• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.3
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• pp.243-254
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• 2024

Currently, due to industrial development in domestic regions, buildings are saturated not only in major city centers but also in surrounding urban areas. Accordingly, people's attention has focused on underground spaces, and tunnels are being widely used, especially in urban development. Research on tunnels and tunnel excavation methods is actively underway. However, there is a lack of research on the wear and tear problems of sludge discharge pipes when using a slurry shield TBM. Therefore, in this paper, the L-shaped bend pipe used in the existing sludge discharge pipe was transformed into a T-shaped bend pipe to move sludge. As a result, it was confirmed that compared to the L-shaped bend pipe, the impact of the T-shaped bend pipe on the bend pipe when discharging sludge was reduced. Based on these results, it is expected that wear of the sludge discharge pipe can be minimized by using a T-shaped bend pipe when using slurry shield TBM equipment. This is expected to ultimately lead to economic benefits, such as reducing costs due to replacement of curved pipes or additional welding during tunnel construction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.321-331
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• 2013

This paper describes the evaluation of shield TBM disc cutter penetration depth in practice. In this study the disc cutter penetration depth used to design the excavation speed of tunnel is reviewed. The characteristics of ground encountered in the investigation site are analysed and evaluated. The shield TBM used in the field is reviewed to verify the applicability of machine in the site. The thrust and torque capacities of each TBM disc cutter are also evaluated. Based on the field data, the excavation volume and speed are re-analysed to evaluate the disc cutter penetration depth used in the design stage. It is clearly found that the design value of disc cutter penetration depth needs to modify when estimation of the TBM capacities in very hard rock formation ($S_c$ >150 MPa).

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.3
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• pp.233-242
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• 2011

This study aims to evaluate the applicability of high-strength concrete mixed with blast furnace slag to shield segment lining in order to improve its performance and economic efficiency. Especially, it was also intended to derive the optimum replacing ratio of ground granulated blast furnace slag to ordinary cement as well as the optimum steam curing condition for shield segment concrete with the design strength of 60 MPa. From a series of experiments, the condition of 50% replacement of ordinary cement by ground granulated blast furnace slag and unit water content of 125 kg/$m^3$ was proposed as the optimum mixing condition. Comparing with standard curing conditions, it was also possible to expect approximately 110~442% strength improvement of concrete by steam curing in the same mixing condition.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.163-176
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• 2017

The Discrete Element Method (DEM) has been widely used in civil engineering as well as various industrial fields to simulate granular materials. In this study, DEM was adopted to predict the performance of the face plate-type earth pressure balance (EPB) shield TBM (Tunnel Boring Machine). An analysis of the TBM excavation performance was conducted according to two pre-defined excavation conditions with the different rotation speeds per minute (RPM) of the cutterhead. The TBM model which was used in this study has a 6.64 m of diameter and six spokes. Also, 37 precutters and 98 scrapers at an each spoke were modeled with a real-scale specification. From the analysis, compressive forces at the cutterhead face, shield and cutting tools, resistant torques at the cutterhead face, muck discharge rate and accumulated muck discharge by the screw auger were measured and compared.

• Geomechanics and Engineering
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• v.37 no.1
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• pp.73-84
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• 2024

Owing to the high strength and abrasive characteristics of cobble-boulders, cutters are easily worn and damaged during shield tunneling, making construction inefficient. In the present work, the stress on the ripper and scraper on the cutterhead was analyzed by the PFC3D-FLAC3D coupling model of shield tunneling to get insight into the performance of the cutterhead for cutting underground cobble and boulders. The numerical calculation results revealed that the increase in trajectory radius leads to a rising stress on the cutters, and the stress on the front cutting surface is greater than that on the back of the cutters. Moreover, the correlation between cutter wear and stress is revealed based on field measurement data. The distribution of the cutter stress is consistent with the cutter wear and breakage characteristics in actual construction, in which more extensive cutter stress is exhibited, extreme cutter wear appears, and more cutter breakage occurs. Finally, the relationship between the cutterhead opening area's layout and cutter wear distribution was investigated, indicating that the cutter wear extent is the most severe in the region where the radial opening ratio dropped sharply.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.4
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• pp.519-534
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• 2019

Mechanized tunneling methods, including shield TBM, have been increasingly used for tunnel construction because of their relatively low vibration and noise levels as well as low risk of rock-falling accidents. In the excavation using the shield TBM, it is important to design penetration rate appropriately. In present study, both subsurface investigation data and shield TBM excavation data, produced for and during ${\bigcirc}{\bigcirc}{\sim}{\bigcirc}{\bigcirc}$ high-speed railway construction, were analyzed and used to compare with shield TBM penetration rates calculated using existing penetrating rate prediction models proposed by several foreign researchers. The correlation between thrust force per disk cutter and uniaxial compressive strength was also examined and, based on the correlation analysis, a simple prediction model for penetration rate was derived. The prediction results using the existing prediction models showed approximately error rates of 50~500%, whereas the results from the simple model proposed from this study showed an error rate of 15% in average. It may be said, therefore, that the proposed model has higher applicability for shield TBM construction in similar ground conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.1
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• pp.1-12
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• 2016

