• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1039-1048
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• 2018

In urban tunnel construction, most of the Shield TBM method is applied to secure the safety of buildings and to minimize risks. On the other hand, in the urban development process, landfills are often embanked or improving in many cases, so that the boundary between the surface and the rock is often heterogeneous. In case of ground condition such as alluvial soil, granite, decomposed granite, core stone and rock with various layers, datas on shield TBM advancing according to each ground condition are analyzed, The characteristics of machine load were compared and analyzed. As a result, it can be predicted that the change of ground condition can be predicted by the tendency of discharge volume, thrust force and cutting wheel torque when the cutter is checked and replaced regularly on advancing under maintaining the design slurry pressure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.3
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• pp.277-292
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• 2012

This paper presents the fundamental study on drag force of shield TBM cutter bit by scaled model test. Several theoretical analyses of the drag force of cutter bit have been studied. However, there are still some difference between the theoretical approaches and actual drag bit capacity. In order to study the drag forces of shield TBM cutter bit, the scaled model tests are carried out and analyzed. The results obtained from scaled model tests are compared with the existing theoretical equations. It is highly expected that the results of this study will be very essentially useful to design and develope the TBM cutterhead.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.125-133
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• 2014

In this study, TBM selection methods to meet soil and site conditions were presented. Factors and excavation equipment affecting TBM selection by soil and environmental condition were selected and classified. Weights between equipment and influencing factors selected were calculated by applying the AHP (Analytic Hierarchy Process) method. The results of the analysis influence factors, Ground condition was a major factor in objective factors and strength was a major factor in the hard condition of criteria factors and water pressure was a major factor in the soft ground condition of criteria factors. In Environment condition, existence of adjacent structures was evaluated more important than existence of feasible site. Lastly, Adequacy was verified through the deduction of results that coincide with input equipment by applying derived weights to actual site conditions.

• Journal of the Korean GEO-environmental Society
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• v.19 no.3
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• pp.35-45
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• 2018

It is essential to predict ground conditions ahead of the tunnel face during tunnel excavation. Various studies on tunnel prediction method of the ground condition ahead of the tunnel face have already been done and applied to in mechanized tunnelling job sites. So, all the methods used in mechanized tunnelling to predict ground conditions ahead of the tunnel face were reviewed. A questionnaire surveying Tunnel Boring Machine (TBM) operators with at least 10 years' experience in TBM operation was used to determine the requirements for prediction methods as well as the distance from the tunnel face that must be assessed. Based on the result of questionnaire survey, the most feasible prediction methods applicable to mechanized tunnelling job-sites are suggested. One of the prediction methods applicable to mechanized tunnelling job-sites might be the electrical resistivity survey by utilizing the disk cutter on the cutterhead as electrode. So, in this study, laboratory tests were performed to evaluate the feasibility of prediction method utilizing electrical resistivity survey at mechanized tunnelling job-sites. It was found that geological condition ahead of 0.3 times of TBM's diameter from tunnel face could be predicted.

• Tunnel and Underground Space
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• v.17 no.3 s.68
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• pp.225-233
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• 2007

Because of Norwegian topography as valleys and fjords, a large number of tunnels has been built and 59 of them have been excavated by TBM for last 30 years. Prognosis technology has been developed and improved through lots of TBM experiences, and the NTNU prediction model has been completed. This paper focuses the improvement of net penetration rate and advance rate in 14 Norwegian and 4 Koran TBM tunnelling sites of which data were reported. Through this period, net penetration rate as well as advance rate were increased to double with the improvement of disc cutter size and cutter arrangement in Norway. These rates in Korea were also increased for 15 years even though the rates were lower compared to Norwegian. It is estimated that these low rates were mainly caused by using disc cutters less than 17 inch diameter. It is expected that net penetration rate and advance rate can be increased by improvement of machine and tunnelling technology, especially by using 17 or 19 inch of the disc cutter size in the Korean full face mechanical tunnelling site.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.469-483
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• 2018

