Stability Of Hydraulic Filled Bead Cave To Tunnel Impact Analysis

In recent years,a large number of mountain tunnels have been built in southwest China.The situation of these tunnels passing through bad geology is increasing day by day.The influence of water pressure filling karst caves on tunnels is particularly obvious.Due to the different degree of water pressure in Karst caves,water inrush and mud inrush are very easy to occur in the process of tunnel construction,which seriously affects the life safety and production cost of tunnel constructors.Based on the Xingaopo Tunnel Project and summarizing the existing research results at home and abroad,this paper makes a systematic and in-depth study on the influence of water-filled Beaded karst cave on tunnel structure by means of numerical simulation.The main contents and results are as follows:(1)Based on the statistical analysis of a large number of karst tunnel water inrush data,the karst development characteristics are analyzed from the perspective of soluble rock characteristics and karst geological structure characteristics,and the karst cave development characteristics and karst filling medium characteristics are summarized.The karst development characteristics and tunnel water inrush mechanism are analyzed from the aspects of karst water inrush mechanism and water inrush control factors.(2)Based on the Xingaopo tunnel project,numerical simulation is carried out by FLAC3 D software combined with actual working conditions.Three kinds of advanced support schemes are simulated,i.e.small pipe grouting,pipe shed grouting and pipe shed + small pipe grouting.According to the displacement around the tunnel and stress state of the support structure,comprehensive analysis is made on the filling of different positions such as no cave,top cave,left cave and bottom cave.By comparing the influence of the type of string beads karst cave on the tunnel structure,the most disadvantageous position of the influence of the string beads karst cave on the tunnel is determined(3)Combining with the engineering geology situation and supporting parameters in site,the stability of surrounding rock during construction is analyzed by controlling a single variable when filling bead caves with different diameters,pressures and distances exist on the left side of the tunnel through numerical simulation,and the displacement and deformation law of the tunnel structure are summarized.(4)Combining with the results of disaster prevention and control of karst tunnels summarized in previous engineering practices,this paper puts forward the principle of water inrush prevention and control which has universal applicability for Karst tunnels,summarizes the characteristics of different types of karst development,and determines the corresponding countermeasures for water inrush control of strong karst tunnels.