Assessment of Mechanical Properties of Clay Containing Smectite and Carbonate

The present study highlights about mechanical properties of clay containing smectite and carbonate. Numerous research has examined the relationship between the mechanical behavior and physicochemical characteristics of clays. Because they are relevant to various fields, such as cleanup, mud drilling, civil engineering, and the storage of radioactive and hazardous waste, the mechanical properties of clays are very significant. The smectite used in this work is from southwestern Tunisia, specifically from Oued Tfal, near the town of Gafsa, and is referred to as “OT”. This study involved characterizing the physicochemical and mechanical properties of the raw clay following treatment with hydrochloric acid and purification. The work aims at elucidating the influence of the pure clay fraction, including compensating cations, on the clay’s hydromechanical properties. The thermal study sample revealed 32.5% of carbonates in the raw clay. The elimination of carbonates by acid attack yielded the following results: If treatment by 0.5M HCl represents a total elimination of carbonates, the clay fraction probably contains altered layers. To eliminate the excess carbonate (6.03%), the sample was treated with 0.4 M HCl without deterioration of the structure of the silicate fraction. The hydromechanical study of three clay samples (raw (OT), purified (OTNa), and 0.4M HCl-treated) clearly showed the relationship between the cation exchange capacity, the percentage of carbonate content, and the swelling pressure. In the oedometer-based mechanical study, the measures of swelling pressures under constant load yielded values of 15.46, 90.00, and 274.60 kPa for OT, OT (0.4), and OTNa, respectively. These values highlight the high swelling of the clay fraction of the deposit of Oued Tfal, and the effect of carbonate on the mechanical stability of this clay, as 6% carbonates significantly altered the swelling properties of the clay.