Characterizing the regional variation of ballast particles’ movement during the increase of local void in ballast bed

Abstract

Local void is usually recognized until consequent track diseases, like mud pumping, track irregularity, etc. The progressive development of local void is always together with adaptive adjustment of ballast and ballast bed, indicating a potential avenue to early recognition of local void. In this paper, the movement characteristics and contact stress distribution of ballast particles at different locations during multi-stage void beneath the ballast bed are obtained by a full-scale model test under sinusoidal cyclic loading. The local void is set beneath the ballast bed right under the rail seat, with four stages of equal void increment. Six wireless particle sensors are installed to obtain the characteristics of particle movement at typical locations, and meanwhile the longitudinal contact stress at the void position is obtained by tactile pressure sensors. The results show that particle movement can effectively reflect changes in the supporting status of the foundation bed. As the volume of void increases, the acceleration of particle sensors at the void position gradually decreases to near zero, while the acceleration of the particles in the upper part of the void area increases. During the development of void, the movement of the particles adjacent to the void position is intensified with varying degrees.