• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1991년도 봄 학술발표회 논문집
• /
• pp.29-33
• /
• 1991

This paper reports the application study of the ground reinforement under a buried pipeline subjected to differential settlement via a finite element modelling. The Soil-reinforrement interaction helps to mimimize the differential settlement between the adjoining pipe segments. The settlement pattern and deformation slope of a pipeline have been evaluated for a boundary condition at the joint between a rigid structure and apipeline. The analysis results are compared for both non-reinforied and reinforced cases to measure the effectiveness of the soil reinforcement for restraining the settlement of the pipeline.

• Earthquakes and Structures
• /
• 제17권5호
• /
• pp.521-532
• /
• 2019

This paper describes the construction of a laminar box for simulating the earthquake response of soil and structures. The confinement of soil in the transverse direction does not rely on the laminar frame but is instead achieved by two acrylic glass walls. These walls allow the behaviour of soil during an earthquake to be directly observed in future study. The laminar box was used to study the response of soil with structure-footing-soil interaction (SFSI). A single degree-of-freedom (SDOF) structure and a rigid structure, both free standing on the soil, were utilised. The total mass and footing size of the SDOF and rigid structures were the same. The results show that SFSI considering the SDOF structure can affect the soil surface movements and acceleration of the soil at different depths. The acceleration developed at the footing of the SDOF structure is also different from the surface acceleration of free-field soil.

• Geomechanics and Engineering
• /
• 제25권4호
• /
• pp.283-294
• /
• 2021

This paper presents a rigorous solution for spherical cavity expansion in unsaturated soils under constant suction condition. The hydraulic behavior that describes the saturation-suction relationship is modeled by a void ratio-dependent soil-water characteristic curve, which allows the hydraulic behavior to fully couple with the mechanical behavior that is described by an extended critical state soil model for unsaturated soil through the specific volume. Considering the boundary condition and introducing an auxiliary coordinate, the problem is formulated to a system of first-order differential equations with three principal stress components and suction as basic unknowns, which is solved as an initial value problem. Parameter analyses are conducted to investigate the effects of suction and the overconsolidation ratio on the overall expansion responses, including the pressure-expansion response, the distribution of the stress components around the cavity, and the stress path of the soil during cavity expansion. The results reveal that the expansion pressures and the distribution of the stress components in unsaturated soils are generally higher than those in saturated soils due to the existence of suction.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
• /
• pp.463-470
• /
• 1998

The boundary/finite element analysis for the seismic wave amplifications due to nonhomogeneous alluvial deposits was performed in this study. For numerical analysis, the homogeneous linear elastic soil half-space was modeled by using the 3-node isoparametric boundary elements and the inhomogeneous alluvial deposit was modeled by using the 8-node isoparametric finite elements. The two elements at interface were coupled together by the equilibrium condition of the tractions and the compatibility condition of the displacements. As a prarmetric variable, the incident angle and the dimensionsless frequency of the SH, P and SV-waves and the shear wave velocity ratio and the mass density ratio between the half-space and the alluvial deposit were selected.

• 한국전산구조공학회논문집
• /
• 제29권6호
• /
• pp.499-512
• /
• 2016

경계반력법은 일반적인 복합법에서 필요한 진동수영역과 시간영역의 반복 작업이 필요없는 두 단계의 시간수영역 부구조법이다. 경계반력법은 다음의 두 단계로 나누어진다: (1) 진동수영역에서 선형구간과 비선형구간 경계에서 경계반력계산, (2) 시간영역에서 경계반력을 이용한 파동방사형문제 해석. 이때 시간영역에서는 파동방사형문제를 모사하기 위해 근역지반을 모델링한다. 이 연구에서는 면진원전구조물의 비선형 SSI 해석을 위한 BRM 해석의 근역지반 모델링 범위에 따른 응답을 평가하였다. 이를 위해 등가선형 SSI 문제를 이용하여 매개변수해석을 수행하였다. BRM 응답의 정확성을 평가하기 위해 BRM 응답은 재래의 SSI 해석의 응답과 비교하였다. 수치해석결과 BRM 해석을 위한 근역지반 모델링 범위는 기초의 크기뿐만 아니라 지반조건의 영향을 받았다. 마지막으로, BRM 해석을 면진원전구조물의 비선형 SSI 해석에 적용하므로 BRM의 정확성과 효율성을 입증하였다.

