• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.545-552
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• 2008

To insure the quality and safety of ground anchors, pull-out test of anchor has to be done. In the individually controlled pull-out test system, pull-out device is used to introduce the same pull-out force to individual tendon that has a different length and a deflection. That is, that device has a separate pull-out oil jack to each tendon, thus the pull-out length of each jack is not the same, but that device introduces each tendon to the same pull-out force. In this study, the in-situ pull-out tests for the compression anchors were performed and its test results were analysed and compared to the results of center hole pull-out tests. In the case of pulling out each tendon using the individually controlled pull-out test device, the pull-out forces were distributed to a individual tendon. That device is excellent one that can solve the cause of unequal pull-out forces of each tendon appearing in the manufacture process and construction of anchors, and unequal pull-out forces due to the deferent length.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.167-174
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• 1999

A Land slide in Granitic Gneiss weathered soil was stabilized successfully with soil nailing using 929mm steel bar. To understand the behavior of load transfer between soil and nail, in-situ pdl-out tests were carried out. The strains of steel bars were measured using strain gauges during pull-out tests. Forces-strain data from laboratory tension tests on steel bar and grouted steel bar were examined to compare with those of the pull-out tests. Comparisons were made between the pull-out test results and laboratory test result to understand load transfer mechanism.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.127-134
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• 2000

Soil nailing is in-situ ground improvement technique of reinforcing soils using passive inclusions for the purpose of slope stability. Also soil nailing, in general, was used and studied as a reinforcement technique at cut slope, but this paper presents the results of study for soil nailing application as a reinforcement technique at the banking over slided slope. In-situ pull-out tests of nails, instrumented with strain gauges, were performed to investigate the maximum pull-out load and to calculate the unit side resistance in each different layer. And the apparent average unit side resistance of this study was compared with that of other sites installed at cut slope.

• Tunnel and Underground Space
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• v.20 no.5
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• pp.332-343
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• 2010

This study aims to evaluate the supporting effect of a spiral bolt that is superior to a rock bolt in terms of constructability, stability, environmental and economic aspects as a support system. This study thus analyzed the mechanical properties of a rock bolt which is widely used as a support and a spiral bolt. In addition, laboratory pull-out tests were conducted for the evaluation of properties of the supports such as displacement, pull-out load, confining pressure etc. Moreover, the differences between a rock bolt and a spiral bolt were drawn by comparing the two results of laboratory pull-out tests and in-situ pull-out tests. Then, the differences of the supporting effect of the two supports were analysed by comparing the results of the two pull-out tests with a numerical analysis using FLAC3D.

• Explosives and Blasting
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• v.29 no.1
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• pp.10-16
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• 2011

To make large slopes or rock structures stable, supporting systems, such as anchor bolt, rock bolt and spiral bolt which are developed recently, are commonly used. In this study, in-situ pull-out tests were carried out to compare the characteristics of rock bolt that is most widely used with ones of spiral bolt that is newly developed. Re-pull-out test for the spiral bolt in which loading and unloading cycles are repeated three times showed that the maximum pull-out load is almost constant irrespective of the number of loading cycles, which may be due to no failure between spiral bolt and filler. On the other hand, the maximum pull-out load for the conventional rock bolt decreases with the number of loading cycles due to the partial failure between rock bolt and filler.

• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.5-19
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• 2018

The characteristics of the skin shear stress distribution for the fixed length of the ground anchor are extremely nonlinear and the engineering mechanisms are complex relatively. So it is difficult to design the anchors simulating the actual behavior by considering various soil conditions and nonlinear behavior. Due to these limits, constant skin shear stress distributions for the whole fixed length of the ground anchor are usually assumed in the design for the sake of convenience. In this study, to assess the pull-out behavior of the tension-type ground anchors, the in-situ pull-out tests in weathered-soil conditions were carried out. Based on the test results, the skin shear behaviors for the fixed length of tension-type ground anchors were established and the multi-linear slip shear model predicting this behavior and an analytical technique applying this model were proposed. From the similarity between the results of the in-situ pull-out tests and those of the analytical technique, the applicability and availability of the multi-linear slip shear model and the proposed analytical technique were verified. The maximum shear stress was developed at the start point of the fixed length acting with the smaller load than the maximum pull-out load but the minimum shear stress was developed at the start point of the fixed length and the maximum shear stress was developed at the point apart from the start point of the fixed length after the maximum pull-out load.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.3-10
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• 1999

