Shearing Behavior of Calcinated Kaolin Clay in Ring Shear Apparatus

Calcined clay (CC) is often used to stabilize problematic soils through its cementitious property. The mechanical behavior of CC might differ from that of raw clay due to calcination and the presence of calcite impurity. The safety and design of the infrastructure built on hilly and sloped clay terrains are influenced by the residual shear strength. Many studies have been done to understand the influence of stress history, strain rate, clay mineralogy, and normal stress on the residual shear strength of clay soils. However, available studies on the residual shear strength of CC are scarce, although it is essential for slope stability analysis. This study investigated the drained torsional shear and volume change response of compacted and slurry calcinated kaolin samples from the laboratory ring shear test under three different normal stresses. The anomalous peak shear response was observed under the volumetric contractive behaviour for calcined kaolin clay in normally consolidated (NC) conditions. Further, the clay particle associations were investigated at different stages of shearing in NC conditions using the field emission scanning electron microscopy (FESEM) technique. FESEM analysis indicated that the anomalous peak behavior was attributed to the cementation bond between the clay particles.