• Geophysics and Geophysical Exploration
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• v.22 no.3
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• pp.160-167
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• 2019

Resistivity inversion result may be distorted if the seepage line fluctuation within central core with the change of reservoir water level as well as the conductivity of the reservoir water is not taken into consideration because the reservoir dike is composed of three-dimensional (3D) resistivity structure. Consequently, to accurately analyze the resistivity changes inside the reservoir dike according to the change of reservoir water level, 3D electrical resistivity modeling for the 2D survey line considering topography and physical properties of dam components was carried out. In addition, 2D inversion was performed with the simulated 2D resistivity data for a given 3D model in order to compare it with the inversion result of real field data. For 283 reservoirs in Korea, 2D inversion results for the simulated 2D data and field 2D resistivity data were compared. Finally, the reservoirs with an inversion ratio of 50% or less were selected as reservoirs that require further precise investigation.

• Journal of the Korean Geotechnical Society
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• v.24 no.3
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• pp.25-34
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• 2008

A finite element analysis was performed for new earth retention system with prestressed wales. A 3D finite element model was adopted in this study to investigate the behavior of the earth retention system with prestressed wales. A procedure of the 3D finite element modeling of this earth retention system was presented. The procedure included the modeling of soil, wall, strut, and members of prestressed wale system which consists of wale, support leg, and steel wires, and the interface modeling of soil-wall and wall-wale. The numerical predictions of lateral wall deflection, and axial load on the members of prestressed wale systems and struts were evaluated in comparison with the measurements obtained from field instruments. A sensitivity analysis was performed using the proposed 3D finite element model to investigate the behavior of new earth retention system on a wide range of prestress load conditions of steel wires. The lateral deflection of the wall and wale, the bending moment of the wale, and the lateral earth pressure distribution on the wall were computed. Implications of the results from this study were discussed.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.51-51
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• 2021

환경생태유량은 수생태 건강성 유지를 위한 최소한의 유량으로 K-water에서는 유량증분방법론 기반의 1차원 물리적 서식처 모형인 PHABSIM(Physical habitat simulation system)을 이용해 고시지점에 대해 환경생태유량을 산정하여 제시하고 있으나, PHABSIM을 이용하여 환경생태유량을 산정하기 위해서는 지형, 수문 및 어류조사와 같은 현장조사를 지속적으로 실시해야한다는 한계점이 존재한다. 따라서 본 연구에서는 안동댐 하류유역(4,565.7 km²)을 대상으로 SWAT(Soil and water assessment tool)과 PHABSIM을 연계하여 수문모형을 이용한 유량 모의에 따른 대상 어종의 환경생태유량을 산정하고자 한다. SWAT 구축을 위해 DEM과 토양도 및 토지이용자료와 유역 내 위치한 7개의 기상관측소에 대한 40년(1980~2019)의 기상자료를 수집하여 적용하였으며, SWAT의 검보정을 위해 유역내 위치한 2개의 다목적 댐(안동댐, 임하댐)의 실측 운영자료와 1개의 수위관측소의 유량자료를 수집하였다. PHABSIM의 경우, 안동댐 하류유역에 대한 하천정비기본계획 보고서에 기반하여 지형자료를 입력하였으며 문헌조사를 통해 대상어종의 서식적합도지수를 수집하여 적용하였다. 3개 지점에 대한 SWAT 검보정결과, 평균 R², NSE 및 RMSE는 각각 0.51~0.76, 0.47~0.74, 0.61~1.84 mm/day로 나타났다. PHABSIM과의 연계를 위해 검보정된 SWAT의 하천유량에 대해 유황분석을 실시하였고, 산정한 Q10과 Q355를 유량의 최대·최소 범위로 설정하여 PHABSIM의 유량 경계조건으로 활용하였다. 이를 이용하여 SWAT과 PHABSIM의 연계모델링 적용성을 평가하고 대상어종의 환경생태유량을 산정할 예정이다.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.05a
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• pp.35-81
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• 1998

Distinct Element Method(DEM) has a great advantage to model the discontinuous behaviour of jointed rock masses such as rotation, sliding, and separation of rock blocks. Geometrical data of joints by a field monitoring is not enough to model the jointed rock mass though the results of DE analysis for the jointed rock mass is most sensitive to the distributional properties of joints. Also, it is important to use a properly joint law in evaluating the stability of a jointed rock mass because the joint is considered as the contact between blocks in DEM. In this study, a stochastic modelling technique is developed and the dilatant rock joint is numerically modelled in order to consider th geometrical and mechanical properties of joints in DE analysis. The stochastic modelling technique provides a assemblage of rock blocks by reproducing the joint distribution from insufficient joint data. Numerical Modelling of joint dilatancy in a edge-edge contact of DEM enable to consider not only mechanical properties but also various boundary conditions of joint. Preprocess Procedure for a stochastic DE model is composed of a statistical process of raw data of joints, a joint generation, and a block boundary generation. This stochastic DE model is used to analyze the effect of deviations of geometrical joint parameters on .the behaviour of jointed rock masses. This modelling method may be one tool for the consistency of DE analysis because it keeps the objectivity of the numerical model. In the joint constitutive law with a dilatancy, the normal and shear behaviour of a joint are fully coupled due to dilatation. It is easy to quantify the input Parameters used in the joint law from laboratory tests. The boundary effect on the behaviour of a joint is verified from shear tests under CNL and CNS using the numerical model of a single joint. The numerical model developed is applied to jointed rock masses to evaluate the effect of joint dilation on tunnel stability.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.101-111
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• 2006

