• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.849-860
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• 2019

This paper is a study on the development of equipment system to obtain data on stability in excavation of sharp curve section of Shield TBM. Shield TBM equipment is being used a lot recently for tunnel excavation. Excavation may result in inevitable detours by buildings above the ground or existing underground structures. Preconstruction simulation is required to verify the stability of the construction in case of this. Therefore, it is necessary to establish an automated control system through the development of this equipment system and conduct simulation through simulation of excavation model in the sharp curve section. A system shall be developed to control the left and right angles and thrust of the equipment, and to view data on the earth pressure and propulsion pressure of the equipment in real time during excavation. With this system, the necessary data can be collected for field testing through excavation method and excavation simulation by angle. It is expected that it will be very useful in assessing the actual Shield TBM by conducting a scale-down model experiment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.5
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• pp.325-337
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• 2021

On the road and rail tunnels, the evacuation pathway and facilities such as smoke-control and fire suppression system are essential in tunnel fire. In the long twin tunnels, the cross-connection tunnel is usually designed to evacuate from the tunnel where the fire broke out to the other tunnel. In twin shield tunnels, the segment lining has to be demolished to construct the cross-connection tunnel. Considering the modern shield TBM is mostly the closed chamber type, the exposure of underground soil induced by removal of steel segment lining is the most danger construction step in the shield tunnel construction. This case study introduces the excavation method using the thrust of large steel pipe and reviews the measured data after the construction. The large steel pipe thrust method for the cross-connection tunnel can stabilize the excavated face with the two mechanisms. Firstly, the soil in front of excavated face is cylindrically pre-supported by the large steel pipe. Secondly, the excavated face is supported by the plugging effect caused by the soil pressed into the steel pipe. It was reviewed that the large steel pipe thrust method in the cross-connection tunnel is enough to secure the construct ability and stability in soil from the measurement results about the deformation and stress of steel pipe.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.3
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• pp.183-198
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• 2021

The EPB (Earth Pressure Balanced) shield TBM method restrains the ground deformation through continuous excavation and support. Still, the significant surface settlement occurs due to the ground conditions, tunnel dimensions, and construction conditions. Therefore, it is necessary to clarify the settlement behavior with its influence factors and evaluate the possible settlement during construction. In this study, the analytical model of surface settlement based on the influence factors and their mechanisms were proposed. Then, the parametric study for controllable factors during excavation was conducted by numerical method. Through the numerical analysis, the settlement behavior according to the construction conditions was quantitatively derived. Then, the qualitative trend according to the ground conditions was visualized by coupling the numerical results with the analytical model of settlement. Based on the results of this study, it is expected to contribute to the derivation of the settlement prediction algorithm for EPB shield TBM excavation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.689-698
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• 2019

In tunnel excavation by TBMs, a cutterhead, which practically excavates the ground, is an important part directly affecting net penetration rate. Most of the researches on the cutterhead design that have been carried out until now are on the cutter arrangement. It is difficult to find a study for the effect of the scraper installation direction on TBM excavation although same cutterheads except for direction of the scraper are used in Korea. Therefore, this paper shows how the direction of scraper installation affects shield-TBM excavation. Discrete element method was used to identify the effect of scraper installation direction on shield-TBM excavation. When the scraper installation direction was outward, the amount of particles per unit time flowed into the cutter head opening was smaller than when the scraper installation direction was inward, and more loads were applied to the cutterhead.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.161-172
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• 2014

An earth pressure balanced shield TBM with the diameter of 4.4 m was designed and manufactured for a subsea discharge tunnel excavation. Its cutterhead was designed to be optimized for the strongest rock mass condition in the tunnel alignment, and then the applicability of the refurbished shield TBM was validated for its maximum capacity. Especially, the maximum cutter penetration depth for the strongest rock mass condition should be kept to be below 7 mm/rev in order to satisfy the allowable capacities of the shield TBM. From the analysis of TBM advance data, approximately 95% of field data showed the cutter penetration depth below 7 mm/rev. In addition, it was certified that the acting forces of every disc cutter, TBM thrust and torque during TBM driving were within the allowable capacities of the shield TBM and its disc cutters. When real acting forces of the disc cutters in the field were compared with those predicted by the CSM model, they showed the close relationships with each other even though the predictions by the CSM model were approximately 22~25% higher than field data.

