An analytical study on the boundary size effect of calibration chamber studies

Abstract

Calibration chambers can provide a laboratory-controlled environment and have long been used to study, such as cone penetration tests and pressuremeter tests. However, the finite radial size of the sample that the chamber can accommodate may give rise to the boundary size effect which can influence the test results. When unsaturated soils, especially for soils where suction hardening is present, are concerned, the effect of suction on the boundary size effect is unknown. This study presents a new cavity expansion solution in unsaturated soils of finite radial extent, with which the boundary size effect can be quantified. The solution is formulated for spherical cavities subjected to two boundary conditions under the drainage condition where the contribution of suction to the effective stress is constant. It is found that samples with a higher suction value are under more influence of the boundary size effect and this is more obvious with higher mean net stress and higher void ratio.