Study On Loess Damage And Its Environmental Effect Under Mining Action

With the development of economy and society,the distribution of coal production and consumption in China is in a dilemma.The resources in the Middle East are exhausted,and the coal industry is transferring to the arid and semiarid areas in the West.In the arid and semiarid areas of Northwest China,there are a large number of deep loess covered areas.The ground fissures and water level drop caused by coal mining in these areas become the stumbling block to the sustainable development of local ecology.It is generally considered that mining subsidence is an important factor that causes the ground fissures in the mining area of coal mine.The fissure development connects the topsoil from the roof,and the surface run off and phreatic water flow along the fissures,leading to the water level drop.However,after many years of experience in water prevention and control in coal mine,the height of the water diversion fissure zone is not very deep,and the water level of the coal mine will be stable after a certain period of time.In order to protect the environment of the ecologically fragile area,this paper takes the 5-108 first mining face of a mine in Lüliang as the research object,investigates the occurrence and development scale of the ground fissures in the study area through the field survey.It uses D-InSAR remote sensing technology to monitor the subsidence of the working face and its surrounding topsoil layer,and preliminarily judges the formation mechanism of the ground fissures by combining the numerical simulation method.According to the established geotechnical model,the change of groundwater level influenced by mining is studied.The main conclusions are as follows:(1)Through field investigation and field survey,the types of surface loess damage in the study area under the action of coal mining are identified,mainly including ground fissures,collapse pits,landslides and other disaster forms.Generally,the collapse pit is associated with the ground fissure,and it is mainly distributed at the boundary of the mining area and the edge of some gullies.(2)Through numerical simulation,the phenomenon of stress concentration in the corner shear stress of working face after the disturbance of coal mining is analyzed,and the local overburden soil body is destroyed due to exceeding the shear strength.After mining disturbance,the maximum local tensile stress of the overlying strata is about 1.3Mpa,the maximum compressive stress is 23.6Mpa,and the possibility of tension and compression failure of the overlying strata is small;the shear stress at the corner of the working face appears stress concentration,the maximum value is about 19.5Mpa,which exceeds the shear strength of the overlying strata.(3)Using GMS calculation method,the influence and change characteristics of the coal mining project on the groundwater level are simulated.It is found that under the action of coal mining,a depression funnel is formed with the working face as the center,and the groundwater level tends to be fast first and then slow as the mining activities advance.This paper has 35 figures,8 tables and 96 references.