海底圆形隧道在渗流场影响下的弹塑性解

ELASTIC-PLASTIC SOLUTION FOR SUBSEA CIRCULAR TUNNEL UNDER THE INFLUENCE OF SEEPAGE FIELD

  • 摘要: 海底隧道不同于陆地上的一般山岭隧道,很高的孔隙水压力会降低隧道围岩的有效应力,造成较低的成拱作用和地层的稳定性。将具有衬砌的海底圆形隧道的各影响因素简化为轴对称,并把渗流场以渗流体积力方式作用于应力场,计算得到了弹塑性界面分别位于衬砌内部和岩体内部两种情况下,海底圆形隧道在渗流场影响下的弹塑性位移和应力解析表达式。通过实例计算,分析了渗流场作用下,海水深度和覆岩厚度对隧道应力场的影响规律。径向应力和切向应力均在弹塑性界面处达到最大值,且切向应力在衬砌与岩体的接触面以及弹塑性界面处均会出现跳跃。无论弹塑性界面位于岩体内还是衬砌内,海水深度的变化对衬砌与岩体接触界面上的法向接触压力影响很小。当隧道结构和覆岩厚度一定,弹塑性界面位于衬砌内部时,海水深度的变化对塑性区的扩展以及弹塑性界面上法向接触压力的变化影响不大,而当塑性区扩展到岩体内部时,塑性区半径以及弹塑性界面上法向接触压力与海水深度的增加大致呈线性关系,增长较快。

     

    Abstract: Subsea tunnels are different from the overground mountain tunnels. Due to the high seepage pressure, the effective stress of wall rocks would be reduced, which results in lower stratum stability. In this paper, the subsea circular tunnel with liner is simplified as axially symmetrical and the effect of seepage field is simplified as seepage volume force acting on the stress fields. Elastic-plastic analytical solutions of stress and displacement are obtained respectively for two cases: the elastic-plastic interface locates in the liner or in the surrounding rock. Based on the results of a practical example, the effects of sea depth and rock cover thickness on the stress fields are analyzed with the consideration of seepage fields. Some conclusions are as follows: 1) The maximum radial stress and tangent stress occur at the elastic-plastic interface. 2) No matter the elastic-plastic interface locates in the liner or in the rock, sea depth variations have little influence on the normal contact pressure at the liner-rock interface. 3) For a tunnel structure with determinate rock cover thickness, if the elastic-plastic interface locates in the liner, sea depth variations have little influence on the radius of the plastic region and on the normal contact pressure at the elastic-plastic interface. But, if the plastic region expands into the rock, the plastic region expands linearly and the radial stress at the elastic-plastic interface increases linearly as the sea depth increases.

     

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