• Geomechanics and Engineering
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• 제15권2호
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• pp.783-791
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• 2018

In consideration of the mesoscopic structure of soil-rock mixtures in which the rock aggregates are wrapped by soil at normal temperatures, a two-layer embedded model of single-inclusion composite material was built to calculate the shear modulus of soil-rock mixtures. At a freezing temperature, an interface ice interlayer was placed between the soil and rock interface in the mesoscopic structure of the soil-rock mixtures. Considering that, a three-layer embedded model of double-inclusion composite materials and a multi-step multiphase micromechanics model were then built to calculate the shear modulus of the frozen soil-rock mixtures. Given the effect of pore structure of soil-rock mixtures at normal temperatures, its shear modulus was also calculated by using of the three-layer embedded model. Experimental comparison showed that compared with the two-layer embedded model, the effect predicted by the three-layer embedded model of the soil-rock mixtures was better. The shear modulus of the soil-rock mixtures gradually increased with the increase in rock regardless of temperature, and the increment rate of the shear modulus increased rapidly particularly when the rock content ranged from 50% to 70%. The shear modulus of the frozen soil-rock mixtures was nearly 3.7 times higher than that of the soil-rock mixtures at a normal temperature.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 사면안정학술발표회
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• pp.145-154
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• 2003

When a nail pulled out in dense, granular soil, the soil in the vicinity of the nail tends to dilate, but its dilatancy results in a normal stress concentration at the soil/nail interface, thereby increasing the pull-out resistance of the inclusion. It is thought to be occurring within the resistance zone where the soil mass is at stationary state and the reinforcement are held in position by the soil, due to the friction or bond. In this paper, A series of direct shear and interface tests were conducted by using so called‘Constant Normal Stiffness Test Apparatus’which was modified and improved from the conventional direct shear box test rig. Unlikely the normal shear box test, this enables to simulate the different constraint effects of surrounding soil during shear under the conditions of constant stress and volume, constant normal stiffness. The aim of the research programme is to get better understanding of pull-out bond mechanism, thus to explore the possibility of evaluating the pull-out bond capacity of soil/reinforcement at the preliminary design stage from the laboratory test.

• 한국토양비료학회지
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• 제10권1호
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• pp.39-48
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• 1977

전국(全國) 21개소(個所)에서 실시한 수도(水稻)에 대(對)한 질소적량시험(窒素適量試驗) 결과(結果)를 검토(檢討)하여 다음과 같은 결과(結果)를 얻었다. 1. 일반품종(一般品種)의 무질소구(無窒素區)와 질소구(窒素區)의 수량(收量)은 다같이 보통답(普通畓)>사질답(砂質畓)>습답(濕畓)의 순(順)이었고 통일품종(統一品種)에서는 무질소구(無窒素區) 수량(收量)은 사질습답(砂質濕畓)>사질답(砂質畓)>보통답(普通畓)=식질습답(埴質濕畓)의 순(順)이었으나 질소구수량(窒素區收量)은 보통답(普通畓)>사질습답(砂質濕畓)>사질답(砂質畓)>식질습답(埴質濕畓)의 순(順)이었다. 즉 통일품종(統一品種)은 사질답(砂窒畓)에서 무비재배(無肥栽培)의 적응력(適應力)이 높다는 특성(特性)을 보여 주었다. 2. 질소(窒素)의 시비응수(施肥應酬)는 보통답(普通畓)에서는 높고 사질답(砂質畓)과 습답(濕畓)에서는 낮았다. 질소(窒素) 1kg당(當) 정조(精租) 생산효율은 통일품종(統一品種)에서 보통답(普通畓) 16.6, 사질답(砂質畓) 10.5, 습답(濕畓) 8.6~11.4kg/10a이고 일반품종(一般品種)에서는 각각(各各) 12.6, 6.3, 6.6~9.3이었다. 3. 사질답(砂質畓)의 벼는 보통답(普通畓)에 비(比)하여 등숙률(登熟率)(일반품종(一般品種)에서) 또는 등숙율(登熟率)과 천립중(千粒重)(통일품종(統一品種)에서)이 모두 높았다. 보통답(普通畓)에서 질소응수(窒素應酬)가 큰 것은 주로 수수(穗數)의 증가(增加)가 크기 때문이었다. 4. 평균(平均) 질소적량(窒素適量)은 통일품종(統一品種)에서 보통답(普通畓) 19.4, 사질답(砂質畓) 14.6, 습답(濕畓) 11.6~13.4kg/10a이고 일반품종(一般品種)에서는 각각(各各) 15.9, 10.2, 8.7~12.7kg/10a이었다. 5. 보통답(普通畓)에서는 생산력이 높을수록 질소적량(窒素適量)도 높아지는 관계(關係)를 보여 주었으나 사질답(砂質畓)과 습답(濕畓)에서는 그러한 관계(關係)가 없었다. 6. 표토중(表土中) $SiO_2$와 OM함량(含量)에 근거한 질소적량(窒素適量) 결정식(決定式)에서 얻은 값과 포장시험(圃場試驗)에서 얻은 실제(實際) 적량치간(適量値間)에는 차이(差異)가 컸으나 두 값간에는 서로 높은 상관관계(相關關係)가 있으므로 질소결정식(窒素決定式)은 품종(品種)과 토양종류(土壤種類)의 요인등(要因等)을 보정(補正)하여 발전(發展)시킬 필요(必要)가 있을 것이다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.139-146
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• 2002

