• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.385-392
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• 2021

When ordering a slurry shield TBM to be used for power cable tunneling, the client organizes an evaluation committee composed of experts, suggest the criteria and evaluation method for technical specifications for supplier selection, and based on the manufacturer's technical proposal were attempted to evaluate and select. It is expected to be referred to as a guideline for future projects to using Shield TBM as one of the methods of verifying performance and quality in advance and securing economic feasibility in the shield TBM tunneling in the recent increasing trend.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.4
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• pp.355-364
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• 2016

Recently, a 3,250 meter-long tunnel was constructed beneath the sea bed formed of composite sedimentary soils to transport reusable waste heat gas of industrial complex in the west coast of Korea. Some risks such as machine settlement always exist due to the uncertainties of geological and construction factors during the subsea shield TBM tunnelling. In this construction site, the deviation of tunnel alignment caused by shield TBM settlement was occurred during excavation. It was examined that the lack of bearing capacity of soft clay was a main cause. This paper evaluates the risk of shield TBM tunnelling considering the ground conditions. Correlation between machine settlement and its advance rate was evaluated through the analytical equation in which bearing capacity is considered and a 3-D numerical analysis which can simulate the TBM advance condition (in other words, the dynamic condition). It was found out that a shield TBM could settle due to the insufficient bearing capacity of soft clay layers. In order to prevent such the problem, the best advance rate proper to the ground characteristics is needed to be applied. In the ground conditions of the section of interest, it was turned out that if the shield TBM advance rate was maintained between 35 mm/min and 40 mm/min, the machine settlement could be avoided.

• 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.16 no.2
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• pp.193-201
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• 2014

This paper presents the development of simulation system on EPB shield TBM Hood operation. In recent, EPB shield TBM is widely used in the tunnel construction. Since the hood system of the EPB shield TBM is most important to excavate the tunnel, it is necessary to perform the simulation of hood system to investigate the design and operation parameters prior to tunnel construction. In order to carry out this study, the scaled simulation system was designed and developed. The model tests were performed to verify the developed system. During the simulation, the earth pressures developed in the chamber during tunnelling were measured to evaluate the operation technique. The test results obtained by the developed simulation system show clearly the similar behaviour of TBM hood compared with the field data. It was also found that the ground loss during tunnelling is dependent on the change of earth pressure in chamber. Therefore, the simulation system developed in this study will be very useful to evaluate the operation technique of the TBM hood prior to tunnel construction. In addition, this system will be applied in a various condition of ground to get the operating information.

• 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.24 no.2
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• pp.217-230
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• 2022

The adequate control of TBM face pressure is of vital importance to maintain face stability by preventing face collapse and surface settlement. An EPB shield TBM excavates the ground by applying face pressure with the excavated soil in the pressure chamber. One of the challenges during the EPB shield TBM operation is the control of face pressure due to difficulty in managing the excavated soil. In this study, the face pressure of an EPB shield TBM was predicted using the geological and operational data acquired from a domestic TBM tunnel site. Four machine learning algorithms: KNN (K-Nearest Neighbors), SVM (Support Vector Machine), RF (Random Forest), and XGB (eXtreme Gradient Boosting) were applied to predict the face pressure. The model comparison results showed that the RF model yielded the lowest RMSE (Root Mean Square Error) value of 7.35 kPa. Therefore, the RF model was selected as the optimal machine learning algorithm. In addition, the feature importance of the RF model was analyzed to evaluate appropriately the influence of each feature on the face pressure. The water pressure indicated the highest influence, and the importance of the geological conditions was higher in general than that of the operation features in the considered site.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.65-85
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• 2023

The use of TBM (Tunnel boring machine) has increased worldwide due to its performance together with the benefit of being safely and environmentally friendly compared to conventional tunneling. In particular, EPB (Earth Pressure Balanced) TBM is widely used because it can be applied to various grounds compared to Open TBM. Also EPB TBM has a simple mechanical structure and advantages in cost, requires less ground area than Slurry TBM. EPB TBM has advantages in soft ground, and more importantly, can extend its applicability by use of appropriate soil conditioning, which improves mechanical and hydrological properties of excavated soil and increases the excavation performance of EPB TBM. Various studies suggested the proper mixing ratio and injection ratio, but almost they are limited to laboratory test under atmospheric pressure such as slump test. Actual field conditions may differ depending on the ground and mechanical condition. In this study, first the amount of used soil conditioning used in the field with various grounds from hard rock to soft ground was estimated through laboratory tests and compared with the estimate in design stage. And also it was compared with the amount used during actual excavation. In addition, experience of soil conditioning for the problems of cutter head clogging and groundwater inrush that occurred during excavation is discussed. Finally, lesson learned for the use of soil conditioning in difficult ground condition such as mixed ground are reviewed.

• 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.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.4
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• pp.611-634
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• 2017

In rapid urbanization, demand for utility tunnel increases more, and tunnel boring machine (TBM) has been used widely. Prediction of TBM penetration rate is important for proper estimation of construction period and cost. Although there are several methods, such as NTNU model and CSM model that require many input parameters, fundamental understanding on correlations between rock properties and TBM penetration rate is critical. In this study, we explored the brittleness indices of hard rocks according to various definitions, and the correlations between the brittleness indices and the TBM penentration rates.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.6
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• pp.611-622
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• 2020

Recently, tunneling projects using shield TBM are increasing in Korea, but the information of client for machine design and manufacturing considering the characteristics of the tunneling phase is not formal, and it is difficult to optimized machine for suitable tunneling works. This paper suggest as for reference the required terms that can be used in Korea on the design items and detailed requirements for ordering of EPB shield TBM based on overseas case study. It would be hope that the TBM user can request the overall tunneling plan and required machine specification when ordering TBM, and the TBM supplier can design and manufacturing that is clear condition and suitable machine for the successful project, so that there are no residential civil complaints and for safe tunneling as well, shield TBM tunneling method will be activated.