• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.33-41
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• 2017

In this study, the increment effect of safety factor according to increasing of horizontal permeability coefficient is analyzed when geocell is installed on the slope for protection. To evaluate the horizontal permeability and reinforcement effect, the laboratory tests such horizontal permeability test were conducted. According to the laboratory test results, as the porosity rate of geocell increases, the coefficient of horizontal permeability is also increased. And also, regardless of the different types of filled materials, the coefficient of horizontal permeability is improved in a geocell reinforced ground compare with the non-reinforced ground. Laboratory test results and the rainfall intensity were applied to the numerical modeling of slope for seepage analysis and stability analysis of slope by using Soilworks, numerical analysis program. As a result of the slope stability analysis, it is confirmed that the installed geocell on the slope facilitates the drainage of water on the surface of slope. Hence, the ground water elevation is suppressed. Therefore, the safety factor of the slope is increased by the increasing of the internal friction angle, apparent cohesion, and coefficient of horizontal permeability by reinforcing the slope with geocell.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.6
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• pp.111-123
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• 2010

In this study, laboratory model test on utilization of recycled aggregates and crushed stone as horizontal drains to use alternative material of sand in soft ground is practiced. The coefficient of permeability of the recycled aggregates and crushed stone showed largely 1.2~5.1 times and 2.0~3.3 times greater than sand, respectively. The horizontal coefficient of permeability in case of installing the horizontal perforated drain pipe showed largely 1.9~6.8 times more than the case of not installing. The drainage distance showed 1.7~1.8 times greater than sand. When a degree of consolidation is 90 %, there is no delay of consolidation in SCP and PVD improvement sections. Therefore, it is proven that the field applicability is excellent. Also, the suitable quality management criterion is presented to make use of a horizontal drains in soft ground on the basis of analysis of the physical and environmental characteristics.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.31-42
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• 2000

Consolidation and permeability are major engineering properties of soil. In clay, coefficient of permeability and consolidation can be calculated by incremental loading consolidation test. However, it is known that the incremental loading test has several deficiencies including long testing time, non-uniform stress state, very soft clay and problem of back pressure saturation. Specially, it is not performed with horizontal consolidation test. Several methods have been proposed for obtaining reliable values of $C_v$. Among these, the square root of time-fitting method proposed by Taylor(1948) and logarithm of time-fitting method, also called Casagrande's method, are used extensively in soil engineering practice. But these methods are not amenable for the absence of initial linear portion and have the difficulties involved in distinguishing secondary compression from primary compression. Rowecell consolidation tests were carried out in this study with different trimming axis and sample size. The results were compared with those of other methods; Casagrande,$Taylor,\; Casagrande,\; Hyperbolic,\; \delta/t-logt$. From the results, we explained a relationship between horizontal coefficient of permeability and void ratio was obtained. Finally, the directly measured horizontal coefficient of permeability obtained by using the Rowecell was compared with the permeability derived indirectly from the consolidation test result.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.285-292
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• 2010

Recently, it is difficult to find a good soil ground due to the shortage of land for new construction site. Because of this situation, the geosynthetics are commonly used for reinforcing the substructure of the soil ground, and hence improving the bearing capacity and reducing the settlement. The geocell is one of geosynthetics and is the advanced system of geogrid. It is the way to increase earth strength and bearing capacity by using three dimension type of geocomposite. In this paper, the Horizontal permeability was determined with considering various geocell shapes. The permeability test was performed by following method of ASTM D4716(87) and potential filling material for geocell was used. The bearing capacity mechanism which enhances the soil ground with evenly maintaining the degree of the compaction was also analyzed for geocell reinforced ground.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.149-156
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• 2020

Permeation grouting effectively enhances soil strength and decreases permeability of soil; however, the flow of grout is heavily affected by anisotropy of hydraulic conductivity in layers. Therefore, this study investigates the effect of permeability anisotropy on the effective radius of horizontal permeation grout using computational fluid dynamics (CFD). We modeled the horizontal permeation grout flow as a two-phase viscous fluid flow in porous media, and the model incorporated the chemical diffusion and the viscosity variation due to hardening. The numerical simulation reveals that the permeability anisotropy shapes the grout bulb to be elliptic and the dissolution-driven diffusion causes a gradual change in grout pore saturation at the edge of the grout bulb. For the grout pore saturations of 10%, 50% and 90%, the horizontal and vertical radii of grout bulb are estimated when the horizontal-to-vertical permeability ratio varies from 0.01 to 100, and the predictive model equations are suggested. This result contributes to more efficient design of injection strategy in formation layers with permeability anisotropy.

