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Large scale 1-g shake table model test on the response of a stiff pile group to
liquefaction induced lateral spreading
Réponse d'un groupe de 3 × 3 pieux rigides sous l'action d'un écoulement latéral induit par
liquéfaction étudié à grande échelle sur table vibrante
Haeri S.M., Kavand A., Asefzadeh A.
Department of civil engineering, Sharif University of Technology, Tehran, Iran
Rahmani I.
Marine transportation and technology division, Transportation research institute, Tehran, Iran
ABSTRACT: Evaluation of pile response to liquefaction induced lateral spreading is an important step towards resistant design of pile
foundations against this destructive phenomenon. This paper investigates the response of a stiff 3×3 pile group under liquefaction
induced lateral spreading using large scale 1-g shake table test. The model ground consisted of a 3-layer soil profile including a base
non-liquefiable layer, a middle liquefiable layer and an upper non-liquefiable layer. Different parameters of the response of laterally
spreading soil as well as those of the pile group including accelerations, pore water pressures, displacements and bending moments
were recorded during the shaking that are presented and discussed in the paper. In addition, distribution of lateral pressures due to
lateral spreading on individual piles of the group is investigated in detail. The results show that lateral forces exerted by the laterally
spreading soil vary in the individual pile of the group both in transverse and longitudinal directions depending on the pile position
within the group. It was also found that the magnitude of lateral pressures due to lateral spreading on the stiff 3×3 pile group of this
study are close to the values recommended by the design code.
RÉSUMÉ : L'évaluation de la réponse d'un pieu à l'écoulement latéral induit par liquéfaction est une étape importante vers la
conception de fondations sur pieux contre ce phénomène destructeur. Cet article présent l’étude de la réponse d'un groupe de 3 × 3
pieux rigides en vraie grandeur à 1 g sur table vibrante. Le modèle de sol est composé de 3 couches comprenant une couche centrale
liquéfiable et des épontes non liquéfiables. Différents paramètres de la réponse du sol ainsi que ceux du groupe de pieux, y compris
les accélérations, les pressions interstitielles, les déplacements et les moments de flexion ont été enregistrés pendant l’essai et sont
présentés et discutés dans cet article. De plus, la distribution des pressions latérales de sol dues à l’écoulement sur tous les pieux du
groupe est étudiée en détail. Les résultats montrent que les forces latérales exercées par le sol écoulé varient dans le pieu individuel du
groupe à la fois dans les directions transversale et longitudinale, selon la position du pieu à l'intérieur du groupe. Il a également été
constaté que la valeur des pressions latérales dues au sol écoulé sur le groupe de pieux sont proches des valeurs recommandées par le
code de conception.
KEYWORDS: Pile group, liquefaction, lateral spreading, 1-g shake table test.
1 INTRODUCTION
Liquefaction-induced lateral spreading is commonly observed in
gently sloping grounds or lands ending in free faces as a result
of liquefaction in underlying saturated loose cohesionless
deposits. In these deposits, earthquake-induced excess pore
water pressures can cause a significant decrease in soil shear
strength resulting in ground movement towards downslope or
free face due to existing static shear forces (Kramer and
Elgamal 2001). Lateral spreading can impose significant lateral
pressures on pile foundations. During past earthquakes, several
examples regarding severe damages to piles and structures
supported on them due to lateral spreading have been
documented, among which the cases in the 1964 Niigata
(Hamada et al. 1986), the 1995 Kobe (Tokimatsu and Asaka
1998), and the 2010 Haiti earthquakes (Eberhard Marc et al.
2010) are the most important ones in this respect.
Although some experimental studies including shaking
table, centrifuge and field tests (e.g. Haeri et al. 2012, Motamed
and Towhata 2010, Abdoun et al. 2003, Ashford et al. 2006)
have been conducted to evaluate the response of pile groups to
lateral spreading, but different aspects of the soil-pile
interaction in laterally spreading ground are not yet fully
understood. For example, there are not still enough effective
researches concerning variation of the value and pattern of the
lateral pressures from the liquefied layer against different
individual piles of a group. Motamed and Towhata [10] recently
showed that the lateral spreading force in an individual pile
within a group varies depending on the pile position in the
group. They conducted a series of 1-g shaking table tests on pile
groups behind quay walls in a two-layer soil profile, including a
non-liquefiable layer overlain by a top liquefiable layer, and
showed that in a pile group rear-row piles which are closer to
the quay wall sustain larger lateral pressures, while front-row
piles sustain smaller values.
In this paper response of a stiff 3×3 pile group under
liquefaction induced lateral spreading in a 3-layer soil profile
including a base non-liquefiable layer, a middle liquefiable
layer and an upper non-liquefiable layer is studied. For this
purpose 1-g shake table physical modeling is utilized. Different
parameters of the response of laterally spreading soil as well as
those of the pile group such as accelerations, pore water
pressures, bending moments and displacements were recorded
during the test that are briefly discussed in the paper. The main
focus of this paper is on distribution of lateral soil forces in
individual piles of the group.
