Research On The Deformation And Failure Law And Maintenance Technology For Dam Body While Mining The First Working Face Under Dam In Daping Mine

Safety synergy of mining under reservoir dam refers to not only ensuring the underwater safety of reservoir,but also ensuring the safety of dam body and operation of reservoir,so as to extract the dull coal resources under dam.Safely and reliably mining coal resources under dams will have immeasurable significance both technically and economically.The laws and characteristics of overburden deformation and damage,surface movement deformation,dam movement and deformation and damage caused by mining under the dam of Daping Mine,as well as the dam reinforcement technology,are studied in depth by means of theoretical analysis,laboratory test,numerical simulation,similar material simulation and field measurement.The orthogonal test is used to determine the test scheme group of different influence factors combination,and height of water flowing fractured zone and caving zone of each scheme is obtained through 3DEC simulation analysis;combined with the measured data of the working face,the calculation model of the height of flowing fractured zone and caving zone of the mine field is constructed by using statistical analysis method.The error analysis shows that the average relative errors of the calculation results of the height of flowing fractured zone and the caving zone are 2.93%and 4.08%respectively,which can basically meet the requirements of practical application.According to the regulations of "Regulations of pillar leaving and coal mining under building,water,railway and main shaft and tunnel" and the rock property of overburden,the judgment standard of safety of coal mining under reservoir water is put forward.According to the calculation model and numerical simulation,the maximum possible height of flowing fractured zone is obtained,and according to the above criteria,the result is safe and feasible when the first mining face under the dam is mined underwater.In view of the problem that the maximum subsidence value of the surface of waiting mining face is difficult to be determined,the viewpoint that the height of the remaining free-space of the overburden is equal to the maximum subsidence value of the surface is put forward.According to the measured data of surface movement and deformation in Daping Mine,the error of prediction model is corrected by statistical analysis.By using the revised calculation model and the calculated maximum subsidence value of the surface and other parameters to analyse the law and characteristics of the movement deformation and deformation failure of the dam body,the following conclusions are drawn:each movement deformation value of the dam presents an asymmetrical distribution,and it is inferred that the dam's deformation failure is the most serious at 30m and 270m from the left slop of the working face.According to the variation of the surface movement and deformation with the advance of the working face,a simplified(local amplification)simulation method is established to replacement coal seams mining with the shallow excavation.Through full-scale numerical simulation,simplified similar material simulation and simplified numerical simulation analysis,the deformation and failure laws and characteristics of the dam body with the advance of the working face are revealed:The dam body has experienced the alternating change process from tensile deformation failure to compression reduction,but the time nodes of tensile-compression transition process are different in each part;the starting point of the dam body affected by mining is the working face advancing 600m,the ending point is the working face advancing 1800m,and the unilateral length of the dam body affected by the working face mining is 280m.According to the laws and characteristics of dam movement,deformation and failure,a dam maintenance scheme is designed,which consists four parts.These four parts are respectively:monitoring scheme of reservoir water level to ensure stable water level,the reinforcement scheme is composed of stage heightening,seepage control scheme of laying geomembrane and construction quality monitoring scheme based on observation of dam movement and deformation.The results of construction quality monitoring in the mining process of working face show that the water level is always under+81.26m,the height of the working dam is always 2.44m higher than the water level,there is no leakage and sudden local collapse in the dam body,and the first mining face is successfully,safely and smoothly mined.It is proved that the design of maintenance scheme is reasonable.At the same time,the reliability of basic research results before mining and feasibility of research method are also proved which are in good agreement with the objective reality.There are 101 figures,37 tables and 162 references in this doctoral dissertation.