• 한국지반공학회논문집
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• 제38권2호
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• pp.5-13
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• 2022

불포화토의 전단 특성 평가는 사면, 제방, 댐 등의 안정성과 투수 특성 평가에 매우 중요한 요소이다. 본 연구에서는 화강풍화토의 불포화 전단특성을 파악하기 위하여 불포화 삼축실험을 수행하였다. 실험에 사용된 시료는 국내에 분포하는 세립분이 다량함유된 SM계열 화강 풍화토이며, 다짐을 통하여 재성형 하였다. 모관 흡수력 및 시료의 밀도에 따른 불포화 전단 특성을 분석하였으며, 전단 과정에서 일정한 모관 흡수력을 유지 하기 위해 압밀-배수삼축실험(CD-test)을 수행하였다. 본 연구결과 화강풍화토 시료의 겉보기마찰각(ϕ^b)과 AEV(Air Entry Value)는 상대밀도가 증가함에 따라 증가하는 경향을 나타내었다. 그러나 모관흡수력이 증가함에 따라서는 점착력(c) 역시 증가하였지만 내부마찰각(ϕ')은 크게 변함이 없는 것으로 확인 되었다.

• 한국농공학회지
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• 제31권1호
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• pp.58-70
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• 1989

The paper compared the Bishop methed to the Fellenius method in the analysis of slope stability. Laboratory model test was carried out in the case of seepage flow considered. The results obtained from this study were summarized as follows; 1. The slice pieces of 10 were enough to analysis the slope stability. 2. The safety factor. by the Fellenius method was lower than the Bishop method by the 96 to 97% in the case of no seepage flow and by the 95 to 96% in the case of seepage flow considered. 3. Besides the parameter of soil and slope, the safety factor of slope was influenced by the height of slope. This phenomena was distinct in the height of height less than 10 meters. 4. In the case of clay, there was no difference in the safety factor of slope between Fellenius and Bishop rnethod. The safety factors of slope with the seepage flow considered were lower than those with no see-page flow. 5. The influence of cohesion on the safety factor was more significant in the Bishop method than in the Fellenius method. 6. The slope failure of model test of A and B soil samples with high permeability coefficient was taken place slightly in vicinity of toe by the concentration of stress and gradually increased 7. Under condition of same slope height, the shapper the slope, the shorter the radius and the center of critical circle appered downward and finally failure of slope occured inside the slope.

• 한국농공학회지
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• 제11권4호
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• pp.1783-1790
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• 1969

It is one of the most economical method of soil stabilization works to compact soil, which increases soil density artificially. Compaction effort is to lessen void of soils, and consequently its aim is to enlarge friction and cohesion force, and reduce permeability of soil. Factors in compaction effort are moisture content, grain size, grain size distribution, physical properties, compaction method and temperature of soils etc. The results obtained in this study on the effects that grain size, gradation and physical properties influence upon compaction effort for 20 samples under the constant compaction method, are summarized as follows: 1. The bigger the maximum dry density is, the smaller the optimum moisture content is, on the other hand, the smaller the maximum dry densityis, the bigger the optimum moisture content is, ingeneral. 2. The coarser the grain size is, the bigger the maximum dry density is, and the optimum moisture content becomes small, and dry density-moisture content curve has the sharp peak, generally. Also, the finer the grain size is the smaller the maximum dry density is, and the optimum moisture content shows the big value, and dry density-moisture content curve has the dull peak. 3. The maximum dry density shows the biggest value on the sample to be about 15% of particles finer than No. 200 sieve. The more the percent passing of No. 10 sieve increase, the smaller the maximum dry density is. Soils which have uniformity coefficient less than 5 in particles larger than 0.074mm hardly show dry density-moisture content curve. 4. There is a relation which is ramax＝2.3948-0.0376 Wopt between the maximum dry density and the optimum moisture content, namely, the maximum dry density is increased in proportion to decrease of the optimum moisture content. 5. There are relations to be the straight lines which the maximum dry density decrease, on the other hand, the optimum moisture content increase in accordance with enlargement of Atterberg Limit(LL, PL, PL) in compacted soils.

