Collapsible soils

Collapsible soils present significant geotechnical and structural engineering challenges the world over. They can be found in many forms, either naturally occurring or formed through man made activities. However, an essential pre-requisite is that an open metastable structure develops through various bonding mechanisms. Bonds can be generated via capillary forces (suctions) and/or through cementing materials such as clay or salts. Collapse occurs when net stresses (either via loading or saturation) pass the yield strength of these bonding materials. More commonly collapse is triggered by inundation through a range of different water sources, although their impact varies with these different sources yielding different amounts of collapse. To engineering and mitigate collapsible soils it is essential to first recognise their existence, something that is often is not easy and key geologic and geomorphologic information is vital here. However, collapsibility should be confirmed through direct response to wetting/loading tests, using laboratory and field methods. The key challenge to be faced with collapsible soils is the extent and the degree of wetting that will take place and care is needed to ensure realistic assessments are undertaken. Ultimately, if undertaken appropriately and a treated through a suite of the possible improvement techniques available, than the collapsible potential can be eliminated effectively.