The liquefaction phenomenon. A brief academic report.

Abstract
In this academic report, the liquefaction phenomenon is described briefly. The historical develop of the liquefaction research is mentioned, and the mechanism of liquefaction phenomenon is addressed in simple way. The report is merely descriptive and scientific content is supported by the references given. Field and laboratory methods commonly to use in the liquefaction evaluation are summarizing. In addition, in regular detailed a simplified process to carry out the liquefaction susceptibility evaluation, is given. Finally the liquefaction affecting factors are mentioned and briefly commented.
Keywords: Flow liquefaction, cyclic mobility, pore-water pressure, liquefaction strength, undrained cyclic loading test


I. Introduction
In general, the geotechnical earthquake damages are very dangerous and quite difficult to evaluate and prevent. The liquefaction phenomenon is one of the more important and interesting geotechnical earthquake problems. This phenomenon occurs, mainly in loose and medium dense saturated sands. The loading process can be cyclic, as in the case of an earthquake, or monotonic, as in the case of a slope failure (Bonita, J. 2000).


From historical aspects, the liquefaction phenomenon became really interesting topic in scientific community and designer engineers after the two big earthquakes occurred in 1964. Firstly the Good Friday earthquake (Mw=9.2) in Alaska, USA, followed by the Niigata earthquake (Ms=7.5) in Niigata, Japan. In both earthquakes, the geotechnical damages widely occurred, especially damages induced by liquefaction were spectacularly produced (Kramer, S. 1996).

Although the liquefaction phenomenon importance was recently recognized (after 1964 earthquakes mentioned above), the term “liquefied” to refer to the large strength loss of soil was used by first time by (Hazen, A. 1920) in reference to the 1918 failure, due to engineering flaws, of the Calaveras Dam in California (Rogers, J.D. 2002), while (Terzaghi, K. 1925) originally introduced the term liquefaction into the engineering community in the classical book Erdbaumechanik, and, in 1936 (Casagrande, A. 1936) used the term to explain the massive soil failures at the Fort Peck Dam

More recently, the liquefaction damages have widely produced by the more powerful earthquakes occurred in the beginning of the present decades, for example (Orense, R. et al. 2011) analyzed the liquefaction damages produced by the recent earthquakes on Cantebury, New Zeeland (September 4th, 2010; February 22nd and June 23rd, 2011) and (Martinez, D. 2011a) described a liquefaction-induced damages on Itako city, Japan by the 2011 off the Pacific coast of Tohoku Earthquake on March 11, 2011*.

In this academic report the liquefaction phenomenon is explained briefly, first the mechanism of soil liquefaction is approached, then, the testing method of liquefaction strength is described and finally some comments related to the factors affecting the soil liquefaction, are added. In addition, simple comments are given, and conclusions as well.


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Aerial view of leaning apartment houses in Niigata produced by soil liquefaction and the behavior of poor foundations. Most of the damage was caused by cracking and unequal settlement of the ground such as is shown here. About 1/3 of the city subsided by as much as 2 meters as a result of sand compaction. 


Photo Credit: National Geophysical Data Center

Source: USGS