• Title/Summary/Keyword: tunnel reinforcement

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Performance Estimation of Tunnel Lining Concrete Reinforced Steel Fiber (강섬유 보강 터널 라이닝 콘크리트의 성능 평가)

  • Jeon, Chan-Ki;Kim, Su-Man;Lee, Myung-Soo;Lee, Jong-Eun;Jeon, Joong-Kyu
    • Proceedings of the Korea Concrete Institute Conference
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    • 2005.11a
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    • pp.579-582
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    • 2005
  • Tunnel lining is the final support of a tunnel and reflects the results of the interaction between ground and support system. Recently it is very difficult to support and manage the tunnel because the cracks on tunnel lining cause problems in supporting and managing tunnels. Therefore the analysis of the cracks is quite strongly required. The major role played by the steel fiber occurs in the post-cracking zone, in which the fibers bridge across the cracked matrix. Because of its improved ability to bridging cracks, steel fiber reinforcement concrete(SFRC) has better crack properties than that of reinforced concrete. In this study, mechanical behaviour of a tunnel lining was examined by model tests. The model tests were carried out under various conditions taking different loading shapes, thicknesses and leakage of lining, and volume content of steel fiber. From these model test, the cracking load, the failure load, defection and cracking position and type were examined and the characteristics of deformation and failure for tunnel lining were estimated and researched.

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Ground Behavior and Reinforcing Methods of NATM Tunnel through Deep Weathered Zone (NATM 터널의 대심도 풍화대층에서의 지반거동 및 보강방법)

  • Sung, Hwa-Don;An, Jung-Whan;Chun, Byung-Sik
    • Proceedings of the KSR Conference
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    • 2007.05a
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    • pp.1782-1788
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    • 2007
  • This study analyzed ground settlement and ground stress depending on tunnel excavation and the ground reinforcing grouting methods for double line road tunnel through deep weathered zone. Diameter of double line road tunnel was approximately 12m and umbrella arch method and side wall reinforcing grouting were applied. The ring-cut split excavation method and CD-cut excavation method for excavation method were applied. Analysis of failure rate and vertical stress ratio show that the tunnel for which the height of the cover(H) was higher than four times the diameter, it can be considered a deep tunnel. Comparisons of various excavation and ground reinforcement methods were showed that CD-cut method results in lower surface and crown settlement, and lower failure rate than where using Ring-cut split method. In addition the side wall reinforcing grouting resulted in reduction of tunnel displacement and settlement.

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Reinforcement of Shotcrete Lining on the Side Wall of Tunnel in Enlargement of Existing ASSM Road Tunnel (측벽부 숏크리트 보강에 의한 재래식 도로터널 단면확대)

  • Kim, Donggyou;Shin, Youngwan
    • Journal of the Korean GEO-environmental Society
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    • v.13 no.12
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    • pp.81-89
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    • 2012
  • The existing tunnel in urban area can be enlarged because of requirement of road-widening by traffic growth. The protector with rectangular cross section can be set up in the tunnel, which will be constructed for enlargement of width, to solve traffic jam around the tunnel. It is impossible to install the rockbolt in the lower area of tunnel due to a limited space between the protector and cutting surface. The objective of this study is to suggest the method of shotcrete thickness increase instead of rockbolt installation in the side wall of tunnel for the stability of tunnel. Numerical analysis was performed to evaluate displacement at the crown of tunnel, convergence of tunnel, and stress in shotcrete lining in 3-lane and 4-lane NATM tunnels enlarged from 2-lane conventional tunnel. There were three types of analysis condition, rockbolt installation, no rockbolt installation, and increase of shotcrete thickness without rockbolt in the side wall of tunnel. There was no difference on the displacement at the crown and the convergence of upper tunnel. In the lower tunnel, the convergence in case of no rockbolt installation was larger as maximum 1.3mm than that in case of rockbolt installation. The stress in shotcrete lining in case of no rockbolt installation was larger as maximum 1.3MPa than that in case of rockbolt installation. Numerical analysis was performed to compare the behavior of shotcrete with rockbolt with that of shotcrete, which its thickness was increased, without rockbolt. The shotcrete has an increase of 20%(250mm ${\rightarrow}$ 300mm, 4-lane tunnel)~25%(200mm ${\rightarrow}$ 250mm, 3-lane tunnel) in its thickness to reduce the stress in shotcrete lining. The behavior of shotcrete lining increased the shotcrete thickness by 20%~25% was similar to that of existing shotcrete lining with rockbolt.

