• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1383-1387
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• 2005

사면의 식생이 초기에는 강우에 의해서 표면흐름, 지하수위 증가, 지표수의 침윤에 의해서 성장이 될 수 있으나, 시간이 경과함에 따라 식생에 의한 사면의 안정성을 확보 하는 데에는 큰 영향을 미치지 못한다. 즉, 사면의 식생을 복우언시켜 식물근(뿌리)에 의해서 사면을 안정화 시키기 위해서는 사면의 위치, 고도 및 방향 등에 따라 적응할 수 있는 식물의 선택과 성장에 충분한 수분을 보습할 수 있는 구조의 사면계획과 구조물 설치가 필수적이다. 본 연구에서는 절$\cdot$성토면에서 경사면의 붕괴를 방지하고 식생을 복원하는 방법으로 Mattress Gabion을 제안하였다. 정형화되고 유연성 있는 다공성 Mattress 구조를 통한 식생의 복원은 사면의 안정과 환경친화적인 목적을 모두 만족할 수 있었다. 특히, Gabion 근고공이 설치된 이후에 공극이 큰 Mattress 구조물을 중심으로 식물의 뿌리를 지반에 직접 연결하거나, 식생 활착이 어려운 암반 절취 사면에서도 Mattress 옹벽을 통해서 식물이 양질의 흙에 직접 활착할 수 있도록 설계한 사면 Mattress의 경우는 사면의 안정성 증대와 아울러 지하수의 표면흐름과 투수 및 침윤에 의한 식물의 성장피해를 최소화하고 시간이 지날수록 식생에 의해서 Mattress Gabion 옹벽이 내구성과 유연성을 유지할 수 있었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.3
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• pp.197-205
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• 2004

The relationships were studied between the range of hardening zone and the intensity of vacuum pressure in case of applying vacuum consolidation drainage method for soil improvement. A testing apparatus was made to measure the range of hardening zone varying the water content and the intensity of vacuum pressure for 3 different the highly compressible dredged clays(Gwangyang, Busan and Mokpo). In case of applying high vacuum pressure, the hardening zone is not spreaded as compared to low vacuum pressure because of the clogging of drainage and developed hardening zone near the drainage.

• Current Research on Agriculture and Life Sciences
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• v.2
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• pp.98-108
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• 1984

Generally, in case of constructing the embankments on the soft clay layers, one-dimensional consolidation settlement under the assumption of a middle position stress in a single layer makes a great difference with the integral value, ie. the final settlement. Consequently, to find how many equal segments of the soft clay layer are needed to converge into the integral value and which position should be taken as a position of mean stress, authors compared the theoretical value of the settlement due to one-dimensional consolidation with the practical value of the settlement due to two dimensional consolidation. The obtained results are as follows. 1) The practical value of the two-dimensional consolidation settlement can be estimated by the 74-83% theoretical value of the one-dimensional consolidation settlement. 2) When the soft clay layer was cut into 8-16 equal segments according to the depth, one-dimensional consolidation settlement converge into the integral value. 3) Assuming a total soft clay layer as a single one, the depth of a mean stress position is 0.29-0.37 of the thickness of the total soft clay layer. 4) The Hyperbola Method which presumes the long-term settlement from the short-term practical value of settlement is credible, because all practical value of the settlement are in safe side of the standard error of estimation and the correlation coefficient is up to 0.95.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.918-927
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• 2008

The problems associated with constructing high-speed concrete track embankments over soft compressible soil has lead to the development and/or extensive use of many of the ground improvement techniques used today. Drains, surcharge loading, and geosynthetic reinforcement, have all been used to solve the settlement and embankment stability issues associated with construction on soft soils. Geosynthetic-reinforced embankment supporting piles method consist of vertical columns that are designed to transfer the load of the embankment through the soft compressible soil layer to a firm foundation and one or more layers of geosynthetic reinforcement placed between the top of the columns and the bottom of the embankment. In the paper, the evaluations of a seismic performance of geosynthetic-reinforced embankment piles for a ultra soft ground during earthquake were studied. the equivalent linear analysis was performed by SHAKE for soft ground. A seismic performance analysis of Piles was performed by GROUP PILE and PLAXIS for geosynthetic-reinforced embankment piles. Guidelines is required for pile displacement during earthquake. Conclusions of the studies come up with a idea for soil stiffness, conditions of pile cap, pile length and span.

• Journal of the Korean Geosynthetics Society
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• v.13 no.1
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• pp.71-83
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• 2014

Busan is located at the mouth of Nakdong River and if an earthquake occurs, it is very likely that the damage by the earthquake will be worse as liquefaction can happen in the sand layer, builtup soil, and landfill ground due to amplification in the lower sedimentary layer that is well developed in the river mouth. Therefore, this study first examined the possibility of liquefaction in the replaced sand layer under breakwater using 14 earthquakes in 5.6-7.9 scale and artificial earthquakes including the seismic wave suggested in the standard specifications for seismic design of ports and fishing port facilities to evaluate the stability of breakwater which is the primary protective structure for port facilities against earthquakes. Second, analysis on characteristics of the seismic energy and acceleration response spectrum by size of earthquake was performed to suggest the most appropriate size of seismic wave for the condition in Korea. Third, finite element analysis was performed using the suggested seismic wave to study the characteristics of earthquake by finding the dynamic lateral displacement of breakwater and verifying the stability of structure and the displacement and forces occurring at geotextile. Results of the study showed that the possibility of liquefaction in the landfill and replaced sand layer, the dynamic lateral displacement of breakwater, and changes of geotextile are greatly affected by the subsurface ground (replaced sand layer).

