• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.931-946
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• 2018

In line with the increased usability of utility pipe conduits in urban areas, construction and R&D activities of utility tunnel, incorporated with the shield TBM method, are actively under way. The utility tunnels are installed through underground excavation, and thus are relatively weak in terms of construction safety. However, hazards associated with the utility tunnel construction have not been properly identified, despite the introduction of a policy to the 'Design for Safety' for the purpose of reducing accident rates in the construction industry. Therefore, in this study, following the derivation of hazards associated with utility tunnel, these hazards were then used as the basis to uncover key safety hazards requiring extensive management in a field, which were then used to conduct a risk assessment having applied the matrix method so that the results can be utilized in risk assessment during the stages of utility tunnel planning, design, and construction, while also serving as a data reference.

• Tunnel and Underground Space
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• v.12 no.2
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• pp.115-119
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• 2002

Four tunnels have been planned to operate a large diameter shielded TBM in Gwangju urban subway construction site. No.1 tunnel has completely been excavated for 13 months operating. Net penetration rate and its relations with thrust farce of the shielded TBM are analysis in this report. This shallow depth tunnel of 536m length is located in soil layers at launching and in hard rocks at ending with 84 m length. The weekly net penetration rates haute dropped down as low as 20∼110 mm/hr in rock while 400∼800 mm/hr in soil. The actual penetration rates we proved to be high as the theoretical penetration rate which is analysis in consideration of conditions of machine and rock. And net penetration rate is investigated to increase linearly thrust force.

• 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.16 no.1
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• pp.63-74
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• 2014

The lining of shield TBM tunnel is composed of segments, therefore segment joints are induced by connecting each segment. Segment joint is considered as joint stiffness in the design of TBM tunnel. Depending on the choice among the different stiffness equations, the joint stiffness values determined can be varied largely. Therefore, the influence of joint stiffness value on the design of segment lining should be verified. In this study, the joint stiffness values were determined firstly by using various equations and total change boundary was justified. Within the change boundary determined, the member forces were calculated by changing the joint stiffness through the numerical analysis and consequently the stability of segment lining was investigated by applying nominal strength. The results showed that the segment joint stiffness did not affect the design of segment lining largely.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.677-685
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• 2018

In construction, schedule management is the basic but important step, for the effective schedule management, the preparation of the reasonable schedule table should be prioritized. In the design stage, the optimal construction period can be selected through comparison of various conditions and construction methods considering weather conditions and site characteristics. But, At the planning phase, it is difficult to select the effective method and calculate the proper construction period by the basic data(D/B) analysis. In this paper, the construction method considering characteristics of each type and conditions of existing city was selected. For the reasonable duration calculation, we analyzed the unit schedule for RC method for open type and Shield TBM method for tunnel type. The normal project duration of construction assuming of 1,200m of extension and every 200m of ventilation was prepared by integrating each unit schedule. It was analyzed that it took 893 days for the open type and 616 days for the tunnel type. The results of this study will help to make type selection and normal project duration more easily in the planning phase. If it is linked to the design stage, it will be easy to estimate the process and construction cost.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.3
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• pp.255-280
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• 2024

If there are concerns about the stability of segment lining due to section deficiency or large deformation in shield TBM tunnel, reinforcement can be done through ground grouting outside the tunnel or by using steel plate reinforcement, ring beam reinforcement, or inner double layer lining inside the tunnel. Traditional analyses of shield TBM tunnels have been conducted using a continuum method that does not consider the segmented nature of segment lining. This study investigates the reinforcement mechanism for double layer reinforced sections with internal steel linings. By improving the modeling of segment lining, this study applies Break-joint mode (BJM), which considers the segmented characteristics of segment lining, to analyze the deformation characteristics of double layer reinforced sections. The results indicate that the existing concrete segment lining functioned similarly to ground reinforcement around the tunnel, rather than distribution the load. In general, both the BJM model considering the segmentation of segment lining and the continuum rigid method were similar deformation shapes and stress distributions of the lining under load. However, in terms of deformation, when the load strength exceeded the threshold, the deformation patterns of the two models differed.

• 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.

• Tunnel and Underground Space
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• v.33 no.5
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• pp.299-311
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• 2023

Continuous excavation technologies are developed to improve the excavation rate of shield TBM. Continuous excavation is a technology that provides thrust to segments, excluding being installed one, to reduce tunneling downtime. This paper investigated the prior technology related to continuous excavation segments. The main technology was classified into helical segment, honeycomb segment, and conventional segment methods. The helical segment method has not been applied in actual construction yet, and the honeycomb segment method has not succeeded in commercialization. The continuous excavation method using conventional segments has been successfully demonstrated. The thrust force and operation method of the thrust jacks for the semi-continuous technology were analyzed. Continuous excavation TBM research is also progressing in Korea, and through the analysis of successful cases, the need to develop independent continuous excavation methods has been identified.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.271-287
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• 2013

In this study, more convenient model(S-model) for predicting ground surface settlement is developed through comparing field monitoring data of the domestic subway applied shield TBM method with conventional equation & numerical analysis. Sample stations are chosen from whole of excavation section and lateral & vertical ground surface settlement characteristic with excavation are analysed. Based on analysis result, through the comparison with actual monitoring data, the model that is possible to compute maximum surface settlement and settlement influence area is suggested with assumption that lateral surface settlement forms are composed relaxed zone and elastic zone. In addition, vertical ground surface settlement patterns with excavation are similar to cubic-function and S-model with assumption that coefficients are function of tunnel diameter and depth is suggested. Consequently, the ground surface settlement patterns are significantly similar to actual monitoring data and numerical method result. Thus, as a result, when tunnels are excavated using sheild TBM through rather soft weathered soil & rock layer, prediction of ground surface settlement with excavation using convenient S-model is practicable.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.269-286
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• 2018

Backfill injection pressure in shield TBM affects not only ground settlement but also adjacent underground structures. Therefore, it is essential to estimate a suitable backfill injection pressure in advance in design stage. In this paper, seven suggested equations worldwide to calculate the backfill injection pressure were reviewed and compared. By assuming 6 cases of virtual ground condition, backfill injection pressures were calculated and analyzed. it was confirmed that the backfill injection pressure increases as the depth of overburden increases, but the increasing ratio decreases. The numerical analysis was carried out by applying the calculated backfill injection pressure to investigate the influence of backfill injection pressure on the settlement of surface and crown of tunnel. It was confirmed that the final settlement at the surface and crown of tunnel on the both unsaturated and saturated condition are more influenced by the applied face pressure than the applied backfill injection pressure. In addition, the effect of backfill injection pressure decreases as the depth of overburden increases, and the effect of backfill injection pressure increases as the applied face pressure decreases.