• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.81-88
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• 1998

During an earthquake, there are three main components of excitation : horizontal excitation of the ground, vertical excitation of the pile due to superstructure feedback produced by vertical excitation of the ground, and the seawater excitation induced by the vertical ground shaking, that is, "the seaquake." These excitations could have effects on the soil plugs in open-ended pipe piles installed at offshore sites. In this study, seaquake excitation induced by the vertical ground shaking was simulated by pulsing the water pressure at the seabed. During a seaquake, due to induced excess porewater pressure and pressure gradients in the soil, the capacity of open-ended pipe piles installed in a simulated sea depth of greater than 220 m was reduced serevely and the soil plugging resistance was degraded by more than 80%. The soil plug was failed because of the upward seepage forces that developed in the soil plug due to excess pore water pressure produced in the bottom of the soil plug during the seaquake. The compressive capacity of an open-ended pile in a simulated sea depth of less than 220m was reduced only by about 10%, and the soil plug resistance was degraded by less than 5%.s than 5%.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.98-105
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• 2009

This paper presents the characteristics of soil ionization for different water contents, and the parameters associated with the dynamic properties of a simple model grounding system subject to lightning impulse currents. The laboratory experiments for this study were carried out based on factors affecting the soil resistivities. The soil resistivities are adjusted with water contents in the range from 2 to 8% by weight. A test cell with a spherical electrode buried in the middle of the hemispherical container was used. As a result, the electric field intensity $E_c$ initiating ionization is decreased with the reduction of soil resistivities. Also, as the water content increased, the pre-ionization resistance $R_1$ and the post-ionization resistance $R_2$ became lower with increasing current amplitude. The time-lag to ionization $t_1$ and the time-lag to the second current peak $t_2$ at high applied voltages were significantly shorter than those of low applied voltages. It was found that the soil ionization behaviors are highly dependent on the water content and the applied voltage amplitude.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.267-274
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• 2021

Among several methods for determining the allowable lateral resistances of piles, the subgrade reaction method and ultimate lateral resistance method are generally used. To determine the effects of the soil conditions, pile head restraint conditions, and pile lengths on determining the allowable lateral resistances of piles, computations of the allowable lateral resistances of piles using the two methods were executed, and the computation results were compared. For piles in soft cohesive soil, the pile design is governed by the allowable lateral resistance of a pile from subgrade soil reaction method regardless of the pile head restraints conditions and pile lengths. The allowable lateral resistance of a pile from the ultimate lateral resistance governs the design as the undrained shear strength increases. Except for the case of a short pile, which is installed in loose granular soil, the allowable lateral resistance of a pile from ultimate lateral resistance governs the design of laterally loaded piles. According to this study, computation of the ultimate lateral resistance of a pile is needed, even though some opinions suggest that the design of a laterally loaded pile is satisfied only by the subgrade reaction method. The pile width barely influences the coefficient of horizontal subgrade reaction. Realistically, the effect of the pile width can be disregarded in the condition of common pile widths of 20~90cm.

• Journal of the Korean Geotechnical Society
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• v.32 no.12
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• pp.15-22
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• 2016

The magnitude of the lateral resistance that resists the lateral movement of the pile is controlled by the amount of the pile movement and the strength and stiffness of soil. In this paper, we proposed an equation which produces the ultimate lateral resistance of the laterally loaded single pile in sand using the strain wedge model of the soil deformation. The ultimate lateral resistance in strain wedge model is composed of earth pressure of wedge rear, the shear resistance on the side of the wedge, and the frictional resistance between pile and ground. The ultimate lateral resistance determined by the proposed equation was compared with the Ashour, F.D.M., field test in sand. As a result, the error of the proposed equation and Ashour theory, field test, F.D.M were respectively 1.03%, 0.40~3.32%, 6.02%.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.118-125
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• 2011

Conventional erosion function apparatus (EFA) which has been used to measure the hydraulic resistance of soil was improved to consider direction change of the current flow. Using improved apparatus, hydraulic resistance capacities of the artificially composed clayey soil and sandy soil were compared. Test result shows that scour rates which were measured under the bi-directional flow were much higher than those measured under unidirectional flow for both type soils. Scour rate of sandy soil was higher than that of clayey soil. Velocity averaged scour rate of specimen which was consolidated under the relatively large consolidation pressure is higher than that of specimen which is consolidated under small consolidation pressure, which means scour problem under bidirectional flow may be more serious for the deep seabed ground.

• Journal of Environmental Science International
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• v.21 no.11
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• pp.1307-1320
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• 2012

