• Tunnel and Underground Space
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• v.26 no.2
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• pp.68-86
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• 2016

Understanding the frictional properties of rock discontinuities is crucial to ensure the stability of underground structures. In particular, the frictional behavior at depth depends on the complex interaction among mechanical, hydraulic, thermal and chemical characteristics and their coupled effects. In this study, a series of shear tests were carried out in a triaxial compression chamber to investigate the shearing behavior of saw-cut granite surface and rough shear surface of synthetic rocks. The test results were analyzed using Coulomb's shear strength criterion. The frictional behavior of saw-cut granite surface showed little variation at different confining, water pressures and temperature conditions, however in case of synthetic rocks, the frictional behavior showed different trend depending on normal stress level. In addition, the variation of stiffness and dilation at different testing conditions were analyzed, and the stiffness and dilation showed little variation at different water pressures and temperature conditions.

• Geophysics and Geophysical Exploration
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• v.2 no.1
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• pp.1-7
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• 1999

We investigated the weathering characteristics of On-Yang gneiss by means of geological survey and Ground Penetrating Radar(GPR). The results of geological survey and boring show the two sets of vertical joint and horizontal joint developed by foliation which is composed of salic and melanic layers. GPR section evidently shows foliation direction and differential weathering due to discontinuity and mineral composition of metamorphic rock. The GPR section for instantaneous phase attribute based on complex trace analysis evidently shows continuity and foliation direction of metamorphic rock. The strong reflection amplitude which is derived from the banded structure of weathered rock can be incorrectly interpreted as a reflection of bedrock. The depth of rock basement should be estimated from the overall exploration result such as boring, seismic method, and electrical resistivity method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.1069-1077
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• 2015

In tunnel excavation using blast, the wire saw rock cutting method generates a discontinuity perimeter around the center cut, and thus prevents blast vibration propagation to reduce vibration and noise. Therefore, the method is expected to be easy to use and economical compared with other methods. In this paper, the cutting mechanism of wire saw in tunnel excavation is investigated. A model describing the changes in cutting depth and wire saw shape inside a rock during cutting is established and validated for this purpose. Through a simulation using the model, the important characteristics of wire saw cut are investigated, and the influences of cutting conditions, such as wire saw tension, wire saw speed, feed speed, depth, and diameter of boring, on cutting performance are also examined. A method to improve the cutting performance is proposed based on the results.

• Structural Engineering and Mechanics
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• v.60 no.5
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• pp.809-828
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• 2016

In deep open pit mines, slope stability is very important. Particularly, increasing the depths increase the risks in mines having weak rock mass. Blasting operations in this type of open pits may have a negative impact on slope stability. Several or combination of methods can be used in order to enable better analysis in this type of deep open-pit mines. Numerical modeling is one of these options. Many complex problems can be integrated into numerical methods at the same time and analysis, solutions can be performed on a single model. Rock failure criterions and rock models are used in numerical modeling. Hoek-Brown and Mohr-Coulomb terms are the two most commonly used rock failure conditions. In this study, mine planning and discontinuity conditions of a lignite mine facing two big landslides previously, has been investigated. Moreover, the presence of some damage before starting the study was identified in surrounding structures. The primary research of this study is on slope study. In slope stability analysis, numerical modeling methods with Hoek-Brown and Mohr-Coulomb failure criterions were used separately. Preparing the input data to the numerical model, the outcomes of patented-blast vibration minimization method, developed by co-author was used. The analysis showed that, the model prepared by applying Hoek-Brown failure criterion, failed in the stage of 10. However, the model prepared by using Mohr-Coulomb failure criterion did not fail even in the stage 17. Examining the full research field, there has been ongoing production in this mine without any failure and damage to surface structures.

• The Journal of the Convergence on Culture Technology
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• v.6 no.2
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• pp.467-472
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• 2020

Methods for deriving design input-parameters to ensure the stability of a structure on a common ground are generally well known. Folded metamorphic rocks, such as the study area, are highly foliated and have small faults parallel to the foliation, resulting in special research methods and tests to derive design input parameters, Etc. are required. The metamorphic rock ground with foliation development of several mm intervals has a direct shear test on the foliation surface, the strike/dip mapping of the foliation, the boring investigation to determine the continuity of the foliation, and the rock mass rating of the metamorphic rock. etc. are required. In the case of a large number of small foliation-parallel faults developed along a specific foliation plane, it is essential to analyze the lineament, surface geologic mapping for fault tracing, and direct shear test. Folded ground requires additional geological-structural-domain analysis, discontinuity analysis of stereonet, electrical resistivity exploration along the fold axis, and so on.

• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.218-231
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• 2006

Anisotropic/heterogeneous rock mass shows various deformation behavior types due to tunnelling because deformation behavior is largely controlled by the spacial characteristics of geological factors such as faults, joints and fractured zone in rock mass. In this paper 2-dimensional numerical analysis on the several influencing factors is performed considering fractured zone located near tunnel. This numerical analysis shows that deformation behavior of tunnel are very different according to the width and the location of fractured zone and supper method. However, 3-dimensional analysis is necessary to consider 3-dimensional geometrical characteristics sufficiently since discontinuity and fractured zone have 3-dimensional geometry. Also flexible design/construction guidelines for tunnelling are required to cope with uncertain ground condition and circumstance for technically safe and economic tunnel construction.

• Journal of the Korean Geosynthetics Society
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• v.21 no.2
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• pp.21-30
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• 2022

Shear strength is the most important indicator in the evaluation of rock slope stability. It is generally estimated by comparing the results of existing literature data, back analysis, experiments and etc. There are additional variables related to the state of discontinuity to consider in the shear strength of the rock slope. It is difficult to determine whether these variables exist through drilling, and it is also difficult to find an exact relationship with shear strength. In this study, the data calculated through back analysis were used. The relationship between previously considered variables was applied to deep learning and the possibility for estimating shear strength of rock slope was explored. For comparison, an existing simple linear regression model and a deep learning algorithm, a deep neural network(DNN) model, were used. Although each analysis model derived similar prediction results, the explanatory power of DNN was improved with a small differences.

• Explosives and Blasting
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• v.41 no.4
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• pp.17-28
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• 2023

Recently, the utilization of underground space for research facilities and resource development has been on the rise, expanding development from shallow to deep underground. The establishment of deep underground spaces necessitates a thorough examination of rock stability under conditions of elevated stress and temperature. In instances of greater depth, the stability is influenced not only by the geological structure and discontinuity of rock but also by the propagation of ground vibrations resulting from earthquakes and rock blasting during excavation, causing stress changes in the underground cavity and impacting rock stability. In terms of blasting engineering, empirical regression models and numerical analysis methods are used to predict ground vibration through statistical regression analysis based on measured data. In this study, single-hole blasting was conducted, and the pressure of the blast hole and observation hole and ground vibration were measured. Based on the experimental results, the blast pressure blasting vibration at a distance, and the response characteristics of the tunnel floor, side walls, and ceiling were analyzed.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.5-14
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• 2004

The observational design and construction method in tunnels is becoming important recently. In many tunnels, enormous cost and time are consumed to cope with the failing or sliding of rock blocks, which could not be predicted because of the complexity of rock discontinuities. It is difficult to estimate the properties of rock masses before the construction. In this paper, a new observational design and construction method in tunnels are proposed, and then applied to the example of the very large cross section tunnel based on actual discontinuity information observed in situ. The items examined in developing a program for the new observational design and construction method are the following ones: generality, precision, high speed, and friendly usability. At the very large cross section tunnel, 7 key blocks were judged to be unstable because they could not be supported by standard supports. Supplementary supports were installed to these 7 key blocks before the excavation. It is possible to detect key blocks all along the tunnel exactly by using the numerical analysis program developed for the new observational design and construction method in the very large cross section tunnel. This computer simulation method with user-friendly interfaces can calculate not only the stability of key blocks but also the design of supplementary supports.

• Economic and Environmental Geology
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• v.52 no.2
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• pp.189-197
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• 2019

HLW (High Level Radioactive Waste) is one of the problems that must be solved in the countries that implement nuclear power generation. Most countries that are concerned about HLW treatment are considering complete isolation from human society by disposing them deep underground. For perfect isolation, understanding the characteristics of underground rocks is very important. In particular, understanding the characteristics of discontinuity as a path way is one of the first things in order to predict the movement of exposed nuclear species to the surface. In this study, we used 500m underground core samples obtained from granite and gneiss area. The purpose of this study is to understand the characteristics of the discontinuities in each rock type and to analyze the properties of the joints in the underground relative to the surrounding environment. For this purpose, the types of discontinuities were classified and the distribution of each discontinuity were analyzed through visual analysis of the each sample obtained at 500m underground. This study can be used as a basic data for understanding the properties of discontinuities in the rock of the survey area and it can be also used as an important data for understanding the distribution characteristics of discontinuities according to the rock types.