Comparative Study of Three Fine Grains Infiltration Techniques to Re–Fill Granular Materials Eroded by Suffusion

With the aim of remediating soils eroded by suffusion, three different techniques were explored and compared at the laboratory scale in this study to effectively infiltrate fine grains into a porous granular filter. In the first technique, which serves as a reference owing to its simple implementation in the field conditions, a pure layer of fine grains is deposited on the upstream side of the filter. However, this technique is found inefficient due to a collective effects between the fine grains which induces formation of surface cake, preventing thus their penetration into the filter. A second technique is therefore proposed in which the fine grains are mixed homogeneously with coarse particles and deposited on the upstream of the filter. Besides, a third technique was designed, where the fine grains are put in suspension in the water seeping through the filter in order to limit their collective clogging. The influence of size ratio and fine grains shape for both the mixture and suspension techniques, and fine grains shape in the case of suspension technique were also explored. For the latter, the cumulative efficiency was further investigated through multiple rounds of infiltration. The results showed that, for a given size ratio between the coarse and fine grains, there is a significant increase in the amount of infiltrated fine grains for the mixture and suspension techniques, that is respectively twice and eight times larger than the value obtained with the reference one, respectively. In the mixture technique, fine grains infiltration is found to increase with the size ratio up to a limiting value whereas, in the suspension method, it decreases as the size ratio increases. Moreover, rounded fine grains are found to infiltrate more easily than angular ones. This work should contribute to improve engineering protocols for achieving deep infiltration through the selection of an appropriate fine grains infiltration technique, with the objective of developing an effective remediation method.