Abstract
Based on the special geological conditions of a tunnel in Qingyuan section of Huizhou-Zhanzhou Expressway, FLAC3d numerical simulation software is used to simulate the rheological properties and instability of surrounding rock in large-section fully weathered sandstone section, and the stability and loss of surrounding rock are analyzed. The deformation of the dome and the face at steady state is analyzed. It is found that: 1) when the surrounding rock is in a stable state, the deformation curve of the dome is smooth. When the surrounding rock of the face is unstable, the front of the face appears ahead. Deformation should be first strengthened on the surrounding rock in front of the face. 2) The arched foot is an important part of the instability of the surrounding rock. In order to prevent the expansion of the collapsed part, the arched part should be reinforced. 3) In order to obtain the limit state of surrounding rock stability, the strength of surrounding rock is reduced, and the strength reduction coefficient corresponding to the displacement sudden point is taken as the safety factor of rock stability around the hole, and the stability safety coefficients of surrounding rock of each construction step are greater than 1.2. 4) The dynamic standard values of deformation control in the whole construction stage are obtained by analyzing the deformation curves of each data monitoring point with time in the corresponding time period of each construction step.
Highlights
With the increase of excavation area of large-section tunnels, the construction difficulty increases sharply
3) In order to obtain the limit state of surrounding rock stability, the strength of surrounding rock is reduced, and the strength reduction coefficient corresponding to the displacement sudden point is taken as the safety factor of rock stability around the hole, and the stability safety coefficients of surrounding rock of each construction step are greater than 1.2
4) The dynamic standard values of deformation control in the whole construction stage are obtained by analyzing the deformation curves of each data monitoring point with time in the corresponding time period of each construction step
Summary
With the increase of excavation area of large-section tunnels, the construction difficulty increases sharply. Determining the surrounding rock failure mode of the fully weathered argillaceous sandstone section of large-section tunnel is to ensure construction safety, construction progress and prevention of landslide. Domestic and foreign scholars have carried out more research on the instability and monitoring and early warning of surrounding rock in large-section tunnels. Ma Shiwei et al relied on the large-section shallow-buried loess tunnel, and proposed the idea and method of real-time early warning of tunnel collapse. Combined with the special geological conditions of a tunnel in Qingyuan section of Huizhou-Zhanzhou Expressway, the numerical simulation software is used to simulate the rheological behavior and instability failure of the surrounding rock in the large-section fully weathered sandstone section. By analyzing the deformation curves of each data monitoring point in the corresponding time period of each construction step, the dynamic standard value of deformation control in the whole construction stage can be obtained [6]
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