In case of drilled shafts installed by drilling through soft overburden onto a strong rock, the piles can be regarded as end-bearing elements and their working load is determined by the safe working stress on the pile shaft at the point of minimum cross-section or by code of practice requirements. Drilled shafts drilled down for some depth into weak or weathered rocks and terminated within these rocks act partly as friction and partly as end-bearing piles. The base resistance component can contribute significantly to the ultimate capacity of the pile. However, the shaft resistance is typically mobilized at considerably smaller pile movements than that of the base. In addition, the base response can be adversely affected by any debris that is left in the bottom of the socket. The reliability of base response therefore depends on the use of a construction and inspection technique which leaves the socket free of debris. This may be difficult and costly to achieve, particularly in deep sockets, which are often drilled under water or drilling slurry. As a consequence of these factors, shaft resistance generally dominates pile performance at working loads. The efforts to improve the prediction of drilled shaft pile performance are therefore primarily concerned with the complex mechanisms of shaft resistance development. In this study, the numerical analyses are carried out to investigate the behavior characteristics of side of rock socketed drilled shafts varying the loading condition at the pile head. The difference of behavior characteristics of side resistance is also evaluated with the effects of modelling of asperity.

• Geophysics and Geophysical Exploration
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• v.11 no.3
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• pp.221-229
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• 2008

The three dimensional model method is widely applied in resource development for feasibility study, mine design, excavation planning and process management by constructing the database of various data in 3 dimensional space. Most of geophysical surveys for the purpose of engineering and resource development are performed in 2 dimensional line survey due to the restriction of the field situation, technical or economical situation and so on. The acquired geophysical data are used as the input for the 2 dimensional inversion under the 2 dimensional assumption. But the geophysical data are affected by 3 dimensional space. Therefore in order to reduce the error caused by 2 dimensional assumption, the 2 dimensional inversion result must be interpreted considering the additional information such as 3 dimensional topography, geological structure, borehole survey etc. The applicability and usability of 3 dimensional modeling method are studied by reviewing the case study to the geophysical data acquired in field of engineering and resource development.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.171-171
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• 2017

전산유체역학(CFD: Computational Fluid Dynamics)를 이용한 스마트팜 환경 내부의 정밀 제어 연구가 진행 중이다. 시계열 데이터의 난해한 동적 해석을 극복하기위해, 비선형 모델링 기법의 일종인 인공신경망을 이용하는 방안을 고려하였다. 선행 연구를 통하여 환경 데이터의 비선형 모델링을 위한 Tensorflow활용 방법이 하드웨어 가속 기능을 바탕으로 월등한 성능을 보임을 확인하였다. 그럼에도 오프라인 일괄(Offline batch)처리 방식의 한계가 있는 인공신경망 모델링 기법과 현장 보급이 불가능한 고성능 하드웨어 연산 장치에 대한 대안 마련이 필요하다고 판단되었다. CFD 해석을 위한 Solver로 SU2(http://su2.stanford.edu)를 이용하였다. 운영 체제 및 컴파일러는 1) Mac OS X Sierra 10.12.2 Apple LLVM version 8.0.0 (clang-800.0.38), 2) Windows 10 x64: Intel C++ Compiler version 16.0, update 2, 3) Linux (Ubuntu 16.04 x64): g++ 5.4.0, 4) Clustered Linux (Ubuntu 16.04 x32): MPICC 3.3.a2를 선정하였다. 4번째 개발환경인 병렬 시스템의 경우 하드웨어 가속는 OpenCL(https://www.khronos.org/opencl/) 엔진을 이용하고 저전력 ARM 프로세서의 일종인 옥타코어 Samsung Exynos5422 칩을 장착한 ODROID-XU4(Hardkernel, AnYang, Korea) SBC(Single Board Computer)를 32식 병렬 구성하였다. 분산 컴퓨팅을 위한 환경은 Gbit 로컬 네트워크 기반 NFS(Network File System)과 MPICH(http://www.mpich.org/)로 구성하였다. 공간 분해능을 계측 주기보다 작게 분할할 경우 발생하는 미지의 바운더리 정보를 정의하기 위하여 3차원 Kriging Spatial Interpolation Method를 실험적으로 적용하였다. 한편 병렬 시스템 구성이 불가능한 1,2,3번 환경의 경우 내부적으로 이미 존재하는 멀티코어를 활용하고자 OpenMP(http://www.openmp.org/) 라이브러리를 활용하였다. 64비트 병렬 8코어로 동작하는 1,2,3번 운영환경의 경우 32비트 병렬 128코어로 동작하는 환경에 비하여 근소하게 2배 내외로 연산 속도가 빨랐다. 실시간 CFD 수행을 위한 분산 컴퓨팅 기술이 프로세서의 속도 및 운영체제의 정보 분배 능력에 따라 결정된다고 판단할 수 있었다. 이를 검증하기 위하여 4번 개발환경에서 운영체제를 64비트로 개선하여 5번째 환경을 구성하여 검증하였다. 상반되는 결과로 64비트 72코어로 동작하는 분산 컴퓨팅 환경에서 단일 프로세서 기반 멀티 코어(1,2,3번) 환경보다 보다 2.5배 내외 연산속도 향상이 있었다. ARM 프로세서용 64비트 운영체제의 완성도가 낮은 시점에서 추후 성공적인 실시간 CFD 모델링을 위한 지속적인 검토가 필요하다.

