Primary Study On Liquefaction In Bachu-Jiashi Earthquake

Liquefaction is one of the typical damages caused by earthquakes. Investigation of liquefied sites is the basic source of methods for estimating liquefaction potential. At present, the empirical methods for estimating liquefaction in aseismic design codes adopted in China is based on several major earthquakes occurred 30 years ago in China, thus the feasibility and applicability of the methods need to be verified in different geological conditions.Bachu-Jiashi earthquake (Ms6.8) which occurred in 2003 caused wide soil liquefaction. Except for the meizoseismic zone, areas which were 40km North-East to the epicenter and 50km North North-West to the epicenter have been observed with severe liquefaction phenomena, resulting in damage to farmland, roads and buildings and collapse of river and canal banks. Which is the most severe liquefaction after Tangshan, Haicheng earthquake nearly 30 years.The main contents and achievements of this dissertation include:(1) It describes the research progress and achievements on soil liquefaction, and introduces Bachu–Jiashi earthquake and earthquake-induced liquefaction. Also it explains the research significance on liquefaction and proposes scientific questions.(2) It collects the existing survey data of Bachu–Jiashi earthquake, and compares the liquefaction phenomena with those in Tangshan, Haicheng earthquakes to obtain the knowledge of liquefaction characteristics and hazard in Bachu–Jiashi earthquake.(3) The existing geological data is collected and compared with those in Tangshan, Haicheng earthquakes to obtain the knowledge of geological characteristics of liquefied sites in Bachu–Jiashi earthquake.(4) Investigation of liquefied sites in Bachu area was conducted. The principles to select liquefied sites and non-liquefied sites were determined. Selecting proper indices and equipments, multi-index tests were completed in 41 sites. The reliability of the results is assured by analyzing typical profiles.(5) Using the data of multi-index tests and site histograms, the depths of liquefied soils are determined. The characteristics of soil conditions are analyzed and compared with those in previous earthquakes. Using the standard penetration test data, the formula for estimating sandy soil liquefaction employed in" Code for Seismic Design of Buildings GB50011-2001" in China is verified. The results of successful judgments are discussed.