Liquefaction susceptibility of fine-grained soils: preliminary study report. Final report, September 1985-March 1986

Abstract : Soil liquefaction, a hazardous ground failure induced by strong motion earthquakes, can cause catastrophic damage to structures such as dams, bridges, power plants, and water-front structures and may involve great losses of life. Examples of liquefaction and resulting damage were observed during the Alaska (1964), Niigata, Japan (1964), and Tangshan, China (1976), earthquakes. Ground failure due to earthquake-induced soil liquefaction may manifest itself as excessive settlement, loss of bearing capacity, sand boiling, and flow slides. The liquefaction potential of clean sands has been studied extensively for the last two decades. However, case histories revealed that liquefied sands were seldom clean. They may contain various percentages of silt or clay or both. In fact, the Chinese observation in the Tansghan earthquake indicated that some cohesive soils may have liquefied. If this indeed had happened, then structures underlain by fine-grained soils, with a marginal safety factor based on the liquefaction criteria normally applied to sands, may actually be unsafe. Thus there is an urgent need for establishing new criteria for the liquefaction susceptibility of soils to include those identified as fine-grained. The author, Professor N.Y. Chang of the University of Colorado at Denver, visited several Chinese agencies and and universities in and near Beijing, China, in the summer of 1985 in an attempt to investigate and verify reported data on the liquefaction of cohesive soils during the Tangshan earthquake of 1976 and to negotiate cooperative research into the problem. This report presents the result of supportive literature review and the findings of the China trip.