• Journal of Korean Society of Forest Science
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• v.31 no.1
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• pp.37-42
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• 1976

In this study, an effort was made to find out more effective methods for vegetation establishment on denuded forest land along Cheon Bo Mountains, This area has serious sheet erosion as a major erosion process and parent material is granite gneiss which is known as one of the most erosive materials. Lespedeza bicolor, Arundinella hirta and Robinia pseudoacacia were used as ground cover species. Seeding methods were open broadcast seeding and broadcast seeding with straw mulch, dill seeding with 10cm and 20cm width, and spot seeding with 20cm and 30cm diameter. 1. On slopes less than 30 degrees, broadcast seeding method with straw mulch was the most effective way to establish vegetation cover. 2. On steep slopes more than 30 degrees, 10cm drill seeding method was more effective than the other methods. 3. Soil Texture has an influence on vegetation establishment governing soil moisture condition. Coverage and fresh weight were increased with the fine material qantity in soil. 4. In process of year, coverage was increased with fresh weight. On the other hand, survival decreased.

• Journal of the Korean Geotechnical Society
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• v.31 no.1
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• pp.15-24
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• 2015

This paper presents the results of a reduced-scale physical model investigation into the effect of drilling fluid with different mix designs for bore hole collapse prevention. The bore hole collapse prevention mechanism for the bentonite based drilling fluid was first discussed together with the effect of conditioning with different additives on engineering characteristics of bentonite based drilling fluid. Reduced-scale model tests were then carried out considering field procedures for cases with a decomposed granitic soil with 20% fines and a sand with various drilling fluids with different mix designs. The results indicated that the addition of polymer to the bentonite based drilling fluid decreases the amount of drilling fluid injected, the drilling fluid infiltration thickness and increases the final depth of excavation. Also revealed is that the effect of polymer on the performance of drilling fluid is more pronounced in the decomposed granite soil with 20% fines than the sand. Practical implications of the findings from this study are discussed in great detail.

• Journal of the Korean Geosynthetics Society
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• v.14 no.4
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• pp.11-21
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• 2015

The method to replace asphalt and cement is needed to reduce the carbon emission on road. Polymeric material which is light and easy to handle while having complex function with less carbon emission would be highly effective when it replaced soil pavement containing cement. This study is intended to identify the usability of soil pavement containing organic solidification agent only through the field test. Pavement on bike trail still satisfied required bearing capacity coefficient in 3 months. Pavement after passing 1.6 bil units of bike through pavement acceleration test that simulated a long-term serviceability during a short-time still remained unaffected, demonstrating a long-term serviceability of soil pavement.

• Journal of the Korean Geotechnical Society
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• v.32 no.1
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• pp.19-33
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• 2016

Stability analysis based on the limit equilibrium method combined with the result of infiltration analysis is commonly used to evaluate the effect of rainfall infiltration on the slope stability. Soil is a three-phase mixture composed of solid particle, water and air. Therefore, a fully coupled mixture theories of stress-deformation behavior and the flow of water and air should be used to accurately analyze the process of rainfall infiltration through soil slope. The purpose of this study is to study the effect of interaction of air and water flow on the mechanical stability of slope. In this study, stability analyses based on the coupled hydro-mechanical model of three-phases were conducted for slope of weathered granite soil widespread in Korea. During the process of hydro-mechanical analysis strength reduction technique was applied to evaluate the effect of rainfall infiltration on the slope stability. The results showed an increase of air pressure during infiltration because rain water continuously displaced the air in the unsaturated zone. Such water-air interaction in the pore space of soil affects the stress-deformation behavior of slope. Therefore, the results from the three-phase model showed different behavior from the solid-water model that ignores the transport effect of air in the pores.

• Journal of the Korean Geographical Society
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• v.36 no.3
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• pp.217-232
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• 2001

One of the molt debatable Issues on geomorphological study in Korea should be the discussion over the formation process of gent1e slope surfaces on the piedmont area. In this study, the characteristics of spatial distribution and the formation process of geomorphic surfaces were investigated by classifying the alluvial fans as three geomorphic surfaces alluvial the Bulguksa fault-line The fan surfaces, distributed along the west slue of Bulguksa Mts, consists the confluent alluvial fans continuously along the N-S direction The surfaces of Sincheon-Hyomun district juxtaposed to the Ulsan Bay must be infulenced by sea-level chance during the Quaternary Taken together, these observation suggests that the major four factors contributed to the fan formation 1) rather longer freeze-and-thaw cycle during the Glacial period. 2) the steep mountain slope along the west side of Bulguksa Mts.. which had been resulted from the horizont stress of EAst Sea 3)the tectolinear fault system developed by structural movement along the Bulguksa Fault-line valley. and 4) the erosion-labile characteristics of bedrock In this urea which is consisted of the Bulguksa granite and the sedimentary rock formed in Cretaceous period.

