Correlation Between Roof Deformation And Water Inflow Based On “Stress-seepage-damage” Coupling

The roof of some coal mines in Guangxi is affected by the upper confined aquifer and mining stress,and it is challenge to the safety of mining operations.Based on the multi-physical field coupling principle of "stress Seepage Damage",We uses COMSOL software to build a numerical model to study the correlation between roof deformation and water inflow in the 4103 working face of No.3mine of Guangxi Heshan Guineng Energy Co.,Ltd.under different face length,head pressure and mining distance,to solve the complex problems of coal seam mining under confined water and provide a reference for safe mining of working faces under similar conditions.The results are as follows:(1)The water inflow is closely related to the length of the working face.With the increase of the length of the working face,the earlier the initial time and the faster the change,the higher the possibility of water inrush;The maximum stress is positively correlated with the head pressure.With the advance of the working face,the maximum stress fluctuates and rises.There is an obvious stress concentration at both ends of the goaf and the roof above the goaf;The plastic deformation of the roof is positively correlated with head pressure and mining distance;The water inflow is positively correlated with head pressure and mining distance.(2)The plastic deformation of the roof can be divided into four period:firstly,the plastic deformation occurs at the lower part of the roof,which is in the shape of an arch bridge with a small deformation variable;Then the plastic deformation of the lower part of the roof increases,and the upper part develops into a closed circle;Then,the plastic deformation of the roof enters the stage of rapid development,and the two parts of the plastic deformation zone are connected until the through crack appears and expands continuously;Finally,a new plastic deformation zone appears on the roof,but it is not connected with the original plastic deformation zone.(3)There is an obvious correlation between the water inflow and plastic deformation.When the water inflow increases abruptly,the key plastic deformation occurs in the roof,and there are cracks.Affected by mining and head pressure,the maximum stress value fluctuates and rises rapidly,and the crack initiation and expansion occur in the roof rock stratum,which destroys the continuity of the roof rock stratum,and the connection of the water diversion channel induces the sudden increase of water inflow.