排水桩加固及动力荷载强度对可液化地层中盾构隧道动力响应的影响

Influence of Drainage Pile Reinforcement and Dynamics Load Intensity on Dynamics Response of Shield Tunnelling in Liquefiable Stratum

目的:隧道工程作为大型地下结构工程之一,穿越可液化地层时面临着较大的液化破坏风险。对此,需分析排水桩加固及动力荷载强度对可液化地层中盾构隧道动力响应的影响。方法:建立了可液化土层中液化动力响应的数值分析模型,并通过实际工程案例验证了该模型的有效性。依托上海市轨道交通崇明线工程,应用该模型进行液化场地加固动力响应分析,评价了液化场地采用排水桩加固措施的效果和加固作用范围,分析了不同动力荷载强度下隧道穿越可液化地层的动力响应。结果及结论:Plaxis2D软件中的UBC3D-PLM本构模型可有效模拟可液化地层中的孔压动力响应;在一定范围内隧道两侧的排水桩可有效抑制动荷载作用下可液化土层液化的发生;动力荷载强度主要对超孔压积累和增长模式产生有影响;当动力荷载加速度峰值达到0.2 g(g为重力加速度)后,可液化土层超孔压比累积增长规律基本一致,均在振动初期达到完全液化,并且超孔压随着振动荷载作用时间的增加而趋于稳定。

Objective:As one of the large underground structure projects,tunnel engineering faces a significant liquefaction damage risk when crossing liquefiable stratum.Targeting this issue,it is necessary to analyze the influence of drainage pile reinforcement and dynamics load intensity on dynamics response of shield tunnelling in liquefiable stratum.Method:A numerical analysis model of liquefaction dynamics response in liquefiable stratum is established,and the effectiveness of the model is validated through an actual engineering case.Based on Shanghai Rail Transit Chongming Line project,the model is applied to analyze the dynamics response of liquefaction site reinforcement,evaluate the effect and scope of drainage pile reinforcement measures for liquefaction site,and analyze the dynamics response of tunnel crossing liquefiable stratum under different dynamics load intensities.Result&Conclusion:The UBC3D-PLM constitutive model in Plaxis2D software can effectively simulate the pore pressure dynamics response in liquefiable stratum.The drainage piles on both sides of the tunnel can effectively suppress the liquefaction in liquefiable soil stratum within a certain range for under dynamics load action.The dynamics load intensity mainly affects the accumulation and growth pattern of excess pore pressure.When dynamics load peak acceleration reaches 0.2 g(where g is the gravitational acceleration),the excess pore pressure accumulation growth pattern of liquefiable stratum is basically consistent,arriving at complete liquefaction at the initial vibration stage,and the excess pore pressure tends to stabilize with the increase of vibration load action time.