The response of compact bentonite during a 1-D gas flow test

This report describes the results of a 1-D gas injection test on compact Mx80 bentonite. The test comprises the first dataset for Stage 1A of Task A of the DECOVALEX-2019 programme, which has been designed to improve our understanding of the migration of repository gases through clay-based materials. Over the duration of the testing period, pressurised helium gas was applied to the face of the injection end of the clay sample, and the gas pressure was increased until the entry pressure was exceeded and gas entered the sample. The gas then migrated through the clay and changes in porewater pressure, swelling pressure and flowrate were observed by the instrumentation around the sample. Gas breakthrough occurred as outflow was recorded by the backpressure pump that corresponded with the changes in pressure. The data presented in this study shows that dynamic processes operate within the clay causing differing responses to be recorded on the monitoring instruments. The recorded response of the clay highlights the spatial and temporal development of permeability within the clay sample over the duration of the test.