Uplift Testing of Model Drilled Shafts in Sand

Results of four uplift tests on large-scale cast-in-place straight-sided model drilled shafts in sand are given. The extensive instrumentation and soil placement procedures are described. The results show: (1)A cylindrical shear model describes the tests well; (2)the load-butt deflection response nonlinear, nonlinear and cumulative net compression occurs during loading; and (3)butt deflections at failure are small and consistent. The proposed failure model cosiders an initial at-rest state and active yield during the construction to obtain the failure conditions. Residual capacities are smaller than the ultimate and the percentage decrease increases with increasing initial shear strength.