Study On Crack-stress Evolution Law And Surface Subsidence Of Overburden Rock In Deep Mining

Due to long-term mining,the development of coal resources in China has entered the stage of deep mining.With the continuous increase of mining intensity and mining area,the liberation of’three under’coal pressure has gradually become a difficult problem in the mining area of central and eastern China.How to carry out safe and green mining on the premise of ensuring the safety of surface appendages,effectively controlling surface subsidence and realizing sustainable development of coal mines is an important problem that China’s coal mines urgently need to solve.The geological conditions of the deep mining area are complex,and the composition and structure of the overlying strata are different.The laws of surface subsidence,overburden fracture development and stress evolution caused by’three under’mining,especially under water mining,and their mutual influence are unclear.The research on the synergy between fracture-stress-deformation is not enough.Based on the background of Jiulong Mine,this thesis analyzes the distribution and evolution characteristics of fracture-stress,establishes the quantitative relationship between fracture-stress,analyzes the fracture-stress evolution law of overburden rock in deep mining and the law of hard rock deformation and surface subsidence,and puts forward the fracture-stress-deformation multi-key stratum-hard rock location synergy model of deep overburden rock.The main results are as follows:（1）The distribution and evolution characteristics of fracture field and mining stress are analyzed,and the stress arch model is established to reveal the quantitative relationship between mining stress and fracture field,and the morphological equation of stress arch is obtained.By calculating the load and breaking distance of each rock layer,it is judged that there are 9 hard rock layers,2 sub-key layers and 1 main key layer above the coal seam.（2）The whole process of formation and development of fracture zone in deep mining is studied by using microseismic monitoring technology.The distribution characteristics and evolution law of microseismic events are obtained.Combined with the field test method of drilling fluid leakage,the development height of overburden fracture in15249S working face is 130m..（3）Through the numerical simulation software UDEC,the evolution law of fracture field and the migration law of overburden rock in deep mining are obtained.The fracture field shows a trapezoidal leap-forward growth,and the trapezoidal area affects the height of the stress arch.The parameters affecting the trapezoidal area are substituted into the two-dimensional stress arch model to obtain the two-dimensional stress arch shape equation of the overlying rock in the 15249S working face.（4）Through the numerical simulation software FLAC^3D,the stress evolution law of overburden rock in deep mining is obtained.The evolution law and shape of abutment pressure,overburden stress and plastic zone of surrounding rock are different under different advancing distances.The volume of plastic zone affects the height of stress arch.The volume of plastic zone is substituted into the three-dimensional stress arch model to obtain the three-dimensional stress arch shape equation of overburden in 15249S working face.（5）FLAC^3D numerical simulation method is used to analyze the deformation law of hard rock under the influence of mining height,elastic modulus of main key stratum,thickness of main key stratum and different mining methods,and the control law of key stratum and hard rock is obtained.At the same time,the mining height,the elastic modulus of the main key layer,the thickness of the main key layer,and the surface subsidence law under the influence of different mining methods are analyzed.The optimal mining method for slowing down the surface subsidence is obtained,and the deep mining overburden fracture-stress-deformation multi-key layer-hard rock location synergy model is established.