Study On The Mechanism Of Water Inrush By Fault Activation Under Seepage Stress Coupling

Fault water inrush in coal mines has long puzzled coal mine safety production.There are many factors affecting the activated water inrush process of the floor fault.In order to solve the problem of activated water inrush from the floor fault,the geological structure,the original rock stress,the water pressure of the aquifer and the mining mode should be taken into consideration,and the systematic study on the activated water inrush from the floor fault is carried out.In this paper,the mechanical analysis,numerical solution,FLAC numerical simulation and engineering practice are combined to study the fault activation and the mechanism of the water inrush in the bottom of the stope.The main research results are as follows:1.On the basis of the distribution law of the supporting pressure of the surrounding rock in the stope,the effective shear stress distribution of the surrounding rock in the fault zone is calculated by using the semi infinite body theory of elasticity,and the coupled mechanical model of the active seepage stress of the fault above the confined water is established.The stress distribution of the surrounding rock in the fault zone at any position of the stope floor under the influence of the water pressure is further deduced.It is found that the working face advances to the distance from the fault The shear stress on the fault plane has reached the peak value at a certain distance,which is an important reason for water inrush in advance,and the acute angle fault is easier to activate than the obtuse angle fault.2.According to the theoretical research of fault activation factors of confined water using FLAC3D numerical simulation software to establish three-dimensional fluid-structure coupling numerical model,and simulated with fault(normal fault)coal floor fault activation features,analysis of different fault throw and fault dip Angle and the different face advance distance and the influence of stress concentration degree of faults in floor water bursting,explains the change law of shear stress on the fault planes research shows that fault activation largest maximum damage depth of the base depth is about 2 times;In the mining of coal seam with normal fault,the stress variation range of footall mining fault surface is small,the risk coefficient of water inrush is low,and the mining is safer.Therefore,more attention should be paid to the monitoring of confined water when the working face of upper mining in engineering application advances to the front of fault.3.From microscopic perspective,based on the theory of fracture mechanics,the fault fractured rock mass under the action of compression-shear,shear fracture strength analysis,through the,control variable method for deriving the crack extension function assignment analysis,further regularity of fault zone rock mass cranny,and combined with RFPA-Flow simulation software,the fault fissure extension,the evolution of the development process of simulation,the study found that with the increase of confining pressure,the lower part of crack tip is easy to initiation of the wing crack ",and "the wing crack" expanded rapidly,lead to the unstability of the model is the main crack;With the increase of pore pressure,the "anti-wing crack" at the lower tip of the fracture will develop gradually from axial stress to horizontal confining pressure.4.Taking the actual geological conditions of 1316 working face of Anju coal mine as the engineering background,the simulation research on the process of floor fault activation and confined water diversion in the process of working face advancing is carried out.It is found that during the whole mining process,the maximum diversion height of floor confined water is about 50m from the floor,and the maximum activation depth of fault is 42m from the floor of coal seam through theoretical analysis and numerical simulation,Therefore,the confined water fails to connect with the activated fault fracture,and then the confined water cannot enter the floor water conduction fracture zone along the fault.Therefore,the mining of working face 1316 is not affected by fk65 fault,the working face is relatively safe,and the risk of water inrush is small.