Geotechnical problems related with loess deposits in Northern France

TL;DR

This paper investigates the collapse susceptibility of loess deposits in Northern France, focusing on water content effects and microstructure analysis to understand sinkhole formation along high-speed railway lines.

Contribution

It provides a detailed geotechnical study of loess collapsibility, applying unsaturated soil mechanics and evaluating collapse criteria specific to loess deposits.

Findings

Collapse susceptibility increases with water content.

Microstructure observations reveal pore structure influences collapsibility.

Existing collapse criteria are assessed for validity on loess samples.

Abstract

Special problems were encountered in some areas in Northern France where the high speed railways (TGV Nord) crossed some loess deposits that appeared to be specially sensitive to change in water content and susceptible to collapse. Numerous sinkholes appeared along some sections of the line following wet climatic periods. After a general geological and geotechnical presentation of loess deposits and collapse susceptibility, in which some tools of the mechanics of unsaturated soils are reconsidered with special application to loess collapsibility, this paper describes the results of a geotechnical study carried out on block samples of intact loess. Collapse susceptibility is examined in the light of microstructure observation. The dependence of collapse to water content changes is examined and the validity of various existing collapse criteria is investigated.