Analysis of the railway heave induced by soil swelling at a site in southern France

TL;DR

This study investigates the swelling behavior of expansive clayey marl at a French railway site to quantify soil-induced heave and distinguish it from landslide effects, combining laboratory tests and field data.

Contribution

It introduces a combined laboratory and field approach to estimate soil swelling and its contribution to railway heave in a specific site.

Findings

Swelling potential was quantified through flooding tests under in-situ stress.

Swelling induced by excavation was assessed via loading and unloading tests.

The study estimated the soil swelling contribution to the observed heave, separating it from landslide effects.

Abstract

In order to better understand the heave observed on the railway roadbed of the French high-speed train (TGV) at Chabrillan in southern France, the swelling behaviour of the involved expansive clayey marl taken from the site by coring was investigated. The aim the study is to analyse the part of heave induced by the soil swelling. First, the swell potential was determined by flooding the soil specimen in an oedometer under its in-situ overburden stress. On the other hand, in order to assess the swell induced by the excavation undertaken during the construction of the railway, a second method was applied. The soil was first loaded to its in situ overburden stress existing before the excavation. It was then flooded and unloaded to its current overburden stress (after the excavation). The swell induced by this unloading was considered. Finally, the experimental results obtained were analyzed, together with the results from other laboratory tests performed previously and the data collected from the field monitoring. This study allowed estimating the heave induced by soil swelling. Subsequently, the part of heave due to landslide could be estimated which corresponds to the difference between the monitored heave and the swelling heave.