• Geomechanics and Engineering
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• 제15권1호
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• pp.659-668
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• 2018

A series of direct shear tests were implemented on three different types of specimens (i.e., clean Perth sand, sand containing 10, 20 and 30% bentonite, sand containing 1, 3 and 5% slag, and sand containing 10, 20 and 30% bentonite with increasing percentages of added slag (1%, 3% and 5%). This paper focuses on the shear stress characteristics of clean sand and sand mixtures. The samples were tested under different three normal stresses (100, 150 and 200 kPa) and three curing periods of no curing time, 7 and 14 days. It was observed that the shear stresses of clean sand and mixtures were increased with increasing normal stresses. In addition, the use of slag has improved the shear strength of the sand-slag mixtures; the shear stresses rose from 128.642 kPa in the clean sand at normal stress of 200 kPa to 146.89 kPa, 154 kPa and 161.14 kPa when sand was mixed with 1%, 3% and 5% slag respectively and tested at the same normal stress. Internal friction angle increased from $32.74^{\circ}$ in the clean sand to $34.87^{\circ}$, $37.12^{\circ}$ and $39.4^{\circ}$ when sand was mixed with 1%, 3% and 5% slag respectively and tested at 100, 150, and 200 kPa normal stresses. The cohesion of sand-bentonite mixtures increased from 3.34 kPa in 10% bentonite to 22.9 kPa, 70.6 kPa when sand was mixed with 20% and 30% bentonite respectively. All the mixtures of clean sand, different bentonite and slag contents showed different behaviour; some mixtures exhibited shear stress more than clean sand whereas others showed less than clean sand. The internal friction angle increased, and cohesion decreased with increasing curing time.

• 한국지반신소재학회논문집
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• 제22권3호
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• pp.11-25
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• 2023

본 연구에서는 시멘트혼합처리토를 활용한 경사 자립식 흙막이공법에 대한 설계법과 해석법에 대하여 연구하였다. 경사 자립식 흙막이 벽체의 경우 경사에 따른 주동토압계수의 감소와 자중효과로 주동측압이 감소하고 수동토압계수의 증가와 자중모멘트의 증가로 인해 전체적인 안정성이 증가하였다. 흙막이 벽체는 경사에 따라 굴착측으로의 전도파괴에서 활동파괴로의 형태 변화가 발생되었고, 최적의 경사는 10°인 것으로 평가되었다. 수치해석에서의 전체 안정성은 강도감소법과 비교하여 한계평형해석이 보수적인 결과를 도출하므로 설계 시 본 방법으로 검토해야 하는 것으로 나타났다. 매개변수 연구 결과, 지지력파괴와 압축파괴에 대한 안정성은 상재하중이 작은 경우(약 20kPa 이하) 경사 10°이상에서는 크게 증가하지 않았다. 배면 지반의 점착력이 있는 경우 수치해석과 유사한 결과는 점착력을 고려한 경우로 나타났다. 활동, 전도, 전단, 인장에 대한 안정성은 벽체의 두께에 비례하여 증가하지만, 일정 경사각(약 10°) 이상에서는 벽체의 두께와 상관없이 지지력과 압축응력의 안정성에 큰 변화가 없는 것으로 평가되었다.

