9-10 September 2019, Greenwich, London NUMERICAL SIMULATION OF OBSERVED LIQUEFACTION PHENOMENA FROM THE 2011 CHRISTCHURCH EVENT Silvia BERTELLI 1 , Diego MANZANAL 2 , Susana LOPEZ-QUEROL 1 , Tiziana ROSSETTO 1 , Pablo MIRA 2 , Sonia GIOVINAZZI 3 , Rob RUITER 4 Abstract: Soil liquefaction at the ground often cause damages to various infrastructure assets. Its consequences have been widely made evident by the performance of the Telecommunication Network Services during the 2010-2011 Canterbury Earthquake Sequence (CES) which stroke the Canterbury region in New Zealand. Despite the relevance of loss of functionality of the telecommunication system, especially during the post-event recovery phase, studies in the literature on the network performance about damages due to liquefaction are still limited. Exploring an unprecedented database of in-situ geotechnical inspections collected after the CES, this research first compares alternative empirical liquefaction-triggering models available in the literature with observation maps. Then, a soil column profile is evaluated adopting a constitutive model based on generalised plasticity (‘modified Pastor-Zienkiewicz’) through a Finite Element based home-developed code. The obtained results from the numerical models are finally cross- checked with the empirical analyses, the existing liquefaction investigation maps and field observations collected in the aftermath of the CES. Introduction Large-scale urban infrastructure networks are highly susceptible to liquefaction. Buried lifelines failures due to floatation or differential settlements are often recorded on telecommunication, electric power, and water and wastewater systems (Maurer et al., 2015; Chian et al. 2012, 2014). For instance, in the aftermath of 22nd February Christchurch Event (New Zealand), Telecom investigations reported many utility holes partially floated out of the ground or filled with water in areas where there was severe liquefaction. The majority of faults were recorded on the copper network in the liquefied areas (Tang et al., 2014). The telecom infrastructure was robust enough and required limited maintenance procedures for its restoration compared to other systems. Nonetheless, the impact of the liquefaction on the network can still be observed from the utility holes left uplift after almost ten years since the event (Figure 1). Regarding the Mw=6.2 Christchurch earthquake itself, the event was induced by a strike-slip rupture, centred 10 km to the southeast from the Central Business District (CBD) at 5-6 km depth. Due to its shallow depth and proximity to the CBD, very high ground motions were registered by the 33 recording stations placed around the Canterbury region. Liquefaction manifestations, including the significant sand boilings, slumpings and ground settlements observed, are one of the most extensive and severe ever reported worldwide (Taylor, 2015). 1 EPICentre, Department of Civil, Environmental and Geomatic Engineering, University College London, London, WC1E 6BT, UK 2 Department of Continum Mechanics and Structures, ETSI Caminos, Canales y Puertos, Universidad Politecnica de Madrid, Spain 3 Department of Civil and Natural Resources Engineering, University of Canterbury, Christchurch, New Zealand 4 Manager Network Protection, Chorus, Christchurch, New Zealand