中文摘要：

为研究软弱岩体中隧道开挖引起的围岩失稳破坏特征以及锚杆的加固效应,以IV级围岩为参照对象,开展一系列无锚杆和有锚杆支护条件下的隧道开挖地质力学模型试验,并对拱顶围岩的位移、应力和宏观破坏形式的发展变化规律进行分析。研究结果表明：（1）隧洞开挖后,围岩破坏始自隧道两侧拱脚,渐次向上延伸并塌落成拱;（2）由于锚杆的悬吊挤压作用及其与岩层的组合梁效应,显著减少了拱顶岩体塌落范围;（3）锚杆通过对岩体施加黏锚力,提高了锚固范围内岩体的强度和韧性,有利于增强围岩的承载能力和抵抗变形能力;（4）锚杆支护对围岩应力分布起调节作用,使得围岩能在较高的能量状态下获得稳定平衡,并延缓了围岩进入＂软化＂阶段。上述研究成果可为软弱隧道围岩稳定性评价以及支护结构的设计与施工提供一定的借鉴和参考作用。

英文摘要：

In order to study the failure characteristics of weak rock mass and the anchoring effect of rock bolts,a series of geomechanical model experiments were carried out to simulate tunnel excavation in rock mass of grade Ⅳ,which includes two modes,unsupported and supported with bolts. Subsequently,the evaluation laws of displacement,stress and the macroscopic failure forms of the surrounding rock mass were analyzed through a comprehensive comparison. According to the experiment results,the following conclusions can be drawn.（1）The damage of surrounding rock induced by tunnel excavation starts from tunnel arch foot,extending upwards gradually and collapsing into arch eventually.（2） Due to the anchor suspension and extrusion effect of bolts combined with the rock beam effect,the rock collapse zone can be reduced significantly.（3） The bolts can improve the strength and toughness of rock mass owning to the applied anchor force,which is conducive to enhance the bearing capacity and the deformation resistance ability of surrounding rock.（4） The bolts can make the surrounding rock obtain a stable equilibrium with high energy,which not only makes the stress distribution in rock mass more balanced,but also delays the rock entering into the ＂softening＂ stage. The conclusions gained can provide references for the stability evaluation of soft rock mass during tunnel construction as well as the design and construction of the supporting structures.