Abstract
The problem of large deformation is very prominent in deep-buried tunnel excavation in soft rock, which brings serious potential safety hazards and economic losses to projects. Knowledge of the stress field distribution and deformation law is the key to ensuring rational design and safe construction in large deformation tunnels of soft rock. As described in this paper, theoretical analysis, numerical simulation and field monitoring were employed to investigate the surrounding rock stress and displacement state in the Dongsong hydropower station in Sichuan Province, China. The results show that the short-bench construction method can effectively control the deformation of surrounding rock and range of the plastic zone. In order to reserve enough working space, the optimum bench length in the actual construction was 10 to 14 m. The peripheral displacement and plastic radius decreased with the increase of tunnel support strength and the advance of supporting time. The displacement can be effectively controlled by applying the second lining in time at a position about twice the diameter of the hole (16 m) from the working face. A reasonable reserved deformation should be adopted to avoid secondary expanding excavation. The values of different positions in the tunnel laterally and longitudinally may be different, and adjustments are needed according to the actual situation.
Highlights
With the continuous railway and highway construction in China, tunnel engineering has been developing in situations of long, large and deep burial [1,2,3,4,5,6,7]
This paper revealed stress field distribution and deformation law in a large deformation tunnel of
This paper revealed stressnumerical field distribution and deformation law inwere a large deformation tunnel soft rock
Summary
With the continuous railway and highway construction in China, tunnel engineering has been developing in situations of long, large and deep burial [1,2,3,4,5,6,7]. The characteristics of deformation and failure of a typical roadway were analyzed, and it was proposed that the fundamental reason for the failure was that traditional support methods and materials could not control the large deformation of deep soft rock These studies are mainly based on the qualitative analysis of engineering cases. Jiang et al [42] proposed defining the large deformation of soft rock as a progressive plastic deformation failure of tunnel and underground engineering surrounding rock with an obvious time effect. Through theoretical study of the surrounding rock stress field, analysis of the space-time effect of numerical simulation and real-time feedback of field monitoring, the whole process of excavation and support of a large deformation tunnel in soft rock is studied. The results can further deepen and enrich the study of this kind of tunnel
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