• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1046-1053
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• 2006

In the large scale recent reclaiming works performed within the wide spatial boundary, evaluation of long-term consolidation settlement and residual settlement of the whole construction area is sometimes made with the results of the limited ground investigation and measurement. Then the reliability of evaluation has limitations due to the spatial uncertainty. Additionally, in case of large scale deep excavation works such as urban subway construction, there are a lot of hazardous elements to threaten the safety of underground pipes or adjacent structures. Therefore it is necessary to introduce a damage prediction system of adjacent structures and others. For the more accurate analysis of monitoring information in the wide spatial boundary works and large scale urban deep excavations, it is necessary to perform statistical and spatial analysis considering the geographical spatial effect of ground and monitoring information in stead of using diagrammatization method based on a time-series data expression that is traditionally used. And also it is necessary that enormous ground information and measurement data, digital maps are accumulated in a database, and they are controlled in a integrating system. On the abovementioned point of view, we developed Geomonitor 2.0, an Internet based real time monitoring program with a new concept by adding GIS and geo-statistical analysis method to the existing real time integrated measurement system that is already developed and under useful use. The new program enables the spatial analysis and database of monitoring data and ground information, and helps the construction- related persons make a quick and accurate decision for the economical and safe construction.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1211-1218
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• 2005

Temperature variation according to space and time on the inner parts of engineering constructions(e.g.: dam, slope) can be a basic information for diagnosing their safety problem. In general, as constructions become superannuated, structural deformation(e.g.: cracks, defects) could be occurred by various factors. Seepage or leakage of water through these cracks or defects in old dams will directly cause temperature anomaly. Groundwater level also can be easily observed by abrupt change of temperature on the level. This study shows that the position of seepage or leakage in dam body can be detected by multi-channel temperature monitoring using thermal line sensor. For this, diverse temperature monitoring experiments for a leakage physical model were performed in the laboratory. In field application of an old dam, temperature variations for water depth and for inner parts of boreholes located at downstream slope were measured. Temperature monitoring results for a long time at the bottom of downstream slope of the dam showed the possibility that temperature monitoring can provide the synthetic information about flowing path and quantity of seepage of leakage in dam body.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.65-78
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• 2008

In case of cut-slopes or shallow-depth tunnels, sliding along with discontinuities or rotation could play a critical role in judging stability. Although numerical analysis is widely used to check the stability of these cut-slopes and shallow-depth tunnels in early design process, common analysis programs are based on continuum model. Performing continuum model analysis regarding discontinuities is possible by reducing overall strength of jointed rock mass. It is also possible by applying ubiquitous joint model to Mohr-Coulomb failure criteria. In numerical analysis of cut-slope, main geotechnical properties such as cohesion, friction angle and elastic modulus can be evaluated by empirical equations. This study tried to compare two main systems, RMR and GSI system by applying them to in-situ hazardous cut-slopes. In addition, this study applied ubiquitous joint model to simulation model with inputs derived by RMR and GSI system to compare with displacements obtained by in-situ monitoring. To sum up, numerical analysis mixed with GSI inputs and ubiquitous joint model proved to provide most reliable results which were similar to actual displacements and their patterns.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.60-68
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• 2010

In this study, the seepage flow monitoring method by hydaulic head loss rate graph was developed for the purpose of monitoring the seepage flow from the see side or from the lake on sea dike in which seepage force was varied periodically. The hydraulic head loss rate was defined in this method. The value of the rate is in the range from 0 to 1. the value of 0 means perfectly free flow of seepage. the value of 1 means perfect waterproofing. The value of coefficient of determination in the hydraulic head loss rate graph closer to 1 means that the seepage flow way is stable. The value of coefficient of determination in the hydraulic head loss rate graph closer to 0 means that the hole may exist or the piping may be in the progress. The pore water pressure data measured in Saemangeum sea dike was analyzed with the developed method The result showed that the variation of seepage flow state was detected sensitively by this method and the interception effect of sea dike could be estimated quantitatively.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1588-1595
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• 2005

