Papers by Keyword: Representative Elementary Volume

Abstract: A Hydropower Station is located in the middle reach of the Dadu River in southwest China. The natural slope angles are generally 40°~65° and the relative elevation drop is more than 600m. Complex different fractures such as faults, dykes and dense fracture zones due to unloading are developed. Many abutment slopes were formed during construction of the abutments. The stability of these steep and high slopes during construction and operation period plays an important role for the safe construction and operation of the hydropower station. According to the statistical distribution of joints and fractures at the construction site, the slope is divided into a number of engineering geological zones. For each zone, a stochastic fracture network and a numerical model which is close to the real state of the fractured rock mass are established by the Monte-Carlo method. The mechanical response of fractured rock masses with different sizes of numerical models is studied using FLAC3D. The REV characteristic scale is identified for rock masses in the slopes with stochastic fracture network. Numerical simulation is performed to obtain the stress-strain curve, the mechanical parameters and the strength of the jointed rock mass in the zone. A constitutive relationship reflecting the mechanical response of the jointed rock mass in the zone is established. The Comparison between the traditional method and the method in this paper has been made at the end.

Abstract: A hydropower station is located in the middle reach of the Dadu River in southwest China. The natural slope angles at the project site are generally 40~65 and the relative elevation drop is more than 600m. Complex different fractures such as faults, dykes and dense fracture zones due to unloading are developed. The stability of these steep and high slopes during construction and operation period plays an important role for the safe construction and operation of the project. According to the statistical distribution of joints at the construction site, the slope is divided into a number of engineering geological zones. For each zone, a stochastic fracture network and a numerical model are established by the Monte-Carlo method. The mechanical characters of fractured rock with different sizes are studied using FLAC3D. The REV characteristic scale is identified for rock masses. Numerical simulation is performed to obtain the mechanical parameters and the strength of the jointed rock. With the numerical model and the site monitoring data, a self-developed stochastic mechanical analysis software is applied for back analysis and stability assessment.

Abstract: The experimental Electron Probe Micro Analysis (EPMA) characterizations on the MOX fuels evidence a heterogeneous microstructure, containing several phases. This heterogeneity must be accounted for in the numerical simulation. The first phase of this work, presented here, concerns exclusively the numerical representation of the MOX microstructure in three dimensions. Three identified steps were realized. The first one consisted in the acquisition and the treatment of two-dimensional experimental pictures thanks to a soft-ware already developed [1]. From the made treatments, the following bi-dimensional data were acquired: the surface fraction of every phase, the various diameters of inclusions within a phase as well as their surfaces fractions. However, within the framework of our study, we wished to represent our heterogeneous microstructure in three dimensions. Except, the data, supplied by this soft-ware, were bi-dimensional. Therefore, the second step of our works deal with the stereological domain. The model of Saltykov [2] was used to go back up the two-dimensional statistical information in three-dimensional. Finally, the last step of our works was to develop a tool able to build a meshed periodic numerical representation of the MOX microstructure. This innovative tool, based on a Random Sequential Absorption technique, represents MOX fuels already irradiated in reactor or any heterogeneous fuels envisaged in the future as well. For example it models two or three phases MOX fuel or any multi-phases fuels as well. Moreover, the sizes of the inclusions can vary within each phase. At the moment, the tool models spherical inclusions but nothing prevents from evolving towards more complex morphologies.