• Tunnel and Underground Space
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• v.13 no.2
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• pp.125-137
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• 2003

Field measurements were carried out in this study to investigate the behavior of cut and cover tunnel such as the distribution and the magnitude of the earth pressure during back fill process. Three kinds of measuring instruments, such as the earth pressure load cell, the concrete strain gauge and the reinforcing bar meter of embedded type in concrete structure were installed and measured. Earth pressure load cells measured the outside forces acting on the tunnel lining with radial directions. Three load cells were installed at the crown, the right and the left shoulder of the tunnel, respectively. Three sets of reinforcing bar meter were installed in the double reinforcements of the tunnel lining and their locations were the same with the position of the earth pressure load cells. Concrete strain gauge was installed only one site of the upper compressive part at the tunnel crown. Based on the measurements, the deformation and the earth pressure acting on the tunnel lining were investigated with the back fill process. Considerations on the validity of the field measurements were paid.

• The Journal of Engineering Geology
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• v.13 no.4
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• pp.445-456
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• 2003

Backfill grouting and consolidation grouting are major reinforcing methods that enhance the stability of tunnel by filling the gap between the tunnel lining and the ground and increasing the stiffness of the ground. However, the effect of the grouting on the tunnel lining is not well established. Field measurements such as pressuremeter test, Lugeon test, and lining instruments were peformed to analyze the grouting effect on the tunnel lining for a waterway tunnel. The elastic modulus was increased up to 5 times than that of original rock mass due to consolidation grouting. This study shows that only 10% of grout pressure was acting on the back face of the tunnel lining. The final results are expected to be used for the design of the concrete lining.

• Journal of the Korean Geosynthetics Society
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• v.9 no.2
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• pp.41-50
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• 2010

The concrete lining of a tunnel constructed by NATM used to be regarded as facing material which does not support any load from the surrounding ground. But the recent appraisal of the decrepit tunnels revealed that rockbolts and shotcrete deteriorate with time resulting in loss of supporting capability. Consequently, concrete lining has to support part of the load which used to be supported by rockbolts and shotcrete, and thus should be regarded as the final supporting structure in a tunnel. One of the common, and perhaps the most serious problem in concrete lining is the longitudinal cracks taking place at the tunnel crown. The longitudinal cracks, mostly related to the construction procedures, can be developed by many reasons such as the lack of thickness, wrong materials, bad curing environment, and excessive external forces. Many efforts has been made to control and suppress these cracks but efficient and economic way is yet to be found. For efficient crack control in concrete lining, reinforcement by composite fibers, which is the mixture of steel fiber and nylon fiber, is suggested in this study.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.2
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• pp.165-175
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• 2010

Recently, requirement of a long subsea tunnel has increased due to political, economical and social demands such as saving of distribution costs, improvement of traffic convenience, and regional development. Road and railroad tunnel need a shaft for construction and ventilation because of increase of tunnel length. Shaft diameter, lining sectional thickness and rebar quantity have to be determined for design of concrete lining in the shaft. A lot of structural analyses are needed for optimal design of concrete lining considering shaft diameter, load conditions and ground conditions. Design charts are proposed by structural analyses for various conditions in this study. A sectional thickness and rebar quantity can be easily determined using the proposed design charts.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.357-367
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• 2017

Bending and axial forces simultaneously occur at the cross-section of a shotcrete lining reinforced with steel supports due to the tunnel geometry. The shotcrete has changing flexural stiffness depending on the axial forces and, as a result, severely nonlinear behavior. The mechanical properties of a shotcrete-steel composite also depend on the type of steel support. This study presents a fiber section element model considering the effect of axial force to evaluate the nonlinear behavior of a shotcrete-steel composite. Additionally, the model was used to analyze the effects of different types of steel supports on the load capacity. Furthermore, a modified hyperbolic model for ground reaction, including strain-softening, is proposed to account for the ground-lining interaction. The model was validated by comparing the numerical results with results from previous load test performed on arched shotcrete specimens. The changes in mechanical responses of the lining were also investigated. Results show a lining with doubly reinforcement rebar has similar load capacity as a lining with H-shaped supports. The use of more materials for the steel support enhances the residual resistance. For all types of steel reinforcement, the contribution of steel supports during peak load decreases as the ground becomes stiffer.

• Structural Engineering and Mechanics
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• v.61 no.5
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• pp.593-603
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• 2017

A high-efficiency simplified modelling approach is proposed for investigating the nonlinear responses of reinforced concrete linings of shield tunnels. Material and geometric nonlinearities are considered in the analysis of the lining structures undergoing large deformation before ultimately losing the load-carrying capacity. A beam-spring element model is developed to capture the force-transfer mechanism between lining segments and radial joints. The developed model is validated by comparing analyzed results to experimental results of a single-ring lining structure under two loading conditions: the ground overloading and the lateral unloading respectively. The results show that the lining structure under the lateral unloading due to excavation on the both sides of the tunnel is more vulnerable compared to the case of ground overloading on the top of the tunnel. A parameter study is conducted and results indicate that the lateral pressure coefficient has the greatest influence on the behaviour of the lining structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.757-762
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• 2007

The lining segment which is the main structure of the shield tunnel consists of joints, not continua. Past international and domestic design data have been commonly used for design practices without specific verification about the structural analysis model, design load, and affection of the soil constant of the lining segment. In this study, the propriety is estimated through the comparison between analytical solution and numerical solution for segment analysis and design models of the shield tunnel which is being used internationally and domestically. As a result, the full. circumferential beam jointed spring model (1R-S0) is suggested by considering aspects of convenient use, application to field condition, and accuracy of analysis result. With suggested model, the parameter analysis was conducted for joint stiffness, ground rigidity, joint distribution, and joint number.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.3
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• pp.227-239
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• 2003

For environment-friendly construction, cut-and-cover tunnels have been constructed, thereby leading to embankment slopes with a number of steps. The slopes cause eccentric load on concrete lining of the tunnel. Nevertheless, uniform vertical and horizontal earth pressures, which are determined by considering a self-weight of embankment and $K_0$, are routinely used in structural calculation. Distribution of the earth pressures applied to the lining will lead to a biased calculation far from the actual behavior of the lining. In this study, basic study, therefore, was performed to consider the eccentric load properly in design and analysis of a cut-and-cover tunnel. A method capable of considering the eccentric load in design was proposed and its applicability was numerically examined through a number of examples.

• 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).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.919-930
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• 2014

In this study, the load capacities and behaviors of a shotcrete member with steel supports, as composite member, are investigated numerically by using a fiber section element. The cross section of a shotcrete lining with steel support is divided into a bundle of fibers, which are allocated nonlinear stress-strain relations and used for determining internal forces. To verify the used approach of the finite element method for shotcrete with steel supports, the load-displacement relations of shotcrete lining obtained by numerical analysis are compared with existing experimental results and are analyzed with the stress distribution of the shotcrete and steel support obtained numerically. As a result, it is shown that the proposed approach can predict the load capacities of each material and the overall nonlinear behavior of shotcrete lining with steel supports. The change of location of the neutral axis and the flexural resistance ratio of each material are also derived from the stress distribution of the cross section of the shotcrete lining with steel supports. From the results, it is concluded that the flexural resistance performance of steel support should be considered in shotcrete lining design.