Development and verification of simulation testing system for floor seepage in coal mine underground reservoir

Based on the requirements of the green development for the western coal mining area in China,the coordinated development of coal resources development,ecological environment and water resources protection in western mining areas is becoming more and more important.Coal mine underground reservoir technology inno-vatively enhances the green development of western coalfield,however,there are still many scientific challenges to overcome.In order to study the seepage law,the deformation and failure characteristics of underground reservoir floor under the stress-seepage coupling condition,and to analyze the multi-field information in the seepage channel evolution process,a seepage simulation test system of underground reservoir floor was developed independently.The test system mainly consists of a servo stabilized voltage control system,a test chamber system and a computer monitoring and data acquisition system.Among them,the servo stabilized voltage control system can use gas pressure instead of water pressure to simulate the pressure generated by the waterbody of underground reservoir and the pressure generated by overlying strata.It realizes the digital control of overall pressure,and the range of that is 0-0.8 MPa.Test chamber system can realize the simulation test of fluid-solid coupling at different water levels,which is a steel frame structure.The maximum model size is 1 000 mm×600 mm×500 mm (length × width × height).Taking the geological condition of Shendong mining area as the background,the similarity simulation test of floor seepage was carried out.The variation laws of pore water pressure and water leakage were obtained.Also the rationality and practicability of the equipment were verified.The results showed that the pore water pressure and water leakage could characterize the rock seepage macroscopically.Pore water pressure generally needed to go through the initial maintenance stage,the increase stage,the maximum stable stage,the decrease stage and the stable stage.The maximum increase was about 0.8 kPa,and the difference of pore water pressure between the initial value and the stable value was about 0.1 kPa.The trend of pore water pressure variation curve of measuring points at different positions in the same layer and at the same position in different layers was basically similar.The main factors that influenced the pore water pressure include the measuring point,rock lithology,permeability and the heterogeneity of the laying model.The water leakage was influenced by the size of the flow section and permeability coefficient,and the maximum water leakage ranged from 14 to 15 mL/s.