大采高采场覆岩破断演化过程及支架阻力的确定

Overlying strata failure process and support resistance determination in large mining height face

基于煤岩体"强度参数-应力环境-节理弱面"破坏控制条件研究了大采高采场覆岩变形破断特征,并通过室内试验再现采动引起覆岩破断后运动演化过程,最后根据顶板结构形态对支架工作阻力确定方法进行了理论分析。研究表明:覆岩薄弱岩层冒落取决于层间离层裂隙的发育范围,基本顶表现出固支梁变形破坏特征,断裂线位置则取决于剪切错动裂隙的发育范围;软弱岩层中受拉应力区贯通分布,坚硬岩层中呈孤岛式分布,分布形态同离层和剪切错动裂隙的发育范围相关;层间拉伸张开型裂缝则呈小范围正梯形滞后工作面发育,剪切闭合型裂缝呈大范围倒梯形超前工作面发育;大采高采场下位基本顶破断后形成单关键块结构,更高位基本顶可形成静定三铰拱结构,采场顶板控制关键为前者的稳定性;以单关键块结构形成条件为基础给出直接顶范围确定方法,基于能量守恒原理、直接顶性质提出顶板压力确定公式,直接顶力学参数对其影响程度依次为:黏聚力>塑性模量>内摩擦角。

Based on the failure control conditions of ＂intensity parameters-stress environment-weak planes of joints＂ in coal-rock mass, the failure characteristic of overlying strata in large mining height face was studied, the simulation of failure process was conducted in the laboratory, and the determination of support resistance was theoretically analyzed. The following conclusions can be made： The caving of layers with thin and low strength depends on the scope of abscission layer, the main roof is characterized by the deformation feature of the clamped beam, and the position of fracture line depends on the scope of shear dislocation fracture. Tensile stress shows a continuous distribution type in thin and low strength strata, whereas a non-isolating distribution type is presented in thick and high strength strata. Shear-closed interlaminar fracture develops prior to the face as an inverted trapezoidal form in large scale, whereas tension-open fracture develops inferior to the face as an upward trapezoidal form in small scale. After fracturing, the lower main roof can form single key block structure and the higher main roof can form static three-hinged arch, and the stability of lower main roof is the key of roof control. Determination of the range of immediate roof is put forward according to the condition of single key block structure in lower main roof, the computational formula of roof pressure is deduced based on the principle of conservation of energy, and the influential degree of immediate roof property on each parameter is thus determined： cohesion plastic modulus friction.