• Title/Summary/Keyword: Process of Excavation

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Numerical Study on the Crack-propagation Controlling in Blasting Using Notched Charge Hole (노치 장약공을 이용한 발파균열제어에 관한 수치해석적 연구)

  • Cho, Sang-Ho;Park, Seung-Hwan;Kim, Kwang-Yeom;Nakamura, Yuichi;Kaneko, Katsuhiko
    • 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.

Evaluation of Radon Exposure During Highway Tunnel Construction by New Austrian Tunneling Method (NATM 공법에 의한 고속도로 터널 공사 중 라돈 노출 평가)

  • Ye-Ji Yu;Hyoung-Ryoul Kim;Mo-Yeol Kang;Sangjun Choi
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.33 no.2
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    • pp.115-125
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    • 2023
  • Objectives: This study was conducted to measure the level of radon in the air at a highway tunnel construction site in a gneiss area using the New Austrian Tunneling Method (NATM) and to evaluate exposure levels by occupation. Methods: Radon concentrations in the air were measured using E-PERM at points 300 m, 600 m, and 900 m from the tunnel entrance during the excavation and waterproofing work inside the tunnel. In addition, radon concentrations were measured during external excavation to compare with the inside of the tunnel. Personal exposure levels for major occupations including tunnel workers, construction equipment operators, waterproofers, shotcrete workers, and safety and health managers who participated in the construction were estimated using radon concentration measured in the work process area and working hours by occupation. Results: As a result of a total of 77 radon measurements, the geometric mean (GM) concentration was 71.1 Bq/m3, and the maximum concentration was 127.3 Bq/m3, which was below the indoor air quality criteria. Radon concentration by process decreased in the order of the tunnel excavation process (GM= Bq/m3, GSD=1.2), waterproofing process (GM=73.35 Bq/m3, GSD=1.2), and outside excavating process (GM=45.28 Bq/m3, GSD=1.2). Processes inside the tunnel were significantly higher than outside excavating processes (p<0.05). There was no statistically significant difference in radon concentration measured inside by distance from the tunnel entrance, but the innermost point of the tunnel, 900 m (GM=79.24 Bq/m3, GSD=1.27), measured the highest. Conclusions: The occupation with the highest individual exposure to radon was tunnel worker (64.16 Bq/m3), followed by construction equipment driver (64.04 Bq/m3) and waterproofer (63.13 Bq/m3).

Trenchless Repairing-Reinforcing Process of Underground Pipes with Advanced Composite Materials (신소재 복합재료를 이용한 비굴착 지하매설관 보수-보강공법)

  • 진우석;권재욱;이대길;유애권
    • Composites Research
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    • v.15 no.1
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    • pp.21-31
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    • 2002
  • To overcome the disadvantages of conventional excavation technology various trenchless (or excavation free, or no-dig) repair-reinforcement technologies have been developed and tried. But trenchless technologies so far developed have some drawbacks such as high cost and inconvenience of operation. In this study, a repairing-reinforcing process for underground pipes with glass fiber fabric polymer composites using VARTM (Vacuum Assisted Resin Transfer Molding) has been developed. The developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than those of the conventional trenchless technologies. For the reliable operation of the developed method, a simple method to apply pressure and vacuum to the reinforcement was devised and flexible mold technology was tried. Also, resin filling and cure status during RTM process were monitored with a commercial dielectrometry cure monitoring system, LACOMCURE. From the investigation, it has been found that the developed repairing-reinforcing technology with appropriate process variables and on-line cure monitoring has many advantages over conventional methods.

