• Journal of the Korean Association of Geographic Information Studies
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• v.25 no.4
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• pp.49-62
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• 2022

Borehole Data is geotechnical information provided so that workers can safely perform construction at the field. It creates 3D data and supports viewing as a 3D image. Currently, all Korean companies that develop programs using 3D visualization use the MVS program developed by C Tech Development Corporation. However, the MVS program is a commercial program, and it is difficult to use MVS in 3D related programs developed by Korean Companies. In this paper, we propose to develop a program that can replace MVS to generate a 3D stratum model from clustered borehole information using Python's Gempy open-source. The 3D stratum model program can creates point data for each stratum and can creates a surface for each stratum through interpolation. Then, the 3D stratum model program is completed by merging the surfaces of each stratum. It was confirmed that there was no difference when a 3D model was created and compared with the MVS program and the proposed program from the borehole data of a Goyang area.

• Journal of the Korean Geotechnical Society
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• v.22 no.7
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• pp.23-35
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• 2006

Shear load transfer characteristics of rock-socketed drilled shafts were analyzed. The constant normal stiffness (CNS) direct shear tests were performed to identify the major influencing factors of shaft resistance, i.e., unconfined compressive strength, borehole roughness, normal stiffness, initial confining stress, and material properties. Based on the CNS tests, shear load transfer function of drilled shafts in rocks is proposed using borehole roughness and the geological strength index (GSI), which indicates discontinuity and surface condition of rock mass in Hoek-Brown criterion (1997). The proposed load-transfer function was verified by the load test results of seven rock-socketed drilled test shafts subjected to axial loads. Through comparisons of the results of load tests, it is found that the load-transfer function by the present study is in good agreement with the general trend observed by in situ measurements, and thus represents a significant improvement in the prediction of load transfer of drilled shafts.

• Economic and Environmental Geology
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• v.49 no.6
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• pp.459-467
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• 2016

Due to the limited areal space for installation, borehole heat exchangers (BHEs) at depths deeper than 300 m are considered for geothermal heating and cooling in the urban area. The deep vertical closed-loop BHEs are unconventional due to the depth and the range of the typical installation depth is between 100 and 200 m in Korea. The BHE in the study consists of 50A (outer diameter 50 mm, SDR 11) PE U-tube pipe in a 150 mm diameter borehole with the depth of 300 m. In order to compensate the buoyancy caused by the low density of PE pipe ($0.94{\sim}0.96g/cm^3$) in the borehole filled with ground water, 10 weight band sets (4.6 kg/set) were attached to the bottom of U-tube. A thermal response test (TRT) and fundamental basic surveys on the thermophysical characteristics of the ground were conducted. Ground temperature measures around $15^{\circ}C$ from the surface to 100 m, and the geothermal gradient represents $1.9^{\circ}C/100m$ below 100 m. The TRT was conducted for 48 hours with 17.5 kW heat injection, 28.65 l/min at a circulation fluid flow rate indicates an average temperature difference $8.9^{\circ}C$ between inlet and outlet circulation fluid. The estimated thermophysical parameters are 3.0 W/mk of ground thermal conductivity and 0.104 mk/W of borehole thermal resistance. In the stepwise evaluation of TRT, the ground thermal conductivity was calculated at the standard deviation of 0.16 after the initial 13 hours. The sensitivity analysis on the borehole thermal resistance was also conducted with respect to the PE pipe diameter and the thermal conductivity of backfill material. The borehole thermal resistivity slightly decreased with the increase of the two parameters.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.4
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• pp.301-312
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• 2017

The concept of deep borehole disposal (DBD) for high-level nuclear wastes has been around for about 40 years. Now, the Department of Energy (DOE) in the United States (U.S.) is re-examining this concept through recent studies at Sandia National Laboratory and a field test. With DBD, nuclear waste will be emplaced in boreholes at depths of 3 to 5 km in crystalline basement rocks. Thinking is that these settings will provide nearly intact rock and fluid density stratification, which together should act as a robust geologic barrier, requiring only minimal performance from the engineered components. The Nuclear Waste Technical Review Board (NWTRB) has raised concerns that the deep subsurface is more complicated, leading to science, engineering, and safety issues. However, given time and resources, DBD will evolve substantially in the ability to drill deep holes and make measurements there. A leap forward in technology for drilling could lead to other exciting geological applications. Possible innovations might include deep robotic mining, deep energy production, or crustal sequestration of $CO_2$, and new ideas for nuclear waste disposal. Novel technologies could be explored by Korean geologists through simple proof-of-concept experiments and technology demonstrations.

