| Water-rich loess tunnel often has large-scale deformation with the complex space-time distribution.Mastering the fine space-time deformation characteristics of initial support is conducive to accurate construction strategies and ensures construction safety and quality.Based on the project "analysis theory and deformation control technology of surrounding rock and structure of vertical joint water-rich loess tunnel" of Shanxi Road and Bridge Construction Group Co.,Ltd.,this paper analyzed the Yulinzi tunnel in Qingyang,Gansu Province using field measurement and numerical simulation.This paper analyzed the fine space-time deformation characteristics of the tunnel and put forward the corresponding deformation control means based on these characteristics.The main research contents and achievements were as follows:(1)The physical and mechanical parameters of loess in the Yulinzi tunnel were obtained by the indoor test method.Based on the analysis of conventional monitoring measurement data,the dynamic tracking measurement was carried out by using three-dimensional laser scanning technology.It was revealed that the deformation of the tunnel presented three stages with the development of time.The spatial distribution of deformation was complex,the settlement and the settlement rate of the arch were the largest,and there was a settlement difference between the left and right sides,resulting in serious distortion.(2)The numerical simulation of the long-distance cyclic excavation process of water-rich loess tunnel under the three benches seven-step excavation method was carried out.The fine space-time deformation characteristics of loess tunnels with different water-rich degrees were analyzed,and it was revealed that the tunnel would produce distortion under this left-right alternating excavation sequence,and the distortion degree was greatly affected by the moisture content of loess.The existence of distortion would damage the supporting structure.The additional stress caused by distortion was calculated by the structural mechanics’ method,and its influence on the supporting structure was analyzed.(3)Based on the obtained finer characteristics,aiming at the dangerous step and part in the tunnel excavation process,the treatment scheme of strengthening advance support was put forward.Aiming at the problems of large deformation of the arch crown and distortion deformation,the deformation control effects of surrounding rock reinforcement,adjustment step sequence,and differential support were analyzed by the numerical simulation method.The curtain grouting method was used to control the deformation of the Yulinzi tunnel,which was verified by the measurement of the tunnel monitoring robot.The effect of this method was good. |
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