• Title, Summary, Keyword: Rail Stability

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Real-scale Accelerated Testing to Evaluate Long-term Performance for Bridge/Earthwork Transition Structure Reinforced by Geosynthetics and Cement Treated Materials (토목섬유와 시멘트처리채움재로 보강한 교량/토공 접속구조의 장기공용성 평가를 위한 실물가속시험)

  • Lee, Il-Wha;Choi, Won-Il;Cho, Kook-Hwan;Lee, Kang-Myung;Min, Kyung-Chan
    • Journal of the Korean Society for Railway
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    • v.17 no.4
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    • pp.251-259
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    • 2014
  • The transition zone between an earthwork and a bridge effect to the vehicle's running stability because support stiffness of the roadbed is suddenly changed. The design criteria for the transition structure on ballast track were not particular in the past. However with the introduction of concrete track is introduced, it requires there is a higher performance level required because of maintenance and running stability. In this present paper, a transition structure reinforced with geosynthetics is suggested to improve the performance of existing bridge-earthwork transition structures. The suggested transition structure, in which there is reinforcing of the approach block using high-tension geosynthetics, has a structure similar to that of earth reinforced abutments. The utilized backfill materials are cement treated soil and gravel. These materials are used to reduce water intrusion into the approach block and to increase the recycling of surplus earth materials. An experiment was performed under the same conditions in order to allow a comparison of this new structure with the existing transition structure. Evaluation items are elastic displacement, cumulative settlement, and earth pressure. As for the results of the real-scale accelerated testing, the suggested transition structure has excellent performance for the reduction of earth pressure and settlement. Above all, it has high resistance the variation of the water content.

A Study on the Reinforcement Effect Analysis of Aging Agricultural Reservoir using Surface Stabilizer (표층안정재를 사용한 노후 농업용 저수지의 보강효과 분석에 관한 연구)

  • Kim, Jae-Hong;Kim, You-Seong;Cho, Dae-sung
    • Journal of the Korean Geosynthetics Society
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    • v.19 no.2
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    • pp.13-21
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    • 2020
  • In Korea, small reservoirs have been constructed for the supply of agricultural water, but most of them have been over 50 years from the year of construction. Aging agricultural reservoirs are being investigated for serious defects such as leaks and movements in slope, which are very vulnerable to safety. Accordingly, grouting methods are used to reinforce aging agricultural reservoirs in Korea. However, cement used as a grouting injection material consumes natural resources and generates a large amount of greenhouse gases during production. In addition, there is a problem that sufficient reinforcement is not made due to various factors such as the injection amount, the compounding ratio, the injection pressure, and etc. Therefore, due to these problems, the development of new materials and methods that can replace the grouting method and cement is required. In order to solve these problems, this study conducted an laboratory test on the surface stabilizer used to secure the stability of road and rail slopes. In addition, the program was analyzed and the reinforcing effect was examined when the surface stabilizer was used as reinforcement material for aging agricultural reservoir. As a result of the laboratory test, when the surface stabilizer is mixed, the increase of cohesion is possible up to 9% and there is no change in the friction angle. The results of the program analysis showed that the 1.0m reinforcement of slopes increased the factor of safety by 1.4 times, making it possible to reinforce the aging agricultural reservoir using surface stabilizers. And as a reinforcement method, it was analyzed that it is most appropriate to reinforce the slope and the bottom of slope simultaneously.

Static and Dynamic Analysis for Railway Tunnel according to Filling Materials for overbroken tunnel bottom (철도터널 하부 여굴처리 방법에 대한 정적 및 동적 안정성 검토)

