Role of expansive soil and topography on slope failure and its countermeasures, Yun County, China

High content of expansive clay minerals coupled with exposure to moisture content fluctuations, is known to cause alternate swelling and shrinkage of soils. Typically, this phenomenon causes deformation and failure of structures that are constructed on such soils. The design and implementation of countermeasures against slope failures and associated failures of structural foundations in field scenarios in which expansive soils are exposed require an integrated analysis of the soil mineralogical structural characteristics and stratification, site topography and the orientation of structures relative to the unstable soil beds. In this combined field and laboratory study, it has been found that mantling of ridge tops by expansive clay soils in Yun County, China, makes buildings sited therein, more susceptible to settlement and structural damage than on the slopes and valley floor where sandstone and gravelly rock pose limited volume change risks. This investigation shows that topography of the ridge-and-gully and engineering properties of expansive soils are two significant determinants of the severity of slope failure, and the engineering measures taken in the past 25 years have been validated to be cost-effective for controlling slope failures in Yun County, China.