• Journal of the Korean Geotechnical Society
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• v.25 no.8
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• pp.33-45
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• 2009

The conventional single-core PBDs have been widely used in order to accelerate consolidation settlement of soft grounds. When using the single-core PBD in a thick clay deposit, a delay of consolidation may occur due to high confining pressure in the thick deposit and necking of drains. This study is to compare the performances of soil improvement by the single-core and double-core PBD installed at a site in Busan New Port which exhibits approximately a 40m-thick clay layer. An in-situ test program was performed at the test site where a set of the double-core PBDs and single-core PBDs were installed to compare the efficiency of each drain. In addition, the discharge capacity of each PBD has been measured using the modified Delft Test. A series of laboratory tests for estimating in-situ soil properties have also been performed in order to obtain input parameters for a numerical program ILLICON. The discharge capacity of the double-core PBD is higher than that of the single-core PBD in the modified Delft Test. However it is observed from the comparative in-situ test and numerical analysis that there is no difference in the performance of ground improvement between the two drain systems. This discrepancy comes from the fact that the amount of water released during consolidation in most common field conditions is much smaller than the capacity of even the single core PBD. And thus, considering actual field conditions, it can be concluded that the single-core PBD has enough discharge capacity even in the thick clay deposit such as this test site.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.281-292
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• 2008

Prefabricated Board Drains (PBDs) recently become more widely used than conventional sand drains in improving soft ground because the PBD is more time and cost effective. The performance of PBDs is affected by disturbance in the adjacent soil formation during inserting mandrels, the intrusion of fine particles into filter fabric, and necking of the drain by excessive lateral pressure especially occurring in very deep clay formation such as the Busan New Port site. In this study, the PBD with double-core is introduced, which seems to overcome the shortcomings of usual single-core PBDs. An in-situ test program was established in the Busan New Port site, in which a set of the double-core PBDs and the single-core PBDs was installed to compare the efficiency of each of the drains. The discharge capacity of the double-core and the single-core PBDs was compared for various confining pressures in the modified Delft test and the chamber test. A series of CRS consolidation tests was performed in order to obtain profiles of void ratio-effective stress and void ratio-permeability relationships in the Busan New Port site that are used as input date in performing a numerical program ILLICON. The numerically simulated settlements of ground surface in the test site are in good agreement with those of in-situ measurements. In addition, the performance of the double-core and single-core PBDs has been experimentally and numerically compared in this paper.

• Journal of the Society of Disaster Information
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• v.13 no.4
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• pp.483-490
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• 2017

Recently, the demand for industrial and residental land are increasing with economic growth, but it is difficult to obtain the area for development with good ground condition. Various kinds of vertical drain technologies such as sand drain, sand compaction pile, packed drain, PVD are commercially available to improve the soft ground. Discharge capacity is the important factor of vertical drains. However, under field conditions, discharge capacity is changed with various reasons, such as soil condition, overburden pressure, and so on. In this paper, the experimental study was carried out to estimate the discharge capacity of four different types of PBD, PBD for double core PBD, deep type PBD, X type PBD, general type PBD. Characteristics of the discharge capacity for the surcharge load and hydraulic gradient were analysed. The double core PBD was excellent for discharge capacity in this study.

• Journal of the Korean Geotechnical Society
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• v.25 no.9
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• pp.67-76
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• 2009

The problems of bearing capacity, settlement and shear deformation occur when constructing a structure such as harbor, airport and bridge on soft ground of marine clay, silty clay or sandy soil. Various ground improvement methods are applied to obtain preceding settlement of soft ground and strength increase. In this study, to analyze the applicability of PBD method in deep soft ground, the compound drainage capacity test was operated in comparison with SD. As a result of the test, a minimum drainage capacity of drain material was estimated to be more than $10\;cm^3/sec$ at a more than $400\;kN/m^2$ and less than $5\;cm^3/sec$ at a more than $500\;kN/m^2$ confining pressure in case of single core PBD. In case of double core PBD, it was estimated to be more than $10\;cm^3/sec$ at a more than $500\;kN/m^2$ confining pressure.