Abstract
The presence of gas is a widespread phenomenon in marine and coastal soils, often accompanied by complications in engineering application. The characteristics of the gas phase in the pore space are relevant for the assessment of the soil mechanical implications. In granular soils the formation of capillary bridges between the soil particles can invoke cohesive forces. In fine-grained soils gas-induced fractures may weaken the soil structure. Additionally, an excessive gas production leads to a build-up of pore pressures and can thereby trigger a liquefaction failure in granular soils. To enable a differentiated investigation of these features, however, it is vital to look into the inner pore space of a gassy soil. For this purpose, a miniaturised experimental set-up was developed which allows for the documentation of gas bubble nucleation and growth in a soil’s pore space by means of the imaging technique X-ray computed tomography. Herein, gassy soil samples with a stationary grain structure are obtained by means of the axis-translation technique. The degree of saturation is adjusted by a controlled pressure relief. During image processing the three phases — soil particles, pore water and gas — are identified and thus, their interaction can be studied. The microscopic insights gained with the help of this experimental set-up will allow validation or falsification of the basic theoretical assumptions on gassy soils. Furthermore, the data bears great potential for the advancement of approaches for multiphase simulation.
