Effect of pretensioned stress to rock bolting

Abstract

The importance of the stiffness of rock bolting in complicated and difficult mine roadways is expounded. The distribution features of stress fields caused by pretensioned stresses in bolts and cables, and the effect of steel stip on bolt pretensioned stress diffusion are analysed by the finite difference method. Several new concepts are presented such as the degree of active support, strength utilisation, pretensioned bolt length, the effective compressive zone, pretensioned stress diffusion, the framework and mesh structure of the effective compressive zone and the critical supporting stiffness. Underground tests showed that the deformation and roof delamination of roadway surrounding rock can be effectively reduced by increasing the bolt pretensioned stress. The steel strip plays an important role in the rock bolting system. There is a critical value for pretensioned stress up to and beyond which rock bolting can control the deformation and damage of the surrounding rock. 10 refs., 3 figs., 1 tab.