Study On The Mechanism Of Fault Lagging Water Inrush In Large Mining Depth And High Water Pressure Mine

The North China Coalfield is mainly affected by the outburst of Ordovician limestone water from the coal floor,and the lagging water inrush accident caused by the fault severely restricts coal mine safety production in large mining depth and high water pressure especially.In order to better solve the key problem of lagging water inrush in North China Coalfield,this paper aims to study the mechanism of fault lagging water inrush in large mining depth and high water pressure mine and its engineering application based theoretical analysis,numerical simulation and other methods.And,during study takes the background of water inrush accident at no.2228 mining face of Xingdong Coal Mine,Hebei Province as the study background with mining depth is greater than 1000m and the coal floor is subjected to Ordovician limestone water pressure greater than 11MPa.The conclusions are as follows:(1)Based on the geological and hydrogeological conditions of Xingdong Coal Mine,the nature of the faults involved in the development and recovery of no.2228mining face was studied.The reasons for the water inrush from the floor of no.2228mining face of Xingdong Coal Mine were analyzed according to the fault occurrence and mining conditions.Fault lagging water inrush is caused by the activation of non-water-conducting faults,and the lagging water inrush from the bottom faults is determined as the research object.(2)A hydraulic model for lagging fault rupture of the floor was established in large mining depth and high water pressure.With the help of the stress intensity factor theory in fracture mechanics,the ultimate water pressure formula for fault activation is derived.Using the remaining life estimation of fatigue crack growth to study the lagging water inrush time of the floor fault,the expression of the number of cycles required for the fault crack to extend to the mining face is derived.According to the actual water inrush in no.2228 mining face,the expression of the number of cycles was verified.Using MATLAB software to numerically analyze the influencing factors of the fault activation limit water pressure formula,the relationship between the limit water pressure and the maximum principal stress,fault dip angle and fault drop is obtained.(3)Based on FLAC~3DD numerical simulation software,and using the fluid-solid coupling model theory,the characteristics of fault activation,damage to the floor and fault crack propagation seepage were simulated during mining.And the effects of aquifer water pressure,fault dip angle,fault drop and excavation step on the fault lagging water inrush of mine floor were affected,inordinately.Numerical simulation results show that:Under high aquifer pressure conditions,the time for water in the aquifer to enter the ore failure zone is shortened,the width of the water inrush channel is increased,and the amount of water inrush is increased.As the fault dip angle increases,the fault is easily to connect with the rock pressure damaged zone.Water uses the activated fault as water inrush channel to flow faster to the rock pressure damaged zone.Under different fault drops,the fault activation time is different.The larger the fault drop,the earlier the fault activation start time.The activated fault channel is different from the activated fault channel.The rock pressure damaged zone connects faster and the floor water inrush lag time is shortened.When the excavation step is larger,the damage to the floor of the coal face is greater,and the fault activation is faster.(4)The mechanism of fault lagging water inrush in large mining depth and high water pressure mine was applied to the exploration and treatment project of floor faults in no.2229 mining face of Xingdong Mine.A phased treatment plan was developed for pre-grouting non-water conducting faults before mining and supplementing grouting for activated faults within a limited time after mining.The implementation of the two-stage grouting project cuts off the recharge channel of Ordovician limestone water.The results of the water conductivity test of the fault after grouting reconstruction show that the stress concentration in and near non-water-conducting faults is reduced,the integrity and water-blocking capacity of the water-insulating later of the 2~#coal seam floor are improved,and the Ordovician limestone water is effectively blocked from entering the mining face.It ensures the safe mining of the mine under the conditions of large mining depth and high water pressure,and brings greater economic and social benefits to Xingdong Coal Mine.