软土路基大应变黏弹塑性正/反分析沉降预测对比

Comparison of settlement prediction from back analysis with forward analysis for embankment on soft soil foundation based on large strain and visco-elastoplastic model

结合软土变形的大位移、大应变、渗透固结及依时性特点,采用黏弹塑(西原)模型模拟土骨架,建立了分析软土地基的大应变黏弹塑性有限元列式和迭代求解算法,并采用动态"生""死"单元模拟路堤的施工过程,建立了软土路基双重非线性渗透固结分析模型,研制了相应的大型实用化有限元分析程序LSVEP。分别采用反分析所得参数和室内试验确定参数对路基地表沉降和地基深层沉降进行预测,并将所得结果和现场实测结果进行对比分析,结果表明:所建立的大应变黏弹塑性有限元分析方法正确;计算参数的准确选择对沉降预测精度影响很大;用反分析所得参数进行沉降预测的精度远高于正分析预测,是提高沉降预测精度的有效途径,可供类似工程借鉴。

Taking the deformation characteristics of large displacement,large strain,permeability-consolidation and time-dependence of soft soil into account,the finite element method（FEM） formulas and iterative solution strategy were built,in which the soil skeleton was simulated by visco-elastic-plastic model.The embankment construction process was simulated by dynamic ＂birth＂ and ＂dead＂ elements and the double nonlinear permeability-consolidation analysis method was established.Then the FEM program LSVEP was developed.The foundation settlement was predicted by using parameters from laboratory tests and back analysis separately;and the results were compared with monitored data.The results indicate that： the large strain visco-elastoplastic FEM built in this paper is reasonable and the precision of settlement prediction was affected markedly by the choosing correctly of calculating parameters.The settlement predicted by parameters from back analysis is much more close to those monitored settlements,it is an effective method to improve the precision of settlement prediction and can be referenced by similar projects.