软弱破碎顶板巷道围岩变形机理及控制技术

Deformation mechanism and control technology of surrounding rock in soft and broken roof roadway

针对软弱破碎顶板巷道支护困难的问题,通过现场调查和钻孔探测发现软弱破碎顶板巷道围岩具有自稳平衡拱结构,但极不稳定,在扰动作用下表现为局部到整体的连锁失稳特征。现场取样进行试验,发现顶板破碎岩块强度低,帮部煤块裂隙发育、底板泥岩软弱是造成巷道全断面变形失稳的主要原因。原支护棚架架型不合理、接顶效果差、支护缺乏整体性以及支护系统不能协调变形是导致巷道失稳的直接原因。进一步试验表明,该巷道的软弱破碎岩样在侧限约束条件下压实后具有较高的承载能力,在无侧限约束条件下则难以自稳。掺入一定水泥进行胶结后形成的弱胶结岩体,其稳定性和承载能力有明显提高。结合普氏自然平衡拱理论和"类双曲线"模型,构建了软弱破碎顶板巷道围岩"抛物线-半双曲线"破碎边界扩张模型,发现软弱破碎顶板载荷呈指数形式增长,当帮部煤体不稳定时顶板载荷急剧增加,而底鼓是造成帮部失稳的重要因素。因此,提出了强力控制软弱破碎顶板,强化约束帮部煤体,加强隔水预防巷道底鼓的控制原理和"控顶先固帮,固帮先护底"的支护原则。针对州景煤矿5305工作面的实际情况提出了"双层金属网+喷射混凝土+预支撑囧形棚架+可缩性纵向连接器"的组合控制技术,经初步的现场工程实践,取得了较好的支护效果。

In view of the difficulty of supporting the roadway with weak and broken roof,it is found,through field investigation and borehole exploration,that the surrounding rock of weak broken roof roadway has a self-stabilizing and balanced arch structure,but it is extremely unstable. On-site sampling and testing showed that the low strength of the roof rock block,fracture development of the coal block of the ribs and the weak mudstone of the floor were the main reasons for the instability of the full-section deformation of the roadway. The unreasonable shape of the original support scaffold,poor roof connection,lack of integrity of the support,and inability to coordinate and deform the support system were the direct causes of roadway instability.Further tests show that the weak fractured rock sample of the roadway has higher bearing capacity after compaction under lateral restraint conditions,and it is difficult to self-stabilize without lateral restraint conditions. The weakly cemented rock mass formed by cementing with a certain cement has a significant improvement in its stability and load-carrying capacity.Based on the Pushl’s natural equilibrium arch theory and the " analogous hyperbola" model,a " parabolic-semi-hyperbolic" fracture boundary expansion model for the surrounding rock of weak broken roof roadway was constructed. It is found that the load of the weak broken roof increases exponentially. When the coal is unstable,the roof is unstable. The load increased exponentially. The load on the top plate increases sharply during stabilization,and the floor heave is an important factor that causes the instability of the upper part.Therefore,it is proposed to strongly control the weak broken roof,strengthen the restraining of coal seamin the ribs,strengthen the control principle of preventing floorheave of the roadway and the supporting principle of " stabilizing solid ribs first for controlling the top,preventing the bottom first for stablizingsolid ribs". According to the actual situation of the No.5305 working face of Zhoujing coal mine,the combined control technology of " double-layer metal mesh + shotcrete + pre-supported truss scaffold + shrinkable longitudinal connector" was proposed. Through preliminary field engineering practice,good supporting effect has been achieved.