Wenchuan Earthquake Liquefaction Macro-phenomenon And Comparative Analysis Of Field Characterization

Post-earthquake investigation is a fundamental way to gain earthquake knowledge and experience for engineering purpose. Also it is the foundation for seismic resistant design theories and analytical tools. Soil liquefaction is one of the most important factors which caused engineering structural malfunctioned and underground structural damage. Earthquake-induced liquefaction is one of the focuses and frontier topics in geotechnical earthquake engineering. Liquefaction-induced damage phenomena have been observed in many previous earthquakes, e.g., Niigata, Alaska, Kobe, Chi-Chi, Xingtai, Haicheng, Tangshan earthquakes, and the detailed post-earthquake investigation facilitates the development of earthquake engineering and seismic resistant techniques both in China and overseas.The Wenchuan Ms8.0 earthquake which hit Sichuan Province in China on May 12th, 2008 is the most destructive and widely influencing earthquake since the founding of new China. Totally 118 liquefaction points, each of which represents at least a village, have been found, involving an area of about 500km long and 200km wide. The geographical distribution, macro-phenomena, and characteristics of liquefied sites are the basis to understand and acquaint the soil liquefaction caused by Wenchuan earthquake. In-situ investigation and new data collection establish database for future research. However, earthquake-induced liquefaction is determined by ground motions, local soil conditions and environmental factors. Ground motions are different in individual earthquakes, and soil burial conditions and properties will be both different but related. Understanding their commonality and individuality will be beneficial to research on soil liquefaction in Wenchuan earthquake, and also be useful to the overall understanding of liquefaction. The main salient points and achievements of this dissertation include:1. Through systematic field investigation, the paper presents the geographical distribution and characteristics of liquefaction caused by Wenchuan earthquake. Also it analyzes the characteristics of liquefaction macro-phenomena in the major areas, and proposed typical examples. Through typical site investigation tests, the relationship between the jetted materials and the possible liquefied soils are analyzed.2. The geographical distribution and main features of liquefaction- induced damage in the main liquefied regions are given, and are comparatively analyzed. Moreover, the typical phenomena and examples are presented. 3. The paper proposes the in-situ investigation design ideas for Wenchuan earthquake, determines the investigation point locations and distribution, and selects proper indices and testing equipments. By analyzing the typical liquefied sites, macro-phenomenon, damage, survey tests, tests are shown, and the possible common points and analytical results are initially extracted.4. The liquefaction data from the Tangshan, Kobe and Taiwan Chi-Chi earthquakes which have rich and representative liquefaction information are collected. The liquefaction investigation results and characteristics of the three major earthquakes are discussed and outlined.5. The characteristics, including soil burial conditions and mechanical properties, of the liquefied sites from the recent major earthquakes are comparatively outlined and analyzed. The difference and common points are analyzed to grasp the common characteristics and individuality.