间歇性循环荷载下路基细粒土填料永久变形特性及预测模型

Cumulative plastic deformation of subgrade fine-grained soil under intermittent cyclic loading and its prediction model

实际列车运营条件下相邻列车间存在一定的时间间隔,因此,列车对路基的长期作用由列车通过时的振动加载和无列车通过时的荷载间歇组成,即间歇性循环荷载。为探究路基在列车间歇性动荷载作用下的变形特性,开展了连续加载与间歇加载(单级、多级加载)的动三轴试验,研究了间歇加载下累积塑性应变的发展规律,并提出了相应的累积塑性应变预测模型。研究结果表明,间歇加载提高了试样抵抗荷载的能力、降低了累积塑性变形的发展;间歇加载下试样的累积塑性应变曲线呈"阶段式"增长,不同于连续加载下累积塑性应变曲线"平顺型"发展的特点;基于时间硬化方法对双曲线模型进行改进,并对间歇加载(单级、多级加载)下稳定型和临界型试样的累积塑性应变进行预测,取得了良好的预测效果。研究结果对于深入分析实际列车荷载作用下路基土体的变形特性和沉降预测具有一定的指导意义。

There is a time interval between adjacent trains in the railway line in service,thus the long-term loading of trains on the subgrade is composed of the vibrational loading when the train is passing and the intermittent loading when train passed away,namely the intermittent cyclic loading.A series of dynamic triaxial tests with continuous loading and intermittent loading(single-stage and multi-stage)was conducted to study the deformation of subgrade under the intermittent cyclic loading of trains.The cumulative plastic strain under intermittent loading was studied,and the prediction models were proposed.Results show that the resistance of the sample to cyclic loading was improved and the cumulative plastic strain was reduced due to the loading intermittence.The cumulative plastic strain showed"phased growth"under intermittent loading instead of the"smooth growth"under the continuous loading.Finally,the hyperbolic model based on the time-hardening approach could better predict the cumulative plastic strain of the stable and critical samples under intermittent loading.The research can provide guidance for further understanding of the deformation characteristics and settlement prediction of railway subgrade.