• Title/Summary/Keyword: Borehole test

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In-Situ Experiment Method on Evaluation of Debris Flow (토석류 발생량 평가를 위한 현장시험 방법)

  • Song, Byungwoong;Yoon, Hyunseok;Kim, Seongmoon
    • Journal of the Korean GEO-environmental Society
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    • v.14 no.7
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    • pp.31-38
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    • 2013
  • After debris flow caused damage during recent years, many scholars and engineers have thrown their effort into analyzing risk from debris flow in Korea. But it is hard to predict damage by debris flow taken place in wide area. Recently, SINMAP program is widely well used to estimate the amount of debris flow and its' range. In order to make frequent use of it, the most important thing is selection of accurate input parameters. In-situ experiments, which are avaliable in the mountain, is to be suggested to get dependable input parameters for SINMAP. Those are permeability, cohesion, density, friction angle and thickness in SINMAP. To get those, test pit, block sampling, in-situ density test, auger boring, permeability test on ground surface, borehole shear test and dynamic cone test and so forth were selected. In addition, the reliability of the results will be increased through comparing with those by laboratory tests. Hence, the experiments are hard to enter the sites without temporary road and, if possible, licensing and many times are needed, too. Small size experiments are indeed necessary to get accurate parameters.

Study on Moye's Method for Analysis of Constant-Head Tests Conducted in Crystalline Rock (결정질 암반에서 Moye 방법을 이용한 정압시험의 해석에 대한 고찰)

  • Kyung-Woo Park;Byeong-Hak Park;Sung-Hoon Ji;Kang-Kun Lee
    • The Journal of Engineering Geology
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    • v.33 no.4
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    • pp.519-530
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    • 2023
  • Moye's analytical solution was examined as a method for constant-head tests under steady-state conditions, and results were compared with transient-state analyses in in situ hydraulic tests. The sensitivity of hydraulic conductivities calculated using Moye's method increased with the length of the test section, which should be as large as possible under test conditions. Particularly in low-permeability media with less than 10-8 m/sec of hydraulic conductivity, hydraulic conductivity is lower than that under transient-state conditions and can be recalculated by adjusting the boundary between radial and spherical flow assumed in Moye's equation. Constant-head tests performed in the research borehole at the KAERI Underground Research Tunnel (KURT) indicated that transmissivities derived from the constant-head withdrawal test under transient-state conditions in low-permeability media were higher than those derived from steady-state tests, likely because the groundwater flow boundary was smaller than the "half of the test-section length"assumed by Moye's equation. When interpreting constant-head test results for crystalline rock, the hydrogeological properties of the medium may be better understood by considering assumed conditions accompanying analysis of the steady-state condition and comparing them with results for the transient-state analysis, rather than simply assuming properties based on steady-state analyses.

Evaluation of Ground Thermal Conductivity by Performing In-Situ Thermal Response test (TRT) and CFD Back-Analysis (현장 열응답 시험(TRT)과 CFD 역해석을 통한 지반의 열전도도 평가)

  • Park, Moonseo;Lee, Chulho;Park, Sangwoo;Sohn, Byonghu;Choi, Hangseok
    • Journal of the Korean Geotechnical Society
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    • v.28 no.12
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    • pp.5-15
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    • 2012
  • In this study, a series of CFD (Computational Fluid Dynamics) numerical analyses were performed in order to evaluate the thermal performance of six full-scale closed-loop vertical ground heat exchangers constructed in a test bed located in Wonju. The circulation HDPE pipe, borehole and surrounding ground formation were modeled using FLUENT, a finite-volume method (FVM) program, for analyzing the heat transfer process of the system. Two user-defined functions (UDFs) accounting for the difference in the temperatures of the circulating inflow and outflow fluid and the variation of the surrounding ground temperature with depth were adopted in the FLUENT model. The relevant thermal properties of materials measured in laboratory were used in the numerical analyses to compare the thermal efficiency of various types of the heat exchangers installed in the test bed. The simulation results provide a verification for the in-situ thermal response test (TRT) data. The CFD numerical back-analysis with the ground thermal conductivity of 4 W/mK yielded better agreement with the in-situ thermal response tests than with the ground thermal conductivity of 3 W/mK.