Japan's excitement over the discovery of Gyeongju Geumgwanchong (Gold Crown Tomb) seen through high school textbooks published in 1922 during Japanese colonial period of Joseon (Korea) - Newly Excavated Artifacts of Gyeongju (濱田耕作: Kosaku Hamada) - (1922년 발행 고등보통학교 교과서를 통해 본 경주 금관총 발견에 따른 일본의 반응 - 경주의 신발굴품(濱田耕作: 하마다 코사쿠) -)

  • YOO, Woo Sik
    • Korean Journal of Heritage: History & Science
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    • v.55 no.1
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    • pp.199-222
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    • 2022
  • It has been 100 years since the excavation of Geumgwanchong (Gold Crown Tomb), a tomb that was accidentally discovered in Noseo-ri, Gyeongju at the end of September 1921 during Japanese colonial rule. Although it is known for its discovery, not only in the Korean Peninsula but also in Asia and beyond, the excavation report was published in Japanese and English by the Government-General of Korea in 1924 and 1928, three years after the excavation. TOMB "KINKANTSUKA" or THE GOLD CROWN TOMB at KEISHU, AND ITS TREASURES) was published as a series of books and picture books. The excavation report was prepared by Kosaku Hamada (濱田耕作), who was a member of the Ruins Investigation Committee of the Japanese Government-General of Korea (later became the President of Kyoto Imperial University, Kyoto, Japan), and Sueji Umehara (梅原末治), who was commissioned to investigate the remains of the Japanese Government-General of Korea. In this paper, the preface was written in July 1922, about half a year after the excavation of tombs, which was much earlier than the official reports, in the 'Korean and Chinese reading book (稿本 高等朝鮮語及漢文讀本 巻五)' by Hamada Kosaku (濱田耕作) for high school students in Korea, which was titled 'New Excavated Artifacts in Gyeongju (慶州의 新發掘品)' with a subtitle '絶大의 發見', a slightly awkward expression in Korean, but it means 'a very big discovery'. The meaning has been introduced as a single unit, emphasizing its significance in terms of the achievements of the excavation of Geumgwanchong, academic and archaeological discoveries, and cultural history in Korean language rather than Japanese language. Since the manuscript was written immediately after the excavation, the excitement as an archaeological researcher at the time of the excavation and expectations for future research can be read as it is. In this paper, I would like to introduce the voice of the excited field leader of the Japanese Government-General of Korea after the excavation of Geumgwanchong in 2022, the 100th anniversary of the writing. In addition, the process from the discovery of the tomb to the preparation of the report was summarized in one chronological table to make it easier to understand the series of flows.

Excavation of Kim Jeong-gi and Korean Archeology (창산 김정기의 유적조사와 한국고고학)

  • Lee, Ju-heun
    • Korean Journal of Heritage: History & Science
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    • v.50 no.4
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    • pp.4-19
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    • 2017
  • Kim Jeong-gi (pen-name: Changsan, Mar. 31, 1930 - Aug. 26, 2015) made a major breakthrough in the history of cultural property excavation in Korea: In 1959, he began to develop an interest in cultural heritage after starting work as an employee of the National Museum of Korea. For about thirty years until he retired from the National Research Institute of Cultural Heritage in 1987, he devoted his life to the excavation of our country's historical relics and artifacts and compiled countless data about them. He continued striving to identify the unique value and meaning of our cultural heritage in universities and excavation organizations until he passed away in 2015. Changsan spearheaded all of Korea's monumental archeological excavations and research. He is widely known at home and abroad as a scholar of Korean archeology, particularly in the early years of its existence as an academic discipline. As such, he has had a considerable influence on the development of Korean archeology. Although his multiple activities and roles are meaningful in terms of the country's archaeological history, there are limits to his contributions nevertheless. The Deoksugung Palace period (1955-1972), when the National Museum of Korea was situated in Deoksugung Palace, is considered to be a time of great significance for Korean archeology, as relics with diverse characteristics were researched during this period. Changsan actively participated in archeological surveys of prehistoric shell mounds and dwellings, conducted surveys of historical relics, measured many historical sites, and took charge of photographing and drawing such relics. He put to good use all the excavation techniques that he had learned in Japan, while his countrywide archaeological surveys are highly regarded in terms of academic history as well. What particularly sets his perspectives apart in archaeological terms is the fact that he raised the possibility of underwater tombs in ancient times, and also coined the term "Haemi Culture" as part of a theory of local culture aimed at furthering understanding of Bronze Age cultures in Korea. His input was simply breathtaking. In 1969, the National Research Institute of Cultural Heritage (NRICH) was founded and Changsan was appointed as its head. Despite the many difficulties he faced in running the institute with limited financial and human resources, he gave everything he had to research and field studies of the brilliant cultural heritages that Korea has preserved for so long. Changsan succeeded in restoring Bulguksa Temple, and followed this up with the successful excavation of the Cheonmachong Tomb and the Hwangnamdaechong Tomb in Gyeongju. He then explored the Hwangnyongsa Temple site, Bunhwangsa Temple, and the Mireuksa Temple site in order to systematically evaluate the Buddhist culture and structures of the Three Kingdoms Period. We can safely say that the large excavation projects that he organized and carried out at that time not only laid the foundations for Korean archeology but also made significant contributions to studies in related fields. Above all, in terms of the developmental process of Korean archeology, the achievements he generated with his exceptional passion during the period are almost too numerous to mention, but they include his systematization of various excavation methods, cultivation of archaeologists, popularization of archeological excavations, formalization of survey records, and promotion of data disclosure. On the other hand, although this "Excavation King" devoted himself to excavations, kept precise records, and paid keen attention to every detail, he failed to overcome the limitations of his era in the process of defining the nature of cultural remains and interpreting historical sites and structures. Despite his many roles in Korean archeology, the fact that he left behind a controversy over the identity of the occupant of the Hwangnamdaechong Tomb remains a sore spot in his otherwise perfect reputation.

