in which, for idealized porous media with a rigid and undeformable skeleton structure (i.e., without variation of total volume ( V T ) when the water content of the sample changes (no expansion or swelling with the wetting of the sample); nor contraction or shrinking effect after drying of the sample), the total (or bulk) volume ( V T ) of an ideal porous material is the sum of the volume of the solids ( V S ) and the volume of voids ( V V ):