• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1065-1070
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• 2004

Recenlty, there are many cases that structures are constructed on soft ground in domestic. Generally in those cases, appropriate geotechnical techniques for the ground are needed. In this study, an example for ground improvement of OO railroad station construction site is introduced and analyzed. The ground conditions of this site which is soft ground are that N value is under 6, average depth and ground water table is 24.4m, GL-1.7. So, as a countermeasure technique for bearing reinforcement, Compaction Grouting System (CGS) method was applied on construction site. To estimate the application of CGS method, piezo cone penetration test and static pile loading test were carried out during the construction. Results of analysis show that CGS method for improving the bearing capacity of soft ground is applicable for the ground well.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.119-124
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• 2008

Due to the recent development of instruments which enabled the measurements of subtle IP effect in the ground and analysis algorithms, complex resistivity (CR) method was expanding its application to various field. In this study, we applied the CR method to the test site where the ground reinforcement had been done by injecting the cement mortar for investigating the effect of ground reinforcement. For this site, resistivity monitoring and tomography survey was carried out while the ground reinforcement had been made by the grouting. From the result, the anomalous region that was shown on the result of resistivity 4D monitoring was coincident with those of phase section in the CR method, because the cement grouting material had the strong IP effects. It might be expected that the CR method should be very powerful surveying tool for the similar purpose.

• Geomechanics and Engineering
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• v.28 no.5
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• pp.531-546
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• 2022

Ground displacements caused by the construction of overlapping twin shield tunnels with small turning radius are complex, especially under special geological conditions of construction. To investigate the ground displacements caused due to shield machines in the unique calcareous sand layers in Israel for the first time and determine the main factors affecting the ground displacements, field monitoring, laboratory geological analysis, theoretical calculations, and parameter studies were adopted. By using rod extensometers, inclinometers, total stations, and automatic segment-displacement monitors, subsurface tunneling-induced displacement, surface settlement, and displacement of the down-track tunnel segments caused by the construction of an up-track tunnel were analyzed. The up-track tunnel and the down-track tunnel pass through different stratum, resulting in different construction parameters and ground displacements. The laws of variation of thrust and torque, soil pressure in the chamber, excavated soil quantity, synchronous grouting pressure, and grout volume of the two tunnels from parallel to fully overlapping orientations were compared. The thrust and torque of the shield in the fine sand are larger than those in the Kurkar layer, and the grouting amount in fine sand is unstable. According to fuzzy statistics and Gaussian curve fitting of the shield tunneling speed, the tunneling speed in the Kurkar stratum is twice that in the fine-sand stratum.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.480-488
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• 2010

The CGS method is non-discharge replacement method improving ground stiffness by the effect of static compaction with injecting very low slump mortar into ground, and is applied for increasing bearing capacity and filling ground cavity by lifting or restoring differential settled structures and preventing differential settlement. This paper suggests design of ground improvement and construction case history for civil engineering structures by CGS method. This method can be used for reinforcing soft ground and liquefaction of loose sandy soil. This method was used in SongDo area in Incheon Economic Free Zone due to its low vibration of ground while it can improve the soft soil where underground structures(subway and box culvert) are already existed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.653-664
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• 2015

When the structural analysis is performed for the concrete lining of the water pressure tunnel, many parameters are considered such as relaxed ground loads, internal water pressure, external water pressure, the shrinkage of the concrete lining, grouting pressure, etc. But, there are no standards and manuals for the structural analysis for the concrete lining of the water pressure tunnel. Above all, the external water pressure has an much effect on the stability of tunnel. So, in case that permeability of ground is large, the external water pressure should be decreased by installation of weep hole, or reinforced ground by ground improvement grouting should be pressed by the external water pressure instead. But, when weep hole is installed to reduce the external water pressure, the many problems may me occurred. Thus, reasonable approach for treatment of the external water pressure is necessary if weep hole is not installed. Therefore, the purpose of this study is to analyze design cases and studies for treatment of the external water pressure in performing structural analysis for the concrete lining of the water pressure tunnel, and to find reasonable method for tunnel lining modeling which is the treatment of the external water pressure according to permeability of ground and consequently the design of ground improvement grouting.

