• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.1
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• pp.13-30
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• 2016

This paper concerns the development of an optimized TBM segmental lining design system for a subsea tunnel. The subsea tunnel is normally laid down under the sea water and submarine ground which consists of soil or rock. The design system is the series of process which can predict segmental lining member forces by ANN (artificial neural network system), analyze suitable section for the designated ground, construction and tunnel conditions. Finally, this lining design system aims to be connected with a BIM system for designing the subsea tunnel automatically. The lining member forces are predicted based on the ANN which was calculated by a FEM (finite element analysis) and it helps designers determine its segmental lining dimension easily without any further FE calculations.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.121-139
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• 2023

Various tunnels such as road, subway, and railway are under construction and operation. Various types of linings are used for structural stability of tunnel structures, and concrete segment linings are mainly installed in TBM tunnel construction. In this paper, when a fire occurs in a tunnel, the impact on the concrete segment lining, which is the structure in the tunnel, and related standards, fire resistance evaluation and fire resistance method are investigated through literature review and related contents are presented. Through this, it is intended to provide an information for practitioners to secure the safety of concrete segment linings against tunnel fires.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.227-236
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• 2015

In impermeable ground, water pressure is applied due to discontinuity such as joint or fissure. Therefore, water pressure should be considered in design regardless of ground condition. However, when the shape of segmental lining is circular, water pressure may reduce the lining member force, so it is important to define the assumption and the concept of design in case of high water pressure. This paper presents the concepts of design of the lining of shield tunnel at high water pressure and in impermeable ground condition. In addition, the member forces in various load conditions were compared in this study. (elastic equation, closed form solutions, beam-spring model).

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1125-1146
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• 2018

Segment lining applied to the TBM tunnel is mainly made of concrete, and it requires sufficient structural capacity to resist loads received during the construction and also after the completion. When segment lining is design to the Limit State Design, both Ultimate Limit State (ULS) and Service Limit State (SLS) should be met for the possible load cases that covers both permanent and temporary load cases - such as load applied by TBM. When design segment lining, it is important to check structural capacity at the joints as both temporary and permanent loads are always transferred through the segment joints, and sometimes the load applied to the joint is high enough to damage the segment - so called bursting failure. According to the various design guides from UK (PAS 8810, 2016), compression stress at the joint surface can generate bursting failure of the segment. This is normally from the TBM's jacking force applied at the circumferential joint, and the lining's hoop thrust generated from the permanent loads applied at the radial joint. Therefore, precast concrete segment lining's joints shall be designed to have sufficient structural capacity to resist bursting stresses generated by the TBM's jacking force and by the hoop thrust. In this study, bursting stress at the segment joints are calculated, and the joint's structural capacity was assessed using Leonhardt (1964) and FEM analysis for three different design cases. For those three analysis cases, hoop thrust at the radial joint was calculated with the application of the most widely used limit state design codes Eurocode and AASHTO LRFD (2017). For the circumferential joints bursting design, an assumed TBM jack force was used with considering of the construction tolerance of the segments and the eccentricity of the jack's position. The analysis results show reinforcement is needed as joint bursting stresses exceeds the allowable tensile strength of concrete. This highlights that joint bursting check shall be considered as a mandatory design item in the limit state design of the segment lining.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.251-262
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• 1999

The assemblage of the trapezoidal segments, which is being used increasingly to shield tunnelling, with Guide rod and Dowel forms tunnel lining. In this case the larger the taper angle of trapezoidal segment is, the easier the assembly work becomes. The large angle can reduce the water proof material's phenomenon of being pushed back, but decreases the structural safety in connecting section of tunnel lining. In this paper a 3-dimensional numerical analysis was performed to estimate the exact behavior of a model shield tunnel made by connecting 3-dimensionally various accessories with irregular sectioned segments. We obtained the operating force of connecting section according to the change of taper angle of trapezoidal segment and sought for improved scheme for connecting section by comparing and analyzing the test results on the friction resistance force of connecting parts.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.363-382
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• 2015

This paper presents a numerical study on the effect of segment assembly characteristics on the TBM segmental lining member section forces. Analyses have been carried out through the two-ring beam finite element model by Midas civil 2012+. TBM segment lining member forces are determined by various joint characteristics. In this study, the segmental member forces were investigated with various joint number and orientation at fixed values of joint stiffness, ground spring parameters. The numerical results were used to identify trends of the member forces in the tunnel lining with the segment assembly characteristics.

