软硬互层岩体采场底板的应力分布及破坏特征研究

Research on stress distribution and failure characteristics of coal mining floor in soft-hard alternant strata

考虑底板岩体分层特性,将采场底板视为弹性层状半无限平面体,采用传递矩阵法建立层状底板的应力计算模型。用Matlab编制了相应的计算程序,求解得到不同分层深度处的底板应力分布,根据Mohr-Coulomb准则判断底板塑性区分布。新建模型考虑了不同底板岩性及其组合条件,理论计算得到的底板破坏深度比传统方法更符合实际,建立不同的软硬互层采场底板模型,分析了岩体的软硬性质对采场底板应力分布和破坏特征的影响。研究结果表明,硬岩底板对支承压力具有降低和扩散作用,降低作用减小了底板深处应力,有效地抑制了采场底板破坏深度;扩散作用加大了下卧岩层的应力影响范围,导致下卧岩层破坏范围增加,软岩底板由于其承载能力弱,会加剧底板应力的集中程度,导致底板岩层的破坏深度和范围都大大增加。

Considering the layered characteristics of mining floor, the floor strata are equivalent to layered semi-infinite plane. A stress calculation model of multilayer floor strata is proposed based on the transfer matrix method. The corresponding calculating program is written by Matlab to calculate the stresses of multilayer mining floor strata. And the plastic zone of mining floor is determined by the Mohr-Coulomb yield criterion. The proposed model take into account the rock lithology and its composite structure of floor strata, so the calculation result of failure depth is more closer to the actual situation than the traditional method. Then different calculating models are established to study the influence of rock properties of the floor strata on the stress distribution and failure characteristics of mining floor. The results show that the hard rock has the reducing and dispersing effect on the abutment pressure. The reducing effect can cause lower stress in the deep floor strata, and inhibit the failure of mining floor. The dispersing effect can expand the influence scope of stress in underlying strata, and widen the failure scope of underlying strata. In soft rock with low load-bearing capacity, will aggravate floor stress concentration, so as to increase the scope and the depth of failure zone in the floor strata.