  • Seo, Jae-Won;Cho, Kook-Hwan
    • Journal of the Korean Society for Railway
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    • v.20 no.5
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    • pp.668-682
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    • 2017
  • Alignments of railways recently constructed in Korea have been straightened due to the advent of high-speed rail, which means increasing the numbers of tunnels and bridges. Overbreak during tunnel construction may be unavoidable, and is very influential on overall stability. Over-excavation in tunneling is also one of the most important factors in construction costs. Overbreak problems around crown areas have decreased with improvements of excavation methods, but overbreak problems around bottom areas have not decreased because those areas are not very influential on tunnel stability compared with crown areas. The filling costs of 10 cm thickness of overbreak at the bottom of a tunnel are covered under construction costs by Korea Railway Authority regulations, but filling costs for more than the covered thickness are considered losses of construction cost. The filling material for overbreak bottoms of tunnels should be concrete, but concrete and mixed granular materials with fractured rock are also used for some sites. Tunnels in which granular materials with fractured rock are used may have a discontinuous section under the concrete slab track. The discontinuous section influences the propagation of waves generated from train operation. When the bottom of a tunnel is filled with only concrete material, the bottom of the tunnel can be considered as a continuous section, in which the waves generated from a train may propagate without reflection waves. However, a discontinuous section filled with mixed granular materials may reflect waves, which can cause resonance of vibration. The filled materials and vibration propagation characteristics are studied in this research. Tunnel bottom filling materials that have ratios of granular material to concrete of 5.0 %, 11.5 %, and 18.0 % are investigated. Samples were made and tested to determine their material properties. Static numerical analyses were performed using the FEM program under train operation load; test results were found to satisfy the stability requirements. However, dynamic analysis results show that some mixed ratios may generate resonance vibration from train operation at certain speeds.

A study on the characteristics of tunnel deformation and support system according to tunnel portal reinforcement method (터널 갱구부 보강방법에 따른 터널 변형 및 지보재 응력특성에 관한 연구)

  • Moon, Kyoung-Sun;Seo, Yoon-Sic;Kang, Si-On;Kim, Sang-Hwan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.3
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    • pp.625-639
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    • 2018
  • This study is about the reinforcing type of reinforcement method which is reinforced in tunnel portal of tunnel with bad ground condition. Generally, it is known that the horizontal reinforcement method is more effective than the conventional reinforcement method. However, as a limitation of the tunnel construction technology, it is being constructed by the superposition reinforcement method. In recent years, high-strength large-diameter steel pipes and horizontally oriented longitudes (L = 30.0~50.0 m) construction technology have been developed. Therefore, it is required to study reinforcement method of tunnel portal reinforcement method. Therefore, 3-D numerical analysis (Midas GTS NX 3D) was performed by setting the reinforcement method (No reinforcement type, overlap reinforcement type and horizontal reinforcement type) and ground condition as parameters. As a result, it was considered that the reinforcement effect was the largest as the horizontal reinforcement type of the reinforcement method was the smallest in the displacement and the support material stress. Based on the results of the numerical analysis, horizontal steel pipe grouting was applied to the actual tunnel site. The displacement of the tunnel portal and the stress of the support material occurred within the allowable values and were considered to ensure sufficient stability.

Monitoring System of Rock Mass Displacement and Temperature Variation for KURT using Optical Sensor Cable (광섬유센서케이블을 이용한 지하연구시설의 지반변위 및 온도변화 감시시스템 구축)

  • Kim, Kyung-Su;Bae, Dae-Seok;Koh, Yong-Kwon;Kim, Jung-Yul
    • The Journal of Engineering Geology
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    • v.19 no.1
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    • pp.63-70
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    • 2009
  • The optical fiber cable acting as a sensor was embedded in the underground research tunnel and portal area in order to monitor their stability and the spatial temperature variation. This system includes two types of sensing function to monitor the distributed strain and temperature along the line, where sensor cable is installed, not a point sensing. According to the results of one year monitoring around the KURT, there is no significant displacement or movement at the tunnel wall and portal slope. However, it would be able to aware of some phenomena as an advance notice at the tunnel wall which indicates the fracturing in rockmass and shotcrete fragmentation before rock falls accidently as well as movement of earth slope. The measurement resolution for rock mass displacement is 1 mm per 1 m and it covers 30 km length with every 1m interval in minimum. In temperature, the cable measures the range of $-160{\sim}600^{\circ}C$ with $0.01^{\circ}C$ resolution according to the cable types. This means that it would be applicable to monitoring system for the safe operation of various kinds of facilities having static and/or dynamic characteristics, such as chemical plant, pipeline, rail, huge building, long and slim structures, bridge, subway and marine vessel. etc.

