An experimental study of the behavior of drilled shaft foundations subjected to static and repeated lateral and moment loading under drained conditions

Drilled shaft foundations are used often by the electric utility industry to support structures subjected to lateral and moment loads. This study was conducted to investigate the drained response of drilled shafts subjected to this type of loading. Static and cyclic conditions were addressed.;The testing program included static and cyclic tests. All tests were controlled by a computer using an electro-hydraulic testing system. Static tests were run in the displacement control mode, while cyclic tests were run under the force control mode.;The load-displacement response of tests in loose and medium dense is smooth and nonlinear, with no apparent yield. In dense sands, however, post-peak softening occurred. Capacities were predicted using limit equilibrium methods. Predictions made using Hansen's method gave overall good agreement with the capacities. Load-displacement responses are well-represented by a hyperbola, for which an initial stiffness and a hyperbolic capacity are sufficient to fully describe. The initial stiffness was evaluated using elastic continuum solutions.;Cyclic loading resulted in no decrease in the capacity and either stable or metastable displacement accumulation. Metastable conditions occur in dense sand if the accumulated displacements exceed displacements that correspond to the lateral/moment limit. Displacement accumulation rates increase with an increase in the ratio of the cyclic load difference to the maximum cyclic load. These displacements are added to the static displacement at maximum cyclic load level to obtain the total accumulated displacements under cyclic loading.;Soil deposits were prepared at different initial conditions in a large test pit. Sand properties were obtained from unit weight measurements and laboratory and in-situ tests. A total of twenty one deposits were constructed, in which 56 tests and four shake-down tests were performed. Two scales were addressed in this study, with depth to diameter ratios that ranged from 2.6 to 9. Eccentricity to depth ratios ranged from "0" to 5.