| Leda Clay is a general name applied to the post-glacial marine sediments of the St. Lawrence and Ottawa River Valleys, a group of sensitive, landslide-prone soils which have been responsible for considerable loss of human life and property. Studies of naturally occurring deposits of Leda Clay are made difficult by the variability of this material. For this reason, the present study was undertaken with a controlled suite of laboratory samples. These were generated by re-sedimenting, re-consolidating and leaching Leda Clay with specially designed equipment and procedures.;A specially designed vane apparatus and procedures were developed to determine the deformability characteristics and shear strength of the samples. It was possible to measure very small elastic deformations in both undisturbed and remolded material. The sensitivity of the samples was found to be related to the percent of monovalent cations in the pore water. The greatest sensitivity was exhibited by samples to which colloidal SiO(,2) had been added.;A system was designed and built to measure the induced-polarization (IP) response and other electrical properties of the samples. The time-dependent rise in voltage exhibited by samples having an IP response was found to be related to the pore-water salinity.;The results of this research indicate that profitable areas for future research include more detailed investigations of: the elastic properties of undisturbed and remolded soils; the induced-polarization response and other electrical properties of soils; and, the diffusion of ions in soils.;The reconstituted samples were subjected to extensive testing, using an integrated program which allowed many tests to be performed on each relatively small sample. Tests included determination of: particle-size distribution; water content; Atterberg limits; oxidation-reduction potential; pH; cation-exchange capacity; coefficient of permeability; concentrations of pore-water cations and adsorbed cations; and, diffusion coefficient. These tests indicated that the samples were similar in most respects to naturally occurring material, except that the oxidizing conditions of the laboratory are thought to have caused some weathering. |
