锚杆拉拔过程中径向力学响应特征研究

Characteristics of radial mechanical responsein rock bolt pullout test

锚杆径向力学响应特征对揭示锚杆拉拔破坏机制和丰富当前支护设计理论有十分重要的意义。为了深入探究锚杆拉拔过程中锚固界面的径向力学响应,开展了不同等效围岩条件的套筒拉拔试验,通过应变片监测试验过程中套筒的周向应变计算得到拉拔过程中砂浆-围岩界面径向应力。试验发现砂浆-围岩界面径向应力-拉拔位移曲线分为两种:(1)围岩弹性模量较大时,径向应力随拉拔位移的增大而增大,越过峰值点后先短暂下降,然后又缓慢增大;(2)围岩弹性模量较小时,径向应力随拉拔位移的增大而增大,越过峰值点后逐渐减小。锚杆拉拔承载力和砂浆-围岩界面峰值径向应力均与等效岩体弹性模量存在明显的线性关系,通过拟合得到了其经验公式,同时对比分析了拉拔力-拉拔位移曲线和径向应力-拉拔位移曲线,并对现象做出了解释。

The radial mechanical response characteristics of rock bolts are of great significance to reveal the failure mechanism of rock bolt pullout and enrich the design theory of rock bolt support.In order to further study the radial mechanical response of rock bolt under different surrounding rock conditions,a cylindrical sleeve pullout test was carried out.The strain gauge was used to monitor the hoop strain of the sleeve,and then the hoop strain was derived to obtain the radial stress of the mortar-surrounding rock interface.It was found that the radial stress pullout displacement curve of the mortar-surrounding rock interface could be divided into two types:(1)when the elastic modulus of surrounding rock was large,the radial stress increased with the increase of drawing displacement,after crossing the peak point it decreased briefly and finally increased slowly.(2)when the elastic modulus of the surrounding rock was small,the radial stress increased with the increase of the drawing displacement,and gradually decreased after crossing the peak point.The drawing bearing capacity and the peak radial stress were linearly related to the equivalent elastic modulus of the surrounding rock and the empirical formula was obtained by fitting.At the same time,the drawing force-displacement curve and the radial stress-displacement curve were compared and analyzed,and the phenomenon was explained.