Study On Geological Characteristics And Surface Subsidence Law Of Mining Under Super-thick Loose Strata

In the process of coal mining,the accurate prediction of surface deformation and destruction can improve the utilization rate of high quality coal resources under the premise of ensuring safe production.Therefore,it is of great significance to study the prediction of surface subsidence.For a long time,experts and scholars at home and abroad have carried out detailed research on the law of surface movement in terms of different mining conditions and geological conditions,and have made many achievements.However,the research on the surface movement and deformation caused by the mining under the super-thick loose strata is relatively few,especially in the geological condition of the transition body of "hard soil-soft rock" in the bottom of the loose layer.Therefore,in order to study the coal mining,engineering geological characteristics and surface subsidence law under the condition of super-thick loose strata,the following research works have been carried out.(1)Fully understand the research status at home and abroad,and describe the characteristics of surface subsidence in coal mining.The basic characteristics of mining subsidence under super-thick loose strata are discussed,and the mechanical analysis of mining subsidence process is carried out,this lays the foundation for further research on the rule of surface subsidence under the condition of super-thick loose strata.(2)Through the ground drilling core and indoor geotechnical tests,the parameters are statistically sorted out:There are typical "hard soil-sofr rock" strata at the bottom of Neogene in coal seam is covered with super-thick loose strata,it belongs to a special transitional stratum from hard soil to soft rock.According to the results of geotextile test,the hydraulic and mechanical characteristics and shallow buried loose layers are compared and analyzed.It has the characteristics of low water content,high degree of consolidation and strong strength,which shows that the transition body is different from shallow buried loose strata and has a very important influence on the surface subsidence.(3)Using FLAC3D numerical simulation software,choose the thickness of hard soil soft rock transition body,the thickness of loose strata,and the thickness of bedrock as the influencing factors,and establish 27 models of working conditions,the surface subsidence characteristics of different strata combination are numerically simulated.Finally come to a conclusion:both the transition body and bedrock inhibit the surface subsidence and the compression of loose strata,and this inhibition will increase with the increase of its thickness.With the increase of the thickness of the loose strata,the maximum subsidence and compression amount of the surface increase first and then decrease.(4)Based on the results obtained by numerical simulation,a model is established to train and learn sample data,three factors are sorted sensitivities by using neural network.The sensitivity of the surface subsidence is sorted:bedrock>"hard soil-soft rock" transition body>loose strata,at the same time,the particularity of transitional half soil and half rock is confirmed.(5)Comparison and verification with measured data of 1304N working face in Xinjulong coal mine and previous research results,the location of the subsidence 10mm measured by the observation station is basically consistent with that calculated by the simulation results,and confirm the reliability of the previous study.It is of great significance to predict surface subsidence under super-thick loose strata in the future.