Loess soils cover approximately 10% of the world's landmass. Loess is an aeolian quaternary deposit of predominately silt size, which forms open metastable structures through various bonding agents. These agents include water, clay and carbonate and upon loading usually in combination of water, collapse occurs. This collapse can be up to 30% by volume and as a result present a major geotechnical challenge. It is essential therefore, that a full appreciation of what loess is and how it fundamentally behaves is made before any treatment strategies can be economically and effectively employed. Various models have been produced and these will enable a fundamental study of the treatment process to be made. There are a wide variety of improvement techniques that have been used to improve loess ground and include various compaction, inundation and chemical treatments. Other more exotic methods have been suggested, however, their cost or environmental consequences have restricted their practical use. The choices made when faced with loess ground are illustrated with a case history.


Loess covers approximately 10% of the landmass of the world, covering vast areas draped from Western Europe to China, across North America and in regions across South America. It is this that produces the open structure that makes the soil susceptible to collapse upon loading and/or water; a process known commonly as hydrocompaction or hydroconsolidation. In fact, this collapse can cause reduction in volume by up to 30% (Waltham, 1988). This makes loess ground very problematic for engineers and has made it responsible for most of the construction problems related to subsidence. Neglect of the various elements causing loess collapse has in the past caused considerable problems to the built environment and other associated works, such as the Teton dam collapse in 1976, in Idaho, USA (Smalley, 1992).

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