• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.537-544
• /
• 2005

We find out many soft ground deep excavation cases where results of careless overexcavation accelerate the advance of loosening zone of adjacent ground, bucklings of struts and bottom heaves happen due to delayed supporting time. This article introduces a soft ground deep excavation case where steel pipe sheet piles were used with struts as an earth retaining system. There were 2 times of buckling in the supporting system and heaving of bottom ground due to overexcavation and insufficient penetration depth of the steel pipe sheet piles. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.529-536
• /
• 2002

The purpose of this paper os to present and discuss some of flow and drain observed in modelling results. Because dredged fill ground of Yul-Chon located in the south coast of Korea is very soft, this ground should be improved after operation of surface stabilization. There are surface stabilization method such as chemical stabilization, desiccation, horizontally vacuum drain, replacement, and geosynthetics. In Yul-Chon, PTM(Progressive Trenching Method) is adopted to provide the necessity condition of surface desiccation. In the case trench in the dredged soft ground is formed by PTM equipment, pore water in the ground is drained through trench. There, drain and desiccation of surface ground increase, and bearing capacity is improved. In this research, when trench in the dredged soft ground is formed by PTM equipment, permeable characteristics and drain efficiency of pore-water are analyzed using SEEP/W software package. Results show variation of total head, pressure head, flux, hydraulic gradient, and flow quantity.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.24 no.4
• /
• pp.150-157
• /
• 1988

The oceanographic condition around the set net fishing ground in Yeosu Bay was investigated by the oceanographic observation in June, July and August, 1988. Also the catch of the set net was analized by daly catch data of the three set net fishing ground from April to September, 1988. The results obtained are as follows: 1) The coastal surface water is high temperature and low salinity through the influence of land, and the off shore water and bottom water are low temperature and high salinity. 2) The eddy current and the sharp thermocline in June appeared in August at the set net fishing ground, and a good catch appeared in June and August. 3) The surface temperature and salinity at the set net fishing ground are 11$^{\circ}C$ to 27$^{\circ}C$ and 31.60$\textperthousand$ to 34.80$\textperthousand$. The surface temperature and salinity of a maximum good catch are 21$^{\circ}C$ and 33.80$\textperthousand$ to 33.99$\textperthousand$ respectively. 4) The dominant species of fish were spanish mackerel, scad, anchovy, sardine, common mackerel, hairtail, crab, yellow tail, in order of catch.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.2
• /
• pp.43-52
• /
• 2010

Shield method is the tunnel boring method that propels a steel cylinder in the ground and excavates tunnels at once. After Marc Isambard Brunel started using the method for the Thames Riverbed Tunnel excavation in London, many kinds of TBM (Tunnel Boring Machine) developed and applied for the construction of road, railway, electricity channel, pipeline, etc. In comparison with NATM concept that allows to observe ground condition and copes with difficulty. The machine selected before starting construction is not able to be changed during construction in shield TBM. Therefore the machine should be designed based on the ground survey result and experiment, so that the tunnel might be excavated effectively by controlling penetration speed, excavation depth and cutter head speed according to the ground condition change. This research was conducted to estimate penetration depth, excavate speed, wear of disc cutter on Boondang Railway of the Han Riverbed Tunnel ground condition by TBM performance prediction models such as NTNU, $Q_{TBM}$, Total Hardness, KICT-SNU and compare the estimated value with the field data. The estimation method is also used to analyze the reason of poor excavation efficiency at south bound tunnel.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.6
• /
• pp.1039-1048
• /
• 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 the Korean GEO-environmental Society
• /
• v.20 no.2
• /
• pp.49-58
• /
• 2019

A study on the analysis of underground ground condition using 3D-GPR exploration was carried out in this paper. The test bed was constructed similar to the field, and the detection analysis was carried out for each depth of cavity and underground burial. Through this, we were able to know the permittivity of the ground by inversion, and we could confirm the depth of detection for the joint by accurate calculation. We confirmed the signal waveforms in the cavity under the road through 3D-GPR exploration, analyzed more quantitatively in subjective and empirical analysis. The subsidence and depth of the subsurface settlement can be observed through 3D-GPR survey, and ground condition change after the ground reinforcement can be confirmed through the exploration section.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.7
• /
• pp.171-186
• /
• 2010

It is generally known that the mechanism of behavior in the flexible earth retaining system is relatively more complicated than in the rigid earth retaining system. Moreover in the case of long span strut supporting system the analysis of strut axial force change becomes more difficult when the differences of ground condition and excavation work progress on both sides of excavation section are added. When deeper excavation than the specification or installation delay of supporting system or change of ground condition happen during construction process, lots of axial force can be induced in some struts, which threaten the safety of construction. This paper introduces two examples of long span deep excavation where struts and rock bolts were used as a supporting system with flexible wall structure. The characteristics of ground deformation and strut axial force change, which were measured in the sections of two examples that are 50 meters apart in one construction site and have almost similar design and construction conditions were analysed, the similarity and difference between measurement results of two examples were compared and investigated. This article aims to improve and develop the technique of design and construction in future projects having similar ground condition and supporting method.

• Journal of the Korean GEO-environmental Society
• /
• v.23 no.2
• /
• pp.13-23
• /
• 2022

The ground-structure interaction of the bridge foundation has been pointed out as a major factor influencing the behavior of the bridge during earthquakes. In this study, the effect of characteristics of ground and bridge foundation on the earthquake vulnerability is investigated. From the pseudo-static analysis, it is confirmed that non-linearity becomes lesser and horizontal load becomes greater when surcharge is considered. It is also found that as the ground worsens and the size of foundation decreases, horizontal load reduces. To derive reasonable structural model for bridge foundation, fragility curve is obtained considering four conditions (fixed condition, equivalent linear condition, non-linear without surchage condition, non-linear with surcharge condition) and compared. Seismic analysis is performed on single pier with Opensees. From the earthquake vulnerability analysis, it is found that shallow foundation can be assumed as fixed condition. In conservative approach, stiffness of spring can be obtained based on Korean highway bridge design code for pile foundation which can consider the ground condition.

• Proceedings of the KSR Conference
• /
• 2011.05a
• /
• pp.1509-1518
• /
• 2011

Shield TBM tunneling method has been getting the spotlight for urban tunneling. It can be minimized the civil complaint during construction and possible safe tunneling. But the settlement has occurred inevitably due to characteristics of shield TBM equipment. For this reason, the civil complaint can occur in urban areas when tunnel with shallow depth passes through neighboring building or residential area. In this study, the occurrence factors of settlement according to shield TBM tunneling and the tendency of ground settlement by strata condition had analyzed. It is suggested that the practical settlement estimation method and minimizing method of ground settlement under simultaneous backfill grouting condition through measurement results and back analysis data using gap parameter.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.7
• /
• pp.27-33
• /
• 2016

This study expanded Terzaghi arching formula, which assumed a vertical surface as a sliding surface, to consider an arbitrarily inclined surface as a sliding surface and examined the effect of a sliding surface. This study firstly developed a formula to expand the existing Terzaghi arching formula to consider an inclined surface as well as a vertical surface as a sliding surface under the downward movement of a trap door. Using the expanded formula, the effect of excavation, ground, and surcharge conditions on a vertical stress was examined and the results were compared with them from Terzaghi arching formula. The comparison indicated that the induced vertical stress was highly affected by the angle of an inclined sliding surface and the degree of influence depended on the excavation, ground, and surcharge conditions. It is expected that the results from this study would provide a better understanding of various arching phenomenon in the future.