Mechanical response and energy partition evolution of coal-rock combinations with different strength ratios

The mechanical response and energy partition of coal-rock combinations with different strength ratios were studied through laboratorial uniaxial compression tests and numerical simulation calculations. The results show that the strength and deformation parameters of the coal-rock combination mainly depend on the weak carrier. When the rock strength is weaker than the coal strength, the combination strength is similar to the rock strength, and the main destruction occurred at the rock section, when the coal strength and rock strength are similar, the combination strength is slightly higher than that of coal and rock, and fully destroying the coal and rock, as the strength and rigidity of the rock increase, the strength and rigidity of the combination also increase, and after the rock strength reaches twice of the coal strength, the uniaxial compressive strength of combination increased to 15%, the elastic modulus increased to 70% and both tended to be gentle compared with coal. At this time, coal is the main body of destruction, and with a much more consistent form of destruction. The loading stage of coal-rock combination can be divided into three stages: rapid accumulation of strain energy, slow growth of strain energy and rapid release of strain energy. Dissipative energy and friction energy begin to increase slowly in the second stage, after entering the third stage, dissipative energy, frictional energy and kinetic energy begin to increase sharply. The strain energy evolution of coal and rock is similar to that of the combination, coal is the important carrier of strain energy in combination. As the rock strength increases, the strain energy density of the coal-rock combination increases rapidly and then decreases slowly. When the strength ratio of the coal and rock is 1:2, the coal-rock combination reaches the highest strain energy density. The bursting energy index of coal continues to increase, and the strain energy density of coal in the combination increases rapidly and then plateaus. When the rock strength in the combination is higher than that of coal, the energy storage capacity of coal strain energy can be increased up to 30%. The strain energy density of the rock in the combination increases first and then decreases, and then reaches its maximum when the coal-rock strength ratio is 1:1. © 2020, Science Press. All right reserved.