Creep Simulation Of Overburden Strata In Gypsum Mine Goaf And Stability Evaluation Based On Displacement Monitoring

The massive mining of mine resources has caused large area of goaf.The collapse of overlying rock,surface deformation and even large area collapse caused by the instability of the goaf will seriously threaten the lives of the residents,the safe production of enterprises and the ecological environment.Therefore,studying the instability of the goaf and evaluating the stability of the goaf have great significance in guiding the goaf control and ensuring the safety of residents' life and production.In this paper,based on the project of optical fiber monitoring and control in the goaf of Pingyi gypsum mine,Shandong Province,investigate the tectonic geological conditions,hydrology and engineering geological conditions and the status of the goaf in the gypsum mine goaf,comprehensively consider the influence factors of the different lithology of the overlying area,the different space position of the goaf and the time effect of the overlying rock subsidence in the goaf,and by combining the engineering practice and using the improved creep constitutive model,calculate the subsidence of the strata of the different depth of the overlying rock in the goaf,compare and analyze the influence of the Mohr constitutive model and the improved creep constitutive model on the numerical calculation results.Simulate and calculate the process of creep and subsidence of strata at different depths in goaf.By selecting the suitable creep model to describe the whole process of rock creep,fit the model by the least square method,get the model creep parameters,and carry out the verification.Obtaine the creep rate boundary value of rock from the creep deceleration stage to the isokinetic stage,the isokinetic stage to the joining stage,by calculate the time derivative of the model,and take creep rate that enters the accelerated creep stage as critical value of the goaf instability.According to the occurrence characteristics of the goaf in Pingyi gypsum mine,the implementation of the optical fiber monitoring method is explained,and the data of the overlying displacement in the goaf are obtained,which proves the rationality of monitoring the overlying displacement of the gypsum mine by using the optical fiber monitoring method.Divide gypsum ore stratum and calculate their critical value of creep rate,determination of the creep state of the goaf,taking this as an evaluation index,establish the evaluation index system of goaf by using fuzzy matter element theory,the results show that the stability of goaf in I-9,I-11,I-7 and I-12 is the best,and put forward prevention measures.