Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method

In longwall top coal caving (LTCC), the resource recovery ratio of working face is directly determined by ratio. An investigation evolution drawing characteristics and revealing parameters necessary when providing guidance for parameter selection improving Based on in-situ measurements size distribution caved blocks in Wangjialing mine, a finite difference method (FDM)–discrete element (DEM) coupled was applied to establish “continuous–discontinuous” numerical model process from first common simulated with 17 separate advances. The body (DB), loose (LB), boundary (TCB) obtained. results show that, DB such as shape size, amount, length deflection angle long axis profile ellipsoid tended decrease first, then increase, again, finally stabilise; increment LB advance wall distance pillar close 0 m stage, while width interval (0.865 m). TCB formed after each round fitted based improved “Hook” function. height radius curvature TCB’s stagnation point analysed. This divided into three stages: (first third rounds) initial mining influence second (fourth ninth transitional (after tenth round) stage.