交通循环荷载下路基填料长期动力特性与道路力学经验设计方法研究

Road base is the crucial component in the road to bear the traffic load and transfer it downward. Large permanent deformation of the road base will occur subjected to the cyclic traffic loading and the raining fall, which will reduce the road performance and its service life. Thus, it is essential to understand the deterioration mechanism of the road base subjected to the coupling action of traffic loadings and the raining fall in order to improve the long-term performance of road in our country. This project plan to investigate the breakage and deformation mechanism of road base material through large-scale tri-axial test; the effects of dry-wet cycling of the road base on its breakage and deformation is also investigated. Through the large-scale model test, the rigidity of the road base and the deformation of each layer under traffic loading is examined at different humidity condition. Based on the experimental results, the elastic-plastic constitutive model is established with shakedown theory, and the long-term deformation of the road base is predicted with the aid of two-time scale. Finally, the Mechanistic-Empirical road design method which is adaptive to the climate and traffic volume in China is proposed. The proposed M-E road design method can meet the challenge proposed by the heavy traffic volume on the road as the cyclic effects of traffic loading can be considered with this road design model. The implementation of this project can promote the road design level as well as improve the long-term road performance in China.

路基为道路中承载和传递车辆荷载关键结构，在大次数车辆循环荷载、降雨等因素作用下易发生累积沉陷与刚度衰减而降低道路服役性能与年限。准确掌握交通循环荷载与降雨等环境效应耦合作用下路基刚度衰减与累积变形机理，探索新型道路设计方法是我国高速公路建设中亟待解决的难题。本项目拟通过大次数、低应变、变围压路基填料大三轴循环荷载试验，揭示交通荷载下路基填料破碎机理与累积应变发展规律，获得干湿循环效应对路基填料破碎与累积应变影响机制；通过大比尺模型试验，揭示不同湿化状态下路基整体刚度变化与各层累积变形发展规律。基于试验结果，建立路基填料循环安定理论本构模型，结合双时间尺度方法实现道路累积变形准确预测。在研究基础上，提出适应我国气候条件、交通流量并能考虑交通荷载循环效应道路力学经验设计方法，以应对交通运输新形势对道路传统经验设计方法的挑战。本项目对促进我国道路设计水平发展，提高道路服役性能具有重要意义

本项目针对大次数交通荷载、降雨等环境荷载作用下路基粗粒填料刚度弱化与过大变形问题，开展了循环荷载下非饱和路基填料大型三轴循环荷载试验研究。以路基粗粒填料为研究对象，利用GDS大型三轴试验系统，在交通荷载引起的真实动应力状态下对路基填料开展循环荷载试验，系统性地分析了不同荷载频率、循环应力比等对路基填料长期动力特性影响规律。对GDS大型三轴试验系统进行非饱和测试模块升级，分析了不同基质吸力下路基填料长期累积变形规律，揭示了路基填料干湿循环效应与最大基质吸力历史对其累积变形影响机理；发现路基填料累积变形随着基质吸力增加而显著降低，且路基累积变形随着最大历史基质吸力与干湿循环次数增加而显著降低。基于安定理论，提出了考虑基质吸力影响的大次数交通循环荷载路基累积变形模型，实现了路基长期累积变形的准确预测，并结合研究结果与上海-嘉兴-湖州高速公路、绍兴钱滨线等道路沉降监测数据，探索了与我国气候环境、交通流量等因素相适应的道路力学经验设计方法，研究表明该方法在我国道路设计中有良好的适用性。克服了我国现有经验性路基设计方法难以考虑交通荷载循环效应、难以大范围推广应用等难题，促进了我国道路路基的设计水平，对我国道路高速化、重载化和大流量趋势下道路服役性能的提升具有重要意义。项目研究取得系列研究成果，发表学术论文13篇，其中SCI论文8篇；申请发明专利2项，登记软件著作权2项。