• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.360-372
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• 2005

The weathering degree and shear wave velocity, $V_S$, were evaluated for decomposed granite layers in Hongsung, where earthquake damages have occurred. The subsurface geological layers and their $V_S$ profiles were determined, respectively, from boring investigations and seismic tests such as crosshole, downhole and SASW tests. The subsurface layers were composed of 10 to 40 m thickness of weathered residual soil and weathered rock in most sites. In the laboratory, the weathering indexes with depth were estimated based on the results of X-ray fluorescence analysis using samples obtained from field, together with the dynamic soil properties determined from resonant column tests using reconstituted specimens. According to the results, it was examined that most weathering degrees represented such as VR, Li, CIA, MWPI and WIP were decreased with increasing depth with exception of RR and CWI. For weathered residual soils in Hongsung, the $V_S's$ determined from borehole seismic tests were slightly increased with increasing depth, and were similar to those from resonant column tests. Furthermore, the $V_S$ values were independent on the weathering degrees, which were decreased with depth.

• Geotechnical Engineering
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• v.13 no.6
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• pp.13-24
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• 1997

In Korea, granite is abundant and occupies around two-thirds of the country's ground. Bven though weathered granite residual soils are widely distributed, undisturbed sampling of this soil is extremely difficult because of the particultate structure. This difficulty has kept away the researchers from investigating !he deformational characteristics of weathered granite residual soil. Thus, a special undisturbed sampling device was developed and undisturbed samples were prepared for triaxial compression (TX), resonant column(RC), and torsional shear (75) tests. Local deformation transducer (LDT) was fabricated for internal strain measurements during TX tests. Both undisturbed samples and statically compacted samples of same density were tested by using TX with LDT, RC, and 75 test equipments. The behaviour of statically compacted specimens was almost the same as that of undisturbed samples in the strain ranges below 1 percent. The stiffness and strength decreased with increasing degree of weathering. In case of undisturbed specimens, strains at failure are widely varied from 2 percent to 11 percent, and planes of failure are irrelevant to the angle of internal friction due to the inhomogeneous nature.

• Geotechnical Engineering
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• v.12 no.4
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• pp.115-130
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• 1996

The definition of laterite or lateritic soils is discussed on a climatic condition of tropical and semitropical regions, and the weathering index is indicated by the chemical composition. The chemical composition of$(Fe_2O_3+Al_2O_3)$ of the weathered granite residual soils in tropical and the temperate regions which shelus laterization usually ranges from 0.2 to 0.5. This study shows that the chemical ratio of the Chonju Ajung site is about 0.2U, and that of the regions along the shore of the western sea of Hongsong and Taechon is about 0.33. The chemical ratio of the non-laterite is less than 0.2, and the Kyougju Pulguksa site confirmed about 0.17, The X-Ray diffraction test shows that the clay mineral of the laterite soils is made of kaolinite, this X -Ray result indicates the same characteristics compared with the wrathered granite residual soils of other sites.

• Geotechnical Engineering
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• v.13 no.5
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• pp.155-168
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• 1997

The phenomena of detachment and movement of One particles are one of the important mechanisms both in geotechnical and geoenvironmental engineering. In geoenvironmental engineering, in particular, movement of fine particles may facilitate the transport of contaminants since the particle surfaces absorb contaminants before movement. Weathered granitic residual soils, which are the most abundant in Korea. contain large quantities of fine particles up to 50%. The characteristics of fine particle movement of weathered granitic residual soils are investigated in this paper. Samples are obtained from Poiiong, Shinnaedong in Seoul and Andong in Kyungpook : each of the samples represents typical residual soil types in Korea. Laboratory experiments for the three adopted soil types are performed. It is found that effluent concentration of the samples is influenced by porosity, fine particle percentage and particle size distribution. The critical velocity decreases as the fine particle percentage increases and the rate of change of erosion rate increases as the porosity increases. And well-graded samples showed less effluent concentrations compared to poorly-graded samples. The governing equation on the physical mechanism of fine particle movement and its nomerical solution scheme are suggested on the basis of the test results.

• Journal of the Mineralogical Society of Korea
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• v.14 no.1
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• pp.58-72
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• 2001

The Cretaceous granite, andesite and sedimentary rocks are widely distributed in the northern Pusan area. The present study investigates mineralogical and geochemical charateristics of residual and cultivated soils derived from these rocks. The soils of granite area contain a large amount of quartz relative to clay minerals, whereas the soils of the andesite area contain more clay minerals than quartz. Clay minerals consist mainly of kaolin minerals illite hydroxy interlayered vermiculite interstratified mica/vermiculite and chlorite. Kaolin minerals are abundant in paddy soils while illite is abundant in less weathered soils. Si and K are major elements in the soils of granite area while Fe and Al in the soils of andesite area. In all the soils Ca, Mg and Na were generally depleted in comparison to those in parent rocks. Analysis data of trace element show that the enrichment pattern in soils depends on parent rock type with high oncentration of some elements over 100 ppm: Ba and Rb in granite area Zn, Bn, and V in andesite area, and Ba and V in sedimentary rock. In granite area, Rb and Th were greatly enriched in soil than in parent rocks. However, Cr, Ni and Sr commonly decrease, whereas Pb increases in all the soils. Exchangeable cation capacity(CEC) is relatively high in the soils of andesite are including abundant clay minerals. Collective evidences prove that the mineralogical and chemical compositions of soils are strongly dependent on the parent rock type. The mineralogy and chemistry of long cultivated soils are not significantly different from those of residual soils.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.481-488
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• 2000

