• Journal of the Korean GEO-environmental Society
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• v.8 no.4
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• pp.67-74
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• 2007

Many studies for slope stability studies have indicated that the infiltration of rainwater into a slope decrease the slope stability. In order to minimize damage caused by slope failure, most design codes suggest that the slope stability be analyzed by saturated condition during rainy season. However it would be excessively conservative condition that every soil slope is saturated in rainy season irrespective of rainfall intensity, soil type and slope geometry. In addition, because most soil slopes are in an unsaturated state, it is necessary to consider the unsaturated characteristics of slope. This paper suggests a prediction method of saturation time for the weathered granite soil slopes due to rainfalls. The finite element analysis of transient water flow through unsaturated slope was used to investigate effects of soil-water characteristics, permeability at saturation, slope geometry, and rainfall intensity. From the result of these analyses, the prediction charts considering soil-water characteristics, permeability at saturation, and slope height were proposed in this study. It is possible to the time required to be saturated slope after rainfall.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.4
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• pp.284-289
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• 2014

Farmers in highlands in South Korea pile up 20 to 30 cm of saprolites, mostly granite- or granite-gneiss-weathered materials, on surface of arable lands every three to five years to compensate eroded soil and sometimes to discontinue soil-borne diseases. Immediate increases of infiltration and percolation rates are expected with coarse textured saprolites while soil drainage becomes poorer in a long-term. In this study, we analyzed mineralogical characteristics and micro-morphology of plow pan to investigate processes making impermeable layers. Soil samples were collected from plow pan, usually located at approximately 20 cm soil depth and at the lower part of piled saprolites, in arable lands in Hoenggye 5-ri, Daekwanryeong-myeon, Gangwon-do (N37.7, E128.7) in which saprolites were added 2, 4, and 8 years ago; saprolites were transported from similar areas. The saturated hydraulic conductivity decreased over time. Based on soil thin section pedography, quartz and feldspar accounted for a majority of minerals. The size of feldspar decreased and macropores became filled with clay or silt particles over time, which implies that macropores were packed with particles weathered from feldspar. The X-ray diffraction (XRD) analysis indicated that intensity of feldspar decreased over time and the reverse was true for kaolinite and illite, indicating that feldspar and mica weathering induced formation of kaolinite and illite. Conclusively, deteriorated drainage by formation of impermeable layers in farms with piled saprolites was caused by accumulation of clay minerals such as kaolinite and illite in macropores; illite and kaolinite can be formed by weathering of mica and feldspar, respectively.

• Korean Journal of Remote Sensing
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• v.17 no.2
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• pp.165-181
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• 2001

Using a field spectrometer having a spectral range of 0.4$\mu\textrm{m}$~2.5$\mu\textrm{m}$ with a spectral resolution of 1nm, the researchers measured the reflectance of granite, andesitic rocks, sedimentary rocks, and pyrophyllite ore in the Ungsang area, Kyungsang Basin, South Korea. Spectral characteristics of the geological media were investigated from the analysis. The in-situ measured sites were selected in well exposed rock outcrops. In case of unfavorable weather conditions, rocks were sampled and remeasured under natural solar condition. The reflectance of field data was measurd at three sistes for granite, six sites for andesitic rock three sites for sedimentary rocks, and two sites for pyrophyllite ore. The vibrational absorption bands for pyrophyllite are detected in the spectral range of 2.0$\mu\textrm{m}$~2.5$\mu\textrm{m}$. The absorption band for granites in study area is not distinctive. The reflectance measured under normal field conditions showed strong absorption at wavelengths of 1.4$\mu\textrm{m}$ and 1.9$\mu\textrm{m}$ due to the effect of moisture in the atmosphere. After the bands of 1.4$\mu\textrm{m}$ and 1.9$\mu\textrm{m}$ were removed, Hull Quotient method was applied to characterize absorption bands. The reflectances of field data were calculated to estimate the band ratio corresponding to the Landsat TM and EOS Terra ASTER. The researchers suggest here that the TM band2, band3, band4, and band7 or ASTER band2, band3, band4, and band9 are the best combination for discriminating outcrops. The researchers tested and demonstrated using a Landsat TM image in the study area. For geologic applications, decorrelation stretch is also an effective tool to enhance the exposed rock mass in images.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.4
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• pp.255-264
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• 2021

