浅埋深薄基岩煤层组开采采动裂隙演化及台阶式切落形成机制

Stepped shearing-induced failure mechanism and cracks propagation of overlying thin bedrocks in shallow deep coal seams mining

探索浅埋深薄基岩煤层组开采采动裂隙演化对认识溃水溃砂通道形成机制具有指导意义。基于大柳塔矿地质条件,设计相似模拟试验,首采1-2上煤层,充分开采后再采1-2煤层。由此,揭示采动裂隙演化规律,指出上煤层采动碎胀作用明显,下煤层采动地表下沉线性增长明显。利用分形与逾渗理论定量评价了采动裂隙的演化特征。上煤层开采,根据周期来压特征,分维变化划分2个线性阶段。下煤层开采,非线性受控于上覆煤层引起的分维变化,分形维数将趋于一个稳定值。进一步揭示了采动裂隙逾渗概率随推进度的线性关系的,得到整个煤层组开采覆岩裂隙非线性演化的2个临界状态。研究了切落式破坏形成机制,提出了岩层板簧效应并分析了崩塌式切落特征,指出拉破坏是典型切落式台阶形成的主要原因。

To study on the cracks propagation of overlying thin bedrocks in shallow deep coal seams mining is useful for understanding the stepped shearing-induced failure mechanism of overlying thin bedrocks. Based on the geology in Daliuta coal mine,the physical model was designed for mining 1-2upcoal seam first,then 1-2 coal seam below. The analysis on the evolution of mining-induced cracks was made in the study. Broken-induced volumetric expansion is obvious in mining the upper coal,as well as surface subsidence increases in mining the lower coal. According to periodic weighting,there are two linear stages of fractal dimension in mining the upper coal. After mining the lower coal,the fractal dimension will tend to be a stable value. Furthermore the percolate probability shows a linear relationship with the advancing distance,and two critical states have been obtained. Finally the study on the formation mechanism of stepped shearing-induced failure is made. The rock seam spring effect and tension-induced collapse are proposed,and the main reasons about stepped shearing-induced failure by tension are provided.