The preservation or restoration of any structural typology requires understanding of the load transfer mechanism under the influence of external actions. Scarce literature on the structural behaviour of existing dry stack stone corbelled arches and vaults has motivated the present study. The objective of the study is to have a better understanding on the failure mechanisms of corbelled vaults under different types of support movement, e.g. translations and rotations, both lateral (inward and outward) and vertical and the in-plane and out-of-plane directions. The current paper examines the in-plane behaviour under relative outward lateral spreading of the support. A test setup is specially fabricated for evaluating these lateral support movements in dry stone corbelled vaults. The prototype of the test model chosen for study is one of the existing entrance vaults of Ta Prohm Temple, Cambodia restricting to the bare arch form, a 2D representation. The angle of repose of a typical vault varies between 45 to 60°. The arch considered here is of 56° of angle of repose. Digital photogrammetric technique has been utilized in the study to capture the deformed geometry, which has proved to be very useful in monitoring the displacements of the rigid blocks. From the study it is concluded that these corbelled arch systems under relative in-plane outward support movement tend to fail by overturning inwards because of the rocking failure being dominant over sliding by virtue of the structural configuration, and available sliding friction. © 2019, RILEM.