The problem of subgrade mud pumping under the action of train loads is common and challenging to cure. In order to investigate the occurrence condition and the mechanism underlying the development of mud pumping, the characteristics of 23 groups of soils prone to mud pumping were analyzed. Moreover, findings indicate that most of the soils have the following characteristics: (1) clay content is greater than 2%, and silt content is greater than 20%; (2) the liquid limit ranges between 23 and 75%, and the plasticity index varies between 5 and 42.5; (3) the permeability coefficient is between 3.28 x 10-8 cm/s and 1.39 x 10-4 cm/s; (4) the main mineral components of the mud pumping soils are illite, montmorillonite, and kaolinite; and (5) the saturation of the mud pumping soil is generally greater than 80%. In addition, silty clay was selected to carry out the subgrade mud pumping test. The results show that under cyclic loading, there is an excess pore water pressure gradient in the subgrade soil, which mobilizes the fine particles in the subgrade soil, especially in the upper part of the subgrade soil, to migrate with the water flow, forming mud, and eventually resulting in subgrade mud pumping.

来源平台：INDIAN GEOTECHNICAL JOURNAL