Re: Enclosure (1): Summary of discussion items of circular no. 1
Thank you Japan for your statements. Here are our comments:
1.1 b) A note on Liquefaction
In 1975, at the 5th Panamerican Conference of Soil Mechanics held in Buenos Aires, Argentina, Arthur Casagrande - Professor emeritus, Harvard University, Cambridge, MA, USA, and Fabian Guerra of Sept-Iles, Qc, Canada, presented and discussed Papers and Liquefaction.
Casagrande discussed a cutting-edge CRITICAL REVIEW ON LIQUEFACTION AND CYCLIC DEFORMATION OF SANDS; he defined the term "liquefaction" as follows:
1. ACTUAL LIQUEFACTION - what was simply called "liquefaction" before the development of cyclic laboratory tests. It is the response of loose, saturated sand when subjected to strains or shocks that results in substantial loss of strength and in extreme cases leads to flow slides.
2. CYCLIC LIQUEFACTION - the response of a test specimen of dilative sand to cyclic loading in a triaxial test when the peak pore pressure rises momentarily in each cycle to the confining pressure.
Guerra discussed a methodology to realistically determine the liquefaction potential of coarse textured free-draining and fine-textured relatively impermeable materials. He drew attention to the relationship between moisture content, density and degree of saturation.
Guerra also indicated that various tests with Iron ore concentrates showed that no FLOW CHARACTERISTICS are apparent unless the minus 200 mesh (finer than 0,074 mm) fraction exceeds 3.8 percent.
In 1976, at the ASCE National Convention held in Philadelphia, PA, USA, dealing with Liquefaction Problems in Geotechnical Engineering, H. Bolton Seed, Professor at the University of California, presented and discussed a State-of-the-Art Paper titled EVALUATION OF SOIL LIQUEFACTION EFFECTS ON LEVEL GROUND DURING EARTHQUAKES.
Seed described the following qualifications of the term "liquefaction" used in his presentation:
a. "Liquefaction": denotes a condition where a soil will undergo continued deformation at a constant low residual stress or with no residual resistance, due to the build-up and maintenance of high pore pressure which reduce the effective confining pressure to a very low value; pore pressure build-up leading to true liquefaction of this type may be due either to static or cyclic stress applications.
b. "Initial Liquefaction": denotes a condition where, during the course of cyclic stress applications, the residual pore water pressure on completion of any full stress cycle becomes equal to the applied confining pressure; the development of initial liquefaction has no implications concerning the magnitude of the deformations which the soil might subsequently undergo; however, it defines a condition which is a useful basis for assessing various possible forms of subsequent soil behavior.
c. "Initial Liquefaction with Limited Strain Potential" "Cyclic Mobility" or "Cyclic Liquefaction":denotes a condition in which cyclic stress applications develop a condition of initial liquefaction and subsequent cyclic stress applications cause limited strains to develop either because of the remaining resistance of the soil to deformation or because the soil dilates, the pore pressure drops, and the soil stabilizes under the applied loads.
Some ten additional papers on Liquefaction were presented and discussed at this ASCE National Convention.
Since then, a plethora of papers - too abundant to enumerate, had been presented and discussed at various conferences and conventions.
