• Journal of the Korean GEO-environmental Society
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• v.10 no.2
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• pp.61-68
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• 2009

This paper presents the numerical investigation for the hydraulic behavior of a fractured rock mass with a hydromechanical interaction which may be considered during the in-situ hydraulic injection test. These experiments consist in a series of flow meter injection tests for fractures existing along an open hole section installed in a borehole, and experimental results are applied for testing a numerical model developed to the analysis and prediction of such hydromechanical interactions. Field experimental results show that conductive fractures form a dynamic and interdependent network, that individual fractures cannot be adequately modeled as independent systems, that new fluid intaking zones generate when pore pressure exceeds the minimum principal stress magnitude in that borehole, and that pore pressures much larger than this minimum stress can be further supported by the circulated fractures. In this study, these characteristics are investigated numerically how to influence the morphology of the natural fracture network in a rock mass by using a discrete fracture ntework model.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1890-1901
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• 2022

We have assessed the applicability of the thermal-hydraulic system analysis code, SPACE, to a small modular reactor called SMART. For the assessment, the experimental data from a scale-down integral-test facility, SMART-ITL, were used. It was conformed that the SPACE code unrealistically calculates the safety injection flow rate through the CMT and SIT during a small-break loss-of-coolant experiment. This unrealistic behavior was due to the overprediction of interfacial heat transfer at the steam-water interface in a vertically stratified flow in the tanks. In this study, a special thermal-hydraulic component model has been developed to realistically calculate the interfacial heat transfer when a strong non-equilibrium two-phase flow is formed in the CMT or SIT. Additionally, we developed a special heat structure model, which analytically calculates the heat transfer from the hot steam to the cold tank wall. The combination of two models for the tank are called the special component model. We assessed it using the SMART-ITL passive safety injection system (PSIS) test data. The results showed that the special component model well predicts the transient behaviors of the CMT and SIT.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.231-234
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• 2001

When constructing subsurface structures and/or wells, the precise estimates of hydraulic parameters must be obtained for operating safety and/or for developing necessary quantity of groundwater. Hydraulic conductivity is mainly subjected to the characteristics of fracture network in the fractured media such as fracture orientation and angle, fracture aperture and frequency, fracture length, interconnectivity of fractures, and filling material, feature of fracture plane. In this study we conducted water injection test at afferent depths on six boreholes drilled in granite of Mt. Geumjeong. hydraulic conductivity was calculated using Moye and Hvorslev methods. The relation between hydraulic conductivity and fracture frequency data obtained from acoustic televiewer and core log were analyzed. The result shows that the correlation between the hydraulic conductivity and the fracture frequency data obtained from acoustic televiewer is better than that with the core log.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.725-732
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• 2003

It was achieved that Rowecell test for this undisturbed sample was picked by Block sampler($\phi$:250mm, L:500mm) and hydraulic piston sampler($\phi$:76mm, L:850mm) in the marine clay of YONGYUDO and YEONGJONGDO in this research. Ratio of coefficient of consolidation was analyzed through comparison with C$\_$h/ by CPTu and C$\_$v/ and C$\_$h/ by existent consolidation test. According to analysis, coefficient of consolidation of block sample is fairly greater than coefficient of consolidation of piston sample. And the bigger diameter of undisturbed sample, sample disturbance could know decreasing. Coefficient of consolidation by Rowecell test measured more greatly than coefficient of consolidation by existent consolidation test. Rowecell test could know decreasing consolidation rate because of smear effect by Mandrel injection. Also, C$\_$h/ by CPTu shows deviation by each analysis method, selection of suitable analysis method judged by important leading in the coefficient of consolidation.

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.279-294
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• 2001

When constructing subsurface structures and drilling wells, the precise hydraulic parameters must be obtained for operating safety and for developing enough quantity of groundwater, respectively. In this study we conducted water injection test at different depths on six boreholes drilled in the granite of Mt. Geumjeong. Hydraulic conductivity was calculated using Moye and Hvorslev methods. The relation between hydraulic conductivity and fracture frequency data obtained from acoustic televiewer and core log was analyzed. From the result, though the correlation coefficient between the hydraulic conductivity and the fracture frequency from acoustic televiewer data is higher than that between the hydraulic conductivity and the fracture frequency from core log data on most of the test holes, the correlation coefficient between the hydraulic conductivity and the fracture frequency from the televiewer data is lower than 0.5. This suggests that the hydraulic conductivity of granite in the study area is influenced not only by the fracture frequency but also by various factors of fracture network such as fracture aperture and length, interconnectivity of fractures, fracture orientation and angle, filling material and so on.

• Tunnel and Underground Space
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• v.27 no.5
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• pp.263-270
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• 2017

Hydraulic rock splitting is a technique which leads to failure of rockmass by means of water injection with a pressure higher than the tensile strength of rockmass, using straddle packer installed in boreholes drilled from free surface. Field tests were conducted in this study for several slopes of biotite granite according to various designs for borehole layout and water injection. Test results showed that new cracks were generated to connect to adjacent holes or that pre-existed cracks were propagated by injection, finally leading to failure. In particular, this study suggests the possibility of controlling the direction of generated cracks with guide slot, since new cracks were generated parallel to the guide slots carved on a borehole wall before injection. Various types of borehole layout and injection methods should be further developed for the practical uses, considering the factors influencing on crack generation.

