A parametric study of the stability of a vertical cut close to a third party wall foundation

Abstract

Maltese legislation states that a minimum distance of 76cm is kept between the party wall and the face of an excavation but provides no other constraints on any other parameters like the load transfer through the party wall, the excavation height, the level of the water table or limitations arising from the material properties of the ground. The aims of this dissertation are to show that the single value stipulated by local law is insufficient and that there is much more to the problem of excavations than simply allowing for a safe distance. This study presents a parametric analysis comparing the effect of different variables on the safe height of a vertical excavation and the resulting safety factor of the excavation. The variables used include the material's angle of shear resistance and cohesion, the amount of load transferred from the neighbouring building to the ground, the distance of the neighbouring foundation to the top of the excavation cut and the effect of the water level below ground. It is seen that by varying these parameters, the stability of the excavation changed. This proved that a single value describing proximity is insufficient to ensure the safety of all possible situations.