• 지반과기술
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• v.6 no.3
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• pp.54-54
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• 2009

• Environmental engineer
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• v.19 s.200
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• pp.46-48
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• 2003

• Tunnel and Underground Space
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• v.24 no.5
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• pp.373-385
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• 2014

Hydraulic filling methods are widely applied to suppress the land subsidence recently. But the research on high-efficiency hydraulic filling to protect the land subsidence is rare. In this study, field experiments to improve the efficiency of the hydraulic filling method are performed by changing the property, specification of the filling material and injection pipe. The filling amounts using vertical injection pipe, reducing tee (${\phi}100mm$) pipe, reducing tee (${\phi}80mm$) pipe and reducing tee (${\phi}50mm$) pipe showed 28.84 ton, 42.62 ton, 53.33 ton, and 63.33 ton respectively. The filling rates using reducing tee (${\phi}100mm$) pipe, reducing tee (${\phi}80mm$) pipe and reducing tee (${\phi}50mm$) pipe showed 47.8%, 84.9% and 119.6% respectively. Filling efficiency can be incresed by using reducing tee. This study shows that simply changing the type of injection pipe is expected to increase the hydraulic filling rate.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.97-107
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• 2017

Recently, there have been a lot of incidents related to ground sinks in urban areas, but restoration work is complicated and inconvenience due to on-site control, and particularly, grouting and soil filling are generally applied as recovery measures, but when the grouting or the soil filling is carried out, material segregation phenomenon occurs in the ground or a lot of restoration amount is often required, depending on the state of sinks and the existence of groundwater under the ground and the soil can be lost due to the flow of the ground water, and thus the purpose of this study is to develop a pouch-type filler applied to a trenchless method for emergency reinforcement of the ground sinks with the aim of quick recovery of the ground sink in urban areas, and as a result, it was confirmed that compression strength and the expansion ratio were different according to the temperature of ground water and the compression strength and the expansion ratio could be controlled by mixing alumina powder.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.105-106
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• 2018

Cracks are typical defects that occur in concrete structures. When cracks occur in the structure, durability reduction, concrete neutralization, and steel corrosion cause functional safety problems. In order to prevent such cracks, surface repair method is performed for cracks smaller than 0.3 mm and rechargeable method is performed for cracks larger than 0.3 mm. However, even if it is applied by the surface repair method at less than 0.3 mm, re-leakage cracks continue to occur. Recently, the Supreme Court ruled that the rechargeable method should be applied to cracks less than 0.3mm in order to reduce the occurrence of defects. However, it was considered that the repair fees were too high relative to the observed defect rate, resulting in a necessitation of modifying the existing construction analysis administration standards. This study analyzes the differences in the subjective views on the durability degradation with regards to surface repair methods in concrete structures.

• Tunnel and Underground Space
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• v.22 no.6
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• pp.403-411
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• 2012

In recent, the using of the hydraulic filling method has increased on the underground reinforcement of the abandoned mine in Korea, however it is the lack of research on the efficient filling method. In this study, tank model tests and field tests were conducted for development of tip device for filling efficiency improvements on the hydraulic filling method. In tank model experiments, the filling efficiency was evaluated according to the form and angle of the nozzle on tip device in the same condition. Then tip device model designed by tank model tests was applied to the field experiment. As a result, the amount of filling of nozzle $90^{\circ}$ tube is increased by approximately 18% compared to the common vertical injection pipe. The angle of repose was $30.82^{\circ}$. Filling hole spacing in the field is usually designed from 5m up to 10m assumed to be $40^{\circ}$ of the angle of repose. According to the results of this study, it is possible that the filling hole spacing expands at least 10m up to 15m applied to be $30^{\circ}{\sim}35^{\circ}$ of the angle of repose. Therefore, it is expected to be economical and efficient mine filling.

