Analytical study on pretensioned bolt-cable combined support of large cross-section tunnel
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alytical study on pretensioned bolt-cable combined support of large cross-section tunnel *
LUO JiWei, ZHANG DingLi, FANG Qian , LI Ao, SUN ZhenYu & CAO LiQiang Key Laboratory for Urban Underground Engineering of the Ministry of Education, Beijing Jiaotong University, Beijing 100044, China Received November 13, 2019; accepted January 18, 2020; published online May 14, 2020
To study the mechanical responses of large cross-section tunnel reinforced by pretensioned rock bolts and anchor cables, an analytical model is proposed. Considering the interaction between rock mass and bolt-cable support, the strain softening characteristic of rock mass, the elastic-plastic characteristic of bolt-cable support, and the delay effect of installation are considered in the model. To solve the different mechanical cases of tunneling reinforced by bolt-cable support, an analytical approach has been put forward to get the solutions of stress and displacement associated with tunneling. The proposed analytical model is verified by numerical simulation. Moreover, parametric analysis is performed to study the effects of pretension force, cross-section area, length, and supporting density of bolt-cable support on tunnel reinforcement, which can provide references for determining these parameters in tunnel design. Based on the analytical model, a new Ground Response Curve (GRC) considering the reinforcement of bolt-cable support is obtained, which shows the pretension forces and the timely installation are important in bolt-cable support. In addition, the proposed model is applied to the analysis of the Great Wall Station Tunnel, a high-speed railway tunnel with a super large cross-section, which shows that the analytical model of bolt-cable support was a useful tool for preliminary design of large cross-section tunnel. bolt-cable combined support, analytical model, pretension force, large cross-section tunnel, reinforcement Citation:
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Luo J W, Zhang D L, Fang Q, et al. Analytical study on pretensioned bolt-cable combined support of large cross-section tunnel. Sci China Tech Sci, 2020, 63, https://doi.org/10.1007/s11431-019-1531-9
Introduction
In recent years, with the development of underground engineering, the design and construction of large cross-section tunnels have received extensive attention. With the increase of tunnel dimension, the rock mass stress distribution due to tunnel excavation would be more complex, and the deformation control of rock mass would be more difficult, which has brought challenges to the design of tunnel support. Rock bolt is a useful tool for tunnel construction, which can considerably improve the stability of tunnel surrounding rock [1]. The effective use of rock bolts for underground structure support began in the 1940s in the mining industry
[2]. From the 1970s up to today, the rock bolt has been widely applied in tunnel projects [3–5], and a series of studies on rock bolting have been carried out [6–14]. For large cross-section tunnels, attempts have been made to improve the rock bolting technologie
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