Figure 6.
The graph shows cumulative inflow plotted against time in days for samples B C 2, B C 3 A, B C 3 B, and B C 4, along with equivalent value from Jacobs et al. 2020 and diffusion in free water. B C 2 shows a gradual decrease from 0 to about minus 0.2 millilitres over about 14 days, while B C 3 A decreases from about minus 0.05 to about minus 0.42 millilitres. B C 3 B shows a fluctuating decrease reaching about minus 0.4 millilitres, and B C 4 decreases from 0 to about minus 0.3 millilitres. The equivalent value line shows a steady decreasing trend, while diffusion in free water shows a sharp decrease reaching about minus 0.6 millilitres within about 2 days.Cumulative inflow curve showing steady-state sections of data normalised to a common time and volume, showing volume loss due to gas diffusion through Boom Clay samples. Dotted lines represent linear regression of the data, the gradient of which is used in Equation 7 to calculate the diffusion coefficient Equation 9. The yellow line is the equivalent response for diffusion of gas in water (i.e. assumed to be 6.7 × 10−9 m2/s taken from the Engineering toolbox, 2025). The grey line is the equivalent response from Jacops et al. (2020) and is based on the average values for diffusion into Boom Clay (i.e. 4.82 × 10−10 m2/s)