Effect of Cementation Degree on Shear Characteristic and Failure Mechanism of Bimrocks Containing Gravels of Different Sizes

Abstract

AbstractTo reveal the influence of cementation degree on the mechanical properties of bimrocks with different particle sizes under different types and contents of cement, indoor direct shear tests as well as numerical tests were conducted. The variation law of mechanical properties and the development law of internal force chain distribution of bimrocks under different conditions are fully studied. The specimens with three particle sizes, two cementing types (cement and gypsum), and three cementing contents were prepared for indoor shear tests under different normal stresses. The results show that the fluctuation of shear stress-displacement curve of bimrocks with round gravels of large particle size is relatively gentle, and the fluctuation of residual strength is relatively small. Under low normal stress, the peak shear strength of bimrocks with round gravels of large particle size can be increased by 115.2% under the action of cementation. Compared with the cohesion of samples without cementation, the maximum improvement of the cohesion of the samples containing large particle size, small particle size, and mixed particle size with different cementing materials is 143.2%, 149.0%, and 141.9%, respectively. The results show that, compared with the internal friction angle of samples without cementation, the maximum increases of the internal friction angle of the samples with large particle size, small particle size, and mixed particle size for adding different contents of cementing materials are 15.7%, 18.5%, and 21.2%, respectively. Numerical tests show that, with the increase of cementation degree, the gathering of force chain is more obvious and more concentrated near the shear surface.