浅埋煤层超大采高开采柱式崩塌模型及失稳

Instability of pillar collapse model and generation of cracks in thick coal seam mining at shallow depth

为认清西部典型浅埋条件下覆岩致裂机理及定量分析失稳条件,基于相似模拟试验开展浅埋深薄基岩厚松散层超大采高采动裂隙演化研究。提出采动裂隙柱式结构并揭示柱式结构生成机制。基于支架工作阻力,指出周期来压期间,柱式结构的形成给支架带来了巨大的压力,波浪式特征明显,是导致压架发生的主要原因。依据破裂角演化规律,揭示切顶线破裂角较大,切落特征明显,易促成垂直柱式结构的形成。提出岩柱失稳的3种主要方式:拉裂式崩塌失稳、滑移失稳及倾覆失稳。推导了2种模式的不同失稳模型的稳定系数表达式。对于上覆软土、砂情况,最有可能发生的是拉剪混合型,然后是纯拉型;对于上覆硬土情况,最有可能发生的是纯剪型。从2种模型失稳模式可以看出,倾覆失稳的稳定系数最容易小于1,因此也是最容易发生的,其次是拉裂式崩塌失稳。

Mining-induced cracks in thin bedrock at shallow depth have been studied based on physical modeling to learn failure mechanism and instability quantitatively. A model of pillar structure of overburden rock was proposed and the formation mechanism was described. According to the resistance of working support,it is pointed out that during the occurrence of periodic pressure the support compressed by tremendous pressure from pillar structure fails with wave characteristics. Based on the evolution of rupture angle,it is revealed that rupture angle is large at the cutting roof line easily leading to the formation of a pillar structure. There are three failure ways of pillar instability including tensioninduced collapse,sliding-induced instability and overturning-induced instability. Due to the constrained lateral displacement by the hardness or softness of soil or sand,two modes of pillar structures are proposed to explain different stability coefficients. For soft model,tensile-shear mixed type is most likely to happen,then a tensile type. For hard condition,only a shear type most likely happens. It is found out that overturning-induced instability is easier to happen in both models followed by tension-induced collapse.