• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.33-40
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• 2000

The horizontal drain method is one of the soil improvement methods in reclamation works using dredged soils. In this method, plastic drain boards are installed horizontally in the ground, and a seepage pressure or negative pressure is applied through one end of these drains. In this study, a basic consolidation test using horizontal drains was conducted to investigate the effectiveness of this method. The configuration of soil box which was used in this test is 100cm(B)${\times}$100cm(L)${\times}$85cm(H). The drain board was reduced to 25mm${\times}$5mm. The variations in settlement and volume of drain water during the consolidation process were measured, and the distribution of water content and the transpormation of horizontal drain were investigated.

• Geotechnical Engineering
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• v.13 no.1
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• pp.137-146
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• 1997

In this study, a large consolidation test was carried out to estimate the consolidation behaviour of dredged clay ground improved by horizontal drain using plastic board drain with a vacuum pressure. The test results were analyzed by a numerical simulation using potential consolidation theory applied to a hollow cylinder. The rapid decreases in pore pressure and the drain speed in the plastic board indicate that the consolidation occurred quickly after the vacuum state was applied to the test soil. According to the numerical analysis obtained by applying the linear potential consolidation theory to a clay hollow cylinder with external radial drainage, the pore pressure is affected by the strain and the permeability of the soil rather than by the diffusion types. Therefore, measured surface settlement agreed with the numerical solution at the point where consolidation pressure increasing rate u: -0.5. Also the behaviour of the clay layer settlement in the place where the drain was installed was similar to that shown in Barron's consolidation theory. Finally, the design and construction procedure including the selection of the appropriate arrangement of horizontal drains were discussed based on the results of the laboratory tutsts. It is also shown that the potential consolidation theory make it possible to predict consolidation behaviour in the field using horizontal drains exactly.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5C
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• pp.313-320
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• 2008

The discharge capacity testing apparatus using penetration method, being able to simulate in laboratory the condition of embedding plastic board drains in field, was developed to investigate consolidation characteristics of ground and to figure out discharge capacity of drains. The developed apparatus with a mandrel and penetrating device was designed to insert PBD into the ground prepared by previously applied pressure, being different from the conventional testing method that the drain was installed and the ground material was poured subsequently. Discharge capacity tests with the conventional apparatus as well as the newly developed one were performed to assess the applicability of the latter. As a result of tests, the conventional method showed delayed consolidation due to overall disturbance of ground and local deformation of drain caused by inhomogeneity of ground. Therefore discharge capacity of drain with the conventional apparatus was measured more or less larger than the expected values whereas discharge capacity with new one could be measured similar to the actual value in field.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.293-301
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• 2001

This paper is experimental results of investigating the efficiency of horizontal vacuum drainage system. Effects of size and shape of drain on horizontal vacuum drainage were studied. Model tests in the laboratory with soft marine clay were carried out with drain pipe of having three different diameters and PBD (Plastic Board Drain) of strip shape so that consolidation settlement of soft clay due to applied vacuum pressure, amount of discharge, ground settlement and distributions of pore pressure and undrained shear strength were measured during testing. From results of model test, amount of discharge due to vacuum pressure was increased with the diameter of pipe drain whereas the drain efficiency of pipe in per unit area of drain surface was decreased with diameter of pipe. The rate of discharge per unit time was reduced very fast with diameter of pipe. Settlement of ground surface with time was increased with diameter of pipe as a result of increase of discharge to drain pipe.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1165-1172
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• 2006

In this study, an aspect of settlement, developed from different ground improvement method like suction drain method using vacuum pressure and vertical drain method using overburden pressure, was compared each other. In order to analyze settlement tendency of each method exactly, the finite element analysis program was used. The analyses of vertical settlement and lateral displacement for suction drain method and vertical drain method were conducted independently during the solving stage. The initial condition of drainage zone was fixed with 25m depth and 21m width. After the program analyses, the settlement condition had a different tendency with the ground improvement method. Especially, in the results of vertical drain method, the disparity of settlement between the middle of improved zone and unimproved zone. In the case of suction drain method, however, the difference of settlement was smaller than that of vertical drain method.

