基于不同本构模型的复杂地层大断面隧道开挖稳定性分析

多元结构地层中,土体单元触变性高,应力应变路径十分复杂,单一的本构模型不能满足隧道施工变形研究的需要。分析了摩尔库伦、修正剑桥、Druker-Prager和西原正夫等四种本构模型的屈服特性及应力应变关系,通过C++对FLAC软件二次开发,将本构模型程序化。以兰州轨道交通某大断面车站隧道为工程背景,模拟分析四种模型下大断面隧道开挖引起的地表沉降、底板隆起、两帮收剑的变化规律,发现摩尔库伦模型中洛德参数可识别土体单元处于压缩或拉伸状态,能较好地拟合地表沉降规律;修正剑桥模型可追踪岩土体的变形能力和抗剪强度随体积改变而变化的特性,能准确判断隧道直墙的水平位移变化趋势;Druker-Prager模型因考虑中间主应力及静水压力对相邻单元的作用,可反映出隧道内部土体移出后的底板隆起变形特点。以上规律可为复杂多元结构地层中隧道施工变形控制提供参考,从而保证隧道建设的高效与优质。

Stability of Large Section Tunnelling Based on Different Constitutive Models in Complex Stratum

In multi-component soil,thixotropy,high stress and strain path are very complex,single constitutive model can not calculate the deformation of the tunnel construction.In this paper,the yield behavior and stressstrain relationship of four constitutive models based on FLAC secondary development via C + + are analysed.Referring to a station construction in Lanzhou City on large cross-section tunnel,the constitutive models are simulated and compared,parameters in Mohr Coulomb model can identify the unit compression or tension state,describe the surface subsidence law;Modified Cambridge model can track the changes of ability and shear strength with the volumn of rock mass,accurately judge the horizontal displacement of straight wall of the tunnel.Druker Prager model,with full consideration of the intermediate principal stress and hydrostatic pressure,can reflect the upheaval of tunnel floor when the soil is removed.The above conclusion can provide guidance for the construction of tunnel and guarantee the efficiency and quality of tunnel construction.