• 한국토양비료학회지
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• 제48권1호
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• pp.50-56
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• 2015

This research was performed to test the hypothesis that the optimal fertilization rate for lettuce is various with soil moisture conditions. The experiment was conducted under a rainfall-intercepted facility in Suwon, South Korea from 2002 to 2003. Soil was irrigated at 30, 50, or 80 kPa of soil moisture tension at 15 cm soil depth in 2002 spring and fall and 20, 30, 50, or 80 kPa in 2003 spring. Fertilization was performed with four levels in spring for both years: none, 0.5, 1.0, and 1.5 times of the recommended N, P, and K fertilization rate. The irrigation amount increased with decreased irrigation starting point as soil moisture tension. The maximum yield was found at the lowest soil moisture tension in spring while irrigation at 50 kPa resulted in the greatest yield in fall. The yield responses of lettuce to fertilization rates were various with soil moisture condition. In spring, maximum yield was found at 1.0 or 1.5 times of the recommended fertilization rate at 20, 30, and 50 kPa irrigation while 0.5 or 1.0 times of fertilization rate resulted in the maximum yield in fall. Especially for 80 kPa irrigation in 2003 spring, yield was decreased by fertilization. It suggested that the optimum fertilization rate for lettuce is affected by soil moisture condition and that lower fertilization rate should be suggested when soil is managed in drier condition.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.106-113
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• 2002

In this study, a numerical analysis method for soil-pile interaction in frequency domain problem is presented. The total soil-pile interaction system is divided into two parts so called near field and far field. In the near field, beam elements are used for a pile and plain strain finite elements for soil. In the far field, dynamic fundamental solution for multi-layered half planes based on boundary element formulation is adopted for soil. These two fields are coupled using FE-BE coupling technique In order to verify the proposed soil-pile interaction analysis, the dynamic responses of pile on multi-layered half planes are simulated and the results are compared with the experimental results. Also, the dynamic response analyses of interface spring elements are performed. As a result, less spring stiffness makes the natural frequency decrease and the resonant amplitude increase.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.976-984
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• 2009

This study proposes a simple method that uses a simple mass-spring model to predict the natural frequency of a soil-pile-structure system in sandy soil. This model includes a pair of matrixes, i.e., a mass matrix and a stiffness matrix. The mass matrix is comprised of the masses of the pile and superstructure, and the stiffness matrix is comprised of the stiffness of the pile and the spring coefficients between the pile and soil. The key issue in the evaluation of the natural frequency of a soil-pile system is the determination of the spring coefficient between the pile and soil. To determine the reasonable spring coefficient, subgrade reaction modulus, nonlinear p-y curves and elastic modulus of the soil were utilized. The location of the spring was also varied with consideration of the infinite depth of the pile. The natural frequencies calculated by using the mass-spring model were compared with those obtained from 1-g shaking table model pile tests. The comparison showed that the calculated natural frequencies match well with the results of the 1-g shaking table tests within the range of computational error when the three springs, whose coefficients were calculated using Reese's(1974) subgrade reaction modulus and Yang's (2009) dynamic p-y backbone curves, were located above the infinite depth of the pile.

• 한국구조물진단유지관리공학회 논문집
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• 제6권3호
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• pp.91-96
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• 2002

There are many methods for analyzing underground box structures. One is the method of Iterative removal of tensional spring. The other is the method of modeling of ground to 8-node elastic-plastic planar element. In this study, We use inelastic soil spring element for analyzing underground box structures. First, if N-value is over 50, the results of inelastic soil spring method is the same as the method of 8-node planar element in last stage. Second, as N is increasing, element forces in two methods are generally decreasing. Third, as N-value is increasing, element forces in two method are generally decreasing and displacement has decreasing incline. This is the same as the force-displacement curve of general underground structures.

