Liquefaction Risk Research Articles

Liquefaction of Thawed Layers in Frozen Soil

A dynamic effective stress method is presented for assessing the liquefaction potential of thawed layers of saturated cohesionless soils sealed between frozen surface layers and permafrost. Such layers are common in Arctic regions. Analysis indicates that the liquefaction potential is increased by the presence of a frozen surface layer. The pore-water pressures created by dynamic stress gradients are redistributed upwards to regions of lower effective stresses, and they cannot dissipate because drainage is sealed off, thus leading to increased liquefaction potential. Within limits yet to be established, the coarser the soil, the greater the risk of liquefaction at low densities as upward redistribution of pore-water pressures is facilitated by increased permeability. Field data on liquefaction from the Alaska earthquake of 1964 are examined, and they appear to support the conclusions.

Risk Analysis for Ground Failure by Liquefaction

A risk analysis has been developed for studying the likelihood of earthquake-induced ground failure by liquefaction. In this analysis, a new empirical method for evaluating the liquefaction potential at a site is employed. The method is based on interpretation of case histories in terms of earthquake magnitude and hypocentral distance. Employing this method, the probability of liquefaction at a site, as a function of earthquake magnitude and hypocentral distance, is first evaluated and then integrated over all magnitudes and distances of interest to obtain the total overall annual probability of liquefaction at the site. An example study is included in which the overall risk of liquefaction at a site is evaluated.

Problems in the Fill Construction Using Coal Ashes

Special attention must be paid to the fill construction where coal ashes are used because they have particular geotechnical properties.Coal ashes are sandy coarse silt and have no plasticity. They have such small specific gravity as 2.1. Compacted coal ashes have strong shearing resistance at the optimum moisture content, but loose coal ashes have the risk of liquefaction when they are saturated.In Hisasue valley in Kawasaki city, an extensive flow slide of fill construction where coal ashes were used occurred in June, 1965. The fill consisted of loose dumping ashes and it collapsed just when it had been saturated by the seeping groundwater to the critical state.In Hodogaya in Yokohama city, a large fill construction has been built with coal ashes with special attention paid to the drainage of groundwater and to the compaction of fill material. The work has proved a success.

Zoning For Soil Liquefaction At Catania City(Italy)

The city of Catania has been destroyed in the past by many earthquakes and particularly by the 1169 earthquake with XI MCS intensity, the 1693 earthquake with X MCS intensity and the 1818 earthquake with VIII MCS intensity. In the framework of a research programme finalised to the definition of a seismic scenario for the city of Catania, the seismic event occurred on January 1693, having a return period of about 300 years has been chosen as scenario earthquake. For this earthquake a Richter magnitude M = 7.3 and a maximum ground acceleration O ax = 0.35g (estimated). Different existing methods for the evaluation of the liquefaction potential index have been applied to several sites of the city of Catania where standard penetration test results were available. The results presented in this paper show that there is a reasonable agreement among the employed procedures and also that, based on the limited available amount of data, only in the site of San Giuseppe La Rena the liquefaction risk is high.