Numerical simulation of overburden migration in a top-coal caving face under extremely weakly cemented strata in Eastern Inner Mongolia

Quan Xizhu; Huang Zunying; Yan Shuai

doi:10.16186/j.cnki.1673-9787.2024100029

Abstract：Objectives To investigate the overburden migration behavior and surface subsidence characteris-tics induced by top-coal caving mining in the extremely weakly cemented Cretaceous strata of Eastern Inner Mongolia,a numerical simulation study was carried out using a typical working face of the Wujianfang coal-field as the engineering background.Methods A particle flow numerical model was first established based on PFC2D 5.0,and the rationality of model parameters was verified by comparing the simulated surface subsidence with in-situ measured data.The overburden migration characteristics were then analyzed by inte-grating force chain diagrams,principal stress distributions,and displacement fields.Finally,a sensitivity analysis was conducted to evaluate the effects of burial depth,mining height,and advancing speed on over-burden migration.Results The results indicate that the overlying strata generally experience three stages:formation and rapid dissipation of a caving arch,gradual formation of a subsidence basin,and periodic ex-pansion of the subsidence basin.The peak range of the front abutment pressure is 8.19～11.86 MPa,and the maximum deviatoric stress reaches 10.76 MPa at a mining distance of 200 m.Although the overall stress level is relatively low,it is significantly higher than the mechanical strength of the rock strata.The maximum surface subsidence values at the end of the three stages are 0.95 m,6.67 m,and 8.85 m,re-spectively,which are notably larger than those observed in western Jurassic coal mines.Sensitivity analysis shows that the R-values of mining height,burial depth,and advancing speed are 5.37,2.76,and 2.01,re-spectively,indicating that mining height has the greatest influence on overburden migration.Conclusions The findings provide theoretical guidance for the prevention and control of mining-induced hazards in ex-tremely weakly cemented Cretaceous strata in Eastern Inner Mongolia.