Study On Stability Of Tunnel Portal In Fractured Rockmass On High And Steep Slope And Its Control Measures

Mountain tunnel entrance slope stability directly determines the safety of tunnel entrance, the corresponding entrances to the tunnel construction and affects the stability of the slope.In this thesis, the stability of the slope of the entrance to the cave is analyzed by the numerical simulation method, and the dynamic response of the slope is considered. The main research work and results are as follows:(1) The importance of studying the slope stability of mountain tunnel portal section to the safety influence during the construction period and operation period is defined by collecting and arranging the data of the interaction between the tunnel project and the slope engineering. The main factors which influence the stability of mountain tunnel portal section are analyzed, and the mechanism of the broken ring of the slope during the excavation of the tunnel is studied by using the method of slice method. According to some engineering disasters, the broken ring mode of the slope of the tunnel portal section is summarized.(2) For all the slope of the blue line, the strength reduction method is used to analyze the stability of slope under static and earthquake dynamic load through the numerical analysis of the single variable method, and according to the geological conditions of 32 tunnels in ChenLan line, stability classification of the import and export section of the 32 tunnels to provide reference for the engineering use of the corresponding reinforcement measures.(3) Combined with the practical project of Maoxian tunnel exit slope reinforcement, the numerical method is used to analyze the installation angle of the anchor in slope reinforcement. Compared with the method of combining theory with practical engineering, getting 15 degree angle cable of high and steep slope of weathered phyllite in mountain area to provide technical guidance for the reinforcement of slope phyllite.(4) The stability of fractured mass rock slope is treated as the slope surface of in natural conditions, reinforcement of the unexcavation hole condition and reinforcement excavation hole under the condition was studied. Analysis results show that, it can be proved that the slope reinforcement measures are effective and safe in the construction of the portal section. The line of the other similar openings can be referenced to the slope reinforcement and the optimal length of pile is studied by changing the length of anti slide pile. And it is concluded that as long as the anti slide pile passes through the weak and broken strata to a certain distance, appropriate reduction of the length of the pile will not cause too much impact on the stability of the slope.(5) The broken zone of the slope surface of the outlet section was eliminated and through the numerical analysis of the anti slide pile with anchor cable to reinforce the outlet slope of Maoxian tunnel, the results show that the slope stability of Maoxian tunnel is stable after the anti slide pile is strengthened as a whole.