Mechanics Damage Characteristics of Resin Anchored Bolts with Different Materials Under High Temperature

Resin bolt have many advantages, such as high anchoring force, good stability and strong adaptability. They are one of the common support methods for roadway and tunnel engineering. As underground engineering progresses, the working environment becomes more complex and the high temperature hazards become more severe. The properties of rocks, resin materials and resin anchoring effects change significantly under high temperature, affecting the stability of underground engineering. Using orthogonal test design, we conducted 19 sets of resin bolt pull-out tests and resin material thermal damage tests with different temperatures, bolt materials and anchoring depths. We analyzed the mechanical damage characteristics of resin anchor bodies under high temperature. The test results show that: (1) The pull-out curve of the anchor exhibits a step-like change under high temperature. The anchor body failure shows four failure modes: anchor-slurry failure, slurry-rock interface failure, bolt breakage and rock failure. (2) Anchoring depth has the largest impact on the anchoring performance of resin anchors, followed by bolt materials and temperature. The anchoring force increases approximately linearly with the anchoring depth, and decreases rapidly with the temperature, especially after 100 °C. (3) Under high temperature, carbon fiber anchor (CFRP) bolts have the best anchoring effect, followed by basalt fiber anchor (BFRP) and glass fiber anchor (GFRP) bolts. Threaded steel anchor bolts have the worst anchoring effect. (4) The anchoring effect of bolts in the range of 50–100 °C is dominated by the high temperature response characteristics of resin materials. In the range of 150–200 °C, it is dominated by the response characteristics of resin materials and rocks. (5) Under high temperature, the resin materials degrade and fracture, causing the bolts to deform and fail in a step-like manner.