• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.10a
• /
• pp.434-478
• /
• 2006

Stress waves have been used for geophysical and geotechnical applications for more than 50 years. The early-stage applications were simply based on travel-time measurements of stress waves and limited to site characterization. Currently stress-wave techniques are expanded to monitoring processes for grouting of damaged geotechnical structures, compaction of embankment, and deformational analyses for static geotechnical problems. Seismic techniques used to be good enough for rough estimators of engineering properties. Nowadays, the sophisticated modeling theory of stress-wave propagation substantially improved reliability and accuracy of the seismic techniques. In this paper, difficulties involved in currently available seismic techniques are discussed and analyzed. Herein some recently-developed non-intrusive seismic techniques, which make optimal use of stress waves for further improvement of reliability and accuracy, are also presented.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.3.2-27
• /
• 2002

This paper presents the status of dam construction in Korea, along with a brief assessment of the dam design and construction practice. The assessment is based on publically available design and construction records of the major existing rockfill dams which have been constructed since early 1970's, and focussed in identifying geotechnical characteristics of design and construction parameters of the dams. Though the assessment, two representative dams, having unique geotechnical characteristics, are selected for comprehensive comparison of their geotechnical engineering behavior during construction and operation. The comparison yields very interesting findings on the effects of various design and construction parameters on dam behavior.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2001.10c
• /
• pp.1-17
• /
• 2001

• Proceedings of the Korean Geotechical Society Conference
• /
• 1998.06b
• /
• pp.35-58
• /
• 1998

• Proceedings of the Korean Geotechical Society Conference
• /
• 1993.06b
• /
• pp.45-98
• /
• 1993

• Proceedings of the Korean Geotechical Society Conference
• /
• 1995.10a
• /
• pp.9-14
• /
• 1995

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.12a
• /
• pp.31-42
• /
• 2007

Dc resistivity monitoring has been increasingly used in order to understand the changes of subsurface conditions in terms of conductivity. The commonly adopted interpretation approach which separately inverts time-lapse data may generate inversion artifacts due to measurement error. Eventually the contaminated error amplifies the artifacts when reconstructing the difference images to quantitatively estimate the change of ground condition. In order to alleviate the problems, we defined the subsurface structure as four dimensional (4-D) space-time model and developed 4-D inversion algorithm which can calculate the reasonable subsurface structure continuously changing in time even when the material properties change during data measurements. In this paper, we discussed two case histories of resistivity monitoring to study the ground condition change when the properties of the subsurface material were artificially altered by injecting conductive materials into the ground: (1) dye tracer experiment to study the applicability of electrical resistivity tomography to monitoring of water movement in soil profile and (2) the evaluation of cement grouting performed to reinforce the ground. Through these two case histories, we demonstrated that the 4-D resistivity imaging technique is very powerful to precisely delineate the change of ground condition. Particularly owing to the 4-D inversion algorithm, we were able to reconstruct the history of the change of subsurface material property.

• Journal of the Korean Geosynthetics Society
• /
• v.12 no.2
• /
• pp.43-53
• /
• 2013

Environmental monitoring analysis were analyzed for the period from 1988 to 2007 near King Sejong Station. Extreme environment structure behaviors(Marine Biology Lab.) were evaluated using monitoring sensors developed commercial sensors. Also when installing the sensors ambient environment of the King Sejong Station, to analyze the measured data and the comparative behavior of the structure were analyzed. As a environmental monitoring analysis result at King Sejong Station temperature, sensors were installed to withstand about $-25.6^{\circ}C$ or less and 49.5m/s. They were needed that the height of 225.0cm or more to be installed during the installation. For several monitoring sensors used in Antarctic, temperature, snow and strong winds were very sensitive to the atmospheric environment. Quite often a camouflage(animals and humans) would make it necessary to provide housing for monitoring sensors. Therefore, protection system developed for these sensors were to protect the sensors and data logger. Protection system the newly developed, is economical, easy to install even in harsh environments. Based on the measurement result of the one year, consider electrode applicability of the protection system, it was confirmed that the behavior of the structure is also predictable.

• Geomechanics and Engineering
• /
• v.28 no.4
• /
• pp.335-346
• /
• 2022

Buckling failure is a typical slope instability mode that should be paid more attention to. It is difficult to provide systematic guidance for the monitoring and management of such slopes due to unclear mechanism. Here we examine buckling failure as the potential instability mode for a slope above a railway tunnel in southwest China. A comprehensive model test system was developed that can be used to conduct buckling failure experiments. The displacement, stress, and strain of the slope were monitored to document the evolution of buckling failure during the experiment. Monitoring data reveal the deformation and stress characteristics of the slope with different slipping mass thicknesses and under different top loads. The test results show that the slipping mass is the main subject of the top load and is the key object of monitoring. Displacement and stress precede buckling failure, so maybe useful predictors of impending failure. However, the response of the stress variation is earlier than displacement variation during the failure process. It is also necessary to monitor the bedrock near the slip face because its stress evolution plays an important role in the early prediction of instability. The position near the slope foot is most prone to buckling failure, so it should be closely monitored.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.319-326
• /
• 2002

During the construction period of submarine shield tunnel, which is built firstly in very soft marine clay layer 40m deep in Korea, wide range problems were encountered such as safe launching against high earth pressure at shield entrance, technique of shield face pressure control when passing through complex multi-layered soils This paper introduces successful construction practice through development of state-of-the-art construction method and field monitoring.