Abstract
A simple approach to estimate sidewall friction in reinforced soil model experiments conducted in parallel-sided test boxes with unlubricated walls is proposed. Analytical solutions are developed for reinforced soil slopes and retaining walls subjected to self-weight or external loading. It turns out that the frictional effect depends on the shape of the failure zone and the value of friction coefficient between soil and a sidewall material. The theoretical predictions were verified in laboratory experiments in a test box with lubricated and unlubricated sidewalls. It was shown that the method can be used to estimate sidewall friction not only under failure conditions, but also under all stages of surcharging prior to failure.