Study on the Dynamic Response of Rock Mechanics and Numerical Simulation of Excavation Sequence Optimization in Ultra-large Span Variable Section Tunnels:Taking Suzhou Changjiang Road South Extension Project-Qizishan Tunnel Project as an Example
In order to ensure the construction safety of the super large-span variable cross-section tunnel,while considering the construction convenience and efficiency.Taking Suzhou Changjiang Road South Extension Project-Qizishan Tunnel Project as an example,the excavation process of continuous arch to large-span section was studied by using FLAC3D numerical simulation in two working conditions:whether to remove or retain temporary support during excavation,and whether to adjust and optimize the excavation sequence of the super large-span section.Comparative analysis was conducted from the perspectives of surrounding rock displacement and stress.The results show that there are significant differences in surrounding rock displacement and stress under the two working conditions mentioned above.In the continuous arch to large-span section,the surrounding rock disturbance is smaller and the surrounding rock stress changes less when temporary support is retained during the excavation process.In the super large-span section,the optimized excavation sequence method reduces the final settlement value of the arch crown by 8.60％,reduces the final uplift value of the arch spring line by 4.01％,reduces the final horizontal convergence values of the left and right side walls by 9.42％and 16.70％respectively,and the optimized method results in relatively small changes in stress of the surrounding rock at various measuring points.Based on the comparative analysis results,optimization suggestions are proposed for on-site construction:for the continuous arch to large-span section,retain temporary support during excavation and use a gantry arch frame as a temporary support method to ensure construction convenience,for the super large-span section,adopt optimized excavation sequence for construction to further reduce surrounding rock disturbance and improve construction safety.
construction of super large-span variable cross-section tunnelsnumerical simulationFLAC3Doptimization of construction method
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