Abstract

To study the stability of a transition section of a tunnel from soft to hard surrounding rock under seepage conditions, FLAC3D software was used to numerically simulate the transition section of the Laomushan Tunnel from the Shiqian to Yuping (Dalong) Expressways in Guizhou Province, China, and to explore different working conditions. The characterization of the tunnel seepage field, stress field, and displacement field and the analysis of the force of the primary lining support structure describe the influence of the seepage field on the stress field distribution and displacement field changes. The reliability of the calculation results is verified by comparison with displacement measurements collected during field monitoring. The design values of the primary support structure parameters of the transition section from soft to hard surrounding rock of the Laomushan Tunnel basically met the strength requirements. The research results provide references for the design and construction of similar projects.

Highlights

  • With the continuous development of China’s economy, the total mileage of highway in China is gradually increasing

  • Based on solidfluid coupling theory, Zhang et al [3] used FLAC3D finite difference software for simulation and on-site monitoring to analyze the stability of a tunnel excavation, obtained the risk prediction function of the tunnel excavation under confining pressure, determined the most dangerous excavation depth of the face, and provided a reference for subsequent work

  • Zhao et al [6] discussed the effect of solid-fluid coupling on the stability of antiburst rock pillars and obtained the safety coefficient of the antiburst rock pillar by constructing an analysis method that links to the solid-fluid coupling strength reduction method for karst cave water inrush, providing a new way to research the stability

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Summary

Introduction

With the continuous development of China’s economy, the total mileage of highway in China is gradually increasing. Based on the study of the solid-fluid coupling effect and the stability of the surrounding rock during the blasting construction of the transition section from soft surrounding rock to hard surrounding rock of the Laomushan Tunnel, considering the different grades of the surrounding rock, the solid-fluid coupling analysis of the excavation of this tunnel section is carried out by using FLAC3D finite difference software; the distribution characteristics of the seepage field and their influence on the stability of this transition section are discussed. Taking the transition section from soft to hard surrounding rock of the YK76 + 415-YK77 + 451 section as the research object, based on fluid-structure coupling theory (2012) [12, 13], a numerical calculation model of the Laomushan Tunnel is established by FLAC3D software. In the process of seepage calculation, the fluid-solid coupling calculation mode is enabled, the rock-soil unit is set to the isotropic seepage model (MODEL fluid fl-isotropic), and the lining is simulated by the shell element set to the impervious material model (MODEL fluid fl-null). e initial support is made of C25 concrete with a thickness of 80 cm. e bolts are selected as left-handed nonlongitudinal rebars with a diameter of

Anchor rod
Contour of Gp pore pressure
Calculated by volumetric averaging
Le arch waist Vault Right arch waist
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