The Lachenaie clay deposit: some geochemical and geotechnical properties in relation to the salt-leaching process

Abstract

This paper summarizes a detailed geotechnical and geochemical characterization program for the Champlain clay deposit in Lachenaie, Quebec. Presently, the clay pore water is saline. The main objective of the testing program was to study the leaching of the clay saline pore water since its deposition. Four issues are discussed in this paper. First, the deposit is shown to comprise two distinct clay layers with contrasting geotechnical properties. The liquid limit and grain-size distribution are the properties that best distinguish the two materials. The upper layer is more plastic while the lower one is relatively silty. The occurrence of these two layers is shown to be in agreement with some recent findings in Quaternary geology. Second, the relatively high pre-consolidation pressures of the clay in the Lachenaie area are shown to be coherent with an erosion scenario and the elevation of a neighbouring bluff previously interpreted as an erosion terrace. Third, the relatively constant hydraulic conductivity values obtained from permeability tests throughout the deposit are shown to be consistent with the variations of liquid limit and void ratio in the two clay sublayers. Fourth, the occurrence of sensitive clay pockets (sensitivity greater than 50) in this otherwise saline clay body is elucidated.

A coupled analysis of cavity and pore volume changes for pulse tests conducted in soft clay deposits

“…A series of pulse tests were performed as part of an important testing program designed to study the migration of the saline water trapped in the Lachenaie clay deposit (Figure ) since its deposition in the Champlain Sea some 12 000 to 10 000 years ago . The extensive testing program allowed a vast array of issues pertaining to aquitard hydrogeology and geotechnical engineering to be studied . Some clay properties were measured using different techniques to compare their effectiveness.…”

Influence of seasonal hydraulic head changes on slug tests conducted in shallow low-permeability soils

“…These values are relatively high for Champlain clay. The upper and lower clay sublayers produced similar K values during the field and laboratory testing programs described by Duhaime et al (2013). A mean K value of approximately 2×10 -9 m/s was obtained.…”

Leaching Impact on Compressibility and Shear Strength of Undisturbed and Cement-treated Champlain Sea Clay

“…Champlain Sea clay or Leda clay is one of the sensitive and fine-grained late glacial marine clays commonly found along the St. Lawrence Lowlands region in Ontario and Quebec (Duhaime, et al, 2013). Figure 2-1 illustrates the distribution of Champlain Sea clay near Ottawa, Montreal, and other high population areas along the St. Lawrence River.…”