Study On Stability Of Coal Pillar Dam Body Of Groundwater Reservoir Under Stress-seepage Coupling

Under the combined action of the working face mining disturbance and water storage pressure,it is prone to cause the instability and damage of the coal pillar dam body of the groundwater reservoir.Combined with indoor experiments,numerical simulations and theoretical research,this thesis studies the mechanical deformation characteristics and seepage evolution characteristics of coal pillar dam under stressseepage coupling,obtains the stress,seepage and damage evolution law of surrounding rock of coal pillar dam under the influence of mining,and establishes a stability evaluation model of coal pillar dam body of the groundwater reservoir under the influence of multiple factors.The main results are as follows:(1)The stress-seepage coupling test method of coal pillar dam body in groundwater reservoir is proposed,similar coal pillar dam body samples are prepared.Then a stress-seepage coupling test system is constructed,and a stress-seepage coupling characteristic parameter expression method is proposed.(2)The stress-seepage coupling test of coal pillar dam body under different conditions was carried out,and the asymmetric deformation characteristics of coal pillar specimen under the coupling of stress-seepage were obtained.And it was found that the changes of porosity,flow rate and permeability of the sample could be divided into three stages: slow reduction stage,rapid growth stage and stability stage.And analyse the mechanical deformation characteristics and seepage characteristics of coal pillar dam body under different confining pressure and water pressure conditions,which provided a reliable basis for numerical simulation parameter selection.(3)A large-scale numerical model of the coal pillar dam body of groundwater reservoir under the combined action of excavation and water storage pressure of the working face was established,and the numerical simulation of stress-seepage coupling was carried out.Then the stress,seepage and damage evolution of coal pillar dam body under the influence of mining were explored,and the results show that the damage of coal pillar dam body on the side of reservoir is more serious than gob side,which is consistent with the results of stress-seepage coupling test.(4)Combined with the actual working conditions of groundwater reservoir and the results of on-site investigation,3 factors and 13 evaluation indicators affecting the stability of coal pillar dam body were obtained.The weight and membership degree of each evaluation index were determined by analytic hierarchy method and fuzzy mathematical theory.A comprehensive evaluation model of coal pillar dam stability was constructed,and the stability evaluation of the studied groundwater reservoir coal pillar dam body was carried out,and the evaluation results showed that the stability of the groundwater reservoir was good,which provided a theoretical basis for the safe and efficient operation of groundwater reservoir.The thesis has 43 figures,19 tables and 103 references...