• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.797-800
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• 2008

The pre-mixed concrete shotcrete, which can pre-bag the shotcrete materials and thus can save considerable labor activity, will be developed through extensive experiments. The proposed pre-mixed High performance Shooting concrete system included hydro-demolition will be verified though field tests in actual repair and rehabilitation construction sites. This research was on developing of the High performance Shooting concrete by evaluation of site application by field test using new automatic Hydro-demolition and Shotcrete equipment.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.527-530
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• 2005

Shotcrete have become a deterioration which is used in the underground such as groundwater and soil in sulfate ion. Sulfate attack on concrete structures in service is not widespread, and the amount of laboratory-based research seems. to be disproportionately large. In this study, immersion test using $Na_2SO_4$ solution($1,2,5\%$) was performed to evalute the resistance of shotcrete. From the results of the immersion test for 112 days of exposure. In order to understand the deterioration mechanism due to seawater attack, test using scanning electron microscopy(SEM) analysis and X-ray diffraction showed that the deterioration mechanism due to sulfate attack in shotcrete.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.622-628
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• 2004

In general, Reinforced Slopes by Shotcrete are difficult to inspect because of stiff Slope and highly Working Area. So the Inspection Techniques are needed by the Non-contact and Non-destructive. On this Study, Appling the safety method to finding the weak zones(cavity area, dampness area, etc.) by using the Infrared Thermal Technique That is detecting the Detail Thermal Difference on the Surface of Reinforced Slopes by Shotcrete.

• 한국터널공학회:학술대회논문집
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• 2005.04a
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• pp.213-224
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• 2005

The safety factor of a tunnel considering the failure of supports is important because the failure of supports might cause the collapse of the tunnel. In the previous studies, shotcrete was modelled as beam elements and the failure of the shotcrete was checked according to the allowable working stress concept. In this study, shotcrete was modelled by both beam elements and continuum (elasto-plastic) elements. Safety factors of tunnels were estimated by two dimensional numerical analysis with varying rock mass class, coefficient of lateral pressure, thickness of shotcrete, rock bolt reinforcement and excavation method. Also the study suggested not only a proper amount of supports but also modelling method.

• 한국터널공학회:학술대회논문집
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• 2005.04a
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• pp.259-261
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• 2005

The needs of improving the performance of wet shotcrete has become one of the most important issues in the tunnel field. The aim of this paper is to research the construction method of reinforced shotcrete using structural polymer fiber which exhibits a high quality in toughness and durability for the support of tunnel.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1162-1167
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• 2004

From the early 1980's, the New Austrian Tunnelling Method (NATM) has been developed as a one of the standard tunneling method in Korea. Owing to the results of many researches, the practical problems of shotcrete has been improved for a last decade. However, the excess amount of rebound still remains one of the critical problems in shotcrete technology. In order to improve for this rebound problem, recently developed cement mineral accelerator has been successfully applied to several NATM tunnels in Korea. An experimental investigation was carried out in order to verify the rebound characteristics of wet-mix Steel Fiber Reinforced Shotcrete (SFRS) with powder types cement mineral accelerator. Mortar setting test, SEM analysis, bonding test under spring water condition and rebound test were conducted. From the result, wet-mix SFRS with cement mineral acelerator exhibited excellent bonding characteristics even spring water condition and less rebound ratio compared to the conventional liquid accelerator.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1517-1521
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• 2009

A variation of pore structure of shotcrete matrix was experimented by Mercury Intrusion Porosimetry, and the relation with compressive strength was also examined. As a result of the Mercury Intrusion Porosimetry(MIP) test, RM-P1 Batch the macropore diameter of the RM-BFS2 and RM-BFS3 Batch than to have a relatively macropore can see a lot of long-term durability performance degradation. Also, K and N Batch the current is applied to the mine if the factors on shotcrete durability performance of the macropore volume of the entire appears to be a long-term durability performance in the fall.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.714-715
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• 2015

Drill and blast method has been most widely used in tunnel excavation, after NATM (New Austrian Tunneling Method) was introduced in 1983. The NATM method utilized mass of shotcrete to secure the bearing capacity of tunnels. Overbreak defined how much larger the actual excavation was than the planned. When it became larger, more shotcrete was required to fill in it Here, payline fixed allowable overbreak, referring to payable amounts of shotcrete. Since owner was not responsible for shotcrete exceeding payline, it was important to properly establish the standards for payline. Although the standards were provided in 'Poom-sam'(standardized quantity per unit), they did not properly reflect the actual conditions for excavation. Thus, this study reviewed existing domestic and foreign standards for overbreak, and estimated overbreak for each type of support using survey data, and finally provided the improvements on the current standards.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.177-184
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• 1997