Failure characteristics of stope floor and grouting reconstruction of Ordovician limestone aquifer roof in Weibei Coalfield

WANG Xingming; GU Shuancheng; LIU Yingfeng; GUO Kang; WANG Qi

doi:10.13347/j.cnki.mkaq.20250455

Abstract：With the continuous expansion of mining scale in Weibei Coal Field in China,stope floor is increasingly threatened by the high confined water in the underlying Ordovician limestone,which leads to an obvious increase in the frequency of water inrush in the floor.In order to study the failure characteristics of stope floor,a mechanical model of stope floor strike is established based on the mine pressure theory.MathCAD software is used to generate the contour maps of vertical stress,horizontal stress and shear stress coefficient of floor rock mass along the working face during periodic pressure.According to Mohr-Coulomb yield criterion,the fail-ure characteristics of stope floor are determined.The results show that:when periodic pressure is applied,the maximum failure depth of stope floor along the working face is about 15 m,which occurs at the front of coal wall and forms a failure pattern of"deeper in front and shallower in back",approximately"scoop shape".FLAC3D simulation results show that the maximum failure depth of stope floor gradually tends to be stable with the increase of the advancing distance of working face.When the stope stope is ad-vanced to 140 m,the maximum failure depth of stope floor is stable at 15.5 m,which is very close to the failure characteristics of stope floor in confined water obtained by theoretical analysis.The current evaluation method of water inrush coefficient in Rules for Coal Mine Water Prevention and Control has certain limitations.It does not consider the influence of floor disturbance and failure depth on the thickness of water barrier layer,a formula for calculating the thickness of Ordovician limestone aquifer roof grouting re-construction is put forward.For the complex geological and hydrogeological conditions of Chengcheng No.2 Mine,a double-layer regional control network borehole structure with plane intersection and vertical offset is adopted-featuring a lower"thickness-pre-serving control layer"and an upper"inspection and reinforcement layer",so as to seal the karst fissures at the top of the Ordovi-cian limestone aquifer,and transform the top of the Ordovician limestone aquifer into a weak aquifer or water barrier layer,so as to explore and block the water channel and increase the thickness of the water barrier.