• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.283-286
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• 2007

지반을 보강 또는 지하수를 차단하기 위해 실시되는 그라우팅과 같은 공법이 제대로 효과를 발휘하기 위해서는 bulging 또는 sheet 형태의 그라우트체 형상의 조절이 필수적이다. 본 논문에서는 이러한 그라우트체 형상에 영향을 끼치는 인자를 찾기 위해 포화된 사질토지반에서의 그라우트 실험을 다수 실시하였다. 그라우트의 주입속도와 점성의 크기, 사질토의 상대밀도와 입도크기의 인자를 사용하여 실험을 사용한 결과, 비교적 느린 주입속도와 작은 상대밀도, 그라우트의 점성과 입자가 클수록 bulging 형상의 그라우트체가 형성이 되었다. 이와는 반대로 빠른 주입속도와 높은 상대밀도, 그리고 그라우트의 점성과 흙 입자가 작을수록 sheet 형상의 그라우트체가 형성이 됨을 확인하였다.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.635-643
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• 2004

In this study, the tensile strength of 321 full-sized grout-filled splice steeve specimens were compared and analyzed in order to afford the data for a reasonable and economical design of this system. The experimental variables analyzed in this study were embedment length of reinforcing bars, compressive strength of grout, sleeve geometry, loading pattern and final failure mode of specimen. Following main conclusions are obtained : 1) The strength of grout-filled splice sleeve tends to be improved with increasing compressive strength of grout and embedment length of reinforcing bars. Specially this tendency appears apparent in specimens of bond failure rather than rebar failure. 2) The results of this study show that the sleeve geometry have influence on the bond strength of grout-filled splice sleeve. 3) The grout-filled splice sleeve of bond failure don't show the difference of tensile strength according to size of rebar. 4) It is verified that the tensile strength required in ACI and domestic code is retained either when the compressive strength of grout over 70 MPa is used with embedment length of reinforcing bars over 4.5d or when the compressive strength of grout over 80 MPa is used with embedment length of rebars over 3.9d. 5) It is verified that the tensile strength required in AIJ code is retained in case when the embedment length of reinforcing bars is 0.8 times the rebar diameter longer than in ACI code.

• Journal of the Korean Geotechnical Society
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• v.32 no.10
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• pp.67-79
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• 2016

Waveform micropile is an advanced construction method that combined the concept of conventional micropile with jet grouting method. This new form of micropile was developed to improve frictional resistance, which consequently leads to achieving higher bearing capacity and cost efficiency. Two field tests were conducted to examine the field applicability as well as to verify the effects of bearing capacity enhancement. In particular, waveform micropile construction using jet grouting method was performed to evaluate the viability of waveform micropile installation. After testing, the surrounding ground was excavated to check the accomplishment on the shape of waveform micropile. The result showed that waveform micropile can be installed by adjusting the grouting time and pressure. In the loading tests, waveform micropile's bearing capacity increased by 1.4 to 2.3 times depending on their shapes when compared with conventional micropile. Overall results clearly demonstrated that waveform micropile is an enhanced construction method that can improve bearing capacity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.19-26
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• 2024

In this study, the compressive behavior of a 1/12.5 scale model of a wind tower support structure connection was experimentally analyzed. A high-performance cementitious grout with a compressive strength of 140 MPa was used to fill the connection, and experiments were conducted with shear key spacing, the shape, and connection length as variables. When the number of shear keys in the connection is the same, the smaller the spacing of the shear keys than the length of the connection, the higher the shear strength, and for the same spacing and connection length, the higher the height of the shear keys, the higher the strength. In addition, it was found that the strength showed a linear behaviour until the connection slip reached 1.0 mm, and it reached the maximum strength at 7.0 mm connection slip showing a non-linear behaviour as the load increased. It was found that the failure mode changed from interfacial shear failure to grout failure as the strength increased according to the shape and spacing of the shear key, and brittle failure did not occur due to steel fibers.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.165-173
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• 2013

Splice sleeves for HD25 and HD32 rebars with yield strength 500 MPa were studied experimentally and analytically. The shapes of sleeve was examined with nonlinear finite element analyses. A total of 18 specimens were tested with test variables of rebar types, sleeve lengths, mortar compressive strengths, and rebar development lengths. Three identical specimens per each variable were tested in order to prevent any test errors. After tests, numerical studies with a nonlinear finite element method were conducted to evaluate the test results. Experimental studies with 18 specimens showed that the sleeves of this study satisfies the code requirement. It was found that the strength of mortar and the bar development length within the sleeves did not affect to the load-carrying capacity of sleeves.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.1049-1057
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• 2016

The waveform micropile is a type of foundation that has a single or multiple shear keys on the pile shaft, and it is constructed through a jet grouting method as a way to increase the shaft resistance of the bonded area between the pile and the soil. In this paper, a geotechnical centrifuge test was performed to study the axial performance of the waveform micropile from other models. The six test models consisted of three waveform micropiles with a single shear key at three different depths, a waveform micropile with multiple shear keys, a conventional micropile, and a jet grouting micropile. Based on the test results, it was clearly shown that the waveform micropile increased in its bearing capacity compared to the other models without the shear key. Additionally, it was observed that the confining pressure for the location of a shear key is directly related to the increase of the bearing capacity.

• Magazine of the Korea Concrete Institute
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• v.8 no.4
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• pp.181-189
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• 1996

It is well-known that the hearing strength in vertical joints of precast concrete large panel system is affected by grout compressive strength angle of shear key and bearing area. 21 vertical joint specimens were tested to investigate the effects of these parameters The analysis of test results shows that : 1. The higher be grout compressive strength, the higher will shear strength be. And the bearing strength does not so increase in proportion of bearing area. 2. The shear key with the angle of $20^{\circ}$shows the highest bearing strength among three angle variables of $20^{\circ}$, $25^{\circ}$, $30^{\circ}$.

• Journal of the Korean GEO-environmental Society
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• v.18 no.7
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• pp.13-20
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• 2017

Soil nailing is ground reinforcement method using the shear strength of ground and the pullout shear resistance force of nail. It is mainly used for reinforcement of cut slopes, earth retaining structures and retaining walls, etc. It may be designed considering the pullout resistance of nail in the case of earth retaining structure and retaining wall, but it should be designed considering not only pullout resistance but also shear and bending resistance in the case of slope. However, conservative designs considering only pullout resistance are being done and most of the studies are about increasing pullout resistance by improving of material, shape and construction method of nail. Actually, Shear bending deformations occur centering on the active surface in ground reinforced with the nail. The grout with relatively low strength is destroyed and separated from the reinforcing material. As a result, the ground is collapsed while reducing the frictional resistance rapidly. Therefore, it is necessary to develop the method to increase the shear resistance while preventing separation of nail and grout body. In this study, an experimental study was conducted on new soil nailing method which can increase shear resistance by forming protrusions through pressurized grouting after installing a packer on the outside of deformed bar.