The characteristics and prediction model for the shear strength of unsaturated residual soils was studied. In order to investigate the influence of the net normal stress on the shear strength, unsaturated triaxial tests and SWCC tests were carried out varying the net normal stress, and the experimental data for unsaturated shear strength tests were compared with predicted shear strength envelopes using 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, tile 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 for the unsaturated shear strength was proposed.

• Structural Engineering and Mechanics
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• 제61권5호
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• pp.637-643
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• 2017

Carbon fiber reinforced polymers (CFRPs) have been recently investigated as an alternative material for Geosynthetics to improve soil properties. One of the factors influencing the fiber orientation and mechanical properties of CFRP is the effect of soil overburden pressure. This study investigates the tensile behavior of cast-in-place CFRP. During the curing time of specimens, a wide range of normal stress is applied on specimens sandwiched between the soils. Two different soil types are used to determine the effect of soil grain size on the mechanical properties of CFRP. Specimens are also prepared with different specifications such as curing time and mixing soil in to the epoxy. In this study, tensile tests are conducted to investigate the effect of such parameters on tensile behavior of CFRP. The experimental results indicate that by increasing the normal stress and soil grain size, the ultimate tensile strength and the corresponding strain of CFRP decrease; however, reduction in elastic modulus is not noticeable. It should be noted that, increasing the curing period of epoxy resin and mixing soil in to the epoxy have no significant effect on the tensile properties of CFRP.

• Journal of Microbiology and Biotechnology
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• 제32권5호
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• pp.564-574
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• 2022

Microbial diversity in the soil is responsive to changes in soil composition. However, the impact of soil amendments on the diversity and structure of rare and abundant sub-communities in agricultural systems is poorly understood. We investigated the effects of different Chinese herb residue (CHR) soil amendments and cropping systems on bacterial rare and abundant sub-communities. Our results showed that the bacterial diversity and structure of these sub-communities in soil had a specific distribution under the application of different soil amendments. The CHR soil amendments with high nitrogen and organic matter additives significantly increased the relative abundance and stability of rare taxa, which increased the structural and functional redundancy of soil bacterial communities. Rare and abundant sub-communities also showed different preferences in terms of bacterial community composition, as the former was enriched with Bacteroidetes while the latter had more Alphaproteobacteria and Betaproteobacteria. All applications of soil amendments significantly improved soil quality of newly created farmlands in whole maize cropping system. Rare sub-communitiy genera Niastella and Ohtaekwangia were enriched during the maize cropping process, and Nitrososphaera was enriched under the application of simple amendment group soil. Thus, Chinese medicine residue soil amendments with appropriate additives could affect soil rare and abundant sub-communities and enhance physicochemical properties. These findings suggest that applying soil composite amendments based on CHR in the field could improve soil microbial diversity, microbial redundancy, and soil fertility for sustainable agriculture on the Loess Plateau.

• 한국약용작물학회지
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• 제21권4호
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• pp.289-295
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• 2013

This study was carried out to investigate the cause of leaf discoloration occurring frequently in paddy cultivation. Chemical property of soil and inorganic nutrient component of leaf were analyzed on abnormal fields of 7 regions where leaf discoloration occurred severely and normal fields of 7 regions among ginseng garden. The pH of abnormal fields was strong acidic condition (pH 5.51) compare to normal fields of slightly acid condition (pH 6.42). Calcium and magnesium content in abnormal fields were lower distinctly than that of normal fields, while EC, organic matter, phosphate, and potassium content showed not distinct difference between abnormal and normal fields. Whereas calcium and magnesium content were distinctly high in normal fields, both of potassium and iron content of ginseng leaf were distinctly high in abnormal fields. In particular, iron content of abnormal fields was more 1.94 times in soil, and 3.03 times in leaf than that of normal fields. In soil chemical property, there were significant negative correlation between leaf discoloration ratio and soil pH, and there were also significant positive correlation between leaf discoloration ratio and iron content. In ginseng leaf, there were highly significant negative correlation between leaf discoloration ratio and calcium content, and there were also highly significant positive correlation between leaf discoloration ratio and iron content.

