Liquid-gas responses during rainfall test in MSW landfill

Although rainfall infiltration into landfills is a common phenomenon, the resulting liquid-gas interactions within the waste are highly complex, posing significant challenges to slope stability. To investigate the simultaneous responses of volumetric water content and pore gas pressure to rainfall infiltration, an exploratory simulated rainfall test was conducted at the Changzhou landfill in China. The results revealed that prolonged rainfall initially caused sharp increases in both volumetric water content and pore gas pressure, followed by a gradual stabilization. After the rainfall ceased, changes in volumetric water content and pore gas pressure ranged from 1.8 % to 17.6 % and from 0 to 9.1 kPa, respectively. The variations in volumetric water content decreased with depth, whereas changes in pore gas pressure became more pronounced at greater depths. Rainfall infiltration induced an increase of over 10 % in volumetric water content within shallow buried waste, resulting in a one-order-of-magnitude reduction in gas permeability. This reduction further restricted gas flow, significantly contributing to the rise in pore gas pressure in deeper waste layers. These findings highlight the novelty of capturing the simultaneous responses of liquid and gas phases in the landfill waste, offering insights into the coupled hydro-gas behavior of landfills during rainfall.