• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.201-208
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• 2000

In this study, the behavior of saturated sandy soils under dynamic loads - pore water pressure and effective stress - was investigated using Disturbed State Concept(DSC) model. The model parameters are evaluated from laboratory test data. During the process of loading and reverse loading, DSC model is utilized to trace strain-hardening and cyclic softening behavior. The procedure of back prediction proposed in this study are verified by comparing with laboratory test results. From the back prediction of pore water pressure and effective mean pressure under cyclic loading, excess pore water pressure increases up to initial effective confining pressure and effective mean pressure decrease close to zero in good greement with laboratory test results. Those results represent the liquefaction of saturated sandy soils under dynamic loads. The number of cycles at initial liquefaction using the model prediction is in good agreement with laboratory test results. Therefore, the results of this study state that the liquefaction of saturated sandy soils can be explained by the effective tress analysis.

• 한국토양비료학회지
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• 제15권2호
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• pp.128-140
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• 1982

저위(低位) 생산답중(生産畓中)에서 분포면적(分布面積)이 가장 넓고 개량(改良)의 효과(効果)가 큰 사질답(砂質畓)의 분포상태(分布状態) 및 실용적(実用的) 분류(分類)와 더불어 현재(現在) 널리 쓰이고 있는 답류형별(畓類型別) 분류체계(分類体系)의 개선(改善)을 위한 사질답(砂質畓) 유형분류(類型分類) 시안(試案)을 시도(試圖)하여 본 결과(結果)는 다음과 같다. 1. 현재(現在) 이용(利用)되고 있는 기준(基準)에 의(依)한 사질답(砂質畓)의 잠재생산력(潜在生産力)은 보통답(普通畓)의 86%이었고 생산력(生産力)의 변이정도(変異程度)가 커서 유형재분류(類型再分類)의 필요성(必要性)이 있었다. 2. 현재(現在) 이용(利用)되고 있는 답유형(畓類型) 구분기준중(区分基準中) "사질답(砂質畓)"은 토성(土性)이 사질(砂質)이더라도 습답(湿畓)인 경우(境遇)와 염농도(塩濃度)가 높은 경우(境遇)에는 제외(除外)되고 있으므로 "객토대상지(客土対象地)" 추천(推薦)이 복잡(複雜)하고 제염(除塩)되거나 배수조건(排水條件) 변화시(変化時)에 유형(類型)을 변경분류(変更分類)해야 하였다. 3. 본(本) 연구(硏究)에서 제안(提案)한 사질답분류(砂質畓分類) 시안(試案)에서는 토성(土性)이 사질(砂質)인 모든 답토양(畓土壌)을 포함(包含)시켰으며 수량(收量)에 영향(影響)이 큰 특성(特性)을 기준(基準)하여 개(個)의 아형(亜型)(산화용탈형(酸化溶脫型) 사질답(砂質畓); 건답형(乾畓型), 산화환원중간형(酸化還元中間型) 사질답(砂質畓); 반습답형(半湿畓型), 환원집적형(還元集積型) 사질답(砂質畓); 습답형(湿畓型), 환원염해형(還元塩害型), 사질답(砂質畓), 염해형(塩害型))으로 재분(再分)하였고 각아형(各亜型)은 토성계별(土性系別)로 토양통(土壌統)과 연결(連結)할 수 있었다. 그러므로 시안(試案)의 분류단계(分類段階)는 형(型)(사질답(砂質畓))-아형(亜型)(4개(個))-토성계(土性系)(5등급(等級))-토양통(土壤壌)(48개통(個統))으로 되었다. 4. 시안(試案)과 같이 사질습답(砂質湿畓)과 사질염해답(砂質塩害畓)을 사질답(砂質畓)의 일부(一部)에 포함(包含)시켜 생산력(生産力)의 변이정도(変異程度)를 검정(検定)해 본 결과(結果)는 현행(現行) 체계(体系)에 의(依)한 것보다 개선(改善)되엇다. 5. 전국(全国)의 사질답(砂質畓) 면적(面積)은 409,902ha로서 총(総) 답면적(畓面積)의 32.3%에 해당(該当)되며 시안(試案)대로 분류(分類)하면 38.9%(492,982ha)에 달(達)하였고 절대면적(絶対面積)이 많은 지역(地域)은 경기(京畿)(88,923ha), 전북(全北)(69,717ha), 경북(慶北)(55,390ha) 순(順)이었고 답면적(畓面積) 전체(全体)에 대(対)한 상대적(相対的) 비율(比率)이 높은 지역(地域)은 강원(江原)(58.9%), 경기(京畿)(50.5%), 충북(忠北)(48.5%), 전북(全北)(41.0%)의 순(順)이며 시안(試案)에 의(依)하면 사질답(砂質畓) 면적(面積)은 더욱 높아져서 강원도(江原道)의 경우(境遇)에는 71.4%가 사질질답(砂質質畓)에 해당(該当)되었다. 6. 사질답(砂質畓)은 답토양(畓土壌) 적성등급(適性等級)의 3급지(級地)(69.1%)와 4급지(級地)(29.2%)에 대부분(大部分)이 해당(該当)되었으며 3급지중(級地中)에서는 "3사질(砂質)"(53.3%), 4급지중(級地中)에서는 "4경사(傾斜)"(16.0%)에 해당(該当)하는 토양(土壌)이 가장 많았다. 토성계(土性系)(Texture family)별(別)로는 사양질계(砂壌質系)(Coarse loamy family)가 59.2%로 대부분(大部分)이었고 징사(徵砂) 사양질계(砂壌質系)(Coarse silty)인 것도 전체(全体)의 16.1%에 달(達)하였다. 7. 시안(試案)에 의(依)한 사질답(砂質畓) 아형별(亜型別) 면적(面積)은 반습답형(半湿畓型) 사질답(砂質畓)(酸化還元中間型)이 49.6%(245,012ha)로 가장 많았고 그 다음으로 건답형(乾畓型) 사질답(砂質畓)(산화용탈형(酸化溶脫型))이 33.5%(64,890ha)이었고 습답형(湿畓型)(14.0%)과 염해형(塩害型)(2.9%)도 그 분포면적(分布面積)은 83,081ha에 달(達)하였다.

