预紧力锚杆作用下锚固体的形成与失稳模式

Anchor bolt body formation and instability mode under the influence of anchoring pretension

高强锚固系统在深部及复杂软弱巷道围岩控制中得到越来越广泛的应用,但对该条件下的锚固体形成和失稳的认识仍不充分。笔者采用数值模拟方法研究了预紧力锚杆作用下锚固体的形成因素及原岩应力作用下锚固体的失稳规律。结果表明:预紧力一定时,锚杆间距越小,附加应力就越大;锚杆间排距一定时,预紧力越大,附加应力就越大,附加应力在锚固体范围岩体中呈纺锤形,压力从巷道表面处逐渐衰减,在锚固起始端呈锥形分布;锚固段越短或预紧力越大,压缩区域就越大,锚固体的范围就越大,但锚固段长度对锚固体的影响较为明显。原岩应力环境中,巷道围岩锚固体失稳类型有锚杆断裂型、锚固脱黏型、岩体主导破坏型和锚固体复合型破坏型;岩体强度、锚杆预紧力、原岩应力侧压系数、埋深、锚杆间排距等对锚固体失稳的作用依次减小。

With high strength anchor system being widely applied for rock control in the deep and complex soft roadways,whereas insufficient recognition has been attained as far as the anchoring bolt body formation and destabilization are concerned. Adopting numerical simulation,authors studied the formation factors of the anchor in the use of pretension and the destabilization mechanisms of the anchor resulting from the in-situ stress. The results indicate that when the pretension is fixed,the smaller the bolt spacing is,the stronger the induced stress will be. The induced stress shapes as spindle in the range of rock anchored,whist the stress gradually decreases from the surface of the roadway,therefore the stress distributing in 'cone'shape at the anchor head. When the anchor area is rather confined or the pretension is rather strong,compression zone and the anchoring range will be expanding. However,the length of the anchoring area has dramatic influence on the anchor bolt body. In the context of in-situ stress,the types of instable anchor solid consist of anchor bolt rupture type,anchoring debonding type,rock dominant failure type,anchor solid composite failure type. In a descending order,the rock strength,bolt pretension,side pressure coefficient of in-situ stress,the cover depth,and bolt spacing will destabilize the anchor bolt.