Evaluation of Existing P-Y Models For Caliche Based on Numerical Analysis of Raiders Stadium Lateral Load Tests-Paper

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The study evaluates whether existing p–y models for vuggy limestone and Florida limestone can represent caliche’s lateral resistance in drilled-shaft analyses. Researchers used NVShaft, a MATLAB-based beam-on-nonlinear-Winkler-foundation program, to simulate four lateral load tests on 2-ft-diameter, approximately 66-ft-long continuous-flight-auger piles at the Raiders Stadium site in Las Vegas. Because laboratory data for caliche were unavailable, its properties were estimated from local practice and published correlations, including an assumed unconfined compressive strength of 12 ksf.<br /><br />For the two tests with caliche near the ground surface (LT-EL and LT-FL), both rock models generally produced reasonable predictions, particularly at the design load. At that load, reported normalized pile-head deflection errors were small: 0.006% and −0.06% for the vuggy-limestone model, and 0.015% and −0.05% for the Florida-limestone model, respectively. The vuggy-limestone model generally yielded lower absolute errors across the comparisons. Predictions were also reasonable at twice the design load, though discrepancies increased in some cases.<br /><br />For LT-CL and LT-AL, where caliche was deeper, changing the caliche model had little effect because overlying cemented soils largely governed the response. The results also supported the use of a weakly cemented-sand p–y model for those layers.<br /><br />Overall, the findings suggest both limestone models can provide useful approximations for caliche, especially when caliche is shallow and at or below design-level loading. However, limited site characterization and uncertainty in caliche properties constrain confidence; the authors recommend further research and development of caliche-specific p–y models.

Keywords

caliche

p-y models

lateral resistance

drilled-shaft analysis

vuggy limestone

Florida limestone

NVShaft

beam-on-nonlinear-Winkler-foundation

continuous-flight-auger piles

Raiders Stadium