Abstract
A new microcrack-based continuous damage model is developed to describe the behavior of brittle geomaterials under compression dominated stress fields. The induced damage is represented by a second rank tensor, which reflects density and orientation of microcracks. The damage evolution law is related to the propagation condition of microcracks. Based on micromechanical analyses of sliding wing cracks, the actual microcrack distributions are replaced by an equivalent set of cracks subjected to a macroscopic local tensile stress. The principles of the linear fracture mechanics are used to develop a suitable macroscopic propagation criterion. The onset of microcrack coalescence leading to localization phenomenon and softening behavior is included by using a critical crack length. The constitutive equations are developed by considering that microcrack growth induces an added material flexibility. The effective elastic compliance of damaged material is obtained from the definition of a particular Gibbs free energy function. Irreversible damage-related strains due to residual opening of microcracks after unloading are also taken into account. The resulting constitutive equations can be arranged to reveal the physical meaning of each model parameter and to determine its value from standard laboratory tests. An explicit expression for the macroscopic effective constitutive tensor (compliance or stiffness) makes it possible, in principal, to determine the critical damage intensity at which the localization condition is satisfied. The proposed model is applied to two typical brittle rocks (a French granite and Tennessee marble). Comparison between test data and numerical simulations show that the proposed model is able to describe main features of mechanical behaviors observed in brittle geomaterials under compressive stresses.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 607-619 |
| Number of pages | 13 |
| Journal | Mechanics of Materials |
| Volume | 32 |
| Issue number | 10 |
| DOIs | |
| State | Published - Oct 2000 |
| Externally published | Yes |
Funding
This work was performed during the visit of J.F. Shao to Northwestern University, Department of Civil Engineering from May to August 1999. The financial and scientific support provided by Northwestern University is greatly acknowledged. Partial financial support was provided by the US Department of Energy, Office of Basic Energy Sciences, Geosciences Research Program through Grant No. DE-FG02-93ER 14344/09 to Northwestern University. We are grateful to Wolfgang Wawersik for providing data on Tennessee marble from experiments at Sandia National Laboratories, Albuquerque, NM. The experimental data of the granite were obtained in the framework of the French research project ‘GDR-FORPRO-Géomécanique’ which was supported by the CNRS and ANDRA. This support is also greatly acknowledged. In this section, the procedure for the determination of model parameters is first presented. Then the proposed model is applied to describe the behavior of two typical brittle rocks: a French granite and the Tennessee marble. The French granite was investigated in the framework of the jointed research project ‘GDR-FORPRO’ supported by the CNRS and ANDRA. The purpose was to study influences of induced damage in safety analysis of underground storage of radioactive wastes. Laboratory investigations have shown important microcrack induced anisotropic damage in this material. On the other hand, inelastic behaviors related to microcrack growth and induced anisotropy in Tennessee marble have been investigated by Olsson (1995), Rudnicki and Chau (1996), Rudnicki et al. (1996) .
ASJC Scopus subject areas
- Mechanics of Materials
- Instrumentation
- General Materials Science