Experimental Studies On Catastrophe Information Identification Of Structural Activation And Water Inrush Mechanism In Mining Floor

Mine water inrush disaster has been a threat to the safety production of coal mines in China,and water inrush caused by activation of floor structure is the main form of mine water accidents.Many scholars were concentrated on water inrush mechanism from coal floor and paid more attention to activation characteristics of different structures,however,destruction of surrounding rock and formation characteristics of water inrush channel show similarity caused by the activation of different floor structures.Based on this viewpoint,theoretical analysis,laboratory rock test,numerical simulation and physical simulation were adopted in this paper,a series of theoretical analysis and basic experimental research have been carried out,such as activation of floor structure,failure precursor information identification,fracture expansion of surrounding rock and monitoring technology.According to the regional characteristics of fracture expansion and evolution,the seepage coupling equation of rock mass in different floor regions was derived.Combined with actual mine data,this study found that the permeability of rock mass in floor swelling area is much higher than that in other areas under the same stress condition;the water inrush model of floor structures was divided into three types:crack propagation defects model,concealed structure sliding shear model and structure conduction model,and three criterion of water inrush models were derived based on mechanics theory.The mechanism of water inrush can be summarized as structural activation destroys the integrity of floor rock and water inrush by fracture coalescence under the influence of water-rock-stress interaction.In order to study the instability characteristics of the defective rock mass,the interaction between strength segments and weak segments in defective rock mass during failure was explored from the multiple point of view.The uniaxial compression damage experiment of red prefabricated defects sandstone with different defect sizes,combined rock mass with strong and weak elements were carried out.The synergistic effect characteristics of strain accumulation and release in rock mass was analysed under the transformation process from independent activities to holistic synergy movement,the released physical information from strong linear phase stage and sub instability stage was used as an effective identification information for predicting water inrush.Combining three water inrush models and defect rocks test results,the test of large size rock-like materials with defect under biaxial loading was designed.The changes in the corresponding physical field of fracture evolution of structure and surrounding rock were captured and compared at critical moments in the process of structure activation of defective rock under simulated stress condition.By analysing the testing data,it was discovered that there are obvious stage characteristics of crack-stress-time and damage variable-energy-time in the failure process of different rock-like materials.The results indicated that in the stage of structure activation the surrounding rock produces new macro-cracks and connected with the original cracks,the number of acoustic emission events is dense and the energy is large,the rock damage variable has reached the critical value,this caused the defect rocks failure.The fracture propagation process in defective rock under solid-flow coupling was studied by using FRACOD2D,and three coupling models of fracture propagation were established.The simulation results showed that along the crack direction the pressure distribution is nonlinear during the flow process in a crack;the shorter the path,the greater the flow when fluid flow in a crack network;the original joint of rock mass provides conditions for the expansion of water crack,and the crack nearest to the inlet and outlet becomes the main channel of water inrush.Based on this idea,the "3.1" water inrush accident model of Luotuoshan coal mine is established,the results indicate that the fracturing zone that led to a water inrush occurs in front of the roadway excavation face where new fractures coalesced with the main fractured zone in the karst collapse column.In order to verify the correctness of theoretical analysis and experimental results,the physical simulation tests of water inrush from floor structure was carried out by using floor water invasion of mining influence simulation testing system and non-hydrophilic similar materials,the formation of fracture propagation and water channel,stress and pore water pressure of surrounding rock under three water inrush models were studied.Based on laboratory rock mechanics test,numerical simulation and physical test results,the abnormal physical information before defect activation was identified,the feasibility analysis of structural instability monitoring was put forward,which provides a new idea and theoretical support for the prediction and prevention of floor water inrush from coal mining floor.