• International Journal of Safety
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• v.8 no.2
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• pp.20-25
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• 2009

In this study, an experiment in the field was performed to analyze the mechanical properties and the influence of steel fiber and silica fume on the rebound ratios of shotcrete. The experimental parameters which are the reinforcing methods (steel fiber, wire mesh), steel fiber contents (0.0%, 0.5%, 0.75%, 1.0%), silica fume contents (0.0%, 10.0%), layer thickness (60 mm, 80 mm, 100 mm), and the placing parts (sidewall, shoulder, crown) were chosen. From the mechanical test, it was found that the flexural strength and toughness is significantly improved by the steel fiber and/or silica fume. According to the results for the side wall in this test, the larger the fiber contents are in case of steel fiber reinforced shotcrete, the less the rebound ratios are within the range of 20-35%, compared to the wire mesh reinforced shotcrte. And also, the reduced rebound ratios were very larger in using steel fiber reinforced shotcrete with silica fume content of 10%, and these results are true of the shoulder and the crown. respectively.

• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.122-129
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• 1998

A field experiment was performed to analyze the properties of SFRS(steel fiber reinforced shotcrete) against WMRS(wire mesh reinforced shotcrete) with some experimental parameters. The parameters were reinforcing methods(steel fiber and wire mesh), steel fiber contents(0.5%, 0.75%, and 1.0%), silica fume contents(0.0% and 10.0%), spraying thicknesses of layer(10㎝, 8㎝, and 6㎝), and spraying parts(side wall, shoulder, and crown). According to the analyzed results, the mechanical properties of SFRS such as compressive strength, flexural strength, and load-carrying capacity after cracks were improved. And the economic evaluation was also performed on the basis of the required thickness of the layer and other researcher's results for rebound ratios. From the results of this tests, it is found that the traditional WMRS may be substituted by the SFRS in the viewpoint of the economic evaluation as well as the mechanical properties. In additions, the silica fume, even if it is very expensive, can significantly improve the mechanical properties of the shotcrete regardless of mixing with or without the steel fiber.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.2
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• pp.83-96
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• 2011

Currently, the commonly used tunneling method in Korea is NATM (New Austrian Tunneling Method). This method uses the rock bolt, shotcrete, and supporting system to maintain the strength of original soil and ensures the stability of tunnel by stabilizing the soil using the original strength of the soil in maximum after the excavation. In past years, wire-mesh reinforced shotcrete was common ones but currently steel-fiber reinforced shotcrete is being widely used for the tunnel construction site in Korea to save construction time with the advanced construction technology. The results further indicate that needs for the establishment of not only the specifications for shotcrete but the strengthening methods for the under reinforced shotcrete sections. Therefore, this study deals with the development of a new steel-fiber to ensure the stability of tunnels that are under reinforced with steel-fibers and to overcome the shortcomings of conventional method.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.429-434
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• 1994

In this study, an experiment in the field was performed to analyze the variations of rebound ratios of SFRS with silica fume after fabricating the panels and placing the plain concrete of simulting a base rock with thickness 7cm. And the experimental parameters which are the reinforcing methods(steel fiber, wire mesh), steel fiber contents(0.0%, 0.5%, 0.75%, 1.0%), silica fume contents(0.0%, 10.0%), and the three parts(lower, middle, upper part) were chosen. According to the results of the lower part in this test, the larger the fiber contents are in case of steel fiber reinforced shotcrete, the less the rebound ratios are within the range of 20~35%, compared to the wire-mesh reinforced shotcrete with silica fume content of 10%, and these results are true of the middle and upper part, respectively. In addition, the four-stage phenomena of the rebound of SFRS were estimated on the base of a series of the test results.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.125-133
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• 1998

In this study, an experiment in the field was performed to analyze the influence of steel fiber and silica fume on the rebound ratios of shotcrete. The experimental parameters which are the reinforcing methods(steel fiber, wire mesh), steel fiber contents(0.0%, 0.5%. 0.75%, 1.0%), silica fume contents(0.0%, 10.0%), and the three placing parts(side wall, shoulder, crown) were chosun. According to the results for the side wall in this test, the larger the fiber contents are in case of steel fiber reinforced shotcrete, the less the rebound ratios are within the range of 20~35%, compared to the wire mesh reinforced shotcrte. And also, the reduced rebound ratios were vary larger in using steel fiber reinforced shotcrete with silica fume content of 10%, and these results are true of the shoulder and the crown, respectively. In addition, the four-stage phenomenon for the rebound of the SFRS were estimated in the view of the co-action between steel fiber and coarse aggregate based upon the existing two-stage analysis method.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.209-220
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• 1999

This paper is aimed to evaluate the effectiveness of flexural toughness of slab panel structures($60{\times}60{\times}10$) reinforced by steel fiber instead of wire mesh. Steel fiber used in this study is double hooked Dramix type fiber. And the fiber length is 60mm, diameter is 0.8mm, Various assessment methods of toughness index are used to estimate the proper effectiveness. In this experimental study, we find that Johnston, JCI-SF4 and EFNARC method are more effective to assess the flexural toughness of slab panels than the others. And the steel fiber is very effective alternative material to reinforce slab panel structures instead of wire mesh. Fiber volume fraction of 0.5~0.75% is more useful than the others in enhancing the post-peak energy absorption and toughness index by Johnston's $I_{5.5}$ assessment method. And the slab panels reinforcing with steel fiber are more resistant to crack propagation than wire mesh reinforcing slabs.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.103-112
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• 2019

This study proposes a system to control the bulging phenomenon occurring in the reinforced earth retaining wall and to evaluate the reliability of the system by field experiment. In this study, drainage facilities were not installed in order to induce reinforcement earth retaining wall bulging, and the bulging was induced by rainfall. The induced bulging displacement exceeded the horizontal displacement criterion during the construction of FHWA. The retaining wall block was drilled and grouting was performed by inserting the nail into the drilling hole. The wire mesh is installed on the reinforcing surface and the head of the nail is connected horizontally so that the blocks of the reinforcing earth retaining wall can be supported with each other. In order to protect the reinforcements, the reinforcement surface was closed with shotcrete and a measuring device was installed to detect the progress of the displacement. After the reinforcement, the bulging were not found to progress any more, confirming the reliability of the system.