Abstract

Drilled shafts are widely used as a foundation system for a variety of structures. Although drilled shafts are extensively used, there is no standard that helps engineers to design for torsional loading regarding geotechnical resistance. In contrast to the broad research on the analysis of deep foundations under axial and lateral loads, the analysis of drilled shafts under torsional loading has received less consideration. Furthermore, the torsional resistance mechanism is not well understood, and the existing design methods have been validated against limited experimental data. This paper presents an up-to-date literature review regarding torsional resistance of drilled shafts. Several methods for calculating the torsional resistance were compared in a statistical manner against available test data. Cohesive, cohesionless, and layered soils were included in the analysis. There is no clear best choice for predicting the torsional resistance of drilled shafts. However, the authors suggest the use of the α, β, and CDOT methods. A theoretical comparison between those methods is provided, and major differences are highlighted. Experimental research to investigate torsional geotechnical resistance and load transfer is highly recommended.