Numerical Investigation of the Effects of Separated Footings on Tunnel-Soil-Structure Interaction

Tunneling-induced horizontal strains for buildings with discontinuous foundations are notable and may pose significant risks to the integrity of nearby structures. This paper presents results from a series of numerical models investigating the response of framed buildings on separated footings to tunnel construction in sand. The study examines a two-story, elastic frame with varying building transverse width, eccentricity, and first story height, subjected to tunneling-induced displacements; footing embedment depth and tunnel cover depth are also varied. Results show that tunneling-induced horizontal displacements for separated footings are significant, with greater footing horizontal displacements occurring at deeper footing embedment depths. Building width and eccentricity also influence soil-footing interaction, particularly in determining the values of footing displacements and the distribution of horizontal strains. An increase in footing embedment depth slightly increases shear distortion but significantly increases horizontal strains. The presented modification factors for angular distortion and horizontal strains align well with empirical envelopes, with the horizontal strain modification factor being sensitive to the relative soil-footing stiffness. This research highlights the importance of considering horizontal strains and realistic foundation embedment depth in the damage assessment for buildings with discontinuous foundations due to tunnel construction.