Effect of prefabricated fractured rock dip angles on mechanical properties and failure modes under dynamic and static loads

With the gradual depletion of shallow geological resources, their development has increased. However, it is difficult to control the stability and bearing capacity of deep-stratum fissure rock bodies under static and dynamic load coupling. To study the relationship between the mechanical properties of anchor-reinforced fissured rock bodies under static and dynamic loading conditions, this study performed a static compression test and dynamic impact test on anchor-reinforced prefabricated fissured red sandstone with different inclination angles. Research has revealed that under static loading conditions, the mechanical properties of anchor-reinforced specimens are stable, and the peak strength fluctuates between 23–27 MPa. Under dynamic loading conditions, the peak strength and deformation decreased with increasing inclination angle. The peak strength decreased from 47.3 MPa at 15° inclination angle to 35.4 MPa at a 90° inclination angle, and the peak strain and dynamic cut line modulus were 1.28 times and 1.23 times of the static loading, respectively. Under static loading, the specimen cracks mainly developed along the prefabricated cracks to shear damage, and the increase in the inclination angle led to the damage spreading to the specimen ends, forming combined tensile–shear damage. Under dynamic loading, the damage was primarily tensile–shear combination damage parallel to the impact direction. Based on the linear uniaxial strength criterion, a new relationship between dynamic peak strength, strain rate, and static peak strength was established, and the correlation coefficients were 0.90–0.98, indicating a good correlation.