Study on the influence mechanism of interfacial inclination angle on the mechanical behavior of coal and concrete specimens

In recent years, the proposed distributed underground reservoir technology has attracted a lot of attention from experts and scholars in the field of engineering. This technology not only avoids the waste of mine water resources, but also realizes the rational utilization of coal mine underground space, and promotes the green and sustainable development of coal mining. As a storage facility of the underground reservoir, the stability of the coal-concrete composite structure will directly affect the long-term safe operation of the underground reservoir. In light of this situation, this study conducted uniaxial compression and acoustic emission experiments on coalconcrete specimens with interface inclinations of 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees to investigate the impact of interface inclination on coal-concrete specimen stability. The test results show that the stress-strain curve passes through three stages: compression, elastic deformation, and deformation failure. The peak stress, peak strain, and elastic modulus exhibit a "U"-shaped distribution with varying angles, reaching a minimum at 60 degrees. Crack analysis using RA-AF reveals that tension cracks predominate at 0 degrees-30 degrees, while shear cracks predominate at 45 degrees 90 degrees. The application of the Mohr-Coulomb criterion to coal-concrete specimens is discussed, and a derivation of the formula for calculating the ultimate principal stress is provided. The research in this paper provides a theoretical reference for the structural design and parameter selection of underground reservoir dams in coal mines.