Laboratory Modeling of Laterally-Loaded Drilled Shafts in Clay

Abstract

The behavior of free-head rigid drilled shafts under static and cyclic lateral and moment loading was investigated using laboratory models in relatively large test chambers. This testing program represents perhaps one of the first larger-scale laboratory test series to utilize cast-in-place concrete shafts in consolidated and prestressed cohesive soil deposits for realistic simulation of prototype drilled shafts in clays. The construction procedure incorporated the actual effects of concrete curing and soil/concrete interface roughness, and the soil-deposit preparation included the characteristic anisotropy and overconsolidation associated with natural clays. A total of 28 cylindrical shafts having diameters of 51, 89, and 175 mm (2.0, 3.5, and 6.9 in.) and depth-to-diameter ( D /B) ratios of 3–8 were constructed and tested. Many of the shafts were instrumented with total stress cells and pore-water stress transducers to permit both total and effective stress measurements during the load testing. The results of the lateral and moment load tests indicated a high degree of nonlinearity in the monotonic static load-displacement response, but it can be represented adequately by a hyperbola. This hyperbola also provides a reference backbone curve for the cyclic loading behavior.