Abstract: An approach was presented to assess the basal heave stability of a kind of distinctive excavations——nested excavations which means that a comparatively smallscale excavation must be located in a large-scale one in some special projects. A new formula targeting on calculating the factor of safety against basal heave of nested excavations was developed in this research, grounding on the widely used conventional computing method for the single excavation. The achievement in this paper has been applied in a typical case in which the structure of a metro station of Line 13 lies beneath basement of the Shanghai Natural History Museum and thus they are co-constructed and form the nested excavations. The results demonstrate that the new formula of this paper could reasonably compute the factor of safety against basal heave of the nested excavations.

Key words: underground space, co-construction, nested excavations, stability