Mechanical properties and energy response of like rock-sprayed high ductility concrete combined body under smooth and wavy interfaces

Abstract

• A new method for preparing like rock-SHDC combined body with interface roughness (JRC) of 28. • The static and dynamic mechanical properties and energy response characteristics of like rock-SHDC combined body under different roughness interfaces are studied to improve the research of SHDC in the engineering field and provide a basis for supporting structure design. • In the impact compression test, when the incident wave energy passes through the interface, reflection and transmission will occur. Therefore, the combined body of double-layer media has more reflected energy than SHDC monomer. • When SHDC is applied in engineering, the surrounding rock roughness should not be too large. Under the condition of high ground stress and large deformation surrounding rock (argillaceous siltstone), the green and low-cost sprayed high ductility concrete (SHDC) used in the initial support structure of tunnels and coal mines can effectively solve the problem of insufficient ductility, toughness and crack resistance of ordinary sprayed concrete. The layered double medium composed of SHDC and surrounding rock near the interface as the research object, replacing surrounding rock with similar materials for rapid machining of high roughness interface. Aiming at the four common problems during construction, static compression, notched three-point bending and impact compression tests were carried out. The static and dynamic mechanical properties and energy response of the like rock-SHDC combined body under smooth and wavy interfaces (different roughness) were deeply explored, the crack propagation law of the combined body were analyzed by using DIC technology and failure modes. The results show that like-rock is feasible as the similar material of surrounding rock. Under static test, with the increase of interface roughness, most of the performance parameters will be significantly reduced, and only a few performance parameters increased. In the compression process, the cracks of the combined body under the waviness interface are dispersed and converged. However, only crack convergence occurs under the smooth interface. In the three-point bending process, the crack development direction of different specimens is consistent, but the crack growth position of the combined body under the waviness interface is shifted. Under impact test, with the increase of interface roughness, the peak stress, elastic modulus and absorbed energy decreased significantly, while the peak strain and reflected energy increased. In addition, deflection cracks appeared in the combined body, and cracks dispersed under the smooth interface, while cracks converged under the waviness interface. The combined body’s static and dynamic breakage degree under the waviness interface is more serious than that under the smooth interface. Therefore, the combined body has relatively better working performance (compression and bending) under the smooth interface, when SHDC is applied in engineering, the surrounding rock roughness should not be too large.