Experimental study and mechanism analysis of bolt anchorage interface failure under temperature and pressure coupling

In order to improve the stability of resin anchored support structure of roadway surrounding rock under deep high temperature and high pressure environment, the failure mechanism of the interface between bolt and resin anchoring agent under the coupling action of temperature and pressure is studied. Firstly, by simulating the indoor pull-out test of anchors with different surrounding rock strength under different temperature environment, it is concluded that the deformation and failure of anchors can be divided into four stages. The ultimate anchoring force increases with the increase of surrounding rock strength, and the ultimate drawing load and residual drawing force decrease with the increase of temperature environment. The failure law of anchorage interface under the coupling action of temperature and pressure is further studied by FLAC3D software. It is concluded that the maximum displacement of the free end of the anchor decreases with the increase of surrounding rock stress, the development range of the plastic zone of the anchor interface decreases with the increase of surrounding rock stress, and the ultimate load of the anchor decreases with the increase of ambient temperature. With the increase of ambient temperature, the axial load transmission range of bolt increases, and the axial force distribution of rod body is more uniform; With the increase of surrounding rock stress environment, the stress of bolt body increases as a whole, and the shear failure resistance of interface increases. Combined with the failure phenomenon of indoor pull-out specimens and the development law of plastic zone, the mechanical models of shear slip failure and shear expansion slip failure modes of the first anchorage interface are established respectively according to the elastic-plastic theory. The relationships between the ultimate failure strength of the interface and temperature, the stress of surrounding rock and the mechanical properties of anchorage materials are obtained, and the rationality of the formula is verified. The research provides technical reference for the safe and efficient construction of deep roadway anchorage engineering and the design of support parameters.