• Tunnel and Underground Space
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• v.7 no.3
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• pp.208-220
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• 1997

To asses the stability of structure around shaft during the excavation of -300 ml hopper room at 2nd shaft in Jangsung mine, some measurements were made with blast monitoring, stressmeter, extensometer and inclinometers. Instrumentations proved to be reliable and data were montiored over six month period. Stressmeters were set at the points of wall and arch of inset gang(level). Induced stresses were measured with the magnitude of 2.81 kgf/$\textrm{cm}^2$(tensile stress) and -4.45kgf/$\textrm{cm}^2$(compressive stress) respectively. These values were converged after two months. The magnitude of axial force in rock bolt was measured with 1.98 ton between the points of M2(2.25m) and M3(1.5 m) but this value was assumed within allowable level. Maximum displacement was also measured with 2 mm at the dephs of 12m from surface. But this value belongs within guide level.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.293-300
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• 2004

A new earth retention system(Innovative Prestressed Wale System) has been developed and introduced. IPR earth retention system provides an economical benefit, construction easiness, good performance and safety. IPS is a prestressed wale by using a steel wire, which provides a high stiffness to resist the earth pressure. In order to investigate the applicability and the safety of new IPS system, field tests were performed. A new IPS system applied in a trench excavation performed successfully. Basic principles and mechanism of IPS system and measure performance were presented and discussed.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.902-911
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• 2009

There appeared many difficulties due to various construction factors during the recent construction adjacent to the housing for the aging. In particular, the study is going to summarize and overview the selection procedure and construction details of the excavation engineering of this site, which could ensure workability and economic efficiency through the construction of a shorter anchor than the length of the existing anchor with a minimal marginal space without invading the nearby private land.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.78-83
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• 2007

The paper focuses on the establishment of optimized bucket path planning and trajectory control designated for force-reflecting backhoe reacting to excavation environment, such as potential obstacles and ground characteristics. The developed path planning method can be used for precise bucket control, and more importantly for obstacle avoidance which is directly related to safety issues. The platform of this research was based on conventional papers regarding the kinematic model of excavator. Jacobian matrix was constructed to find optimal joint angles and rotation angles of bucket from position and orientation data of excavator. By applying Newton-Raphson method optimal joint angles and bucket orientation were derived simultaneously in the way of minimizing positional errors of excavator. The model presented in this paper was intended to function as a cornerstone to build complete and advanced path planning of excavator by implementing soil mechanics and further study of excavator dynamics together.

• Tunnel and Underground Space
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• v.4 no.1
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• pp.63-76
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• 1994

This paper discusses contents of the existing design, the behaviours prediction on the strut and retaining wall around subsurfaces, and also evaluates the measured results in comparison with the management criterion during excavation period of ventilation shaft at Pusan-Subway 220. Field measurements showed that maximum displacement 23.74 mm at boundary site of multistratification and the weathered rock to be formed at 0.2~0.6 H of total excavating depth(H), 68 ton of maximum axial force and 4.4X102 kg/cm2 of stress on strut. The measured axial force exceeds prediction levels by up to 50 percent at the weathered soil & rock, and the others come under the category of their levels. The great gap of both field measurements and prediction on behaviour makes a difference of the site situation at the design stage and the practical working. This measured value is greatly safety in comparison with that of the safety criterion, but axial force at 4~5 strut of ventilation shaft l is higher than the prediction.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.320-329
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• 2005

The use of diverse methods for the retaining system has been continuously increased in order to maintain the stability during excavation. However, ground anchor system occasionally may have the restriction in urban excavation sites nearby the existing structures because of space limitation. In this case, soil nailing system with relatively short length of nails could be efficiently useful as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in excavating the zone of weak soils or nearby the existing structures. Therefore, applying the pretension force to the soil nails then could play important roles to reduce deformations mainly in an upper part of the nailed-soil excavation system as well as to improve the local slope stability. In this study, a newly modified soil nailing technology named as the PSN(Pretention Soil Nailing) is developed to reduce both facing displacements and ground surface settlements during top-down excavation process as well as to increase the global slope stability. Up to now, the PSN system has been investigated mainly focusing on an establishment of the design procedure. In the present study, the field tests including pull-out tests were fulfilled to investigate the behavior of characteristics for PSN system. All results of tests were also analyzed to provide a fundamental and efficient design.

• Journal of the Korean Geotechnical Society
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• v.37 no.12
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• pp.89-105
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• 2021

In this paper, feasibility study was carried out to evaluate necessity of seismic design of earth retaining structures in a deep excavation. Dynamic behavior of retaining system was analyzed using FLAC, a finite difference analysis program. It was shown that maximum bending moments of retaining walls and axial forces of supports were increased up to 98% and 87% during earthquake, respectively, compared to final excavation step, which indicates that dynamic earth pressure has a large effect on a retaining system. The stability of retaining system designed according to current design specifications was evaluated using structural forces obtained by numerical analysis, and effect of earthquake loading on structural design was analyzed.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.197-206
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• 2004

The ground anchor support system may not be occasionally used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then could play important roles to reduce deformations mainly in the upper part of the nailed-soil excavation system as well as to improve local stability. In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing), is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the analytical procedure and design technique are proposed to evaluate maximum pretension force and stability of the PSN system. Also, proposed are techniques to determine the required thickness of a shotcrete facing and to estimate probability of a failure against the punching shear, Based on the proposed procedure and technique, effects of the radius of a influence circle and dilatancy angle on the thickness of a shotcrete facing, bonded length and safety factors are analyzed. In addition, effects of the reduction of deformations expected by pretension of the soil nails are examined in detail throughout an illustrative example and the $FLAC^{2D}$ program analysis. And a numerical approach is proposed PSN system using the shear strength reduction technique with the $FLAC^{2D}$ program.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.4
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• pp.657-669
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• 2018

In recent years, the development of complex urban areas has become saturated and much attention has been focused on the development of underground space, and deep excavation is frequently performed in order to increase the utilization of underground space due to the enlargement of buildings and the high rise of buildings. Therefore, in this study, we tried to understand the behavior of the braced wall and the behavior of the tunnel adjacent to the wall according to the stiffness of the wall and the distance between the tunnel and wall. As a result of the study, the deformation of the braced wall tended to decrease with increasing the stiffness of the wall, and the axial force acting on the struts was also different according to the stiffness of braced wall. When the stiffness of the braced wall is small (2 mm), the point at which the axial force of the braces maximizes is near 0.3H of the wall. When the stiffness of the braced wall is large (5 mm), the axial force is maximum at around 0.7H of the wall. Also, the tunnel convergence occurred more clearly when the separation distance from the braced wall was closer, the stiffness of the wall was smaller, and the tunnel convergence was concentrated to the lower right part. The ground settlement due to the excavation of the ground tended to decrease as the distance between tunnel and braced wall was closer to that of the tunnel, which is considered to be influenced by the stiffness of the tunnel.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.225-232
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• 2003

The behaviour of ground induced by tunneling of 2arch tunnels may differ from the one caused by usual type tunnels. This paper describe the behaviour created by the size of pilot tunnel and the condition on the construction method of center piller Also, loads acting on the supports of the first tunnel and the center pillar during the excavation of second tunnel is investigated by numerical analyses. The results of numerical analyses are compared to the data records of measurement results, i.e. force on the support system and ground displacement.