| In order to explore the mechanical characteristics of the artificial dam body of underground reservoir of coal mine and analyze its deformation and failure characteristics,this paper takes the No.2 underground reservoir of Wulanmulun mine of ordos as the engineering background,and analyzes and studies it by means of theoretical analysis,physical model test and numerical simulation.Firstly,the theoretical model of artificial dam body is established by using the plastic strand method of simplified bi-directional plate,and the theoretical calculation and mechanical analysis are carried out by this model;then,to further study the deformation and failure mechanism of the artificial dam,a servo water injection system was designed and added on the basis of the original nested double dynamic pressure similar simulation test system,and the similar model test was carried out by using this system,and a series of related laws of the artificial dam were obtained;next,FLAC3D software was used for numerical simulation analysis,and a comparative study was conducted from the perspective of displacement,stress and plastic zone distribution of the dam and its cut,revealing the stability rules of the dam caused by some parameter changes,and further obtaining the optimal parameters related of the artificial dam;finally,the safety and stability of the artificial dam are evaluated by using the multi-level fuzzy comprehensive evaluation method,and its comprehensive evaluation model and evaluation system are established.The specific results are as follows:(1)Theoretical analysis research on artificial dam body of underground reservoir in coal mineThe theoretical analysis model is established based on the elastic-plastic two-way slab theory of reinforced concrete.By using the mechanical model and combined with the elastoplastic hinge line method in the design of concrete structure,the function expression of the maximum limit water pressure under uneven distribution of water pressure on the artificial dam body is established.The stability of the artificial dam is evaluated by using the function expression,and the ultimate water head of the artificial dam is obtained.(2)Physical similarity simulation model test study on artificial dam body of underground reservoir in coal mineFirstly,the stress distribution characteristic analysis,displacement analysis and acoustic wave test analysis are carried out for each component of underground reservoir(artificial dam,coal pillar dam,roadway roof and floor and reservoir roof and floor),and strain analysis is carried out for the artificial dam.Then the seepage and failure characteristics of the similar model of underground reservoir under the action of load and water pressure are briefly analyzed.Finally,a series of the deformation and failure characteristics and rules of artificial dam in underground reservoir of coal mine are summarized,and the deformation and failure mechanism of artificial dam is revealed.It is found that under the action of multi-load coupling,the stress concentration in the cut area of the top and bottom face of the artificial dam body is greater,and the damage near the cut is more likely to occur.The existence of water pressure changes the stress state of surrounding rock in a certain range around the reservoir,enhances the radial stress in a certain range of roof and floor to a certain extent,and weakens the vertical stress in a certain range of the coal pillar dam.Under the action of water pressure,the infiltration of underground reservoirs basically presents a certain regularity.The places where the infiltration phenomenon occurs are in sequence:the bottom cut of the artificial dam body,the top cut of the artificial dam body,the coal pillar dam body,the floor of the reservoir,the roof of the reservoir,the roof of the roadway,the floor of the roadway,and the surface of the artificial dam body.In addition,the failure of the artificial dam body is compression shear failure,and the cracks extend from the lower part of the surface of the back of the artificial dam body model to the top of the face of the water,running through the whole artificial dam body and forming an Angle of about 450 with the section of the artificial dam body.(3)Numerical simulation research on artificial dam body of underground reservoir in coal mineThe fluid-structure coupling model of underground reservoir in coal mine was established by FLAC3D software.Firstly,the mechanical response of the artificial dam body was analyzed by changing the water storage pressure,and the ultimate head of 21m was obtained.Then,by changing the parameters of the artificial dam,several groups of numerical simulation were carried out,and finally the stability rules and optimal parameters of the artificial dam were obtained.With the increase of cut depth,the displacement and tensile stress of the artificial dam and the cut along the direction of water pressure decrease gradually,and the decreasing trend gradually becomes slow,and finally tends to be unchanged.And the displacement and tensile stress reduction caused by increasing the depth of the band cut is significantly greater than that caused by increasing the depth of the top and the bottom cut.Obviously,the effect of increasing the depth of top groove is better.In addition,increasing the thickness and strength of the artificial dam has certain effect on reducing the displacement and stress level of the dam and the cut,and the law is similar to that of increasing the cut depth,and increasing the thickness and strength of the artificial dam can also effectively reduce the area of the plastic zone,so as to enhance the stability of the reservoir.Under comprehensive consideration,the optimal parameters of the artificial dam body are as follows:the depth of the side cut of the artificial dam body is 0.6m,the depth of the top cut is 0.5m,the depth of the bottom cut is 0.4m,the thickness of the artificial dam body is 1.4m,and the strength grade of concrete used by the artificial dam body is C25.(4)Comprehensive evaluation research on the stability of artificial dam body of underground reservoir in coal mineThe stability of the artificial dam body of underground reservoir in coal mine is affected by many factors,and it is difficult to determine the degree of influence of each factor on the stability of the dam body.The safety of the artificial dam is the precondition of the normal operation of the underground reservoir and the safety evaluation of dam body includes various indexes,criteria and levels.In order to objectively and accurately evaluate the safety of the dam body,field research was carried out on the underground reservoir built in the mine.Communicate with the underground reservoir experts of the coal mine unit,and invite the experts on the construction of the reservoir to grade the factors affecting the safety and stability of the dam body.The analytic hierarchy process is used to calculate the weight of factors at different levels,and the comparative judgment matrix is established to meet the consistency test.Based on fuzzy theory and expert questionnaire,the membership degree of evaluation factors was determined and the evaluation matrix was obtained.The comprehensive safety evaluation of the artificial dam body is carried out,and the comprehensive evaluation level of the factors that affect the dam body greatly and the stability of the dam body is determined,which provides a reference for the safety evaluation and monitoring and management of the artificial dam body of the underground reservoir.Finally,the multi-level fuzzy comprehensive evaluation model of the safety of the artificial dam body of underground reservoir is applied to the comprehensive evaluation of the safety of the artificial dam body of No.2 underground reservoir of wulanmulun coal mine in shendong mining area.According to the principle of maximum membership degree,the results show that the dam body is in a safe state. |
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