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为研究煤层巷道围岩失稳过程及裂隙演化特征,并对支护方式选择提出建议,通过数值模拟获得工作面附近围岩应力分布特征,并将围岩受力状态简化成平面应变问题、准平面应变问题和三维复杂应力问题3种。采用自行研制的相似材料模拟试验台及煤岩体细观力学试验装置,分别针对平面应变和准平面应变2种应力状态下煤岩体的破坏过程及裂隙演化特征进行试验研究。结果表明:1)层状围岩梯形巷道受载失稳存在3个阶段,即楔形破坏阶段、滑移失稳阶段、顶底板大挠度断裂阶段。高垂直应力条件下,顶、底板初始变形造成两帮出现明显剪切滑移后,直接顶、底板分别出现“三铰拱”形态冒落及鼓胀断裂。2)准平面应变条件下,煤体自由端首先出现张拉破裂失稳,造成上覆直接顶砂岩受力不均,并出现一次弯曲断裂;随载荷增大,煤体出现滑移失稳并呈现出“弧线”压出形态,顶板砂岩发生断裂;裂隙煤体与砂岩反复作用形成多对贯通裂隙,说明顶板断裂位置、形态与煤体失稳过程具有显著的对应关系。结合压剪和拉伸破坏机理,对单一煤层巷道和沿空留巷煤层巷道围岩的支护进行分区研究,并提出相应的支护建议。
In order to study the instability process of surrounding rock and the evolution characteristics of fissures in coal roadway, and to make suggestions on the selection of support modes, the stress distribution characteristics of surrounding rock near working face are obtained through numerical simulation. The stress conditions of surrounding rock are simplified to plane strain problem. Plane strain problems and three-dimensional complex stress problems 3 kinds. A similar material simulation test bench and coal-rock mesomechanics test device developed by ourselves were used to conduct experimental research on the destruction process of coal mass and the evolution of fracture under two kinds of stress states of plane strain and quasi-plane strain respectively. The results show that: (1) There are three stages of the load-bearing instability of the trapezoidal surrounding rock, namely the wedge failure stage, the slip failure stage and the roof-floor large-deflection fracture stage. Under the condition of high vertical stress, after the initial deformation of the top and bottom plates caused the obvious shearing and slippage of the two groups, the “top and bottom” plates appeared “three-hinged arch” and the bulges and fractures ruptured respectively. 2) Under quasi-plane strain, the tensile failure and instability of the free ends of the coal occur first, which results in uneven stress on the overlying overlying roof sandstone and a first bending fracture. With the increase of load, Showing the “arc” extrusion shape, the roof sandstone fractures; cracked coal and sandstone repeatedly formed multiple pairs of through cracks, indicating the roof fracture location, morphology and the process of instability of coal has a significant correspondence. Combined with the mechanism of the compression shear and the tensile failure, the research on the support of the surrounding rock of the single coal seam roadway and the gob-side entry coal seam roadway is carried out and the corresponding support suggestions are put forward.