多年冻土地区路基沉降变形的机理和时空演化规律研究

Settlement of embankments in permafrost regions extensively exists in highways. Due to involvement of several physical-mechanical processes, mechanism of the embankment settlement is very complicated and its temporal-spatial evolution rule is unclear, which is one of the big challenges to frozen soil mechanics and engineering. Based on a large amount of preparation work, this project will take the Qinghai-Tibetan Highway as study object. Mechanism and evolution rules on settlement of embankments in permafrost regions will be extensively investigated using in-situ monitoring, model test and numerical simulation. New in-situ monitoring sites will be set up, so as to form a serial multi-layered settlement observation system. Combining with model testing results, the mechanism of the settlement in embankments are investigated which covers the main physical-mechanical processes including thaw consolidation, creep of warm frozen layer and freeze-thaw induced settlement. Through element tests, constitutive models for related processes will be improved. Taking use of FLAC3D software for secondary development, a numerical platform for muti-process settlement will be developed. Numerical calculation is to be carried out on typical embankment sections in future time series. In-situ monitoring, model tests and numerical analysis are combined to reveal spatial and temporal evolution rules of embankment settlements under different geographical and geological conditions in permafrost regions. The study will provide scientific basis for construction and maintenance of roadway embankments in permafrost regions.

沉降变形广泛存在于多年冻土地区的路基工程中。由于涉及多个物理力学过程，路基沉降变形发生的机理复杂，时空演化规律尚不明确，是冻土力学与工程中至今没有解决的难题。本项目拟以青藏公路为研究对象，在大量前期工作的基础上，采用现场观测、室内大型模型试验和数值模拟相结合的方法，深入研究多年冻土地区路基沉降变形产生的机理和时空演化规律。在典型路段增设分层沉降观测点，形成系统的沉降变形现场观测体系，结合大型模型试验，揭示路基沉降变形的机理；基于室内小样品试验，发展沉降变形所涉及的融沉、高温冻土蠕变和冻融循环作用等物理力学过程的本构理论；利用FLAC3D软件进行二次开发，建立多元沉降数值分析平台；对沿线典型路基断面在不同运营时间下的沉降变形进行数值分析，以揭示不同地貌和工程地质条件下路基沉降变形的时空演化规律。研究成果将为多年冻土地区道路工程建设和维护提供科学依据。

沉降变形广泛存在于多年冻土地区的路基工程中。由于涉及多个物理力学过程，路基沉降变形发生的机理复杂，时空演化规律尚不明确，是冻土力学与工程中至今没有解决的难题。本项目以青藏公路为研究对象，在大量前期工作的基础上，采用现场观测、室内试验和数值模拟相结合的方法，深入研究多年冻土地区路基沉降变形产生的机理和时空演化规律。通过分析典型路段上布设的分层沉降观测点所获得的沉降变形，提出不同工程地质和地貌条件下四种典型沉降模式，即稳定低速型、波动型、阶梯型和稳定快速型。自主研发了冻土K0压缩仪、可进行孔隙水压力测量的融化固结仪、高级冻土三轴试验仪以及冻土平面应变仪。开展的试验和理论工作包括：进行了三种典型土的K0压缩，进一步从力学特性的角度确定了高温冻土的温度界限，并分析了不同冻土的压缩特性；进行了融化固结试验，研究了融化固结期间孔隙水压力分布和消散规律，验证非线性应力-应变关系在三维大变形融化固结理论中的适用性，并分析了影响融化固结行为的相关因素；利用三轴试验获得的试验数据，对冻土亚塑性模型进行了验证并数值化；在软土蠕变基础上考虑强度衰减提出了修正的率相关本构模型。基于室内小样品试验，发展沉降变形所涉及的融沉、高温冻土蠕变和冻融循环作用等物理力学过程的本构理论；利用修正的本构模型可直接进行沉降变形计算。研究成果将为多年冻土地区道路工程建设和维护提供科学依据。