The mechanism of soil-geotextile system has been studied among researchers since the application of geotextile as a replacement of graded granular filters is rapidly growing. The interaction of soils with geotextile is rather complicated so that its design criteria are mostly based on empiricism. Hence, it is essential to study the characteristics of fine particles transport into geotextile induced by the groundwater flow In this study, the permeability reduction in the soil-filter system due to clogging phenomenon is evaluated. An extensive research program is performed using two typical weathered residual soils which are sampled at Shinnae-dong and Poi-dong area in Seoul. Two separate simulation tests with weathered residual soil are peformed: the one is the filtration test(cross-plane flow test): and the other is the drainage test(in-plane flow test). Needle punched non-woven geotextiles are selected since it is often used as a drainage material in the field. The compatibility of the soil-filter system is investigated with emphasis on the clogging phenomenon. The hydraulic behaviour of the soil-filter system is evaluated by changing several testing conditions.

• Journal of the Korean Geotechnical Society
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• v.22 no.6
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• pp.41-49
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• 2006

This paper deals with development and dissipation of excess pore pressure induced by the cyclic load. Cyclic triaxial tests on reconstituted samples of weathered residual soils, which were widely used as construction materials in Korea, were performed. Test results showed that excess pore pressures developed under undrained condition increased with the increase of cyclic loads and confining pressures. And a new concept based on modified excess pore pressure ratio (MEPPR) was proposed for simply estimating excess pore pressures in terms of the number of cyclic load, irrespective of cyclic loads and confining pressures. Also, it was proposed that excess pore pressure ratio (EPPR) could be effectively utilized to estimate volumetric strains during dissipation which decreased as confining pressures increased. Consequently, concept and method to effectively estimate settlements under non-liquefied condition, induced by dynamic loads such as earthquake loads were evaluated based on laboratory test results for reconstituted weathered residual soils.

• Geotechnical Engineering
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• v.9 no.2
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• pp.5-14
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• 1993

Weathered granite soil is the most representative as a surface soil in Korea. In this paper, the dynamic properties and settlement characteristics of Korea granite soil are studied through the dynamic triaxial compression tests. The dynamic characteristics are very important on the analysis of the foundations under dynamic loading such as machine vibration and earthquake. Soil samples having different grain sixtes were prepared at the relative densities between 80oA and 90oA and tested to measure shear moduli and damping ratios at each level of shear strain. The measured shear moduli of weathered granite soils showed large variations according to the grain sizes, confining pressures, relative densities and shear strains. Sandy weathered granite had a little larger dynamic properties than the average values of the sand studied by Seed and Idriss. Pot the well compacted granite soils, little residual settlements occured due to dynamic loading.

• Journal of the Korean Geotechnical Society
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• v.23 no.12
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• pp.13-23
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• 2007

Weathered soils appear from the rock and its weathering result. In accordance with the degree of weathering the roch may become soft rock, weathered rock and residual soil. In general, classification method for determining the degree of weathering are performed by chemical method and N-value. But these method have some problems. So, this research is to suggest an appropriate physical method to determine the degree of weathering of weathered soils. A new classification method for determining the degree of weathering is suggested, based upon the results from fall cone test. According to the proposed physical method using fall cone apparatus, the measured values of the samples from the same area show distinctive difference of weathering. For the checking, we selected two areas. As a result, the relationship between CWI and water content according to penetration is expressed as an equation in Ilsan and Incheon area. And it proved to be a good method to determine the degree of weathering.

• Economic and Environmental Geology
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• v.47 no.2
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• pp.87-96
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• 2014

The objectives of this study were to characterize the physicochemical properties and mineralogy of Hwangto (yellow residual soils) from the southwestern part of Korea and to understand the soil-forming processes of the residual soils from their parent rocks. Both the yellowish residual soils as well as the unweathered and weathered parent rocks were obtained from Jangdong-ri, Donggang-myun, Naju, Jeollanam-do, Korea. The soil samples were examined to analyze the said soil's physicochemical properties such as color, pH, and particle size distribution. A scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis were performed in order to understand the mineralogy, chemical composition, and morphology of the soils. Two thin sections of a parent rock were analyzed to study its mineral composition. A particle size analysis of the soils indicates that the residual soil consists of mainly silt and clay (approximately 95%) and that soil textures are silty clay or silt clay loam. The soil colors of the residual soil are dark brown (7.5YR 3/4) through yellowish red (5YR 4/6). The pH of the residual soil ranges from 4.3 to 5.1. The major minerals of the parent rocks were quartz, biotite, chlorite, and plagioclase. The mineralogy of the sand fraction of the residual soil was quartz, biotite, muscovite and sanidine. The mineralogy of the silt fraction of the residual soil was quartz, biotite, muscovite, Na-feldspar, K-feldspar, and sanidine. The clay mineralogy of the soil was goethite, kaolinite, ilite, hydroxy-interlayed vermiculite(HIV), vermiculite, mica, K-feldspar and quartz. The mineral composition of the residual soil and the parent rock indicates that feldspar and mica in the parent rock weathered into illite, vermiculite and hydroxy-interlayed vermiculite(HIV), and finally changed into kaolinite and halloysite in the yellowish residual soils.