Analysis of transmissivity tensor in an anisotropic aquifer (이방성 대수층에서의 투수량계수텐서 해석)

  • 강철희;이대하;김구영;이철우;김용제;우남칠
    • Journal of Soil and Groundwater Environment
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    • v.7 no.2
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    • pp.53-61
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    • 2002
  • An Aquifer test was carried out on five boreholes to determine the hydrologic anisotropy and the major groundwater flow direction in the aquifer system of the study area. With an assumption of the aquifer's anisotropy and homogeneity, the major transmissivity(T(equation omitted)), the minor transmissivity( $T_{ηη}$ ), and primary tensor direction ($\theta$) for each borehole were determined from the test. Besides the boreholes BH-1, BH-4 and BH-5, the anisotropy transmissivity tensor values of BH-2 and BH-3 did not correspond with the assumption. Thereafter the values were plotted on the polar coordinate, and showed that the tensor values were out of the anisotropy ellipsoid due to the high heterogeneity of BH-2 and BH-3 comparing with the other boreholes. Therefore. the anisotropy of the aquifer was examined from BH-1, BH-4. and BH-5. In BH-1, T(equation omitted) is 171.9 $\m^2$/day. $T_{ηη}$ is $71.01\m^2$/day, and the principal tensor direction is Nl5.39$^{\circ}$E. In BH-4. T(equation omitted) is $268.2 \m^2$/day, $T_{ηη}$ / is $28.75\m^2$/day and the principal tensor direction is N7.55$^{\circ}$E. In BH-5, T(equation omitted) is $168.4\m^2$/day, $T_{ηη}$ is 66.80 $\m^2$/day, and the principal tensor direction is $N76.59^{\circ}$E. On the basis of teleview logging performed on each borehole. the principal fracture directions were revealed as $N0^{\circ}$~4$^{\circ}$E/$30^{\circ}$~$50^{\circ}$SE and $N30^{\circ}$~$80^{\circ}$W/$20^{\circ}$~$50^{\circ}$NE that are the most frequently occurred sets as well as that correspond well with the calculated transmissivity tensor.

Case Study on the Failure Causes of Gneiss Slope Occurred Tension Crack (편마암비탈면에서 인장균열 파괴원인 사례 연구)

  • Chun, Byungsik;Noh, Insoo;Kong, Jinyoung;Kim, Juhyong
    • Journal of the Korean GEO-environmental Society
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    • v.13 no.11
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    • pp.27-35
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    • 2012
  • The discontinuity of rock is one of important elements that have impact on the dynamic movement of rock. A slope made of gneiss has complicated geological structure because of the gneiss forming process through metamorphism covering wide range and the anisotropic structure with foliation. In this study, before cutting slope, the rock of slope had been found as a good quality by the boring test. But during construction tension cracks had occurred in the section with 170m length during large-scale excavation work with depth more than 20m. Ground surface geological investigation, boring exploration, resistivity logging and borehole image processing had been done to find the causes of the tension crack. It was possible to estimate the scale of fault existing in large area through resistivity logging and geological investigation. Large scale slickenside and fault clay had been found as the result of comprehensive analysis.

Evaluation of Reinforcing Effects of Pressure-Injected Grouting Nail in Weathered Rock (풍화암 사면에서의 압력분사 그라우팅 네일 보강 효과 연구)

  • Hwang, Young-Cheol;Kim, Nak-Young
    • Journal of the Korean GEO-environmental Society
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    • v.3 no.1
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    • pp.47-55
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    • 2002
  • The slope reinforcing method utilized in this paper reinforces the ground overall by means of filling borehole as well as permeating grout material into ground by injecting it through the grouting pipe. In order to reflect these characteristics to design, not only the ground reinforcing effect by the structural material itself but also the ground strength improvement effect by the grouting injection must be quantitively evaluated. But precedent research of it has been insufficient. Therefore, the slope reinforcing method was applied to the weathered rockmass slope situated in the highway in order to analyze reinforcing effect and the instrumentation of slope was performed. Through analysis of this field test, the slope reinforcing method was proved to be effective and back analysis method based on instrumentation values of slope was proposed to apply to reinforcing design. In this paper, the effectiveness of reinforcing method was certified through proposed back analysis.

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Stability Assessment of Building Foundation over Abandoned Mines (채굴 지역에서의 건축물 기초 지반 안정성 평가 연구)

  • 권광수;박연준
    • Tunnel and Underground Space
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    • v.11 no.2
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    • pp.174-181
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    • 2001
  • The cavities created by underground mining, if remained unfilled, can cause ground settlement and surface subsidence as a result of relaxation and breakdown of the carven roof. Construction of structures above the underground mine cavity will have serious problems concerning both structural stability and safely even if the cavity is back-filled. This study was conducted to confirm the location and condition of the cavern as well as the state of the back-fill in A mine area using core logging and borehole camera. The bearing capacity and other mechanical properties of the ground were also measured by the standard penetration test(SPT). Obtained data were used to assess the stability of the ground and the structures to be built by numerical analysis using FLAC. The site investigation results showed that the mine cavities were filled with materials such as boulder and silty sand(SM by unified classification). Result of the numerical analyses indicated that constructing building structures on the over-lying ground above the filled cavities is secure against the potential problems such as surface subsidence and ground settlement.

