Experimental Study of the Triaxial Strength Properties of Hollow Cylindrical Granite Specimens Under Coupled External and Internal Confining Stresses
High geostresses and stress gradients are the predominant stress conditions in deep excavation-disturbed rock masses. The aim of this study is to determine the triaxial compressive strength properties of hollow cylindrical granite specimens under a radially non-uniform confining stress field with different radial stress gradients determined by coupled external and internal confining stresses. Triaxial compression testing of hollow cylindrical rock specimens was performed to investigate the influence of the radial stress gradient, external confining stress and specimen length-to-diameter (L/D) ratio on the triaxial compressive strength. The experimental results and regressed failure criteria indicate that the triaxial compressive strengths of the hollow cylindrical granite specimens increase with the external confining stresses, but decrease with an increase in the radial stress gradients. The calculated goodness of fit (R2) and root-mean-squared error suggest that the nonlinear failure criterion based on the Hoek–Brown model is more accurate than the linear failure criterion based on the Mohr–Coulomb model for determining the influences of the external confining stress and radial stress gradient on the triaxial compressive strength. In addition, the triaxial compressive strength increases with a decreasing L/D ratio due to the strengthening end effect of the hollow cylindrical granite specimens and the change in the failure pattern of these specimens from shear to slabbing.
KeywordsHollow cylindrical granite Radial stress gradient Length-to-diameter ratio Triaxial compressive strength Failure criterion
The work described in this paper was supported by the State Key Research Development Program of China (2016YFC0600706), the National Natural Science Foundation of China (51504287, 51774326 and 41630642) and the Hunan Provincial Natural Science Foundation of China (2017JJ3390) as well as by a the China Postdoctoral Science Foundation funded project (2016M602432), for which the authors are very thankful. The corresponding author acknowledges the support of an open fund from the State Key Laboratory for Geomechanics and Deep Underground Engineering at the University of Mining and Technology-Beijing (SKLGDUEK1418).
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