Drained Cavity Expansion–Contraction in CASM and Its Application for Pressuremeter Tests in Sands

Abstract

The contraction behavior of monotonically expanded cavities is intriguing as it offers insights into certain geotechnical scenarios, especially for pressuremeter tests, where the unloading data is equally informative as the loading data. Despite many solutions for cavity expansion, attempts for the analyses of cavity contraction from an expanded state were rarely made. To extend previous solutions to include contraction, this paper presents a novel semianalytical solution for drained contraction of spherical and cylindrical cavities from an initially expanded state in soils characterized by a unified state parameter model for clay and sand (CASM). Given the nonself-similar nature of the contraction after expansion problems, the hybrid Eulerian-Lagrangian (HEL) approach is employed to derive distributions and evolutions of stresses and strains around the cavities during the unloading process. Combined with the previous expansion solution, the complete loading-unloading cavity pressure curves and stress paths at the cavity wall are presented and verified against numerical simulations. Following validation through comparisons with calibration chamber pressuremeter tests conducted in Stockton Beach sand, a new method for the interpretation of pressuremeter testing data is developed based on the proposed solution. This method demonstrates its capability in the back-calculation of the effective horizontal stresses and state parameters for four distinct types of sands.