Evaluation on Reinforcing Effect of Inclined System Bolting by Model Tests and Numerical Analysis (모형시험 및 수치해석을 통한 경사 시스템 록볼트의 보강효과 분석)

  • Lee, Jea-Dug;Kim, Byoung-Il;Yoo, Wan-Kyu;Han, Jin-Tae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.4
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    • pp.1529-1539
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    • 2013
  • Recent case studies in Japan have shown that rockbolts are commonly installed at an oblique angle to the excavation direction of the tunnel, instead of at a right angle, due to restriction of the working space. In particular, in the case of expansion in an existing tunnel, the working space can be very small, due to the large protective structures necessary to operate within an existing tunnel. In this case, where both the current use of the existing tunnel, and the reinforcement of the ground around the tunnel are required, the effects of installation angles and patterns of rockbolts are important factors in the design process. Therefore, in this study, a total number of 24 model tests are performed, to investigate the reinforcing effects of system bolting installed obliquely from the excavation direction of the tunnel, by changing the installation angle of bolts, longitudinal distance, and bonded length of bolts. The model test results indicate that the relaxed load ratio decreases, with the increase of both the bonded lengths and the number of the installed bolts, resulting in the decrease of the supported area by one bolt. Two-dimensional numerical analysis, which considered the reinforcement effect of inclined system bolting as the change of engineering properties near the tunnel, demonstrated that the deflection patterns at the tunnel crown in the numerical simulations, show a similar tendency to those measured in the model tests.

Analysis on Surface Collapse of the Road NATM Tunnel through the Weathered Rock (풍화대를 통과하는 도로 NATM 터널의 천단부 함몰에 대한 연구)

  • Shin, Eun-Chul;Yoo, Jai-Sung
    • Journal of the Korean Geosynthetics Society
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    • v.15 no.2
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    • pp.55-64
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    • 2016
  • The construction of the road NATM tunnel, which undergoes the weathered zone of the mountain, was in process with the reinforcement methods such as the rock bolt, shotcrete depositing, and the multi step grout with large diameter steel pipe. The collapse from the ceiling, and on the ground surface area(sink hole), of which were measured to be 25m from the ground surface($V=12m(W){\times}14m(L){\times}5m(H)=840m^3$), as well as excessive displacements in the tunnel, had occurred. In order to execute the necessary reconstruction work, the causes of the surface collapses were inspected through the field investigation, in-situ tests, and numerical analysis. As a result, several proper solutions were suggested for both internal and external reinforcements for the tunnel. As a result of numerical analysis, the collapsed zone of the tunnel was reinforced up to 0.5D~1.0D laterally by the cement grouting on the ground surface, 0.5D longitudinally by the multi step grout with large diameter steel pipe in tunnel. With further reinforcement implemented by rebars in lining, the forward horizontal boring was executed to the rest of the tunnel to evaluate the overall status of the tunnel face. Appropriate reinforcement methods were provided if needed.

Development of Inspection and Diagnosis System for Safety and Maintenance in Tunnel (터널 유지관리를 위한 안전진단시스템 개발에 관한 연구)

  • Kim, Young-Geun;Baek, Ki-Hyun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.3 no.1
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    • pp.37-50
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    • 2001
  • Recently, as tunnel structure is getting old, many deformations and defects have been occurred. As tunnel has the characteristics of underground structure, the estimation of the cause of deformation is very difficult. Then, it is necessary to investigate the state of tunnel lining and to estimate the deformation cause and safety for tunnel. In this study, inspection and diagnosis system for effective maintenance in tunnel was researched. Firstly, non-destructive techniques such as GPR (ground penetrating radar), impact echo test, and infrared thermal techniques were applied to tunnel lining inspection. Tunnel lining analysis system was developed to analyze the stability of tunnel. And, tunnel soundness evaluation system was developed to find the probable causes and indicate the method for repair and reinforcement for tunnel.

