• Earthquakes and Structures
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• v.13 no.6
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• pp.519-529
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• 2017

The surrounding rocks of underground openings are natural materials and their mechanical behavior under seismic load is different from traditional man-made materials. This paper proposes a framework to comprehensively model the mechanical behavior of surrounding rocks. Firstly, the effects of seismic load on the surrounding rocks are summarized. Three mechanical effects and the mechanism, including the strengthening effect, the degradation effect, and the relaxation effect, are detailed, respectively. Then, the framework for modelling the mechanical behavior of surrounding rocks are outlined. The strain-dependent characteristics of rocks under seismic load is considered to model the strengthening effect. The damage concept under cyclic load is introduced to model the degradation effect. The quantitative relationship between the damage coefficient and the relaxation zone is established to model the relaxation effect. The major effects caused by seismic load, in this way, are all considered in the proposed framework. Afterwards, an independently developed 3D dynamic FEM analysis code is adopted to include the algorithms and models of the framework. Finally, the proposed framework is illustrated with its application to an underground opening subjected to earthquake impact. The calculation results and post-earthquake survey conclusions are seen to agree well, indicating the effectiveness of the proposed framework. Based on the numerical calculation results, post-earthquake reinforcement measures are suggested.

• Geomechanics and Engineering
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• v.29 no.4
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• pp.391-405
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• 2022

A newly proposed grouting simulation method, the sequential diffusion solidification method was introduced into the numerical simulation of combined bi-borehole grouting. The traditional, critical and difficult numerical problem for the temporal and spatial variation simulation of the slurry is solved. Thus, numerical simulation of grouting and blocking of flowing water in karst conduits is realized and the mechanism understanding of the combined bi-borehole technology is promoted. The sensitivity analysis of the influence factors of combined bi-borehole grouting was investigated. Through orthogonal experiment, the influences of proximal and distal slurry properties, the initial flow velocity of the conduit and the proximal and distal slurry injection rate on the blocking efficiency are compared. The velocity variation, pressure variation and slurry deposition phenomenon were monitored, and the flow field characteristics and slurry outflow behavior were analyzed. The interaction mechanism between the proximal and distal slurries in the combined bi-borehole grouting is revealed. The results show that, under the orthogonal experiment conditions, the slurry injection rate has the greatest impact on blocking. With a constant slurry injection rate, the blocking efficiency can be increased by more than 30% when using slurry with weak time-dependent viscosity behavior in the distal borehole and slurry with strong time-dependent viscosity behavior in the proximal borehole respectively. According to the results of numerical simulation, the grouting scheme of "intercept the flow from the proximal borehole by quick-setting slurry, and grout cement slurry from the distal borehole" is put forward and successfully applied to the water inflow treatment project of China Resources Cement (Pingnan) Limestone Mine.

• Proceedings of the Korean Geotechical Society Conference
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• 1996.10a
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• pp.135-140
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• 1996

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.143-150
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• 2000

A field test performance of FRP-Grouting method at a collapsed slope were carried out to verify the improving effect. The results are summerized in this paper.

• Proceedings of the Korean Geotechical Society Conference
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• 1995.10a
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• pp.15.3-24
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• 1995

• Proceedings of the Korean Geotechical Society Conference
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• 1995.03a
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• pp.143-152
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• 1995

• 한국지구물리탐사학회:학술대회논문집
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• 1999.08a
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• pp.37-47
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• 1999

Among the geophysical exploration methods, electromagnetic (EM) survey must have the broadest range of instrumental systems and remarkable range of applications. There is a plethora of available techniques and instruments, and the depth of investigation and resolution are highly dependent on the particular systems used according to their operating frequency and source-receiver configuration. This diversity of EM systems, however, provides a wide range of instruments or methodologies to choose in order to select the most appropriate tool for the task in hand. This rather than being a disadvantage, would be a major strength of EM methods. Modern EM equipments are remarkably portable, considering their sophistication. Coupled with major advances in recent computer technology, accurate modeling and interpretation techniques are on the way of continuous development and upgrade which, in turn, make the EM methods to become much more heavily used, especially for engineering and environmental applications. We aim to provide a brief theoretical principles, survey techniques and case histories of some selected EM methods that can be applied to geotechnical and environmental problems in Korea.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.4
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• pp.32-49
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• 2010

Site characterization on geological and geotechnical conditions was performed for evaluating the earthquake ground motions associated with seismic site effects at a small urbanized area, Hongseong, where structural damages were recorded by an earthquake of magnitude 5.0 on October 7, 1978. In the field, various geotechnical site investigations composed of borehole drillings and seismic tests for obtaining shear wave velocity profile were carried out at 16 sites. Based on the geotechnical data from site investigation and additional collection in and near Hongseong, an expert system on geotechnical information was implemented with the spatial framework of GIS. For practical application of the GIS-based geotechnical information system to assess the earthquake motions in a small urban area, spatial seismic zoning maps on geotechnical parameters, such as the bedrock depth and the site period ($T_G$), were created over the entire administrative district of Hongseong town, and the spatial distributions of seismic vulnerability potentials were intuitively examined. Spatial zonation was also performed to determine site coefficients for seismic design by adopting a site classification system based on $T_G$. A case study of seismic zonation in the Hongseong area verified that the GIS-based site investigation was very useful for regional prediction of earthquake ground motions in a small urbanized inland area.

• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.5-19
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• 2009

Most of earthquake-induced geotechnical hazards have been caused by the site effects relating to the amplification of ground motion, which is strongly influenced by the local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated GIS-based information system for geotechnical data, called geotechnical information system (GTIS), was constructed to establish a regional counterplan against earthquake-induced hazards at an urban area of Daejeon, which is represented as a hub of research and development in Korea. To build the GTIS for the area concerned, pre-existing geotechnical data collections were performed across the extended area including the study area and site visits were additionally carried out to acquire surface geo-knowledge data. For practical application of the GTIS used to estimate the site effects at the area concerned, seismic zoning map of the site period was created and presented as regional synthetic strategy for earthquake-induced hazards prediction. In addition, seismic zonation for site classification according to the spatial distribution of the site period was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site in the study area. Based on this case study on seismic zonations in Daejeon, it was verified that the GIS-based GTIS was very useful for the regional prediction of seismic hazards and also the decision support for seismic hazard mitigation.

• Geotechnical Engineering
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• v.11 no.3
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• pp.43-54
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• 1995

The aim of the work described in this paper is to develope a constitutive model for the prediction of an unsaturated soil and to confirm the application'of the model, which is composed of the elastic and plastic part in consideration of the matric suction and the net mean stress. From test results, volume changes and deviator stresses are analyzed at each state and their relationships are formulated. The application of the model to silty sands is confirmed by the comparison between test and predicted results. During drying -wetting and loading -unloading processes for isotropic states, the agreement between predicted and test results are satisfactory. Predicted deviator stresses are well agreed with test results in shearing process. Overall acceptable predictions are reproduced in high confining pressure. Usefulness of the model is confirmed for the unsaturated soil except volumetric strain, which is not well agreed with the test results due to deficiency of dilatancy of the model in low confining pressure. It is, therefore. recommended to study the behavior of dilatancy for an unsaturated soil.