高速铁路软土地基动力软化的微观机理及其对地基长期沉降的影响研究

The settlement of high-speed railway foundation is a serious threat to the safety of train operation. However, due to the absence of the clear understanding on micro-mechanism of the dynamic softening of the soft soil, the theoretical predictions of long-term settlement of the foundation significantly deviate from the practical measurement. This project aims to reveal the micro-mechanism of dynamic softening of soft soil and its influence on the long-term settlement of the foundation through theoretical study, model test and numerical analysis. Based on the assumption of statistical distribution of the bond and contact strength between the soft soil grains, a mathematical model for soft soil dynamic softening is proposed to analyze the key factors to affect the softening of soft soil. Consider the softening, nonlinearity and size effect of the soft soil, a nonlocal-strain-gradient Biot theory is proposed. The computing model for the consolidation settlement and dynamic responses of high-speed railway foundation under cyclic load generated by the train is constructed. The numerical analysis on the consolidation settlement and dynamic responses of the foundation is developed to reveal the development of the foundation long-term settlement, on which the evaluation system for settlement of the high-speed railway foundation can be improved. The research results from this project can provide necessary scientific basis and support for the prediction and control design of foundation settlement of the high-speed railway.

高速铁路轨下软土地基沉降是列车安全运营的严重威胁，而目前由于缺乏对软土动力软化微观机理的清晰认识，地基长期沉降的理论预测与实际情况出入较大。本项目拟通过理论研究、模型试验、数值分析等手段，针对高速铁路软土地基动力软化的微观机理及其对地基长期沉降的影响展开如下研究：提出软土颗粒间连接强度具有统计分布的假设，建立软土动力软化的数学模型，分析影响软土软化的关键因素；综合考虑软土的软化特性、非线性及颗粒尺寸效应，构建非局部-应变梯度Biot本构模型，提出软土地基在高速列车循环载荷作用下的固结沉降和动力响应的计算模型；开展地基固结沉降和动力响应的数值分析，揭示循环载荷作用下地基的长期沉降规律，完善高速铁路地基沉降的评价体系。本项目的研究成果可为高速铁路地基沉降预测和控制设计提供必要的科学依据和支撑。

本项目运用理论和数值计算相结合的方法，通过理论研究、模型试验、数值分析等手段，针对高速铁路软土地基动力软化的微观机理及其对地基长期沉降的影响展开如下研究：提出了软土颗粒间连接强度具有统计分布的假设，建立了软土动力软化的数学模型，分析了影响软土软化的关键因素；综合考虑软土的软化特性、非线性及颗粒尺寸效应，构建了非局部-应变梯度Biot本构模型，提出了软土地基在高速列车循环载荷作用下的固结沉降和动力响应的计算模型；开展了地基固结沉降和动力响应的数值分析，揭示了地基沉降规律，完善高速铁路地基沉降的评价体系。本项目的研究成果可为高速铁路地基沉降预测和控制设计提供必要的科学依据和支撑。