• Journal of the Korean Geotechnical Society
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• v.22 no.6
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• pp.27-40
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• 2006

Damage of cut-and-cover tunnel lining can be attributed to physical and mechanical factors. Physical factors include material property, reinforcement corrosion, etc. while mechanical factors include underground water pressure, vehicle loads, etc. This study is limited to the modeling of rigid circular cut and cover tunnel constructed at a depth of $1.0{\sim}1.5D$ in loose sandy ground and subjected to a vibration frequency of 100 Hz. In this study, only damages due to mechanical factors in the form of additional loads were considered. Among the different types of additional, excessive earth pressure acting on the cut-and-cover tunnel lining is considered as one of the major factors that induce deformation and damage of tunnels after the construction is completed. Excessive earth pressure may be attributed to insufficient compaction, consolidation due to self-weight of backfill soil, precipitation and vibration caused by traffic. Laboratory tunnel model tests were performed in order to determine the earth pressure acting on the tunnel lining and to investigate the applicability of existing earth pressure formulas. Based on the difference in the monitored and computed earth pressure, a factor of safety was recommended. Soil deformation mechanism around the tunnel was also presented using the picture analysis method.

• 도로교통
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• s.98
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• pp.57-75
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• 2004

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.489-501
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• 2017

The collapse accidents during a open ground excavation in urban areas not only lead to human injuries and material damages in the construction site, but also lead to road sinks and damages to the adjacent facilities due to settlement of ground around the construction site. Therefore, during a open ground excavation in the urban areas, it is necessary to thoroughly prepare for prevention of collapse accidents, and consider whole construction stage such as planning, design and construction. In this study, the priorities to be managed mainly were obtained in order to prevent collapse accidents during a open ground excavation. After analyzing results from past accidents cases for open ground excavations, priorities were evaluated regarding collapse-inducing elements using the Delphi technique which is a decision-making method by consensus among experts. As a result, insufficient groundwater treatment, bad geotechnical investigation and instability on construction, etc. were obtained as priorities for prevention of collapse accidents.

• Magazine of korean Tunnelling and Underground Space Association
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• v.14 no.2
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• pp.67-76
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• 2012

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.177-186
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• 2005

World widely, the occurrences of earthquakes have been increased recently including to nations which earthquake often happen to like Japan. Taking into account that the earthquake acceleration at design was 0.154 g at the contigency level earthuake (CLE) with its geological condition, it resulted that this method must be the most efficient condition against the earthquake vibration to two lane cut-and cover tunnel. The correlations between the result of the shaking table test and its numerical analysis showed that the test data of the bending stress due to the earthquake vibration have been underestimated about 5 percents in case of the cut slope 1 : 0.6 and about 10 percent in case of the cut slope 1 : 1.2. However, on average, the results showed a similar tendency that the higher the height of the backfill of the EPS block was, the less the bending stress was.

• 지반과기술
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• v.2 no.2
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• pp.45-48
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• 2005

• 지반과기술
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• v.6 no.4
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• pp.50-50
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• 2009

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.237-250
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• 2015

Underground structures such as a tunnel have been considered as safer than structures on the ground during earthquake. However, severe damages of underground structures occurred at subway tunnel during 1995 Kobe Earthquake and such damages are gradually increased. In this study, a dynamic behavior of a cut and cover tunnel surrounded by weathered soils is investigated using Mohr-Coulomb Model. Parametric study was carried out for boundary conditions, tensile strength, and earthquake magnitudes. The results of numerical analyses in terms of ground deformations and stresses acting on the lining were quite dependent on the side boundary condition (free or fix conditions) and tensile strength of surrounding soils. The ground was deformed upward at the end of earthquake when the side boundary condition was fixed, whereas residual deformations were not predicted when it was free. When the tensile strength of a soil was set to the same as its cohesion, residual deformation was less than 1cm, regardless of side boundary conditions or input accelerations. In addition to that, stress conditions at the maximum deformation and end of earthquake were within an allowable range and considered as safe. Proper boundary conditions and material properties such as tensile strength are quite important because they may significantly impact on the results of dynamic analyses.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.25-40
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• 2007

Excessive earth pressure is one of the major mechanical factors in the deformation and damage of Cut-and-Cover Tunnel lining in shallow tunnels and portals of mountain tunnels (Kim, 2000). Excessive earth pressure may be attributed to insufficient compaction and consolidation of backfill material due to self-weight, precipitation and vibration caused by traffic (Komiya et al., 2000; Taylor et al., 1984; Yoo, 1997). Even though there were a lot of tests performed to determine the earth pressure acting on the tunnel lining, unfortunately there were almost no case histories of studies performed to determine remedial measures that reduce differential settlement and excessive earth pressure. In this study the installation of geotextile mat was selected to reduce the differential settlement and excessive earth pressure acting on the cut-and-cover tunnel lining. In order to determine settlement and earth pressure reduction effect (reinforcement effect) of geotextile mat reinforcement, laboratory tunnel model tests were performed. This study was limited to the modeling of rigid circular cut-and-cover tunnel constructed at a depth of $1.0D\sim1.5D$ in loose sandy ground and subjected to a vibration frequency of 100 Hz. Model tests with varying soil cover, mat reinforcement scheme and slope roughness were performed to determine the most effective mat reinforcement scheme. Slope roughness was adjusted by attaching sandpaper #100, #400 and acetate on the cut slope surface. Mat reinforcement effect of each mat reinforcement scheme were presented by the comparison of earth pressure obtained from the unreinforced and mat reinforced model tests. Soil settlement reduction was analyzed and presented using the Picture Analysis Method (Park, 2003).

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.456-461
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• 2011

Recently the design specification has been advanced with preventing earthquake disaster in Korea because of increasing occurrence of large size earthquake. A composite plate with ductile fiber is proposed, which can enhance the performance of built tunnel in both strength and ductility. This study is to focus to verify the effect of strengthening of existing tunnels which is built without earthquake type load scenario, so that it can provide the safety of existing urban subway system against earthquakes.