• Journal of the Korea Concrete Institute
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• v.13 no.5
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• pp.516-524
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• 2001

Among many connection methods of reinforcing bar, the grout-filled splice sleeve system is very effective method of precast concrete construction due to its superior construction efficiency, such as large allowable limit to arrangement of reinforcing bars, good application of large sized reinforcing bars. In this study, totally 20 full-sited specimens were made and tested under monotonic and cyclic loading in order to extend the usage range of grout-filled splice sleeve system. The experimental variables adopted in this study are size of reinforcing bars embedded in upper and lower part of sleeve and compressive strength of filled mortar etc. After test was performed, the results were compared and analyzed with respect to previous test of author. Following main conclusions are obtained : 1) The structural performance of splice sleeve system is improved with increasing compressive strength of filled mortar. And also it was verified that the splice sleeve system with over 700 kgf/㎠ mortar compressive strength and over 6.54 development length of reinforcing bar retains the structural performance of over A class(AIJ Criteria). 2) In the case of using different size of reinforcing bars embedded in upper and lower part of sleeve, the result show that splice sleeve matching with large sized reinforcing bar must be used. And also up to 2 level smaller size of reinforcing bar compared to large reinforcing bar embedded in sleeve can be used.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.102-109
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• 2003

The grouted splice steeve has been applied widely due to its superior construction efficiency, such as the unnecessity of post concrete and the large allowable limit to the arrangement of reinforcing bars. However, studies on grout-filled splice steeve still have not been sufficiently peformed. The purpose of this study is to investigate the confining effect of mortar grouted splice sleeve on reinforcing bar, known to strengthen the bond capacity between grout mortar and reinforcing bar. To accomplish this objective, totally 6 full-sized specimens were made and tested under monotonic loading. Each specimens were equipped with strain gauges at the 12 location of sleeve and reinforcing bar. The experimental variables adopted in this study are embedment length and size of reinforcing bars. Following conclusions are obtained; 1) Under ultimate strength condition, the confining pressure of grouted splice sleeve calculated from measured tangential and axial strain of the sleeve is over $200{\sim}300kgf/{cm}^2$ at any location of sleeve and improved with reduction in embedment length of reinforcing bar. 2) Untrauer and Henry's equation which describe bond strength of mortar as a function of its compressive strength and confining pressure, predicted the measured bond capacity of this test within the 5% limits.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.880-894
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• 2010

The Grout injected precast pile is widely used in rapid-transit railway bridge recently. The existing portland cement of well used filling at injected precast method that with low strength and environmental pollution, unstable in which ground water contamination by cement flow out, ground relaxation by water down, decrease of horizontality resistance and durability and load transfer divide etc. In particular, as in rapid-transit railway bridge need to secure safety from different angle with vibration of high speed train, horizontal force when train stop and earthquake. Works of foundation construction consider to requirements of the times to coal yard green growth. Together, new green foundation method for possible economics and securing of reduce the term of works are material to developments. Therefore, we carried out study that it is using and development new concept environment - friendly filling include durability and earthquake resistance, for secure safety and minimize environment pollution. To achieve this, we carried out difference tests that new green fillings of underwater concrete, high liquidity, high viscosity, early stiffness as compared to existing portland cement fillings. As results, new green filling have outstanding application at precast pile method and micropile construction method with vertical bearing capacity, horizontal bearing capacity and many case. From now on we will be looking forward to development of new environment-friendly foundation method from various further studies.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.5
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• pp.577-585
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• 2023

Lateral torsional buckling causessafety accidentssuch as collapse accidents during erection. Therefore, anaccurate safety designshould be conducted. Lateral torsional buckling canbe prevented by reinforcing the end orreducing the unbraced length. The method ofreducing the unbraced length by installing a crossframe has high material and installation costs and low maintenance performance.In addition, structuralsafety may be deteriorated due to cracks. The end reinforcement method using Concrete Filled Half Pipe Stiffeneris a method ofreinforcing the end of a plate girder using a stiffenerin the form of a semi-circular column. This method increasesthewarping strength ofthe girder and increasesthe lateral torsional buckling strength.In thisstudy, the effect ofincreasing the warping strengthof plate girders with concrete filled half pipe stiffeners was confirmed. To verify the effect, the results ofthe designequationand the finite element analysis were compared and verified through a experiment. As a result, the plate girderwithCFHPS increased thewarping strengthand confirmed that the lateral torsional buckling strength was increased.