Numerical model verification and calibration of George Massey Tunnel using centrifuge models

Abstract

Dynamic soil–structure interaction analyses were carried out for the seismic retrofit design of the immersed George Massey Tunnel, both to predict and study soil liquefaction and related tunnel movements and to design ground improvement. The proposed ground improvement included ground densification using vibroreplacement stone columns along both sides of the tunnel and seismic gravel drains adjacent to the outer edge of the densified zones. The den sification and drainage were proposed to locally mitigate soil liquefaction and reduce displacements of the tunnel to tolerable levels. Centrifuge model tests with base shaking to simulate earthquake effects were conducted to verify and calibrate the numerical models. This included simulating the effects of ground densification and drainage on reme diating tunnel movements. This paper presents the principal results from the dynamic analyses, the centrifuge model design and testing procedure, the class A predictions of the centrifuge tests, and discussions of the centrifuge test results and numerical model calibrations.Key words: immersed tunnel, seismic retrofit, soil liquefaction, design verification, centrifuge testing, numerical calibration.