加固厚度对软土地层大直径盾构隧道抗浮的影响

Influence of Reinforcement Thickness on Anti-floating of Large-diameter Shield Tunnel in Soft Soil Stratum

为研究软土地层隧道工程中软土地基的加固厚度对隧道上浮量的影响,以珠海市横琴杧洲隧道为依托,采用小应变硬化模型(HSS模型)作为软土本构模型,在PLAXIS 3D软件中建立了软土地层大直径盾构隧道的有限元模型,计算并对比了不同环形加固厚度下的隧道上浮量、河底土体位移和隧道周围土体的受扰动范围。结果表明:未对软土进行加固时,数值模拟得到的土体位移与二维理论推导的结果吻合较好;软基地层预加固处理能使加固土体与隧道整体抗浮,有效抑制隧道局部的上浮变形;软土加固厚度为0.10D(D为隧道外径)时,河底上浮量和隧道上浮量分别比未加固时减小了32.8%和36.4%,隧道上浮量和地层受扰动区域随加固厚度增加逐渐减小;该工程中隧道环形加固厚度大于0.20D时,计算得到的管片上浮量控制在30 mm以内,河底最大上浮量控制在20 mm以内;根据管片接头错台量和隧道上浮量的关系得到可控制管片接头偏差在5 mm以内,满足规范中管片拼装和验收时接头允许偏差量的要求。

In order to study the influence of the reinforcement thickness of the soft soil foundation on the up-floating amount of the tunnel lining in soft soil stratum,a hardening small strain model(HSS Model)was selected as the constitutive model,and a finite element model of large-diameter shield tunnel was established by PLAXIS 3 D software according to the Mangzhou tunnel project in Hengqin.The up-floating amount of the tunnel,the displacement of the soil at the river bottom,and the disturbed soil range around the tunnel were calculated and compared considering different reinforcement thicknesses.The results show that when the soft soil is not reinforced,the soil displacements from the numerical simulation are in good agreement with the two-dimensional analytical solution.Through the pre-reinforcement treatment of the soft soil,the reinforced soil and the tunnel lining work together to restrain the local tunnel floating.When the soft soil reinforcement thickness is 0.10D(D is the tunnel outer diameter),the vertical displacement of the soil at the river bottom and the floating amount of the tunnel lining is reduced by 32.8%and 36.4%respectively.With the increase of the reinforcement thickness,the floating amount of the tunnel and the area of the disturbed soil decrease gradually.For this project,when the reinforcement thickness is greater than 0.20D,the calculated maximum floating displacement of the tunnel lining is controlled within 30 mm,and the maximum vertical displacement of the soil at the river bottom is controlled within 20 mm.According to the relationship between the dislocation amount of lining joints and the floating amount of tunnel,the dislocation of lining joints can be controlled within 5 mm,meeting the requirements of the design standard.