Effects of hydraulic shear stress and rate of erosion on the magnitude, degree, and rate of collapse

Abstract

Arid regions worldwide are plagued by collapsible soils. Collapsible soil is characterised by the sudden decrease in volume that occurs when it is subjected to inundation under constant stress. This volume change manifest itself as drastic and unpredicted foundation settlement, which may lead to further catastrophic failure of the supported structures. Collapse settlement is the term applied to the additional settlement of a foundation due to wetting of the underlying soils. The results of an experimental investigation of the effects of the saturation of soil with water, kerosene, and crude oil, and of the effects of the fluid head on the magnitude, degree, and rate of collapse of the underlying soil are presented in this paper. Soil erodibility is presented in terms of the applied hydraulic shear stress and the rate of erosion. The relationship between soil erosion and the magnitude and rate of collapse is examined. Empirical methods for the prediction of the magnitude and rate of collapse of a soil saturated with the test fluids and subjected to a hydraulic constant head are proposed.

Keywords:

• collapsible soil
• wetting
• hydraulic shear stresses
• constant-head
• rate of erosion
• rate of collapse
• fluid density
• viscosity
• empirical formulae

Acknowledgements

Financial support from the Natural Science and Engineering Research Council of Canada (NSERC) and from Concordia University is acknowledged.