• Journal of the Korean Geotechnical Society
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• v.30 no.6
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• pp.51-59
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• 2014

Shallow landslides and debris flows are a common form of soil slope instability in South Korea. These events may be generally initiated as a result of intense rainfall or lengthening rainfall duration because of the effects of climate change. This paper presents the evaluation of rainfall-induced natural soil slope stability and reinforced soil slope instability under vertical load (railway or highway load) throughout South Korea based on quantitative analysis obtained from 58 sites rainfall observatories for 38 years. The slope stability was performed for infinite and geogrid-reinforced soil slopes by taking an average of maximum rainfall every ten years from 1973 to 2010. Seepage analysis is carried out on unsaturated soil slope using the maximum rainfall at each site, and then the factor of safety was calculated by coupled analysis using saturated and unsaturated strength parameters. The contour map of South Korea shows four stages in 10-year-time for the degree of landslide hazard. The safety factor map based on long term observational data will help prevent rainfall-induced soil slope instability for appropriate design of geotechnical structures regarding disaster protection.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.5-14
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• 2013

Coarse granular geomaterials containing large gravels are broadly used for construction of large geotechnical systems such as dams, levees, railways and backfills. It is necessary to evaluate deformation characteristics of these materials for dynamic analysis, e.g. seismic design. This study presents evaluation of dynamic deformation characteristics of coarse materials using large scale resonant column testing apparatus, which uses specimens with 200 mm in diameter and 400 mm in height, and the effects of gradation characteristics on maximum shear modulus, shear modulus reduction curve and damping characteristics were investigated. From experimental study using rock-fill materials for a dam, we could see that the largest or mean particle size affects the shape of shear modulus reduction curve. When the specimens are prepared under the same conditions for maximum particle size, the coefficient of uniformity affects the confining stress exponent of maximum shear modulus. It could be concluded that the maximum particle size is an factor which affects shear modulus reduction curve, and that the coefficient of uniformity is for small strain shear modulus, especially for the sensitivity to confining stress.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.213-220
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• 2011

Fines such as silt or clay are usually mixed with granular particles in natural or reclaimed soils which are slightly cemented. Such fines contained within weakly cemented soils may influence permeability and also mechanical behavior of the soils. In this study, a series of unconfined compression tests on weakly cemented sands with fines are carried out in order to evaluate the effect of fines on unconfined compressive strength (UCS) of cemented soils. Two different cement ratios and fine types were used and fine contents varied by 5, 10, and 15%. Two types of specimens were prepared in this testing. One is the specimen with the same compaction energy applied. The other is the one with the same dry density by varying compaction energy. When the same amount of compaction energy was applied to a specimen, its density increased as a fine content increased. As a result, the UCS of cemented soils with fines increased up to 2.6 times that of one without fines as an amount of fines increased. However, when the specimen was prepared to have the same density, its UCS slightly decreased and then increased a little as a fine content increased. Under the same conditions, a UCS of the specimen with silt was stronger than the one with kaolin. As a cement ratio increased, a UCS increased regardless of fine type and content.

• Journal of the Korean Geosynthetics Society
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• v.9 no.1
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• pp.47-57
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• 2010

Granular soils having a large particle size have been used as a filling material in the construction of foundation, harbor, dam, and so on. Consequently, the shear behavior of this granular soil plays a key role in respect of stability of structures. For example, soil particle crushing occurring at the interface between structure and soil and/or within soil mass can cause a disturbance of ground characteristics and consequently induce issues in respect of stability of structures. In order to investigate the shear behavior according to an existence and nonexistence of particle crushing, numerical analyses were conducted by using the DEM (Discrete Element Method)-based software program PFC2D (Particle Flow Code). By dividing soil particle bonding model into crushing model and noncrushing model, total four particle bonding models were simulated and their results were compared. Noncrushing model included one ball model and clump model, and crushing model included cluster model and Lobo-crushing model. The combinations of soil particle followed the research results of Lobo-Guerrero and Vallejo (2005) which were composed of eight circles. The results showed that the friction angle was in order of clump model > cluster model > one ball model. The particle bonding model compared to one ball model and noncrushing model compared to crushing model showed higher shear strength. It was also concluded that the model suggested by Lobo-Guerrero and Vallejo (2005) is not appropriate to simulate the soil particle crushing.

• Journal of the Korean Geosynthetics Society
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• v.21 no.1
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• pp.11-21
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• 2022

In this study, the individual vacuum seepage consolidation method, a new soft ground improvement method, was developed to supplement the conventional suction drain method (individual vacuum preloading method) and the geotechnical behavior was predicted through numerical analysis. If the individual vacuum seepage consolidation method applied, the effect of accelerating settlement and increasing the amount of settlement was high when the aquifer was located in the middle or at the bottom of the layer to the target improvement layer. It was found that the pumping amount in the aquifer does not affect the settlement behavior when it exceeds a certain level. Even vacuum pumping wells were installed in various locations, such as inside or outside of the embankment, the difference in settlement and horizontal displacement was insignificant. In addition, it was predicted that the settlement rate was the fastest and the horizontal displacement (inward) was large when both methods were carried out at the same time. Since this method can reach the target settlement amount very quickly, it was confirmed that it is possible to increase the spacing of vertical drain, thereby securing economic feasibility.