OPTIMIZATION ANALYSIS OF CONSTRUCTION SCHEMES FOR SUBWAY STATION WITH EIGHT-DRIFT BY PBA METHOD
As the width of subway stations constructed using the open-cut pile method increases,the number of guid-ing tunnels also increases,leading to greater disturbance and heightened construction risks.This study focuses on the Dazhongsi station of Beijing metro line 12,which employs eight guiding tunnels.A two-dimensional numerical analy-sis model is established to optimize construction plans by analyzing ground settlement and crown subsidence under var-ious conditions,including different initial support thicknesses,reinforcement schemes,and excavation sequences.The findings indicate that ground settlement is maximized during the guiding tunnel excavation phase.The lateral impact range of the station construction is approximately 2.5 times the station width.The maximum ground settlement shows an exponential decay relationship with the initial support thickness of the guiding tunnels.Additionally,reinforcement at the top of the guiding tunnels contributes more significantly to ground settlement improvement than reinforcement at the crown.Changes in initial support thickness and reinforcement are particularly effective in improving ground settle-ment within a range of one station width.The optimal excavation sequence for the guiding tunnels is to first excavate the two central tunnels,followed by the side tunnels.The effect of changes in initial support thickness on controlling crown subsidence is more effective for the central tunnels than for the side tunnels,while controlling the subsidence of the upper guiding tunnel is primarily dependent on reinforcement at the tops of the side tunnels.The conclusions drawn from this study can serve as valuable references for engineering design and planning under similar conditions.
subway station with eight-drift by PBA methodthickness of primary liningdrift-top reinforcement
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