Experimental Study On Multi-physical Field Characterization Of Water Inrush Induced By Mining-induced Floor Fracture Expansion In Coal Seam

With the gradual transfer of the national coal resources development strategy to the west,the scale and intensity of coal mining in the west have increased year by year.However,the complex mine hydrogeological conditions have seriously restricted the safe and efficient mining of coal resources.Jungar coalfield in the Ordos basin belongs to North China type hydrogeological structure type,which is characterized by large coal seam thickness,complex geological structure,and serious floor Ordovician limestone water damage.This paper is guided by the interdisciplinary theories of hydrogeology,rock mechanics,geophysics,tectonic geology,mining engineering,etc.Theoretical analysis,numerical simulation,physical test,on-site monitoring and other methods are adopted.The author has carried out a systematic and in-depth study on the structural characteristics of the floor aquiclude of Tangjiahui Coal Mine in Jungar Coalfield,the catastrophic mode and mechanism of water inrush from the floor of typical aquifer,the response characteristics of multi-physical fields and the identification of impending disaster signals.It is expected to provide guidance for the monitoring and early warning of water inrush from the floor under similar geological conditions.The main achievements and understanding are as follows:(1)Division of floor rock structure and analysis of water blocking capacity of typical water inrush disaster model.Based on the statistical analysis of the typical drilling lithology data of the floor of multiple working faces in the mine,the floor rock structure is divided into layers by using the "three layers" method.Based on the actual geological structural conditions of the floor of the mine working face and its induced water inrush mechanism,a generalized model of water inrush in the floor "three layers" structure with a typical water-conducting structure is given.The relationship between the properties of each interval,the key layers,and the structure is determined,and the water-blocking ability and water inrush risk of each model are qualitatively evaluated.The concept of "floor water inrush disaster chain" is proposed,which is based on the concept of "coupling" and "process" to understand the space-time evolution mechanism of floor water inrush disaster,and gives the evolution path of typical mining floor damage water inrush disaster chain.(2)Based on the fluid-structure coupling numerical simulation of FLAC 3D,the research on the formation and evolution mechanism of the joint damage and water inrush channel in the upper and lower areas of the floor.The failure characteristics of the floor of the concealed water-conducting structure under different water pressures and the distribution law of the confined water diffusion are systematically simulated.The idea and method of spatial superposition analysis of the simulation results of stress field-seepage field and fracture field-seepage field are proposed.By using the method of sketch drawing to express the complex plastic failure and the space-time evolution simulation results of pore water pressure,the correlation model between mining floor damage and tectonic activation water inrush is analyzed.The mechanism of joint damage and water inrush disaster evolution in the upper and lower areas of the mining floor under different water pressures is revealed.(3)Study on the development and characteristics of fluid-structure coupling similar materials for the floor rock with water-conducting structure.Using quartz sand,calcium carbonate and talc powder as aggregates,white cement and vaseline as cement and hydraulic oil as modifiers,the proportions of different similar materials were determined by the orthogonal test method,and the physical-mechanical-hydraulic properties were tested and analyzed.The proportioned materials which can meet the requirements of different rock structures such as water-barrier layer,limestone layer and water-conducting structure are formulated.The range analysis method was used to statistically analyze the sensitivity of each parameter property,and the quantitative relationship between the key parameters of the sample and the material composition ratio was determined by multiple linear regression analysis of the results of each parameter of the sample.(4)Experimental study on multi-parameter collaborative monitoring and characterization of the activation of floor structure and the formation of water inrush channels in coal seam mining under pressure.The two-dimensional floor water inrush simulation test bench system was optimized and improved independently.The "point-line-plane" multi-field and multi-parameter collaborative monitoring technology,which is mainly based on geoelectric field monitoring and supplemented by strain field monitoring,are integrated.A multi-source information monitoring test model for potential water inrush from the mining floor of coal seam above confined water is established.The collaborative monitoring of water pressure flow and multi-physical information is realized in the process of mining floor water inrush evolution under the original in-situ stress environment simulated by a large two-dimensional model size.The multi-parameter response characteristics and change rules of the structural evolution process of the "lower three zones" and "transverse six zones" of the floor are revealed.Based on the multi-parameter visualization results,the formation and evolution mechanism of the fault water inrush channel following the combination of the minimum path principle and the dominant path principle is explained.A multi-parameter response identification and characterization method of water inrush precursor information is proposed.(5)Based on the multi-physics field monitoring technology,the hidden danger of water inrush from the floor of the stope and its risk analysis are studied.The multi-parameter collaborative monitoring technology is used to realize the continuous monitoring of the entire life cycle of the floor of multiple stopes in Tangjiahui Coal Mine.The development depth of floor failure zone and disturbance influence zone in each monitoring area is obtained.Through further comprehensive analysis of the floor test data of each working face in the mining area,the spatial distribution characteristics and laws of the floor damage and water inrush risk in the mining area are obtained from the face.The research results have a certain guiding role for the prevention and control of floor water damage and safe mining in other areas of the mine.The proposed "point-line-plane" multi-field and multi-parameter collaborative monitoring technology has broad engineering application prospects in the intelligent prevention and control of floor water inrush.Figure [115] Table [23] Reference [179]...