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A Study on Anisotropic Reinforcing Mechanism of Umbrella Arch Reinforcement Method in Tunnelling (터널 보강용 강관 다단 그라우팅 공법의 이방성 보강 메카니즘 규명에 관한 연구)

  • 배규진;신휴성;최용기
    • Journal of the Korean Geotechnical Society
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    • v.19 no.6
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    • pp.245-259
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    • 2003
  • This paper deals with an Umbrealla Arch Reinforcement Method (UARM) in tunnelling. It is known that the mechanism of the reinforcement system is too complex to be simulated in existent finite element (FE) frameworks when considering its complex geometry of pipe arrangements and contribution of each component of the reinforcement to reinforcing effect. In this study a 3-D elastoplastic FE procedure is, therefore, proposed by introducing homogenisation technique, which is used to define mathematically elastic as well as elastoplastic characteristics of a reinforced ground material as a composite. A number of practical suggestions are addressed considering staged constructions of tunnels. For illustrative purposes, a series of parametric studies are undertaken and anisotropic characteristics of the reinforced ground as well as effects of the reinforcement on tunnel convergences are investigated. It is found that the reinforced ground material defined in homogenisation framework has its mechanical characteristics reasonably representing inherent geometrical and quantitative characteristics of each of constituents.

A new dynamic construction procedure for deep weak rock tunnels considering pre-reinforcement and flexible primary support

  • Jian Zhou;Mingjie Ma;Luheng Li;Yang Ding;Xinan Yang
    • Geomechanics and Engineering
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    • v.38 no.3
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    • pp.319-334
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    • 2024
  • The current theories on the interaction between surrounding rock and support in deep-buried tunnels do not consider the form of pre-reinforcement support or the flexibility of primary support, leading to a discrepancy between theoretical solutions and practical applications. To address this gap, a comprehensive mechanical model of the tunnel with pre-reinforced rock was established in this study. The equations for internal stress, displacement, and the radius of the plastic zone in the surrounding rock were derived. By understanding the interaction mechanism between flexible support and surrounding rock, the three-dimensional construction analysis solution of the tunnel could be corrected. The validity of the proposed model was verified through numerical simulations. The results indicate that the reduction of pre-deformation significantly influences the final support pressure. The pre-reinforcement support zone primarily inhibits pre-deformation, thereby reducing the support pressure. The support pressure mainly affects the accelerated and uniform movement stage of the surrounding rock. The generation of support pressure is linked to the deformation of the surrounding rock during the accelerated movement stage. Furthermore, the strength of the pre-reinforcement zone of the surrounding rock and the strength of the shotcrete have opposite effects on the support pressure. The parameters of the pre-reinforcement zones and support materials can be optimized to achieve a balance between surrounding rock deformation, support pressure, cost, and safety. Overall, this study provides valuable insights for predicting the deformation of surrounding rock and support pressure during the dynamic construction of deep-buried weak rock tunnels. These findings can guide engineers in improving the construction process, ensuring better safety and cost-effectiveness.

A Study on the Ground Movement around Tunnel Reinforced by Umbralla Arch Method (Umbrella Arch 공법에 의한 터널 천단부 보강시 주변 지반의 거동에 관한 연구)

  • 배규진;김창용;문홍득;훙성완
    • Tunnel and Underground Space
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    • v.7 no.4
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    • pp.299-309
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    • 1997
  • Soil and rock improvement and reinforcement techniques are applied to achieve safe tunnel excavation in difficult geological conditions. The Umbrella Arch Method(UAM), one of the auxiliary techniques, is used to reduce ground permeability and improve stabtility of the tunnel by inserting a series of steel pipes into ground around the crown inclined to the longitudinal axis of the tunnel. Additionally, multi-step grouting is added through the steel pipes. UAM combines the advantages of a modern forepoling system with the grouting injection method. This technique has been applied in subway, road and utility tunneling sites for the last few years in Korea. This paper presents the results of analysis of the case studies on ground movements associated with UAM used in the Seoul Subway line 5 constructon site. Improvement of tunnel stability and decrease of ground settlement expected with pipe insertion are also discussed. Finally, the method to minimize ground settlements caused by NATM tunnelling are suggested.

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Design and Construction of Bottom Drainage Tunnel and the Watertight Tunnel (배수형 터널과 방수형 터널의 설계와 시공)

  • Kim, Seung-Ryeol;Park, Gwang-Jun;Park, Bong-Gi
    • Proceedings of the Korean Geotechical Society Conference
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    • 1993.03a
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    • pp.49-58
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    • 1993
  • Reappraisal of the design and the construction concept of the bottom drainage tunnel has been made through the seepage analysis. An appropriate design approach for this tunnel has also been proposed. It was revealed from this study that water pressures acting on the concrete lining in the bottom dralnage tunnel much depend on the permeability of the surrounding ground, the source of water supply and the discharge capacity of dralnage facilities. The full release of these water pressures by the current drainage system could not be expected if this type of tunnel is constructed in the ground including alluvial deposits having a high permeability. The necessity of a proper reinforcement of the concrete lining or a modification of its shapes corresponding to the water pressure has been suggested.

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