• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.213-229
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• 2017

Recently, in urban areas there is a tendency to construct more complex network-type tunnels including entrance and exit ramps. At the same time, various one-dimensional programs based on the network theory have been proposed for tunnel ventilation analysis. This paper aims at developing a program that can analyze the ventilation flow rate and pollutants concentration in complex network-type tunnels based on the none hardy-cross method. The flow analysis in the branch was carried out on the basis of the Gradient method, while for the concentration analysis a new logic has been developed to calculate the inflow and outflow concentration automatically in a complex network-type structure. Additionally, in the tunnel segments showing low flow rate, proper grid interval sizes were proposed to reduce numerical error. To verify the applicability of the program, flow rates predicted in the straight tunnels were compared with the classical velocity-diagram method by Stokic and the TVSDM program. The results showed that the errors were within 1%. In addition, the program was applied to the recent ventilation system adopted in the complex network-type urban tunnels.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.559-575
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• 2021

Due to the increase in ground excavation work, the possibility of ground subsidence accidents is increasing. And it is very difficult to prevent these risk fundamentally through institutional reinforcement such as the special law for underground safety management. As for the various cases of urban ground excavation practice, the ground subsidence behavior characteristics which is predicted using various information before excavation showed a considerable difference that could not be ignored compared to the results real construction data. Changes in site conditions such as seasonal differences in design and construction period, changes in construction methods depending on the site conditions and long-term construction suspension due to various reasons could be considered as the main causes. As the countermeasures, the safety management system through various construction information is introduced, but there is still no suitable system which can predict the effect of excavation and risk assessment. In this study, a web-based system was developed in order to predict the degree of impact on the ground subsidence and surrounding structures in advance before ground excavation and evaluate the risk in the design and construction of urban ground excavation projects. A system was built using time series analysis technique that can predict the current and future behavior characteristics such as ground water level and settlement based on past field construction records with field monitoring data. It was presented as a geotechnical data visualization (GDV) technology for risk reduction and disaster management based on web-based system, Using this newly developed web-based assessment system, it is possible to predict ground excavation impact prediction and risk assessment.

• 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.19 no.2
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• pp.335-353
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• 2017

This paper presents the application technique on thrust jacking pressuring of shield TBM in the sharp curved tunnel alignment by model tests. Recently, the application of shield TBM method as mechanized tunnelling is increasing to prevent the vibration and noise problems, which can be occurred in the NATM in the urban area in Korea. However, it is necessary to plan the sharp curved tunnel alignment in order to avoid the building foundation and underground structures, to develop the shield TBM operation technique in the shape curved tunnel alignment. Therefore, the main operation parameters of shield TBM in the curved tunnel alignment are reviewed and analyzed based on the case study and analytical study. The results show that the operation of shield jacking force system is the most important technique in the shape curved tunnel alignment. The simplified scaled model tests are also carried out in order to examine the ground-shield TBM head behaviour. The earth pressures acting on the head of shield TBM are investigated according to two different shield jacking force systems (uniform and un-uniform pressure) and several articulation angles. The results obtained from the model tests are analysed. These results will be very useful to understand the shield TBM head interaction behaviour due to the shield jacking operation technique in the shape curved tunnel alignment, and to develop the operation technique.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1105-1123
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• 2018

The main risk factors of tunnel excavation through urban areas are ground settlement and surface sink which caused by ground conditions, excavation method, groundwater condition, excavation length, support method, etc. In the process of ground settlement assessment, the numerical analysis should be conducted considering the displacement and stress due to tunnel excavation. Therefore a technique that can simplify such process and easily evaluate the influence of tunnel excavation is needed. This study focused on the tunnelling-induced ground settlement which is main consideration of underground safety impact assessment. The parametric numerical analyses were performed considering such parameters as ground conditions, tunnel depth, and lateral distance from tunnel center line, etc. A simplified ground settlement evaluation chart was suggested by analyzing tendency of ground subsidence, lateral influence area and character by depth. The applicability of the suggested settlement evaluation chart was verified by comparative numerical analysis of settlement characteristics.

