Gas injection test of remolded saturated soil with consolidation

Abstract

Investigation of gas migration in saturated soil is of great theoretical and practical significance in marine science and engineering. The transport of gas bubbles in soil and its effects on soil physical and mechanical properties can be further studied. Gas injection and permeability tests were conducted using a self-developed oedometer with gas injection and water infiltration. Before the gas injection test, the remolded saturated soil was consolidated in an oedometer device to an effective vertical stress of 100 kPa. Gas injection tests were then performed to investigate the transport mechanism of bubbles in saturated soil and the changes in water permeability after gas injection. The results show that it is difficult for gas to migrate through capillary invasion and fracturing from the pore scale owing to the high gas entry pressure in fine-grained sediments. Hence, initial gas migration mechanism in pore scale is elastic-plastic expansion. The scale of cavities expands from micron to millimeter during gas injection, and gas pressure for fracturing reduces with the expansion of cavities. The fracturing initiated in millimeter scale and gas invades further into the soil. Interconnections of cavities and cracks resulting in an increasing of drainage rate and coefficient of permeability.