Abstract
Clay geomaterials pose a great challenge in geotechnical design due to their complex mechanical behaviour. Despite the vast research on clay mechanical behaviour, mechanisms occurring at the particle-scale still remain largely unknown. Particle-to-particle interactions include electro-chemical forces, which can be in turn associated with repulsive/attractive Coulomb interaction and attractive van der Waals force. This work aims to investigate the role of attractive forces (van der Waals and Coulomb) via their control of the process of aggregation (attractive forces tend to form aggregates of clay particles). Dry clay particles were compressed under high stress to reduce particles distances and activate attractive van der Waals and Coulomb forces. Particle size distribution was then measured using laser granulometry to explore aggregation formation. Laser granulometry tests were performed with and without ultrasound and with and without dispersant. Results show that the higher the compressive stress applied to the sample, the bigger is the ‘particle’ size measured by the laser granulometry, which corresponds to formation of aggregation due to attractive forces. Ultrasound appeared to disaggregate the aggregates thus suggesting that van der Waals and Coulomb forces are sensitive to dynamic loading.
Highlights
Mechanical and hydraulic behaviour of clays is controlled by processes occurring at the particle scale
In suspension Coulomb force is computed according to the Double Layer Theory ([1, 2]). [3] presented the first study about interparticle forces of cohesive soils, double layer forces. [4] included the van der Waals forces in the study of clay soil
The first approach is based on the point of zero charge (PZC), which for kaolinite is between pH 5 and 6 ([9, 15])
Summary
Mechanical and hydraulic behaviour of clays is controlled by processes occurring at the particle scale. If charges surfaces have the same sign, they will be repulsive, otherwise they will be attractive These forces will depend on the magnitude of the electrical field generated by charges of particle surface. In suspension double layer electrochemical forces occur due to the presence of unbalanced charges within in the clay particle. These charges create an electrical field that attracts ions forming a diffuse double layer. The kaolinite particle has three surfaces that are electrically charged: the octahedral face, the tetrahedral face, and the edges. Kaolinite particles are positively charged on the edges at low pH and negatively charged on the face. Kaolinite particles are negatively charged both on the edges and on the faces.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
