Analysis of solid load transfer mechanism and characteristics of anchor based on hole wall shape

In found in testing the anchor rod(rope) drawing is an important phenomenon of mechanics，namely when the drawing force to a certain value，the anchor rod(rope) body did not pull out from the hole，rock specimen with noise or vibration，instantly overall cracking along the radial of hole wall，due to the radial pressure is sufficient to cause the whole rock specimen cracking quickly，it cannot ignore the influence of the bearing capacity of anchor bolt is visible. In view of this phenomenon，through the in-depth study of the shear characteristics of rock-rock structural plane and the dilatancy effect that inevitably occurs in the process of structural plane stress shear in the theoretical research results of reaming，it is concluded that the shape of borehole wall is the most important factor to produce this radial stress. Therefore，based on the proper assumptions and consider the bolt hole under the premise of the rough shape of hole wall，based on the nonlinear Mohr - Coulomb strength criterion，combined with load transfer function method and the anchor solid - structural plane dilatancy effect and failure mechanism of surrounding rock，established the stress transfer model adapted to the circular roadway anchor rod anchor solid，were obtained under the condition of damage and the elastic anchor solid axial force and shear stress. Based on the analytical equation obtained，the distribution law of the axial force of the anchor with the dilation Angle，that is，the roughness of the borehole wall，and the distribution law of the tangential stress with the stress field of the circular roadway are discussed. Under the same conditions，the larger the dilatation Angle is，the greater the roughness of the hole wall is，the better the tensile performance of the bolt is，and the greater the ultimate tensile force is. Moreover，the grouting pressure of the grouting bolt has an important restricting effect on the tensile force of the bolt，so it is suggested to increase the roughness of the borehole wall properly in the actual design and construction of the anchorage engineering to improve the anchorage effect and increase the grouting pressure appropriately to improve the bearing capacity of the bolt.