Study On Overlying Strata Stability And Surface Subsidence With Effect Of Backfilling Method In The Luohe Underground Mine

Based on the main parts of a scientific research project--Monitoring and Research for Surface Stability through Backfilling Method in Luohe Underground Mine, this dissertation focuses on the issues of surface subsidence and overlying strata stability caused by underground backfill mining. A number of study methods, such as theory analysis, experimental testing and numerical simulation, are used to research the mine safety during mining process. Contents of this dissertation are mainly illustrated as follows:(1) The support capacity of tailings backfill to the stope country-rocks is determined by its strength, which exerts large influence on the stability of overlying strata after backfill mining. In order to study the strength of cemented tailings backfill of the Luohe mine, theoretical and experimental methods were applied to study the related factors, which could affect its strength. The influence factors of backfill strength and failure process under loading impact were achieved according to the experimental and analyzed results.(2) Taking backfilling tailings in underground mined-out stope as the object of study, an analytical seepage model was established and the seepage pressure and flow formula of water in backfill-rock interface were deduced according to the practical situation which confirmed the initial and boundary conditions. Based on that, the seepage law and influence factors in the backfilling tailings were analyzed.(3) Based on the mining method of the Luohe mine, a subsidence mechanical model of panel roof was conducted and the related surface settlement formulas were deduced according to the Navier dual-trigonometric series. Accordingly different factors affecting the maximum surface subsidence were analyzed respectively, such as the foundation coefficient, the located stope depth, the ratio of length to width of a panel, the panel roof thickness, the rock Young’s modules of roof, etc. The stress distribution in the roof was also analyzed.(4) A numerical model of 13# geological profile in the Luohe mine was established by using 3DEC discrete element software, according to the geological data and rock mass properties of the mine. Based on the mining design, the mining process of this profile was simulated and the surface subsidence and stress distribution in the overlying strata was analyzed. Also experimental method of similar simulation was used to research the displacement and stress variation of overlying strata during mining process. In situ, a GPS monitoring system was established to record the surface subsidence caused by excavation and backfill mining.(5) The application of Fourier transform and HHT (Hilbert Huang Transform) in analyzing the signals of blasting vibration was introduced. By using this method, the analysis for vibration signals of ground surface and refuge station was conducted, where the vibration characteristics caused by blasting were obtained. A blasting numerical model in underground mining was also established by using ANSYS\LS-DYNA, and the stability of drilling chamber, slot-cut area, surrounding rocks of drifts, and overlying strata was analyzed, and the transmission laws of blasting vibration wave in the strata were obtained. In addition, the vertical vibration velocities and effective stresses of different locations were calculated and analyzed with effect of double maximum explosive charges in one delay time.