• Journal of the Korean Society for Railway
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• v.3 no.4
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• pp.213-218
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• 2000

Waste landfill is so loose that it may cause the insufficient bearing capacity and the differential settlement. And so, characteristics and conditions of the ground should be considered in applications of ground improvement in waste landfill. In this paper, analysis of field tests as the static loading test and the bearing capacity test were performed. In result, PG(Pack Grouting) pile method is proved effective and economic, because it could bring about the increase of end bearing capacity, the prevention of differential settlement and increase of density by expansion of pile.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.509-516
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• 2004

The measurement of abnormal change of temperature(temperature anomaly) will help determine the safety of various engineering constructions, as the measurement in body often used to diagnose one's health. Temperature anomaly can be occurred in leakage or seepage of water flow in rocks, and in ground water table etc. Grouting materials injected in fractured rocks generate heat during hardening process. The degree of temperature change is associated directly with heat flow characteristics, that is, thermal conductivity, specific heat capacity. density of the surrounding rocks and can afford to assess the grouting efficiency. However, in practice, the use of traditional temperature measuring technique composed of only one single thermal sensor has been fundamentally limited to acquire thermal data sufficient to use for that, partly due to the time-consuming measuring work, partly due to the non-consecutive quality of data. Thus, in this paper, a new concept of temperature measuring technique, what we call, thermal line sensor technique is introduced. In this, the sensors with an accuracy of $0.02^{\circ}$ are inserted at regular intervals in one line cable and addressed by a control device, which enables to fundamentally enhance the capability of data acquisition in time and space. This new technology has been demonstrated on diverse field model experiments. The results were simply meant to be illustrative of a potential to be used for various kinds of temperature measurements encountered in grouting and leakage problems.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.121-131
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• 2003

Tunneling in difficult geological conditions is often inevitable especially in urban areas. Ground improvement and reinforcement techniques are often required to guarantee safe tunnel excavations and/or to prevent damage to adjacent structures. The steel pipe-reinforced multistep grouting method has been recently applied to tunnel sites in Korea as an auxiliary technique. In this study, the face stability with steel pipe-reinforced multistep grouting was evaluated emphasizing the effect of seepage forces. The study revealed that the influence of the steel pipe-reinforced multistep grouting on the support pressure in dry condition is not significant while there is relatively a large amount of reduction in seepage forces by adopting the technique in saturated condition. The effect of the anisotropy of permeability on the seepage force acting on the tunnel face was also estimated by conducting the coupled analysis. It was found that a higher horizontal permeability compared with the vertical one causes reduction in the seepage farce acting on the tunnel face.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.191-194
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• 2008

The cavity behind the tunnel lining, caused by overbrake, might be cause a severe instability during tunnel construction. So backfill grouting is essentially required. GPR(Ground penetrating Radar) is widely used to identify the position and size of the cavity and to verify the effect of the backfill grouting. In this study, GPR survey with 450 MHz antenna was implied to access the effect of the backfill grouting before and after the work to the crown part of ○○ tunnel in Seoul respectively. The result of GPR survey conducted before the backfill, was revealed that cavities behind the lining were existed in the areas of 8 spans. Finally, from the GPR survey implied after backfilling, it was turned out that backfill grouting was successfully carried out. Also, GPR survey was ascertained the better contact between lining and rock base at arrangement of bar span.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.5
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• pp.799-812
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• 2017

Backfill grouting and realistic convergence distribution were not properly considered in previous studies on 2D numerical analysis of a shield TBM tunnel. In this study, a modeling method was suggested to cope with this problem by considering a realistic convergence distribution and proper properties of backfill grouting. To this end, the influence of gap parameter and depth of rock cover on volume loss and composed of ground volume loss around tunnel excavation and surface volume loss were analyzed with a single layer of weathered soil. As a result, most of surface settlements were occurred immediately after excavation. Additional, as depth of rock cover and gap parameter increased, the influence range of surface settlement curves obtained from 2D numerical analyses became broader than a suggested theoretical equation. Therefore, it is inferred that gap parameter should be applied based on load distribution ratio and the property of backfill grouting properly considered for the estimation of the precise behavior of a shield TBM tunnel in 2D numerical analysis.