• Economic and Environmental Geology
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• v.28 no.5
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• pp.503-512
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• 1995

Groundwater flow in fracture networks is simulated using a discrete fracture (DF) model which assume that groundwater flows only through the fracture network. This assumption is available if the permeability of rock matrix is very low. It is almost impossible to describe fracture networks perfectly, so a stochastic approach is used. The stochastic approach assumes that the characteristic parameters in fracture network have special distribution patterns. The stochastic model generates fracture networks with some characteristic parameters. The finite element method is used to compute fracture flows. One-dimensional line element is the element type of the finite elements. The simulation results are shown by dominant flow paths in the fracture network. The dominant flow path can be found from the simulated groundwater flow field. The model developed in this study provides the tool to estimate the influences of characteristic parameters on groundwater flow in fracture networks. The influences of some characteristic parameters on the frcture flow are estimated by the Monte Carlo simulation based on 30 realizations.

• Tunnel and Underground Space
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• v.31 no.5
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• pp.309-332
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• 2021

Natural barrier systems surrounding the geological repository for the high-level radioactive waste should guarantee the hydraulic performance for preventing or delaying the leakage of radionuclide. In the case of the behavior of a crystalline rock, the hydraulic performance tends to be decided by the existence of discontinuities, so the coupled hydro-mechanical(HM) processes on the discontinuities should be characterized. The discontinuum modelling can describe the complicated behavior of discontinuities including creation, propagation, deformation and slip, so it is appropriate to model the behavior of a crystalline rock. This paper investigated the coupled HM processes in discontinuum modelling such as UDEC, 3DEC, PFC, DDA, FRACOD and TOUGH-UDEC. Block-based discontinuum methods tend to describe the HM processes based on the fluid flow through the discontinuities, and some methods are combined with another numerical tool specialized in hydraulic analysis. Particle-based discontinuum modelling describes the overall HM processes based on the fluid flow among the particles. The discontinuum methods that are currently available have limitations: exclusive simulations for two-dimension, low hydraulic simulation efficiency, fracture-dominated fluid flow and simplified hydraulic analysis, so it could be improper to the modelling the geological repository. Based on the concepts of various discontinuum modelling compiled in this paper, the advanced numerical tools for describing the accurate coupled HM processes of the deep geological repository should be developed.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.167-176
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• 2018

It is necessary to consider various geological parameters such as lithology, geological structure, earthquake, hydraulic geology, geochemistry, geological engineering, and geothermal in order to select potential sites for HLW(high-level radioactive waste) geological disposal. In particular, the geological lineament reflects the characteristics of various geological parameters and can be used as an important criterion for site selecting such as nuclear power plants and HLW repositories. In this paper, the Finnish lineament classification method for HLW disposal site selection through the lineament analysis was applied to the lineament data in the Korean peninsula. For this purpose, we used previous lineament data from the KIGAM(Korea Institute of Geoscience and Mineral Resources) and obtained new lineament data from the field geologists such as structural geologist, paleoseismologist, and geomorphologist. To ensure the reliability of the new lineament analysis data, we used high-resolution satellite images and hill-shade relief maps which were constructed by a digital elevation model. In the prevailing direction analysis from the acquired lineament data, the NNE-SSW direction was the most dominant, but the ENE-WSW and NNW-SSE directions also showed highly frequency depending on the experts. Applying the Finnish classification method, the geometrical development characteristics of the lineament corresponding to the Class 1 and 2 used for the wide-wide candidate site were compared. As a result of direction analysis for Class 1, the NNE-SSW direction was the most dominant and the WNW-ESE direction also showed a high frequency. In the case of Class 2, the NNE-SSW is the most prevalent and WNW-ESE or ENE-WSW direction also had highly frequency depending on the experts. Different lineament analysis results based on the same data are interpreted as a result of subjective experience and analytical criteria from the every experts. Therefore, it is necessary to establish integrated criteria and consider geophysical data for the publication of reliable nation-wide lineament map.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.782-789
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• 2010

Landslides cause enormous economic losses and casualties. Korea has mountainous regions and heavy slopes in most parts of the land and has consistently built new roads and large-scale housing complexes according to its industrial and urban growth. As a result, the damage from landslides becomes greater every year. In this study, performed a GIS-based landslide hazard analysis by SINMAP(Stability Index MAPping) model in Gyeonggi Icheon area coupling with geomorphological and geological data. SINMAP model has its theoretical basis in the infinite plane slope stability model with wetness obtained from a topographically based steady state model of hydrology. To Gyeonggi Icheon area landslides hazards evaluated, these SINMAP model were analysed results while simultaneously referring to the stability index map, where lines distinguish the zones categorized into the different stability classes and a table giving summary statistics.

• Economic and Environmental Geology
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• v.40 no.6
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• pp.739-749
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• 2007

The seismic velocity at the formation varies widely with physical properties in the layers. These features on seismic shot gathers are not capable of reproducing normally by numerical modeling of homogeneous medium, so that we need that of random inhomogeneous medium instead. In this study, we conducted Gaussian autocorrelation function (ACF), exponential autocorrelation function and von Karman autocorrelation function for getting inhomogeneous velocity model and applied a simple geological model. According to the results, von Karman autocorrelation function showed short wavelength to the inhomogeneous velocity medium. For numerical modeling for a gas hydrate, we determined a geological model based on field data set gathered in the East sea. The numerical modeling results showed that the von Karman autocorrelation function could properly describe scattering phenomena in the gas hydrate velocity model which contains an inhomogeneous layer. Besides, bottom-simulating-reflectors and scattered waves which appear at seismic shot gather of the field data showed properly in the inhomogeneous numerical modeling.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.spc
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• pp.75-87
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• 2020

