An effective thermal conductivity model for bentonite based on meso homogenization techniques

An effective thermal conductivity model is presented based on the basic solution of ellipsoidal matrix-inclusion problem using homogenization techniques. This model integrates well the effects of the shape, volume fraction, space distribution of inclusion and the interaction between inclusion and matrix on the effective thermal conductivity. The anisotropy of conductivity, which is mainly induced by the aspect ratio of inclusion and the ratio between conductivity of inclusion and matrix, is also included in the model. On this basis, by characterizing the geomaterials as heterogeneous media composed of solid matrix and embedded ellipsoidal voids, the influences of void shape, porosity and saturation degree on the effective thermal conductivity are discussed. Finally, the proposed model is used to predict the effective thermal conductivity of Gaomiaozi bentonite(GMZ01); and the predicted results are compared with the experimental data and the predictions by other models. The results show that the proposed model has a better predictive capability for the effective thermal conductivity of the GMZ01 bentonite. Given the complex pore structure of the bentonite, multiscale homogenization techniques should be used to yield more accurate predictions. The research results may provide a helpful reference for better understanding the coupled thermo-hydro-mechanical behaviors of buffer materials for the high-level radioactive waste disposal.