• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.87-92
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• 2000

In excavation of tunnels especially located in shallow depth, it is not rare to meet geological change in excavation progress worse than expected in the initial design stage. This paper present a case study on the re-design of excavation and support system of a shallow tunnel under construction where it meets the unexpected bad geological condition during excavation. The detailed geological investigation shows that the rock mass is heavily weathered and fractured with RMR value less than 20. Considering this geological condition, the design concept is focused on the reinforcement of the ground preceding the excavation of tunnel. Two design patterns, LW-grouting & forepoling with pilot tunnelling method and the steel pipe reinforced grouting method, are suggested. Numerical analysis by FLAC shows that these two patterns give the tunnel and roof ground stable in excavation process while the original design causes severe failure zone around the tunnel and floor heaving. In point of the mechanical stability and the degree of construction, the steel pipe reinforced grouting technique proved to be good for the reinforcement of heavily fractured rock mass in tunnelling. This assessment and design process would be a guide in the construction of tunnels in heavily weathered and fractured rock mass situation.

• Economic and Environmental Geology
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• v.31 no.6
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• pp.527-534
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• 1998

Excavation of underground openings changes stress distribution around the opening. The survey of this disturbed zone in excavation is very important to design and construct underground facilities, such as tunnel, gas and oil storage, power plant and disposal site of high- and low-level radioactive wastes. This paper presents a zoning of rock masses with tunnel excavation using PS logging. Compressional and shear wave velocities are measured in boreholes drilled in the tunnel wall, which was constructed with blasting and/or machine excavation. The disturbed zone in excavation can be estimated by comparing PS logging data with a tomographic image of compressional wave velocity and compressional and shear wave velocities of core samples. In the side wall of tunnel, the disturbed zone reaches 1.5 m and 1.0 m in thickness for blocks of blasting and machine excavations, respectively. In the roof of tunnel, however, the disturbed zone is 1.0 m and 0.75 m thick for the two blocks. These results show that the width of the disturbed zone is larger in the side wall of tunnel than in the roof, and 1.3 to 1.5 times larger for the blasting excavation than for the machine excavation.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.115-123
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• 2007

Recently, accelerating population and advanced economy result in extending old freeways and constructing new freeways. To make a good freeway shape, tunnel constructions are also rapidly increasing. Therefore, a possibility of a collapse during a tunnel excavation is getting higher in a proportionate manner. Especially, tunnel excavation has increased in poor geological condition in order to maintain good alignment of road and the collapse of tunnel has often happened without reinforcement method. This research paper will analyze for ms and causes of the collapses for different geological conditions and applied reinforcement solutions by investigating typical collapse sites during highway tunnel constructions.

• The Journal of Engineering Geology
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• v.13 no.4
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• pp.445-456
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• 2003

Backfill grouting and consolidation grouting are major reinforcing methods that enhance the stability of tunnel by filling the gap between the tunnel lining and the ground and increasing the stiffness of the ground. However, the effect of the grouting on the tunnel lining is not well established. Field measurements such as pressuremeter test, Lugeon test, and lining instruments were peformed to analyze the grouting effect on the tunnel lining for a waterway tunnel. The elastic modulus was increased up to 5 times than that of original rock mass due to consolidation grouting. This study shows that only 10% of grout pressure was acting on the back face of the tunnel lining. The final results are expected to be used for the design of the concrete lining.

• The Journal of Engineering Geology
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• v.7 no.1
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• pp.1-10
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• 1997

The construction of Kyungbu canal connecting Han and Naktong rivers is needed to facilitate the carriage of goods and enhance the economic growth. The two rivers are liflked by the Choryeong tunnel with 20.5 km length and 125 m altitude. Seven locks involving of 25 m lifting height are planned to reach the tunnel from Shingok dam along the Han river. The tunnel and dams are located favorably by topographic and geologic map analysis. The water needed to fill the chamber of high lock will he supplied by construction of additional dams above Chungju-dam and/or intmduction of water-saving lock system.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.633-642
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• 2007

Traveltime tomogram is generally used for interpretation of seismic tunnel data. In the field data, the first arrival traveltime is less dispersive with increasing source-receiver seperation compared to theoretical model data. So the result of calculation can be serious despite of small errors such as traveltime picking. In this study, amplitude method and error tomogram method are tried to overcome these problems. This method will help the interpretation of the data from the underground tunnel.

• Proceedings of the KSEG Conference
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• 2000.04a
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• pp.85-93
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• 2000

• Proceedings of the KSEEG Conference
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• 2002.04a
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• pp.298-300
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• 2002

• The Journal of Engineering Geology
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• v.22 no.3
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• pp.323-330
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• 2012

The use of lattice girder is increased rapidly as a substitute for H-steel ribs at the tunnel sites in Korea. Ground loads acting on the tunnel are supported by shotcrete and lattice girders. To assess the safety of the tunnel, it is essential to obtain field measurements for the lattice girders; however, lattice girder measurements have rarely been performed at tunnel sites, and the method of measurement is not well established. In the present study we suggest a load cell method for the instrumentation of tunnels with lattice girders. Actual measurements of ground loads acting on lattice girders are presented for a specific tunnel under construction.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.455-461
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• 2014

The Honam-Jeju, Korea-Japan, and Korea-China subsea tunnel construction projects have drawn significant attention since the early 2000s. These subsea tunnels are much deeper than most existing natural shallow sea tunnels linking coastal areas. Thus, the need for developing new technologies for the site selection and construction of deep subsea tunnels has recently emerged, with the launch of a research project titled "Development of Key Subsea Tunnelling Technology" in 2013. A component of this research, an analysis of deep subsea geological structure, is currently underway. A ground investigation, such as a borehole or geophysical investigation, is generally carried out for tunnel design. However, when investigating a potential site for a deep subsea tunnel, borehole drilling requires equipment at the scale of offshore oil drilling. The huge cost of such an undertaking has raised the urgent need for methods to indirectly assess the local geological structure as much as possible to limit the need for repeated borehole investigations. This study introduces an indirect approach for assessing the geological structure of the seafloor through a submarine bathymetry analysis. The ultimate goal here is to develop an automated approach to the analysis of submarine geological structures, which may prove useful in the selection of future deep subsea tunnel sites.