深季节冻土区路桥过渡段冻融变形机理与控制研究

Complex temperature distribution and different structure are important reasons for frozen disease in embankment-bridge (culvert) transition in deep seasonal frost regions. The diseases of embankment-bridge (culvert) transition caused by frost heaving and thaw settlement seriously restrict and influence the development of the High-Speed and Heavy Haul Railway in cold regions. Depending on the existing monitoring section of embankment-bridge (culvert) transition, the method of combining field monitoring, laboratory test and theoretical analysis is tried. The temperature distribution of embankment-bridge (culvert) transition in deep seasonal frost regions is detailed researched, the discrepant frost heaving and thaw settlement mechanism of embankment-bridge (culvert) transition is studied, the key factors in restricting frost heaving and thaw settlement deformation is explored, the frost heave and thaw settlement rating standard for subgrade fillings is proposed, the moisture migration rule and frozen margin is discussed and studied in the course of freezing and thawing. The multi-factors fusion model for frost heave and thaw settlement is established in combination with model test, and the long-term deformation of embankment-bridge (culvert) transition is also forecasted. Based on above research results, the frost heaving and thaw settlement controlling method applied to embankment-bridge (culvert) transition in deep seasonal frost regions is raised. The research results have important sense to improve the quality of subgrade engineering design and construction and protect against cold damage, at the same time, it will also improve the frozen soil mechanics curriculum and frozen soil test technology.

温度分布情况复杂和结构迥异是深季节性冻土区路桥（涵）过渡段冻害问题突出的重要原因，由冻胀、融沉引起的过渡段病害问题严重影响和制约着冻土区高速、重载铁路的发展。依托已有的路桥（涵）过渡段监测断面，采用现场监测、室内试验与理论分析相结合的方法，分析深季节冻土区路桥（涵）过渡段的温度分布情况，重点研究过渡段差异性冻胀、融沉变形机理，探讨制约路桥（涵）过渡段冻胀融沉变形的关键因素，提出路基填料冻胀、融沉和冻胀力分级标准，研究土体冻结融化过程中的水分迁移规律和冻结缘的形成过程。结合室内模型试验，建立深季节冻土区铁路路基多源融合的冻胀融沉计算模型，并预测其长期变形。在上述研究成果的基础上，提出适用于深季节性冻土区路桥（涵）过渡段差异性冻胀、融沉控制方法。研究结果对提高深季节冻土区路基工程设计与施工质量、路基冻害防治具有重要意义，同时也进一步完善了冻土力学学科体系和冻土试验技术。

路桥过渡段差异冻融变形问题是制约冻土区高速铁路快速发展的关键和亟待解决的重要科学问题。依托哈齐高速铁路路桥过渡段的设计与施工，深入分析了冻土区路桥过渡段的温度场、变形场分布特征，初步得到了多因素耦合作用数值计算模型，探讨和分析了适用于冻土区高速铁路路桥过渡段的填料类型、结构形式，并结合工程实际提出了冻土区高速铁路路桥过渡段差异冻融变形控制措施。本项目主要取得了以下几点成果：①结合现场监测和室内试验，研制并开发了一系列与项目密切相关的测试试验装置，如高程基准桩、大直径试样冻胀测试装置和冻拔性能测试装置等；②分析监测数据发现，冻结深度不仅与环境温度有关，亦与路基填料的性质密切相关；③路桥过渡段与标准路基相比，具有冻深更大、阴阳坡现象更明显的特点，且温度边界复杂性和结构迥异是冻土区路桥过渡段冻害问题突出的关键控制因素；④基于数值模拟和理论分析，复合保温措施、以及适当增加桥台构筑物与路基填料接触面的倾斜角度可以有效地抑制路桥过渡段冻害发生发展；⑤采用冻胀率、抗压强度和压实度作为抗冻胀填料的控制指标，提出过渡段粗粒土填料的合理细粒含量为5%，并将经历6次冻融后力学指标作为工程设计参考值；⑥综合考虑冻胀率、抗压强度和渗透系数，对于非渗水性要求的路基，基床填料益选用细粒土含量3%、水泥掺量3%的级配碎石，而对于有渗水性要求的路基，基床填料益选用去除0.5mm以下颗粒、水泥掺量3%~5%的级配碎石；⑦水分迁移是路基填料冻胀发生发展的原驱动力，外界水源补给条件下的冻胀量是封闭条件下的1.3倍，因此做好路基防排水可有效抑制路基冻融变形量。这些研究结果对有利于进一步提升我国寒区高速铁路路基冻胀防控理论水平，为冻土区路基工程设计与施工、养护与维修提供必要的技术指导，同时也进一步完善了冻土力学学科体系和冻土试验技术。