Abstract

This paper presents a modified version of the Booker et al. cycle-based pore pressure generation model for use with strain-controlled cyclic loading tests on sandy soils. The original Booker et al. model has been widely used in geotechnical engineering because of its simplicity and computational efficiency; however, it was developed using stress-controlled cyclic test data and does not accurately capture the pore pressure response observed in strain-controlled cyclic loading. In strain-controlled tests, excess pore pressure typically develops rapidly during the early stages of loading and more gradually as liquefaction is approached, resulting in a pore pressure–cycle ratio relationship fundamentally different from that produced by the original model. To address this limitation, a Modified Booker Model was developed through curve fitting of laboratory test data obtained from strain-controlled cyclic triaxial and cyclic direct simple shear tests. The model was evaluated using the results of 51 cyclic triaxial tests and 101 cyclic direct simple shear tests performed on clean sands and sand–silt mixtures with fines contents both above and below the threshold fines content (TFC). The model produced excellent agreement with measured pore pressure responses, yielding average coefficients of determination (R2) ranging from 0.921 to 0.989 depending on the test type and soil conditions. The results indicate that the Modified Booker Model provides a practical, accurate, and computationally efficient method for predicting pore pressure generation during strain-controlled cyclic loading of sands and silty sands.

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