Response of Framed Buildings on Raft Foundations to Tunneling

Abstract

This paper investigates the response of framed buildings on raft foundations to tunnel construction using geotechnical centrifuge testing. Five framed building models were considered and the influence of building configuration, weight, eccentricity, and soil density were evaluated. Soil and foundation displacements, frame deformed shape, maximum structure deformation parameters (deflection ratios and angular distortions), and associated modification factors are illustrated. Results indicate that, unlike equivalent isotropic plates, framed buildings primarily exhibit shear behavior and a semi-flexible response. Building deformed shapes indicate that angular/shear distortions (considering bay slope and local tilt) are more appropriate for quantifying framed building distortions than deflection ratios. A relative stiffness parameter is suggested to relate maximum angular distortions to greenfield settlement slope. Moreover, the efficiency of available relative stiffness parameters for the deflection ratio modification factors is confirmed. Limitations of the equivalent plate approach and practical implications of the results for framed buildings are discussed.

Tunneling-Induced Deformation of Bare Frame Structures on Sand: Numerical Study of Building Deformations

“…Traditionally, horizontal strains ℎ are inferred from the displacements measured at the ground surface or at the foundation level, while the bending and shear strains and are related to either the deflection ratio Δ/ (Burland and Wroth, 1974) or the angular distortion (Boscardin and Cording, 1989), as defined in Figure 1. Recently, moving from Cook (1994), Ritter et al (2020) proposed that the deformation parameters of the bay (both average curvature and shear strain) could be inferred from its top and bottom corner displacements, consistent with Xu et al (2020a). More specifically, for framed structures with continuous foundations (e.g.…”

“…This approach can be contrasted with that of the pure bending stiffness based on the Euler-Bernoulli beam theory (Franzius et al, 2006;Goh and Mair, 2014;Haji et al, 2018). The equivalent bending and shear stiffness are typically estimated by analytical methods (Franzius et al, 2006;Finno et al, 2005;Pickhaver et al, 2010) and loading tests, carried out either experimentally or numerically (Son and Cording, 2005;Xu et al, 2020a;Losacco et al, 2014Losacco et al, , 2016.…”

“…For the frame, a simple linear elastic constitutive law was adopted with Young's modulus = 53.8 GPa, Poisson's ratio = 0.334 and unit weight = 27 kN/m 3 . The reduced value of used for the aluminum frame, instead of the standard 70 GPa, was selected to account for the partial welding of the frame components (described earlier); this value of was found by simulating load-deflection tests carried out on the frames (Xu et al, 2020a).…”

“…Later, Son and Cording (2005) normalized the angular distortions of masonry building bays with respect to the differential ground slope obtained in greenfield conditions. By considering that framed configurations with axially stiff slabs/beams in the horizontal direction undergo minimal longitudinal deformations (Finno et al, 2005) and thus shear deformation is dominant, Xu et al (2020a) introduced the angular distortion modification factor and related it to a relative soil-structure stiffness parameter .…”

Role of Footing Embedment on Tunnel–Foundation Interaction

“…In practice, modification factor approaches are often used to predict tunneling-induced structure distortion from greenfield displacements. Xu et al (2020a) and Goh and Mair (2014) presented modification factors of angular distortion and horizontal strains ,ℎ , respectively. For angular distortion, = / is obtained by normalizing the maximum angular distortion within the structures ( ) by the maximum (among all bay locations) average slope of the greenfield surface settlement trough spanning a bay width ( = Δ , , / ).…”