ABSTRACT
The determination of input parameters such as limiting strength and subgrade modulus is critical to design of piles, and test data can be used to back-estimate them. However, the accuracy of the back-estimation under torsional loading must be justified by critical lengths. This chapter provides analytical solutions for a torsional pile embedded in a two-layered soil profile, which are expressed in terms of Bessel functions of non-integer order, and simplified expressions for rigid and flexible piles. In addition, a spreadsheet program, GASPILE, is also available for gaining numerical solutions. The solutions are presented in non-dimensional charts, and can be used to deduce the modulus and strength (friction) between torsional and vertically loaded pile. Examples are provided for the back-estimating of the input parameters.
