Gassy sands: volume change induced by organic matter oxidation

Most traditional laboratory techniques to prepare gassy soils inject carbonated water into a soil sample while the latter is mounted on a triaxial chamber, and subsequently produce gas by lowering confining stresses below the gas/liquid bubble point. This study introduces an experimental technique to prepare gassy soil analogues by in-soil oxidation of organic matter (native and foreign to the soil) by way of chemical reaction with diluted hydrogen peroxide, which avoids the bubble-point dependence. Sand specimens reconstituted at varying relative densities and organic matter contents were prepared in an instrumented modified oedometer. In-soil oxidation of organic matter was induced by adding hydrogen peroxide into the water-filled void space, thus producing free gas bubbles. The evolution of volumetric strain and pore water electrical conductivity under drained conditions were monitored during all experiments. Results demonstrate that this technique successfully allows the preparation of gassy coarse-grained soil analogues in the laboratory.