Abstract：To investigate the effects of retaining wall and interface strength on translational failure of landfill along the underlying liner system，a three-part wedge analysis is used to calculate the safety factor for the waste mass against possible translational failure. The landfill can be divided into three discrete parts：an active wedge lying on the back slope that tends to cause failure；a passive wedge；and retaining wall resting on the foundation or liner system that helps to resist failure. With the change of the interwedge forces，the upper and lower bound solutions for the landfill stability，i.e. FSmax and FSmin，can be readily determined. Using an average safety factor FSave to replace the true factor FStrue，the differences between FSave and FStrue are within 5% for all cases considered. The safety factors increase with the increase of the height of retaining wall and the friction angle beneath the retaining wall. It is found that the retaining wall affects significantly the stability of landfill，if not consider the retaining wall，the stability analysis of landfill is relatively conservative. A potential failure phase with a minimum safety factor cannot simply be determined by comparison of the values of inner friction angles and cohesions for a multilayer liner. The safety factor increases with the increase of inner friction angle and cohesion of the liner interface. The cohesion of the liner interface seriously affects the safety factor，especially for a liner interface with inner a low friction and high apparent cohesion.
