• Explosives and Blasting
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• v.41 no.4
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• pp.9-16
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• 2023

To compare the global warming impact of the TBM and NATM method, which are representative tunnel excavation methods, a life cycle assessment was performed for each method. Life cycle assessment should compare the sum of carbon emissions by considering the pre-manufacturing stage, product manufacturing stage, usage stage, and disposal stage. However, access to TBM (Tunnel Boring Machine) manufacturing and disposal data is limited, so I had no choice but to focus on the analysis for the usage stage. In general, carbon emissions during the pre-product manufacturing stage and product manufacturing stage often exceed 90% of carbon emissions throughout the entire process. Therefore, since it is difficult to achieve the analysis goal only by comparing the usage stage, the analysis scope was expanded, and carbon emissions for the process were calculated for the NATM method with access to manufacturing data. As a result of comparing the relative impact on global warming, the carbon emissions of the TBM method were found to be higher than those of the NATM method even though TBM method was only considered for the usage stage. So there it is, the NATM method can be seen as environmentally friendly in the future when considering the impact of climate change (global warming), which has recently attracted attention among environmental impact fields.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.6
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• pp.599-614
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• 2014

When tunnelling with TBM (Tunnel Boring Machine), accessibility to tunnel face is very limited because tunnel face is mostly occupied by a bunch of machines. Existing techniques that can predict ground condition ahead of TBM tunnel are extremely limited. In this study, the TBM Resistivity Prediction (TRP) system has been developed for predicting anomalous zone ahead of tunnel face utilizing electrical resistivity. The applicability and prediction accuracy of the developed system has been verified by performing field tests at subway tunnel construction site in which an EPB (Earth Pressure Balanced) shield TBM was used for tunnelling work. The TRP system is able to predicts the location, thickness and electrical properties of anomalous zone by performing inverse analysis using measured resistivity of the ground. To make field tests possible, an apparatus was devised to attach electrode to tunnel face through the chamber. The electrode can be advanced from the chamber to the tunnel face to fully touch the ground in front of the tunnel face. In the 1st field test, none of the anomalous zone was predicted, because the rock around the tunnel face has the same resistivity and permittivity with the rock ahead of tunnel face. In the 2nd field test, 5 m thick anomalous zone was predicted with lower permittivity than that of the rock around the tunnel face. The test results match well with the ground condition predicted, respectively, from geophysical exploration, or directly obtained either from drilling boreholes or from daily observed muck condition.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.4
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• pp.415-428
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• 2015

With increase of the extension of long tunnels and urban tunnelling, demands on the new tunnelling technologies are raised. Currently, drilling and blasting tunnel construction method is mostly used, however, because of sever blast vibration for some occasions, complaints from local residents and rock damages are inevitable. Accordingly, TBM tunnelling is more efficient and effective for such conditions. Nevertheless, tunnel construction costs of TBM cannot compete that of the drill and blasting method in Korea. To overcome such limitations, various TBM equipments and construction technologies are required. In addition, continuous revision of the design standard and specification are required. In this study, a detailed explanation regarding the revised version of TBM section in the tunnel standard specification at 2015 is shown.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.04a
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• pp.47-60
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• 1998

It is considered in this paper that the main causes of tunnel collapse during the construction were the insufficiency of data of geotechnical investigations, or their limits due to special ground condition such as its heterogeneity and anisotropy It is thought that safety of ground can be affected by the geological conditions such as presences of discontinuities in good intact rocks, and considered to be necessary that awareness of the conditions of discontinuities in advance is important to apply adequate reinforcement measures. It is also shown that a serious accident had occurred because of the unawareness of the permeable alluvial deposits at the top of the tunnel. And it is shown that the example of application of the results of geotechnical investigation such as face-mapping, pilot boring etc. during tunnel construction, and a serious deformation of tunnel under special geological condition. Therefore, it is strongly recommended to perform an adequate geotechnical investigation to confirm the geotechnical conditons of ground before design, and supplimentary investigation is also needed depending on conditions for safe and econonic construction.

• Tunnel and Underground Space
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• v.31 no.1
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• pp.1-9
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• 2021

Recently, the development of underground space has been accelerated with rapid urbanization, and it is significantly important for safe construction to accurately understand the geological conditions of the section when excavating rocks. In this paper, a boring alignment tracking and geological exploration system have been developed to identify the geological conditions beyond the excavation face by utilizing a MSP method that bores a large empty hole to reduce blast-induced vibration. The major advantage of the proposed exploration system is that we can obtain the ground condition of 50 m ahead of the excavation face through exploration along blast cut-holes drilled for the NATM tunnel construction. In addition, we introduce several case histories regarding the assessment of the geological conditions beyond the tunnel face by monitoring the inside of large empty holes using the proposed hole exploration system.

