• Geophysics and Geophysical Exploration
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• v.7 no.4
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• pp.225-233
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• 2004

The purpose of this study is to provide the geo-technical information by assessment of the in-situ rock strength using the reflected wave energy and travel time data acquired by the borehole acoustic scanner. In order to compare and analyze the relationship between the uniaxial compressive strength and the reflected wave energy, the laboratory test and the borehole acoustic scanning were conducted for the set of specimens, such as mortar, concrete, and rock samples which have different rock type. Finally, we verified the applicability of the reflected wave energy acquired by the borehole acoustic scanner to quantitatively estimate the in-situ rock strength.

• Journal of electromagnetic engineering and science
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• v.14 no.2
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• pp.79-81
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• 2014

In B-scan data measured by a pulse-type monostatic borehole radar, target signatures are seriously obscured by two clutters that differ in orientation and intensity. The primary clutter appears as a nearly constant time delay, which is caused by internal ringing between antenna and transceiver in the radar system. The secondary clutter occurs as an oblique time delay due to the guided borehole wave along the logging cable of the radar antenna. This issue led us to perform adaptive filtering processing for orientation-based clutter removal. This letter describes adaptive filtering processing consisting of a combination of edge detection, data rotation, and eigenimage filtering. We show that the hyperbolic signatures of a dormant air-filled tunnel target can be more distinctly enhanced by applying the proposed approach to the B-scan data, which are measured in a well-suited test site for underground tunnel detection.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.427-432
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• 2005

This study treats the advantage of in situ line source method measuring the heat transfer capacity of a borehole, using mobile equipment, to determine the thermal properties of the entire borehole system such as thermal conductivity, diffusiveity. volumetric heat capacity, and borehole thermal resistance. The results from the response test include not only the thermal properties of the ground and the borehole, but also conditions that are difficult to estimate, e,g. natural convection in the boreholes, asymmetry in the construction, etc. In this study, 1) theoretical in situ methods for assessing working fluid temperature variation in V-type PE tube have been introduced, and 2) TRTE(Thermal Response Test Equipment) has been built based on these kinds of theoretical in situ methods. Basically TRTE consists of a pump, a heater and temperature sensors for measuring the inlet and outlet temperatures of the borehole. In order to make equipment easily transportable it is set up on a small trailer. Since the response test takes above two days to execute, the test was fully automatic in recording measured data using Labview DAS(Data acquisition system) program. The test was demonstrated in the course of intensive research in this field through the one site at Ulsan city in Korea. From this kind of thermal properties test of borehole systems in situ, the design of the borehole system can be optimized regarding the total geological, hydro-geological and technical conditions at the location.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.581-586
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• 2009

Knowledge of ground thermal properties is most important for the proper design of large scale BHE(borehole heat exchanger) systems. The type, pipe size and thermal performance of the BHE is highly dependent on the ground source heatpump system-efficiency and instruction cost. Thermal response tests with mobile measurement devices were developed primarily for insitu determination of design data for large diameter BHE for triple-U spacer apply. The main purpose has been to determine insitu values of effective ground thermal conductivity and thermal resistance, including the effect of ground-water flow and natural convection in the boreholes. The test rig is set up on a some trailer, and contains a circulation pump, a inline heater, temperature sensors, flow meter, power analysis meter and a data logger for recording the temperature, fluid flow data. A constant heat power is injected into the borehole through the tripl-U pipes system of test rig and the resulting temperature change in the borehole is recorded. The recorded temperature data are analysed with a line-source model, which gives the effective insitu values of rock thermal conductivity and borehole thermal resistance of large diameter BHE for spacer apply.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.2
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• pp.161-167
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• 1999

There is an increasing need for the estimation of foundation piles whose depths are unknown. Especially in repair and reinforcement works or in safety inspection and assessment to the big structures whose foundations are piles, the accurate information about the depth of foundation piles is one of the most important factors. A borehole magnetic tool has been developed and tested to meet this object. The fundamental base is that there usually exist many re-bars inside the foundation structure such as piles, and these re-bars are ferromagnetic materials which cause strong induced magnetic field comparable to the earth magnetic field. It utilizes flux-gate type magnetometer which measures 3-components of the magnetic field. Taking vertical derivatives of vertical component of the measured magnetic field, we can expect the error limit of estimating the depth of the pile end less than 20 cm in favorable condition. The maximum measurable distance is about 3 m to the pile from the borehole. The field data show that borehole magnetics is one of the most accurate, fast, and reliable methods for this object so far, as long as there is no magnetic materials such as deep located steel pipe or power cables close to the foundation piles.