• 한국도로학회논문집
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• 제20권1호
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• pp.19-25
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• 2018

PURPOSES : The purpose of this study is to identify the road-subsidence mechanism in unsaturated sandy soils. METHODS : A series of soil chamber tests were conducted under various conditions. RESULTS : The cavity-expansion characteristics in unsaturated sandy soils due to seepage were affected by the outlet size, seepage intensity, relative density, and fine content. CONCLUSIONS : In unsaturated sandy soils, the cavity-expansion speed was affected by the outlet size, relative density, seepage intensity, and clay content; however, the cavity-expansion shape was very similar. As the outlet size and seepage intensity increased, the cavity-expansion speed increased. As the relative density increased, the cavity-expansion speed increased because of a sudden decrease in shear strength, resulting from the increased saturation (reduction of matric suction). The cavity expanded faster with the increasing clay content, up to a certain threshold. It expanded at a slower rate once it passed the threshold. Finally, it reached a stable state where the cavity did not expand due to seepage.

• 한국수자원학회논문집
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• 제32권3호
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• pp.215-223
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• 1999

최근, 국내외에서 TDR(Time Domain Reflectometry)기법을 이용한 토양 함수량 측정이 유용한 기술로써 받아들여져 오고 있다. Topp 등, (1980)에 의하여 최초로 제안된 경험식이 TDR에 의해 측정된 유전상수로부터 토양 함수량을 결정하는 데에 폭넓게 적용되어져 왔다. 그러나, 이 방법의 적용범위는 중간 입자 조성의 토양(Medium-testured soils)에 한해서 제한되어져 왔다. 본 연구에서는 Topp 모델이 사력토(Sandy-gravelly soils)에서도 적용가능한 지를 알아보고자 한다. 검정실험은 토양시료내에 설치된 2선 TDR 탐침을 따라 전송되는 광전자파의 전송시간 측정과 중력법에 따른 토양 함수량 결정의 두 부분으로 구성되었다. 실험에 사용된 토양시료는 2개의 다른 TDR 탐침길이에 대하여 중복시료로서 각 시료당 자갈의 질량 퍼센티지가 다른 7개의 입도 분포로 구성되었다. 계산 결과 Topp이 제안한 식은 주어진 유전상수에 대하여 3내지 8%정도 함수량을 과대 추정하고 있음을 알 수 있었으며, 본 연구에서 사력토에 대한 새로운 경험식을 제안하였다.