When utilizing a Tunnel Boring Machine (TBM) for tunnelling work, unexpected ground conditions can be encountered that are not predicted in the design stage. These include fractured zones or mixed ground conditions that are likely to reduce the stability of TBM excavation, and result in considerable economic losses such as construction delays or increases in costs. Minimizing these potential risks during tunnel construction is therefore a crucial issue in any mechanized tunneling project. This paper proposed the potential risk events that may occur due to risky ground conditions. A resistivity survey is utilized to predict the risky ground conditions ahead of the tunnel face during construction. The potential risk events are then evaluated based on their occurrence probability and impact. A TBM risk management system that can suggest proper solution methods (measures) for potential risk events is also developed. Multi-Criterion Decision Making (MCDM) is utilized to determine the optimal solution method (optimal measure) to handle risk events. Lastly, an actual construction site, at which there was a risk event during Earth Pressure-Balance (EPB) Shield TBM construction, is analyzed to verify the efficacy of the proposed system.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.3
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• pp.323-345
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• 2019

It is essential to predict ground conditions ahead of a tunnel face in order to successfully excavate tunnels using a shield TBM. This study proposes a forward prediction method for a mixed soil ground and/or a ground containing core stones by using electrical resistivity and induced polarization exploration. Soil conditioning in EPB shield TBM is dependent upon the composition of mixed soils; a special care need to be taken when excavating the core-stoned soil ground using TBM. The resistivity and chargeability are assumed to be measured with four electrodes at the tunnel face, whenever the excavation is stopped to assemble one ring of a segment lining. Firstly, the mixed ground consisting of weathered granite soil, sand, and clay was modeled in laboratory-scale experiments. Experimental results show that the measured electrical resistivity considerably coincides with the analytical solution. On the other hand, the induced polarization has either same or opposite trend with the measured resistivity depending on the mixed ground conditions. Based on these experimental results, a method to predict the mixed soil ground that can be used during TBM tunnel driving is suggested. Secondly, tunnel excavation from a homogeneous ground to a ground containing core stones was modeled in laboratory scale; the irregularity of the core stones contained in the soil layer was modeled through random number generation scheme. Experimental results show that as the TBM approaches the ground that contains core stones, the electrical resistivity increases and the induced polarization fluctuates.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.329-336
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• 2008

Efficient traffic network is required in urban area for good living condition. However, dense traffic network creates traffic jam and gives bad influences to the ground environment. Therefore, advanced use of underground and tunnel is required. But, in the last 20 years many tunnel fire accidents have occurred all over the world. Increase of tunnels and increase of traffics result in increase of tunnel fire. Tunnel fire creates damage to people and to the tunnel structure. Also, tunnel fire creates a big economical loss. In a mountain tunnel, the stability of the tunnel will not be disturbed by fire although the tunnel lining will get a severe damage. However, in a shield tunnel or immersed tube tunnel, cut and cover tunnel, there is a high possibility that tunnel itself will collapse by fire because their tunnel concrete lining is designed as a structural member. The aim of this experimental research is to verify the fire protection performance of newly developed cementitious material compared with the broadly used existing products in Europe and Japan. For the experiments, the general NATM tunnel concrete linings with the newly developed material were tested using fire loading curve of RABT (Maximum peak temperature is $1,200^{\circ}C$) and RWS (Maximum peak temperature is $1,350^{\circ}C$). From the test results, the newly developed fire protection material applied with 30 mm thickness showed good fire-proofing performance under RABT fire loading.

• The Journal of the Convergence on Culture Technology
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• v.6 no.3
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• pp.369-375
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• 2020

The section of this study is the geological vulnerable zone where groundwater leakage occurred through the tunnel barrier during excavation of the shield tunnel boring machine(TBM) for the construction of the electric power unit. Therefore, a Three D imensions(3D) numerical analysis was performed to analyze the actual situation from before construction to the time when the change in groundwater level occurred, and to reflect the surrounding ground conditions based on the observed change in groundwater level during construction. As a result of the study, the correlation between groundwater level change and tunnel construction around the site was identified. Therefore, it was similar to the measurement result of groundwater level at the target ground. The amount of groundwater discharge to the entrance of the tunnel construction was also similar to the actual measured result, and the numerical analysis method and modeling in this study were analyzed to reflect the site conditions.