Nanoscale observations of leaching of sensitive clay

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Sensitive clays are fine-grained, marine sediments that can undergo an irreversible and pronounced loss of shear strength upon remoulding. Sensitivity, defined as the ratio of peak intact and remoulded shear strengths, reflects the degree of this strength loss. The sensitivity in natural marine clays is strongly influenced by a change in pore fluid chemistry during their formation. Generally, the salinity of the pore water governs the electrochemical interactions and the interparticle bonding. Rosenqvist (1946) proposed that salt leaching is the principal mechanism that increases the sensitivity. Yet, the structural changes at the particle scale as a result of leaching are not fully understood. This study investigates the chemical and nanoscale evolution of a natural sensitive clay from Kärra, Sweden with a sensitivity of approximately 20 and a pore water salinity of about 0.4 M. Different controlled leaching experiments were conducted to study the impact of leaching on the sensitivity and nanoscale structure using a Rowe cell and removing approximately 10% and 25% of the original salts. Na⁺, K⁺_, Mg²⁺, and Ca²⁺ in the pore water chemistry were analysed using Ion Chromatography (IC) before and after each stage to assess the overall reduction in ionic strength and preferential ion removal. Furthermore, Wide X-ray Scattering (WAXS) measurements were performed on the intact specimens to identify nanoscale rearrangements associated with the leaching. Results showed that leaching can alter the balance between ordered and disordered structural domains, especially the I/S mixed layers.

International Conference on Advances and Innovations in Soft Soil Engineering (ICAISSE2026)

Multiphysics Behaviour