Deformation of an excess spoil fill subjected to infiltration and groundwater seepage is simulated with a matric-stress critical state model. The model includes groundwater and elastoplastic soil constitutive relationships and is formulated in terms of fluid head and net stress plus matric stress, where matric stress is the stress generated by matric suction. Results of the simulation are presented in terms of the pore-water pressure distribution, phreatic surface, shear strain distribution, and settlement at selected points on the fill.