A working platform must support plant on ground that may be much weaker than its granular surface suggests. A new peer-reviewed study by Shehan Mithila, Chaminda Gallage, Kasun Wimalasena and Ashan Pathirana examines how one geocomposite changes that layered system. Published on 18 September 2026 in the International Journal of Geo-Engineering, it provides controlled laboratory comparisons and a proposed design chart. This review examines the full original paper, including the limits of transferring its results to a working site.
What the researchers tested
The Queensland University of Technology team tested twelve configurations in a steel box measuring 1.0 m by 1.0 m by 1.2 m. They used reconstituted fine-grained soil collected from a Queensland road site, prepared to target California Bearing Ratio (CBR) values of 1% and 2.5%. The granular capping was one Type 2.1 unbound material. Reinforced configurations contained a single welded geogrid–geotextile geocomposite at the capping–subgrade interface.
At CBR 2.5%, the programme compared 200, 300 and 400 mm capping layers, each with and without reinforcement, plus a bare-subgrade test. At CBR 1%, it compared 100 and 200 mm layers in the same way, plus bare subgrade. A 200 mm diameter circular steel plate applied the load. An initial loading stage stopped at 550 kPa or 5 mm displacement, whichever came first; after unloading, the second stage continued to peak load. The displacement rate was 1 mm/min. This was not a sustained programme of repeated trafficking.
The measured benefit depended on the layer
For the CBR 2.5% subgrade, reinforcement increased peak bearing capacity by 60% with 200 mm capping and 37% with 300 mm capping, relative to their matching unreinforced configurations. At 400 mm, or twice the plate diameter, its additional contribution was marginal. The result supports a specific mechanism: reinforcement needs enough load-induced deformation and interaction with the aggregate to mobilise its contribution. Simply placing it deeper did not deliver a proportional gain.
Pressure cells helped explain the response. Under the same 550 kPa surface stress, the measured centreline stress at the CBR 2.5% subgrade interface fell from 120 kPa without reinforcement to 97 kPa with reinforcement beneath the 200 mm layer. That is evidence of changed load transfer in this model. It is not a permissible working pressure for a crane, piling rig or outrigger.
A design chart and a worked calculation
The authors normalised capping thickness by plate diameter and divided each platform’s peak bearing capacity by the bare subgrade’s peak capacity. Their chart relates these ratios for the two tested subgrade conditions. This makes the comparisons easier to interpret across the experimental series, although dimensionless axes alone cannot establish full-scale validity.
A worked example illustrates the chart using an assumed 400 mm circular footing, 1,000 kPa contact pressure and a factor of safety of two. It produces calculated capping thicknesses of 460 mm with reinforcement and 624 mm without it, approximately 26% apart. Those figures are an illustrative calculation, not a constructed field trial, a measured saving or a platform specification for another site.
How strong is the evidence?
The controlled comparisons, pressure measurements and checks on compaction provide a useful link between peak capacity and load distribution. The authors also examine possible box-boundary effects. However, the programme contains one soil, one aggregate and one reinforcement product at two target CBR values. It reports no replicated test series or confidence intervals for the percentage improvements. Their repeatability across natural material variability therefore remains unresolved.
The laboratory plate also differs from a tracked machine or a rectangular outrigger pad. Moving loads, repeated operation, eccentric loading, platform edges and changing moisture conditions were not established by these twelve configurations. The authors’ favourable assessment of scale transfer should be read alongside those limits. Their funding acknowledgements include government, university and industry support; they declare no competing interests. Peer review adds scrutiny, but does not remove the need for independent field validation.
Implications for Australian site teams
Civil Insight’s interpretation: the study is useful evidence for comparing reinforcement options during a project-specific geotechnical assessment. Its Queensland materials give it a relevant local context, while its narrow experimental scope sets the transfer limit. Practitioners considering the chart should establish actual subgrade conditions, plant loading and material compatibility, and obtain appropriate verification of the proposed platform. The most useful lesson is to examine where reinforcement can mobilise within the loaded system, then test the assumptions against the intended operation.
Original paper and photographs
Mithila, S., Gallage, C., Wimalasena, K. and Pathirana, A. (2026). “Experimental evaluation and design framework for geocomposite-reinforced working platforms on soft subgrades.” International Journal of Geo-Engineering, 17, article 33. Version of record published 18 September 2026. DOI: 10.1186/s40703-026-00291-7. Open-access full paper.
Featured photographs show preparation and checking of the study’s working-platform models (Figure 4). Photographs and test arrangement: Mithila et al. (2026), CC BY 4.0. Civil Insight’s article is an editorial review of peer-reviewed research.