Steel bars have been widely used as the primary reinforcement for Precast Segmental Concrete Lining for TBM Tunnels. Previously, studies have been carried out to gauge the potential for steel fiber reinforcement to replace the use of steel bar reinforcements in the segmental lining to reduce the amount of the steel bar reinforcement. Steel fiber reinforcements have been investigated and widely applied to SFRC TBM linings to improve the constructability of SFRC TBM linings worldwide. However, the steel fiber reinforcement often caused punctures to the water membranes inside tunnel lining and had long-term durability deterioration issues caused by steel corrosion, as well as cosmetic problems. Therefore, this paper sought to gauge the potential of synthetic fiber reinforcements, which have proven to be very attractive substitutes for steel fiber reinforcements. This study analyzed the performance of both steel and synthetic fiber reinforcements in segmental linings and evaluated the applicability of the fiber reinforcements to the TBM Precast Concrete Segmental Linings of TBM tunnels. As a conclusion, this study demonstrates that the potential use of steel and synthetic fibers in various combination, can substitute the rebar reinforcement in the concrete mix for segmental concrete linings.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.6
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• pp.623-641
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• 2020

About 5 km length of tunnels were constructed by mechanized tunnelling method using closed type shield TBM. In order to avoid construction delay problems for ensuring timely electricity transmission, it is necessary to increase the prediction accuracy of the excavation process involving machines according to rock mass types. This is important to corroborate the project duration and optimum operation for various considerations involved in the machine. So, full-scale tunnelling tests were performed for developing the advance rate model to be appropriately used for 3.6 m diameter shield TBM. About 100 test cases were established and performed using various operational parameters such as thrust force and rotational speed of cuttterhead in representative uniaxial compressive strengths. Accordingly, relationships between normal force and penetration depth and, between UCS and torque were suggested which consider UCS and thrust force conditions according to weathered, soft, hard rocks. Capacity analysis of cutterhead was performed and optimum operational conditions were also suggested based on the developed model. Based on this study, it can be expected that the project construction duration can be reduced and users can benefit from the provision of earlier service.

• 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.20 no.4
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• pp.687-699
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• 2018

The construction of subsea tunnel differs from that of inland tunnel because of high water pressure due to sea water level and difficulties to reinforce the ground under construction. Therefore, it is very important to prevent trouble in advance when the subsea tunnel is constructed. In this paper, we established lots of databases about characteristics of geological and mechanical parameters on the construction of subsea tunnel using micro slurry TBM which depth is about 60 m. The correlation analysis is conducted to confirm the effect of thrust, torque and RPM among the excavation database on the net penetration rate. Also, An empirical formula is suggested to predict the net penetration rate through the correlation analysis between FPI (Field Penetration Index) and specific energy from the subsea tunnel excavation database.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.4
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• pp.285-303
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• 2023

Interest in building underground spaces is increasing for the creation of downtown infrastructure and efficient space utilization. A representative method of utilizing underground space is a tunnel, and in addition to road tunnels, the construction of utility tunnels such as power conduits and utility conduits is gradually increasing. The current basic tunnel construction method can be divided into NATM (New Austrian Tunnelling Method) and TBM (Tunnel Boring Machine). The NATM is a reliable method, but it is accompanied by vibration and noise due to blasting. In the case of the TBM excavation method, there are disadvantages in terms of construction period and construction cost, but it is possible to improve economic feasibility by introducing appropriate complementary methods. In this study, a blasting method was develop using the NATM after TBM pre-excavation using the protective shield method. This is a method that compensates for the disadvantages of each tunnel construction method, and is expected to reduce construction costs, blasting vibration, and noise. In order to review the performance of the developed method, an experiment was conducted to evaluate the performance of explosion-proof tube to which a protective shield scale model was applied, and the impact of blasting vibration of the protective shield method was analyzed.