• Journal of the Korean Geotechnical Society
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• v.26 no.7
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• pp.71-80
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• 2010

Korea is considered to be a seasonal frozen soil area that thaws in the spring, and freezes in winter. In the current design codes for anti-freezing layer, the thickness of anti-freezing layer is calculated by the depth frozen due to the temperature condition. Therefore, there is a tendency of over-design and applying uniform thickness without the consideration of thermal stability, bearing capacity and frost susceptibility of materials. So, it is essential to study the structural appropriateness of pavement layer and bearing capacity besides the seasonal and mechanical properties of pavement materials to take an appropriate and reasonable design of the road structure. In this paper, the evaluation of frost susceptibility on subgrade, ant-freezing layer, subbase was conducted by means of the mechanical characteristics and model experiment. The temperature, heaving amount, unfrozen water contents and freezing depth of soil samples, the subgrade, anti-freezing layer, subbase soils of road construction site were measured to determine the frost susceptibility.

• Journal of the Korean Geotechnical Society
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• v.23 no.5
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• pp.153-162
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• 2007

For the reinforced earth wall constructed on a soft ground in parallel with replacing soft soils, the behavior of the wall according to variations of thickness and stiffness of soft layer, replacement depth, and wall height is investigated using a finite element method, in which incremental construction steps including consolidation of soft soil layer are considered. The behavior of wall is characterized by investigating displacements and settlements developing at the wall, and shear strains developing in a soil deposit. The stability of wall is, then, evaluated by comparing these values with the safety criteria determined on the basis of the literature. Based on the investigation, it is shown that the behavior of wall is influenced naturally from soft soil thickness(t), replacement depth(d) and wall height(h), but more significantly from d and h. In addition, it is also shown that the normalized replacement depth, d/h, required for the safety of wall is not influenced significantly by the variations of t and h. Consequently, it can be concluded that the proper replacement depth can be suggested in an equivalent value in terms of d/h, even for the cases where the wall height is varying with stations, but the variation is not significant.

• Geotechnical Engineering
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• v.12 no.3
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• pp.35-48
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• 1996

Reinforced soil structures may experience large local movements between soil and reinforcement. The failure modes of a reinforced structure depend on several factors which are governed by deformation and slipping of the reinforcement. In some cases, pulling out of the reinforcement may occur instead of rupturing, The growing use of geosynthetic liner system for storage of solid and liquid wastes has led to a number of slope instability problems where the synthetic liner may undergo a large amount of stretching and slipping as a result of the loading. The conventional finite element model for the soil-reinforcement interface uses a zero thickness joint element with normal and shear stiffnesses and can only accommodate a small amount of deformation. When a large slippage occurs, the model provides an i ncorrect mechanism for deformation. This paper presents a new interface finite element model which is able to simulate a large amount of slippage between soil and reinforcement. The formulation of the model is presented and the capability of the model is demonstrated using illustrative examples.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.11c
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• pp.105-116
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• 1999

The Inchon International Airport site was formed by reclaimed soil from the sea. The average thickness of soft soil Is about 5 m and most of soft soils are normally consolidated or slightly over consolidated. There are many box culverts which are being constructed under the runways in the airfield. Sometimes, differential settlement can be occurred in the adjacent of box culvert or underground structures at the top layer of runway Soil compaction at very near to the structure is not easy all the time. Thus, one layer of geogrid was placed at the bottom of lean concrete layer for the concrete paved runway and at the middle of cement stabilized sub-base course layer for the asphalt paved runway. The length of geogrid reinforcement is 5m from the end of box culvert for both sides. The extended length of geogrid was 2m from the end of backfill soil in the box culvert. The tensile strength tests of geogrid were conducted for make sure the chemical compatibility with cement treated sub-base material. The location of geogrid placement for the concrete paved runway was evaluated. The construction damage to the geogrid could be occurred. Because the cement treated sub-base layer or lean concrete was spread by the finisher. The magnitude of tensile strength reduction was 1.16%~1.90% due to the construction damage and the ultimate tensile strength is maintained with the specification required. Total area of geogrid placement in this project is about 50,000 $m^2$.

• The Korean Journal of Ecology
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• v.25 no.5
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• pp.321-328
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• 2002

In order to provide the basic information for restoration of vegetation, conservation of rare species and maintenance of biodiversity, changes of site factors and vegetation by human trampling disturbance were investigated at the subalpine zone near the peak of Mt. Sorak in Korea. The destructed vegetation was found mainly in the southern parts with gentle slope in this study area. Height and coverage of vegetation and the species diversity decreased, and the community structure depended on trampling strength. Soil moisture, organic matter contents and litter thickness in the site with destructed vegetation by human trampling showed lower values than in the undisturbed site. Soil depth decreased, and gravel exposure on the ground surface increased by soil erosion responded to trampling strength.

