Experimental study on mud pumping mechanism and dynamic characteristics of ballasted track subgrade under intermittent load-wetting coupling

The mud pumping mechanism and dynamic characteristics of ballasted track subgrade under intermittent train load and rainfall wetting coupling are still unclear. A mud pumping model test in ballasted track subgrade under intermittent load-wetting coupling was conducted. The experimental results indicate that the cyclic loading has a promoting effect on the increase of volumetric water content and pore water pressure, and the promoting effect weakens with the increase of dry density. The accumulated deformation and particle migration mainly occur in the LS1-LS3 stages, and the changes are most significant in the LS2 stage because of the high saturation and low density of the soils. In the subsequent loading stages, only a small amount of accumulated deformation occurs due to the high density of the soils, and the phenomenon of particle migration is not obvious. A small resilience occurs during the intermittent period(IS4-IS7 stage). At the end of the experiment, the ballast void contaminant index(VCI) is 27%, which is close to the critical value of 40% for railway maintenance and needs to pay attention.