The Korea Atomic Energy Research Institute (KAERI) has developed geological repository systems for the disposal of high-level wastes and spent nuclear fuels (SNFs) in South Korea. The purpose of the most recently developed system, the improved KAERI Reference Disposal System Plus (KRS⁺), is to dispose of all SNFs in Korea with improved disposal area efficiency. In this paper, a system-level safety assessment model for the KRS⁺ is presented with long-term assessment results. A system-level model is used to evaluate the overall performance of the disposal system rather than simulating a single component. Because a repository site in Korea has yet to be selected, a conceptual model is used to describe the proposed disposal system. Some uncertain parameters are incorporated into the model for the future site selection process. These parameters include options for a fractured pathway in a geosphere, parameters for radionuclide migration, and repository design dimensions. Two types of SNF, PULS7 from a pressurized water reactor and Canada Deuterium Uranium from a heavy water reactor, were selected as a reference inventory considering the future cumulative stock of SNFs in Korea. The highest peak radiological dose to a representative public was estimated to be 8.19×10^-4 mSv·yr^-1, primarily from ¹²⁹I. The proposed KRS⁺ design is expected to have a high safety margin that is on the order of two times lower than the dose limit criterion of 0.1 mSv·yr^-1.

• Journal of Korea Water Resources Association
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• v.38 no.9 s.158
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• pp.699-711
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• 2005

In this study, the U.S. Geological Survey's DR3M-II(Distributed Routing Rainfall-Runoff Model) was applied for small urban drainage. DR3M-II is a watershed model for routing storm runoff through a branched system of pipes and natural channels using rainfall input. The model was calibrated and verified using short term rainfall-runoff data collected from Sanbon basin. Also, the parameters were optimized using Rosenbrock technic. An estimated simulation error for peak discharge was about 7.4 percent and the result was quite acceptable. Results of the sensitivity analysis indicate that the percent of effective impervious area and ${\alpha}$ defining surface slope and roughness were the most sensitive variables affecting runoff volumes and peak discharge for low and high intensity storm respectively. In most cases, soil moisture accounting and infiltration parameters are the variables that give more effects to runoff volumes than peak discharge. Parameter ${\alpha}$ showed the opposite result.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.267-272
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• 2007

Uiseong subbasin belonging to Kyungsang basin resulted from volcanic activity in the late Cretaceous. In this study, we carry out MT and gravity survey at the Hwasan caldera, which was formed of volcanic and abyssal rocks complex, then analyze and identify geological substructure. Potential survey such as gravity and magnetic survey has been mainly carried out in former studies, so depth information for understanding substructure was not enough. To complement a potential survey, we use MT method, which has high vertical resolution. Moreover we make a simple 2D model comparing with former study. The result of MT and gravity 2D modeling shows that this area is roughly composed of 3 layers; The bottom layer is a basement. In the second layer, intrusive rocks having high resistivity is placed along the ring faults and the sedimentary layer of low resistivity is inside caldera. The highest layer is alluvium. To comprehend the 3D structure of the Hwasan caldera, we perform 3D gravity inversion, and construct the 3D model from the result of 3D gravity inversion. MT responses are calculated by using the constructed 3D model and the 3D model of the Hwasan caldera's structure is suggested after comparing the calculated values with the observed values at MT line.

• Computers and Concrete
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• v.31 no.2
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• pp.85-95
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• 2023

Natural pozzolans are used as additives in cement to develop more durable and high-performance concrete. Pozzolanic activity index (PAI) is important for assessing the performance of a pozzolan as a binding material and has an important effect on the compressive strength, permeability, and chemical durability of concrete mixtures. However, the determining of the 28 days (short term) and 90 days (long term) PAI of concrete mixtures is a time-consuming process. In this study, to reduce extensive experimental work, it is aimed to predict the short term and long term PAIs as a function of the chemical compositions of various natural pozzolans. For this purpose, the chemical compositions of various natural pozzolans from Central Anatolia were determined with X-ray fluorescence spectroscopy. The mortar samples were prepared with the natural pozzolans and then, the short term and the long term PAIs were calculated based on compressive strength method. The effect of the natural pozzolans' chemical compositions on the short term and the long term PAIs were evaluated and the PAIs were predicted by using multiple linear regression (MLR) and adaptive neuro-fuzzy inference system (ANFIS) model. The prediction model results show that both reactive SiO₂ and SiO₂+Al₂O₃+Fe₂O₃ contents are the most effective parameters on PAI. According to the performance of prediction models determined with metrics such as root mean squared error (RMSE) and coefficient of correlation (R²), ANFIS models are more feasible than the multiple regression model in predicting the 28 days and 90 days pozzolanic activity. Estimation of PAIs based on the chemical component of natural pozzolana with high-performance prediction models is going to make an important contribution to material engineering applications in terms of selection of favorable natural pozzolana and saving time from tedious test processes.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.785-790
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• 2010

Geothermal energy is gaining wide attention as a highly efficient renewable energy and being increasingly used for heating/cooling systems of buildings. The standing column well (SCW) is especially efficient, cost-effective, and suitable for Korean geological and hydrological conditions. However, a numerical model that simulates the SCW has not yet been developed and applied in Korea. This paper describes the development of the SCW numerical model using a finite-volume analysis program. The model performs the hydro-thermal coupled analyses and simulates heat transfer through advection, convection, and conduction. The accuracy of the model was verified through comparisons with field data measured at SCWs in Korea. Comparisons indicated that the SCW numerical model can closely predict the performance of a SCW.