Study On Risk Analysis And Treatment Technology Of Water Inrush In Deep Shaft Of High Pressure Water-rich Granite Stratum

At present,the problem of water gushing is prominent when railway tunnel shaft passes through water-rich broken rock strata.Galigong Mountain tunnel shaft is the deepest railway tunnel shaft in China at present,and many water gushing accidents occur in the construction process.Taking gaoligongshan tunnel shaft as the research background,based on typical engineering surrounding rock sections with high-pressure water-rich granite and joint fissure development,this study analyzed the characteristics of granite rock strata and hydrogeological conditions on the basis of obtaining the distribution characteristics of joint fissure and hydrogeological characteristics of surrounding rock.The calculation and analysis of the water inflow of the shaft and the stability of the support structure under the condition of different grouting water plugging measures and stratum water abundance are carried out,and the reinforcement effect and grouting parameters of the shaft grouting reinforcement are discussed and optimized.The main contents and conclusions of this study are as follows:(1)Based on the geological survey data,the three-dimensional geological model of gaoligongshan tunnel shaft is established.Combined with the existing water inrush case analysis of shaft and construction risk assessment management standards,the risk list of water inrush of shaft is established,and based on FAHP-TOPSIS method,combined with threedimensional geological model and actual water inrush risk of shaft,the risk index is evaluated,and the risk grade of water inrush of shaft is determined.(2)Based on the seepage continuity equation and Darcy’s law,the seepage field theoretical model of vertical shaft is derived to simulate the water inrush accident of vertical shaft,and the distribution law of water pressure characteristics of vertical shaft and support structure under the influence of different construction period,different grouting reinforcement parameters and different underground water level is discussed.The results show that the water inflow of the shaft will be higher than the maximum pumping capacity of the shaft if the grouting is not adopted in the case of no supporting structure,and it is easy to cause water gushing accident.After supporting structure is applied and grouting measures are taken,the grouting control effect is good,and the grouting parameters are optimized based on the research structure.(3)Based on the finite difference numerical simulation software,the calculation method of water inflow of shaft is clarified,the water inflow and structural stability of shaft under different construction conditions are calculated and analyzed,the simulated predicted water inflow is verified by combining with the actual monitoring data on site,and the water plugging effect of pre-grouting reinforcement measures on surrounding rock is discussed.Based on the hydrogeological condition of gaoligongshan tunnel shaft,the grouting reinforcement parameters such as permeability coefficient and thickness of grouting ring are optimized.Combined with the case of gaoligongshan tunnel shaft construction,the water plugging measures of pre-grouting and its specific technological parameters under complicated geological conditions of the shaft are put forward.There are 77 pictures,24 tables and 100 references in this paper.