In order to study the effect of impact load on straight-wall arch cavern and surrounding rock, large-scale steel fiber reinforced concrete specimens were prepared, and a self-developed pendulum impacting system with biaxial stresses was used to carry out impact tests. A super-dynamic information acquisition system was used to record the impact force and internal strain, and digital image correlation technology was used to characterize the surface strain field. 0.6 MPa stress was applied vertically, and the height of 2000 kg pendulum was raised to 150 mm. The results show that: The shock wave with amplitude attenuation was a typical low-frequency shock wave. Four cracks appeared in the spandrel and foot of the straight wall arch specimen, and the cracks at the spandrel were connected by a circumferential crack on the vault of the cavern. The internal peak strain and plastic strain are mainly tensile strain, compressive strain distributed near the left foot of the tunnel. The peak strain was larger in the circumferential direction, smaller in the radial and axial direction. And the plastic strain in the left spandrel was the largest. And the vault was prone to plastic deformation which can not be recovered through peak or plastic strain, but the ratios of plastic strain to peak strain in the vault were all larger. DIC strain cloud map showed that within less than 200 μs, the four cracks of spinner and foot of the sample were formed and connected, and the vertical strain changed the most, the vertical strain concentration area was consistent with the fracture morphology, the horizontal strain concentration area mainly appeared at the spinner position, and the shear strain concentration area was mainly distributed at the bend of each crack.

To study the characteristics of sandstone crack propagation under hydraulic coupling, sandstone laboratory tests were conducted under different seepage pressures and confining pressures. Under the same effective confining pressure, it is shown that the rock brittleness index becomes higher as the seepage pressure increases, while the crack initiation stress, the crack damage stress, and the peak stress decrease gradually. The initial volumetric strain of the crack decreases, and the volumetric strain of crack propagation decreases firstly and then increases afterward. The growth rate of the crack axial strain and the crack circumferential strain are both increasing that corresponding to the damage stress and the peak stress, however, no obvious relation is observed between the growth rate of the crack volume strain and the seepage pressure. Under the same seepage pressure, the initiation stress, damage stress, and peak stress gradually increase as the effective confining pressure increases. In addition, the growth rates of the crack axial strain, circumferential strain and volumetric strain increase gradually during deformation that corresponds to the crack initiation stress, damage stress and peak stress, respectively. When comparing the different growth rates of crack strain for a tested sandstone specimen, it is found that the strain growth rates have the following order: the crack axial strain > the crack circumferential strain > the crack volume strain.