• Geomechanics and Engineering
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• v.35 no.4
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• pp.411-424
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• 2023

Reasonable estimates of tunnel lining dislocations in the operation stage, especially under longitudinal differential settlement, are important for the design of waterproof gaskets. In this paper, a modified shell-joint model is proposed to calculate shield tunnel dislocations under longitudinal differential settlement, with the ability to consider the nonlinear shear stiffness of the joint. In the case of shell elements in the model, an elastoplastic damage constitutive model was adopted to describe the nonlinear stress-strain relationship of concrete. After verifying its applicability and correctness against a full-scale tunnel test and a joint shear test, the proposed model was used to analyze the dislocation behaviors of a shield tunnel in Shanghai Metro Line 2 under longitudinal differential settlement. Based on the results, when the tunnel structure is solely subjected to water-earth load, circumferential and longitudinal joint dislocations are all less than 0.1 mm. When the tunnel suffers longitudinal differential settlement and the curvature radius of the differential settlement is less than 300 m, although maximum longitudinal joint dislocation is still less than 0.1 mm, the maximum circumferential joint dislocation is approximately 10.3 mm, which leads to leakage and damage of the tunnel structure. However, with concavo-convex tenons applied to circumferential joints, the maximum dislocation value reduces to 4.5 mm.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.265-268
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• 2008

The safety of a tunnel under seismic motion is most often evaluated by ovalling deformation of tunnel. This paper research about tunnel's longitudinal deformation. Because of spatial variation of seismic ground motion, the longitudinal structures like tunnel are likely to experience relative displacements along longitudinal direction. The spatially variable ground motion can be estimated by coherency function obtained empirically, and can be considered from different arrival times of ground motion. As a result of estimating tunnel's relative displacements at maximum curvature of tunnel, the displacements and curvatures estimated by coherency function affect the tunnel's safety more than different arrival times. However, if tunnel's displacements by coherency function superpose on displacements by different arrival times, the relative displacements and curvatures of tunnel will be more severe. Therefore, to estimate accurately tunnel's deformation in longitudinal direction has to consider both coherency and wave passage effects.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.487-497
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• 2016

If a tunnel is excavated, the released stress is redistributed in the ground around the tunnel face, which lead the stress state of the surrounding ground of the tunnel and the load acting on the tunnel support to change. If the tunnel face deforms, the ground ahead of it is relaxed, and the earth pressure acting on it decreases. And if the displacement increases so much that, the ground ahead of the tunnel face reaches in failure state. At this time, load would be transferred longitudinally in the tunnel, depending on the cover and the face deformations. The longitudinal load transfers in the tunnels induced by the tunnelling has been often studied; however, the relation between the deformation of the tunnel face and the longitudinal load transfer was rarely studied. Therefore in this study assesses the characteristics of the longitudinal load transfer as the face was failed by displacement by conducting a model test in a shallow tunnel. In other words, the longitudinal load transfer of the tunnel with the progress of the face deform was measured by conducting a model test, beginning at the state of earth pressure at rest. As results of this study, most of the longitudinal load transfers occurred drastically at the beginning of the displacement of the tunnel face, and as the displacement of the face approached the ultimate displacement, it converged to the ultimate displacement at a gentler slope. In other words, when the ground ahead of the tunnel face was still in an elastic state, the longitudinally transferred load increased sharply at the beginning stage but it tended to increase gradually if it approached to the ultimate limit. Thus, it was noted that the earth pressure in the face and the longitudinal load transfer of the tunnel had the same decreasing tendency.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.8
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• pp.763-770
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• 2000

In tunnel ventilation, the Purpose of ventilation control is to keep the required pollution level with minimum consumption of energy But tunnel ventilation has large disturbances caused by discharge of pollutants, traffic forces especially strong for longitudinal ventilation. Hence in this paper, the tunnel ventilation control logic applying fuzzy control theories is proposed and the simulation program of tunnel ventilation control is developed. The characteristics of longitudinal ventilation with jet fans are estimated and the effect of the proposed tunnel ventilation control is verified by the simulation program.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.393-401
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• 2016

In the present study, fault attitudes and the locations of appearance of faults in tunnel faces were predicted by analyzing the trajectory of the maximum longitudinal displacement immediately before the appearance of faults through three-dimensional finite element analysis. A total of 28 fault attitude models were used in the analysis. Those faults that have drives with dip appear first in the upper part of tunnel faces as tunnel excavation progresses and their maximum longitudinal displacement shows a tendency to move from the middle part to the upper part of tunnel faces. Those faults that have drives against dip appear first in the lower part of tunnel faces as tunnel excavation progresses and their maximum longitudinal displacement shows a tendency to move from the middle part or middle upper part to the lower part of tunnel faces. In addition, when the dip of faults is larger the maximum longitudinal displacement moves from the left upper part toward the wall part in the case of drive with dip models and from the left lower part toward the wall part in the case of drives against dip models. Therefore, it was indicated that the attitudes of faults distributed ahead of tunnel faces and the locations where faults appear in tunnel faces can be predicted by analyzing the longitudinal displacement trajectory of tunnel faces following excavation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.6
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• pp.417-427
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• 2010

