Evaluating the Applicability of a Hypoplastic Constitutive Model for Double-Porosity Fills Undergoing Isotropic and 1-D Consolidation

• Published in: Indian Geotechnical Journal Vol. 54; no. 5; pp. 1834 - 1843
• Main Authors: Mann, L. S., Juneja, A.
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 01.10.2024; Springer Nature B.V
• Subjects: Anisotropy; Clay; Compression; Compressive strength; Constitutive models; Degradation; Engineering; Finite element method; Foundations; Geoengineering; Hydraulics; Mathematical analysis; Mathematical models; Micromechanics; Normal stress; Original Paper; Parameter modification; Parameter sensitivity; Porosity; Slurries; Soil; Soil analysis; Soil degradation; Soil porosity; Soil stresses; Soil structure; Specific volume; Hypoplastic model; Consolidation; Finite element analysis; Double-porosity fills
• ISSN: 0971-9555; 2277-3347
• DOI: 10.1007/s40098-024-00995-6

This paper discusses the finite element analysis of assemblage of clay lumps placed in clay slurry and undergoing compression using a structured hypoplastic soil model. The stress state of the fill was treated as that of a structural clay, which ignores the micromechanics of the complex double-porosity fill. Sensitivity of the fill was used as a numerical parameter to quantify the structure of the fill based on its initial specific volume. In the absence of any strong anisotropy, the above sensitivity was equal to the ratio of the size of the structured state boundary surface and the Roscoe surface. In addition to the five basic parameters used in the modified Cam clay model, this hypoplastic model with its own metastable structure used three more variables to account for the structural degradation. These variables considered the rate of structural degradation, relative importance of shear and volumetric strains, and the soil’s ultimate sensitivity, respectively. The findings were validated by comparing the numerical results to the experimental data of two different clay fills which had undergone isotropic and one-dimensional (1-D) loading. These two stress states are applicable to near surface and thick double-porosity clay fills, respectively. The complete analysis was controlled by the initial specific volume of the fill. Its reconstituted behaviour was achieved only when the imposed normal stress surpassed the preconsolidation pressure of the clay lumps. The controlling variables ranged between 0.37 and 0.75 for the two different clays to model their structure degradation. A parametric study was used to further elaborate on this behaviour. Some discussion on the initialisation of the soil sensitivity is also presented.