预应力在锚杆支护中的作用

Effect of pretensioned stress to rock bolting

在分析目前复杂困难条件下锚杆支护存在问题的基础上,论述锚杆支护系统刚度,特别是预应力对支护效果的重要性.采用有限差分数值计算软件分析了不同预应力下锚杆、锚索产生的应力场分布特征,以及钢带对锚杆预应力扩散的作用.提出锚杆主动支护系数、强度利用系数、预应力长度系数、有效压应力区、预应力扩散系数、有效压应力区骨架网状结构及临界支护刚度等概念.井下试验表明,大幅度提高锚杆预应力可显著减小巷道围岩变形,有效控制顶板离层;钢带在预应力支护系统中起非常重要的作用;锚杆预应力存在临界值,达到或超过临界值后锚杆支护可有效控制围岩变形与破坏.

Based on the analysis on existing problems of rock bolting for complicated and difficulty roadways, the importance of rock bolting stiffness, especialy the pretensioned stress to bolting effects was expounded. The distribution features of the stress fields caused by the pretensioned stresses of bolts and cables, and the effects of steel strip to the bolt pretensioned stress diffusion were analyzed through finite difference numerical modelling. The new concepts, such as the active supporting coefficient, the coefficient of strength utilization, the coefficient of pretensioned bolt length, the effective compressive zone, the coefficient of pretensioned stress diffusion, the framework and mesh structure of the effective compressive zone, and the critical supporting stiffness were put forward. The underground tests show that the deformation and roof delamination of roadway surrounding rock can be effectively reduced by means of great increase of the bolt pretensioned stress, the steel strip plays an important role in the rock bolting system, and there exsits a critical value for pretensioned stress, up to or beyond which the rock bolting can effectively control the deformation and damage of the surrounding rock.