基于巷道围岩自承特性的锚杆锚固效果研究

Study of bolt anchoring effect based on self-bearing characteristics of roadway surrounding rock

现有锚杆锚固效果研究很少关注整体锚固围岩的自承载特性。巷道围岩切向应力σθ对围岩承载结构的力学变化反应灵敏,研究了锚杆长度和锚杆强度对切向应力σθ曲线变化的影响,可为研究锚杆锚固效果提供重要参考依据。整体锚固巷道围岩σθ曲线形状与锚固端所处弹塑性围岩位置有关,当锚固端在塑性区内,对σθ曲线的峰值位置和大小影响不大;随着锚固端向弹性区深入,σθ分布曲线形成内外两个峰值,锚固巷道围岩出现弹塑性交替的现象。同时,锚杆强度与围岩自承强度存在一定程度的匹配关系,相应地提出了通过锚固σθ曲线的双峰值来判别锚杆锚固效果的新方法,该方法能较好地解释软弱地层条件下取消系统锚杆布置的问题。

The current researches on bolt anchoring effect are rarely concerned with self-bearing characteristics of whole anchorage surrounding rock. For its sensitive response to mechanical changes of surrounding rock bearing structures, tangential stressσθcurve with different bolt lengths and different bolt strengths is researched, which can provide important references to research the bolt anchoring effect. The σθcurve shape of whole anchorage roadway is related to the anchorage end position in elastic and plastic surrounding rock. When bolt anchorage end is located in the plastic zone of surrounding rock, the peak value and its corresponding position ofσθcurve are slightly influenced. With the increasing of bolt anchorage end depth in the elastic zone, distribution curve ofσθwill have internal and external peak values from the surface to the depth of anchorage surrounding rock gradually; and its alternative elastic and plastic zones gradually appear. And bolt strength should match the self-bearing strength of surrounding rock. Accordingly, a new method to determine the bolt anchoring effect based on the double peak values of σθcurve of anchorage surrounding rock is put forward, which can well explain the problems of canceling the systematic anchor bolts in weak strata.