Study on Loading Rate and Rock–Coal Strength Ratio Effect on Mechanical Properties of Coal–Rock Combination

Abstract

In order to clarify the relationship between the mechanical properties of coal-rock composite and the loading rate and rock–coal strength ratio, uniaxial compression tests were carried out on coal-rock combinations with three different rock–coal strength ratios at four different loading rates. The rock–coal strength ratio \(\lambda\) is a ratio of the compression strength of rock to the compression strength of coal. The test results indicate that the relationship between the mechanical properties of coal-rock composite and loading rate is influenced by both the strong and weak components in the composite. The peak stress and elastic modulus mainly depend on the weak component, while the peak strain is determined by both the strong and weak components. For peak stress and elastic modulus, when the weak body is the same, the relationship with loading rate is the same, otherwise it is different. The relationship between the mechanical properties of coal-rock combination and \(\lambda\) is not affected by the loading rate. The weak body in the coal-rock combination is the main body of damage, and the greater the value of \(\lambda\), the more severe the damage. At the same time, the failure mode shows a gradual transition from weak body failure inducing strong body failure to only weak body failure.