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Displacement and Stress Monitoring for Excavation Deep Foundation (인접지역의 깊은 터파기 굴착에서 변위 및 응력의 계측)

  • 원연호
    • Explosives and Blasting
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    • v.17 no.1
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    • pp.27-55
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    • 1999
  • The excavation works for deep foundation in urban areas have recently increased complaints of blasting vibration and settlement of ground level. Foundation must be excavated approximately up to 24-28m depths from the surface. The roads and subway line pass through the excavation area. The Dae-chung station is also located at the nearest distance 5-35m from the working site. To protect subway station and adjacient some structures from blasting and settlement, the level of ground vibration, displacements and stress were monitored and analyzed. The results can be summarized as follows ; 1. An empirical particle velocity equation were obtained by test blasts at Nassan Missi 860 Office tel construction site. $V{\;}={\;}K(D/\sqrt{W})^{-n}$, where the values for n and k are estimated tobe 0.371 and 1.551. From this ground vibration equation, the max. charge weight per delay time against distance from blasting point is calculated. Detailed blasting method is also presented. 2. To measure the horizontal displacement in directions perpendicular to the borehole axis, 6 inclinometers installed around working sites. The displacement at the begining was comparatively high because the installation of struts was delayed, but after its installation the values showed a stable trend. Among them, the displacement by 3 inclinometers installed on a temporary parking area showed comparatively high values, for example, the displacement measured at hole No. IC-l recoded the max. 47.04mm for 6 months and at hole No. IC-2 recorded the max. 57.33mm for 7 months. So, all of these data was estimated below a safe standard value 103mm. 3. Seven strain gauge meter was installed of measure the magnitude and change of stress acted on structs. The measured value of maximum stress was $-465{\;}kgf/\textrm{cm}^2,{\;}-338.4{\;}kgf/\textrm{cm}^2,{\;}302.3{\;}kgf/\textrm{cm}^2$ respectively. In compareto the allowable stress level of steel, they are estimated to be safe.

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Analysis of the statistical properties for the background fractures in the LILW disposal site of Korea (중.저준위 방사성폐기물 처분 부지 내 배경 단열의 통계적 특성 분석)

  • Ji, Sung-Hoon;Park, Kyung-Woo;Kim, Kyoung-Su;Kim, Chun-Soo
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.6 no.4
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    • pp.257-263
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    • 2008
  • We analyzed the statistical properties for the conductive background fractures in the Low and Intermediate Level Waste(LILW) disposal site to conceptualize of its groundwater flow system. The background fractures were classified to fracture sets based on their trends and plunges that were obtained from the borehole logging data, and then the fracture transmissivity distribution was inferred from the fixed interval hydraulic test results. The fracture size distribution of each fracture set was estimated using the fracture density and fracture mapping data. To verify the analyzed results, we compared observed field data to simulated one from the DFN model that was constructed with the analyzed statistical properties of the background fractures, and they showed a good agreement.

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Analyses of Correlation Between Groundwater Movement and Tidal Effect in West Costal Landfill Area (서해안 매립지 내 지하수유동과 조석에 관한 상관성 분석)

  • Park Jong-Oh;Song Moo-Yaung;Park Chung-Hwa
    • The Journal of Engineering Geology
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    • v.16 no.3 s.49
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    • pp.293-300
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    • 2006
  • The groundwater movement in the west costal landfill area was analyzed by measuring N value by Standard Penetration Test, coefficient of permeability by falling head method, linear structure analysis by Digital Elevation Method, groundwater flow direction and rate by flowmeter logging due to tidal variation in the each borehole. The coefficients of permeability of the weathered zone and of the marine deposit showed similar values although some values of weathered zone show smaller values than those of the marine deposit. The major groundwater flow and rate in the marine deposit observed as east-west direction due to tidal variation, but on the other hand it was observed as N45E in weathered zone which is the major direction of the linear structures in the area. 2 hours delayed changes of the groundwater flow direction was observed during the 24 hours observation, and it seems to be a travel time of the tidal wave which cause the continuous change of the hydaulic gradient of the groundwater.