• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.451-468
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• 2020

Aging tunnels with small cross-sections can cause chronic traffic jams. This problem can be solved by widening the tunnel. In general, when the tunnel is expanded, the outer portion of the existing tunnel is excavated through a mechanical or blasting method. Such excavation affects not only the surrounding ground but also the existing tunnel. The application of the pre-cutting method can be a solution to these problems effectively. Therefore, if the widening of tunnel is performed by applying pre-cutting method, analysis of the impact of this method must be performed. In this study, in order to analyze the effect of applying pre-cutting in tunnel widening, numerical analysis is performed at six ground grades, from grade I to weathered rock. The analysis is performed with the expanding lane and the excavation length of pre-cutting as variables. In addition, the analysis is focused on the displacement of crown of the existing tunnel and the enlarged tunnel. As a result, the crown displacement of the enlarged tunnel is confirmed to converge at the same value regardless of the excavation length of the pre-cutting when the tunnel widening is completed. In the case of existing tunnels, uplift of crown occurs within 5 m of the front of the tunnel surface, and the shorter the excavation length of pre-cutting is found to be effective in preventing the occurrence of uplift.

• Tunnel and Underground Space
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• v.33 no.3
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• pp.141-149
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• 2023

Recently, as the demand for urban underground space increases, urban tunnel planning is actively progressing. In particular, the application of the roadheader excavation method, which has favorable applicability to urban tunnel, is increasing. However, it is known that the roadheader excavation method has a limitation in that excavation efficiency for high strength rock with a Uniaxial Compressive Strength (UCS) of 100 MPa or more is lowered. In this study, The pre-cracked method was presented as a method to improve the excavation efficiency of roadheader for high strength rock and its applicability was evaluated. The net cutting rate was evaluated using the Bilgin prediction formula, which can calculate the net cutting rate by considering the UCS and RQD (Rock Quality Designation). It was found that the net cutting rate increased as the RQD decreased under the rock condition with the same UCS. This is judged to increase the excavation efficiency of the roadheader in the jointed high strength rock. Additionally, the field applicability of the pre-cracked method for high strength rock was verified through field tests. It was confirmed that the crack zone was formed around the charging hole, and it is considered that the pre-cracked method can be applied to the high strength rock.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.5
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• pp.22-29
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• 2002

This study was conducted to suggest develop revegetation methods and to classification of cutting-rock slopes revegetation type. The data was collected from pre-experienced data, reports and journal. Also research result was reflected from field research for the conditions of construction, vegetation types and field conditions. As the result of analyze, the factors affecting the plant coverage rates of cutting-rock slopes were period of construction, revegetation methods, slope gradient and slope length. Classification of cutting-rock slopes revegetation type was fourth from material of revegetation measures and spray type. It is recommended to adjust the proposed factor as environment, field condition and characteristic related with revegetation measures on slopes for the presentation of revegetation standard.

• Explosives and Blasting
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• v.23 no.3
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• pp.83-89
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• 2005

It follows in deterioration of the steel frame structure and becomes remodeling and removal. The construction work characteristic, economical efficiency and stability environment characteristic are planned and considered hereafter control plan of the steel frame structure which is deteriorated currently to cutting mettled plentifully sued on gas cutting of H beam. However it will not be able to apply from the explosives demolition which is makes a weak instantaneously and then collapses the building at the time. In this study, shape charge was used for cutting of the H-beam. That is the element testing to estimate explosives demolition for steel frame structure. As a result, it is found for single-side rutting method, both-sides rutting methods by H-beam thickness and pre-rutting process. It confirmed an affix method and an ease characteristic by fixing tool. Also, it is shown that air blasting decreased about 8dB(A) in order to reduce air blasting used by sand box. However, it will be required to reduce air blasting little more because explosives demolition will be done in urban site.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.344-348
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• 2008

During the last few years, the use of Pre-tensioned spun High strength Concrete(PHC) pile has been gradually increased in many construction sites such as super high-rise and large building construction. there is almost no specific code and/or standard described in the specifications to check verticality for Pre-tensioned Spun High Strength Concrete pile installation process. The most commonly used method for the vortical PHC pile installation is a naked-eye measurement or water level measurement conducted by assistant crew in the construction sites. And recent analysis results of the pile cutting work revealed that it frequently makes a lot of cracks which significantly reduce the strength of the pile and is very labor intensive work, thus requiring a large amount of additional time, costs, and efforts. The main objective of the research is to analize problems and to improvement. measure of PHC Pile Construction. The improvement measure present to the main problem with survey and discussion.