• Tunnel and Underground Space
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• v.30 no.3
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• pp.214-225
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• 2020

Uniaxial compressive strength (UCS) of rock is one of the important factors to determine the advance speed during shield TBM tunnel excavation. UCS can be obtained through the Geotechnical Data Report (GDR), and it is difficult to measure UCS for all tunneling alignment. Therefore, the purpose of this study is to predict UCS by utilizing TBM machine driving data and machine learning technique. Several machine learning techniques were compared to predict UCS, and it was confirmed the stacking model has the most successful prediction performance. TBM machine data and UCS used in the analysis were obtained from the excavation of rock strata with slurry shield TBMs. The data were divided into 8:2 for training and test and pre-processed including feature selection, scaling, and outlier removal. After completing the hyper-parameter tuning, the stacking model was evaluated with the root-mean-square error (RMSE) and the determination coefficient (R²), and it was found to be 5.556 and 0.943, respectively. Based on the results, the sacking models are considered useful in predicting rock strength with TBM excavation data.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.3
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• pp.219-237
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• 2020

Rapid economic development and urban population growth have been increasing the necessity for underground space exploration and utilization due to the need of upgrading and expanding the existing infrastructures. TBM has been widely used to construct underground structures with high advance rate and minimal ground disturbance. Two important design parameters, which are available thrust capacity and cutterhead torque, should be estimated for any project in addition to proper selection of TBM type. However, the conventional thrust force and torque estimation model only depends on the empirical equation, which hinders the design process of the optimal thrust hydraulic system and the appropriate hydraulic components. In this study, four thrust and torque calculation models are derived and explained. For TBM design practice, the four estimation models are compared and discussed.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.528-546
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• 2018

Cases of TBM tunnelling have been consistently increasing worldwide. In many recent subsea and urban tunnelling projects, TBM excavation has been preferably considered due to its advantages over drill and blast tunnelling. Difficult ground conditions are highly probable to appear in subsea and urban tunnels because of the shallow working depth and alluvial characteristics. Under the difficult ground conditions, ground reinforcement measures should be considered including grouting, while it is of great importance to select the optimal grout material and injection method to cope with the ground condition. The benefits from TBM excavation, such as fast excavation, increased safety, and reduced environmental impact, can be achieved by applying appropriate ground reinforcement with the minimum overrun of cost and time. In this report, various grouting methods were reviewed so that they can be applied in difficult ground conditions. In addition, domestic and international cases of successful ground reinforcement for difficult grounds were introduced for future reference.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.3
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• pp.261-275
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• 2020

When excavating a small cross-section tunnel in a fault fracture zone using the shield TBM method, there is a high possibility of excessive convergence and collapse. Appropriate ground reinforcement is required to minimize construction cost loss and trouble due to a fault fracture zone. In this study, the optimal reinforcement area was suggested and the surrounding ground behavior was investigated through numerical analysis using MIDAS GTS NX (Ver. 280). For the parameters, the width of the fault fracture zone, the existence of fault gouge, and the groundwater level and depth of cover were applied. As a result, when there is not fault gouge, the convergence and ground settlement are satisfied the standard when applying ground reinforcement by up to 0.5D. And, due to the high permeability coefficient, it is judged that it is necessary to apply 0.5D reinforcement. There is a fault gouge, it was possible to secure stability when applying ground reinforcement between the entire fault fracture zone from the top of the tunnel to 0.5D. And, because the groundwater discharge occurred within the standard value due to the fault gouge, reinforcement was unnecessary.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.6
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• pp.531-555
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• 2011

This study aims to derive the statistical models for the estimation of the required specifications of a rock TBM as well as for its cutterhead design suitable for a given rock mass condition. From a series of multi-variate regression analysis of 871 TBM driving data and 51 linear rock cutting test results, the optimum models were newly proposed to consider a variety of rock properties and mechanical cutting conditions. When the derived models were applied to two domestic shield tunnels, their predictions of cutter penetration depth, cutter acting forces and cutter spacing were very close to real TBM driving data, showing their high applicability.