综放工作面区段煤柱采动应力全周期时空演化分析

Mining stress full-cycle temporal and spatial evolution analysis on section coal pillar of fully-mechanized caving face

三向采动应力的大小、方向演化过程是揭示煤柱损伤破坏机制的关键。将综放工作面区段煤柱分为上部与下部2个区域,采用3DEC数值模拟方法,分析巷道开挖–右侧工作面回采–左侧工作面回采–回采稳定4个阶段煤柱三向采动应力全周期时空演化规律,揭示煤柱上覆岩层断裂结构–采动应力–位移的映射关系。基于模拟分析结果,采用莫尔–库仑强度准则分析煤柱莫尔应力圆的变换形式及莫尔圆与强度包络线的关系,确定煤柱的破坏深度约为8 m。研究结果表明:工作面煤层开采导致煤柱的三向主应力方向发生了大幅旋转,煤柱三向主应力数据呈现明显的两簇或三簇的规律,数据簇的分割点为右侧工作面推进至测线位置及右侧工作面回采完毕。工作面推进顺序不同导致煤柱上覆岩层的断裂结构呈现明显的非对称性,上覆岩层的断裂线向后开采的工作面进行偏移,导致煤柱左侧测点的水平位移量明显大于煤柱右侧测点。煤柱采动应力全周期时空演化规律及覆岩断裂结构–采动应力–位移的映射关系为揭示煤柱损伤破坏机制奠定了基础。

The evolution process of the magnitude and direction of three-dimensional mining stress is the key to reveal the damage and failure mechanism of coal pillar.The coal pillar between the fully mechanized top-coal caving faces was divided into upper and lower areas.There were four stages:roadway excavation-right longwall face mining-left longwall face mining-mining stability.The 3DEC numerical simulation method was used to analyze the full-cycle temporal and spatial evolution law of three-dimensional mining stress of coal pillar in these stages.The mapping relationship between the fracture structure of overlying strata,mining stress and displacement of coal pillar was revealed.Based on the simulation analysis results,the Mohr-Coulomb strength criterion was used to analyze the transformation form of Mohr stress circle of coal pillar and the relationship between stress circle and strength envelope.The failure width of coal pillar was determined to be about 8m.The results show that longwall face mining causes the three-direction principal stress direction of coal pillar to rotate greatly.An obvious two-cluster or threecluster rule was showed in the three-dimensional principal stress data of coal pillar.The division points of the data clusters correspond to the time when the right longwall face is advanced to the survey line and when the mining of right longwall face ends.The obvious asymmetry in overlying fracture structure of coal pillar was caused by the different mining sequences of longwall face.The fracture line of the overlying strata is biased towards the longwall face which is mined later.As a result,the horizontal displacement of the measuring point on the left side of coal pillar is significantly larger than that on the right side of coal pillar.The full-cycle temporal and spatial evolution law of coal pillar mining stress and the mapping relationship between the fracture structure of overlying strata,mining stress and displacement of coal pillar lay the foundation for revealing the damage mechanism of coal pillar.