Measurement of Unsaturated Hydraulic Properties of Municipal Solid Waste

Constitutive models developed for describing the water retention curve (WRC) and unsaturated hydraulic conductivity (K_θ) of soil are parameterized for MSW. Samples of shredded (maximum particle size = 25 mm) MSW were compacted to three dry densities for WRC and K_θ measurement. The water retention curves were measured using the hanging column method. The unsaturated hydraulic conductivities were measured using the multistep outflow method utilizing transient outflow data from the hanging column tests. The measured WRC and unsaturated hydraulic conductivity were used to fit two commonly used constitutive WRC and K_θ models developed for unsaturated soils. The constitutive models were parameterized using non-linear regression to the equilibrium WRC and measured K_θ data. The constitutive models for the WRC and K_θ are capable of reproducing measured WRC and K_θ data when properly parameterized. Root mean squared error water contents (θ_RMSE) ranging from 1–2% were calculated between the measured and modeled WRCs. Unsaturated hydraulic conductivities calculated using the constitutive models were generally within one order of magnitude of the measured K_θ. Parameter estimation for the K_θ functions requires inclusion of K_θ data in the parameter estimation method.