• Proceedings of the Korean Geotechical Society Conference
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• 1996.03a
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• pp.265-274
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• 1996

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1300-1305
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• 2007

Plastic board drain is one of the methods to reinforce weak soil, and it has been widely used because of economical efficiency, convenience of construction, and ease of quality control. The weight of PBD equipment which places PBD perpendicularly underground in the depth of 40m has to be minimized to obtain convenience installation and movement while standing against press drawing load. In this study, the performance of stability was evaluated with stress distribution at the steel construction of former equipment by structural analysis: And the steel construction which can increase strength while reducing the weight was also presented. As a result of this study, presented construction can obtain more stability by use of the weight 700kg lighter than the former one.

• Geotechnical Engineering
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• v.14 no.6
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• pp.93-112
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• 1998

In the present study, 2-D consolidation theory of the dredged clay by means of the horizontal drain method is proposed. The horizontal drain method to install the drains such as plastic drain board within the dredged clay is a soil improvement method to accelerate the consolidation by expelling pore water in the vertical direction along the horizontal drains. Based on the finite strain consolidation theory by Gibson et al., the partial differential equation of 2-D consolidation due to the horizontal drain is derived. The consolidation due to the horizontal drain can be illustrated from combined self-weight consolidation effect and consolidation effect by horizontal drains. For the prediction of consolidation settlement and degree of consolidation numerical analysis is suggested on the basis of Dufort-Frankel finite differential algorithm. Also, the analytical procedures proposed in this study are verified by the model tests, and the predictions of the consolidation settlement and degree of consolidation are compared with the results obtained from the tests for the dredged clay gathering at Siwha site in Ansan, Korea. For the predictions, the relationship void ratio vs effective stress and the relationship permeability vs void ratio of the dredged clay are obtained from the odometer tests. Additionally, the parametric study for consolidation settlement by variations of design parameters related with horizontal drain method is carried out. Based on the results of the parametric study, design .charts for the preliminary design are also proposed.

• Journal of the Korean Geosynthetics Society
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• v.7 no.4
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• pp.37-45
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• 2008

A pilot test using environmentally friendly drains, was carried out to evaluate their applicability potential in the field. The pilot test site was divided into 5 different areas, with several combinations of vertical and horizontal drains installed for evaluation. Conventional natural fiber drains (FDB), new developed straw drain board (SDB) and plastic drain board (PDB) were used as vertical drains, while sand and fiber mats were used as horizontal drains. Surface settlement rates and excess pore pressure generation/dissipation tendency of PDB and FDB are almost identical except those of SDB. Cone tip resistance obtained from cone penetration test measured at the end of 1st consolidation stage for upper soft layer definitely increased irrespective of types of vertical drains. The monitoring and site investigation test data obtained at the pilot test site prove the vertical natural fiber drains can be used as substitutes of conventional plastic and sand material.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.43-50
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• 2000

In this paper, the consolidation efficiency and the equivalent diameter of the cross shaped drain are examined by using the laboratory test and the numerical model, and the results are compared with those of the band shaped drain. The equivalent diameter of the tested drains is back-calculated from the laboratory experiment and compared with those calculated from the formula suggested in the literature. The efficiency of the cross shaped drain is evaluated by using the 3-D flow program which was validated by the settlement-time test fill data. The results of laboratory test show that the equivalent diameter of the band shaped drain was close to the Rixner's formula and that of the cross shaped drain was fit to the following formula: $d_w\;=\; \\tarc{3}{4}.(b+t)$The results of the numerical analysis show that the cross shaped drain can reduce the consolidation time by 9-10% from that for the band shaped drain. The equivalent diameter obtained from the numerical flow model by using the field data is 3.5 times smaller than that obtained from the laboratory consolidation test.