Variation of abrasive feed rate with abrasive injection waterjet system process parameters (연마재 투입형 워터젯 시스템의 공정 변수에 따른 연마재 투입량 변화)

  • Joo, Gun-Wook;Oh, Tae-Min;Kim, Hak-Sung;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.17 no.2
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    • pp.141-151
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    • 2015
  • A new rock excavation method using an abrasive injection waterjet system has been developed to enhance the efficiency and reduce the vibration of tunnel excavation. The abrasive feed rate is an important factor for the cutting performance and the economical efficiency of waterjet-based excavation. In this study, various experiments were performed to explore the effects of major process parameters for both the abrasive feed rate and the suction pressure occurring inside the mixing chamber when the abrasives are inhaled. Experimental results reveal that the abrasive feed rate is affected by geometry parameters (abrasive pipe height, length, and tortuosity), abrasive parameters (abrasive particle size), and jet energy parameters (water pressure and water flow rate). In addition, the relation between the cutting performance and the abrasive feed rate was discussed on the basis of the results of an experimental study. The cutting performance can be maximized when the abrasive feed rate is controlled appropriately via careful management of major process parameters.

Economical Analysis and Estimate Method of Possible Working Hours for Marine Rock Excavation Work Regarding the Tide Cycle (조석의 주기를 고려한 해상 암굴착 공사의 경제성 분석 및 작업가능시간 산정 방법에 관한 연구)

  • Kwon, Soon-Boum;Ock, Jong-Ho;Lee, Seung-Hyun
    • Korean Journal of Construction Engineering and Management
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    • v.8 no.5
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    • pp.142-151
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    • 2007
  • The rock excavation work on the sea is planned as underwater process if the elevation of the rock is lower than the M.S.L.(Mean Sea Level). However, in case of West and South sea which are largely different between the rise and fall of the tide, the earth work can be performed on the ground while the work surface is exposed above the sea according to the tide cycle. Thus, it may a good substitute to make up for shortcomings of underwater construction works such as safety problems of workers, loss of efficiency and increasement of construction costs. But the difference between the height of the rock excavation surface and the water surface changed by the tide makes the exposure time of work surface, that is the possible working hours be changed. Also, it may cause the changes of construction cost. Thus, this study analyzes the economical efficiency of the construction method using the difference between the rise and fall of the tide in comparison with the construction method which is performed under the sea, and it also suggests the way to analyze the economical working hours by estimating the possible working hours on the ground. We also try to find out the application possibility of the way like the rock excavation work on the sea using the difference between rise and fall of the tide.