• Explosives and Blasting
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• v.19 no.3
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• pp.91-104
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• 2001

As in Korean environments with mountainous and hilly areas, the rock generally has to be removed in construction or civil engineering work in tunnelling or excavation for development in urban area. Explosives should be used for blasting, which may cause serious problems on local people for their claim for compensation due to ground vibration, noise. For safe and economic blasting, geology and engineering characteristics of rocks such as discontinuities of rock or weathering are very important factors, together with site characteristics for prediction of ground vibration. In this study, conducted were the detailed study for major rocks most widely distributed in the South-east area, in-situ geological survey, geological and geochemical analysis, and further laboratory uniaxial rock stress, seismic velocity of core samples together with in-situ seismic velocity measurements. Regulations on ground vibration and noise were reviewed for assessing their adaptabilities, and a total of 4,856 measured blasting vibration data were examined for enhancing the confidence level in estimating the predictive formulation using scaled distance statistically.

• Geomechanics and Engineering
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• v.12 no.2
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• pp.185-195
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• 2017

With the rapid development of urban underground traffic, the study of soil deformation induced by subway tunnel construction and its settlement prediction are gradually of general concern in engineering circles. The law of soil displacement caused by shield tunnel construction of adjacent buildings is analyzed in this paper. The author holds that ground surface settlement based on the Gauss curve or Peck formula induced by tunnel excavation of adjacent buildings is not reasonable. Integrating existing research accomplishments, the paper proposed that surface settlement presents cork distribution curve characters, skewed distribution curve characteristics and normal distribution curve characteristics when the tunnel is respectively under buildings, within the scope of the disturbance and outside the scope of the disturbance. Calculation formulas and parameters on cork distribution curve and skewed distribution curve were put forward. The numerical simulation, experimental comparison and model test analysis show that it is reasonable for surface settlement to present cork distribution curve characters, skewed distribution curve characteristics and normal distribution curve characteristics within a certain range. The research findings can be used to make effective prediction of ground surface settlement caused by tunnel construction of adjacent buildings, and to provide theoretical guidance for the design and shield tunnelling.

• Geomechanics and Engineering
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• v.33 no.5
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• pp.463-475
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• 2023

Tunnel construction activity, conducted mainly in mountains and within urban centres, causes soil settlement, thus requiring the relevant management of slopes and structures as well as evaluations of risk and stability. Accordingly, in this study we performed a three-dimensional finite element analysis to examine the behaviour of piles and pile cap stability when a tunnel passes near the bottom of the foundation of a pile group connected by a pile cap. We examined the results via numerical analysis considering different conditions for reinforcement of the ground between the tunnel and the pile foundation. The numerical analysis assessed the angular distortion of the pile cap, pile settlement, axial force, shear stress, relative displacement, and volume loss due to tunnel excavation, and pile cap stability was evaluated based on Son and Cording's evaluation criterion for damage to adjacent structures. The pile located closest to the tunnel under the condition of no ground reinforcement exhibited pile head settlement approximately 70% greater than that of the pile located farthest from the tunnel under the condition of greatest ground reinforcement. Additionally, pile head settlement was greatest when the largest volume loss occurred, being approximately 18% greater than pile head settlement under the condition having the smallest volume loss. This paper closely examines the main factors influencing the behaviour of a pile group connected by a pile cap for three ground reinforcement conditions and presents an evaluation of pile cap stability.

• Geophysics and Geophysical Exploration
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• v.9 no.1
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• pp.108-113
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• 2006

Urban conditions, such as existing underground facilities and ambient noise due to cultural activity, restrict the general application of conventional geophysical techniques. At a tunnelling site in an urban area along an existing railroad, we used the refraction microtremor (REMI) technique (Louie, 2001) as an alternative way to get geotechnical information. The REMI method uses ambient noise recorded by standard refraction equipment and a linear geophone array to derive a shear-wave velocity profile. In the inversion procedure, the Rayleigh wave dispersion curve is picked from a wavefield transformation, and iteratively modelled to get the S-wave velocity structure. The REMI survey was carried out along the line of the planned railway tunnel. At this site vibrations from trains and cars provided strong seismic sources that allowed REMI to be very effective. The objective of the survey was to evaluate the rock mass rating (RMR), using shear-wave velocity information from REMI. First, the relation between uniaxial compressive strength, which is a component of the RMR, and shear-wave velocity from laboratory tests was studied to learn whether shear-wave velocity and RMR are closely related. Then Suspension PS (SPS) logging was performed in selected boreholes along the profile, in order to draw out the quantitative relation between the shear-wave velocity from SPS logging and the RMR determined from inspection of core from the same boreholes. In these tests, shear-wave velocity showed fairly good correlation with RMR. A good relation between shear-wave velocity from REMI and RMR could be obtained, so it is possible to estimate the RMR of the entire profile for use in design of the underground tunnel.

• 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.