• Economic and Environmental Geology
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• 제27권3호
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• pp.295-311
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• 1994

A comprehensive in-situ tests are performed to define the hydrogeologic and hydrodispersive characteristics such as hydraulic conductivities, longitudinal dispersivity, and average linear velocities as well as conducting flow-net analysis at the study area. The results show that the study area is very heterogeneous so that hydraulic conductivities range from $6.45{\times}10^{-7}$ to $1.15{\times}10^{-5}m/s$ with average linear velocities of 0.34~0.62m/day. Whole groundwater in upper-most aquifer is discharging into the sea with specific discharge rate of $7.2{\times}10^{-3}$ to $1.3{\times}10^{-2}m/day$. The longitudinal dispersivity of the aquifer is estimated about 4.8m through In-situ injection phase test. The area is highly vulnerable to potential contaminant sources due to it's high value of DRASTIC index ranging from 139 to 155 and also under water table condition with very shallow groundwater level. To delineate contaminant plumes of toxic NaOH and carcinogenic benzene when these substances are assumed to be leaked through existing TSDF at the study area by unexpected accidents or spill, Aquifer Simulation Model (ASM) including Flow and Transport Model is used. Te simulated results reveal that the size of NaOH plume after 5 years continuous leak is about $250{\times}100m$ and benzene after 10 years, $490{\times}100m$. When the groundwater is abstracted about 50 days, which is maximum continuously sustained no-precipitation period during 30 years, with pumping rate of $100m^3/day$, THWELL program shows that the groundwater is adversly affected by sea water intrusion.

• Journal of Korean Society of Environmental Engineers
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• 제35권12호
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• pp.929-936
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• 2013

The saturator and injection nozzle are important facilities on the dissolved air flotation process. To increase the formation of micro bubble, it is required to improve the air dissolving performance in the saturator and keep the pressure uniform from the saturator to the nozzle. This study aimed to evaluate the performance of the saturator and the hydraulic effect of the nozzle and the pipe structure. The air volume concentration, bubble size and bubble residual time were measured in the test. The saturator, which had mounted with the spray nozzle, showed a good performance for bubble formation. Also, the characteristics of micro bubble formation were influenced by pressure uniformity and flow velocity through the orifice in the nozzle.

• Journal of Soil and Groundwater Environment
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• 제7권3호
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• pp.33-44
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• 2002

A field technique for assessing the transmissive fractures in an aquifer was applied to a fractured rock formation in Youngchun area Korea. Geological mapping and detailed acoustic borehole teleview(BHTV) logging were performed to obtain information about the fractures. The study area consists predominantly of two types of fractures. The fracture sets of low angle partings such as bedding and sheeting plains have strike N70-80$^{\circ}$W, 25$^{\circ}$-30$^{\circ}$SW and N3S$^{\circ}$W, 12$^{\circ}$NE, respectively. In areas of high fractures, on the other hand, the major fracture sets show strike N80$^{\circ}$W and dip 70$^{\circ}$-85$^{\circ}$SW, N10$^{\circ}$E.85$^{\circ}$SE in sedimentry rocks, N40-50$^{\circ}$E.85$^{\circ}$SE/85$^{\circ}$NE, N70$^{\circ}$E.80$^{\circ}$SE, and N7$^{\circ}$-75$^{\circ}$W.80$^{\circ}$SW in granites and volcanic rocks. Injection tests have been performed to identify discrete production zones and quantify the vertical distribution of hydraulic conductivity. The calculated hydraulic conductivities range from 3.363E-10 to 2.731E-6, showing that the difference between maximum and minimum value is four order of magnitude. Dominant section in hydraulic conductivity is extensively fractured. Geophysical logging was carried out to clarify characterization of the distribution of fracture zones. Transmissive fractures were evaluated through the comparison of the results obtained by each method. The temperature logs appeared to be a good indicator that can distinguish a high transmissive fractures from a common fractures in hydraulic conductivity. In numerous cases, evidence of fluid movement was amplified in the temperature gradient log. The fracture sets of N70-80$^{\circ}$W.60-85$^{\circ}$NE/SW N75-80$^{\circ}$W.25-30$^{\circ}$SW, N50-64$^{\circ}$W.60-85$^{\circ}$NE, N35-45$^{\circ}$E.65-75$^{\circ}$SE, and N65-72$^{\circ}$E.80$^{\circ}$SE/60$^{\circ}$NW were idenfied as a distinct transmissive fractures through the results of each tests.

