Effect of anchorage angle on dynamic compression-shear response of jointed rock mass

This study aims explore the effect of different anchorage angles on the dynamic mechanical properties of jointed rock mass and the failure behavior of anchorage body. We conducted the dynamic load impact test on fully anchored jointed rock mass with anchorage angles of 15°, 30°, 45°, 60° and 75° by using the split Hopkinson pressure bar system to analyze the dynamic stress and strain of anchored rock mass, the strain of anchored bolt and the sliding compression-shear behavior of anchored matrix under different anchorage angles. Results show that with the increase of anchoring angle, the peak stress of anchorage body demonstrate initial increase and subsequent decrease, namely 15.8, 18.1, 20.9, 24.7 and 23.3 MPa, respectively. The dynamic stress-strain curve of anchorage body under compression and shear resistance of anchor rod exhibits a "double peak" shape. Under the compression-shear behavior of rock mass, the axial strain of bolt shows a decreasing trend, and the strain rate of bolt decreases with the increase of angle at the moment of impact. The strain amplitude monitored by strain gauges on the left and right sides of joint surface is close to each other at 45° anchoring angle. The displacement of the loading end of the anchorage body decreases gradually along the impact direction, namely 4.84, 1.71, 1.40, 1.01 and 0.84 mm, respectively. The ability of the bolt is gradually enhanced to resist the compression-shear slip of the anchorage body along the joint surface.