• Geotechnical Engineering
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• v.12 no.6
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• pp.115-126
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• 1996

The purpose of 1,his study is to analyze the compression and strength charactefistics of the decomposed -weathered soil originating from biotite gneiss or fine grained gneiss sampled from Poidong, Seoul : to figure out the behavioural characteristics of the decomposed -weathered soil in accordance with mineral composition and origin by comparing experimental results of residual soils. originating from granites and sampled from Bulam, Andong and Kimchun area. A series of CIU, CID CKoV, CKoD tests were car lied out. Although weathered soils have different origin and mineral composition, the slope of the NCL A was similar. It was also shown that plastic strain ratio was about 85% mainly due to the particle crushing effect during compression. The Poidong soil showed strain softening phenomenon unlike the Kimchun and Andong soils. this implies that the behavioural characteristics are affected by the origin and the mineral composition of the soil particles. Moreover, it was found that the angle of the shear resistance$(\phi')$ was dependent on the mineral composition. On the oher hand, measured Af values of decomposed weathered soils were more than one regardless of the origin and the mineral composition.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.125-139
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• 1999

It is difficult to evaluate the shear strength of weathered residual soils because of the difficulties of undisturbed sampling. In this study, a sampling device, direct shear box with shoe, was developed in order to get undisturbed samples easily for direct shear tests, and undisturbed samples could be successfully obtained. Through direct shear tests on undisturbed samples, the shear strength was evaluated with the variation of saturated conditions. In order to consider the effect of disturbance on the shear strength, a static compaction device was developed, and then it was found that undisturbed samples show greater shear strengths than the disturbed ones under natural water contents and similar strengths to the ones under soaked conditions. Further, the shear strength evaluated from direct shear tests was compared with the result of triaxial tests on undisturbed samples, and soaked strengths of the former were similar to the latter. As the result of stability analyses on an actual failed slope, it was found that the shear strength can be evaluated reasonably using direct shear box with shoe.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.03a
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• pp.32-66
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• 1998

• 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.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.73-80
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• 1998

• Proceedings of the Korean Geotechical Society Conference
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• 1996.10a
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• pp.39-50
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• 1996

• Applied Biological Chemistry
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• v.1
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• pp.12-20
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• 1960

고위생산답(高位生産畓) 22개(個)와 매년(每年) 호마엽고병(胡麻葉枯病)을 발생(發生)시키는 저위생산답(低位生産畓) 18개토양(個土壤)을 분석(分析)하고 활성철(活性鐵)과 열염산(熱鹽酸)에 녹는 철(鐵)의 분포상태(分布狀態)를 조사(調査)하였으며 그 결과(結果)는 아래와 같다. 1. 작토중(作土中)의 활성철(活性鐵)의 함량(含量)과 청취(聽取)한 정조수량간(正粗收量間)에는 밀접(密接)한 정상관(正相關) (${\gamma}=0.68$, 고등(高等)의 유의성(有意性)이 있음)이 있다. 2. 고위생산답(高位生産畓) 토양(土壤)의 활성철(活性鐵) 및 열염산가용철(熱鹽酸可溶鐵)은 저위생산답(低位生産畓) 토양(土壤)에서의 그것보다 현저(顯著)히 많았으며 각(各) 토양별(土壤別) I 층(層)의 그 평균함량(平均含量)과 열염산가용철(熱鹽酸可溶鐵)에 대(對)한 활성철(活性鐵)의 비율(比率)은 아래와 같다. 고위생산답(高位生産畓) 조사점수(調査點數) 활성철(活性鐵)% 활성철(活性鐵)/염산가용철(鹽酸可溶鐵) 잔적토(殘積土) 6 1.313 0.374 하성토(河成土) 9 1.334 0.335 해성토(海成土) 5 1.120 0.382 평균(平均) 20 1.224 0.359 저위생산답(低位生産畓) 조사점수(調査點數) 활성철(活性鐵)% 활성철(活性鐵)/염산가용철(鹽酸可溶鐵) 잔적토(殘積土) 5 1.15 0.370 하성토(河成土) 8 0.472 0.191 해성토(海成土) 5 1.068 0.362 평균(平均) 18 0.808 0.288 그러나 표(表)에서와 같이 잔적토(殘積土) 저위생산답(低位生産畓) 각층(各層)의 철(鐵)은 고위생산답(高位生産畓)에서 보다 낮지 않았다. 3. 해수(海水)의 영향(影響)을 받지 않은 고위생산답(高位生産畓)에서는 표층토(表層土)의 세탈(洗脫)이 적었으나 동(同) 저위생산답(低位生産畓) 및 해성토(海成土)에서는 그 세탈(洗脫)이 크고 동세탈물(同洗脫物)은 심층(心層)에 집적(集積)되여 있다. 4. 해성토(海成土)에서는 고위생산답(高位生産畓)이나 저위생산답(低位生産畓)을 막론(莫論)하고 집적층직하(集積層直下)에 활성철량(活性鐵量)이 심(甚)히 적은 층(層)이 있다. 그리고 집적층(集積層)은 고위생산답(高位生産畓)에서는 II-III층(層)(지표면(地表面)으로부터 60cm이내(以內))에 저위생산답(低位生産畓)에서는 I-II층(層)(지표면(地表面)으로부터 대개(大槪) 30cm이내(以內))에 위치(位置)한다. 5. 같은 고위생산답(高位生産畓) 및 저위생산답(低位生産畓)에서는 토성간(土性間)의 활성철함량(活性鐵含量)에 큰 차이(差異)가 없다. 6. 내산씨(內山氏)의 4개(個)기본(基本)토양형별(土壤型別)로는 동일(同一)토양형((土壤型)이라도 고위(高位) 저위생산답별(低位生産畓別)로 활성철(活性鐵)의 함량(含量)에는 차이(差異)가 크다.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.03a
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• pp.93-100
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• 1998

• 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 Korean Geotechnical Society
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• v.19 no.2
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• pp.27-38
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• 2003

The characteristics and prediction model of the shear strength of unsaturated residual granite soils were studied in this paper. In order to investigate the influence of the net normal stress on the shear strength, unsaturated triaxial tests and SWCC tests were carried out by varying the net normal stress. Experimental data for unsaturated shear strength tests were compared with predicted shear strength envelopes obtained from existing prediction models. It was shown that the soil-water characteristic curve and the shear strength of the unsaturated soil varied with the change of the net normal stress. Therefore, to achieve a truly descriptive shear strength envelope for unsaturated soils, the effect of the normal stress on the contribution of matric suction to the shear strength has to be taken into consideration. In this paper, a modified prediction model f3r the unsaturated shear strength was proposed.