Journal
ROCK MECHANICS AND ROCK ENGINEERING
Volume 53, Issue 7, Pages 3111-3131Publisher
SPRINGER WIEN
DOI: 10.1007/s00603-020-02094-3
Keywords
Compression-shear; Tension-shear; Hoek-Brown strength criterion; Shearing rate
Funding
- National Natural Science Foundation of China [41807279, 41672300, 41972297]
- Natural Science Foundation of Hebei Province, China [E2019202336]
- Supporting program of hundred promising innovative talents in Hebei provincial education office [SLRC2019027]
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Direct shear tests on rocks under compression-shear stress conditions have been widely conducted, whereas few have been performed under tension-shear stress conditions. However, rocks exhibit tension-shear failures in many scenarios, such as in the excavation disturbed zone in deep underground caverns and high slopes. A series of direct shear tests were performed with cuboid sandstone specimens under different normal tensile stresses (sigma(n) = - 3, - 2, and - 1 MPa) and compressive stresses (sigma(n) = 1, 3, and 5 MPa) at different shearing rates (v = 0.2, 1, 5, and 10 mm/min). The tension-shear tests were performed using an auxiliary device in combination with a compression-shear testing machine. The results showed that the fracture, shear stress-displacement curve, shear stiffness and shear strength were affected by both sigma(n) and v, and the differences in these mechanical behaviour between compression-shear and tension-shear cases were analysed in detail. The shear strength had a nonlinear relationship with both sigma(n) and v in the full region of tested normal stress (namely, the normal stress range from tension to low compression). The Hoek-Brown criterion (tau=A(sigma n-sigma t)B) considering the shearing rate effect (the relationship between parameter A (B) and shearing rate v is represented by a natural logarithm function) was proposed as the optimal shearing rate-dependent strength criterion for sandstone in the tested normal stress range.
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