Preliminary Study on Double Lining Support Design for Water Plugging of Highway Tunnel under High Water Pressure in Mountain Area Based on Limited Drainage  
[PERSON]  
1 State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing 400074, China 12 Chongqing Jiaotong University, Chongqing 400074, China 2  
[PERSON]  
1 State Key Laboratory of Mountain Bridge and Tunnel Engineering, Chongqing 400074, China 12 Chongqing Jiaotong University, Chongqing 400074, China 213 College of Civil Engineering and Architecture, Chongqing University of Science & Technology, Chongqing 401331, China 12 University of  
bear part of the water pressure and block the passage of groundwater flowing into the tunnel. However, regarding both curtain grouting and radial grouting, the influence of grouting scope on the construction of water-rich tunnels has not been specifically discussed. Technicians often use experience and judgment in the design, and the determination of grouting parameters has become a major task. Due to the thick anti-water-pressure lining, the construction can be inconvenient and difficult, and the tunnel cannot bear water pressure in time. Based on the engineering practice of double-layer initial support to control the large deformation of the tunnel [14; 15; 16; 17; 18; 19; 20], a double-layer initial support (two-layer shotcrete and steel arch combined structure) is proposed to bear the high-water pressure, reduce the thickness of the secondary lining, and enhance the waterproof effect. However, previous designs adopted a single measure of grouting, without considering the damage and stress of the initial support. The research shows that the rich water in the later tunnel still has a great impact on the initial support. Therefore, the scheme of double-layer initial support design plus curtain grouting is proposed to support the surrounding rock area with high water pressure. In previous tunnel construction cases, curtain grouting was used for the construction of water-rich tunnels. Although curtain grouting initially alleviated the risk of water inrush and gushing of the tunnel, the large seepage water pressure in the construction acted on the initial support, so engineers often used strong initial support, and later also used a thick secondary lining structure to control deformation and bear water pressure, which increased the construction investment to a certain extent. Referring to the deformation control technology of double-layer initial support used in the construction of soft rock tunnels, the authors adopts a strategy to bear the external load of the surrounding rock step by step and make full use of the support system formed by the surrounding rock and lining. The first layer of initial support bears the main load, and the second layer of initial support carries out reinforcement and offers a safety guarantee, so as to reduce the secondary lining structure, effectively speed up the project's progress, and reduce investments. Therefore, based on the previous experience of water-rich tunnel treatment, this paper creatively puts forward the structural type of \"curtain grouting + double-layer initial support\" to provide the stability of the anti-water-pressure lining and improve the efficiency of water-rich tunnel construction. To obtain the effect of tunnel radial grouting and curtain grouting based on double-layer initial support, the finite difference method is adopted in this paper to analyze the radial grouting and curtain grouting technologies. These technologies are used in the Yongfutun tunnel of the Guilin-Liazhou expressway. This paper aims to obtain the stress variation law of the surrounding rock deformation, shotcrete, and secondary lining under the operating conditions of different grouting ranges.