Parameter variability of undrained shear strength and strain using a database of reconstituted soil tests

Mair E W Beesley, Paul Joseph Vardanega
2019 Canadian geotechnical journal (Print)  
General rights This document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: ABSTRACT During construction, the mobilisation of undrained shear strength must be limited to avoid soil failure. Soil strains must be controlled to avoid compromising structural serviceability. To assess foundation performance by strength mobilisation, an understanding of soil strains at various levels of
more » ... h mobilisation is required. In practice, ground investigation data is often limited, and assessment of the expected variation of stress-strain and undrained shear strength is improved with empirical correlations calibrated with a database. The new database RFG/TXCU-278 contains data of 278 consolidatedundrained triaxial tests on reconstituted fine-grained soil samples compiled from the literature. Analysis of the database to evaluate the variability of undrained strength ratio (c u /' v0 ) and a reference shear strain with shear mode is undertaken in this paper. The new database provides evidence that shear strain (like undrained shear strength) is sensitive to the consolidation (isotropic or K 0 ) and shear mode (triaxial compression or extension) applied in the test. For the materials included in the database, the strength mobilisation parameters obtained from a triaxial compression test can be used to predict the corresponding triaxial extension parameters to a reasonable accuracy. Prediction of soil strains at increments of stress ratio or mobilisation level cf. BSI, 1994) allows engineers to better evaluate foundation performance. For this purpose, the Mobilisation Strain Framework (MSF) is a convenient model for characterising nonlinear stress-strain from undrained shear test data (Vardanega and Bolton 2011; Vardanega et al. 2012). Whether a simple hand calculation or a more advanced numerical model is used, checking the possible range of ground movements at any mobilisation level requires the selection of representative design parameters which are often determined by experiment. If a test is representative of the site,  ref (a reference strain parameter) controls undrained foundation settlement at 50% mobilisation.
doi:10.1139/cgj-2019-0424 fatcat:kdfgak7lrzaspbojyeoheelks4