than to the normal compressive stress, and the power function failure criterion (or Mohr envelope form of Hoek-Brown criterion) is examined to be the optimal criterion for the tested sandstone in the full region of tested normal stress in this study.
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