• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.5C
• /
• pp.231-238
• /
• 2012

The rockbolt functions as a main support, which restricts enlargement of the plasticity area and increases stability in the original ground around tunnels, and prevents a second deformation of an excavated surface by supplementing vulnerability arising from opening of the excavated surface. System bolting is generally applied if ground conditions are bad. System bolting is generally installed perpendicular to the excavation direction in every span. If a place is narrow, or it is difficult to insert bolts due to construction conditions, it may be connected and used with short bolts, or installed obliquely. In this study, laboratory model tests were performed to analyze the effect of the ground being reinforced by inclined bolts, based on a bending theory that assumes that the reinforced ground is a simple beam. In all test cases, deflections and vertical earth pressures induced by overburden soil pressure were measured. Total of 99 model tests were carried out, by changing the installation angle of bolts, lateral and longitudinal distance of bolts, and soil height. The model test results indicated that when the installation angle of bolts was less than $75^{\circ}$, deflections of model beams tended to increase rapidly. Also, the relaxed load that was calculated by earth pressure was rapidly increased when the installation angle of bolts was less than $75^{\circ}$. However, the optimum installation angle of inclined bolts was judged to be in the range of $90^{\circ}{\sim}75^{\circ}$. Also, as might be expected, the reinforcement effect of bolts was increased when the longitudinal and lateral distance of bolts was decreased.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.4
• /
• pp.651-668
• /
• 2017

For initial stability of the tunnel, the primary support, Shotcrete and rockbolt shall be placed in the most appropriate time. This is because the role of such support plays a vital role in long-term and short-term tunnel stability. In this study, the rock bolt is an important supporting system that receives the external pressure generated by the stress relaxation during tunnel excavation as axial force and transmits it to the shotcrete on the tunnel excavation surface. Until now, most of the materials of rock bolts have been used in the field, but there have been many problems such as uncertain quality of Chinese materials entering the market, poor packing due to falling down of rock bolts when filled with mortar, and corrosion due to water. Therefore, in this study, we have developed a high strength steel pipe rock bolt using Autobeam material to solve and improve various problems of existing rock bolts. In order to evaluate the performance of the developed bolt, field tests were carried out and the existing mortar filler in order to improve the performance of the rock bolt, the design and construction criteria were studied and the results were included in this paper.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.22 no.5
• /
• pp.543-561
• /
• 2020

This paper is the result of the study on the effect of the support structure of the tunnel steel rib. In tunnel excavation, the top and bottom half excavation methods result in subsidence of steel rib reinforcement due to insufficient support of steel rib reinforcement when the ground is poor after excavation. The foundation of the steel rib installed in the upper half excavates the bottom part of the base, causing the subsidence to occur due to various effects such as internal load and lateral pressure. As a result, the tunnel is difficult to maintain and its safety is problematic. To solve these problems, steel rib support structures have been developed. For the purpose of verification, the behavior of the supporting structure is verified by model experiments reduced to shotcrete and steel rib material similarity, the numerical analysis of ΔP and ΔP generated by bottom excavation by Terzaghi theoretical equation. As a result, it was found that the support structure of 20.100~198.423 kN is required for the 10~40 m section of the depth for each soil of weathered soil~soft rock. In addition, as a result of the reduced model experiment, a fixed level of 50% steel rib deposit of steel rib support structure was installed. The study shows that the installation of steel rib support structures will compensate for uncertainties and various problems during construction. It is also thought that the installation of steel rib support structure will have many effects such as stability, economy, and air reduction.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.6
• /
• pp.510-515
• /
• 2016

Recently, corrosion occurred on the piles of a marine bridge located on the NamHae expressway in Korea. A sacrificial anode cathodic protection system was installed to prevent corrosion damage in the marine bridge. In the case of the marine bridge in this study, the sacrificial anode cathodic protection system was applied at the tidal and splash zones of the piles because the upper part of the structure was not corroded, and because corrosion occurs at the tidal and splash zones due to sea tides. To verify the performance of the sacrificial anode cathodic protection system 8 years later, cathodic protection (CP) current, CP potential, and degree of depolarization were measured. The experimental results on the performance of the sacrificial anode cathodic protection system from a total of 60 piles were classified into 4 categories: good CP effect results (13 piles), partial CP effect results (27 piles), temporarily erroneous results (5 piles), and need for maintenance because of delamination (15 piles). It was determined that additional repairs are required, such as the application of bulk anodes and jacket casings, for piles where the CP effect is poor.

