Research on Arch Buckle Optimization and Field Monitoring of Underground Excavation Station in Loess Area
In order to explore the variation law of surface settlement and surrounding rock stress induced by the arch construction sequence of PBA method underground excavation station in loess area,a three-dimensional calculation model of subway underground excavation station is established by using the finite difference software FLAC 3D,and the surrounding rock stress changes and surface settlement prediction analysis induced by different arch construction sequences are completed.FLAC 3D prediction shows that the maximum settlement of ground settlement caused by the four construction sequences is located in the center line of the station,and the settlement curve is V-shaped.The cumulative displacement,the stress of the surrounding rock and the induced ground settlement are the smallest for the"sides after central"excavation of the arch crown with staggered spacing constructing sequence.For the"sides after central"excavation of the buckle arch,the displacement of deep soil is small,the change of soil structure and the change of interaction force are small,and the influence of floor heave on the construction of pilot tunnel is effectively weakened,which is convenient to control the surface settlement and is beneficial to the construction safety.Based on the staggered construction sequence of the arch"first middle and then side",the on-site monitoring scheme of the arch stress and surface settlement during the construction of the arch of the underground excavation station is formulated.The engineering practice shows that the measured curve is basically consistent with the FLAC 3D simulation results,and the FLAC 3D prediction calculation is reasonable and feasible.
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