Asian dust (Hwangsa) deposited on the surface of the Korean Peninsula is difficult to recognize their existence in mountainous terrain undergoing active erosion and weathering. This study examined Asian dust sediments mixed in soils by analysing clay mineralogy, mineral composition, and microtextures of fine silt (< 20 ㎛) in the alkali feldspar granite area of Seoraksan. The fine silt was composed of detrital particles derived from bedrocks, Asian dust sediments, and their weathering products. Clay minerals of 2:1 structural type, chlorite, amphibole, epidote, and Ca-bearing plagioclase were identified as eolian mineral particles. During the weathering of the bedrock composed of quartz and alkali feldspars, albite was partially weathered to produce small amounts of gibbsite and kaolin minerals. Hydroxy-Al interlayered clay minerals were formed by the exchange and fixation of polynuclear Al cationic species into the interlayers of expandable 2:1 clay minerals dominated by illite-smectite series clay minerals. Contribution of Asian dust to the fine silt of soils was estimated around 70% on the basis of total contents of 2:1 phyllosilicates.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.4
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• pp.329-340
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• 2010

Mechanical behavior of underground cavity construction such as tunnel is very difficult to estimate due to complexity and uncertainty of ground. Prediction of behavior according to excavation of tunnel mainly uses method utilized of model test or numerical analysis. But scale model test is difficult to reappear field condition, numerical analysis is also very hard to seek choice of suitable constituent model and input data. To solve this problem, this paper forecasted the deformation of tunnel that applied to information of crown settlement and convergence, RMR in weathered granite by using the regression analysis. The result of the analysis shows that the crown settlement according to excavation occurs approximately 70~80% of total displacements within about 20 days. As a result of the prediction of crown settlement and convergence, an exponential function becomes more accurate at measurements than an algebraic function. Also this paper got a correlation in comparison of RMR and displacements of 6 sections.

• Geotechnical Engineering
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• v.12 no.6
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• pp.163-184
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• 1996

In this study, physical and geotechnical properties of the light weight mixed soil( weathered granite soil mixed with small pieces of waste EPS) were analyzed by laboratory experiments to examine its suitability for backfill materials of the reinforced-earth walls. Friction characteristics of geogrid-light weight sized soil were also investigated by performing the pullout tests for two types of geogrids having different flexural rigidity. Also a procedure was proposed to evaluate friction strength between geogrid and light weight miffed soil by using a stress-strain relationship of the orthotropic composite material subjected to both longitudinal and vertical loadings. By the procedure proposed in this study, values of the calibration coefficients ul and uf applicable for the evaluation of friction strengths between two types of geogrids and light weight mixed soils were further presented.

• Geotechnical Engineering
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• v.13 no.6
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• pp.95-106
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• 1997

A pressuremeter is an expandable tube which is placed in the soil, and then expanded under controlled condition against the soil. From this test a pressure expansion curve of the soil can be obtained. However soil disturbance during the test has significant influence on the results of tests. A general governing equation for pressuremeter test can be theoretically derived on the basis of the hyperbolic soil model and the cavity expansion theory. The curve fitting technique was used to establish the pressure-strain curve without disturbance of soil during testing. This interpretation makes use of both the loading and unloading portions of the test. An interpretation methodology is described and illustrated with pressuremeter test data carried out in the weathered granitic soil to estimate initial shear modulus. Standard penetration test is a very common site investigation technique in Korea. Therefore the blow counts of standard penetration test are discussed by comparing them with initial shear modulus.

