| With the continuous development of China’s transportation infrastructure,the length of highway tunnels has been continuously increasing,the span has been continuously increasing,and the depth of burial depth has been continuously deepened.More and more high-stress soft rock tunnels have been encountered.High-stress soft rock tunnels often have serious large deformation problems.Traditional passive support has been difficult to meet engineering requirements and has not yet been resolved.With the development of pre-stressed anchor cables technology,pre-stressed anchor cable support technology can be introduced to transform passive support into active support and provide new support means for high-stress soft rock tunnels.Based on the national key project Muzhailing Highway Tunnel,this paper innovatively proposes the method of combined support using anchor rods and prestressed anchor cables.Through theoretical analysis and numerical simulation,the parameters of the combined support of anchor rods and cables are analyzed.The results have been analyzed and researched,which can provide reference for the design of high-stress soft rock tunnels.The main work and achievements of the thesis are as follows:(1)Analyze the type,instability and mechanical properties of high-altitude soft rock in detail,discuss the mechanical mechanism of instability and deformation failure of underground soft rock in high geostress,and determine the excavation stress change and deformation and displacement plasticity of surrounding rock in tunnel engineering,Characteristics of change;(2)The support mechanism of prestressed anchor cables was explored,and the load transfer mechanism of the prestressed anchor cables in the anchorage section was analyzed.The internal friction angle,Poisson’s ratio,and lithology modulus of the rock mass were obtained and the stress distribution of the prestressed anchor cables was obtained.Influence laws;(3)Using Flac3 D numerical simulation software software to establish a variety ofworking conditions for numerical simulation of excavation and support of high-stress soft rock tunnels,and to analyze the influence of different prestressed anchor cable parameters(length,spacing,prestress)on the effect of soft rock tunnel support;(4)Based on the analysis of the effects of the initial support for the Muzhailing Highway Tunnel,the initial support form of joint support with bolts and cables was proposed,and the combined support method of bolts and cables was simulated using Flac3 D software.Through the comparison with the changes of displacement,stress,and plastic zone of surrounding rock with the traditional initial support methods,the effect of joint support is obtained. |
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