节理围岩特性及其锚固效应模型试验研究

RESEARCH ON BEHAVIOUR AND ANCHORING EFFECT OF JOINTED ROCKMASSES AROUND AN UNDERGROUND OPENING UNDER EXCAVATION BY MODEL TESTING

通过堆砌尺寸为１８０ｃｍ×１４０ｃｍ×１５ｃｍ的大比尺结构模型，依据两组正交节理的不同倾角和间距、地应力及洞周有无锚杆等不同组合的１６种工况进行地下洞室分步开挖模型试验，研究节理对洞室围岩变形破坏的影响及锚杆对节理围岩的锚固效应．试验首次应用ＣＣＤ画像处理法和光学照相法进行位移观测．结果表明，岩体的变形大部分是由节理变形引起的，围岩塌落区完全由开挖自由面与节理的不利组合所控制，围岩变形主要由洞室尺寸、节理倾角及间距、地应力等决定．锚杆能大幅度减少围岩的变形破坏，垂向位移减少更甚，预应力锚杆使围岩变形进一步减小．

This paper deals with large-sized simulation tests concerning opening excavation by step in a jointed rockmass and bolt-reinforcement of the opening. The testing model is sized 180cm×140cm×15cm and is tested under 16 different working conditions. The varying factors of these conditions are: dip of two orthogonal joint sets, joint spacing, initial stress field,installing or not installing bolt-anchoring. CCD image processing technique and high-accurate photo technique are firstly performed. The results indicate that the deformation of rockmass is mostly governed by the deformation of joints and the collapsing areas of surrounding rocks are completely controlled by unfavourable combination of free excavation surfaces and discontinuities. The deformation of surrounding rocks is mainly determined by the sizes of opening, dip and spacing of joint sets, initial stress field, etc.. Rock bolts can greatly decrease deformation (esp. the vertical deformation) and failure of surrounding rocks. The pre-stress bolts can further decrease deformation of surrounding rocks.