The main overall objective of the SOMEF project is the investigation of the role of soil fabric on the foundation of Critical State Soil Mechanics theory, the incorporation of the results of this investigation into a new enhanced formulation of the theory and the illustration by examples of fabric effects on constitutive modeling and numerical analysis of problems in geomechanics.
Largely different views exist among various research groups in theoretical and applied soil mechanics as to the relevance of fabric in regards to the foundation of CSSM theory. The consequences are not only of academic interest but they extend to the heart of applications in the forefront of geomechanics where the principal tool of modern analysis, constitutive and numerical modeling, depends on the CSSM framework in a fundamental way. This is the strong motivation behind the present project.
In pursuing this overall objective several intermediate methodological objectives must be met as follows:
1. Appropriate definition of a fabric tensor and determination of its value at critical state.
2. Uniqueness of the critical state value of fabric tensor, or possible dependence on loading history.
3. Effects of fabric tensor on the location of the classical Critical State Line (CSL) in the e-p space.
4. Formulation of an objective rate equation of evolution of fabric tensor from initial to critical state value.
5. Enhancement of current critical state conditions on e and • by the critical state value of the fabric tensor.
6. Investigation and illustration of fabric tensor effects on the constitutive response of soils.
7. Numerical analysis of bvp in geomechanics under various loadings, with and without fabric effects.
NOTE: All the above objectives will be addressed separately for sands and clays, aiming at a unified description but also accounting for the physical differences of their interparticle interaction.
The research plan of SOMEF will include complementary experimental, numerical and analytical methods of investigation. In more concrete terms the investigation includes the following set of seven research actions (or Work Packages), each one of which aims at a specific task (or Work Tasks) addressing one or more of the aforementioned particular objectives:
Task A (DEM) – Fabric measurements of particulate aggregates by DEM (AS: sands; AC: clays)
Task B (X-R CT) – Fabric measurements of particulate aggregates by X-Ray CT
Task C (Fabric F) – Fabric tensor and its evolution
Task D (Lab Exp.) – Triaxial, biaxial, and hollow cylinder experiments on sand samples
Task E (CSSM) – Fabric-enhanced CSSM
Task F (Const. Mod.) – Effects on constitutive modeling
Task G (Num. Anal.) – Numerical analysis of boundary value problems in Geomechanics