Abstract: It is an effective way to replace the soft foundation waste and backfill the low-lying valley with the lumpy waste. In order to explore the consolidation behaviors of saturated lumpy composite backfill foundation, one-dimensional (1-D) consolidation model is established by using the mixture theory. Firstly, based on the assumption of the equal solid strain condition between lumpy soil and filling soil, the formulations are obtained between each constituent strain and pore deformations in lumpy soil and filling soil. Then, under small strain, the 1-D linear elastic constitutive equations for the saturated lumpy composite backfill soil are derived by applying the free energy potential constitutive equations, and the governing equation for 1-D consolidation is provided based on the Darcy's law and the stress equilibrium equation. Meanwhile, its analytical solution is gained by using the separation variable method, and the contrast between the degenerating model and other existing ones shows the validity of the proposed model. Finally, the influences of two pore permeability coefficients and fluid exchange parameter on the characteristics of 1-D consolidation for the saturated lumpy composite backfill foundation are studied by adopting the analytical solution. The analysis results indicate that the permeability coefficient in filling soil plays a leading role in the consolidation behaviors, and the pore pressure in the lumpy soil increases to a certain extent at the initial stage of consolidation and three parameters have the similar mechanism.