基于弯曲模式的层状采动斜坡变形破坏机理研究

Study on Deformation and Failure Mechanism of Stratified Mining Slope Based on Bending Mode

为揭示采空区反倾斜坡变形破坏机理,针对采空区顶板层状岩体提出固定梁约束模型,并根据已有研究给出其基于结构力学和最大拉应力准则的弯曲折断应力判据。为验证约束模型的效果,以纳雍左家营崩塌为例,在详细地质调查的基础上,选取典型地质剖面1-1′剖面,对面积最大的1号采空区顶板每隔10 m取一个计算点,计算出固定梁约束模型下采空区顶板不同位置处的弯曲折断应力,同时利用FLAC;对其进行数值模拟,最后综合结构力学计算结果、数值模拟结果和地质调查对左家营崩塌机理进行分析。研究结果表明:固定梁可作为采空区顶板反倾层状岩体的受力模型,采空区顶板受力由固定梁向简支梁转化;采空区两侧端面应力集中现象明显,且应力集中朝顺倾向偏移,顺倾向应力集中较反倾向显著,采空区顶底板中部局部呈受拉状态,塑性区以剪切破坏为主;上硬下软不利岩性组合和节理裂隙发育的岩体造成的岩体结构破碎是崩塌源区形成的关键因素,高度临空的斜坡地形为崩滑提供了有利地形,采空区应力调整导致已有裂缝裂隙不断扩展、贯通,加剧斜坡失稳,最终形成崩塌。

In order to explore the deformation and failure mechanism of anti-dip slope in goaf, the constraint models of the fixed beam were proposed for the layered rock mass of goaf roof. The stress criterion of bending and fracture based on structural mechanics was derived respectively from the constraint models. In order to verify the constraint models, it took Zuojiaying collapse in Nayong county, Guizhou, China as an example. On the basis of the detailed geology survey, typical geological 1-1′ section was selected to verify the models. The bending fracture stress of the largest gob roof was calculated at every 10 m point using the constraint model of the fixed beam. At the same time, the FLAC;was used to numerically simulate the bending process. Finally, the mechanism of Zuojiaying collapse was analyzed by combining the results of structural mechanics calculation, numerical simulation and geological survey. The results show that the stress characteristic of the inverted stratified rock mass in the goaf is a fixed beam, and the stress characteristic of the inverted stratified rock mass away from the goaf is a cantilever beam. The stress concentration on both sides of the goaf is obvious, and deviated towards the dip direction. Meanwhile, the stress concentration in the dip direction is more obvious than the anti-dip direction. The middle part of the roof and floor of the goaf is in tension, and the plastic area is mainly in shear failure. Hard and soft lithology combination and developed joint fissures cause rock mass structure broken. It is the crucial factor for the formation of collapse. High and steep topography of slope provides a favorable terrain for collapses. The goaf stress adjustment results in crack fracture expanding, and cutting through. Finally, it aggravates slope instability and collapse.