• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1047-1054
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• 2005

The purpose of this study is the understanding to changes in the characteristic of soil structure and classification, atterberg limits, undrained shear strength and consolidation of clayey soil dependent on pH of soil pore water. A series of tests including consistency tests, uniaxial compressive tests, vane tests and oedometer tests are performed on. The test results indicated that pH changes in the soil pH resulted in changes in the soil structure and classification, stress-strain behavior. Specially, when pH is conditioned to 7, liquid limit, undrained shear strength and preconsolidation pressure are the largest.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.211-220
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• 2002

CGS(Compaction Grouting System) is widely used in reinforcement of structural foundation and ground improvement in soft ground. But the effects of ground improvement depending on the type of soil must be studied in order to adopt in various soils (granular soil and cohesive soil). In this study, characteristics of ground improvement (the increase of N value, increase in unit weight, vertical displacement on the ground surface) by CGS method was compared through two cases that were performed in granular and cohesive soil. The results show that the closer to the grout hole, the more increase in N value and this trend appear distinctly in granular soil. Unit weight of ground increase largely near by the grout hole and decrease in far from it independently of the soil type. The vertical displacement on the ground surface appeared in smaller area in case of granular soil than cohesive soil.

• Journal of the Korean Society of Safety
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• v.20 no.1 s.69
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• pp.101-106
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• 2005

When a underground structure is constructed at the site composed of soft soil, the behavior of a underground structure Is much affected by the motion of soft soil. Therefore, the effect of soil-structure interaction is an important consideration in the design of a underground structure such as tunnel at the site composed of soft soil. This paper presents the results of the study on dynamic response of tunnel structures and soil-structure interaction effects. The computer program SASSI was used in seismic analysis of tunnel structures because it is more capable of analyzing dynamic response or structures considering soil-structure interaction. As regards the results, the flexibility of surrounding soil affects dynamic response characteristics of tunnel structures and response of tunnel structures can be amplified.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.2
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• pp.109-115
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• 2006

Understanding characteristics of claypan soils has long been an issue for researchers and farmers because the high-clay subsoil has a pronounced effect on grain crop productivity. The claypan restricts water infiltration and storage within the crop root zone, but these effects are not uniform within fields. Conventional techniques of identifying claypan soil characteristics require manual probing and analysis which can be quite expensive; an expense most farmers are unwilling to pay. On the other hand, farmers would be very interested if this information could be obtained with easy-to-use field sensors. Two examples of sensors that show promise for helping in claypan soil characterization are soil profile strength sensing and bulk soil apparent electrical conductivity (ECa). Little has been reported on claypan soils relating the combined information from these two sensors with grain crop yield. The objective of this research was to identify the relationships of sensed profile soil strength and soil EC with nine years of crop yield (maize and soybean) from a claypan soil field in central Missouri. A multiple-probe (five probes on 19-cm spacing) cone penetrometer was used to measure soil strength and an electromagnetic induction sensor was used to measure soil EC at 55 grid site locations within a 4-ha research field. Crop yields were obtained using a combine equipped with a yield monitoring system. Soil strength at the 15 to 45 cm soil depth were significantly correlated to crop yield and ECa. Estimated crop yields from apparent electrical conductivity and soil strength were validated with an independent data set. Using measurements from these two sensors, standard error rates for estimating yield ranged from 9 to 16%. In conclusion, these results showed that the sensed profile soil strength and soil EC could be used as a measure of the soil productivity for grain crop production.

• The Journal of Engineering Geology
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• v.19 no.1
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• pp.33-41
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• 2009

In this study, some changes of soil characteristics in a field were analyzed to investigate the effect of heavy rainfall during rainy season. The heavy rainfalls were often induced geohazards like landslides. To do this, the reaching rainfall in the ground surface was investigated according to a condition of vegetation, and the change of soil characteristics induced by infiltrating rainfall was analyzed. The study site is a natural terrain located in Daedeok Science Complex. This site has same geology and soil condition whereas it has different vegetable condition. The rainfall records during the rainy season of 2006 and 2007 were selected. The rainfall records are based on the measuring date from Daejeon Regional Meteorological Administration adjacent to the study site. Also, the rainfall records according to the condition of vegetation were measured using rainfall measuring device made by ourselves. The soil tests were carried out about soil specimen sampled before and after rainfall, and then the change of soil characteristics related to rainfall and vegetation were analyzed. As the result, the density of vegetation was influenced by reaching rainfall quantity in the ground surface, and its influence intensity was decreased with rainfall intensity and rainfall duration. Also, it shows that degree of saturations, water contents, liquidities and shear resistances are directly influenced by heavy rainfalls.

• Journal of Korean Society of Forest Science
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• v.109 no.3
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• pp.313-324
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• 2020

This study investigated the environmental location effects that Larix kaempferi and mixed forests had on the early growth of wild-simulated ginseng (Panax ginseng C. A. Meyer) seedlings. Experimental plots were created in Larix kaempferi and mixed forests, and confirmed the location environments and growth characteristics of wild-simulated ginseng seedling. Our results showed that the soil properties, such as soil organic matter, total nitrogen, and cation exchangeable capacity were significantly higher in the mixed forest soil compared to the Larix kaempferi forest soil. Likewise, the growth characteristics of wild-simulated ginseng seedlings were significantly higher in mixed forestsd compare to the Larix kaempferi forest. Correlation analysis between tree species ratio, soil properties, and growth characteristics in the experimental plots determined that the soil properties and growth characteristics had significant positive correlation with the broad-leaved forest percentage. Growth characteristics of the wild-simulated ginseng seedlings were shown to have a significant positive correlation with organic matter, total nitrogen, and cation exchange capacities. This study has clearly demonstrated that the tree species ratio, and soil properties in Larix kaempferi and mixed forests were significantly correlated with the early growth of wild simulated ginseng seedlings. These results could help to improve the selection of suitable cultivation sites for wild-simulated ginseng.

