| Promoting interconnectivity of transportation infrastructure is an essential requirement of our development.Tunnel engineering as an important part of traffic infrastructure construction,its engineering status is increasingly prominent.With the deep implementation of "One Belt,One Road" strategic planning and western development,underground engineering gradually develops to the direction of "bigger and deeper",and the large deformation of compressed-type weak surrounding rock has become one of the main problems facing tunnel engineering at present.Therefore,it is of far-reaching significance and engineering value to carry out theoretical research on large deformation control of compressed-type soft surrounding rock tunnel.With the development of tunnel engineering technology,the concept of "deformation release" has become a common understanding when facing the large deformation problem of extruded soft rock tunnel,so that pressure support has gradually begun to replace the traditional rigid support.In this paper,a series of research are carried out by means of theoretical analysis and engineering application,aiming at the deficiency of theoretical researches on the interaction between surrounding rock and support of the tunnel,based on the depressurization support of extrusion large deformation tunnel.The main research contents are as follows:(1)Aiming at the problem that the nonlinear hardening stage of shotcrete cannot be considered by the existing theoretical analysis methods,the nonlinear hardening stage of shotcrete is divided into several linear stages based on the equivalent Young’s modulus theory,and the theoretical calculation model of shotconcrete is established.By comparing the existing engineering data,it is found that the model can accurately predict the mechanical response law of tunnel surrounding rock and lining,and provide a reliable basis for tunnel engineering design.This method has been successfully applied in Rongjiawan tunnel,and then the sensitivity parameters are analyzed comprehensively.(2)In view of the problems existing in the design theory of large deformation circum-compression support for soft rock in the compaction stage,a multi-segment line approximation method is proposed to simulate the compaction stage of the compression structure with embedded high-pressure elements;Based on this method,the calculation method of stress characteristic curve of tunnel surrounding rock support in nonlinear compaction process is established,and the analytical equation of each stage is proposed.Furthermore,the parameter sensitivity of concatenation structure in nonlinear compaction stage is analyzed.(3)In view of the unclear interaction mechanism between compression support and surrounding rock,a theoretical calculation method of tunnel displacement and stress response under compression support was established based on the convergence-constraint theory,and a reasonable installation position of high compressibility elements under different mechanical properties of surrounding rock and ground stress conditions was given.Based on the theoretical model,a comprehensive parameter study is carried out,which provides some suggestions for the application of compression support in actual tunnel engineering.(4)In view of the unclear mechanism of the application of compression support and bolt combined support in large deformation tunnels,the influence of the combined action of anchorage surrounding rock and compression support on the tunnel displacement and stress response is analyzed.Based on the homogenization method,the calculation method of surrounding rock in the anchoring zone is established,and the theoretical calculation solutions of the plastic zone,stress field and displacement field of the circular tunnel under the combined support of pressure and bolt are given.Finally,based on the analytical solution,the relative parameters of the bolt and the supporting parameters of pressure relief are analyzed and studied. |