• The Journal of Engineering Geology
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• 제33권3호
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• pp.371-388
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• 2023

A stratum with a complex composition and a distributed low-permeability soil layer is difficult to remediate quickly because the soil remediation does not proceed easily. For efficient purification, the permeability should be improved and the soil remediation agent (H₂O₂) should be injected into the contaminated section to make sufficient contact with the TPH (Total petroleum hydrocarbons). This study analyzed a method for crack formation and effective delivery of the soil remediation agent based on pneumatic fracturing, plasma blasting, and vacuum suction (the PPV method) and compared its improvement effect relative to chemical oxidation. A demonstration test confirmed the effective delivery of the soil remediation agent to a site contaminated with TPH. The injection amount and injection time were monitored to calculate the delivery characteristics and the range of influence, and electrical resistivity surveying qualitatively confirmed changes in the underground environment. Permeability tests also evaluated and compared the permeability changes for each method. The amount of soil remediation agent injected was increased by about 4.74 to 7.48 times in the experimental group (PPV method) compared with the control group (chemical oxidation); the PPV method allowed injection rates per unit time (L/min) about 5.00 to 7.54 times quicker than the control method. Electrical resistivity measurements assessed that in the PPV method, the diffusion of H₂O₂2 and other fluids to the surface soil layer reduced the low resistivity change ratio: the horizontal change ratio between the injection well and the extraction well decreased the resistivity by about 1.12 to 2.38 times. Quantitative evaluation of hydraulic conductivity at the end of the test found that the control group had 21.1% of the original hydraulic conductivity and the experimental group retained 81.3% of the initial value, close to the initial permeability coefficient. Calculated radii of influence based on the survey results showed that the results of the PPV method were improved by 220% on average compared with those of the control group.

• The Journal of Engineering Geology
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• 제29권4호
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• pp.483-494
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• 2019

This study aimed to determine the extent of artificial aquifer recharge and to evaluate appropriate recharge techniques based on field investigations and comparative analysis of each recharge method. Characteristics of the aquifer determine the target aquifer and the recharge method for artificial groundwater recharge. Electrical conductivity surveys, drilling, permeability tests, and grain-size analysis indicate that the hydraulic conductivity of weathered soil and weathered rock is higher than that of upper unconsolidated soil. Pumping tests indicate that the groundwater level was stable at a depth of 12 m until 9 hours of pumping, but after that it dropped again, indicating anisotropic aquifer characteristics. Three types of artificial recharge method were reviewed, including recharge wells, ditches, and ponds, and a combination of two methods is proposed: a recharge well system directly injecting into weathered soil and rock sections with good permeability, and an injection ditch that can increase the recharge effect by line-type injection in the upstream area. The extent of groundwater recharge by the selected methods will be evaluated through on-site tests and if their applicability is verified, they will contribute to securing water in areas of water shortage.

• The Journal of Engineering Geology
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• 제31권3호
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• pp.381-393
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• 2021

Physical, mechanical, hydraulic, and geophysical tests were applied to validate methods of inspecting the effectiveness of grouting on an agricultural reservoir dam. Data obtained from series of in situ and laboratory tests considered four stages: before grouting; during grouting; immediately after grouting; and after aging the grouting for 28 days. The results of SPT and triaxial tests, including the unit weight, compressive strength, friction angle, cohesion, and N-value, indicated the extent of ground improvement with respect to grout injection. However, they sometimes contained errors caused by ground heterogeneity. Hydraulic conductivity obtained from in situ variable head permeability testing is most suitable for identifying the effectiveness of grouting because the impermeability of the ground increased immediately after grouting. Electric resistivity surveying is useful for finding a saturated zone and a seepage pathway, and multichannel analysis of surface waves (MASW) is suitable for analyzing the effectiveness of grouting, as elastic velocity increases distinctly after grouting injection. MASW also allows calculation from the P- and S- wave velocities of dynamic properties (e.g., dynamic elastic modulus and dynamic Poisson's ratio), which can be used in the seismic design of dam structures.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제26권11호
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• pp.2228-2236
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• 2002

