Theory and full-scale simulation testing of the mechanical properties of anchors under a variable lateral pressure coefficient

The mechanical behavior of the lateral pressure coefficient (LPC) of the axial stress of the anchor rod is an important factor in roadway bolt support, especially in deep mining, where the variation of the LPC is larger. In this paper, an innovative mechanical model of bolt pulling is proposed in which the influence of the LPC is considered. When the LPC is changed, the variation of the axial force along the anchor rod body is expressed by the interface normal stress of the anchoring system. In addition, a full-scale test model with a 1:1 similarity ratio was developed in the laboratory and the influence of the LPC on the deformation and stress of the anchor rod under vertical and horizontal pressure was studied by using a 2.5-m fiber Bragg grating (FBG) force-measuring anchor rod. The results demonstrate that the axial force of the bolt shows the same increasing trend under various LPC values. The theoretical solution of the bolt axial force variation value accords with the experimental data. The theoretical calculation method can effectively predict the variation distribution of the bolt axial force under various LPC changes. Increasing the LPC of the surrounding rock can effectively reduce the axial force and the deformation of the bolt under the same pulling force. The support effect of the bolt can be improved by increasing the pressure of the anchor hole and increasing the interface friction coefficient between the anchoring agent and the surrounding rock during the construction of the bolt support.