• Research in Plant Disease
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• v.10 no.4
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• pp.310-312
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• 2004

Pseudomonas syringae pv. actinidiae is the causative agent of bacterial canker in kiwifruit. A nested PCR detection method that uses primers designed from the cfl gene, involved in production of the phytotoxin coronatine, was applied on soil samples. These primers yielded 665 and 310-bp fragments in consecutive PCR amplification step with DNA from soil inoculated with Korean strain of P. syringae pv. actinidiae. This system was applied to survey soil samples from a kiwifruit orchard destroyed by bacterial canker. A specific 310-bp PCR product was obtained from all six samples of soil tested.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1224-1227
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• 2006

It has been recognized unsaturated soil behaviour playing an important role in geomechanics. Up to now, only a few experimental data are available for the technical difficulties related to both volume changes and suction measurements. In this study, the volume changes of unsaturated compacted silty soil were monitored with proximeter (i.e. non-contactable transducer) during various triaxial compression tests, which gave a realistic estimation in the volume changes of unsaturated soil sample. The measurement of volume changes were performed with 0.5% of the maximum error under the axial strain ratio of less than 10%. The experimental results have revealed that the mechanical behaviour of unsaturated soil can be significantly affected by the matric suction. During the shearing processes, the level of maximum deviator stress under the initial suction pressure of 50kPa was higher than that under the initial suction pressure of 10kPa. On the other hand, the volume changes became smaller under the increase in the initial suction pressure.

• Geomechanics and Engineering
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• v.20 no.5
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• pp.433-445
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• 2020

A new code, called PRaFULL (Piled Raft Foundation Under Lateral Load), was developed for the analysis of laterally loaded Combined Pile Raft Foundation (CPRF). The proposed code considers the contribution offered by the raft-soil contact and the interactions between all the CPRF system components. The nonlinear behaviour of the reinforced concrete pile and the soil are accounted. As shallower soil layers are of great relevance in the lateral response of a pile foundation, PRaFULL includes the possibility to consider layered soil profiles with appropriate properties. The shadowing effect on the ultimate soil pressure is accounted, when dealing with pile groups, as proposed by the Strain Wedge Model. PRaFULL BEM code obviously requires less computational resources compared to FEM (Finite Element Method) or FDM (Finite Difference Method) codes. The proposed code was validated in the linear elastic range by comparisons with the code APRAF (Analysis of Piled Raft Foundations). The reliability of the procedure to predict piled raft performance was then verified in nonlinear range by comparisons with both centrifuge tests and computer code PRAB.

• Journal of Ocean Engineering and Technology
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• v.24 no.3
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• pp.52-58
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• 2010

This study investigated the engineering properties of waste tire powder-bottom ash added composite soil, which was developed to recycle dredged soil, bottom ash, and waste tire powder. Test specimens were prepared using 5 different percentages of waste tire powder content(0%, 25%, 50%, 75%, and 100% by weight of the dry dredged soil), three different percentages of bottom ash content (0%, 50%, and 100% by weight of the dry dredged soil), and three different particle sizes of waste tire powder (0.1~2 mm, 0.9~5 mm, and 2~10 mm). Several series of unconfined compression tests, direct shear tests, and flow tests were conducted. The experimental results indicated that the waste tire powder content, particle size of waste tire powder, and bottom ash content influenced the strength and stress-strain behavior of the composite soil. The flow value increased with an increase in water content, but decreased with an increase in waste tire powder content.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.237-249
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• 2002

Nonlinearity and anisotropy of soil should be considered for the exact prediction of deformation before the failure state. In this study, a new constitutive model is developed in which the nonlinearity of soil is formulated by Ramberg-Osgood equation and the soil anisotropy is implemented by the cross-anisotropic elasticity. Nonlinear anisotropic model and other models for comparison are used to analyze the simple boundary value problems and the circular footing problem. In the results, the anisotropic ratio of elastic modulus is a key value for the bulk modulus of soil, the coeffcient of earth pressure at rest, and the slope of effective stress paths. Furthermore, it is found that the nonlinearity of soil considering the in-situ stresses has the great influence on the magnitude of settlements.