Development of testing apparatus and fundamental study for performance and cutting tool wear of EPB TBM in soft ground (토사지반 EPB TBM의 굴진성능 및 커팅툴 마모량에 관한 실험장비 개발 및 기초연구)

  • Kim, Dae-Young;Kang, Han-Byul;Shin, Young Jin;Jung, Jae-Hoon;Lee, Jae-won
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.2
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    • pp.453-467
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    • 2018
  • The excavation performance and the cutting tool wear prediction of shield TBM are very important issues for design and construction in TBM tunneling. For hard-rock TBMs, CSM and NTNU model have been widely used for prediction of disc cutter wear and penetration rate. But in case of soft-ground TBMs, the wear evaluation and the excavation performance have not been studied in details due to the complexity of the ground behavior and therefore few testing methods have been proposed. In this study, a new soil abrasion and penetration tester (SAPT) that simulates EPB TBM excavation process is introduced which overcomes the drawbacks of the previously developed soil abrasivity testers. Parametric tests for penetration rate, foam mixing ratio, foam concentration were conducted to evaluate influential parameters affecting TBM excavation and also ripper wear was measured in laboratory. The results of artificial soil specimen composed of 70% illite and 30% silica sand showed TBM additives such as foam play a key role in terms of excavation and tool wear.

An elasto-plastic damage constitutive model for jointed rock mass with an application

  • Wang, Hanpeng;Li, Yong;Li, Shucai;Zhang, Qingsong;Liu, Jian
    • Geomechanics and Engineering
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    • v.11 no.1
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    • pp.77-94
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    • 2016
  • A forked tunnel, as a special complicated underground structure, is composed of big-arch tunnel, multi-arch tunnel, neighborhood tunnels and separate tunnels according to the different distances between two separate tunnels. Due to the complicated process of design and construction, surrounding jointed rock mass stability of the big-arch tunnel which belongs to the forked tunnel during excavation is a hot issue that needs special attentions. In this paper, an elasto-plastic damage constitutive model for jointed rock mass is proposed based on the coupling method considering elasto-plastic and damage theories, and the irreversible thermodynamics theory. Based on this elasto-plastic damage constitutive model, a three dimensional elasto-plastic damage finite element code (D-FEM) is implemented using Visual Fortran language, which can numerically simulate the whole excavation process of underground project and perform the structural stability of the surrounding rock mass. Comparing with a popular commercial computer code, three dimensional fast Lagrangian analysis of continua (FLAC3D), this D-FEM has advantages in terms of rapid computing process, element grouping function and providing more material models. After that, FLAC3D and D-FEM are simultaneously used to perform the structural stability analysis of the surrounding rock mass in the forked tunnel considering three different computing schemes. The final numerical results behave almost consistent using both FLAC3D and D-FEM. But from the point of numerically obtained damage softening areas, the numerical results obtained by D-FEM more closely approach the practical behaviors of in-situ surrounding rock mass.

Determining Parameters of Dynamic Fracture Process Analysis(DFPA) Code to Simulate Radial Tensile Cracks in Limestone Blast (석회암 내 방사상 발파균열을 예측하기 위한 동적파괴과정 해석법의 입력물성 결정법에 관한 연구)

  • Kim, Hyon-Soo;Kang, Hyeong-Min;Jung, Sang-Sun;Kim, Seung-Kon;Cho, Sang-Ho
    • Explosives and Blasting
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    • v.31 no.2
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    • pp.6-13
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    • 2013
  • Recently, complaints or environmental problems caused by the noise and dust generated from crusher of the mine and quarry are emerging. Therefore mining facilities such as crushers and mills have been installed in an underground. In order to facilitate crusher equipments in the underground, excavation of large space is required and then the stability of the large space underground structure is an important issue. In this study, the blast experiments, which use a block of the limestone, are performed. Based on the blast experiments, the numerical model was prepared and simulated using dynamic fracture process analysis code(DFPA) with considering the rising time of applied borehole pressure and microscopic tensile strength variation. Comparing the non-dimensional crack length and no-dimensional tensile strength obtained from blast experiments and numerical analyses, the input parameters of DFPA code for predicting a radial tensile crack in limestone blasting were determined.