| In the production activities of mining areas,mining ground fissures is a common geological disaster,which seriously threatens the safety of people’s lives and properties.In coal production base in Shanxi Province and part of the mining area is distributed in the loess hilly north thicker,surface fluctuation,cracks are more likely to form under the condition of mining,the mining area of vegetation,farmland,roads and buildings destroyed,under the demand of national disaster prevention and mitigation,study and master the loess hilly region dynamic evolution law of mining ground fissures,It can provide some reference value for prevention and control and ecological restoration,and further optimize the ecological environment of mining area.In view of the mining fracture disaster in loess hilly-gully region,taking Zhengwang Coal mine in Fenxi mining area of Shanxi Province as the research background,based on the measured data,combined with UAV remote sensing technology,field investigation,numerical simulation,theoretical analysis and other methods,the evolution law of mining fracture in this region is deeply studied.This paper mainly discusses the law of overburden breaking,the law of fracture dynamic evolution and formation mechanism,and the law of mining subsidence under the loess hilly landform.The main work and achievements are as follows(1)To typical loess hilly-gully region Fenxi mining area as the research background,through the establishment of surface movement observation station,the research on the rules of mining subsidence loess hilly-gully region,the results show that the subsidence deformation of loess hills are greatly influenced by topography and geomorphology,mining slope easily happened in the process of slippage phenomenon,surface subsidence coefficient is larger,and the surface horizontal displacement curve point mutation is more,The measured data show that discontinuous movement and deformation are obvious in loess hilly region.(2)The ground fissures in 103 working face of Zhengwang coal mine are investigated by using UAV remote sensing technology.It is concluded that the ground fissures in this area mainly include tensile type and bench type.There are a large number of bench type cracks distributed at the boundary of the working face,and the crack length and bench drop are large;The reliability of UAV Remote Sensing Technology in identifying and interpreting mining fractures is verified by field investigation.It is found that the identification accuracy of UAV in fracture investigation is higher in this area,and the fracture morphology and distribution characteristics can be investigated more efficiently and comprehensively(3)After comparing and analyzing the advantages and disadvantages of different numerical simulation methods and programs and the evolution law of mining surface cracks,using the discrete element numerical simulation software 3DEC,this paper selects the 103 working face of Zhengwang coal mine as the research object,establishes a three-dimensional geological body model based on the real surface fluctuation above the working face,and studies the overburden fracture,ground crack development law and surface movement and deformation law in the process of advancing the working face.The results show that:(1)according to the advancing scale of the working face,the failure of overburden can be divided into two processes: the initial failure and collapse of the basic roof and the periodic pressure of the basic roof.(2)With the mining of coal seams,the surface cracks are mainly affected by the breaking of the underlying rock layers,and internal cracks in the loess layer,tensile cracks and step-type cracks have been formed successively.(3)The numerical simulation experiment can better restore the process of surface movement and deformation,and the measured value is close to the maximum subsidence in the simulation experiment.(4)The "bench rock beam" structure is used to study the crack formation mechanism.Combined with the numerical simulation experiment,it is found that the key layer of working face 103 is thick and there is layered collapse.The development process of mining surface cracks is divided into three periods: crack formation period,growth period and stability period. |