• Nuclear Engineering and Technology
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• v.49 no.7
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• pp.1537-1546
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• 2017

Many thermal-hydraulic tests have been conducted at the Korea Atomic Energy Research Institute for verification of the SMART (System-integrated Modular Advanced ReacTor) design, the standard design approval of which was issued by the Korean regulatory body. In this paper, the contributions of these tests to the standard design approval of SMART are discussed. First, an integral effect test facility named VISTA-ITL (Experimental Verification by Integral Simulation of Transients and Accidents-Integral Test Loop) has been utilized to assess the TASS/SMR-S (Transient and Set-point Simulation/Small and Medium) safety analysis code and confirm its conservatism, to support standard design approval, and to construct a database for the SMART design optimization. In addition, many separate effect tests have been performed. The reactor internal flow test has been conducted using the SCOP (SMART COre flow distribution and Pressure drop test) facility to evaluate the reactor internal flow and pressure distributions. An ECC (Emergency Core Coolant) performance test has been carried out using the SWAT (SMART ECC Water Asymmetric Two-phase choking test) facility to evaluate the safety injection performance and to validate the thermal-hydraulic model used in the safety analysis code. The Freon CHF (Critical Heat Flux) test has been performed using the FTHEL (Freon Thermal Hydraulic Experimental Loop) facility to construct a database from the $5{\times}5$ rod bundle Freon CHF tests and to evaluate the DNBR (Departure from Nucleate Boiling Ratio) model in the safety analysis and core design codes. These test results were used for standard design approval of SMART to verify its design bases, design tools, and analysis methodology.

• Journal of Korea Water Resources Association
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• v.54 no.11
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• pp.863-873
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• 2021

The mechanical dispersion which dominates solute transport in porous media is caused by the difference in flow velocity within pores. Longitudinal dispersion coefficient and longitudinal dispersivity that are hydro-dispersive parameters of advection-dispersion equation can only be obtained by experiment. Hydraulic mean radius that represents the amount and intensity of flowing water within pores can be obtained by the formula using the factors for physical properties. A slug injection test was conducted and a power type empirical formula for obtaining a longitudinal dispersivity using a hydraulic mean radius in rockfill porous media was derived. It is possible to obtain the longitudinal dispersivity depending on transport distance because it contains a formula for a scale constant, and expected to be applicable to waterways filled with homogeneous gravel and small flow rate.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.149-165
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• 1993

Nowadays, the field hydraulic test is still an only method to evaluate groundwater characteristics in subsurface. The results of hydraulic test are very important for the concept model of fracture hydrogeology as well as the geometric pattern of fractures. The hydraulic tests performed in Korea are generally analysed under such assumption as steady radial flow in homogeneous aquifer or along simple geometry of fractures. Also the transmissivity measured in a fixed interval length is equivalent to a sum of individual fracture transmissivities in test legth. The boundary effects of weH hydraulics and the geometry of flow paths are hardly obtained from the test results analysed by a steady flow method. To circumvent this problem, the flow dimensional analysis was attempted from the results of constant pressure injection test carried out in a fractured granite area. A comparison of the hydraulic conductivity values from the transient and steady analysis shows that the latter is about a factor of 2~3 higher than the former. However, it was possible to analyse a flow dimension of each test interval from flow rate variation with time. The upper part of the bedrock(<10m deep) indicates an open boundary and the flow dimension shows nearly steady states, while the lower part of the bedrock(>25m deep) is characterized as sublinear flow dimension with a dosed boundary. In one of the test sections(15m deep), the flow dimension was changed from linear flow to spherical flow. From the experience of this study, one of the immediate problems to be solved is to enhance the field testing equipments, i.e., an accurate flowmeter with autorecording and a pressure detecting device to be able to install in the test section.

• Journal of Soil and Groundwater Environment
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• v.25 no.1
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• pp.12-24
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• 2020

This study was conducted to examine an artificial recharge system, which was considered to be an alternative for securing additional groundwater resources in a high-density greenhouse region. An injection well with a depth of 14.0 m was placed in an alluvial plain of the zone. Eight monitoring wells were placed in a shape of dual circles around the injection well. Aquifer tests showed that the aquifer was comprised with high-permeable layer with hydraulic conductivities of 1.5×10^-3~2.4×10^-2 cm/sec and storage coefficients of 0.07~0.10. A step injection test resulted in a specific groundwater-level rising (Sr/Q) values of 0.013~0.018 day/㎡ with 64~92% injection efficiencies. Results of the constant-rate injection test with an optimal injection rate of 100 ㎥/day demonstrated an enormous storage capacity of the alluvial aquifer during ten experimental days. To design an optimal recharge system for an artificial recharge, the high-permeable layer should be isolated by dual packers and suitable pressure should be applied to the injection well in order to store water. An anisotropy ratio of the alluvial aquifer was evaluated to be approximately 1.25 : 1 with an anisotropy angle of 71 degrees, indicating intervals among injection wells are almost the same.