• 한국농공학회지
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• 제16권4호
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• pp.3611-3616
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• 1974

Alluvial plain of the coast of Kum river tail were found as being mostly consisted of weak foundation. The settlement of the ground, density and change of moisture content which were formed by the load due the construction of earth works were disclossed by the field investigations and laboratory tests. The results are as follow, 1) Banking materials are SM and soft soil stratum is CL. 2) Field moisture content; Wf=19-1.37c c; percentage of clay (less than 0.005mm) 3) optimum water content and maximum density of banking materials; rt=2.15$\mid$0.0165W(12%24%) 4) Density and moisture coutent of banking materials; rt=2.146-0.0095W (8%50%) 5) Density and moisture content of weak foundation; rt=2.06-0. 007W After construction (20%50%) Befor construction (40%60%) 6) Load and settlement of weak foundation; Everage settlement ratio; 12% of actual load p Maximum settlement ratio; 19% of actual load p Minimum settlement ratio: 5% of actual load p 7) Relation of cohesion and unconfined compression test value; c=1/2qu (qu<0.5kg/$\textrm{cm}^2$) c=1/3qu (qu<0.5kg/$\textrm{cm}^2$)

• Ecology and Resilient Infrastructure
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• 제5권3호
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• pp.180-188
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• 2018

하천 제방의 토양 안정화 물질의 하나로, 미생물 유래 베타글루칸과 잔탄검 계열 바이오폴리머를 사용하고자 하는 연구가 현재 진행중이다. 본 연구의 목적은 바이오폴리머 신소재의 생태성 평가의 일환으로, 바이오폴리머가 국내 하천에 자생하는 식물의 씨앗 발아 및 생육에 미치는 영향을 평가하는 것이다. 낙동강과 영산강에 자생하는 총 9종의 식물을 대상으로 시험한 결과, 발아율, 총 건중량, 지상부 건중량, specific leaf area 등 지상부 형질에서는 식물종 별로 다양한 바이오폴리머에 대한 반응을 나타냈다. 애기똥풀의 총 건중량과 지상부 건중량은 감소한 반면 타 식물종들은 건중량을 유지하거나 다소 증가시켰다. 반면 대상 식물종들의 뿌리 생장 (뿌리 길이, 지상부 대비 지하부 건중량)은 바이오폴리머가 처리된 토양에서 증가하는 경향을 보였다. 이러한 결과로 보아, 본 연구에서 시험된 바이오폴리머는 토양 강화 효과와 함께 자생 식물의 뿌리 생장을 촉진시켜, 제방을 강화시키는 역할을 할 것으로 기대된다. 그러나 화학물질들에 대한 식물 반응의 종 특이성을 고려할 때, 보다 광범위한 식물종을 대상으로 하는 연구가 필요할 것이다.

• 한국농공학회지
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• 제26권1호
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• pp.29-37
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• 1984

This study was made to find several significant relations among various physical and mechanical properties including cone penetration resistance. The alluvial clay samples were taken at the Daebul Reclaimed Tideland in Samhomyeon, Yeongamgun, Jeonranamdo. The results of the study are summarized as follows; 1.Most samples belong to medium or high plastic, inorganic, silty clay(clay contents;32-64%, silt contents; 36-68%, sand contents; 0-3%). The specific gravities range from 2.70 to 2.73, the unit weights from 1.45 to 1. 75g/cm$^3$, the natural moisture contents from 45 to 77%, the liquid limits from 32 to 56%. It is certain that the foundation is weak because the natural moisture contents are much higher than the liquid limits. 2.It is known from the shear tests that the unconfined compression strenghs vary from 0.09 to 0. 38kg/cm2, the cohesions from 0.05 to 0. 21kg/cm2, the internal friction angles from 0 to 3˚. 3.The consolidation tests show that the initial void ratios range from 1.25 to 2.28, the compression indeices from 0.43 to 0.84, the preconsolidation loads from 0.21 to 0.74kg/cm$^2$. 4.Cone penetration resistances are usually less than 5kg/cm$^2$ from ground surface to the depth of about 8m, and from S to l0kg/cm$^2$ in the layer below about 8m to hard layer. 5.The cohesion and cone penetration resistance are in proportion to the depth of soil layer. 6.The correlations between various physical and mechanical properties including cone penetration resistance for the alluvial clay samples are as follows; a) Wn=0.944C+ l2.733 (r=0.829) b) LL=0. 728Cy+6. 991 (r=0. 873) c) PI=0.659Cy-8.168 (r=0.860) d) rt=0. 0077(272-Wn) =2.092-0. 0077Wn (r=0. 859) e) 60=0. 035wn-0 447 (r=0. 893) f) C=0.380qw+0.031 (r=0.816) g) qu=0.0707qc+0.029 (r=0.810) h) C=0.018Z+0.055 (r=O.802) I) qc=0. 415Z+1, 438 (r=0. 943)

