盾构埋深对软土土拱效应影响分析

软土盾构深埋隧道竖向荷载的选取直接关系到工程的经济性与安全性。在软土地层的盾构隧道设计是否需要考虑土拱效应,关系到盾构设计的荷载取值。从应力场变化和不均匀变形的角度,分析土压力拱的作用机理,得到管-土刚度埋深对"土拱效应"的影响。软土中盾构隧道埋深越大,拱效应发挥越充分,但土拱效应比例值与埋深并非线性关系。盾构在软土2倍直径埋深及以下深部地层中开挖,土拱效应开始发挥作用。当埋深达4D时,拱效应发挥至23%。埋深范围与软土拱效应比例的对应,对软土隧道竖向荷载的取值有一定指导意义,可为后期软土不同埋深的盾构设计提供依据。

Analysis on the Influence of Shield Depth on Soft Soil Arching Effect

The economy and safety of project is directly related to the vertical load of shield tunnel in soft soil.In the design of shield tunnel in soft soil,the soil arching effect is related to the load of shield design.From the point of the variation of stress field and the non-uniform deformation,the action mechanism of the soil pressure arch is analyzed.The influence of the depth on the soil arching effect was obtained.The bigger the buried depth of the shield tunnel in soft soil is,the more effective the arch effect is.During the unloading process of deep soft soil stratum,the displacement of the soil makes the soil particle density of the soil arch boundary increase.But the relationship between the proportion of soil arching effect and the depth of tunnel is nonlinear.The soil arching effect is playing a role when the excavation of the shield in the depth of 2 times diameter or deeper area in soft soil.The soil arching effect can reach 23％ when the depth reaches 4D.The research focuses on relationship between the depth of embedment and the proportion of soft soil arching effect,which has a certain significance value in vertical load for soft soil tunnel.