The Research on Construction Key Technology and Ability Analysis of Shallow Tunnel Surrounding Rock
|School||Central South University|
|Course||Bridge and Tunnel Engineering|
|Keywords||shallow tunnel stability milling excavation method tunnel face pre-reinforcement technology|
LiuYang River Tunnel, a passenger special line tunnel crossing the river and urban, is the first tunnel which milling excavation method and pre-reinforcement technology have been applied.It has many features of the construction method of tunnel and urban underground engineering.The stability analysis of tunnel surrounding rock and related research of construction technology engineering are one of the difficulties but also a hotspot in current engineering.Urban River Tunnel not only has the features of general tunnel construction, but also has more exigent reins on surface settlement. Therefore, the stability of the surrounding rock and tunnel face in the tunnel construction process is a key step to control surface settlement. The stable surrounding rock and safety support measures provide a fundamental guarantee for tunnel face excavation in the tunnel construction process.For the above-mentioned reasons, this article is based on the stability analysis of tunnel surrounding rock and the research of construction technology engineering of LiuYang River Tunnel on Wuhan-Guangzhou High-speed Railway, theoretical analysis, experimental study and numerical simulation have been used in this paper, the contributions are as follows:(1)A failure model of the stability analysis of shallow tunnel surrounding rock in inclined ground surface has been built based on the Hoek-Brown generalized nonlinear strength criterion and nonassociated flow rule, associated-nonassociated flow rule is introduced by modify the instantaneous internal friction angle and cohesive strength of nonlinear geological materials. Upper bound theorem of limit analysis and strength reduction technique have been applied to study the effects of non-linear failure criterion and nonassociated flow rule on the surrounding rock pressure and stability of the shallow tunnel. The research results can offer beneficial reference in the optimal design of shallow tunnel support structure and the stability analysis of surrounding rock.(2) Based on the Hoek-Brown generalized nonlinear strength criterion, took the excavation of the tunnel as a plane strain problem and the force of the anchor applied on the surrounding rock as radial stress, stability analysis of differential equations before and after anchor was applide on the surrounding rock were established, the calculation method of the stress field before and after tunnel surrounding rock apply anchor, displacement field and plastic zone radius and anchor ultimate load were obtained. Parameter analysis and engineering application show that the theoretical calculation method has some value in engineering application. These achievements have been guided the anchor supporting parameters of surrounding rock in Liu Yang River Tunnel.(3) Forming a matching mode of milling excavation method of large cross section tunnel passenger dedicated line, selection of milling digging equipment and its machinery works, the efficiency of milling excavation method is improved significantly.(4) Pre-reinforcement of the tunnel face is studied based on the special geological environment conditions of Liu Yang River Tunnel, three arching effects after surrounding rock excavated are explicated, stability classification system of the tunnel face is builded; indoor model experiment and field experiments of pre-reinforcement of the tunnel face of Liuyang river tunnel are studied, the critical technologies of pre-reinforcement of glass fiber bolt in tunnel face and the methods of monitoring and measuring the deformation of advance core soil and tunnel face are proposed.