| The construction of tunnels is often faced with the geological conditions of high in-situ stress and soft surrounding rock.Reasonable support for high in-situ stress soft rock tunnels can effectively control the large deformation of surrounding rock,thereby ensuring the safety of the construction process and the long-term stability of the tunnel.It is significance to study the support method and optimization of support parameters for high ground stress soft rock tunnels.This paper focuses on the research on the supporting effect of bolts in soft rock tunnels with high ground stress,combined with actual engineering cases,and on the basis of existing research results.The bolt support effect and parameter design of the rock tunnel are systematically studied,so as to obtain the bolt support scheme that can be used as a reference for actual engineering.The main research conclusions are as follows:(1)The engineering characteristics of high geostress soft rock tunnels and the failure mechanism of bolt support are studied.The high geostress softness is summarized from four aspects:deformation characteristics,mechanical mechanism of deformation,degree of squeezing of surrounding rock,and factors affecting deformation of surrounding rock the engineering characteristics of large deformation of surrounding rock,and through the law of radial stress and displacement of high geostress tunnel changing with the softening degree of surrounding rock,analyze the failure mechanism of bolt support in high geostress soft rock tunnel to provide a theoretical basis for subsequent numerical analysis.(2)Based on actual engineering cases,ANSYS and FLAC3D are used to establish a three-dimensional model to simulate and analyze the effect of bolt support in the initial support of high-ground stress soft rock tunnels.By comparing the stress and displacement of surrounding rock in the initial support of the tunnel with the non-intrusive anchor,the stress of the supporting structure shows that the effect of anchor support on the deformation of surrounding rock is obvious.After the bolt support in the high-stress soft rock tunnel,the vertical stress of the surrounding rock is relatively stable during the tunnel excavation,and the peak stress remains at about 22.00MPa;the vertical displacement of the surrounding rock gradually increases with the excavation,and the increase is more come smaller.(3)In order to improve the application effect and utilization rate of bolt support in high-ground stress soft rock tunnels,the numerical simulation and optimization of the bolt support parameters are studied,and the changes in the length,spacing,density and prestress of the bolts are analyzed.The effects of rock stress,displacement,plastic zone and axial force of bolts were determined through multi-index evaluation to determine the reasonable support parameters based on specific engineering conditions and provide an effective reference for similar projects.(4)By analyzing the monitoring data of the displacement of the surrounding rock and the stress of the anchor rod in the actual project,it is concluded that the deformation of the surrounding rock during tunnel excavation is generally divided into three stages:large initial deformation,slow deformation in the middle period,and stable surrounding rock period.The monitoring results are compared with the simulation results.The numerical simulation is close to the actual situation and has credibility.Through the above research results,it is concluded that the bolt support has a significant effect in the initial support of high-stress soft rock tunnels.Parameter optimization of the bolt support for high-stress soft rock tunnels can provide a reference for similar projects. |
PDF Full Text Request