• Journal of Industrial Technology
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• v.27 no.A
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• pp.111-120
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• 2007

This paper is results of experimental research on the effect of application of similarity related to permeability of soil on the consolidation behavior as centrifuge modeling of consolidation is performed with the centrifuge model facility. In this research, the permeability of soil was controlled by changing the viscosity of porewater as the mixed water with glycerin was used during the centrifuge model experiments. The effect of drainage path on consolidation was investigated by installing the vertical drains. A serise of centrifuge model tests with conditions of single vertical and radial horizontal drainage were carried out. Kaolinite and Jumunjin standard sand were used as soft clay and surcharges respectively during tests. For testing condition of single vertical drainage considering similarity of permeability, it was found that consolidation with mixed porewater with glycerin was delayed in comparisons sons with test results with water only. For conditions of horizontal drainage with vertical drains, a low permeability by changing the viscosity of pore water resulted in delayed degree of consolidation at an initial stage of consolidation. But, it predicted not much differences in settlement as long as the consolidation time was sufficiently long enough to finish consolidation. Consequently, it was found that similarity in permeability should be considered to be critical for the case of centrifuge model experiments related to consolidation with long drainage path.

• Korean Journal of Agricultural Science
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• v.40 no.3
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• pp.253-260
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• 2013

In this study, laboratory model test carried out to present the suitable range of particle size distribution and clogging behavior of recycled aggregates and crushed stone as horizontal drains in soft ground. The recycled aggregates and crushed stone showed clogging phenomenon because the top fill material and bottom clay inflow into the horizontal drains. The pp mat was the most effective method to minimize clogging phenomenon. The horizontal coefficient of permeability in case of installing the pp mat showed largely 2.1 times more than the case of not installing. When the pp mat is not installing, the thickness of fine grained soil inflow into the horizontal drains showed 6.7~13.3% range in top fill material and 3.3~6.7% range in bottom clay. Overall, the reduction of the discharge capacity by fine grained soil inflow showed small in recycled aggregates and crushed stone. Also, the appropriate criterion range of particle size distribution is presented to make use of a horizontal drains in soft ground on the basis of laboratory test.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.71-79
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• 2008

Reports about coefficients of consolidation in horizontal direction of marine clays located at seven different sites on western and southern coast area in Korea were reviewed and characteristics of them were investigated. As results of analyses, for relation between the depth of ground and coefficients, any trend and correlation between them can not be found since they are more influenced by the nature of geological formation rather than the depth of ground. Dissipation time t50, one of important factors in estimating value of coefficient of consolidation in horizontal direction, was found to be quite related to them. For the correlation between the maximum pore pressure developed and coefficients, coefficient of consolidation in the horizontal direction tend to decrease with increase of the maximum pore pressure whereas the ground water level or static pore pressure do not have any specific correlation with those coefficients. Values of coefficient tends to increase with values of liquid limit, plastic limit and plastic index and thus they are found to be directly influenced by the contents of fines. Values of coefficient of consolidation in horizontal direction are also increased with increases of permeability in horizontal direction and coefficient of consolidation in vertical direction. They were highly correlated between coefficient of consolidation and permeability in horizontal direction while values of coefficient of consolidation in horizontal direction have a relatively low correlation with values of coefficient of consolidation in horizontal direction. Sometimes, coefficient of consolidation in horizontal direction obtained from field tests were estimated 2-3 times greater than those from laboratory tests.

• Geomechanics and Engineering
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• v.29 no.2
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• pp.145-154
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• 2022

Complex geological conditions have a great influence on the mining of coalbed methane (CBM), which affects the extraction efficiency of CBM. This investigation analyzed the complicated geological conditions in the Liujia CBM block of Fuxin. A geological model of heterogeneities CBM reservoirs was established to study the influence of strike direction of igneous rocks and fault structures on horizontal well layout. Subsequently, the dual-porosity and dual-permeability mathematical model was established, which considers the dynamic changes of porosity and permeability caused by gas adsorption, desorption, pressure change. The results show that the production curve is in good agreement with the actual by considering gas seepage in matrix pores in the model. Complicated geological structures affect the pressure expansion of horizontal wells, especially, the closer to the fault structure, the more significant the effect, the slower the pressure drop, and the smaller the desorption area. When the wellbore extends to the fault, the pressure expansion is blocked by the fault and the productivity is reduced. In the study area, the optimal distance to the fault is 70 m. When the horizontal wellbore is perpendicular to the direction of coal seam igneous rock, the productivity is higher than that of parallel igneous rock, and the horizontal well bore should be perpendicular to the cleat direction. However, the well length is limited due to the dense distribution of igneous rocks in the Liujia CBM block. Therefore, the horizontal well pumping in the study area should be arranged along the direction of igneous rock and parallel plane cleats. It is found that the larger the area surrounded by igneous rock, the more favorable the productivity. In summary, the reasonable layout of horizontal wells should make full use of the advantages of igneous rock, faults and other complex geological conditions to achieve the goal of high and stable production.

• Journal of the Korean Geosynthetics Society
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• v.15 no.2
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• pp.35-44
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• 2016

PET aggregates were produced by mixing heated PET flakes with frictional soils. Using these artificially-made PET aggregates, horizontal drain tests in the laboratory, pilot scale model tests were conducted for the evaluation of the drainage characteristics of PET aggregates. Laboratory horizontal drain tests were conducted under twenty different conditions varying mixing ratios and surcharged pressures. Moreover, by utilizing the aggregates with a mixing ratio producing the lowest variation in terms of permeability against applied load, large scale tests were performed. Reliability of the test results was evaluated from comparison with the results of the laboratory horizontal drain test.