• Korean Journal of Organic Agriculture
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• v.26 no.3
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• pp.427-437
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• 2018

In this study, microorganism community characteristics of organic managed soil which applied rye (Secale cereal L.) as green manure for 25 years, were determined. The chemical properties of organic soil showed high level of organic matter and available $P_2O_5$, while the level of exchangeable cation was low. The analysis of dehydrogenase activity and carbon source utilization indicated that the values in on organic soil were significantly higher than those of the control. It suggested that the microorganism community of organic soil had high microorganism activity, compared to the control. In addition, when the 16S rRNA gene-targeted NGS (Next generation sequencing) analysis was conducted to estimate the class of bacterial community, the class level of bacterial taxon composition on organic soil showed higher portion of Sphingobacteriia, Acidobacteriia, Gammaproteobacteria, Solibacteres and Planctomycetia. By base on the results of various reports in which organic managed soil had high portion of Acidobacteriia and Planctomycetia, the characteristic of taxon composition in organic soil, which showed the high percentages of Ktedonobacteria, Sphingobacteriia, Acidobacteriia and Gammaproteobacteria, was resulted from the application of rye as a green manure for the long term. However, further researches were needed because the crop effect was not considered in this study.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.70-74
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• 2005

Soil particles from rainfall flow into reservoir and give lots of influence In water quality because the geological conditions and landcover characteristics of imha basin have a weakness against soil loss. Especially, much soil particles induced to reservoir in shape of muddy water when it rains a lot because the geological characteristics of imha reservoir are composed of clay and shale layer. Therefore, field turbidity data can be Indirect-standards to estimate the soil erosion of imha basin. This study evaluated annual soil erosion using GIS-based RUSLE (Revised Universal Soil Loss Equation) and developed rainfall weighting value method using time-series rainfall data to estimate monthly soil erosion. In view of field turbidity data(2003 yr), we can find out monthly soil erosion with rainfall weighting value is more efficient than that with monthly rainfall data.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.7
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• pp.391-399
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• 2018

The site coefficients in the common requirements for seismic design codes, which were promulgated in 2017, were reevaluated and the standard design spectrum for soil sites were newly proposed in order to ensure the consistency of the standard design spectra for rock and soil sites specified in the common requirements. Using the 55 ground motions from domestic and overseas intraplate earthquakes, which were used to derive the standard design spectrum for rock sites, as rock outcropping motions, site response analyses of Korean soil were performed and its ground-motion-amplification was characterized. Then, the site coefficients for soil sites were reevaluated. Compared with the existing site coefficients, the newly proposed short-period site coefficient $F_a$ increased and the long-period site coefficient $F_v$ decreased overall. A new standard design spectrum for soil sites was proposed using the reevaluated site coefficients. When compared with the existing design spectrum, it could be seen that the proposed site coefficients and the standard design spectrum for soil sites were reasonably derived. They reflected the short-period characteristics of earthquake and soil in Korea.

• Structural Engineering and Mechanics
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• v.58 no.6
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• pp.1045-1075
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• 2016

Shallow footings are one of the most common types of foundations used to support mid-rise buildings in high risk seismic zones. Recent findings have revealed that the dynamic interaction between the soil, foundation, and the superstructure can influence the seismic response of the building during earthquakes. Accordingly, the properties of a foundation can alter the dynamic characteristics (natural frequency and damping) of the soil-foundation-structure system. In this paper the influence that shallow foundations have on the seismic response of a mid-rise moment resisting building is investigated. For this purpose, a fifteen storey moment resisting frame sitting on shallow footings with different sizes was simulated numerically using ABAQUS software. By adopting a direct calculation method, the numerical model can perform a fully nonlinear time history dynamic analysis to realistically simulate the dynamic behaviour of soil, foundation, and structure under seismic excitations. This three-dimensional numerical model accounts for the nonlinear behaviour of the soil medium and structural elements. Infinite boundary conditions were assigned to the numerical model to simulate free field boundaries, and appropriate contact elements capable of modelling sliding and separation between the foundation and soil elements are also considered. The influence of foundation size on the natural frequency of the system and structural response spectrum was also studied. The numerical results for cases of soil-foundation-structure systems with different sized foundations and fixed base conditions (excluding soil-foundation-structure interaction) in terms of lateral deformations, inter-storey drifts, rocking, and shear force distribution of the structure were then compared. Due to natural period lengthening, there was a significant reduction in the base shears when the size of the foundation was reduced. It was concluded that the size of a shallow foundation influences the dynamic characteristics and the seismic response of the building due to interaction between the soil, foundation, and structure, and therefore design engineer should carefully consider these parameters in order to ensure a safe and cost effective seismic design.