• Journal of the Korean Society of Costume
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• v.50 no.7
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• pp.47-58
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• 2000

Prime Minister Kim tart-song is said to have built this cave temple in the tenth year of the reign of King Kyongdok-wang(742-765) of Unified Shilla(751). The numerous stone Buddhist images in the grotto represent the best Buddhist figure of the Unified Shilla period and of all Korea. The Sokkuram Grotto is composed of the main hall, entrance to the main chamber and antechamber in space. The main hall beyond the small antechamber is round and the ceilling is domed. Within the rotunda sits a majestic Buddha(Amitabha), 3.48m in height and 2.6m in width, carved in granite and facing east. Surrounding the main Seated Buddha are eleven-headed Avalokitesvara Bodhisattva, Manjusri Bodhisattva and the other three Buddhist images, Ten disciples, Buddhist figures in the ten Niches in relief. An eleven-headed Avalokltesvara Bodhisattva of boundless mercy is sculptured on the wall behind the main Seated Buddha. Further guarding the Buddha are ten standing Arhans of the Disciples of Buddha. Next, two Devas. one on each side, stand guard. Two Bodhisattvas are the saints who are next to the Seated Buddha in importance, also one on each side. And, There are ten niches around the dome. They contain seven seated Bodhisattvas and one Vimalakirti(the name of a famous lay disciple of the Buddha). Two niches are empty. Consequently, there are total thirty-eight Buddhist images in the Sokkuram cave temple. The Buddhist images have been reguarded as masterpieces of Buddhist art and Shilla culture of Unified Shilla in the eightth century. The Buddhist images are represented very dear, elegance and beauty of detail skill

• Journal of the Korean GEO-environmental Society
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• v.7 no.3
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• pp.31-41
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• 2006

The scale effect of specimens on the shear behavior of joints is studied by performing direct shear tests on six different sizes in Granite. The peak and residual shear stress, shear displacement, shear stiffness, and dilation angle are measured with the different normal stress(0.29~2.65MPa) and roughness parameters. It is also shown that both the joint roughness coefficient(JRC) and the joint compression strength(JCS) reduce with increasing joint length. A series of shear tests show about 56~67% reduction in peak shear stress, and about 18~44% in residual shear stress, respectively as the contact area of joint increases from 12.25 to $361cm^2$. Also the variation of dilation angle is $27^{\circ}$ at normal stress of 0.29 MPa and $6^{\circ}$ at normal stress of 2.65 MPa, respectively. The envelopes considering scale effect for JRC are made for the peak shear strength of rock joint in comparison with the Barton's equation.

• Journal of the Korean Geosynthetics Society
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• v.14 no.3
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• pp.43-51
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• 2015

In seasonal frozen areas which have a temperature difference in the winter and spring season like south korea, if stiffness reduction by repeated freezing and thawing occurs to slopes adjacent to private facilities or mountain slopes, safety factor is insufficient to design criteria and landslide could be occurs due to rainfall or snowfall. It can lead to large damage of human life and property. In this study, in order to examine the safety changes of mountain slopes by repeated freezing and thawing, soil samples series of SP and SM by USCS distributed in surface soil of mountain slopes were collected for specimens. Through the direct shear test, the characterestics of frozen soil shear strength were analyzed and by utilizing numerical methods, chracteristics of strength reduction of weathered granite soil according to repeated action of freezing and thawing, changes in the stability of the slopes when applying freezing and thawing of the soil samples were examined. As a result, the maximum shear stress decreased approximately 10%, and slope stability analysis confirmed that required safety factor is less than compare with the non-frozen samples.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.143-154
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• 1999

In this study, the load transfer mechanism of tendon-grout interface of rock anchors has been examined through a series of static pull-out tests conducted on the model rock anchors constructed in the natural and artificial rock masses of granite and concrete, respectively. Several rock masses with horizontal discontinuities have been prepared to study the effects of weak planes on the shear stress distribution in tendon-grout interface. As a result, for the rock anchors constructed in the rock mass without discontinuities, stress concentration occurs on the upper part of the tendon-grout interface. On the contrary, as the frequency or the number of discontinuities increases, the shear stress distribution along the depth tends to be uniform. Also, an experimental equation about shear stress distribution between tendon-grout interface can be made by the regression of test results. The shear stresses computed from the experimental results between the rock surface and the depth of 2~3 times the tendon diameter are smaller than those from theory. Below the depth, the reverse can be observed.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.155-165
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• 1999

In completely weathered granite gneiss,8 of 40cm cast-in-situ concrete piles are constructed, and static pile load tests are executed on the piles to study the bearing behavior of rock-socketed piles. Subsurface explorations are carried out on the test site in three phases, in which 14 borehole investigations as well as the seismic investigation are performed. Rock socketd depths of the piles in the weathered rocks are varied as 3m, 6m and 9m to separate the shaft resistance from the end bearing resistance, and for a couple of piles, styrofoam of 10cm thickness is installed under the pile point to eliminate the effect of the end resistance. Strain gages are instrumented on re-bars to pick-up the transferred loads along the pile length. From the results of the pile load tests, the allowable shaft resistance and the allowable end bearing values of weathered rocks are proposed as $8.6t/m^2\;and\; 84t/m^2$, respectively. The empirical equation relating the elastic modulus of rock mass with the uniaxial compressive strength of the rock specimen is also proposed for the weathered rocks.