Evaluation of a New P-Y Analysis Tool for Lateral Analysis of Drilled Shafts Using Load Tests in Nevada-Paper

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The study evaluates NVShaft, a MATLAB-based finite-difference program for analyzing the lateral response of drilled shafts using nonlinear p-y models. The program includes 19 p-y curve models and supports layered soils, nonlinear shaft moment–curvature behavior, user-defined load locations and boundary conditions, tapered shafts, and p-multipliers. Comparisons with LPILE showed close agreement in a layered-soil example, with differences of 2.66% in maximum deflection and 1.24% in maximum bending moment.<br /><br />NVShaft was also used to model 2-ft- and 8-ft-diameter shafts tested at the I-15/US 95 project site in Las Vegas. The subsurface included stiff sandy clay, partially cemented soils, and caliche layers. The analyses incorporated the lateral load application point and used appropriate p-y models for the soil and cemented layers.<br /><br />Predictions agreed well with measured responses at low loads for both shafts. For the 2-ft shaft, the predicted response remained reasonably consistent with measurements, including curvature at small to moderate loads. For the 8-ft shaft, predictions were stiffer than the measured response at high loads. The authors suggest that damage and cracking caused by the preceding axial load test may have softened the shaft’s lateral response; soil heave, cementation, and uncertainty in estimated soil properties also complicated interpretation.<br /><br />Overall, the results support NVShaft’s ability to perform conventional p-y analyses and reasonably predict drilled-shaft behavior, while highlighting the challenges of modeling large shafts affected by prior loading and complex, cemented soils.

Keywords

NVShaft

drilled shafts

lateral response

finite-difference analysis

nonlinear p-y models

layered soils

moment-curvature behavior

p-y curve models

LPILE comparison

I-15/US 95 project