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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - LIQUEFACT (Assessment and mitigation of liquefaction potential across Europe: a holistic approach to protect structures / infrastructures for improved resilience to earthquake-induced liquefaction disasters)

Teaser

Summary

1 Introduction
Earthquakes are one of the most destructive natural phenomena. Over the past decade, earthquakes proved to be the deadliest of all European disasters, with almost 19,000 fatalities and economic losses of around â‚¬29 billion. While structural remediation of the built environment against earthquakes has been widely studied, the knowledge about foundation improvement to mitigate the effect of earthquakes is limited and remediation techniques can be very invasive and costly. The most critical effect of the earthquake on foundations and other geotechnical structures is the liquefaction of the soil.
1.1 Earthquake Induced Liquefaction Disasters
Liquefaction is the phenomenon whereby, under seismic loading, a soil loses strength and can no longer support structures founded on it. Further damage can be caused from the resulting settlements.
Recent events have demonstrated that Earthquake Induced Liquefaction Disasters (EILDs) are responsible for significant structural damage and human casualties with, in some cases, EILDs accounting for half of the economic loss caused by earthquakes. The causes of liquefaction are largely acknowledged so the LIQUEFACT project sets out to recognise the factors that contribute to its occurrence, estimate the impacts of EILD hazards and identify and implement the most appropriate mitigation strategies that improve both infrastructure and community resilience to an EILD event.
1.2 Aim and Objectives of LIQUEFACT
The primary aim of the LIQUEFACT project is to develop a more comprehensive understanding of EILDs and the application of mitigation techniques to safeguard small to medium sized critical infrastructures from its effects.
In order to achieve this aim the project identified seven specific research objectives:
Objective 1: Establish an EILD Risk/Resilience Assessment and Improvement Framework (RAIF) to identify vulnerability in terms of physical, social, economic and environmental factors and appropriate mitigation strategies.
Objective 2: Develop a European liquefaction hazard geographical information system (GIS) map framework and methodology for performing localized assessment of liquefaction potential.
Objective 3: Develop new simplified methodologies to assess the vulnerability of infrastructure to EILDs.
Objective 4: Analyse, using geotechnical seismic centrifuge testing and full scale field testing, state of the art liquefaction mitigation techniques suitable for critical infrastructures.
Objective 5: Identify the most appropriate vulnerability, resistance, resilience and adaptive capacity models for Europe and develop a range of performance metrics through which they can be assessed.
Objective 6: Integrate the acquired knowledge and methodologies into a LIQUEFACT Reference Guide (LRG), an easy-to-use software application toolbox, which can be used to make informed assessments on the feasibility and cost-benefit of applying mitigation techniques.
Objective 7: Produce guideline recommendations enabling the EU Structural Eurocodes standards revision task groups to produce new technical standards.

Work performed

2 Progress to date
During the reporting period work has principally been carried out on Objectives 1-5.
Objective 1: Establish an EILD Risk/Resilience Assessment and Improvement Framework (RAIF)
A workshop was held in Bologna to present the LIQUEFACT project to stakeholders in the Emilia Romagna region, Italy. It attracted 205 delegates drawn from engineers, geologists, architects, civil protection and politicians. A questionnaire survey was undertaken to inform the initial development of the RAIF which will be further developed and integrated into a software tool.
Objective 2: Develop a European liquefaction hazard geographical information system (GIS) map.
For the European liquefaction hazard map, the first version of a GIS framework has been developed. In addition, a literature review has been started to construct a catalogue of European historical liquefaction occurrences.
To validate the localised assessment methodology, the ground characterisation at four European testing sites (Emilia Romagna in Italy, Lisbon in Portugal, Ljubljana in Slovenia and the Marmara region in Turkey) has been completed and the results reported.
Objective 3: Development of new simplified methodologies for the vulnerability assessment of structures and infrastructure to EILDs.
Evaluation has started of the existing numerical modelling strategies to simulate liquefaction induced structural damage and to analyse the liquefaction vulnerability of interacting soil-structure systems in the field trials at the pilot testing sites.
Objective 4: Assess liquefaction mitigation techniques using centrifuge modelling and full scale field testing.
This objective involves the testing of soil before and after the application of liquefaction mitigation techniques. A series of small scale centrifuge tests and full scale field tests have been planned to assess the effects of densification, addition of fines and low-desaturation.
Objective 5: Develop a range of European performance metrics to assess vulnerability, resistance and resilience to an EILD event.
A community resilience tool to assess the antecedent and post mitigation EILD resilience of a community and a critical infrastructure resilience tool to assess the impact that such an event would have on the ability of the system to deliver its core services have been developed.
A cost/benefit model of liquefaction mitigation for community resilience will be developed next.

Final results

3 Expected Potential Impact
The current building standards do not fully address the issue of liquefaction and LIQUEFACT will tackle this shortcoming by providing research and demonstration to develop new simplified methodologies and tools. LIQUEFACTâ€™s impact on the innovation capacity will be two-fold.
3.1 Impact of risk/resilience assessment and improvement on stakeholders
A broad variety of stakeholder groups would be interested in the prediction of the likely consequences of an EILD event. These range from individual infrastructure managers to regional government, insurance and civil protection organizations. The RAIF provides the stakeholders with the tools to assess their susceptibility, vulnerability and risks to an EILD event as well as the business modelling tools to evaluate the potential of mitigation options to improve their resilience.
Ultimately the RAIF will be incorporated into the SELENA-LRG software toolbox which will be made available as open source.
3.2 Impact of seismic building codes
Seismic building regulations are strongly connected to earthquake risk assessment. It is important, however, to distinguish between new and existing construction. For new construction, hazard mitigation is embedded in the process of earthquake-resistant design. The current design codes primarily apply to new construction and typically do not include recommendations for the strengthening and rehabilitation of existing structures. The lack of consideration of existing structures in seismic building codes would therefore have a dramatic effect on expected losses during a future seismic event. However, in many parts of the developing world the availability of a proper design code is of greater importance.
LIQUEFACT aims at consolidating the varying knowledge around liquefaction mitigation and here contribute to the convergence of building design codes and the ongoing revision process of the Structural Eurocode.