EXPERIMENTAL INSIGHTS INTO INDUCED PARTIAL SATURATION METHODS DEVELOPED FOR LIQUEFACTION MITIGATION: DISTRIBUTION OF GAS BUBBLES

Abstract

Saturated deposits of sandy soils may liquefy during an earthquake event, causing detrimental effects on the site and structures. Mitigation of liquefaction-induced damage is of the essence when the structures are expected to exceed the acceptable limits of safety and serviceability. Induced Partial Saturation (IPS) has been recently proposed as a novel liquefaction countermeasure. In the present study, several laboratory tests were conducted on partially saturated sand models to offer insights into two IPS methods, paying more attention to the distribution of air/gas bubbles entrapped in pore spaces. For this purpose, loose deposits of partially saturated sand were prepared in transparent plexiglass boxes either injecting air or using a chemical substance. Digital images were recorded at different stages of the tests, which provided an opportunity to visualize the distribution of gas/air bubbles. Furthermore, moisture sensors were placed at different locations of sand models, allowing to capture the variation of the degree of saturation with time. Comprehensive analyses of the test data suggested that oxygen bubbles were generated through a reaction between water and chemical substance, and the distribution of oxygen bubbles was sufficiently uniform across the sand models. This method also allowed the preparation of sand models at the desired degrees of saturation. On the contrary, at 1-g injected air was observed to flow through a path of less resistance, and this technique was comparatively less successful in preparing sand models with uniformly distributed air bubbles and at lower degrees of saturation (i.e., below 90%).