In the ease that a new cross tunnel is constructed under the existing tunnel, development of a longitudinal arching would be influenced by the existing tunnel. But it is not enough to investigate. Especially, the influence of the structure loads on the ground surface on the new tunnel, which the under-passes existing tunnel has been rarely studied. This study, therefore, aimed to clarify the effect of the existing tunnel and the structure on the ground surface on the development of a longitudinal ground arching during the excavation of a cross tunnel under the existing tunnel. Two-dimensional model tests were carried out in the test box, whose dimension was 30 cm (wide) ${\times}$ 113 cm (deep) ${\times}$ 87 cm (high). The existing tunnel was made of S21 steel tube in 16 cm diameter and 1 mm thickness. The ground surface load was 4.9 kPa and was loaded on the model structure in the size with 30 cm width ${\times}$ 16 cm height. New tunnel was excavated in 250 mm height by a bench cut method. As results, the longitudinal arching would be developed but it was severely influenced by not only the existing upper tunnel but also the ground surface load. The influence of the ground surface load on the development of longitudinal ground arching around a new tunnel showed the highest value when the tunnel face located direct under the surface load.

• Geomechanics and Engineering
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• v.30 no.4
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• pp.363-372
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• 2022

One of the most frequent issues in tunnel excavation is the collapse of rock blocks and the dropping of rock fragments from the tunnel face. The tunnel face can be reinforced using a number of techniques. One of the most popular and affordable solutions is the use of face longitudinal dowels, which has benefits including high strength, flexibility, and ease of cutting. In order to examine the reinforced face, this work shows the longitudinal deformation profile and ground response curve for a tunnel face. This approach is based on assumptions made during the analysis phase of problem solving. By knowing the tunnel face response and dowel behavior, the interaction of two elements can be solved. The rock element equation derived from the rock bolt method is combined with the dowel differential equation to solve the reinforced ground response curve (GRC). With a straightforward and accurate analytical equation, the new differential equation produces the reinforced displacement of the tunnel face at each stage of excavation. With simple equations and a less involved computational process, this approach offers quick and accurate solutions. The FLAC3D simulation has been compared with the suggested analytical approach. A logical error is apparent from the discrepancies between the two solutions. Each component of the equation's effect has also been described.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.887-903
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• 2017

Lots of shallow tunnels are constructed in the mountainous areas where the stress distribution in the ground around tunnel is not simple, also the impact of stress conditions on the longitudinal load transfer characteristics is unclear. The tunnel construction methods and the ground conditions would also affect the longitudinal load transfer characteristics which would be dependant on the displacement patterns of tunnel face. Therefore, in this study, the slope of the ground surface was varied in $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$, and the longitudinal load transfer depended on the deformation conditions of tunnelface (that were maximum deformation on the top, constant deformation, and maximum deformation on the bottom), and the stress distribution at tunnelface. As results, when the tunnelface deformed, the earth presure on the tunnelface decreased and the load at tunnel crown increased. The load transferred on the crown was influenced by the earth presure on tunnel face. Smaller load would be transfered to the wide areas when the slope of ground surface decreased. When the slope of ground surface became larger, the longitudinal load transfer would be smaller and would be concentrated on tunnelface, In addition, the shape of the transferred load distribution in the longitudinal direction was dependant on the deformation shape of tunnelface. The deformation shape of tunnelface and stress conditions in longitudinal sections would affect the shape and the magnitude of the load transfer in the longitudinal directions.

• Journal of the Korean Geotechnical Society
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• v.27 no.11
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• pp.47-54
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• 2011

In this paper, longitudinal behaviors of a tunnel with respect to various conditions are analyzed, and a new equation of longitudinal deformation curve during tunnel expansion is proposed. Finally, the range of protection by a protector is investigated using the proposed equation. To achieve the objectives, numerical analysis according to the ground and expansion conditions is performed. The results show that the range of protection, when a 2 traffic lane tunnel is expanded to 4 traffic lanes, should cover at least 24m to backward and 35m forward.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.323-330
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• 2007

Recently, due to the effective land utilization and environmental protection, the construction of 2-arch tunnel has been gradually increased. In spite of this tendency, the mechanical information for the 2-arch tunnel, especially such as its behavior characteristics and mechanism are not enough. Therefore in this study, the theoretical and numerical studies on the behavior characteristics of 2-arch tunnel are carried out and longitudinal optimum separated distance of tunnel face is proposed by considering the analysis results from the behavior of advanced excavation of tunnel and stress of central pillar. As a result, longitudinal optimum separated distance of tunnel face is in 0.5D for the better safety of 2-arch tunnel by rapidly decreasing the stress concentration of central pillar.