Numerical study on the influence of cross-sectional shape on strength and deformation behaviors of rocks under uniaxial compression

Cross-sectional shape effect, which has not been well studied, is one of the geometry effects that influence rock laboratory test results. In order to investigate the influence of cross-sectional shape on the strength and deformation behaviors of rocks, a comprehensive numerical experiment is carried out to simulate the deformation responses of circular, square, and rectangular cross-sectionally shaped specimens in uniaxial compression. The validity of the numerical model is first examined by comparing the uniaxial compressive strengths (UCS) of cylinder and square prism specimens obtained from the numerical modeling with these obtained in laboratory tests. Both the numerical modeling and laboratory test results show that the cross-sectional shape has a very small influence on the UCS of rocks. However, the numerical results show that the cross-sectional shape affects the post-peak behaviors of rocks considerably. It is also concluded that hoop tension contributes little to affecting rock strength. It is revealed through the numerical study that in the laboratory tests because the square prism specimens with a slenderness (defined by specimen height divided by specimen width) the same as that of a cylinder specimen have an equivalent diameter larger than that of the cylinder specimens, a slightly higher strength of the square prism specimens is thus observed. It is suggested to use the equivalent diameter of a non-circular cross-section to define the slenderness of a specimen to present laboratory test and numerical simulation results consistently.