Study on the Effect of Bond Strength on the Failure Mode of Coarse-Grained Sandstone in Weakly Cemented Stratum

Bond strength is one of the most important parameters and can affect the macroscopic mechanical properties and the damage state of rock to some degree. Coarse-grained sandstone was studied using the controlled variable method. The influence of parallel bond strength on the peak strength and failure mode of coarse-grained sandstone was simulated, and the evolution law of peak strength and the failure mode of bond strength were comprehensively analyzed. The results show that the peak strength of the rock was positively correlated with the bond strength; the difference in quantity between the tensile and shear cracks was negatively correlated with tensile bond strength and positively correlated with shear bond strength. With a tensile-shear bond strength ratio of less than 0.5, the peak strength of the rock was usually stable at the certain extreme value under a constant tensile bond strength. The tensile cracks were negatively correlated with the tensile-shear bond strength ratio, and the shear cracks were positively correlated with the tensile-shear bond strength ratio. The main failure mode of the coarse-grained sandstone in the weakly cemented stratum of the Hongqinghe coal mine is shear failure. The research results can be used to guide the ground control of other mine stopes or roadways with weak cementation lithology.