• Journal of Ginseng Research
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• 제48권2호
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• pp.229-235
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• 2024

Background: Plant health is directly related to the change in native microbial diversity and changes in soil health have been implicated as one of the main cause of root rot. However, scarce information is present regarding allelopathic relationship of Panax notoginseng root exudates and pathogenic fungi Fusarium oxysporum in a continuous cropping system. Methods: We analyzed P. notoginseng root exudate in the planting soil for three successive years to determine phenolic acid concentration using GC-MS and HPLC followed by effect on the microbial community assembly. Antioxidant enzymes were checked in the roots to confirm possible resistance in P. notoginseng. Results: Total 29 allelochemicals in the planting soil extract was found with highest concentration (10.54 %) of p-hydroxybenzoic acid. The HPLC showing a year-by-year decrease in p-hydroxybenzoic acid content in soil of different planting years, and an increase in population of F. oxysporum. Moreover, community analysis displayed negative correlation with 2.22 mmol. L^-1 of p-hydroxybenzoic acid correspond to an 18.1 % population of F. oxysporum. Furthermore, in vitro plate assay indicates that medium dose of p-hydroxybenzoic acid (2.5-5 mmol. L^-1) can stimulate the growth of F. oxysporum colonies and the production of macroconidia, as well as cell wall-degrading enzymes. We found that 2-3 mmol. L^-1 of p-hydroxybenzoic acid significantly increased the population of F. oxysporum. Conclusion: In conclusion, our study suggested that p-hydroxybenzoic acid have negative effect on the root system and modified the rhizosphere microbiome so that the host plant became more susceptible to root rot disease.

• 한국토양비료학회지
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• 제15권2호
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• pp.101-109
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• 1982

농가포장에서 실시한 '76~'79년의 비료 시험성적으로부터 수도의 통일계 품종에 대한 인산 및 칼리의 시비효과와 시비적량을 토양의 물리적 특성을 달리하는 답유형별로 검토하였으며, 이 중 '77년의 시험성적을 집중적으로 분석하여 토양화학 검정치에 따른 시비적량의 산출기준을 설정하였는 바, 그 결과를 요약하면 다음과 같다. 1. 답유형별로 산출한 인산의 시비적량 6.6-11.4kg/10a범위에서 미숙답>보통답>사질답>염해답${\fallingdotseq}$습답의 순이었고, 칼리의 시비적량은 7.0-11.3kg/10a범위에서 미숙답>습답>사질답>보통답${\fallingdotseq}$염해답의 순이었다. 2. 답유형별로 산출된 적정시비량은 사용하였을 때 각각의 무요소구에 대한 증수효과는 인산의 경우 3.5-7.5%, 칼리의 경우 2.2-91%의 범위에서 답유형별로 차이가 있었다. 인산의 효과는 미숙답에서, 칼리의 효과는 습답에서 가장 컸으며, 염해답에서는 인산과 칼리의 효과가 모두 비교적 높았다. 3. 답토양의 필지별 화학성분 검정치와 상대수량 지수의 관계에서 시비효과의 한계점인 토양중 유효인산의 임계함량은 보통답 약 100ppm, 사질답 약 200ppm이었고, 치환성 칼리 염기비(K/Ca+Mg${\times}100$)임계점은 보통답 약 8, 사질답 8이상이며, 습답에서는 나타나지 않았다. 4. 토양검정치(x)에 따른 시비적량(y) 산출식은 인산에 있어서는 보통답 y=11.270-0.048x, 사질답 y=13.383-0.061x이고 칼리에 있어서는 보통답 y=9.526-0.569x, 사질답 y=11.727-1.004x, 습답 y=12.574-0.558x이었다.

• Journal of Ecology and Environment
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• 제33권1호
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• pp.15-18
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• 2010

Mangroves are special plant communities that live along intertidal zones in tropical and subtropical areas. They are regarded as one of the most important types of natural ecosystem in the world because of the many ecosystem functions that they perform, of which water purification is the most complex. Mangrove ecosystems are conducive to the deposition and retention of heavy metals. So it is important to understand the impact of heavy metals on mangrove ecosystems, and especially on soil subsystems. We examined the levels of heavy metals in the soil of mangroves in the Dongzhaigang Mangrove National Nature Reserve. Dongzhaigang, the first mangrove nature reserve established in China, is located south of Haikou in Hainan Island and encompasses $33.37\;km^2$, of which mangroves comprise $20.56\;km^2$. To assess the impact of human activities, we collected a large number of soil samples in four sampling areas (the protection station, the harbor, a tour area, and Yeboluo island) in the study area. We measured the concentrations of Cu, Pb, Zn and Cd in the soil samples using the spectra of polyatomic molecules. The average concentrations of Cu, Pb, Zn and Cd were $5.04\;{\mu}g/g$, $10.36\;{\mu}g/g$, $20.06\;{\mu}g/g$ and $0.06\;{\mu}g/g$, respectively, and the heavy metal concentrations were lowest in the protected area, highest in the harbor, and intermediate in Yeboluo Island and the tour area. The heavy metal concentrations in the soil collected from different sample plots are related not only to the physical and chemical properties of the soil, but also to the heavy metal emitted by nearby pollution sources. Our analysis indicates that tourist boats are the main pollution sources in the study area.