Evaluating the Performance of Tire Cell Foundations as Subballast Capping Layers under Cyclic Train Loading

Author(s)

ic Train Loading, Buddhima Indraratna, Fatima Mehmood https,Trung Ngo, Cholachat Rujikiatkamjorn,

Abstract

This paper presents laboratory and field test results on the use of the Tire Cell Track Foundation (TCTF), which consists of an assembly of rubber tyres filled with various materials to reinforce the capping layer beneath the ballast. Large-scale cubical triaxial tests were conducted using two different infill materials: crushed basalt rockfill and recycled spent ballast.

These materials were subjected to cyclic loading with varying magnitudes and frequencies. A multistage cyclic loading was performed, both with and without the inclusion of tyre cell reinforcement, in four stages, each comprising 25,000 loading cycles. In the first two stages, the frequency was increased from 10 to 15 Hz for an equivalent axle load of 25 tonnes. In the third stage, the axle load was raised to 35 tonnes with a frequency of 10 Hz, further increased to 15 Hz in the final stage.

Results indicate that TCTF can reduce vertical stress transmitted to the subgrade layer and limit vertical and lateral displacement of the ballast. Furthermore, TCTF stabilised the track without significantly reducing the resilient modulus of the ballast under increasing load and frequency. Compared to a traditional track, TCTF reduced the breakage index by 40.1% for crushed latite basalt and 28.3% for spent ballast (recycled from ballast tips). The improved track performance can be attributed to the increased confining pressure provided by the tyre cell assembly and the enhanced damping properties of the rubber tyres.

Additionally, the TCTF concept was tested on a fully instrumented track (20 m long) subjected to a 22-tonne locomotive with two fully loaded carriages. The trial section, constructed in a heavy haul maintenance yard in western Sydney, Australia, demonstrated that TCTF significantly reduces stress transfer to the subgrade soil. This reduction mitigates excessive deformation and subgrade failure, positioning TCTF as a sustainable solution for soft and weak subgrade soils, despite initial settlement.

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