IMPACT OF LIQUEFIED SOIL ON SHALLOW FOOTINGS Gonzalo BARRIOS 1 , Xiaoyang QIN 2 , Tam LARKIN 3 , and Nawawi CHOUW 4 ABSTRACT This research addresses the subsurface behaviour of liquefiable sand and its influence on shallow foundations. This was achieved by performing physical experiments. A large laminar box on a shake table was used to simulate the behaviour of the footings-soil system under dynamic loads. The subsurface acceleration and excess pore-water pressure have been measured beneath the footings. Laser displacement transducers were used to record the movement of the laminar layers that constitute the box. The acceleration and settlement of the footings were also measured. Harmonic base motions with different frequencies were applied. Results of the footing in a stand-alone condition (i.e. no adjacent footing) are compared to those from a group of six-clustered footings. The footing on a stand-alone condition showed a larger acceleration for all the frequencies considered, this was also observed at 0.05 m beneath the surface. The settlement showed a strong dependency on both, the frequency content and the number of footings. The acceleration and lateral deformation of the soil beneath the footing were also influenced by the number of footings. All these observations highlight the importance of the effect of shallow footings on the soil response. Keywords: Liquefiable soil; adjacent footings; shear soil deformation; load frequency; shallow footings 1. INTRODUCTION Even though soil liquefaction has been widely studied, the complex geotechnical mechanisms associated are an active research field (Seed, et al. 2003; Madabhushi and Haigh, 2012; Ko, Chen, and Ueng, 2015). Methodologies to assess liquefaction potential (e.g. Seed and Harder, 1990 and Robertson and Wride, 1998) are mainly based on results from in-situ tests (e.g. SPT and CPT) or laboratory tests (e.g. triaxial and direct shear tests). These methodologies have been validated using evidence from real ground motions e.g. Ishihara and Yoshimine (1992). However, these validations considered a free-filed condition neglecting the influence of buildings. Triaxial and direct shear tests also do not consider effects such as the shear deformation and the bearing pressure induced by a building, or a partially drained soil bahaviour. Therefore, other approaches, that include these variables, must be considered to achieve a better understanding of the response of structures. The influence of a building on the response of saturated soils has been studied since the second half of the 20 th century. Yoshimi and Tokimatsu (1977) studied the response of rigid blocks on saturated sand using a shake table. The authors related the settlement with the bearing pressure and the footing width. The mechanisms of liquefaction-induced settlement of buildings were discussed by Dashti, et al (2010). The influence of the shear deformation induced by the building was highlighted as one of the most important parameters. Bertalot, et al (2013), studied a large collection of site evidence of 1 PhD student, Department of Civil and Environmental Engineering, the University of Auckland, Auckland, New Zealand, gbar737@aucklanduni.ac.nz 2 Postdoctoral Fellow, Department of Civil and Environmental Engineering, the University of Auckland, Auckland, New Zealand, xqin009@auckland.ac.nz 3 Senior Lecturer, Department of Civil and Environmental Engineering, the University of Auckland, Auckland, New Zealand, t.larkin@auckland.ac.nz 4 Associate Professor, Department of Civil and Environmental Engineering, the University of Auckland, Auckland, New Zealand, n.chouw@auckland.ac.nz