Lateral stability of rigid poles subjected to an applied couple

Functional relationships are developed for the load-deflection characteristics of a rigid, vertical pole, embedded in sand and subjected to an applied couple. The study is based on non-dimensional techniques and the physical variables included in the theoretical analysis are the ground-line deflection, depth of embedment, geometry of the pole cross-section, applied couple, time of loading, and soil parameters. The soil parameters used include the density, angle of internal friction, flow characteristics, and relative density of the sand. Non-dimensional techniques in conjunction with small scale model studies are used to determine the explicit form of the interrelationship among the above physical variables for a pole embedded in a very dense, uniform, fine, dune sand of constant properties and subjected to an applied couple. Hyper-bolic prediction equations are given from which the load-deflection characteristics of a prototype pole might be estimated. A failure criterion in the form of a stability number relating the ultimate applied couple to the geometry of the pole-soil system is given and correlated with the failure criterion of the same pole-soil system subjected to a horizontal ground-line thrust. Several illustrative examples are worked.