• 한국지반신소재학회논문집
• /
• 제6권3호
• /
• pp.9-16
• /
• 2007

토양증기추출공법(SVE)은 불포화 지반상태에서 휘발성 유기화합물(VOCs)과 유류오염 물질을 제거하는데 효과적이고 경제적인 공법중의 하나이다. 본 연구에서는 기존 연약지반의 지반개량시 사용된 연직배수재(PVDs)를 토양증기추출시스템에 적용하여 짧은 공기배출거리로 최대한 신속하게 오염물질을 제거할 수 있게 하여 투기계수가 낮은 지반에서 오염된 토양을 효과적으로 복원할 수 있는 토양증기추출공법을 적용하는데 목적이 있다. 연직배수재를 이용한 토양증기추출시스템 적용시 실제 현장에서 나타나는 무한 경계 조건을 만족하기 위해서 실내에서 파일럿 규모의 오염복원 모형실험을 결과로 유한경계조건 시스템에서 이미지웰 중첩이론을 이용하여 압력분포를 가정하였다. 즉, 압력강하가 없는 일정수두 경계조건 상태와 토조의 상 하부와 같이 흐름이 없는 불투수경계조건 상태를 유지하기 위해서 이미지웰 중첩이론을 도입하여 경계조건을 수립하였다. 결과, 공기흐름률이 증가할수록 흐름비율도 증가하였다. 따라서 높은 흐름률에 대한 흐름비율도 더 커지게 되는 것이고, 최적화과정동안 공기흐름률은 측정 압력수두와 이미지웰 중첩이론으로부터 구해진 이론 압력수두의 오차율에 미치는 가장 중요한 인자로 판단된다.

• 한국지진공학회논문집
• /
• 제27권1호
• /
• pp.25-35
• /
• 2023

Considering the non-linear behavior of structure and soil when evaluating a nuclear power plant's seismic safety under a beyond-design basis earthquake is essential. In order to obtain the nonlinear response of a nuclear power plant structure, a time-domain SSI analysis method that considers the nonlinearity of soil and structure and the nonlinear Soil-Structure Interaction (SSI) effect is necessary. The Boundary Reaction Method (BRM) is a time-domain SSI analysis method. The BRM can be applied effectively with a Perfectly Matched Layer (PML), which is an effective energy absorbing boundary condition. The BRM has a characteristic that the magnitude of the response in far-field soil increases as the boundary interface of the effective seismic load moves outward. In addition, the PML has poor absorption performance of low-frequency waves. For this reason, the accuracy of the low-frequency response may be degraded when analyzing the combination of the BRM and the PML. In this study, the accuracy of the analysis response was improved by adjusting the PML input parameters to improve this problem. The accuracy of the response was evaluated by using the analysis response using KIESSI-3D, a frequency domain SSI analysis program, as a reference solution. As a result of the analysis applying the optimal PML parameter, the average error rate of the acceleration response spectrum for 9 degrees of freedom of the structure was 3.40%, which was highly similar to the reference result. In addition, time-domain nonlinear SSI analysis was performed with the soil's nonlinearity to show this study's applicability. As a result of nonlinear SSI analysis, plastic deformation was concentrated in the soil around the foundation. The analysis results found that the analysis method combining BRM and PML can be effectively applied to the seismic response analysis of nuclear power plant structures.

