The rapid growth in railway infrastructure and the construction of high-speed heavy-haul rail network, especially on ground that is basically unsuitable, poses challenges for geotechnical engineers because a large part of the money invested in the development of railway lines is often spent on track maintenance. In fact around the world, the mud pumping of subgrade fines is one of the common reasons why track performance deteriorates and track stability is hindered. This article presents a series of laboratory tests to examine following aspects of mud pumping: (1) the mechanisms of subgrade fluidisation under undrained condition, (2) the effects of mud pumping on the engineering characteristics of ballast, and (3) the use of vertical drains to stabilize subgrade under cyclic loads. The undrained cyclic triaxial testing on vulnerable soft subgrade was performed by varying the cyclic stress ratio (CSR) from 0.2 to 1.0 and the loading frequency f from 1.0 to 5.0 Hz. It is seen from the test results that for a specimen compacted at an initial dry density of 1790 kg/m³, the top portion of the specimen fluidises at CSR = 0.5, irrespective of the applied loading frequency. Under cyclic railway loading, the internal redistribution of water at the top of the subgrade layer softens the soil and also reduces its stiffness. In response to these problems, this paper explains how the inclusion of vertical drains in soft subgrade will help to prevent mud pumping by alleviating the build-up of excess pore pressures under moving train loads.

中文翻译：

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压载铁路轨道下路基流化的机理与影响

铁路基础设施的快速增长和高速重载铁路网的建设，特别是在根本不适合的地面上的建设，对岩土工程师提出了挑战，因为投资于铁路开发的大部分资金通常用于跟踪维护。实际上，在世界范围内，路基细粉的泥浆泵送是导致轨道性能下降和轨道稳定性受到阻碍的常见原因之一。本文介绍了一系列实验室测试，以检查泥浆泵送的以下几个方面：（1）在不排水条件下路基流化的机理；（2）泥浆泵送对压载物工程特性的影响；（3）使用垂直排水，以稳定循环荷载下的路基。f从1.0到5.0 Hz。从测试结果可以看出，对于以1790 kg / m ³的初始干密度压实的试样，试样的顶部在CSR = 0.5时发生流化，而与施加的加载频率无关。在循环铁路荷载作用下，路基层顶部的内部水分重新分配会软化土壤，并降低其刚度。针对这些问题，本文解释了在软土路基中包括垂直排水孔如何通过减轻列车在移动荷载作用下过大的孔隙压力的积累来帮助防止泥浆泵送。