中文摘要：

采用粘弹塑（西原）本构关系模拟土骨架的材料非线性、更新的拉格朗日法描述软土的几何非线性，推导用于增量分析的饱和土体双重非线性U．L.J．格式平衡方程和连续性方程，编制软土路基大型实用化有限元分析程序，利用该程序对某高速公路的实测断面分别进行大应变、小应变分析。数值模拟结果和现场实测结果的对比分析表明：大、小应变分析结果的差异随应力水平的提高和时间的延长而上升，其地表沉降、地基沉降、水平位移、孔隙水压力的最大相对误差分别为16．39％，20．23％，27．8％和22．75％，说明对软土路基进行大应变分析很有必要；采用室内试验确定的计算参数进行分析时，计算结果虽能较好地模拟地基应力和位移的发展趋势，但其值有较大差别，说明必须寻求更加合理的计算参数确定方法以提高数值模拟精度。

英文摘要：

The visco-elastic-plastic constitutive relation was employed to simulate the material non-linear of soil skeleton and the update lagrangian formulation was chosen to describe the geometry non-linear of soft soil. The continuity equation and double non-linear equilibrium equation of U.L.J. form for increment analysis of saturated soil were derived. The large-scale practical finite element analysis program was developed. The comparison analysis between large strain and small strain for a practical monitoring project on expressway was performed using this program. The analysis results were compared with the monitoring data. The results show that the difference of calculation results between large strain and small strain increases with the increase of stress level and time, the maximums of fractional error are 16.39% for settlement on the ground surface and 20.23% under the surface 3.8m, 27.8% for horizontal deformation and 22.75% for pore water pressure, which show that the large strain analysis is indispensable for soft soil subgrade. When the calculating parameters determined by the laboratory test are adopted, though the developing trends of deformation and stress of subgrade are described well by FEM analysis, the differences between the calculating value and tested data are too large to be accepted, which shows that seeking for more rational methods to determine the calculating parameters is essential to improve the precision of numerical analysis.