Enhanced delivery of chemical agents in soil improvement applications

The paper explores the concept of enhanced delivery of chemicals for soil improvement applications based on clay treatment by guanidinium salt solutions. This treatment is shown to cause significant increase in shear strength and decrease in the swelling potential of clayey soils, which are highly desirable results in many geotechnical applications. Whereas some other soil improvement techniques reduce soil permeability as a side effect, guanidinium increases permeability of pure bentonites and quartz–bentonite mixtures by an order of magnitude and maintains this increase under high confining stresses, thus enhancing its own and other agents' delivery. It is shown that molecular change of the clay minerals on the level of the surface chemistry results in an aggregation of small clay minerals to stable larger particles, thus providing a system of open pores. For a better understanding of the mechanisms behind the process of enhanced delivery, a simple analytical hydro-chemical model is developed and successfully validated against both experimental data from soil samples subjected to the flow of guanidinium solution and a more sophisticated numerical analysis. Potential applications of this technique to stabilisation of creeping landslides will be investigated in a companion paper.