Experimental Study And Numerical Simulation Of Water Weakening By Leaching Of Peat-bearing Coal Columns

Water inrush has always been one of the main problems in coal mining.In the past ten years,water inrush caused by coal pillar destruction accounted for about 50%of the major water disasters in China.The process of water inrush disaster induced by coal pillar instability is the result of coupling of stress field,damage field,seepage field and diffusion field.And the peat bearing coal pillar is obviously affected by the weakening of water immersion,which leads to the reduction of the effective size of the water resisting coal pillar and poses a serious threat to the safety of underground mine construction.Therefore,it is of great practical significance and engineering value to carry out the research on the water weakening process of peat bearing coal pillar for the prevention and control of coal pillar water inrush disaster.This paper focuses on the problem of water inrush caused by coal pillar failure in Zhangcun Coal Mine,Shanxi Province,and carries out the experimental and Simulation Research on the water diffusion weakening of peat coal pillar.Based on the indoor test,the diffusion process and law of water in coal and rock mass under one-dimensional water immersion condition are analyzed,and the weakening degree of mechanical properties of coal pillar under different water content conditions is measured,and the failure law is discussed.Finally,combined with the test results,the stress Seepage Damage diffusion multi field coupling model is established,and the reserved size of water separation coal pillar is preliminarily revised.The main research contents are as follows(1)Research and development of immersion diffusion experiment device and immersion diffusion experiment.Aiming at the problem of coal pillar soaking diffusion,we independently developed the soaking weakening experimental device.It can measure the real-time quality and resistance of coal pillar in the process of water immersion.According to the measurement results,the diffusion mode and diffusion process of water in coal pillar can be inversed,and the diffusion law of moisture in coal pillar can be studied.And the corresponding evolution equation is fitted,which provides the basis for the future experimental research.(2)Experimental study on weakening degree of mechanical properties of coal pillar soaked in water and establishment of humidity weakening equation.The mechanical properties of coal pillars with different soaking time were tested by 20t tension compression testing machine independently developed by Northeast University.The weakening degree of mechanical properties of coal pillars with different water content was measured.The quantitative relationship between weakening coefficient L and water content w of coal pillars was determined,and the failure law of coal pillars after soaking weakening was analyzed.(3)Research on the diffusion law of water in coal and rock materials and numerical simulation of water diffusion process and weakening failure of coal pillar in small scale.Based on the theory of water diffusion field,this paper analyzes the diffusion mode and process of water in coal and rock materials,determines the relationship between various physical quantities to measure water content,establishes the coupling model between diffusion field and stress field for numerical simulation calculation,and compares it with the coal pillar soaking diffusion experiment and soaking weakening experiment,The rationality and correctness of the coupling equation are verified.(4)Based on the results of immersion diffusion experiment and immersion weakening experiment,and considering the coupling relationship between multi physical field coupling theory and physical parameters in multi field,the stress Seepage Damage diffusion multi field coupling model is established.Then,the finite element software COMSOL is used to model and solve the actual engineering case,reproduce the process of coal pillar failure and water inrush,and analyze the water inrush failure mechanism under the coupling effect of multiple physical fields.(5)Based on the results of laboratory test and numerical simulation of engineering cases,considering the weakening effect of coal pillar soaking,the effective mechanical properties of coal pillar are modified,and then the reserved size of coal pillar is preliminarily revised.And other physical quantities can also be treated in this way,and then the effective value can be calculated,which not only retains the advantages and advantages of the original formla,but also corrects and improves the problem of water immersion weakening,which provides a new idea for the future coal pillar size.