• The Journal of Engineering Geology
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• v.10 no.3
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• pp.225-236
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• 2000

We conducted laboratory simulations of deep vertical drilling into the earth's crust to induce borehole breakouts and investigated their potential use for estimating in situ stress magnitudes in Westerly granite and Berea sandstone. Our experiments consisted of two major stages, a series of triaxial tests and borehole-breakout formation tests under a wide range of far-field stresses. We derived the Mohr-Coulomb, Nadai and Mogi failure criteria from the triaxial test results. Each criterion was compared with the stress condition at breakout boundaries. We concluded that the well known Mohr-Coulomb criterion is not compatible with the stress condition at breakout failure. On the other hand, polyaxial (truly triaxial) failure criteria such as the Nadai criterion for Berea sandstone and the Mogi criterion for Westerly granite were much more suitable for predicting breakout failure zone. Such failure criteria appeared to enable the reliable estimation of the magnitude of one of two horizontal principal stresses if the other one is known.

• Economic and Environmental Geology
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• v.23 no.2
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• pp.135-141
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• 1990

A number of alunite and pyrophyllite deposits occur around the Haenam area where Cretaceous volcanic and volcanogenic sediments are widely distributed. The K-Ar ages of alunite, sericite and whole rocks collected from alunite and pyrophyllite deposits and unaltered rocks representing various stratigraphic horizon of the area were determined and their formation stage was discussed. The ages of volcanic rocks range between $68.6{\pm}1.9$ and $94.1{\pm}2.0$ Ma corresponding to Cenomanian-Maastrichtian of upper Cretaceous. Andesitic rock gives $94.1{\pm}2.0$. Rhyolite and acidic tuffs give $79.47{\pm}1.7$ and $82.8{\pm}1.2$ Ma corresponding to Campanian. The later stage andesite gives $68.6{\pm}1.9$ Ma of Maastrichtian. The results suggest that volcanism of the area can be devided into three different stages. The ages of alunite and sericite range $71.8{\pm}2.8$ to $76.6{\pm}2.9$ Ma of late Campanian to early Maastrichtian which is rather earlier than the age of granite(67 Ma). It indicates that the alteration ages of these clay mineral deposits appeared to be related with its volcanism rather than the hydrothermal stage of granite of this area.

• Economic and Environmental Geology
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• v.27 no.2
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• pp.161-170
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• 1994

Jindong Granites are plotted mainly in the region of granodiorite~diorite of the Streckeisen's diagram, while Yucheon-Eonyang Granites and Onjonri Granites in the region of monzo-granite and monzo-granite~granodiorite, respectively. Jindong Granites show a differenciation trend of calc-alkaline magma, and its magmatic evolution from intermediate to acidic rocks, which might form mineralizing solution, is consistant with the general path of the Cretaceous granitic rocks including Yucheon-Eonyang Granites and Onjongri Granites. The differenciation index (D.I.) is 35~80 for Jindong Granites, which is lower than 85~95 of Yucheon-Eonyang Granites and is partly overlapped by 67~84 of Onjongri Granites. There is clear difference in content of some major and trace elements between Jindong Granites of Cu province and the other granitic rocks of Pb-Zn and Mo provinces. Between these metallogenic provicnes, Cu content is high in Jindong Granites near Haman-Gunbuk mineralized zone, while Pb and Zn are relatively abundant in Yucheon-Eonyang Granites and Mo in Onjongri Granites. Therefore, Jindong Granites of the Cu province are distinguishable by chemical compositions and their related geochemical characteristics from the other Cretaceous granitic rocks of Pb-Zn and Mo provinces. However, the content of Cu and Cl in biotite is applicable to distinguish a productive phase from a barren phase of Jindong Granites, because Cu and Cl show a trend to be concentrated in biotite of Jindong Gratites in the Haman-Gunbuk mineralized zone.