• Fire Science and Engineering
• /
• v.6 no.2
• /
• pp.15-24
• /
• 1992

우리나라는 1960년대의 경제개발계획에 따른 공업화 시축의 추진으로 산업의 발달과 경제성장은 인구를 도시로 집중시키면서 도시건축물은 대형화, 고층화, 과밀화 현상을 가져왔다. 한편, 국민생활의 향상과 산업활동의 다양화로 화재발생의 주요원인이 되는 전기, 가스, 유류등의 사용량이 해마다 늘어나고 있어 화재의 위험을 가중시키고 있다. 최근 10연간('81~'90) 전국에서 발생한 화재사고는 9만 5,154건이 발생하여 인명피해 1만1,117명, 재산피해 1,859억 2,200만원의 많은 손실을 가져 왔으며, 이 중에는 서울에서 발생한 화재가 3만6,089건으로 전체의 37.9%을 차지하고 있다. 화재가 발생할 경우 대형 참사를 방지하고 귀중한 인명피해는 물론 경제적 손실을 최저로 줄일 수 있는 소방시설을 도시건축물에 설치하여 이에 대비하는 것이 무엇보다 귀중한 일이다. 이는 화재예방 또는 발생 초기에 이를 감지, 통보하고 피난하며 소화활동에 이르는 모든 방재 및 소화를 위한 소방시설의 유용성을 최대로 발휘할 수 있기 때문이다. 본 논문에서는 서울특별시를 중심으로 도시건축물에 설치된 소방시설의 유지 관리 실태와 화재시 소방시설의 이용실태를 분석하여 문제점을 도출하고 이에 대한 개선방향을 제시하므로서 예방소방행정의 발전을 기하고저 하였으며, 그 내용을 요약하면 다음과 같다. 제1장에서는 서론부분으로서 연구의 목적과 범위및 접근 방법을 서술하였고, 제2장에서는 도시소방행정의 특성 및 소방환경의 변화로 먼저 소방행정의 의의와 도시소방행정의 유형으로 예방소방과 진압소방 그리고 구급.구조업무등을 살피고. 도시소방환경변화에 따른 화재발생추세를 살펴 보았다. 제3장에서는 도시건축물에 설치하는 소방시설의 설치.유지 및 이용실태를 검사.분석하였다. '90년도 서울시내 소방서에서 실시한 소방대상물에 대한 소방검사와 방화관리자에 대한 설문조사를 실시하여 소방시설의 유지관리실태를 통계.분석한 결과, 소방시설이 양호한 소방대상물은 전체의 75.9%이며, 불량소방대상물은 24.1%로 나타났다. 그리고 화재가 발생한 소방검사대상물에 대한 화재현장 조사결과 화재시 소방시설을 사용한 소방대상물은 전체의 72.1%를 차지하고 있다. 제4장에서 는 소방시설의 문제점으로 \circled1 소방설비부실공사, \circled2 소방시설 유지관리능력부족, \circled3 소방검사제도 불합리등이며, 이에 대한 개선방향으로 \circled1 소방설비 시공자의 지도. 감독강화, \circled2 자체시설관리능력향상, \circled3 예방소방행정제도의 개선을 제시하였다. 제5장은 결론으로, 우리나라가 최근 경제성장과 산업의 발달로 도시건축물의 화재발생 위험이 가중되면서 이에 대한 소방안전대비책이 요구된다. 이에는 도시건축물에 방화시설과 소방시설을 완비하고, 그리고 자격있고 유능한 방화관리자 선임하여 자체 소방계획을 수립하여 시설점검, 정비와 유지관리를 철저히 한다면 어떠한 화재도 예방 또는 초기에 진압할 수 있고, 또한 입주검자에 대한 소방교육 및 훈련을 지속적으로 수행하여 나간다면 여하한 도시건축물의 소방안전도 그 목적을 달성하리라고 생각한다.

• Korean Journal of Construction Engineering and Management
• /
• v.9 no.4
• /
• pp.193-205
• /
• 2008

Quality is an important keyword representing the corporate competitiveness and image in today' s construction industry. Especially in concrete construction, any problems or defects in fresh concrete can significantly degrade the entire quality and performance of the facility built. Thus, adequate quality inspection and testing must be exercised over the fresh concrete, if concrete with the required strength, durability and appearance is to be obtained. The testing of concrete delivered to the construction job site involves testing of fresh concrete and performing strength tests on hardened concrete. The principal tests conducted on fresh concrete include the slump test and tests for air and salt content. The temperature of fresh concrete should be checked out hot or cold weather concreting. The 7-day and 28-day strength of hardened concrete are also determined by compression tests on usually cylinder samples. However, it is very complex and time-consuming process requiring a lot of efforts to document those on-site concrete testing results and to accumulate their historical data. The primary objective of this study is to suggest a unique PDA and web-based system which enables an on-site quality manager to effectively conduct the concrete inspection and testing, automatically document and accumulate the collected historical data, and promptly obtain the approval from supervisors. Finally, it is anticipated that the effective use of the proposed PDA and web-based system would be able to improve reliability of the concrete quality inspection and testing data as well as significantly reduce the approval process.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.5
• /
• pp.187-194
• /
• 2010

