Abstract：Gas permeability of municipal solid waste(MSW) is an important parameter for the analyses of landfill gas migration. The laboratory measurement of gas permeability was carried out on the MSWs taken from the Qizishan landfill in Suzhou City，China. The measurement was performed with a purposely-designed lysimeter. The influences of void ratio，degree of saturation and MSW composition on gas permeability were investigated. The test results show that the gas permeability of the MSW ranges from 10－8 m2·Pa－1·s－1 to 10－5 m2·Pa－1·s－1，and the corresponding intrinsic permeability is between 10－13 m2 and 10－10 m2. For a given composition and degree of saturation(Sr = 0% or 40%)，gas permeability was found to increase exponentially with void ratio of the MSW. For a given composition and void ratio(e = 2.0)，a bilinear relationship was observed between gas permeability and degree of saturation. The degree of saturation corresponding to the division point(i.e. Sr = 50%) was slightly less than that corresponding to the field capacity of the MSW. When the degree of saturation is greater than the division point，gas permeability decreases exponentially with an increase in the degree of saturation. However，at the low range of degree of saturation(i.e. Sr≤50%)，the influence of Sr on gas permeability is not so significant. When the samples have the same void ratio as well as degree of saturation，it is unexpected to find that the gas permeability of the MSW increases with fill age.