• Geomechanics and Engineering
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• v.16 no.6
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• pp.577-588
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• 2018

A major concern in deep excavation project in soft clay deposits is the potential for adjacent buildings to be damaged as a result of the associated excessive ground movements. In order to accurately determine the wall deflections using a numerical procedure such as the finite element method, it is critical to use the correct soil parameters such as the stiffness/strength properties. This can be carried out by performing an inverse analysis using the measured wall deflections. This paper firstly presents the results of extensive plane strain finite element analyses of braced diaphragm walls to examine the influence of various parameters such as the excavation geometry, soil properties and wall stiffness on the wall deflections. Based on these results, a multivariate adaptive regression splines (MARS) model was developed for inverse parameter identification of the soil relative stiffness ratio. A second MARS model was also developed for inverse parameter estimation of the wall system stiffness, to enable designers to determine the appropriate wall size during the preliminary design phase. Soil relative stiffness ratios and system stiffness values derived via these two different MARS models were found to compare favourably with a number of field and published records.

• Earthquakes and Structures
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• v.20 no.1
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• pp.87-96
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• 2021

Ground motions recorded in near-fault sites, where the rupture propagates toward the site, are significantly different from those observed in far-fault regions. In this research, finite element modeling is used to investigate the effect of pile cap stiffness on the seismic response of soil-pile-structure systems under near-fault ground motions. The Von Wolffersdorff hypoplastic model with the intergranular strain concept is applied for modeling of granular soil (sand) and the behavior of structure is considered to be non-linear. Eight fault-normal near-field ground motion records, recorded on rock, are applied to the model. The numerical method developed is verified by comparing the results with an experimental test (shaking table test) for a soil-pile-structure system. The results, obtained from finite element modeling under near-fault ground motions, show that when the value of cap stiffness increases, the drift ratio of the structure decreases, whereas the pile relative displacement increases. Also, the residual deformations in the piles are due to the non-linear behavior of soil around the piles.

• Journal of Microbiology and Biotechnology
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• v.15 no.4
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• pp.701-709
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• 2005

An efficient method of selecting an antagonistic strain for use as a biological control agent strain was developed. In this improved method, the surface tension reduction potential of an isolate was included in the 'decision factor,' in addition to two other factors; the growth rate and pathogen inhibition. By using a statistically designed method, an isolate from the soil was selected and identified as Bacillus sp. GB 16. In the pot test, this strain showed the best performance among the isolated strains. The lowest disease incidence rate and fastest seed growth were observed when the Bacillus sp. GB 16 was used. The action of the surface tension reducing component was assumed to enhance the wetting, spreading, and residing of the antagonistic strain in the rhizosphere. This result showed that the improved selection method was quite effective in selecting the best antagonistic strain for the biological control of soilborne infectious plant pathogens.

• Microbiology and Biotechnology Letters
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• v.23 no.5
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• pp.550-555
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• 1995

A strain of Pseudomonas sp. isolated from soil was shown to produce a high level of extracellular endo-inulinase. In this work, the endo-inulinase gene (inu1) of the bacterial strain was cloned into the plasmid pBR322 by using EcoRI restriction endonuclease and E. coli HB101 as a host strain. One out of 7, 000 transformants obtained from the above cloning experiment formed a clear zone around its colony on the selective medium supplemented with 2.0% inulin after a prolonged incubation at 37$\circ$C and subsequent cold shock treatment. The functional clone was found to carry a recombinant plasmid (pKMG50) with a 3.7 kb genomic insert containing the genetic information for the inulinase activity. The inulinase from E. coli HB101/pKMG50 was proved to be an endo-acting enzyme and produced constitutively in the recombinant E. coli cells. Zymogram of the enzyme from the recombinant cells with inulin substrate indicated that the molecular mass of the active protein was 190 Kd, while that of the endo-inulinase from the Pseudomonas strain was 170 Kd. This size discrepancy suggested that the inulinase from the recombinant E. coli HB101 cells might be the initial product of translation, not the mature form produced in the strain of Pseudomonas sp..

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.448-456
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• 2010

The mechanical behavior of granular soils is affected by particle bonding including natural cementation. This study addresses a simple model of small strain stiffness and salt concentration based on wave measurements of salt-cemented particulate media. Published models of artificially cemented soils with different curing methods and several types of cementation agents are reviewed. Glass beads with the median diameter of D50 = 0.5mm are prepared in rectangular cells using the water-pluviated method in salt water with different concentrations. Piezo disk elements and bender elements embedded in the cell are used for the measurements of compressional and shear waves. The relationships between elastic wave velocities and salt concentration show an exponential function. The measured small strain stiffness matches well the predicted small strain stiffness based on micromechanics for simple cubic monosized sphere particles. This study demonstrates that the salt concentration in salt-cemented specimen may be evaluated by using elastic wave velocities.