The translational failure along liner system at bottom and back slope often happened in municipal waste landfill. The composite failure through the body of waste filling and bottom slope is other failure mode. The relative calculation method of slope stability in landfill for composite failure mode must be modified based on the current stability analysis method. For composite failure

it is assumed that failure surface in waste filling is in Coulomb’s active situation and safety factor is identical at all points on the composite failure surface. On the limit equilibrium of rigid body

a new stability analysis method for composite failure is presented. The stability of a slope and Kettleman Hills’s landfill slope are calculated by the new method and two wedges method. The calculation results show that safety factor obtained by two wedges method for dangerous translational failure is higher than that by the above new method. The most dangerous slide failure surface is composite failure surface. For the Kettleman Hills’s landfill

the composite failure surface is possible sliding failure surface. It can be found that the composite failure is one of the possible failure modes. The composite failure mode must be considered for slope stability safety analysis of landfill.