动荷载下软土路基变形规律研究

Study on the Deformation Behavior of Soft Soil Subgrade under Dynamic Load

研究目的:为研究列车循环荷载下的路基变形特性,找出路基中土的动力特性。本文首先介绍了胶新线试验段的基本情况,从理论上分析计算了路基沉降与时间的关系,给出了路基计算模型与路基土本构方程。进而通过研究列车动荷载下的路基弹性变形与塑性变形特性,得到路基动应力衰减曲线。研究结论:(1)实际中应变波是在有限深度内传播的,一般在路基面以下5 m弹性变形很小。弹性动应变所占比例很小,不足0.06%,而且随着深度逐渐减小,所以弹性动应变对松软土路基工后沉降的贡献很小;(2)在动载试验150万次后,测得路基的塑性变形值为:级配碎石基床表层塑性变形为27.35 mm,松软土地基塑性变形为2.67 mm。动荷载对工后沉降的贡献主要体现在路基基床部分,工后沉降在列车运行1年后趋于稳定。

Research purposes：To study the subgrade deformation characteristics under cyclic loading and identify the dynamic characteristics of embankment,the basic conditions of the test section of the Jiaozhou-Xinyi Railway are introduced in this paper.A theoretical analysis of the relationship between subgrade settlement and time is made and the model for calculation of the subgrade and equation for soil constitutive are given.Through studying the elastic and plastic deformation characteristics of the subgrade under dynamic load,the decay curve of the subgrade dynamic stress is obtained. Research conclusions：（1） The practical strain wave propagates within limited depth and its elastic deformation is generally small under 5m of the subgrade.The proportion of the elastic dynamic strain is small with less than 0.06% and it decreases with increase of the depth,so the elastic dynamic strain makes little impact on the post-construction settlement of the soft soil subgrade.（2） After doing the dynamic tests of 1.5 million times,the subgrade plastic deformation values are as follows：the plastic deformation of graded crushed stone subgrade is 27.35mm and the loose soft plastic deformation is 2.67mm.The impact of the dynamic load on post-construction settlement mainly reflects in bedding,and the post-construction settlement is stable after 1 year.