• Tunnel and Underground Space
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• v.7 no.4
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• pp.299-309
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• 1997

Soil and rock improvement and reinforcement techniques are applied to achieve safe tunnel excavation in difficult geological conditions. The Umbrella Arch Method(UAM), one of the auxiliary techniques, is used to reduce ground permeability and improve stabtility of the tunnel by inserting a series of steel pipes into ground around the crown inclined to the longitudinal axis of the tunnel. Additionally, multi-step grouting is added through the steel pipes. UAM combines the advantages of a modern forepoling system with the grouting injection method. This technique has been applied in subway, road and utility tunneling sites for the last few years in Korea. This paper presents the results of analysis of the case studies on ground movements associated with UAM used in the Seoul Subway line 5 constructon site. Improvement of tunnel stability and decrease of ground settlement expected with pipe insertion are also discussed. Finally, the method to minimize ground settlements caused by NATM tunnelling are suggested.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.423-428
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• 2007

This study was performed to construct a geothermal data base about thermal conductivity of ground heat exchanger and thermal properties of grouting material which used to refill the borehole. We have acquired geothermal data sets from 39 sites over wide area of South Korea except to Jeju island. From data analysis, the range of thermal conductivity is 1.5$\sim$4.0 W/mK. It means that thermal conductivity varies with grouting material as well as regional geology and ground water system.

• 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.

• Journal of the Korean Geotechnical Society
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• v.23 no.8
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• pp.87-95
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• 2007

This study analyzed ground settlement and ground stress depending on tunnel excavation and the ground reinforcing grouting methods for double line road tunnel through deep weathered zone. Diameter of double line road tunnel was approximately 12m and umbrella arch method and side wall reinforcing grouting were applied. The ring-cut split excavation method and CD-cut excavation method for excavation method were applied. Analyses of failure rate and vertical stress ratio show that the tunnel for which the height of the cover (H) was higher than four times the diameter, can be considered a deep tunnel. Comparisons of various excavation and ground reinforcement methods showed that CD-cut method results in lower surface and crown settlement, and lower failure rate than that obtained by Ring-cut split method. In addition, the side wall reinforcing grouting resulted in reduction of tunnel displacement and settlement.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.115-127
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• 2019

The low-flow grouting injection technique, the target construction method for this study, is a method of pouring mortar into the ground by non-emission replacement principle, which can be expected to increase the density of the ground, and, in some cases, be used as a base file using the strength of the high injection solids, along with low noise, low pollution, and high durability. To verify that the dynamic characteristics of the ground are improved by the low-flow injection technique, the test work was conducted on the site and physical tests were performed, and the quality of the improvement formed in the ground was verified through the indoor test on the core and core recovery rate was analyzed. The density logs test layer calculated the volume density of the ground layer by using the Compton scattering of gamma-rays, and the sonic logs was tested on the ground around the drill hole using a detector consisting of sonar and receiver devices inside the drill hole. As a result of the measurement of the change in physical properties (density and sonic logs) before and after grouting, both properties were basically increased after infusion of grout agent. However, the variation in density increase was greater than the increase in speed after grouting, and the ground density measurement method was thought to be effective in measuring the fill effect of the filler. Strength and core recovery rates were measured from specimens taken after the age of 28 days, and the results of the test results of the diffusion and strength test of the improved products were verified to satisfy the design criteria, thereby satisfying the seismic performance reinforcement.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.466-469
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• 2007

Heat pumps are used for air-conditioning systems in commercial buildings, schools, and factories because of low operating and maintenance costs. These systems use the earth as a heat source in heating mode and a heat sink in cooling mode. Ground heat exchangers are classified by a horizontal type and vertical type according to the installation method. A horizontal type means that a heat exchanger is laid in the trench bored in 1.2 to 1.8 m depth. And a vertical type is usually constructed by placing small diameter high density polyethylene tube in a vertical borehole. Vertical tube sizes range from 20 to 40 mm nominal diameter. Borehole depth range between 100 and 200 m depending on local drilling conditions and available equipment. In this study, to evaluate the performance of single u-tube with bentonite grouting, single u-tube with broken stone grouting and double n-tube bentonite grouting of vertical ground heat exchangers, test sections are buried on the earth and experimental apparatus is installed. Therefore the heat transfer performance and pressure loss of these are estimated.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.621-628
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• 2002

Compaction Grouting Pack (CGP) Anchor which is composite anchor of bearing plus friction-type was chosen and executed for the open-cuts in soft ground. This paper presents an analysis of data from tests on composite-anchor by jacking force. The properties of composite-anchor was presented to be as follows , the maximum plastic displacement was 60 mm in abandoned coal fill deposit, the shear stress($\tau$) is expressed as $\tau$ = (equation omitted) kg/$\textrm{cm}^2$ in clayey silt.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.899-904
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• 2009

This paper presents the analysis result of load-transfer mechanism and pile movements associated with the development of frictional resistance to understand the engineering characteristics of micropile behavior. An field load tests were performed for two different types of micropiles and they are (i) thread bar reinforcement with D=50mm and (ii) hollow steel pipe reinforcement with $D_{out}$=82.5mm and $D_{in}$=60.5mm and wrapped with woven geotextile for post-grouting. The load test results indicated that micropiling with pressured grouting provided better load-transfer characteristics than micropiling with gravity grouting under both compressive and tensile loading conditions in that unit skin frictional resistance is well distributed along installation depth. The unit weight and unconfined compressive strength of cured grout were obtained for each piling method. The strength and unit weight of micropile with pressured grouting was higher than those with gravity grouting. The fact that load bearing quality with pressured grouting is better than that of gravity grouting could be attributed to the dense mutual adhesion between surrounding ground and pile due to pressurized grouting method and better grout quality.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.257-266
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• 2019

Ground water generated under tunnel excavation has a major impact on tunnel construction and stability. Thus, effective waterproof grouting is needed to reduce the inflow of groundwater. Most tunnel designs are applying the Pre Grouting. However there are no propriety analysis for grouting material and waterproof effect. In this study, numerical analysis was performed in order to investigate the effect of waterproof with decrease of coefficient of permeability of the grouting area based on the case of grouting construction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.235-244
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• 2016

Grouting is frequently used before the construction of subsea tunnels to mitigate problems that can occur in weak ground zones such as joints, faults or unconsolidated settlements during construction. The grout material injected into rock mass often flows through the discontinuities present in the host rock and hence, joint properties such as its distribution, roughness and thickness greatly affect the properties of grouting-improved rocks. The grouting-improved zones near subsea tunnels are also subjected to high water pressures that can cause long-term weathering in the form of changes in grout microstructure and crack formation and lead to subsequent changes in ground properties. Therefore, an assessment method is needed to accurately measure changes in the grouting-improved zones near subsea tunnels. In this study, the elastic wave propagation characteristics in grouting-improved rocks were tested for various axial stress levels, curing time, joint roughness and thickness conditions under laboratory conditions and the results were compared with wave velocity standards in different Korean rock mass classification systems to provide a basis for inferring improvement in grouted rock-mass.