3DEC Simulations of Dynamic Direct Shear Tests Considering Joint Roughness Coefficient (JRC)

In general, the dynamic properties, e.g., dynamic rock modulus and dynamic rock (shear or tensile) strength are two to three times greater than static moduli and strengths. Thus, understanding the dynamic rock characteristics is necessary to improve the design of support systems in underground mines, nearly all of which are subject to dynamic loading. In this paper, we report the baseline results of an ongoing study. Experimental direct shear tests were conducted on jointed specimens that were created by 3D printer to represent 3D joint roughness coefficients (JRCs) of 12 and 17. These JRC values are relatively close, but they represent the roughness of a large proportion of joints found in underground mines. We also report the results of numerical direct shear tests using 3DEC modeling code that were conducted for the purpose of learning more about dynamic shear failure mechanisms. We performed static direct shear tests for the purpose of calibrating our models with the empirical solution. Results of these tests compared well with the empirical results. Subsequent dynamic numerical direct shear tests were performed using 3DEC, simulating the dynamic direct shear tests performed in the laboratory. The numerical direct shear stresses compared well with those of the laboratory tests. Furthermore, the results confirm that the ratio of dynamic to static shear strengths vary between approximately 2 and 3 in the range of normal stresses used in the tests.