The purpose of this paper is to provide information on planting construction for healthy plant growth. To achieve this purpose, this study analyzed the planting type, planting density, withering rate, soil characteristics, and cambium electrical resistance (CER) of withered trees in an apartment complex with a high withering rate. The major plant groups examined consisted of native broad-leaved tree species (39.3%), native narrow-leaved tree species (24.2%), and native broad-leaved - exotic narrow-leaved tree species (16.4%). The planting density of the green area, where trees were planted from 0.0 to 0.3 trees per unit area, was measured as 98.4%. Withered trees were found in 19 of the 20 planted species, and the withering rate was 41.8% (610 withered/1,461 planted). Withering rates for tree species were measured as follows: Sophora japonica and Salix babylonica (100.0%), Magmolia denudata (84.3%), Lindera obtusiloba (74.7%), cornus kousa (69.3%), acer triflorum (69.2%), diospyros kaki (66.7%), Prunus yedoensis (62.8%), Acer palmatum (52.6%), Prunus armeniaca (51.1%), Chaenomeles sinensis (43.7%), Ginkgo biloba (40.9%), Zelkova serrata (31.0%), Cornus officinalis (28.6%), Taxus cuspidata (25.6%), Pinus densiflora (21.4%), Pinus parviflora (15.2%), Pinus strobus (14.6%), and Abies holophylla (10.3%). Soil chemical analyses for 18 samples revealed that as the withering rate increased, the following occurred: (a) the ratio of silt and clay in soil increased; (b) the soil pH, organic matter rate, nitrogen, available phosphorus, and cation exchange capacity (CEC) in samples were graded as "inadequate," based on the plant grading evaluation; and (c) the NaCl and cation exchange capacity were evaluated as "somewhat satisfactory." The measurement of CER for withering rate shows electrical resistance for higher withering rate are higher, which could predict that a tree will not grow well.

• Earthquakes and Structures
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• v.19 no.4
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• pp.273-286
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• 2020

The pile group foundation is widely used for gravity pier of high-speed railway bridges in China. If a moderate or strong earthquake occurs, the pile-surrounding soil will exhibit obvious nonlinearity and significant pile group effect. In this study, an improved pushover analysis model for the pile group foundation with consideration of pile group effect is presented and validated by the quasi-static test. The improved model uses simplified springs to simulate the soil lateral resistance, side friction and tip resistance. PM (axial load-bending moment) plastic hinge model is introduced to simulate the impact of the axial force changing of pile group on their elastic-plastic characteristics. The pile group effect is considered in stress-stain relations of the lateral soil resistance with a reduction factor. The influence factors on nonlinear characteristics and plastic hinge distribution of the pile group foundation are discussed, including the pier height, longitudinal reinforcement ratio and stirrup ratio of the pile, and soil mechanical parameters. Furthermore, the displacement ductility factor, resistance increase factor and yielding stiffness ratio are provided to evaluate the seismic performance of soil-pile system. A case study for the pile group foundation of a railway simply supported beam bridge with a 32 m-span is conducted by numerical analysis. It is shown that the ultimate lateral force of pile group is not determined by the yielding force of the single one in these piles. Therefore, the pile group effect is essential for the seismic performance evaluation of the railway bridge with pile group foundation.

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.61-69
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• 2022

In this study, a large-scale direct shear test was performed to evaluate the shear characteristics of the pile-soil interface according to the fines content and confining pressure conditions as a reasonable evaluation method of the pullout resistance performance of pile considering the soil conditions. It was found that the shear stress was greatly generated under the conditions of high normal stress and low fines content. In addition, the maximum shear stress was found to be rather large under the conditions of the same normal stress and fines content, when pile surface had high roughness. The internal friction angle decreased at the pile-soil interface, when the fines content in the ground increased. On the other hand, the cohesion decreased under the condition of high fines content. And the internal friction angle and cohesion were large regardless of the fines content in the model ground, when the roughness of the pile surface was high.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6C
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• pp.359-366
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• 2008

The load distribution and deformation of pile subjected to axial loads are evaluated by a load-transfer method. The emphasis is on quantifying the effect of coupled soil resistance that is closely related to the ratio of pile diameter to soil modulus $(D/E_s)$ and the ratio of total shaft resistance against total applied load $(R_s/Q)$, in rock-socketed drilled shafts using the coupled load-transfer method. The proposed analytical method that takes into account the soil coupling effect was developed using a modified Mindlin's point load solution. Through comparisons with field case studies, it was found that the proposed method in the present study estimated reasonable load transfer behavior of pile and coupling effects due to the transfer of shaft shear loading, and thus represents a significant improvement in the prediction of load deflections of drilled shafts.

• Journal of Microbiology and Biotechnology
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• v.26 no.9
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• pp.1542-1550
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• 2016

This is the first report that paromomycin, an antibiotic derived from Streptomyces sp. AG-P 1441 (AG-P 1441), controlled Phytophthora blight and soft rot diseases caused by Phytophthora capsici and Pectobacterium carotovorum, respectively, in chili pepper (Capsicum annum L.). Chili pepper plants treated with paromomycin by foliar spray or soil drenching 7 days prior to inoculation with P. capsici zoospores showed significant (p < 0.05) reduction in disease severity (%) when compared with untreated control plants. The disease severity of Phytophthora blight was recorded as 8% and 50% for foliar spray and soil drench, respectively, at 1.0 ppm of paromomycin, compared with untreated control, where disease severity was 83% and 100% by foliar spray and soil drench, respectively. A greater reduction of soft rot lesion areas per leaf disk was observed in treated plants using paromomycin (1.0 μg/ml) by infiltration or soil drench in comparison with untreated control plants. Paromomycin treatment did not negatively affect the growth of chili pepper. Furthermore, the treatment slightly promoted growth; this growth was supported by increased chlorophyll content in paromomycin-treated chili pepper plants. Additionally, paromomycin likely induced resistance as confirmed by the expression of pathogenesis-related (PR) genes: PR-1, β-1,3-glucanase, chitinase, PR-4, peroxidase, and PR-10, which enhanced plant defense against P. capsici in chili pepper. This finding indicates that AG-P 1441 plays a role in pathogen resistance upon the activation of defense genes, by secretion of the plant resistance elicitor, paromomycin.