On the hydro-mechanical behavior of unsaturated soils in railway sub-structures

The hydro-mechanical behavior of some unsaturated soils in the sub-structures of both new and conventional railway lines was investigated. For the new lines, an example of track instability related to the sensitivity of the loess subgrade behavior to water content changes was firstly presented, followed by a second example involving the track instability due to the swelling of marl in the sub-structure. For the conventional lines, emphasis was put on the effects of water content and fines content on the hydro-mechanical behavior of the unsaturated interlayer soil which has been formed mainly by the interpenetration between ballast and subgrade soils under the effect of traffic.