既有线开行大轴重列车路基动力湿化变形机理及适应性研究

It has become a main trend that running heavy-axle load train in existing line. Subgrade diseases, however, frequently happens, which lead to not only increase of expenses for repair, but also decrease for the running safety. It is the coupling effect of dynamic load and wetting process which is the main reason for the beginning and development of subgrade diseases. As a result, it is very important for safety running to find the reaction mechanism between dynamic load and water seepage in addition to the assessment of existing line. In this project, the water distribution along triaxial sample is measured in time when dynamic triaxial tests is taking. By this way, the coupling process for dynamic load and water is investigated. From tests the main parameters which affect the dynamic wetting process are confirmed. Then, based on the theory of unsaturated theory, a dynamic and wetting coupled model and FEM program will be provided. By this model, the devolvement of diseases, such as mud-pumping, uneven settlement, can be investigated. It is also have benefits for design of repair method, assessment of subgrade and confirming the requirements for embankment. The achievements will offer important theoretical and technical support to run heavy-axle train on existing line.

既有线路开行大轴重列车是铁路发展的一个方向，然而,既有线设计标准低，频繁出现的路基病害不仅增加维护费用也影响行车安全。动应力与水的耦合作用是造成路基病害、恶化的最主要原因，揭示其相互作用机理、评估线路状况的适应性，对确保运营安全有重要意义。本项目采用实时测试动三轴实验中土样水分迁移规律，探索动应力与浸水的耦合作用过程，掌握变形控制参数特征；以非饱和多相介质理论为基础，提出动力-湿化变形模型及计算方法，对揭示轴重增加引起的翻浆冒泥、不均匀沉降等病害的产生规律，为制定合理的病害治理方法有着重要价值；对评价既有线路开行大轴重列车的适应性有重要意义，为我国既有线路重载化和路基强化技术提供理论和技术保障。

准确预测既有线路扩能改造后出现的路基病害对于加快了我国重载铁路建设的步伐，合理制定有效的治理措施有着重要价值。本项目按着计划书要求，由4位老师、8名研究生参与 ，并与国内外专家学者进行了广泛深入的学术交流，主要取得了如下四个方面的研究成果：（i）发现了基床动应力值受轨面平顺状态影响极为显著 ，轨缝处动应力约比平顺段高30%，因此病害段动变形与动应力存在较为明显的互相放大效应；（ii）基于梯形模型，提出了柱状土体电阻率分布影响线法，获得了动力三轴试验中水分迁移的精确测量方法，拓展了三轴试验的水力测试的新领域；（iii）基于试验与数值方法突破了传统vdP理论只能应用于片状体的局限，得到了vdP法在柱状体测试中的解析公式；（iv）进行了不同压实度、初始含水率土体在补水条件下的动力特性试验，发现动力湿化试验中进水量随着动应力幅值的增加而减小，前期动应力幅值越大，补水后水分越难浸入 试样内部，且浸入 试样内部的水分沿高度方向的迁移速率较慢，并形成水囊，由此可以做出翻浆冒泥也是一种“液化”的判断；（v）通过定义归一化塑性应变指数，提出了基于H-D模型的土体湿化骨干曲线模型，在修正Iwan模型基础上，提出了考虑湿化与循环荷载耦合作用的动力湿化模型，利用该模型可以很好地预测基床在动力湿化条件下的变形特性。研究成果建立了不同自然条件下线路服役状态评估及安全性预测理论体系，为预测重载列车动力荷载作用下基床土体变形，评价既有线路开行大轴重列车的适应性提供了参考。