• Geomechanics and Engineering
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• v.6 no.1
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• pp.79-98
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• 2014

This paper presents an experimental and numerical study on the evaluation of a thermal response test using a precast high-strength concrete (PHC) energy pile and a closed vertical system with W-type ground heat exchangers (GHEs). Field thermal response tests (TRTs) were conducted on a PHC energy pile and on a general vertical GHE installed in a multiple layered soil ground. The equivalent ground thermal conductivity was determined by using the results from TRTs. A simple analytical solution is suggested in this research to derive an equivalent ground thermal conductivity of the multilayered soils for vertically buried GHEs. The PHC energy pile and general vertical system were numerically modeled using a three dimensional finite element method to compare the results with TRTs'. Borehole thermal resistance values were also obtained from the numerical results, and they were compared with various analytical solutions. Additionally, the effect of ground thermal conductivity on the borehole thermal resistance was analyzed.

• Journal of the Korean earth science society
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• v.22 no.3
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• pp.179-185
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• 2001

Borehole tests are commonly used as a tool to obtain the physical properties of soils and rocks. The results of borehole tests are, however, discontinuous. Interpolation methods are applied to interpret the data gap between the borehole test points. The interpolation is valid only if the horizontal variations of the ground between the test points are small enough to ignore. A surface wave inversion method was used to study the S wave velocity of the very soft soil to provide the continuous 2 dimensional S wave velocity structure. The resolution of the S wave velocity structure was used to interpret the inversion results.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.45-51
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• 2009

A ground-loop heat exchanger in a ground source heat pump system is an important unit that determines the thermal performance of a system and its initial cost. The size and performance of this heat exchanger is highly dependent on ground thermal properties. A proper design requires certain site-specific parameters, most importantly the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. This study was performed to investigate the effect of some parameters such as borehole lengths, various grouting materials and U-tube configurations on ground effective thermal conductivity. In this study, thermal response tests were conducted using a testing device with 9-different ground-loop heat exchangers. From the experimental results, the length of ground-loop heat exchanger affects to the effective thermal conductivity. Among the various grouting materials, the bentonite-based grout with silica sand shows the largest thermal conductivity value.

• 한국지구물리탐사학회:학술대회논문집
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• 2009.10a
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• pp.155-159
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• 2009

Crack-controlled method which utilizes the dynamic energy such as explosives and propellent gases have been applied to the development of mineral resource and oil and civil engineering. It is necessary to consider the fracture processes associated with the material properties and external forces to control crack propagation using borehole pressure. To investigate the influence of the applied borehole pressure waveform on the crack propagation in rock masses having different material properties, a no-free surface model was used, consisting of a borehole in rock with a continuous boundary. Loading rates ranging from 1 to 100MPa/${\mu}s$ with different rock mass properties was employed to investigate the loading rate dependency of fracture patterns in the rock mass.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.489-492
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• 2007

Understanding the thermohydraulic processes in the aquifer is necessary for a proper design of the aquifer thermal energy utilization system under given conditions. Experimental and numerical test were accomplished to evaluate the relationship between the geothermal heat exchanger operation and hydrogeological conditions in the open-loop geothermal system. Sand tank experiments were designed to investigate the open-loop geothermal system. Water injection and extract ion system as open-loop borehole heat exchanger was applied to observe the temperature changes in time at injection well, extraction well and ambient groundwater. The thermohydraulic transfer for heat storage was simulated using FEFLOW for two cases of extraction and injection phase operation in sand tank model. As one case, the movement of the thermal plume was simulated with variable locations of injection and extraction well. As another case, the simulation was performed with fixed location of injection and extraction well. The simulation and experimental results showed that the temperature distribution depends highly on the injected water temperature and the length of injection time and the groundwater flow and pumping rate sensitively affect the heat transfer.

• Computers and Concrete
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• v.18 no.6
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• pp.1135-1151
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• 2016

For investigating the effect of the pre-existing joints on the initiation pattern of hydraulic fractures, the numerical simulation of circular holes under internal hydraulic pressure with a different pattern of the joint distributions are conducted by using a finite element code, FRANC2D. The pattern of hydraulic fracturing initiation are scrutinized with changing the values of the joint length, joint offset angle. The hydraulic pressures with 70% of the peak value of borehole wall breakout pressure are applied at the similar models. The simulation results suggest that the opening-mode fracture initiated from the joint tip and propagated toward the borehole for critical values of ligament angle and joint offset angle. At these critical values, the crack grow length is influenced by joint ligament length. When the ligament length is less than 3 times the borehole diameter the crack growth length increases monotonically with increasing joint length. The opening-mode fracture disappears at the joint tip as the ligament length increases.