弱胶结软岩煤巷锚杆索-围岩变形协同控制方法研究

针对西部弱胶结软岩煤巷顶板支护易失效问题,在探究弱胶结泥岩物性组分及破坏力学特征基础上,分析弱胶结软岩巷道围岩破坏特征,揭示弱胶结软岩巷道顶板破坏失稳机理,提出弱胶结软岩高预紧力下锚杆-围岩变形协同机理,开发相应支护设计方法,并进行应用实践。结果表明:(1)弱胶结软岩黏土矿物含量高,微裂隙发育造成其强度小、黏聚力小、胶结性差、易碎胀,在低围压条件下就产生剪切滑移破坏,提高其等效黏聚力和围岩应力水平是提升其抗变形能力的最有效途径;(2)弱胶结泥岩特性、高水平应力及低锚杆(锚索)预紧力等因素综合作用下,弱胶结软岩顶板易发生整体性下沉,内部破裂严重,破裂范围最大达4.0 m,尤其是煤岩界面破裂剪胀使部分锚杆-锚索破断失效,加剧顶板破裂下沉;(3)锚杆支护作用体现在提高锚杆加固范围内岩层等效黏聚力,锚索支护则强调对其支护范围内岩层提供较强的支护应力,两者工作阻力越高支护效果越好;(4)高预紧力下锚杆与锚索联合支护时,锚杆、锚索变形与顶板变形下沉协同、相适应,且要最大程度发挥锚杆-锚索支护效能。现场应用表明,按照高预紧力锚杆-围岩形变协同支护后,弱胶结软岩巷道顶板控制效果好,达到设计预期,该方法为弱胶结软岩巷道支护提供参考。

Research on collabration control method of bolt/cable-surrounding rock deformation in coal roadway with weakly cemented soft rock

In order to solve support problem of weakly cemented soft rock,mudstone physical components are tested,and failure character?istic is analyzed.Then,based on analysis of failure characteristics of surrounding rock,its instability mechanism is revealed.Thereforce,cooperative control mechanism of bolt-cable-surrounding rock deformation under high pretension is proposed,and its design method is given and used in roadway support.Conclusions are as follows:①high content of clay minerals and developed micro-cracks cause weakly cemented soft rock with low strength,low cohesion,poor cementation,and fragile swelling.It produces shear slip failure under low confi?ning pressure.And the most effective way to improve its resistance to deformation and fracture is improving its equivalent cohesion and sur?rounding rock stress level.②Under the combined action of weakly cemented mudstone characteristics,high level stress and low bolt(ca?ble)pre-tightening force,it is prone to overall sinking,with serious internal fractures,and a maximum fracture range of 4.0 m,especially the fracture and dilatancy of the coal-rock interface,which makes part of the bolt-cable failure and aggravates the roof fracture and sink;③the role of bolt support is reflected in increasing the equivalent cohesive force of the rock formation within the reinforcement range of the bolt,while the anchor cable support emphasizes providing strong support stress to the rock formation within the support range.The higher the working resistance,the better the support effect;④the elongation of bolt or cable and roof deformation should be adaptive after it is supported,and bolt or cable elongation is in allowed range of elongation deformation.At the same time,the most supporting effectiveness of bolt or cable should be made.Field application shows that,weak cementation of soft rock roadways roof control effect is better,to meet the design expectations,and this method can provide reference for the weakly consolidated soft rock supporting.