• Geomechanics and Engineering
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• 제25권3호
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• pp.221-231
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• 2021

A two dimensional model of linearly elastic soil spring used for the settlement analysis of the flexible mat foundation is suggested in this study. The spring constants of the soils underneath the foundation were modeled assuming uniformly vertical load applied onto the foundation. The soil spring constants were back calculated using the three-dimensional finite element analysis with Midas GTS NX program. Variation of the soil spring constants was modeled as a two-dimensional polynomial function in terms of the normalized spatial distances between the center of foundation and the analytical points. The Lysmer's analog spring for soils underneath the rigid foundation was adopted and calibrated for the flexible foundation. For validations, the newly proposed soil spring model was incorporated into a two dimensional finite difference analysis for a square mat foundation at the surface of an elastic half-space consisting of soft clays. Comparative study was made for elastic soils where the shear wave velocity is 120~180 m/s and the Poisson's ratio varies at 0.3~0.5. The resulting foundation settlements from the two dimensional finite difference analysis with the proposed soil springs were found in good agreement with those obtained directly from three dimensional finite element analyses. Details of the applications and limitations of the modified Lysmer's analog springs were discussed in this study.

• Journal of Animal Science and Technology
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• 제61권6호
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• pp.324-332
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• 2019

This study aimed to identify the causality between climatic and soil variables affecting the yield of Italian ryegrass (Lolium multiflorum Lam., IRG) in the paddy field by constructing the pathways via structure equation model. The IRG data (n = 133) was collected from the National Agricultural Cooperative Federation (1992-2013). The climatic variables were accumulated temperature, growing days and precipitation amount from the weather information system of Korea Meteorological Administration, and soil variables were effective soil depth, slope, gravel content and drainage class as soil physical properties from the soil information system of Rural Development Administration. In general, IRG cultivation by the rice-rotation system in paddy field is important and unique in East Asia because it contributes to the increase of income by cultivating IRG during agricultural off-season. As a result, the seasonal effects of accumulated temperature and growing days of autumn and next spring were evident, furthermore, autumnal temperature and spring precipitation indirectly influenced yield through spring temperature. The effect of autumnal temperature, spring temperature, spring precipitation and soil physics factors were 0.62, 0.36, 0.23, and 0.16 in order (p < 0.05). Even though the relationship between soil physical and precipitation was not significant, it does not mean there was no association. Because the soil physical variables were categorical, their effects were weakly reflected even with scale adjustment by jitter transformation. We expected that this study could contribute to increasing IRG yield by presenting the causality of climatic and soil factors and could be extended to various factors.

• 한국지반공학회논문집
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• 제38권9호
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• pp.5-17
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• 2022

최근, 잔교식 말뚝 구조물의 응답스펙트럼해석 시 지반-말뚝 상호작용을 모사하기 위해 가상고정점(virtual fixed point) 및 탄성지반스프링(elastic soil spring) 방법에 관한 몇몇 연구가 수행되어 왔다. 그러나, 가상고정점 방법 및 탄성지반스프링 방법의 경우 지진 가속도 크기에 따라 변하는 지반 스프링 강성을 적절히 고려할 수 없으며, 현재까지 이를 고려한 잔교식 말뚝 구조물의 응답스펙트럼해석에 관한 연구는 부족한 실정이다. 그러므로 본 연구에서는 지진 가속도 크기에 따라 변하는 지반 스프링 강성을 고려하여 응답스펙트럼해석을 수행하였으며, 기존에 제시된 가상고정점 및 탄성지반스프링 방법과의 비교를 통해 잔교식 말뚝 구조물의 동적 거동을 평가하였다. 실험 및 해석을 비교한 결과, 가상고정점 모델의 경우 모멘트 차이가 최대 117% 발생하였고, Terzaghi(1955) 탄성지반스프링 모델의 경우 모멘트 차이가 최대 21% 발생하였다. 반면, API(2000) p-y 곡선을 바탕으로 지진 가속도 크기에 따라 변하는 지반 스프링 강성을 고려하여 응답스펙트럼해석을 수행하는 경우 실험 및 해석의 모멘트 차이가 최대 4% 미만으로 도출되어 실험모델의 응답을 가장 적절히 모사하는 것으로 나타났다.

