Correlation between the laboratory and in-situ permeabilities for the embankments

Permeability is one of the major factors of the seepage stability of the embankments such as reservoirs and sea dikes. Seepage through the embankment has many uncertainties due to an application of inaccurate permeability, use of bad construction materials and poor compaction during construction of the embankment. The most important one is permeability that results in seepage problems of embankment. Seepage rate through the embankment and internal erosion increases as the permeability increases. Therefore, the proper assessment of permeability is important when the embankment is designed and maintained and managed. In general, the permeability is usually obtained from the laboratory test. However, it is no doubt that the permeability by laboratory test has some difference with the actual permeability in field. In this study, a series of laboratory tests were carried out with soil obtained from the borrow pits used as construction materials of Hwaong sea dike and in-situ permeability tests were conducted directly on Hwaong sea dike. Its correlation between the laboratory and in-situ permeability values was analyzed. The results show that there were significant differences between the laboratory and in-situ permeability values. In this case, the in-situ permeability values were much higher than the laboratory ones; the in-situ permeability values were α×100∼α×104 (average, α×102) times higher than the laboratory permeability ones. For this reason, the laboratory permeability values were chosen for the design values, the seepage safety factor in embankments could be overestimated. Therefore, for the safety of embankment structures, it should be suggested that the design standard for the seepage safety could be corrected and upgraded to higher level.