往复交通荷载下非饱和路基长期服役性能理论与试验研究

The roadbed is usually in the unsaturated state as it is built above the groundwater level. Field tests show that the matrix suction in the subbase and subgrade layer can reach as high as 100 kPa, which has significant effects on the dynamic properties of the road. Thus, deep understanding of the mechanism of resilient deformation and cumulative deformation of the unsaturated roadbed filling is the premise of the accurate prediction of the long-term road performance. The effect of water content on the resilient modulus and cumulative deformation of unsaturated roadbed is revealed by the cyclic loading test of the coarse road fillings with the unsaturated tri-axial apparatus. The effects of the complex water content history on the water retention characteristics and the long-term performance of the roadbed are identified. Furthermore, the coupling effects of the fine content and the water content on the resilient deformation and the cumulative deformation of the roadbed will be investigated. The overall stiffness and cumulative deformation of the road base under the wetting-drying cycles and traffic loading is studied through the model test. Based on the experimental results of unsaturated roadbed fillings, the constitutive model of unsaturated roadbed under cyclic traffic loading is proposed and the explicit method to calculate the cumulative deformation is developed. Then, the accumulated deformation of the unsaturated roadbed can be accurately predicted. This study is of great significance to promote the research in long-term characteristics of unsaturated roadbed and improve the performance of the road in China.

道路路基因建于地下水位之上而常处于非饱和状态，现场测试表明路基底基层与填方路基中基质吸力往往高达100 kPa，进而显著改变路基动力特性。正确认识往复交通荷载下不同含水率下路基回弹与累积变形机理，是准确预测路基长期服役性能的关键。本项目拟通过非饱和大三轴试验系统对路基粗粒填料进行循环荷载试验研究，揭示不同含水率下非饱和路基回弹变形与累积变形特性；分析复杂基质吸力历史对路基持水特性及长期动力特性的影响；揭示细粒土在不同含水率下对非饱和路基动力特性影响机理。结合模型槽试验，研究干湿循环与交通荷载耦合作用下路基整体刚度与累积变形规律。基于非饱和土路基试验结果，提出非饱和路基循环安定本构模型与累积变形显式计算方法，实现交通循环荷载下非饱和路基累积变形准确预测。本研究将促进路基动力特性分析理论与分析方法发展，对提高我国道路服役性能具有重要价值。

本项目针对交通荷载下非饱和路基服役性能劣化以及细粒侵入引起的路基填料持水特性与动力特性变化，本项目自主研发了大型土体持水特性测试仪，实现对路基粗细粒混填料土水特性测试；并通过对GDS大型三轴仪进行非饱和测试模块升级，实现了路基填料大型三轴试验中基质吸力的精准控制。开展了不同基质吸力幅值、复杂基质吸力历史、不同细粒含量下非饱和路基回弹与累积变形特性研究。研究发现非饱和情况下路基填料回弹模量随基质吸力增加而增加，累积变形随着基质吸力增加而显著降低。路基持水性随着细粒含量的增加而显著增加，土水特征曲线（SWCC）由单峰模式转变为双峰模式。路基细颗粒含量对非饱和路基长期累积变形的影响随土体内部结构变化而变化。基于安定理论与巴塞罗那非饱和土基本模型（BBM）框架，建立了大次数循环荷载下非饱和路基累积应变模型，提出了非饱和路基累积变形显式计算方法.本项目研究揭示了交通荷载下非饱和路基的回弹与累积变形特性，并提出了非饱和状态下路基累积变形显式计算方法，所提出的非饱和路基累积变形预测方法可用于非饱和状态下路基长期累积变形预测。目前已在杭州地铁10线车辆段等道路沉降分析中取得应用，对促进我国道路路基设计水平发展，提升道路服役性能具有重要意义。项目研究发表学术论文19篇，授权发明专利4项，登记软件著作权1项，本项目部分研究成果获浙江省科技进步二等奖1项。