There is an increasing demand for using rock anchors as foundations in many geotechnical engineering structures such as transmission towers, dams, etc. For investigate the behavior and strength of rock anchors, in-situ pull-out tests were carried out. From the tests, various forms of failure of rock anchors were observed. Ultimate capacity of each failure modes of 1) Tendon failure, 2) Interface failure(tendon-grout interface, sheath-grout interface and grout-rock interface), 3) Combined interface failure, was obtained by varying the parameters such as diameter and length of tendon, grout strength, and quality of rock.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.320-329
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• 2005

The use of diverse methods for the retaining system has been continuously increased in order to maintain the stability during excavation. However, ground anchor system occasionally may have the restriction in urban excavation sites nearby the existing structures because of space limitation. In this case, soil nailing system with relatively short length of nails could be efficiently useful as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in excavating the zone of weak soils or nearby the existing structures. Therefore, applying the pretension force to the soil nails then could play important roles to reduce deformations mainly in an upper part of the nailed-soil excavation system as well as to improve the local slope stability. In this study, a newly modified soil nailing technology named as the PSN(Pretention Soil Nailing) is developed to reduce both facing displacements and ground surface settlements during top-down excavation process as well as to increase the global slope stability. Up to now, the PSN system has been investigated mainly focusing on an establishment of the design procedure. In the present study, the field tests including pull-out tests were fulfilled to investigate the behavior of characteristics for PSN system. All results of tests were also analyzed to provide a fundamental and efficient design.

• Tunnel and Underground Space
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• v.25 no.3
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• pp.264-274
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• 2015

In this study, the applicability of geotextile mesh soil nails on slopes was evaluated by numerical analysis to reduce environmental problems which a general soil nailing might produce and to improve its economical efficiency and construction convenience. To this end, in situ pull-out tests were conducted for both general soil nail and geotextile mesh soil nail and their pull-out characteristics were analyzed. Also, finite difference method was used to verify the suitability of numerical simulation. Parameters for nail and ground conditions were selected and sensitivity analysis was performed for the evaluation of slope stability. In addition, analysis was performed by limit equilibrium method which is widely used for slope stability analysis in practice. As a result, if the nail diameter was same, there is no big difference between geotextile mesh soil nails and general soil nails in terms of slope stability. Therefore it can be expected that geotextile mesh soil nails could be effective for slope reinforcement since they could keep a slope as stable as general soil nails and give better economical efficiency and construction convenience than general soil nails.

• Composites Research
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• v.33 no.6
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• pp.415-420
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• 2020

The interfacial properties in carbon fiber composites, which control the overall mechanical properties of the composites, are very important. Effective interface enhancement work is conducted on the modification of the carbon fiber surface with carbon nanotubes (CNTs). Nonetheless, most surface modifications methods do have their own drawbacks such as high temperatures with a range of 600~1000℃, which should be implemented for CNT growth on carbon fibers that can cause carbon fiber damages affecting deterioration of composites properties. This study includes the use of in-situ interfacial polymerization of polyamide 610/CNT to fabricate the carbon fiber composites. The process is very fast and continuous and can disperse CNTs with random orientation in the interface resulting in enhanced interfacial properties. Scanning electron microscopy was conducted to investigate the CNT dispersion and composites morphology, and the thermal stability of the composites was analyzed via thermogravimetric analysis. In addition, fiber pull-out tests were used to assess interfacial strength between fiber and matrix.