• Earthquakes and Structures
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• 제15권6호
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• pp.687-699
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• 2018

This paper investigates the pseudo-static analysis of reinforced slopes with geosynthetics under the influence of the uniform surcharge to evaluate the maximum tensile force of reinforcements. The analytical approach has basically been used to develop the new practical procedure to estimate both tensile force and its distribution in the height of the slope. The base of developed relationships has been adapted from the conventional horizontal slice method. The limit equilibrium framework and the assumptions of log-spiral failure surface have directly been used for proposed analytical approach. A new analytical approach considering a single layer of non-cohesion soil and the influence of uniform surcharge has been extracted from the 5n equation and 5n unknown parameters. Results of the proposed method illustrated that the location of the surcharge, amount of internal friction and the seismic coefficient have the remarkable effect on the tensile force of reinforcement and might be 2 times increasing on it. Furthermore, outcomes show that the amount of tensile force has directly until 2 times related to the amount of slope angle and its height range. Likewise, it is observed that the highest value of the tensile force in case of slope degree more than 60-degree is observed on the lower layers. While in case of less degree the highest amount of tensile force has been reported on the middle layers and extremely depended to the seismic coefficient. Hence, it has been shown that the tensile force has increased more than 6 times compared with the static condition. The obtained results of the developed procedure were compared with the outcomes of the previous research. A good agreement has been illustrated between the amount results of developed relationships and outcomes of previous research. Maximum 20 and 25 percent difference have been reported in cases of static and seismic condition respectively.

• 지질공학
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• 제17권3호
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• pp.435-443
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• 2007

본 연구에서는 풍화대에 분포하고 있는 핵석지반에 대한 지질공학적 조사와 실내모형실험을 통하여 핵석지반의 공학적 물성을 산정하였다. 핵석이 노출된 세 곳의 산사면에 대한 조사창 조사와 시추공 코어 관찰로 핵석의 분포도와 기하학적 모양을 분석하였다. 현장 핵석분포 및 크기에 대한 조사 자료와 모형실험용 공시체 시편의 크기를 바탕으로 산정된 축소율을 고려하여 5mm이하-평균 2mm의 분쇄-연마된 핵석시료를 실내핵석 실험용으로 사용하였다. 핵석 체적함유비를 0%, 10%, 20%로 달리하면서 토양 직접전단시험 및 석고모형실험을 실시하였고, 이를 통하여 핵석지반의 특성을 구하고자 하였다. 핵석함유 토양의 직접전단실험에서는 핵석 함유량의 증가로 인하여 전단강도가 증가하는 경향을 보여주었다. 핵석함유비가 20%일 경우는 핵석 입자의 맞물림에 의한 점착력의 증가가 마찰각의 변화보다 더욱 전단강도의 상승을 유발시키는 요소로 작용하였다. 핵석 함유비를 달리한 석고모형실험에서는 핵석이 많아질수록 모형시료의 강도 및 탄성계수가 증가하는 경향을 보여주었다. 석고모형실험에서 얻어진 핵석 함유량에 따른 모형의 물성변화률을 현장에서 측정한 풍화대의 물성과 비교하여, 현장에서 핵석함유에 따른 물성을 예측한 결과, 핵석 함유가 0%에서 10%로 증가하면 15%의 일축압축강도 증가를, 핵석 함유가 20%로 증가되면 30%의 일축압축강도 증가를 유발하는 것으로 예측이 되었다.