渗水膨胀岩隧洞黏弹塑性蠕变解及变形特性分析

Viscoelastic-plastic creep solutions and deformation properties of tunnels in swelling rocks under seepage

渗水膨胀岩隧洞变形是一个受渗流、膨胀与扩容等多因素影响的复杂时变问题。探讨了其变形机制,建立渗水膨胀围岩受力平衡方程,进而得到反映扩容角影响的弹塑性解,并证明余东明解和侯公羽解是本文解的两个特例。以此为基础,借助改进的西原模型,获得了考虑膨胀应变影响的渗水膨胀岩隧洞黏弹塑性蠕变解,并分析了渗流、膨胀与扩容等因素对洞壁时效变形的影响规律。结果表明:随着内外水头比减小或扩容角增大,时效变形逐渐表现为黏弹塑性;膨胀系数α2只影响围岩黏弹性变形,位移为α2的单调递增线性函数;在隧洞开挖扰动初期,封闭应变迅速发展成位移,对渗水膨胀围岩变形影响极大。所得结论对渗水膨胀岩隧洞施工和变形控制具有一定指导意义。

With the effects of many parameters,such as seepage,swelling and dilatation,the deformation of tunnels in swelling rocks under seepage is a complex time-dependent problem.The closed strain hypothesis is proposed.The equilibrium equation for the tunnels in swelling rocks under seepage is established.And then the elastoplastic solutions considering the effect of dilatancy angle are obtained.The answers of Yu dongming's and Hou gongyu's are the two special cases of the solutions.Accordingly,the viscoelastic-plastic creep solutions of the tunnels in swelling rocks under seepage considering the effect of swelling strain are obtained by using the modified Nishihara model.The influence of the related parameters on the time-dependent deformation of tunnel wall is analyzed,such as inflation,seepage and expansion.The results show that the time-dependent deformation presents viscoelastic-plasticity gradually with the decrease of the ratio of inner to outer water heads or the increase of the dilatancy angle.The moisture expansion coefficient α2 affects only the viscoelastic deformation of the surrounding rock,and the displacement monotonically linearly increases with it.At the early stage of excavation,the closed strain develops rapidly into displacement,which greatly influences the deformation of swelling rocks under seepage.The results can be taken as a guide for the construction and deformation control of the tunnels in swelling rocks.