红层软岩地区高速铁路深路堑基底变形规律研究

挖方高边坡基底随时间持续上拱变形如果超出铁路路基设计规范的限值,会严重影响列车的舒适性和安全性。为研究西南地区泥岩夹砂岩挖方高边坡基底持续上拱变形机理,使用FLAC3D软件对挖方高边坡进行弹塑性和黏弹塑性数值计算,并尝试从软岩流变的角度分析挖方高边坡施工完后基底持续上拱变形的规律。研究结果表明:在不考虑流变的弹塑性分析中,挖方高边坡具有明显的边坡开挖效应(卸荷效应),竖向应力随着边坡开挖深度的增加而减小,导致竖向变形逐渐增大,应力变化越大竖向变形也越大;在流变分析中,由于开始阶段的岩体应力调整,基底下一定深度出现竖向压缩变形,随着应力稳定,发生持续上拱非线性变形,并在5年后达到稳定;在流变计算中,由于基底下剪应力与水平应力均有所大幅度增加,基底下各深度的竖向变形小于弹塑性计算的变形,采用泥岩流变计算模型能较好的模拟并解释依托工程案例中挖方路基持续上拱变形现象。

Study on deformation law of deep foundation of high speed railway in red layer soft rock area

The comfort and safety of the high-speed railway will be seriously affected if the upper arch deformation of excavated high slope subgrade over time exceeds the limit of railway subgrade design code.In order to study the mechanism of the continuous upper arch deformation of the excavated high slope subgrade in mudstone sandwiched with sandstone in the southeast area,FLAC3D software was used to carry out the elastic-plastic and viscoelastic plasticity numerical calculation for the excavated high slope.It also tried to analyze the law of the continuous upper arch deformation of the subgrade after the construction of the excavated highslope from the perspective of the soft rock rheology.The results are as follows.In the elastic-plastic analysis without considering the rheology,the excavated high slope has an obvious slope excavation effect(unloading effect).The vertical stress decreases with the increase of the depth of the slope excavation,leading to the gradual increase of the vertical deformation.The greater the stress variation,the greater the vertical deformation.In the rheological analysis,due to the initial stress adjustment of the rock mass,the vertical compression deformation occurs at a certain depth under the subgrade.With the stabilizing of the stress,the continuous nonlinear deformation of upper arch occurs,which will reach a stability in 5 years.In the rheological calculation,since the shear stress and the horizontal stress have a great increase under the subgrade,the vertical deformation of each depth is less than the elastic-plastic deformation.The mudstone rheological calculation model can well stimulate and explain the continuous arch deformation of the excavated subgrade in this engineering case.