• Journal of the Korean GEO-environmental Society
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• v.7 no.2
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• pp.67-76
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• 2006

For a hydro power plant project, the headrace tunnel having a finished diameter of 3.3 m was constructed in volcanic rocks with well-developed vertical joint and high groundwater table. The intake facility was located 20.3km upstream of the powerhouse and headrace tunnel of 20km in length and penstock of 440m in height connected the intake and the powerhouse. The typical caldera lake, Lake Toba set the geology at the site the caving of the ground caused tension cracks in the vertical direction to be developed and initial stresses at the ground to be released. High groundwater table(the maximum head of 20bar) in the area of well-connected vertical joints delayed the progress of tunnel excavation severely due to the excessive inflow of groundwater. The excavation of tunnel was made using open-shield type TBM and mucking cars on the rail. High volume of water inflowraised the water level inside tunnel to 70cm, 17% of tunnel diameter (3.9m) and hindered the mucking of spoil under water. To improve the productivity, several adjustments such as modification of TBM and mucking cars and increase in the number of submersible pumps were made forthe excavation of severe water inflow zone. Since the ground condition encountered during excavation turned out to be much worse, it was decided to adopt PC segment lining instead of RC lining. Besides, depending on the conditions of the water inflow, rock mass condition and internal water pressure, one of the invert PC segment lining with in-situ RC lining, RC lining and steel lining was applied to meet the site specific condition. With the adoption of PC segment lining, modification of TBM and other improvement, the excavation of the tunnel under severe groundwater condition was successfully completed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.5
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• pp.303-314
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• 2021

With the high quality/high stiffness/high strength of segment lining, segment lining is increasingly used as the final lining of the tunnel. Precast concrete lining has higher quality and strength than field concrete. Paradoxically, this contributes to greater damage to concrete in the event of a fire in a tunnel. In this study, tests were conducted to determine the fire resistance performance of segment linings according to fiber content in fire resistance methods using synthetic fibers such as PP fibers. As a result, it was confirmed that fire resistance performance required by the relevant project can be secured when using 1.5 kg/m³ of PP fiber. In addition, comparison of the results of PP fibers with PET, a similar synthetic fiber, showed better fire resistance performance than when PP fibers were used.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.95-105
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• 2014

Reinforced concrete (RC) shield tunnel lining must be designed for fireproof performance because the lining is sometimes exposed to very high temperature due to traffic accidents. Both experimental and numerical studies are carried out to evaluate fire resistance performance of precast RC tunnel lining systems. In the experimental studies, six full-scale precast RC tunnel segments are exposed to fire in order to examine the influence of various parameters on the fire resistance performance of precast RC tunnel lining. We used the temperature curve of the RABT criteria, which are severe conditions of fire temperatures. The fire test showed that the explosive spalling was not observed by substituting concrete to PP fiber reinforced concrete. A transient heat flow analysis was carried out in consideration of the material properties that change with temperature, and the results showed good agreement with the test results.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.99-118
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• 2018

Recently, the limit state design method in the design of the structure is in global trend, but it is limited to a few structures in Korea. Since the introduction of the limit state design method has recently been attempted for tunnels, which are the main underground structures, it is surely necessary to understand the latest limit state design method. Therefore, based on the recently published AASHTO LRFD Road Tunnel Design and Construction Guide Specification (2017), structural load factors and load combinations were reviewed, and various factors which should be applied for the review of structures have been analyzed. In this study, utility tunnel section and subway tunnel sections used in Korea were analyzed by the limit state design method, and we have analyzed the direction of application of limit state design method through studying the tendency of member force by various influential factors such as ground conditions, load modifier and joint stiffness.