• The Journal of Engineering Geology
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• v.28 no.1
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• pp.81-99
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• 2018

Excessive groundwater discharge by tunneling and tunnel operation can lead to groundwater exhaustion and ground subsidence. Therefore, it is very important to evaluate environmental impact and to establish mitigation measures of the impact related to tunnel excavation based on hydrogeological and modeling approaches. This study examined the depletion of surface reservoirs and valley water due to tunnel excavation through field survey, water quality analysis, tracer test, and groundwater modeling. As a result of field water quality test, the concentration of chemical constituents in groundwater discharge into the tunnel is slightly higher than that of valley water. By the result of laboratory water analysis, both valley water and the groundwater belong to $Ca^{2+}+HCO_3{^-}$ type. Tracer test that was conducted between the valley at the injection point and the tunnel, indicates valley water infiltration into the ground and flowing out to the tunnel, with maximum electrical conductance changes of $70{\mu}S/cm$ in the first test and of $40{\mu}S/cm$ in the second test. By groundwater modeling, the groundwater discharge rate into the tunnel during tunnel construction is estimated as $4,942m^3/day$ and groundwater level recovers in 3 years from the tunnel completion. As a result of particle tracking modeling, the nearest particle reaches the tunnel after 6 hours and the farthest particle reaches the tunnel after 9 hours, similarly to the case of the field trace test.

• Geotechnical Engineering
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• v.12 no.5
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• pp.79-88
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• 1996

In this study, prediction of soil behavior under vacuum preloading with vertical drain is explored on the basis of numerical models and toe results were compared with field measurements. Reasonable prediction of the time rate of settlements and pore pressure dissipation under vacuum preloading is the maj or concern. The conventional method for vatsuum preloading is based on modeling vacuum preloading as surcharge loading for the consolidation analysis. However, this modeling may violate the real behavior of soils under vacuum loading since the total stress in the analysis varies due to the modeled surcharge loading whereas in'.situ total stress of soils under vacuum loading is constant. In this study a new method is suggested. Instead of modeling vacuum loading as surcharge loading, negative hydraulic head is applied at the surface drain boundary to simulate the vacuum preloading. Comparisons of predictions and field measurements of soil behavior under vatsuum preloading are presented and the usefulness of the new modeling technique is demonstrated.

• Economic and Environmental Geology
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• v.35 no.1
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• pp.13-23
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• 2002

The chemical compositions of groundwaters from the granite areas mainly belong to Ca-HC0$_{3}$ and Na-HC0$_{3}$type, and some of these belong to Ca-(CI+S0$_{4}$) and Na-(CI+S0$_{4}$) type. Spring waters and groundwaters from anorthosite areas belong to Ca-HC03 and Na-HC03 type, respectively. The result of reaction path modeling shows that the chemical compositions of aqueous solution reacted with granite evolve from initial Ca-CI type, via CaHC0$_{3}$ type, to Na-HC0$_{3}$ type. The result of rain water-anorthosite interaction is similar to evolution path of granite reaction and both of these results agree well with the field data. In the reaction path modeling of rain watergranite/anorthosite reaction, as a reaction is progressing, the activity of hydrogen ion decreases (pH increases). The concentrations of cations are controlled by the dissolution of rock-forming minerals and precipitation and re-dissolution of secondary minerals according to the pH. The continuous addition of granite causes the formation of secondary minerals in the following sequence; gibbsite plus hematite, Mn-oxide, kaolinite, silica, chlorite, muscovite (a proxy for illite here), calcite, laumontite, prehnite, and finally analcime. In the anorthosite reaction, the order of precipitation of secondary minerals is the same as with granite reaction except that there is no silica precipitation and paragonite precipitates instead of analcime. The silica and kaolinite are predominant minerals in the granite and anorthosite reactions, respectively. Total quantities of secondary minerals in the anorthosite reaction are more abundant than those in the granite reaction.