The axial piston pump by which the mechanical energy is converted into hydraulic energy has been widely used in a press, a injection molding machine and construction equipments due to the high specific power compared to the electric power system. In this paper, the one-piece shoe holder spring of the axial piston pump to simplify its structure and reduce this manufacturing cost was designed and tested. The finite element analyses using the 3-D shell element and contact element were performed to determine the thickness, width and initial angle of the shoe holder spring. Also, the compressive tests of the shoe holder spring were performed and their results were compared with those of the finite element analysis. Also, the performance and endurance limit of axial piston pump with the shoe holder spring were tested and evaluated.

• Geomechanics and Engineering
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• 제25권4호
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• pp.295-302
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• 2021

Cross-borehole electrical resistivity tomography (ERT) is an effective groundwater detection tool in geophysical investigations. In this paper, an artificial water injection test was conducted on a small clay sample, where the high-resolution cross-borehole ERT was used to investigate the moisture migration law over time. The moisture migration path can be two-dimensionally imaged based on the relationship between resistivity and saturation. The hydraulic conductivity was estimated, and the magnitude ranged from 10^-11 m/s to 10^-9 m/s according to the comparison between the simulation flow and the saturation distribution inferred from ERT. The results indicate that cross-borehole ERT could help determine the resistivity distribution of small size clay samples. Finally, the cross-borehole ERT technique has been applied to investigate the self-sealing characteristics of clay.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1448-1459
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• 2023

A key element of the safety analysis is Loss of Coolant Analysis (LOCA) which must be performed using system thermal-hydraulic codes. These codes are extensively validated against separate effect and integral experiments. RELAP/SCDAPSIM is one such code that may be used to predict LBLOCA response in a CANDU reactor. The RD-14M experiment selected for the Best Estimate Plus Uncertainty study is a 44 mm (22.7%) inlet header break test with no Emergency Coolant Injection. This work has two objectives first is to simulate pipe break with RELAP and compare these results to those available from experiment and from comparable TRACE calculations. The second objective is to quantify uncertainty in the fuel element sheath (FES) temperature arising from model coefficient as well as input parameter uncertainties using Integrated Uncertainty Analysis package. RELAP calculated results are found to be in good agreement with those of TRACE and with those of experiments. The base case maximum FES temperature is 335.5 ℃ while that of 95% confidence 95^th percentile is 407.41 ℃ for the first order Wilk's formula. The experimental measurements fall within the predicted band and the trends and sensitivities are similar to those reported for the TRACE code.

• Tunnel and Underground Space
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• 제28권6호
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• pp.670-691
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• 2018

This study presents the research results of the BMT(Benchmark Model Test) simulations of the DECOVALEX-2019 project Task B. Task B named 'Fault slip modelling' is aiming at developing a numerical method to predict fault reactivation and the coupled hydro-mechanical behavior of fault. BMT scenario simulations of Task B were conducted to improve each numerical model of participating group by demonstrating the feasibility of reproducing the fault behavior induced by water injection. The BMT simulations consist of seven different conditions depending on injection pressure, fault properties and the hydro-mechanical coupling relations. TOUGH-FLAC simulator was used to reproduce the coupled hydro-mechanical process of fault slip. A coupling module to update the changes in hydrological properties and geometric features of the numerical mesh in the present study. We made modifications to the numerical model developed in Task B Step 1 to consider the changes in compressibility, Permeability and geometric features with hydraulic aperture of fault due to mechanical deformation. The effects of the storativity and transmissivity of the fault on the hydro-mechanical behavior such as the pressure distribution, injection rate, displacement and stress of the fault were examined, and the results of the previous step 1 simulation were updated using the modified numerical model. The simulation results indicate that the developed model can provide a reasonable prediction of the hydro-mechanical behavior related to fault reactivation. The numerical model will be enhanced by continuing interaction and collaboration with other research teams of DECOVALEX-2019 Task B and validated using the field experiment data in a further study.