Engineers Australia

Unsaturated free-standing mainline railway embankments – Part 2: An example of handling the awkward truthAustralian Geomechanics Award, 2019 Winner

Andrew Leventhal and Tim Hull


The presence of negative pore pressures within cuttings and embankments, and the benefit of the consequent reduction of the likelihood of instability (also known as increased stability), have long been recognised by members of the profession. Negative pore pressures are usually a consequence of environmental influences upon clay soils in particular, and are frequently termed “soil suction”.

The recognition of suctions in the assessment of potential instability, by way of stability analyses, is less common, albeit that the tools are available to conduct such analyses, once the boundary conditions are understood.

Measurement of suction values in the field assists the selection of suction values appropriate for such analyses.

In the companion paper, the authors develop a philosophy and present a defensible model for analysis of free-standing embankments (Hull & Leventhal, 2019). Herein, a case history is presented that demonstrates one such analysis, being for Main Line Railway infrastructure. The results indicate the benefit accrued through recognition of suction in the estimation of potential instability of free-standing embankments.

The paper is intended to alert the profession to an improved assessment technique that incorporates these effects.