沿空留巷底板变形力学分析及底臌防控

Mechanics analysis on floor deformation of gob-side entry retaining and prevention and control of floor heave

上覆岩层垮落产生的动载荷通过巷帮煤体、巷内支护体以及巷旁支护体传递给底板,造成工作面后方一段距离的沿空留巷底臌变形加剧。为了控制上覆岩层垮落引起的底臌变形,在分析沿空留巷力学环境的基础上,建立底板力学模型,计算出沿空留巷煤帮弹性压缩区、塑性区、破裂区的宽度,以及煤帮对底板的作用力。应用关键层理论,确定顶板硬岩层位置及其破断顺序,以及垮断极限层的层位;采用顶板载荷条带分割法,计算出巷旁支护体对底板的作用力,并引入等效载荷的概念,构建底板等效载荷分布力学模型,将沿空留巷底臌与上覆岩层垮落紧密联系起来,分析上覆岩层垮落对底板的受力及变形影响,推导出底臌变形计算式。研究结果表明:上覆岩层垮落引起的底臌主要是由于塑性区煤体和巷旁支护体下方底板岩层高应力压剪破坏,以及巷道底板和采空区底板在强卸荷条件的拉伸破坏共同影响造成的。基于此,提出了降低塑性区煤体和巷旁支护体传递给底板的作用力,提高采空区冒落矸石对底板的作用力,防止巷道底板岩层拉伸破坏,巷旁支护体宽度、刚度与底板岩层强度相匹配等底臌防控措施,并应用于工程实践。

Dynamic loads which caused by overlying strata caving pass to the floor of gob-side entry retaining through roadside coal,entry-in support and roadside support,consequently cause serious floor heave deformation in a section behind the working face. In order to control the floor heave deformation of gob-side entry retaining which caused by overlying strata caving,on the base of analyzing the mechanics environment of gob-side entry retaining,the mechanical model of the floor was established,and the width of elastic compression zone,plastic zone,the fractured zone inside the coal rib and the forces of the coal rib to floor strata were calculated. With the application of key strata theory,the location and caving order of hard rock strata,and the location of caving limit layer were determined; also,the stripe segmentation method of roof load was adopted to calculate the force of roadside support to the floor,and the concept of equivalent load was introduced,the mechanical model of floor equivalent load distribution of gob-side entry retaining was established,the overlying strata caving was closely linked with the floor heave deformation of gob-side entry retai-ning,the influence of overlying strata caving on the stress and deformation of roadway floor was analyzed,and the floor deformation formula of gob-side entry retaining was deduced. The results show that the floor heave of gob-side entry retaining was caused mainly by the high stress pressure shear failure of floor strata below plastic zone coal and roadside support and the tensile failure of roadway floor and gob floor in strong unloading conditions. Based on this,the prevention and control measures of floor heave were put forward,such as reducing the forces of plastic zone coal and roadside support to the floor,improving the force of caved gangue to the floor,preventing the floor strata of roadway from tensile failure,matching the width and stiffness of roadside support with the strength of floor strata. The research results were applied to the engineering practice to provide some references for the prevention and control of the floor heave of gobside entry retaining.