Liquefaction Characteristics Of New Zealand2011Earthquake And Test Of The Existing Liquefaction Evaluation Methods

The worldwide seismic activities have been quite frequent since the1960s,especially the1964Niigata earthquake caused severe saturated sand liquefaction andground failure, the Alaska earthquake brought about more than10,000km2sandliquefaction, as well as the1976Tangshan earthquake induced24,000km2sandliquefaction. Saturated sand liquefaction attracts more and more attention recently. Thephenomenon caused by earthquakes often leads to serious disasters, such as surfacesubsidence, road damage, house cracking or tilting, dam instability, etc. Therefore,further study on liquefaction mechanism, its influence factors and how to accuratelyevaluate the liquefaction potential is particularly vital. The rationality and reliability ofliquefaction evaluation methods has strong influence on seismic safety and the cost ofengineering structures, thus it becomes an important research direction of soil dynamicsboth at home and abroad, which has always been highly valued by scholars andengineers.Liquefaction evaluation methods which are widely used both at home and abroadnow have certain limitations, and many problems need to be solved for the liqueficationevaluation of deep sand particularly. The MW6.2earthquake which struck Christchurch,New Zealand in February22,2011provides a good opportunity to explore new rules ofliquefaction and assess the existing liquefaction evaluation methods. This earthquake isthe first one in recorded survey in which the massive liquefaction acts as the main causefor seismic damage, and it creates conditions for further understanding of liquefactionmechanism, to test assess the existing liquefaction evaluation methods and to developnew evaluation methods.This paper collects liquefaction survey data of the New Zealand earthquake,together with a large number of post-earthquake in-situ investigation test data,summairizes the liquefaction characteristics of this earthquake, and gives comparativeanalysis of both domestic and abroad evaluation methods based on SPT and CPT,evaluating the applicability and reliability of different methods.The main work and research results include:1. Through referring to relevant survey data, to understand the earthquake historyand plate tectonics characteristics of New Zealand, get the distribution of liquefied areasand detailed liquefaction damage infomation, and preliminarily analyze the reasons forthe large-scale liquefaction.2. To introduce the use of standard penetration test (SPT), static cone penetrationtest (CPT) and other in-situ testing techniques adopted in the investigation, and todetermine the liquefied/non-liquefied layers through field survey data.3To conduct comparative analysis of the liquefaction features, including peakacceleration, sand burial depth, groundwater level, sand density, particle sizedistribution, etc., so as to get the basic features of these factors in the New Zealand earthquake.4. To give comparative analysis of eight SPT-based evaluation methods,including seven from Chinese codes and the Seed simplified method. Using theliquefaction survey data of the New Zealand earthquake to test the above-mentionedeight methods, then evaluate their applicability and reliability.5. To provide comparative analysis of three CPT-based evaluation methods,including the one from Chinese code, two foreign ones, Robertson method and Olsenmethod. Using the liquefaction survey data of the New Zealand earthquake to test theforementioned three methods, then evaluate their applicability and reliability.