Advancing the state of the art of cyclic direct simple shear Testing: Histories, current status, challenges and future trends

The Cyclic Direct Simple Shear (CDSS) test, designed to simulate in-situ stress-strain behaviors during seismic loading, has become a widely used tool for assessing liquefaction potential and soil constitutive properties. Recent advancements have broadened its applications in constitutive modeling, unsaturated soil mechanics, and shear wave velocity measurement. However, the CDSS apparatus suffers from inherent limitations, including the absence of complementary shear stresses on vertical boundaries, stress and strain concentrations at platen edges, incomplete stress component measurement, potential for inaccurate soil property assessment, and assumptions required for Mohr’ circle construction. These limitations, often overlooked by practitioners, can lead to unreliable results. This paper comprehensively reviews the histories, development, applications, and, critically, the limitations of CDSS testing. We examine the ongoing controversies surrounding its use, discuss future trends, and highlight both the appropriate engineering applications and the theoretical and experimental drawbacks. This review aims to provide a deeper understanding of CDSS testing and promote more informed interpretation of test results.