• 한국지반공학회논문집
• /
• 제29권8호
• /
• pp.75-84
• /
• 2013

지반의 동결현상은 일반적으로 대기와 지반의 온도차이로 발생하는 열흐름에 의해, 지반에 존재하는 물이 동결되어 지반의 물리적 성질이 변하는 현상을 일컫는다. 동결현상 해석에 필요한 지중온도 변화는 크게 대기와 지반의 경계층에서 발생하는 열유동과 지중 내에서 흙을 구성하는 성분들의 열전도 현상으로 설명할 수 있다. 따라서 지표면의 경계조건과 지반의 열적 특성은 동결지반 온도분포 해석에 중요한 인자들이다. 지표면 경계조건은 대기온도, 지표의 식생상태, 토질조건을 포함한 간편상수법들이 제시되어 있다. 대기온도 변화에 따른 지표의 열전달을 설명하는 대표적인 열물성 값은 지표면에서의 n-factor와 대류 열전달계수이다. 본 연구에서는 대기와 지반의 경계층을 해석하는데 필요한 지표면 n-factor와 대류 열전달계수의 적용성을 분석하고자 실내실험을 수행 하였다. 실내실험 결과를 토대로 상용 수치해석 프로그램인 TEMP/W를 이용하여 각각의 경계층 조건에 따른 지중온도 변화를 해석하고 실내실험을 통해 측정된 온도 데이터와 비교하였다. 결론적으로 n-factor보다 지표면 대류 열전달계수를 적용한 수치 해석 모델이 실내실험 결과와 유사하였다.

• 지질공학
• /
• 제32권1호
• /
• pp.143-155
• /
• 2022

본 연구에서는 지진 모사실험을 진행하는 1 g 진동대 실험에 올라가는 연성토조(Laminar Shear Box, LSB)라고 하는 토조의 경계조건(Boundary effect)을 달리하여 다른 조건에 따른 응답가속도 증폭에 대한 분석하였다. LSB의 양 옆을 고정하여 경계조건을 달리하여 실험을 진행하였고, 가속도계를 각 동일한 위치에 설치하여 2가지 시료에 대하여 실험을 진행하였다. 또한, DEEPSOIL v7 프로그램을 이용하여 1차원 지반응답해석을 통하여 자유장 조건에서와 비교 분석하였다. 그 결과 가속도가 하층부에서 상층부로 올라갈수록 증폭하는 모습을 확인할 수 있었고, 지반응답해석과 비교한 결과, 자유장 조건에서 해석과 비슷하게 나오는 것을 확인할 수 있었다. SA분석결과, 지반응답해석과 유사한 결과를 얻을 수 있었으며, 고정한 경우는 PSA가 더욱 증폭하는 결과를 확인할 수 있었다.

• 한국작물학회:학술대회논문집
• /
• 한국작물학회 2017년도 9th Asian Crop Science Association conference
• /
• pp.315-315
• /
• 2017

In Japan, more than 80 % of soybean growing area is converted fields and excess water is one of the major problems in soybean production. For example, recent study (Yoshifuji et al., 2016) suggested that in the fields of shallow groundwater level (GWL) (< 1m depth), rising GWL even in a short period (e.g. 1 day) causes inhibition of soybean growth. Thus it becomes more and more important to predict GWL and soil moisture in detail. In addition to conventional surface drainage and underdrain, FOEAS (Farm Oriented Enhancing Aquatic System), which is expected to control GWL in fields adequately, has been developed recently. In this study we attempted to predict GWL and soil moisture condition at the converted field with FOEAS in Biwa lake reclamation area, Shiga prefecture, near the center of the main island of Japan. Two dimensional HYDRUS model (Simuinek et al., 1999) based on common Richards' equation, was used for the calculation of soil water movement. The calculation domain was considered to be 10 and 5 meter in horizontal and vertical direction, respectively, with two layers, i.e. 20cm-thick of plowed layer and underlying subsoil layer. The center of main underdrain (10 cm in diameter) was assumed to be 5 meter from the both ends of the domain and 10-60cm depth from the surface in accordance with the field experiment. The hydraulic parameters of the soil was estimated with the digital soil map in "Soil information web viewer" and Agricultural soil-profile physical properties database, Japan (SolphyJ) (Kato and Nishimura, 2016). Hourly rainfall depth and daily potential evapo-transpiration rate data were given as the upper boundary condition (B.C.). For the bottom B.C., constant upward flux, which meant the inflow flux to the field from outside, was given. Seepage face condition was employed for the surrounding of the underdrain. Initial condition was employed as GWL=60cm. Then we compared the simulated and observed results of volumetric water content at depth of 15cm and GWL. While the model described the variation of GWL well, it tended to overestimate the soil moisture through the growing period. Judging from the field condition, and observed data of soil moisture and GWL, consideration of soil structure (e.g. cracks and clods) in determination of soil hydraulic parameters at the plowed layer may improve the simulation results of soil moisture.