Effects of foundation pressure and building stiffness on tunnel-separated footing interaction

The displacements and deformations of buildings with separated footings caused by tunneling may be significant and could damage the structures. This paper numerically investigates the influences of building stiffness, geometry, and foundation pressure on the deformation of a two-story elastic framed building due to tunneling in sand. An advanced soil constitutive model known as hypoplastic model was calibrated and adopted to simulate the sand behavior. Results show that the roles of building stiffness and foundation pressure on the footing displacements due to tunneling are significant, particularly for a larger tunnel volume loss. An increase in building stiffness reduces both the vertical and horizontal displacements of footings, while a greater foundation pressure primarily increases footing settlements. The influences of building stiffness and foundation pressure on building shear distortion are considerable, while their impacts on panel horizontal strains are minor for the investigated parameter ranges. The results also suggest the potential use of greenfield results as a conservative estimation of the distortion of buildings with separated, embedded footings when subjected to tunneling-induced displacements. Modification factors for shear distortion and horizontal strains are presented and show good agreement with the empirical centrifuge-derived envelopes for buildings resting on the soil surface.