• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3401-3406
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• 2007

This study was performed to acquire the reliable in-situ thermal conductivity of closed type ground heat exchanger used in ground source heat pump. We selected four sites(Cheonan, Daejeon, Daegu, Gwangju) which are central area of South Korea. Test results show that the effective thermal conductivities are 2.33 W/m$^{\circ}C$, 2.50 W/m$^{\circ}C$, 2.75 W/m$^{\circ}C$ and 2.86 W/m$^{\circ}C$. From this data, we can see that thermal conductivity varies about the range of 23% with the sites. Also, thermal conductivity increases up to 20% by changing grouting material from low salica sand to high one.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1786-1792
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• 2011

If the concrete track is settled excessively, it must be restored or reinforced immediately. Especially, reinforcement/restoration method should be applied without affecting on train operation. To deal with this problem, special equipment, process and material should be prepared. This paper suggest a special mixing ratio to restore the settled concrete track. Materials are classified the quick hardening mortar and the middle hardening mortar. The quick hardening mortar is used to restore the settled track and the middle hardening mortar is used to fill the void. These materials must have the appropriate gel time(1-40sec) and compressive strength($5kg/cm^2$). Various compounds is used and the micro cement is used as a main base.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1090-1095
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• 2004

Umbrella Arch Method(UAM), among others. is commonly applied to increase the facial stability during tunnel excavation and, depending on the field condition, additional reinforcement techniques can be used simultaneously. UAM, together with grouting method, is normally used to reduce ground permeability and improve stability of the tunnel by inserting a series of steel pipes into the ground around the crown inclined to the longitudinal axis of the tunnel. However. there has not been much rigorous study on the effectiveness of UAM, and most of UAM installations depend on empirical judgement rather than on engineering calculation, .In this study, the effectiveness of UAM is demonstrated based on the constitutive relationship involving UAM derived from the mechanics of composite material, and the numerical investigation is compared with small scale experiments on the tunnel reinforcement.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.118-119
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• 2017

In the S.C.W (soil cement wall) grouting solution, Cement grout ratio of 1 part Portland cement and 1part water is being used. However, Co₂ and harmful heavy metals such as cr6+ are discharged in the process, causing a serious environmental issue. The purpose of the present study is therefore to substitute cement grout to inorganic binder and identify durability properties of ground solidification materials.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.761-768
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• 2008

This paper presents the results of a laboratory study on the thermal conductivity of sand(silica, quartzite, limestone, sandstone, granite and masonry sand)-water mixtures used in ground heat exchanger backfilling materials. Nearly 260 tests were performed in a thermal conductivity measuring system to characterize the relationships between the thermal conductivity of mixtures and the water content. The experimental results show that the thermal conductivity of mixtures increases with increasing dry density and with increasing water content. The most widely used empirical prediction models for thermal conductivity of soils were found inappropriate to estimate the thermal conductivity of unsaturated sand-water mixtures. An improved model using a exponential relationship to compute the thermal conductivity of dry sands and empirical relationship to assess the normalized thermal conductivity of unsaturated sand-water mixtures is presented.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.2
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• pp.1-9
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• 2019

In a ground-source heat pump (GSHP) system, a vertical ground heat exchanger (GHE) is widely accepted due to a higher thermal performance. In the vertical GHE, grout (also called grouting material) plays an important role in the heat transfer performance and the initial installation cost of the GHE. Bentonite-based grout has been used in practice because of its high swelling potential and low hydraulic conductivity. This study evaluated the thermo-physical properties of the bentonite-based grouts through lab-scale measurements. In addition, we conducted performance simulation to analyze the effect of mixed ratio of grouts on the design length and thermal performance of the vertical GHE. The simulation results show that thermally-enhanced grouts improve the heat transfer performance of the vertical GHE and thus reduce the design length of GHE pipe.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.2
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• pp.189-198
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• 2003

For the huge section of tunnel, it is highly required to observe the role of each rock support and their effect of rock reinforcement in order to investigate more reasonable rock support structure. Especially for unstable tunnel situation with no shotcrete strength right after an excavation, sufficient investigation is needed for rock support structure. In this paper, we clarify the relations of compressive strength and material age, cohesion strength and material age, and cohesion stiffness and material age of grout with time-dependence through tests and numerical analysis simulation with trial rock mass considering hardening of bolt grouting material. By means of this process, effect of rock reinforcement for rockbolt is investigated right after an excavation and modelling and physical constants of young aged rockbolts are obtained. Additionally, the effect of rock reinforcement with hydraulic tensile friction bolt is examined right after an excavation, which grout effect is no need to be waited.

• The Journal of Engineering Geology
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• v.18 no.3
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• pp.245-255
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• 2008

The variation of the electrical property of embankment material was analyzed from laboratory experiments and the result of field survey, in order to enhance the interpretation of electrical resistivity survey frequently used for safety assessment of embankment. At first, the kaolinite, showing similar physical property with core material of embankment, was used to examine the variation of the resistivity value according to degree of consolidation. The test showed that a drop of shear strength induces increase of resistivity value regardless of degree of water content. This result means that porous zones of weak core material in embankment may be appeared as highly resistive part in the electrical resistivity survey. This observation implies that it may fail to detect weak core material by electrical method, if we only try to and zones showing low resistivity value. And, we performed Standard Penetration Test (SPT) to analyze the correlation between electrical property and ground stiffness. Finally, a mechanism to describe the variation of electrical resistivity due to grouting effect was proposed and real field data were analyzed.

• Journal of the Korean Geosynthetics Society
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• v.16 no.3
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• pp.21-30
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• 2017

Cement grouting method is generally applied for the purpose of reinforcement of deteriorated reservior. Problems have been raised due to the limit of the injection material. In order to solve these problems, various grout materials have been developed. However, there are many cases in which the grounds are disturbed in actual field. In this study, the physical properties of hybrid grout with high fineness and high viscosity characteristics were analyzed to enable penetration into the ground. Optimum inflation agent was selected and mixed with the grout. The pressure and compaction effect on expansion was examined and its effectiveness was verified. From the result of confirming expansion ratio, uniaxial compressive strength, expansion pressure and compaction effect, the HI-E (2%) sample was analyzed to be excellent in improvement effect by the inflation agent. Hence, hybrid grout can be effectively applied for the impermeable and reinforcement method of deterioration reservoir and tide embankment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.1
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• pp.77-89
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• 2020

Submerged floating tunnel (SFT) is a type of tunnel that allows tunnel segments to float underwater by buoyancy, and is being actively studied in recent years. When the submerged floating tunnel is connected to the ground, the tunnel and the bored tunnel inside the ground must be connected. There is risk that the stress will be concentrated at the connection between the two tunnels due to the different constraints and behavior of the two tunnels. Therefore, special design and construction methods should be applied to ensure the stability around the connection. However, previous studies on the stability at the connection site have not been sufficiently carried out, so study on the basic stage of the stability at connection site are necessary. In this study, numerical analysis simulating the connection between submerged floating tunnel and the bored tunnel confirmed that the shear strain concentration occurred in the ground around the connection, and it was analyzed that the structural factors can be handled during construction to have effects on the stability of the ground around the connection. Numerical results show that the risks from disproportionate displacements in the two tunnels can be mitigated through the construction of grouting material and joint design. Although the results from this study are qualitative results, it is expected that it will contribute to the determination of structural factors and risk areas that should be considered in the design of connections between the submerged floating tunnel and bored tunnel in the future studies.