The geotechnical significance of osmotic mechanisms as influencing hazards such as expansive ground and landslides has yet to be clarified. The major obstacle has been the lack of appropriate quantitative methods for either predicting or measuring the magnitudes of these mechanisms in situ. This research will be an essential step towards establishing a quantitative basis for comprehensive evaluation of the significance of osmotic mechanisms for geotechnical problems in natural geologic systems such as: 1) damaging differential displacements in expansive ground, 2) the role of weathering mechanisms, such as oxidation of pyrite, in destabilizing ground and triggering landslides 3) geochemical causes of groundwater movement and abnormal pore-fluid pressures in low-permeability environments, and 4) the remediation of contaminated ground. The current understanding of osmotic mechanisms is based primarily on controversial field studies concerning anomalous groundwater pressures and compositions in sedimentary geologic basins, and also on laboratory and theoretical studies of monominerallic clays with uni-electrolyte pore fluids. Laboratory studies of osmotic mechanisms on natural earth materials and unambiguous field studies of these mechanisms ion geotechnical systems are in their infancy. The goals of this research are: 1) to develop an integrated experimental and theoretical approach for quantifying osmotic mechanisms on undisturbed samples of natural earth materials, and 2) to use this approach to quantify the importance of osmotic mechanisms that influence the expansive behavior of the Pierre Shale, namely osmotically-driven pore fluid flux and osmotically-induced volumetric repulsion among clay particles. The objectives for accomplishing these goals include: 1) mobilizing a triaxial system for measuring the coupled fluxes of pore fluid constituents, 2) selecting, sampling, and characterizing a test site in steeply dipping strata of Pierre shale, using both conventional methods and the new experimental system, 3) expanding existing coupled-flow theory to include swelling pressures and volume changes in expansive clay shales from osmotic mechanisms, and 4) analyzing the new experimental data with the new theoretical framework to quantify the geologic, physical, and chemical controls on the efficiencies of osmotically-driven pore fluid flux and osmotically-induced volumetric repulsion among clay particles.
