湿化作用下现役路堤刚度和变形演变规律及调控方法研究

Because of the influence of climates, soils and other complex conditions, the moisture content in embankments in service changes with time and space remarkably in the southern region, which will obviously humidify embankments and lead to a decrease of stiffness and an increase of deformation. Currently, the study on the evolution law and control method of stiffness and deformation of embankments in service under the humidifying effect is still not completed well.The modified stress dependent pressure plate will be utilized to gain the soil-water characteristic curve of unsaturated soils considering the density variety, drying-wetting cycle and vertical loading. Then, the calculation method of the moisture content distribution in embankments will be put forward. Subsequently, the surface equivalent modulus of embankments according to the moisture dependent resilient modulus with a spatial non-uniform distribution in embankments will be built. Based on this, the permanent deformation considering the change with the variety of pavement structure, traffic loading and moisture content of the influence depth of the traffic loading in embankments was calculated. After that, the evolution of the surface equivalent modulus and permanent deformation of embankments will be revealed. Then, the working mechanism of the granular layer on embankments will be explored and its structure design method will be put forward. At the same time, a small accelerated loading test will be carried out according to related research contents. The research findings will be beneficial to know and control the rigidity and deformation of embankments, which have an important theoretical significance and engineering application value to predict the performance of embankments in service for the road maintenances decision and to improve the performances of old embankments.

由于受湿热气候及土质等复杂条件影响，南方地区现役路堤内部湿度状态随时间和空间的稳定性差，导致其湿化严重，刚度显著降低，变形持续增加。目前，国内外对湿化作用下现役路堤刚度和变形演变规律及调控方法的研究尚不深入。本项目拟采用改进的应力相关压力板仪，开展受密度和干湿循环影响的路堤土有荷条件下的土水特征曲线试验研究，建立路堤湿度计算方法；提出考虑路堤内各点回弹模量的湿度依赖性和空间非均匀分布特性的路堤顶面当量回弹模量计算方法，基于此建立考虑行车荷载在路堤内的影响深度随路面结构、荷载大小等变化的路堤永久变形预估方法，揭示湿化作用下路堤顶面当量回弹模量和永久变形演变规律；并阐明路堤顶面粒料层作用机理，提出其结构设计方法。同时，针对相关内容开展小型加速加载模型试验研究。成果可实现湿化作用下现役路堤刚度和变形的“可知和可控”，对道路养护决策的路堤性能预测和旧路堤性能改善具有重要理论意义和工程价值。

我国南方湿热地区路堤和大气的湿热交换导致其湿化严重，且在行车动荷载的反复作用下，刚度显著降低、变形持续增加，直接影响道路基础设施的持久稳定。为此，本项目针对湿化作用下现役路堤刚度和变形演变规律及调控方法开展研究。首先，改进了应力相关压力板仪，通过优选试样下方的透水石替代材料有效缩减了吸力平衡时间，开展了考虑干密度变化等的有荷条件下路堤土基质吸力试验，获取了复杂条件下路堤土的土水特征曲线预估模型与相关参数，以此为基础建立了路堤湿度计算方法，与实际工程的现场测试数据对比分析表明建立的路堤湿度计算方法合理准确。其次，建立了行车动荷载作用下路基路面力学响应模型，提出了恒定湿度条件下路堤内空间非均匀分布的回弹模量计算方法，并建立了随湿度变化而变化的路堤内空间非均匀分布的回弹模量计算方法，由此基于弯沉等效的原则提出并验证了路堤顶面当量回弹模量计算方法，进而揭示了湿化作用下路堤顶面当量回弹模量的演变规律，发现其随着湿度和交通荷载的增大而减小，且随着时间的推移而逐渐减小，并逐步达到一个相对的稳定值，且在此稳定值附近随气候环境的变化而小幅波动。接着，开展了考虑路堤内回弹模量空间非均匀分布特性的路堤动应力场数值计算，分析了不同路面结构、行车动荷载大小、路基湿度等条件下的路堤内动应力分布规律，确定了不同工况下动荷载在路堤内的影响深度，进而提出了路堤永久变形计算方法并揭示了其演变规律，结果显示路面结构的厚度变薄、行车动荷载增大以及路堤湿度升高均会导致路堤永久变形增大。最后，通过数值计算方法，建立了粒料层厚度、粒料层材料模量、路堤模量等各因素与粒料层顶面当量回弹模量之间的相关关系，提出了粒料层结构设计方法。成果实现了南方湿热地区湿化作用下现役路堤刚度和变形的“可知和可控”，从而提高了道路养护决策时现役路堤性能预测水平并改善了旧路堤性能，并最终可提高道路基础设施的使用寿命。