In this study, the installation location of accelerometer and accelerograph for dam are investigated in the field to establish of emergency action against dam failure when earthquake occur and to guarantee the results of seismic stability of dams which are analysed with dynamic analysis method during 1999 to 2003 by KOWACO. By a comparative study concerning of domestic and foreign guidelines of seismic strong motion instrumentation for dams, "Guidelines of Seismic Strong-Motion Instrumentation Installation, Operation and Maintenance for Dams" is established to set up the standard of seismic strong-motion instrumentation for dam, are supervised by KOWACO There is some problems in taking a measure of stability of dams when earthquake event occur because the existing seismic strong motion instruments are operated independently. This make difficult to confirm the occurrence of seismic event. For that reason, in this study the plan of unified operation and maintenance system for strong-motion instrument for dams is designed. It will make possible real-time seismic monitoring, data transmission and receiving, giving warning for earthquake, and exchanging data with national seismic network.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.285-292
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• 2004

Earth Anchor method as a supporting system is widely used in the large scale deep excavation of urban areas or slope excavation project. Considering the application frequency of that method and catastrophe of that method under unproper construction management, we can find out many problems relevant to the domestic design and construction management of earth anchor method. When we encounter the cases of rapid increments and various decrements in earth anchor axial forces, considering the characteristic of earth anchor method, it is an essential point to catch the reasons and to prepare countermeasures. This article introduces two actual monitoring examples based on the close analyses of measured data in a typical large scale deep excavation project and slope excavation project. One is a rapidly increasing case of earth anchor axial forces with the continuous advance of incremental deformation in a geological layer interface. And another is a decreasing case of earth anchor axial forces with the construction conditions. 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.

• Tunnel and Underground Space
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• v.27 no.4
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• pp.185-194
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• 2017

This technical paper is a study on the unique displacements of Shotcrete Lining at the mined tunnel during excavation period through deep consideration with real time data from monitoring instrumentations correlation with the numerical analysis to identify the rock stresses and the rock spring points at the working face of the Conventional tunnelling by the Drill and Blast, based on the geological face mapping results of the project NS2, Transmission cable tunnel project in Singapore. The created geometry of numerical model was prepared to the real mined tunnel construction site including, vertical shaft, construction adit, tunnel junction area, and 2 enlargement caverns. The convergence measurements by the monitoring instrumentation were performed during the tunnel excavation and shaft sinking construction stages to guarantee the safety of complicated underground structures.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.401-408
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• 2009

Old national Road No. 59 that connects Danyang and Gagok has 35 dangerous cut slopes. It is relatively narrow and has a poor alignment. The torrential rains in 2002 and 2006 has caused numerous slope collapses, landslides and road settlements in this area. The old road's high risk level lead to the planning and construction of a new national road. During the construction of the new road in December 2006, the right side of Dugcheon Tunnel entrance has collapsed and tension cracks were observed on the district road above the tunnel. In order to determine the cause of failure, intensive field investigation and monitoring cracks were performed together with Lower Hemisphere Projection Analysis, Limit Equilibrium Analysis and Finite Difference Analysis.

• Journal of the Korean Geosynthetics Society
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• v.5 no.3
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• pp.45-52
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• 2006

The collapsed cases are more and more increasing at the large scaled structures because of increasing of the risk due to natural disasters. The measuring instrument such as inclinometer, total station on reinforced-soil retaining wall has been used that displacement, settlement for stability assessment, maintenance and management of it. But because these has gotten many instability measuring factors for stability analysis of RRW, new system needs to complement disadvantage of existing system. In this study, we considered a application of Visual Monitoring System (VMS) to measure a displacement in face of wall through Lab. test about block assembly of segmental retaining wall during load test.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.41-49
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• 2003

Rainfall-induced landslides in a weathered granite soil slope usually happen on shallow slip surfaces above the groundwater table. The pore-water pressure of soil above the groundwater table is usually negative. This negative pore-water pressure (or matric suction) has been found to make a large contribution to the slope stability. Therefore, the variation of in-situ matric suction profiles with time elapse in a soil slope should be understood. In this study, a field measurement program was carried out from June to August, 2001 in order to monitor in-situ matric suctions and volumetric water contents in a weathered granite soil slope. Finite-element transient seepage analyses are also conducted using SEEP/W. The influence of climatic conditions on the variation of in-situ matric suctions could be found to decrease rapidly with the change of depth. It could be found that decrement of matric suction induced by precipitation is affected not only by the amount and duration of rainfalls but also by the initial matric suction just prior to rainstorms. The soil-water characteristic from the field monitoring tends toward the wetting path of SWCC obtained from the laboratory test.