Abstract
The setting of circumferential distance of system anchor rod in highway tunnel is related to the safety of tunnel structure, and also affects the project cost. The “code for design of highway tunnels” issued in 2018 also adjusted the circumferential spacing arrangement of the system bolts of the tunnel. Based on a highway tunnel project, the circumferential spacing of system bolts in deep buried section of grade V surrounding rock is adjusted from 0.8m to 1.2m, and the numerical simulation and comparative analysis before and after the optimization of bolt spacing are carried out. The field monitoring and measurement data show that the surrounding rock deformation after adjustment has little effect, and the cavern is stable as a whole, which can guide the optimization implementation of subsequent sections.
Highlights
System anchor bolts are an important part of the primary support structure of a tunnel
Traditional theory holds that system anchor bolts has the functions of suspension, span reduction, reinforcement and composite beam, etc. [1], and recommended range for system anchor bolt spacing setting is given in relevant specifications [2]
Li Dejun [4] et al believed that increasing bolt length and reducing bolt spacing within a certain range can effectively improve the stress of anchor bolts, but it has no obvious influence on the deformation of tunnel surrounding rock and the overall stress of primary support
Summary
System anchor bolts are an important part of the primary support structure of a tunnel. Li Dejun [4] et al believed that increasing bolt length and reducing bolt spacing within a certain range can effectively improve the stress of anchor bolts, but it has no obvious influence on the deformation of tunnel surrounding rock and the overall stress of primary support. Chen Jianxun, et al [9] conducted a comparative test on several loess tunnels with and without system anchor bolts, and believed that the application of system anchor bolts delayed the best time of primary support, increased the deformation of surrounding rock, and the effect of system anchor bolts was not obvious; on the contrary, after canceling the system anchor bolts, the deformation and stress of the primary support structure of the tunnels are in good working condition, and system anchor bolts cancellation can significantly improve the quality and efficiency and reduce the cost. Based on a highway tunnel project in Yunnan Province, this paper optimizes and adjusts the spacing setting of the system anchor bolts of the tunnel system by numerical simulation and comparative analysis of field monitoring data
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