• Geomechanics and Engineering
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• v.11 no.4
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• pp.471-492
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• 2016

Underground tunnelling is one of the sustainable construction methods which can facilitate the increasing passenger transportation in the urban areas and benefit the community in the long term. Tunnelling in various ground conditions requires careful consideration of the stability factor. This paper investigates three dimensional stability of a shallow circular tunnel in a layered soil. Upper bound theorem of limit analysis was utilised to solve the tunnel face stability problem. A three dimensional kinematic admissible failure mechanism was improved to model a layered soil and limiting assumptions of the previous studies were resolved. The study includes calculation of the minimum support pressure acting on the face of the excavation in closed-face excavations. The effects of the characteristics of the layers on the minimum support pressure were examined. It was found that the ratio of the thickness of cover layers particularly when a weak layer is overlying a stronger layer, has the most significant influence on the minimum tunnel support pressure. Comparisons have been made with the results of the numerical modelling using FLAC3D software. Results of the current study were in a remarkable agreement with those of numerical modelling.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.3
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• pp.130-139
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• 1993

In order to evaluate the long-term permeability performace of the geotextiles, for five different combination of geotextiles and soils the long-term column test method The results obtained are as follows; 1.The gradient range of the initial stage of the long-term permeability curves varied with respect to the soil types, while that of the final stage varied according to the interaction of the soil/geotextile system. 2.The time required for a given soil/geotextile system to reach a interactive stable stage was measured ahout 100 hours for the standard sand and 150 to 600 hours for the silty content soils, respectively. 3.There were no differences between the plain woven geotextile and the non-geotextile in the long-term permeability performance. 4.As the silt content increased, the long-term performance of the geotextiles decreased, and the limiting silt content was about 15%. 5.The thickness and area density of the geotextiles did not influence on the variation of the seepage quantities. 6.The ayerage slope and the transition time of the long-time flow curve were calculated. 7.In order to evaluate the mechanism of soil/geotextile system more perfectly, the gradient ratio test or the hydraulic conductivity test is required.

• Structural Engineering and Mechanics
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• v.9 no.1
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• pp.69-88
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• 2000

A relatively simple model of a buried structure response to a surface loading that can simulate a possible opening and closure of a gap between the soil and the structure is presented. Analysis of the response of small and medium scale buried roof slabs under surface impulsive loading shows that the model's predictions are in fairly good agreement with the experimental results. Application of the model to a study case shows the relative influence of system parameters such as, the depth of burial, the arching coefficient, and the roof thickness, on the interface pressure and on the roof displacement. This model demonstrates the effect of a gap between the structure and the soil. The relative importance of including a gap opening and closure in the analysis is examined by the application of the model to a study case. This study results show that the deeper the depth of burial, the longer the gap duration, and the shorter the duration of the initial interface impact, while the higher the soil's shear resistance, the higher the gap duration, and the shorter the initial interface impact duration.

• Journal of Soil and Groundwater Environment
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• v.15 no.6
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• pp.53-63
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• 2010

Pneumatic fracturing is an emerging tool to enhance the remediation efficiency of contaminated unsaturated zones by injecting high pressure air and inducing artificial fracture networks. Pneumatic fracturing is reported to be well suited for the cases where the contaminated unsaturated zone thickness is less than 5 m as many contaminated domestic sites in Korea. Nevertheless, there have been almost no studies carried out on the site-specific efficiency and the optimized design of pneumatic fracturing considering the unsaturated zone characteristics of Korea. In this study, we employ numerical simulations to compare the efficiency of pneumatic fracturing on the aspect of the site remediation and the porosity improvement at several hypothetic unsaturated zones composed of four typical soil types. According to the simulation results, it is found that the zone with fine grains soil such as clay and silt shows better efficiency than the zone composed of coarse grains in terms of air flow and porosity enhancements. The results imply that pneumatic fracturing may improve the efficiency of site reclamation by jointly or independently applied to the many contaminated sites in Korea.

• Korean journal of food and cookery science
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• v.17 no.5
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• pp.510-516
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• 2001

Hydroponic cultivation is a technology of raising crops without use of soil. Generally farmers use the method of DFT(deep flow technology)to grow leafy or fruity vegetables; however, systematic and scientific researches are insufficient on this matter. This study investigated the possibility of cultivating Chinese cabbage steadily year long by using the method of DFT. Chinese cabbage was cultivated hydroponically with and without Ge addition, used to prepare kimchi, and the chemical and microbiological characteristics of kimchi were compared. The basic hydroponic cultivation condition was as follows: 30 days after seeding, the raised seeds were moved to a hydroponic bed and given underground water for 3 days so the roots grow normally Standard nutrient solution was provided and the early electric conductivity concentration was maintained between 1.5∼2.5 thickness. The temperature of the solution was maintained between 10 ∼25$^{\circ}C$ to allow the growth of Chinese cabbage. When soil-cultivated, organically cultivated and hydroponically cultivated Chinese cabbages were compared, hydroponically cultivated cabbages were smaller in size and showed less ability to build up and fold leaves into a head, but showed better quality than organically cultivated cabbages. The contents of protein and fat showed no significant differences. The contents of water. Ca, P, Fe, Vitamin A and Niacin were higher in control and Ge-added cabbages compared with soil-grown cabbage. There was no difference between soil-cultivated Chinese cabbage kimchi and hydroponically cultivated Chinese cabbage kimchi.