• Tunnel and Underground Space
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• v.34 no.2
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• pp.143-153
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• 2024

Tunnel Boring Machine (TBM) method is a tunnel excavation method that produces lower levels of noise and vibration during excavation compared to drilling and blasting methods, and it offers higher stability. It is increasingly being applied to tunnel projects worldwide. The disc cutter is an excavation tool mounted on the cutterhead of a TBM, which constantly interacts with the ground at the tunnel face, inevitably leading to wear. In this study quantitatively predicted disc cutter wear using geological conditions, TBM operational parameters, and machine learning algorithms. Among the input variables for predicting disc cutter wear, the Uniaxial Compressive Strength (UCS) is considerably limited compared to machine and wear data, so the UCS estimation for the entire section was first conducted using TBM machine data, and then the prediction of the Coefficient of Wearing rate(CW) was performed with the completed data. Comparing the performance of CW prediction models, the XGBoost model showed the highest performance, and SHapley Additive exPlanation (SHAP) analysis was conducted to interpret the complex prediction model.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.153-163
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• 2005

This paper presents two case studies for tunnelling in Bangkok: a subway tunnel site and a flood diversion tunnel site. The first case study is related to ground displacement response for dual tunnel Bangkok MRT subway. The MRT subway project of Bangkok city consists of dual tunnels about 20 km long with 18 subway stations. The tunnels are seated in the firm first stiff silty clay layer between 15-22 m in depth below ground surface. The behavior of ground deformation response based on instrumentation is presented. The back analysis based on plain strain FEM analysis is also presented and agrees with field performance. The shear strain of FEM analysis is in the range of 0.1-1% and in accordance with the results of self boring pressuremeter tests. Meanwhile, the second case study is related to the EPB tunnelling bored underneath through underground obstruction. The Premprachakorn flood diversion tunnel is the shortcut tunnel to divert the flood water in rainy season into the Choapraya river. The tunnel was bored by means of EPB shield tunnelling in very stiff silty clay layer at about 20-24 m in depth. During flood diversion tunnel bored underneath the existing Bangkok main water supply tunnel and pile foundation of the bridge, instrumentation was monitored and compared with predicted FEM analysis. The prevention risk potential by means of predicting damage assessment is also presented and discussed.

• Tunnel and Underground Space
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• v.21 no.3
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• pp.151-163
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• 2011

The LCM test is one of the most powerful and reliable methods for designing the disc cutter and for predicting the TBM (Tunnel Boring Machine) performance. It has an advantage to predict the actual load on disc cutter from the laboratory test on the real-size large rock samples, however, it also has a disadvantage to transport and/or prepare the large rock samples and to need an extra cost for experiment. Moreover it is not easy to execute the test for jointed rock mass, and sometimes the design model estimated from the test can not be applied to the real design of disc cutter. In order to break this critical point, lots of numerical studies have been performed. PFC2D can simulate crack propagation and rock fragmentation effectively, because it is useful in particle flow analysis. Consequently, in this study, the PFC2D has been adopted for numerical analysis on cutting power of disc cutter according to the different angle of joint, the different direction of joint, and the different space of joint with jointed rock mass models. From the numerical analyses, it was concluded that the bigger cutting power of disc cutter was needed for reverse cutting direction to joint rather than for forward direction, and the cutting power of disc cutter was increased with decreasing the dip angle of joint and decreasing the space of joints in reverse cutting direction. The more precise numerical model for disc cutter can be developed from comparison between the numerical results and LCM test results, and the resonable guideline is expected for prediction of TBM performance and disc cutter.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.553-581
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• 2022

Shortly after tunnel boring machine (TBM) was introduced in the tunneling industry, the use of TBM has surprisingly increased worldwide due to its performance together with the benefit of being safely and environmentally friendly. One of the main cost items in the TBM tunneling in rock and soil is changing damaged or worn cutters. It is because that the cutter change is a time-consuming and costly activity that can significantly reduce the TBM utilization and advance rate and has a major effect on the total time and cost of TBM tunneling projects. Therefore, the importance of accurately evaluating the cutter life can never be overemphasized. However, the prediction of cutter wear in soil, rock including mixed face is very complex and not yet fully clarified, subsequently keeping engineers busy around the world. Various prediction models for cutter wear have been developed and introduced, but these models almost usually produce highly variable results due to inherent uncertainties in the models. In this study, a case study of design and construction of disc cutter change is introduced and analyzed, rather than proposing a prediction model of cutter wear. As the disc cutter is strongly affected by the geological condition, TBM machine characteristic and operation, authors believe it is very hard to suggest a generalized prediction model given the uncertainties and limitations therefore it would be more practical to analyze a real case and provide a detailed discussion of the difference between prediction and result for the cutter change. By doing so, up-to-date idea about planning and execution of cutter change in practice can be promoted.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.549-560
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• 2021

Forces exerted on a shield TBM (tunnel boring machine) such as cutter head torque, thrust force, chamber pressure, and upward force are key factors determining TBM performance. However, the forces acting on the TBM when tunnelling the mixed ground have different tendencies compared to that of the uniform ground, which could impair TBM performance. In this study, the effect of mixed ground tunnelling was numerically investigated with torque, thrust force, chamber pressure, and upward force. A coupled discrete element method (DEM) and finite difference method (FDM) model for TBM driving model was used. This numerical study simulates TBM tunnelling in mixed ground composed of upper weathered granite soil and lower weathered rock. The effect on the force acting on the TBM according to the location and slope of the boundary of the mixed ground was numerically examined.