• Geomechanics and Engineering
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• 제10권4호
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• pp.527-546
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• 2016

This paper discusses improvements of compressibility, permeability, static and liquefaction strengths of in-situ soils by grouting. Both field testing and laboratory evaluation of the on-site samples were conducted. The improvement of soils was influenced by two main factors, i.e., the grout materials and the injection mechanisms introduced by the field grouting. On-site grout mapping revealed the major mechanism was fracturing accompanied with some permeation at deeper zones of sandy soils, where long-gel time suspension grout and solution grout were applied. The study found the compressibility and swelling potential of CL soils at a 0.5 m distance to grout hole could be reduced by 25% and 50%, respectively, due to the grouting. The effect on hydraulic conductivity of the CL soils appeared insignificant. The grouting slightly improved the cohesion of the CL soils by 10~15 kPa, and the friction angle appeared unaffected. The grouting had also improved the cohesion of the on-site SM soils by 10~90 kPa, while influences on the friction angle of soils were uncertain. Liquefaction resistances could be enhanced for the sandy soils within a 2~3 m extent to the grout hole. Average improvements of 40% and 20% on the liquefaction resistance were achievable for the sandy soils for earthquake magnitudes of 6 and ${\geq}7.5$, respectively, by the grouting.

• Geomechanics and Engineering
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• 제20권5호
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• pp.385-397
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• 2020

This paper presents an application of artificial neural networks (ANNs) in settlement prediction of a foundation on sandy soil. In order to train the ANN model, a wide experimental database about settlement of foundations acquired from available literatures was collected. The data used in the ANNs model were arranged using the following five-input parameters that covered both geometrical foundation and sandy soil properties: breadth of foundation B, length to width L/B, embedment ratio D_f/B, foundation net applied pressure q_net, and average SPT blow count N. The backpropagation algorithm was implemented to develop an explicit predicting formulation. The settlement results are compared with the results of previous studies. The accuracy of the proposed formula proves that the ANNs method has a huge potential for predicting the settlement of foundations on sandy soils.

• 한국균학회지
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• 제10권3호
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• pp.119-124
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• 1982

공시(供試)한 6개지역(個地域)의 토성(土性)은 Colwood와 Capac이 양질토(良質土)이고 Gilford와 Ceresco는 사질식양토(砂質埴壤土)이며 Sission은 식양토(埴壤土)이고 Spinke는 사질토(砂質土)이었다. 토양산도(土壤酸度)는 Gilfold사질식양토(砂質埴壤土)가 6.6이고 기타는 $5.4{\sim}5.9$의 범위로 나타났으며 유기물함량(有機物含量)은 Gilford토양(土壤)이 제일 많이 함유하고 있었다. 일반세균수(一般細菌數)는 Gilford토양에서는 다른 토양(土壤)에서 보다 통제적으로 많았고 사상균수(絲狀菌數)에서도 Gilford와 Colwood토양(土壤)이 다른 토양보다 통계적으로 더 많았다. 방선균(放線菌)의 밀도(密度)를 보면 Gilford와 Ceresco의 토양(土壤)에서 많았고 혐기성(嫌氣性) 세균(細菌)의 수(數)는 Ceresco, Capac및 Colwood에서 많았으며 번대로 사질식양토(砂質埴壤土)인 Gilford에서는 적었다. $^{14}C-glucose$를 첩가한 토양(土壤)에서의 미생물(微生物)의 호흡량(呼吸量)은 Ceresco, Spinks, Colwood, Sission, Capac 및 Gilford의 순(順)으로 적었다. 공시균주(供試菌株) Helminthosporium victoriae(# 418)와 Mortierella n. sp.에 대한 자연토양(自然土壤), 살균토양(殺菌土壤)및 glucose와 peptone을 농도별(濃度別)(mg/g 토양(土壤))로 첨가한 토양(土壤)에서의 발아율(發芽率)을 보면 자연토양(自然土壤)에서는 $0{\sim}5%$이고 살균토양(殺菌土壤)에서는 $90{\sim}98%$이었다. 토양(土壤)에 첨가(添加)된 영양물(營養物)의 농도(濃度)에 따라 공시균(供試菌)의 발아(發芽)정도는 달랐다. 일반적으로 Capac과 Gilford에서는 Spinks토양(土壤) 보다 발아(發芽)에 필요한 영양물(營養物)을 더 많이 요구(要求)하였으며 특히 Mortierella는 H. victoriae보다 발아(發芽)에 있어서 더 많은 량(量)의 영양물(營養物)을 요구(要求)하였다.