As the design of the pillar width (PW) of the parallel tunnels in downtown area, in which are located in plains zone with deep alluvium compared with mountain tunnels, is directly related with pre-compensation payment and costs of the underground area, it has to be planned as to keep minimum distance while securing the stability of the parallel tunnels. Although PW of downtown road tunnel in Korea is standardized as 1.5D(D: diameter of the tunnels), PW sometimes has to be reduced within 1.5D to adjust the tunnel lines to the city plan in the cases of the inlet and outlet of the tunnels. In this paper, the design and the analyses of optimum PW of the NATM type road tunnel in the downtown area are introduced. The relationship among the tunnel line planning and underground compensation fee, and ground characteristics are evaluated. In the determination of PW distance, the numerical analyses of underground road tunnels were performed, including the use of the strength decrease method and strength/stress ratio method. In the cases of inlet and outlet part of the tunnels where the stability of the pillars is poor due to contiguous construction of the parallel tunnels, the reinforcement methods are recommended for securing the stability. Numerical verification was performed for the reinforcement proposed.

• Korean Journal of Construction Engineering and Management
• /
• v.22 no.3
• /
• pp.61-68
• /
• 2021

This study analyzed the influencing factors for urban redevelopment projects with a relatively long project duration in the context of Seoul's increasing urbanization rate and aging. Among the business areas that have been designated since 2005 and have been approved for the management and disposal plan of the entire Seoul area, 75 business areas have been set as targets. A hedonic price model was used to analyze the project area, economic, and locational characteristics as independent variables with the project duration from designation of zones to approval of management and disposal plans as dependent variables. As a result of the analysis, the smaller the project area, the larger the area occupied per union member, the larger the land price change rate, and the smaller the KOSPI index, the shorter the required period. This study has the distinction of empirically analyzing the effect of characteristic variables considering size and economic and locational characteristics on period. It provides implications that the area of the business area, the number of union members, and economic conditions should be considered when establishing a business area.

• Journal of the Korean Geotechnical Society
• /
• v.38 no.12
• /
• pp.7-17
• /
• 2022

The ratios of water and controlled low-strength materials (CLSM) were selected as 1:0.4, 1:0.6, 1:0.8, 1:1.0, and 1:1.2 to minimize the construction and long-term decrease in uniaxial compressive strength due to dry shrinkage through the combination of water, CLSM, and expansion agent. Approximately 2% and 5% of the expansion agent were added for each blending condition. As a result, it was found that the compressive strength decreased and the expandability increased as the specific gravity of the water increased. In addition, it was confirmed that the compressive strength increased rapidly up to 15 days of age compared to the CLSM used in the field. However, the compressive strength decreased compared to the 15 days of the age as of the 28 days of the age. It showed engineering characteristics similar to CLSM generally used in the field. Therefore, the water and the CLSM were mixed at a ratio of 1:0.8, and the field test was performed by adding 5% of an expansion agent. As a result, 28 days after age, the cavity waveform was observed using the handy GPR exploration system, and it was found that cavity waveform was relaxed or disappeared.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.3
• /
• pp.25-40
• /
• 2007

Excessive earth pressure is one of the major mechanical factors in the deformation and damage of Cut-and-Cover Tunnel lining in shallow tunnels and portals of mountain tunnels (Kim, 2000). Excessive earth pressure may be attributed to insufficient compaction and consolidation of backfill material due to self-weight, precipitation and vibration caused by traffic (Komiya et al., 2000; Taylor et al., 1984; Yoo, 1997). Even though there were a lot of tests performed to determine the earth pressure acting on the tunnel lining, unfortunately there were almost no case histories of studies performed to determine remedial measures that reduce differential settlement and excessive earth pressure. In this study the installation of geotextile mat was selected to reduce the differential settlement and excessive earth pressure acting on the cut-and-cover tunnel lining. In order to determine settlement and earth pressure reduction effect (reinforcement effect) of geotextile mat reinforcement, laboratory tunnel model tests were performed. This study was limited to the modeling of rigid circular cut-and-cover tunnel constructed at a depth of $1.0D\sim1.5D$ in loose sandy ground and subjected to a vibration frequency of 100 Hz. Model tests with varying soil cover, mat reinforcement scheme and slope roughness were performed to determine the most effective mat reinforcement scheme. Slope roughness was adjusted by attaching sandpaper #100, #400 and acetate on the cut slope surface. Mat reinforcement effect of each mat reinforcement scheme were presented by the comparison of earth pressure obtained from the unreinforced and mat reinforced model tests. Soil settlement reduction was analyzed and presented using the Picture Analysis Method (Park, 2003).