Hydrodynamic behaviour of compacted granite sawdust from the dimension stone industry of Pontevedra (Spain): Experimental and Modelling

Two large-scale column experiments have been performed to test the hydrodynamic behaviour of unsaturated, compacted granite sawdust—a material produced during the dressing of dimension stone in Pontevedra (Spain). One of the columns was equipped with psychrometers and capacitance probes while, in the other, a radial array of 80 electrodes made possible a time-dependent 3D electrical resistivity survey. All these devices allowed investigating and modelling the progressive saturation of the material. The study includes a straightforward methodology developed to calibrate the resistivity signals based on standard Proctor-compacted specimens. The progressive saturation of the granite sawdust reveals different stages: initially, an uneven advance of the saturation front (fingering) occurs; later on, this feature vanishes and is replaced by a more regular advance of the saturation front. Numerical analysis of the results shows that the yield capacity of the granite sawdust is*0.39 m3 m-3 and a saturated hydraulic conductivity *2 9 10-6 m s-1. The latter, which corresponds to the specific standard Proctor compaction, is not sufficient to support the use of granite sawdust for compacted-single-layer capping structures. Nonetheless, increased compaction efforts or improved design criteria (multilayer systems or capillary barriers) can keep bearing when considering granite sawdust for this purpose.