• 한국재난정보학회 논문집
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• 제3권2호
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• pp.147-169
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• 2007

This study investigates the reinforcing effects of the Multi-bar Spring nails with respect to the conventional Soil-nails in artificial slopes. Based on wide experience related to design and construction, soil nails have been widely applied to reinforce slope in the world. Multi-bar spring nails are one of the improved soil nailing methods. These method maximizes bending, shearing, pull-out resistance for those multi-nails, not unit nail, that are inserted in the borehole using special spacer at regular intervals. In addition, because cutting plane is confined effect resulting from a pressured plate at the end of the nails with compression spring equipment, slope stability is secured using MS-nailing method. Analyzing bending, pull-out, shearing condition of MS-nail, it was examined throughly elastic region, load transfer capacity, reinforcing effect on cutting plate of MS-nails. In addition, Pilot and laboratory tests, numerical analysis were carried out to verify the superiority of MS-nailing method. In case, MS nailing method is applied to reinforce artificial slope, it was analyzed that bending, pull-out, shearing resistance was increased more than existing nailing method was applied. In this study, it was shown that surface failure was more or less prevented using MS-nailing method, confining effect on cutting plane using spring stuck to flexible equipment.

• 한국지하수토양환경학회지:지하수토양환경
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• 제28권5호
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• pp.25-35
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• 2023

This study aimed to classify spring types based on the hydrogeological characteristics of springs in Yongsu-ri~Hamo-ri coastal area in western part of Jeju Island. The springs in study area can be broadly categorized into three groups: perched groundwatrer springs (soil type), perched groundwater springs (sediment type), and basal groundwater springs. The perched groundwater springs of soil type correspond to springs where groundwater seeps out from the perched aquifer formed in the soil layer due to the development of clayey Kosan Formation beneath the surface. Because of the low hydraulic conductivity of soil layer, the average of spring discharge is less than 1 m³/day. The quality of spring water is significantly influenced by agricultural activities, resulting in high nitrate nitrogen concentrations and electrical conductivity. While the perched groundwater springs (sediment type) of the Suwolbong Tuff, which are located in the upper part of Kosan Formation, exhibited relatively higher discharge rates, their water quality was similar to soil-type springs. Basal groundwater springs are located in the zone of basal groundwater, mostly near the coastline. This type of spring appears to discharge of up to 3,707 m³, and the salinity content varies with the tidal fluctuations, especially increasing significantly during dry seasons.

• 한국지반환경공학회 논문집
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• 제14권4호
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• pp.59-66
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• 2013

현재 해상풍력시스템의 거동 해석은 지반을 고정단으로 가정한 채로 수행하는 것이 일반적이라고 알려져 있다. 지반의 연성이 고려될 경우 해상풍력시스템의 고유 주파수뿐만 아니라 기초구조물 설계를 위한 하중 또한 변화할 것이라고 예상되나, 이에 대한 연구는 아직 미미한 실정이다. 이에 따라, 본 연구는 기초구조물의 연성을 고려하여 시스템 해석을 수행할 경우 시스템의 고유 주파수와 하중의 변화를 살펴보기 위한 목적으로 수행되었다. 해상풍력시스템의 해석을 위하여 풍력발전기 해석프로그램인 GH-Bladed를 활용하였으며, 해석 시에는 coupled spring 모델과 winkler spring 모델을 활용하여 기초구조물의 연성효과를 고려하였다. 해석결과 지반의 연성 고려방안 중 winkler spring 모델을 적용하여 산정한 시스템 1차모드 및 하중이 지반을 고정단으로 가정한 해석결과와 비교하여 감소하는 것을 확인하였으며, 이를 통하여 지반의 연성이 시스템의 거동에 미치는 영향을 관찰하였다.