Mechanical behavior of micaceous clays

This study aims to investigate the effect of mica content on the mechanical properties of clays. Commercially available ground mica was blended with a locally available clayey soil, at varying mica contents by mass of 5%, 10%, 15%, 20%, 25% and 30%, to artificially prepare various micaceous clay blends. The preliminary testing phase included consistency limits and standard Proctor compaction tests. The primary testing program consisted of unconfined compression (UC), direct shear (DS) and scanning electron microscopy (SEM) tests. The test results showed that the liquid and plastic limits exhibited a linear, monotonically increasing trend with increase in mica content. The rate of increase in the plastic limit, however, was found to be greater than that of the liquid limit, thereby leading to a gradual transition towards a non-plastic, cohesionless character. The soft, spongy fabric and high water demand of the mica mineral led to higher optimum water contents and lower maximum dry unit weights with increasing mica content. Under low confinement conditions, i.e. the UC test and the DS test at low normal stresses, the shear strength was adversely affected by mica. However, the closer packing of the clay and mica components in the matrix under high confinement conditions offsets the adverse effects of mica by inducing frictional resistance at the shearing interface, thus leading to improved strength resistance.Jiahe Zhang, Amin Soltani, An Deng, Mark B. Jaks