This contribute analyses the collapse mechanisms of a circular masonry arch supported on rectangular slender abutments when subjected to an imposed settlement of one support in addition to self-weight, using the principle of virtual work and thrust line analysis. Depending on the angle of settlement and the slenderness of the arch and the abutments, the study identifies the main hinging failure mechanisms where the hinge configurations depend mainly on the angle of the settlement and the slenderness of the arch. An extensive analysis shows the different possible collapse mechanisms of masonry buttressed arches with different type of support settlements