• 산업기술연구
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• 제34권
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• pp.45-52
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• 2014

In this paper the settlement characteristic of shallow foundation on sandy soil overlained by rigid ground was investigated by analyzing results of model tests. For model experiments, model tests were performed with sandy soils sampled from the field, changing the relative density of sandy soil and the ratio of thickness of sandy layer(H) to the width of model strip footing(B). As result of tests, settlement of sandy soils increases as the value of H/B increases, whereas it increases with relative density of soil. Bearing capacity decreases as the thickness of the sand layer relative to the footing width increases. In order to analyze the settlement characteristics of sandy ground, the results of model tests were compared with the predicted values using the empirical formulas proposed by Terzaghi, De Beer and Schmertmann. The method by De Beer was found to be in good agreements with test results.

• 아시안잔디학회지
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• 제9권1호
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• pp.81-89
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• 1995

The variations of the soil texture, $SiO_2$ /$Al_2$$O_3$ ratio, buffer action, exchangeable base, ex-changeable hydrogen, and mineral nutrients were investigated to estimate the grade of the soil fertility of the soil derived from the different parent rocks such as the granite in Kwangnung and the basalt in Chejudo. The results investigated were showed as follows : Basalt soils in Chejudo belong to sandy clay, light clay and sandy clay loam, while gramite soils in Kwangnung sandy loam. The $SiO_2$ /$AI_2$$O_3$ ratio of the grassland in Chejudo was 1.11 and that of the oak forest soils was 1.24, while granite soils in Kwangnung 1.54 and 1.46, respectively. The buffer actions of ba-salt soils against the N /10 HCI and $Ca(OH)_2$ were stronger than those of granite soils. The $SiO_2$/$Al_2$$O_3$ + $Fe_2$$O_3$ ratios of grassland and oak forest soils of basalt in Chejudo showed 1.10 and 1.24 respectively, while those of the grassland and oak forest of Kwangnung 1.44 and 1.33. The base exchange capacity of basalt soils which has higher value of exchangeable hydrogen was stronger than that of granite soils. But the base saturation of granite soils showed higher value than that of basalt soils. Water contents of basalt soils in Chejudo was lower than that of granite soils fo Kwangnung Basalt soils in Chejudo contain still more humus and total nitrogen than gran-ite soils in kwangnung, The amount of available nitrogen, available phosphorus and exchangeable calcium of granite soils were more than that of basalt soils, Therefore, estimating the soil fertility, granite soils in Kwangnung is higher than that of basalt soils in Chejudo.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.3-14
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• 2000

Anisotropic consolidation, shear, a transportational component during or after deposition each may produce anisotropic fabrics, which result in the anisotropic properties of soils. Nevertheless, the isotropically consolidated compression triaxial tests are commonly used in practice to determine the strength of the anisotropically consolidated soils because of their practicality and simplicity. In this paper the effects of anisotropic consolidation on the strength properties of soils are discussed. For the sandy soils consolidated under a constant vertical consolidation pressure, the deformation modulus decreases with decreasing consolidation pressure ratio($\sigma$$\sub$3c/'/$\sigma$ sub 1c/'), but the liquefaction resistance increases. For the saturated cohesive soils, both the undrained shear strength and undrained creep strength decrese with decreasing the consolidation pressure ratio. When the in-situ strength properties of the anisotropically and normally consolidated soils are determined by the isotropically consolidated tests, the undrained shear strength and creep strength of saturated cohesive soils as well as the deformation modulus of sandy soils are measured to be higher than the rear in-situ values. This, therefore, could lead to a dangerous judgement in stability analysis