南方多雨地区重载铁路路基瞬态饱和区动孔压演化基础研究

The transient saturated zone at heave-haul railway subgrade has the properties of high risk for subgrade disease, extensive distribution, transient existence and extremely complicated hydro-solid coupling. The transient saturated zone is the key reason for mud pumping, which harms the durability of ballasted railway subgrade. It is urgent to take researches focusing on this key problem. The scope of this project includes the researches of dynamic pore pressure evolution due to heave-haul railway load, the modeling of hydro-solid coupling in transient saturated zone, and the numerical analysis of the hydro-solid coupling damage in subgrade. The aim of this project is to know the micro mechanism of mud pumping disease owing to the hydro-solid coupling in transient saturated zone. In addition, the quantified indexes are presented to reduce the risk of mud pumping disease in heave-haul railway subgrade located in southern rainy area. The laboratory works consist of the large-scale cyclic TX tests of subgrade fillings, the full-scale model tests of rain infiltration and the large-scale model tests of emigration of fines. The general works are as following: First, a theoretical method will be proposed to evaluate the depth of transient saturated zone and the developing rate of transient saturated zone. Secondly, the hydro-solid coupling in the transient saturated zone will be modeled using the basic theory of seepage and mechanics. And then, the accurate numerical- method will be developed based on the modeling works and be calibrated by the results of large-scale model tests. After that, the evolution procedure of dynamic pore pressure will be simulated and the critical hydraulic gradient for transient saturated zone will be set up. The evolution of dynamic pore pressure includes the developing procedure and the dissipation procedure during a passage of heave-haul train. The mechanism for the emigration of fines can be revealed through the numerical simulation of hydro-solid coupling. At last, the micro mechanism of mud pumping can be clearly known and the critical conditions for mud pumping can be quantified. The findings are expected to supply basic theory for the prevention of extensive occurring of pumping disease heave-haul railway subgrade in southern rainy area.

瞬态饱和区具有高危害性、分布广泛性、瞬态性(隐蔽性)和异常复杂性特点，它是多雨地区路基大面积冒浆的根源，严重损害重载铁路路基长期稳定，开展对此的深化研究已非常迫切。为此，本项目通过理论分析和模型试验，深入研究路基瞬态饱和区动态孔压演化规律与固-液耦合效应，揭示瞬态饱和区劣化机理，量化病害控制条件。具体为：进行路基瞬态饱和区深度计算理论研究，分析其形成与发展规律；基于多孔介质渗流场与应力场理论，建立瞬态饱和区的固-液耦合理论模型；开展路基瞬态饱和区精细化模型试验研究，验证和改进固-液耦合模型，并开发细观尺度数值模拟方法；分析大轴重列车加载挤压下瞬态饱和区孔压发展与卸载抽吸下的消散规律，提出临界水力梯度控制方程；分析孔隙水非平衡流动及细颗粒迁移规律，研究瞬态饱和区固-液耦合效应，明确病害机制和控制条件。预期成果为“多雨地区重载铁路路基大面积冒浆病害防控”提供理论支撑。

本项目结合我国铁路的基本情况，针对南方多雨地区重载铁路基床层冒浆病害频发的内因，围绕解决瞬态动孔压演化与固-液耦合效应的基本科学问题，采用综合现场调研、实验与理论分析相结合的方法开展研究。经过4年努力，完成了既定的研究目标情况。开展了铁路路基翻浆冒泥病害调查，进行了重载铁路路基瞬态饱和区形成与发展规律研究。掌握了列车激励下饱和基床层瞬态高孔压发展规律，揭示了瞬态饱和区动态高孔压演化机理；建立了路基基床层粗颗粒破碎演化预测模型，能够准确预测基床层细颗粒增量和应力应变发展规律，明确了重载铁路瞬态饱和区冒浆病害细颗粒物源；揭示了路基瞬态饱和区发展规律与冒浆病害宏细观机理，揭示了多雨地区重载铁路路基瞬态饱和区劣化机制，提出了应对技术措施。立足于“排、堵、注”一体化的设计理念，优化了路基瞬态饱和区冒浆病害快速修复工艺，部分研究成果在既有铁路线中得以应用。优化的路基瞬态饱和区冒浆病害快速修复工艺在既有铁路线中得以应用。“重载列车激励下红砂岩残积土基床瞬态饱和区动态水压力特征试验研究”与“重载铁路基床表层级配碎石的级配优化方法研究”成果有望在未来3-5年内通过铁路行业相关设计院平台实现成果转化。发表学术论文8篇，申请发明专利2 项；培养博士研究生2 名，培养硕士研究生4 名；依托本项目参加国际学术交流2 次，参加国内学术会议6 次，邀请1名国外专家赴华讲学。本课题部分研究成果为依托，获得2019年湖南省科学技术国际合作奖，申报了2020年中国交通学会科技进步一等奖。