• Journal of the Korean Geotechnical Society
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• v.29 no.10
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• pp.49-56
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• 2013

The use of geothermal energy has been increased for economic and environmental friendly utilization. Ground thermal conductivity and borehole thermal resistance are very important parameters in the design of geothermal heat pump system. This paper presents an experimental study of heat exchange rate of U and W type ground heat exchangers (GHEs) measured by thermal performance tests (TPTs). U and W type GHEs were installed in a partially saturated dredged soil deposit, and TPTs were conducted to evaluate heat exchange rates under 100-hr continuous operation condition. The heat exchange rates were also calculated by analytical models to estimate borehole thermal resistances and were compared with experimental results. It comes out that multi-pole and equivalent diameter (EQD) models resulted in more accurate agreement than shape factor (SF) model which is currently more often used.

• KCID journal
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• v.2 no.1
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• pp.57-64
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• 1995

현장 투수시험 방법 중에서 Borehole type의 Boutwell Permeameter와 Constant head bore-hole permeameter, 그리고 Porous probe type의 cone shaped porous probe(BAT Permeameter)에 대한 내용을 간단히 소개하였고, 각 측정법의 특징을 비교분석한 내용을 요약하면 (표-1)과 같으며, 기회가 있으면 Infiltrometer type와 Underdrain type에

• Economic and Environmental Geology
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• v.34 no.3
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• pp.255-269
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• 2001

The geochemical studies on groundwater in the borehole, which is straddled by multi-packer (MP) system, were carried out from a volcanic terrain in the Yeosu area. The pH of groundwater collected from selected sections in the MP-installed borehole is much higher (up to 9.6) than that of the borehole groundwater (7.0-7.9) collected using conventional pumping technique. Hydrochemistry shows that the groundwater has a typical chemical change with increasing sampling depth, suggesting that the groundwater is evolved through water-rock interaction along the fracture-controlled flow paths. The groundwater from the deeper part (138-175 m below the surface) in borehole KI is characterized by the Ca-C11 type with high Ca (up to 160 mg/L) and Cl (up to 293 mg/L) contents, probably reflecting seawater intrusion. The groundwater also has high sodium and sulfate contents compared to the waters from other boreholes. These observed groundwater chemistry is explained by the cation exchange, sulfide oxidation, and mixing process with seawater along the flow path.

• Geophysics and Geophysical Exploration
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• v.17 no.3
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• pp.155-162
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• 2014

We performed MCNP modeling for density log, and examined its reliability and validity comparing the correction curves from physical borehole model. Based on the constructed numerical model, numerical modelings of density sonde in three-inch borehole were carried out under the various conditions such as the existence and type of casing or fluid, and also the stand-off between the sonde and borehole wall. These results of numerical modeling quantitatively reflect effects of casing and fluid in borehole, and moreover, demonstrate constant patterns with interval change from borehole wall. From this study, numerical modeling using MCNP shows a good applicability for well logging, and therefore, can be efficiently used for the calibration of well logging data under the various borehole conditions.

• Geomechanics and Engineering
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• v.1 no.2
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• pp.155-168
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• 2009

Breakdown pressures obtained from the classic, linear elastic breakdown model are compared with the corresponding pressures obtained using a nonlinear material model. Compression test results obtained on sandstone and siltstone are used for that purpose together with previously formulated nonlinear model which introduces elasticity functions to address nonlinear stress-strain behaviour of rocks exhibiting stress-dependent mechanical properties. Linear and nonlinear collapse pressures are also compared and it is shown that material nonlinearities have significant effect on both breakdown and collapse pressures and on tangential stresses which control breakdown pressure around a borehole. This means that the estimates of ${\sigma}_H$ made using linear models give stress values which are different than the real values in the earth. Thus the importance of a more accurate analysis, such as provided by the nonlinear models, is emphasised. It is shown, however, that the linear elastic model does not necessarily over-predict borehole stresses and the opposite case can be true, depending on rock type and test interpretation.