Mechanical behavior and fracture response characteristics of hard sandstone considering bedding dip angle

Aiming at the mechanical behavior and fracture response characteristics of hard sandstone considering bedding dip angle, uniaxial compression tests of hard sandstone with different bedding dip angle were carried out to explore the influence of bedding dip angle on the mechanical behavior of hard sandstone and the relationship between bedding dip angle and fractal characteristics of fragments. The test results show that the bedding dip angle has no significant effect on the type characteristics of the stress-strain curve of hard sandstone, but when the dip angle is small (0°, 22.5°, 45°), the curve shows the law of single peak. When the dip angle is large (67.5°, 90°), the curve shows the law of multi-peak, and the fluctuation position of the curve is mainly near the peak value. Both peak stress σ_d and peak strain ε_d reach the minimum values 46.25 MPa and 9.80×10^-3 when the dip angle is 67.5° (the most unfavorable bedding structural plane). The effect of bedding dip angle on the stress of hard sandstone is obviously greater than that of strain. Affected by bedding dip angle, the degree of anisotropy of hard sandstone is 1.32-1.64, showing the characteristics of low anisotropy. The bedding dip angle has a significant influence on the failure mode of hard sandstone. With the increase of bedding dip angle, the hard sandstone shows the damage failure evolution law of shear failure-shear tension compound failure-bedding structural plane shear failure-splitting failure. Under uniaxial compression, the quality and fractal characteristics of hard sandstone are obvious, the hard sandstone fragments are mainly distributed in middle blocks, and the bedding dip angle has little influence on the mass distribution of fine-grained fragments, and the value of fractal dimension is in 1-2. A large proportion of fragments are distributed in the range of large size distribution. The research results can provide theoretical reference for the stability of rock with bedding structural plane and the disaster prevention and control of underground space engineering.