• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.735-747
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• 2019

Due to the lack of ground space by urbanization, the demand of utility tunnels for laying social facilities is increasing. During the construction of a utility tunnel in downtown area using a shield TBM, various problems may occur when difficult ground is encountered such as mixed ground and cobbly ground. Thus, in this study, using MIDAS GTS NX (Ver. 280), a numerical analysis was performed on characteristics of difficult ground, reinforced area, depth of cover and groundwater level to analyze the optimal ground reinforced area according to combination of parameters. As a result, it was difficult to secure stability in unconstrained excavation cases on both the mixed ground and the cobbly ground. However, when ground reinforcement grouting as much as 2.0D is applied, convergence occurred within the allowable limit, except for mixed ground with a depth of cover 30 m. In addition, excessive leakage occurred during excavation of both the mixed ground and the cobbly layers. It was able to secure stability after applying waterproof grouting.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.3
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• pp.281-301
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• 2024

The power cable tunnels which are part of the underground transmission line project, are constructed using the shield TBM method. The disc cutter among the shield TBM components plays an important role in breaking rock mass. Efficient tunnel construction is possible only when appropriate replacement occurs as the wear limit is reached or damage such as uneven wear occurs. A study was conducted to determine the wear conditions of disc cutter using a deep learning algorithm based on real-time measurement data of wear and rotation speed. Based on the results of full-scaled tunnelling tests, it was confirmed that measurement data was obtained differently depending on the wear conditions of disc cutter. Using real-time measurement data, an algorithm was developed to determine disc cutter wear characteristics based on a convolutional neural network model. Distributional patterns of data can be learned through CNN filters, and the performance of the model that can classify uniform wear and uneven wear through these pattern features.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.861-874
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• 2019

A great interest in the seismic performance evaluation of small size tunnel structures such as utility tunnel has been taken since recent earthquakes at Pohang and Gyeongju in Korea. In this study, the three-dimensional dynamic analyses of vertical shaft and horizontal tunnel under seismic load were carried out using FLAC3D. Especially, parametric analyses was performed to investigate the effects of interfacial stiffness on interfacial behavior between soil and structure. The parametric analysis showed that the interfacial stiffness scarcely gave an effect on the global dynamic behavior of the structure, while had a significant effect on the local displacement behavior of the connections. The magnitude of the interfacial stiffness was inversely proportional to the displacement, while the magnitude of interface stiffness was proportional to the normal and shear stresses. The results of this study suggest the limitations of the existing empirical equations for interfacial stiffness and emphasize the need to develop new interfacial stiffness models.