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采用理论分析结合现场实测数据,以黄河厚冲积层地质条件下某深大基坑开挖为实例,利用修正剑桥、西原正夫及改进的西原正夫等5种本构模型,通过FLAC仿真软件构建3D数值模型,分析基坑开挖引起的围护桩变形规律、墙后土体沉降变化特征、坑底土体上移趋势及抗浮桩侧摩阻力分布特点。结果表明:西原正夫本构模型可描述粘土体的蠕变变形,能准确追踪围护桩侧向位移;修正剑桥模型通过自动调整自身抗剪强度和弹性模量等参数,可给出墙后土体沉降的正确规律;摩尔库伦模型拟合得到的坑底土体上移曲线与现场实测数据较吻合;在改进的西原正夫及修正剑桥模型下,计算得到的抗浮桩侧摩阻力最为保守。上述规律可供预测基坑后续运营期间的结构变形、延长结构的服役年限参考。
Based on the theoretical analysis and field measurements, taking a deep foundation pit excavation under the condition of thick alluvium in the Yellow River as an example, five constitutive models, namely modified Cambridge, Nishihara Masaharu and improved Hideki Nishihara, were constructed by using FLAC simulation software Numerical model is used to analyze the deformation of retaining piles caused by excavation, the characteristics of subsidence changes of soil behind piles, the tendency of soil moving upward in pits and the distribution of lateral frictional resistance of anti-floating piles. The results show that the Xiyuanzhengfu constitutive model can describe the creep deformation of clay body and can accurately track the lateral displacement of the retaining pile. The modified Cambridge model can automatically adjust the self-shear strength and elastic modulus of the clay wall The correct law of body subsidence is obtained. The up-curve of the soil at the bottom of the pit fitted by the Mohr-Coulomb model is in good agreement with the measured data. Under the improved Nishihara-Masaharu and modified Cambridge model, the calculated frictional resistance of the anti-floating pile is the most conservative. The above rules can be used to predict the structural deformation during the subsequent operation of the foundation pit and extend the service life of the structure.