Laboratory simulation of train loading and tamping on ballast

Abstract

A box test has been developed to simulate the effects of train loading and tamping on the performance of four different ballasts. The ballasts have each been loaded in the box by a simulated segment of sleeper for up to a million cycles of traffic loading, representing early life behaviour. Simulated tamping has also been performed on the ballasts causing rearrangement of grains. Results from the box tests have been found to be repeatable, and give realistic stiffness and settlement characteristics compared with full-scale tests on trackbeds in the UK. The performance of each of the four ballasts has been determined in terms of settlement characteristics, stiffness and degradation, and the results have been found to agree with results from Los Angeles abrasion tests and water absorption values, and also with petrographic analysis, thus demonstrating the usefulness of the box test for estimating the performance of ballast in the field.

Discrete element modelling of under sleeper pads using a box test

“…The improvement of using geogrid-reinforced ballast has also been successfully [22][23][24][25] by representing the geogrid as a group of bonded spheres, which is similar to the generation method for the USP in this study. In this paper, DEM is employed to simulate the behaviour of an under sleeper pad in a box test developed by McDowell [26]. The USP is modelled by three layers of hexagonal-closed-packed, bonded spheres.…”

Numerical simulation of land subsidence caused by subway train vibration using PFC

“…According to published results, different vibration frequencies were used to investigate the dynamic response of subsurface layers under traffic loading. McDowell et al (2005) performed laboratory simulation of train loading at a frequency of 3 Hz. Zheng and Liu (2007) carried out field testing on a section of Shanhgai metro line 1, and it was found that the vibration frequency was mainly at a low frequency of 10 Hz.…”

Whole Issue - Civil Engineering, Volume 167, Issue 4 (High Res. - 39MB)

“…Tamping disturbs the load-bearing structure of the ballast bed (Ahmed, 2014;Aingaran, 2014) and may damage the ballast particles (McDowell et al, 2005), resulting in the increasingly rapid development of settlement with trafficking after each tamping cycle (Selig and Waters, 1994). Ballast generally offers sufficient resistance to unwanted movement of the track, while still allowing adjustments in line and level to be made relatively easily when required.…”