Normalized undrained shear strength of clay shales

This paper examines the possibility of normalizing the undrained shear strength behavior of clay shales. Shales are formed in sedimentary basins by diagenetic processes, which turn young clay sediments into compacted and lithified shales. Cementation at grain contacts affects many properties of shales including the apparent preconsolidation and shear strength. Based on a study of 25 different types of materials, the normalized undrained shear strength of clay shales was found to correlate satisfactorily with overconsolidation ratio following the SHANSEP (Stress History and Normalized Soil Engineering Properties) normalization procedure for clays. The normalized undrained shear strength correlation appears valid regardless of the cause of the apparent preconsolidation. Correlations of the apparent preconsolidation stress with unconfined compressive strength and compressional wave velocity are proposed to predict the normalized undrained shear strength of clay shales.