沿空留巷围岩结构稳定性力学分析

以往对沿空留巷围岩结构特征了解不够,难以准确计算巷旁支护阻力,导致沿空留巷困难甚至失败。因此,根据沿空留巷上覆岩层垮断特征,提出了"大结构"、"小结构"概念,分别构建了围岩"大结构"、"小结构"力学模型,研究分析了"大结构"形成"低形态拱"和"高形态拱"的条件,推导出了拱高计算式,研究认为:在巷旁顶板岩层残留边界二次破断前,若及时加固煤帮,提高巷内和巷旁支护阻力,则上覆岩层易形成"低形态拱";若巷道煤帮松软,或巷道支护阻力不足,则易形成"高形态拱"。通过研究拱脚的水平力对"大结构"形态演化及其稳定性影响,发现拱脚处的水平力是造成拱破坏的主要原因,若拱脚处的水平力大于其抗剪力,拱将失稳破坏,造成"低形态拱"的拱高增加或"高形态拱"的跨度向外扩展,引起"小结构"的岩层载荷增加,"小结构"的岩层载荷不仅与"大结构"的形态、拱高和跨度相关,而且与二次破断区顶板"铰接岩层"的稳定性密切相关,根据关键层理论,确定"大结构"拱高范围内顶板硬岩层位置及其所控制的软岩层组,采用滑落失稳判据和挤压变形失稳判据,自上而下判别出顶板"铰接岩层"的稳定性,进而确定围岩"小结构"的岩层载荷,据此推导出巷旁支护阻力计算式。

Mechanical analysis on the stability of surrounding rock structure of gob-side entry retaining

Analyzing thoroughly the characteristics of surrounding rock structure,calculating accurately roadside supporting resistance,and controlling serious deformation and failure of rocks surrounding,lead to supporting difficulty in gob side entry retaining increased,even fail.Therefore,based upon the breaking off characteristics of overlying rock,the mechanical models of big and small structure were built,the formation conditions of low arch and high arch were analyzed,the formulas of their arch rise were derived,and the effect of horizontal force at arch foot on form evolvement and the stability of big and small structure.Research suggested that before the residual boundary of roadside roof the second broke off,if the coal side of roadway was strengthened timely and roadway inside and roadside supporting resistance were improved,then overlying rock was easy to form low arch;if the coal side of roadway was soft,or the supporting resistance of roadway was insufficient,then overlying rock was easy to form high arch.Horizontal force at arch foot was the main reason of arch instability,if horizontal force at arch foot was larger than shearing resistance at arch foot,then the arch would lose stability,consequently the arch rise of low arch or the arch span of high arch would increase,which caused the overburden load of small structure increase.Overburden load of small structure was not only related to arch form,arch rise and arch span of big structure,but also closely related to the stability of articulated rock of roadway roof in secondary breaking off zone.Based on this,combining with the key strata theory,the locations of hard rock layers and their controlling soft rock group within the scope of arch rise were determined,using slide instability criterion and extrusion deformation instability criterion,the stability of articulated rock of roadway roof was identified from above to below,the overburden load of small structure was determined,and accordingly the reasonable formula of roadside supporting resistance were derived.