• 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 Korean Tunnelling and Underground Space Association
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• v.5 no.2
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• pp.209-216
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• 2003

The present with in this country, rock bolt installation, shotcrete, and concrete lining in construction order has become accepted as a general tunnelling method in NATM. On the other hand Unlined tunnelling method, which was developed by many countries near Scandinavian Peninsula with hard rocks comparatively, has recently been introduced all over the world, and numerous studies about that have been being devoted to domestic tunnels. Unlined tunnelling method has been developed on the basis of the permanently unsupported openings, and general 7 requirements for them were suggested by Nick Barton. There are no case record about these conditions for Q-system in this country. Therefore, input parameters for Q-system under these conditions were applied to general road tunnel cross-section and numerical analyses for each condition were executed with UDEC-BB, Distinct Element Method.

• Magazine of korean Tunnelling and Underground Space Association
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• v.23 no.4
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• pp.38-48
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• 2021

최근 국내 건설현장들은 도심지 근접구간에서 발파진동피해를 최소화하기 위하여 전자뇌관을 이용한 미진동 전자발파공법 적용사례가 증가하고 있는 추세이다. 그러나 미진동 전자발파는 무진동 암파쇄 대체공법으로 경제성은 우수하나 시공현장에서 진동을 제어하는 공법으로 1회 굴진장을 1m 이하로 적용하고 있어 시공속도가 저하되는 문제점이 발생하고 있다. 따라서, 미진동 전자발파 수준의 진동제어와 굴착비 절감 및 시공속도를 높일 수 있는 더블데크 발파공법을 연구 및 시험을 수행하였다. 미진동 전자발파와 더블데크 전자발파 비교 시험결과 진동레벨, 발파효율, 파쇄입도, 여굴량 등이 비슷한 수준으로 평가되어 현장 적용시 굴진장 증대로 인한 공사기간 단축 및 시공비 절감이 가능할 것으로 판단되었다.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1994.03a
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• pp.38-51
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• 1994

지하원유비축 기지 저장공동의 원유 유출이나 기화누설을 방지하기 위하여 지하수압을 조절하는 수벽공의 운영이나 공동주위 암반의 그라우팅 공법 설계에 있어서는 공동의 굴착으로 인한 주위 암반의 변형에 따른 투수계수의 변화와 지하수위의 변화에 대한 해석이 대단히 중요하다. 본 연구에서는 순간증압법을 이용한 삼축압축하의 암석의 투수계수 측정을 통하여 변형율과 투수계수와의 관계함수식을 구하였다. (중략)

• Explosives and Blasting
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• v.26 no.1
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• pp.49-55
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• 2008

Mechanical excavation techniques employing tunnel boring machines (TBM) and rock splitters have been proposed to minimize rock damage for tunnel and underground waste repository facilities. Such a mechanical excavation, however, is extremely expensive and not applicable in all cases. For these reasons, controlled blasting using notched charge holes have been suggested to achieve crack growth along specific directions and inhibit growth along other directions. This study introduces a dynamic fracture process analysis code to simulate fracture processes of rock which has a notched charge hole.

• Tunnel and Underground Space
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• v.31 no.1
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• pp.1-9
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• 2021

Recently, the development of underground space has been accelerated with rapid urbanization, and it is significantly important for safe construction to accurately understand the geological conditions of the section when excavating rocks. In this paper, a boring alignment tracking and geological exploration system have been developed to identify the geological conditions beyond the excavation face by utilizing a MSP method that bores a large empty hole to reduce blast-induced vibration. The major advantage of the proposed exploration system is that we can obtain the ground condition of 50 m ahead of the excavation face through exploration along blast cut-holes drilled for the NATM tunnel construction. In addition, we introduce several case histories regarding the assessment of the geological conditions beyond the tunnel face by monitoring the inside of large empty holes using the proposed hole exploration system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.131-138
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• 2012

This paper aims to present accurately analytical modeling method for underpinning using uncertainty reduction, obtained from comparison between numerical analysis and Site measuring data during construction and service stages. Combination of various conditions should be considered for using numerical analysis to predict the behavior of the structure accurately, even though complexly considered the conditions, real construction should be secured the stability by applying the actual instrument measurement data because predicted results are including the considerable uncertainty. In order to secure the stability during construction, the real time instrument measurements together with numerical analysis results performed before construction state are complementary used actively. From the results of this study, the significant settlements are occurred not only in underpass structure of adjacent excavation area but also in the permanent steel pipe structures were analyzed. From the site measurement results of underpass settlement, the settlements are occurred in every stages of excavation, furthermore observed tendency is asymmetrical excavation patterns are settled more than symmetrical excavation patterns. The essential consideration points for numerical analysis are construction sequence, the direction of the existing facilities, the methods of elements modeling, the applied factors for nature of material and different results would be occurred depending upon inputting the above factors.

• Geotechnical Engineering
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• v.12 no.5
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• pp.5-16
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• 1996

When braced excavation with temporary retaining wall installation, is performed in loose sand with high ground water level boiling may be induced and considerable damage on the excavation works and structures in the vicinity can take place. Recently, for the purpose of reinforcement of ground and cut-off of ground water behind the temporary retaining wall, high pressure jet grouting is widely used. The purpose of this paper is to investigate the effects of jet grouting on ground reinforcement and cut -off of the ground water behind temporary retaining walls for braced excavation. A series of both laboratory and field tests has been performed. The test results show that high pressure jet grouting has sufficient effects on reinforcement of stiffness of ground and retaining wall. The permeability of the improved ground was 10-f_ 10-3cm l s smaller than those of the original ground. Therefore, the effect on cut off of ground water behind temporary retaining walls could be improved by high pressure jet grouting method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.589-604
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• 2021

Waterjets for rocks have various advantages of the non-contact and eco-friendly excavation using only water and abrasive. To overcome the problems (e.g., dust and noise occurrence) of the conventional drilling methods, waterjet excavation methods are broadly used. It is advantageous to operate a couple of nozzles in order to increase the waterjet excavation efficiency. When multiple nozzles are used, it is essential to analyze the excavation performance and shape according to the nozzle operation method. In this study, nozzle angle, horizontal distance between nozzles, and standoff distance were defined as nozzle operating parameters and the excavation performance and shape were analyzed. As a result of the experiment, when the nozzle angle and standoff distance are increased, the excavation depth is decreased and the effective depth tends to be increased. In addition, based on the experimental results, the excavation shape criteria required for nozzle insertion were proposed and optimal nozzle operating parameters were derived according to the criteria. This study result is expected to be used as useful basic research in the future development of multiple waterjet nozzles for rock drilling.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.517-520
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• 2010

BIM 설계시 의무사항으로 포함되어 있는 원지형과 암층별 지층, 흙막이 공법 중 CIP(Cast in Place Pile)공법, 구조물 형상을 3차원 정보 모델로 생성하고, 모델을 통해 정확한 2D 도면의 생성, 각 공정간의 간섭검토, 암층별 토공량 및 흙막이의 수량을 산출하였다. 최종 설계안을 도출하기 위해 3차원 기법이 설계 초기에 도입되어 반복적인 노력과 시간을 최소화하여 많은 설계대안을 제시하도록 하였으며, 정확한 설계결과를 얻기 위해, 2D 설계와 3D 설계를 병행 수행함과 동시에 이 과정과 결과를 비교하여 3차원 모델의 효과를 검증하였다.