Case study in the Northern Cape (Loopeng area), South Africa, confirming occurrence of a collapsible sand soil structure in transported soils

Abstract

Abstract Testing was performed on transported soils belonging to recently deposited sandy-silty soil deposits occurring in and around Loopeng Village, Northern Cape Province, South Africa, in order to determine the occurrence and order of magnitude of a collapsible sand soil structure. Various empirical geotechnical characteristics including: in situ soil profile structure description, particle grading curve and clay content, soil classification, soil density and void ratio were compared to collapse potential values determined with oedometer testing, in order to judge the success with which the empirical characteristics can be utilised to predict the occurrence of a collapsible soil structure. From the results it is clear that a collapsible sand structure exists in the transported soils (both aeolian and fine alluvial) and that the empirical descriptors mostly correctly indicate the occurrence of the particular soil structure when compared to existing studies on collapsible sands. The one descriptor which reflects a relatively poor prediction of a collapsible soil structure, namely the in situ soil profile structure description, is considered to be a poor indicator due to erroneous or poor in situ soil structure observations. These poor observations result from unfavourable local conditions namely dry, dusty soil conditions and very brief intact standup time of test pit side walls.