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The causes of apparent overconsolidation in the Namak marine deposit, Korea

2007; ICE Publishing; Volume: 57; Issue: 4 Linguagem: Inglês

10.1680/geot.2007.57.4.355

1751-7656

Jeong-Yun Won, Ping Chang,

Geotechnical and construction materials studies

An intensive experimental study was carried out to investigate the causes of the overconsolidation phenomena in the Namak New City site, Korea. Geological events in conjunction with sea level changes, groundwater fluctuation, weathering, leaching and cementation were examined as possible causes of overconsolidation. In addition to oedometer and triaxial tests, radiocarbon dating, geochemical components and pore water chemistry were analysed. It was shown that the overconsolidation in the upper marine clay deposit was not caused by stress reductions such as erosion and groundwater fluctuation. Furthermore, weathering or leaching seemed unlikely. The apparent overconsolidation can be explained by cementation, which is indicated by profiles of the sulphate and potassium ion concentrations in the pore water. At the early stage of the Holocene marine deposition, the rate of deposition was 4·4 mm/yr; thereafter it was reduced to 1·4 mm/yr, controlling chemical processes such as sulphate reduction and ion exchanges and, in turn, apparent overconsolidation. Some mechanical and chemical properties of the apparent overconsolidated clay were compared with the geologically overconsolidated Palaeosol layer in the site.