A Case Study on the Hybrid Reinforcement Retaining Wall System Reinforced by Soil Nail and Steel Strip (쏘일네일과 강재스트립으로 보강된 복합보강토옹벽 시스템의 사례연구)

  • Chun, Byung-Sik;Kim, Hong-Taek;Cho, Hyun-Soo;Do, Jong-Nam
    • Journal of the Korean Geotechnical Society
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    • v.24 no.12
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    • pp.5-12
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    • 2008
  • The reinforced earth wall, which is able to improve the strength of soil highly, is required in case of supporting high surcharge load such as high speed rail way, high embankment road, and massive reinforced earth wall in a mountainous area. And also, it is continuously required that the method is able to minimize the amount of excavated soil on account of environmental issue, boundary of land, etc., on excavation site. However, because the required length of reinforcement should be $60{\sim}80%$ of the height of reinforced earth wall for general reinforced earth wall, in fact the reinforced earth wall is hardly applied on the site of cut slope. In this paper we studied the design and construction cases of hybrid reinforcement retaining wall system combined with steel strips and soil nails, connecting the reinforced earth wall reinforcements to the slope stability reinforcements (soil nails) to ensure sufficient resistance by means of reducing the length of reinforcements of reinforced earth wall. And the feasibility of hybrid reinforcement retaining wall system, suggested by real data measured on site, is also discussed.

A STUDY ON THE CHUMSUNGDAE'S FIGURES AND FUNCTIONS (첨성대 수치와 역할에 대한 연구)

  • Kim, Kwang-Tae
    • Publications of The Korean Astronomical Society
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    • v.28 no.2
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    • pp.25-36
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    • 2013
  • Chumsungdae is an ancient astronomical observatory whose main role was doing 'chunmoon'. It was administrate by a royal advisory agency on state affairs. The observers observed the heaven on the observatory platform, recorded peculiar events, and watched and interpreted the signs displayed in the heaven. Chumsungdae is an stonemasonry which represents almanac principles with its peculiar shapes and the numbers of strata and stones. The numbers were thoroughly invented to match exactly the almanac constants. Chumsungdae is comprised largely of three main parts, namely the square base, the stratified cylindrical body, and the top #-shaped stonework, and the total number of stones is 404. The number of the strata (27) and the height of the cylindrical body (27 尺) stand for the days in a sidereal month (27.3 days), which implies that the motion of the Moon with respect to the stars was given more priority than to the Sun at that time of geocentricism. And the cylindrical body was thoroughly designed to consist of 365 stones, which is of course the number of days in a solar year. In addition, there are 12 strata each under and above the south entrance and this in sum makes the 24 divisions of the year. Also there is 182 stones below the 13th stratum and this represents the number of days in the winter ~ summer solstice period, and the rest 183 stones the vice versa. The #-shaped top stonework was aligned in such a way that one of the diagonals points the direction of sunrise on the winter solstice. The square base also layed with the same manner. The south entrance was built 16 degrees SE, and the upright direction of the right pillar stone coincides with the meridian circle. This was a kind of built-in standard meridian circle facilitating the observations. In a symbolic sense, Chumsungdae was thought as the tunnel reaching the heaven, where the observers wished to be enlightened with the signs and inspirations in need. With the craftsmanship and skill, the builder reinforced the stratified cylindrical body with two sets of #-shaped beam stones, piercing at a right angle at 19th ~ 20th and 25th ~ 26th strata. Likewise, by placing the double #-shaped stonework with 8 beam stones on the platform of the observatory, both the stability of the stonemasonry and a guard rail for the nightly observers were securely provided.

A Case Study on Elephant Foot Method for Railway Tunneling in Large Fault Zone (대규모 단층대구간에서의 철도터널 우각부 보강공법 적용성 연구)

  • Lee, Gilyong;Oh, Jeongho;Cho, Kyehwan;Lee, Doosoo
    • Journal of The Korean Society of Civil Engineers
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    • v.36 no.6
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    • pp.1161-1167
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    • 2016
  • In this study, an attempt was made to conduct a case study on the development of ground expansive displacement due to lack of bearing capacity of original ground in spite of applying reinforcement treatments that intended to enhance the stability of big size high-speed rail tunnel in large fault zone. For the purpose of this, in-situ measurements made in the middle of excavation stage were analyzed in order to characterize ground responses and numerical analysis was performed to evaluate the effectiveness of reinforcement technique such as elephant foot method applied for this site via comparing with field monitoring measurements. In addition, further numerical studies were carried out to investigate the influence of leg pile installation angle and length, which is one of types of elephant foot method. The results revealed that the optimum condition for the leg pile installation is to maintain 45 degree of installation angle along with 6 meter of embedment depth.