盾构穿越富水砂层对高铁桥梁桩基变形规律的影响分析OA

When a shield tunnel traverses the pile foundation of the high-speed railway bridge at a close distance,the disturbance of the soil will cause the pile foundation to offset,posing a potential threat to the safe operation of the high-speed railway overhead.To explore the deformation rule of adjacent pile foundations caused by shield construction in a water-rich sand layer,based on the case of Zhengzhou Metro Line 12 underpassing the Beijing-Guangzhou High-speed Railway bridge,this paper first discusses the instability mechanism of the pile foundation under the thrust and dynamic action of the shield tunneling machine,and then establishes a tunnel-soil-pile foundation finite element model using Abaqus.The whole process of shield excavation of the double-line tunnel is simulated by the"birth-death element method",and the deviation of the pile foundation in different directions under the conditions of single-and double-line tunneling is analyzed based on construction monitoring data.The following conclusions are drawn:①In this construction case,the shield machine can safely pass through the construction area,and the deformation of the pile foundation is within the control range of national standards.②The thrust of the shield machine causes the pile body to shift toward the driving direction.When the shield machine reaches the pile foundation plane,the migration rate reaches its maximum,and then the rate decreases with displacement rebound.③The pile foundation is offset away from the tunnel by the lateral extrusion of the shield tunneling machine,and then offset back by the extrusion of the rear shield tunneling machine.Finally,the pile foundation is stable in the direction toward the rear tunnel.The maximum vertical displacement of the pile body occurs in the middle and upper parts,and the settlement of the lower part is the smallest due to the rebound from soil unloading.④The surface settlement curve for the single line is"V"shaped,and that for the double line is"W"shaped.The maximum settlement value occurs on the central axis of each tunnel,and the maximum settlement amount of the rear line is less than that of the advance line.After data comparison,the model results are well validated with the monitoring data.The research results of this study can provide theoretical basis and engineering references for the construction control,deformation analysis and safety guarantee of subway shield tunneling passing close to the bridge pile foundation of high-speed railway in areas with abundant water-bearing sand layers.