Research On The Stability And Monitoring Method For Grouting Curtain Under High Seepage-pressure

Zhangmatun iron-mine is famous for its huge hydraulic dischage, it is one of the earliest mine to found the grouting-curtain engineer for water control.The grouting-curtain can seal and cut the seepage way, and then greatly reduce water-dischage volume, protect the original groundwater environment surrouning the mine area, and remarkably advance ecomonic profit of the mine. However, for increasing of the mining depth, the difference of hydraulic pressure between inside and ouside of the grouting-curtain became very bigger. Furthermore, the grouting-curtain was distrubed by excavating and mining perennially. Therefore, the satbility of grouting-crutain was affected obviously, and greatly threatened the underground working. Accordingly, based on investigation to hydrogeologic condition, mechnical parameters, seepage characteristic, AE (acoustic emission) activity et al, the three-dimensional geological and mechanical model were founded, and numrical analysis was conducted on the stress distribution and stability in the grouting-curtain and surrounding rockmass. The microseismic monitoring and analyzing system was established, and data exchanging between the microseismic information and numberical simulation system for rock failure analysis. As a result, the relationship between the stress evolvement and microseismic activity was achieved, and the temporal and spacial distribution on the process of water inrush when grouting-curtain destoryed. Finally, the forecasting system for the water inrush was founded. The main conclusions are following listed.(1) The seepage coefficient was not obviously changed in the beginning stage when the grouting-curtain specimans sufferd pressure. When the pressure reached80%of the specimans’ strength, the seepage coefficient had increaed fastly, and had geted its maximun after the specimans totally destoryed. The AE activity showed well corresponding relation with the changing of seepage coefficient, its number and energy hold low level in the early pressure stage and became flourish when the pressure to80%strength and maitained to the completely destroyed.(2) The peak value of strain-seepage curve was later than strain-stress peak value, while the peak value of strain-AE rate was ealier than strain-stress peak value. This result indicated that numerous microcracks would emergence before the macro fracture occured in rock material.The macro-crack results from evolution and accumulation of the numerous microcracks. The permeability of rock material was greatly effeced by the occurence of macrocracks;it increased along with evolution of macrocracks and reaches the peak value after rock was completely destroyed. Namely, the immediate factor that affect the occurance of water inrush is the macrofailure of rockmass. The conclusions provide theory foundation for the application of microseismic to forcasting water inrush in mine.(3) Rapidly increaseing of AE rate, obviously raising of AE energy and quickly descending of b value are the portentous information indicate the rockmass will failure soon.(4) Numerical calculation on three-dimension stress and analysis on the stability of grouting curtain were conducted. Mining activity disturbed the in-situ stress greatly, stress concentration appeared on the excavated-region side, the maximun value is40Mpa; stress decreasing appear on the roof and floor of excavated region, the minimum value is O.lMPa. The connected region of O2-Ⅱ marble and diorite in southwesten area of grouting curtain is the main seepage way because of the high stress and broken rockmass. The safty factor of grouting curtain calculated by RFPA-Centrifuge is2.6, which indicated that the state of grouting-curtain is safe in the present stress condition.(5)The monitoring and analyzing system for stability of the grouting-curtain in Zhangmatun iron mine was founded. The real-time and continuous monitoring and analyzing for the grouting-curtain and surrounding rockmass were achieved. Therefore, The predicting and forecasting abiltiy for the mining dynamical disaster such as water inrush was advanced.(6)The spatial distribution of microseismic events and stress field achieved by3-D numerical simulation were well coincident. It is indicate that combination of microseismic technique and3-D rock failure process analysis can acquire accurately result for the stability of underground rockmass. This result is very significant for the predicting and forecasting to the mining dynamical disaster.