Soil enhancement by fluid injection for in situ treatment of contaminated soil

摘要

Across North America, there are numerous sites where industrial, commercial or waste management activities have resulted in the release of a wide variety of contaminants into the ground. Many technologies used for in situ remediation of contaminants in soil and groundwater promote the movement of fluids through the subsurface to either treat the contaminant in place or to facilitate removal of the contaminant for surface treatment. The in situ treatment of contaminants located in low permeability soil is a particularly challenging problem. Existing in situ techniques for treating contaminants are generally ineffective in these soils and seldom used. The objective of this research has been to investigate a simple and low cost fluid injection technique that relies on a soil shearing mechanism to create an enhanced flow regime within the soil. An enhanced flow regime allows greater accessibility to contaminants and enables conventional in situ treatment technologies to be used more effectively over a broader range of soil conditions. -- The research included an experimental program consisting of fluid injection tests carried out from vertical and horizontal wellbores, and numerical simulations of injection test results. Reduced scale injection tests were carried out in a geotechnical centrifuge and large scale field experiments were carried out at the former U.S. Naval Facility in Argentia, NF. The numerical modelling work also included the analysis of data from an injection test program carried out by others in a large calibration chamber. -- The injection tests resulted in the formation of high permeability discontinuities within the soil surrounding the wellbore. Yielding due to shear was found to dominate under certain conditions, however, other mechanisms also occurred including porous flow without yielding, cavity expansion, and yielding in tension. The role that each of these mechanisms plays, is influenced by a complex interrelationship between physical and geotechnical parameters including pore and injection fluid properties, injection zone details, the soil stress state, permeability, constitutive behaviour, and structure.