• Journal of Korean Society for Geospatial Information Science
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• v.14 no.3 s.37
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• pp.55-62
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• 2006

The purpose of the current research is to evaluate the possibility of landslides by using geo-spatial information system. Geological information has been summarized and stability analysis for infinite slopes has been conducted based on the force equilibrium. In addition, the analysis of landslides was performed based on probabilistic approach by using probabilistic variables which can include uncertainty of input parameters. For the purpose of testifing the applicability of the analysis method actual geological data from a construction site was obtained, thereby performing both a preliminary analysis for a large area and detailed analysis for a better result. As a result of the current analysis several issues such as the possibility of development of landslides, detailed analysis of where landslides are most likely to be developed were analysed by using two concepts of safety and index of failure probability.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.121-131
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• 2017

We studied the time-dependent behaviors of rock and concrete materials by conducting the static and dynamic long-term strength tests. In particular, acoustic emission(AE) signals generated while the tests were analyzed and used for the long-term stability evaluation. In the static subcritical crack growth test, the long-term behavior and AE characteristics of Mode I and Mode II were investigated. In the dynamic long-term strength test, the fatigue limit and characteristics of generation of AE were analyzed through cyclic four points bending test. The graph of the cumulative AE hits versus time showed a shape similar to that of the creep curve with the first, second and third stages. The possibility for evaluating the static and dynamic long-term stability of rock and concrete is presented from the log - log relationship between the slope of the secondary stage of cumulative AE hits curve and the delayed failure time.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.269-281
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• 2021

Land creeping is the imperceptibly slow, steady, downward movement o f slope-forming soil or rock. Because creep-related failures occur frequently on a large scale without notice, they can be hazardous to both property and human life. Korea Forest Service has operated the prevention and response system from land creeping which has been on the rise since 2018. We categorized and proposed three survey steps (e.g., preliminary, regional, detailed) for investigation of creeping susceptibility site with a focus on geophysical mapping of a selected test site, Yongheung-dong, Pohang, Korea. The combination of geophysical (dipole-dipole electrical resistivity tomography and reciprocal seismic refraction technique, well-logging), geotechnical studies (standard penetrating test, laboratory tests), field mapping (tension cracks, uplift, fault), and comprehensive interpretation of their results provided the reliable information of the subsurface structures including the failure surface. To further investigate the subsurface structure including the sliding zone, we performed high-resolution geophysical mapping in addition to the regional survey. High-resolution seismic velocity structures are employed for stability analysis because they provided more simplified layers of weathering rock, soft rock, and hard rock. Curved slip plane of the land creeping is effectively delineated with a shape of downslope sliding and upward pushing at the apex of high resistive bedrock in high-resolution electrical resistivity model with clay-mineral contents taken into account. Proposed survey steps and comprehensive interpretation schemes of the results from geological, geophysical, and geotechnical data should be effective for data sets collected in a similar environment to land-creeping susceptibility area.

• Steel and Composite Structures
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• v.31 no.6
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• pp.629-640
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• 2019

The investigation of retaining wall structures behavior under dynamic loads is considered as one of important parts for designing such structures. Generally, the performance of these structures is under the influence of the environment conditions and their geometry. The aim of this research is to design retaining wall structures based on smart and optimal systems. The use of accuracy and speed to assess the structures under different conditions is one of the important parts sought by designers. Therefore, optimal and smart systems are able to have better addressing these problems. Using numerical and coding methods, this research investigates the retaining wall structure design under different dynamic conditions. More than 9500 models were constructed and considered for modelling design. These designs include height and thickness of the wall, soil density, rock density, soil friction angle, and peak ground acceleration (PGA) variables. Accordingly, a neural network system was developed to establish an appropriate relationship between data to obtain safety factor (SF) of retaining walls under different seismic conditions. Different parameters were analyzed and the effect of each parameter was assessed separately. According to these analyses, the structure optimization was performed to increase the SF values. The optimal and smart design showed that under different PGA conditions, the structure performance can be appropriately improved while utilization of the initial (or basic) parameters leads to the structure failure. Therefore, by increasing accuracy and speed, smart methods could improve the retaining structure performance in controlling the wall failure. The intelligent design process of this study can be applied to some other civil engineering applications such as slope stability.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.20 no.1
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• pp.43-63
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• 2022

The aim of this review is to communicate some essential knowledge of the underlying mechanism of the corrosion of structural containment alloys during molten salt reactor operation in the context of prospective online monitoring in future MSR installations. The formation of metal halide species and the progression of their concentration in the molten salt do reflect containment corrosion, tracing the depletion of alloying metals at the alloy salt interface will assure safe conditions during reactor operation. Even though the progress of alloying metal halides concentrations in the molten salt do strongly understate actual corrosion rates, their prospective 1^st order kinetics followed by near-linearly increase is attributed to homogeneous matrix corrosion. The service life of the structural containment alloy is derived from homogeneous matrix corrosion and near-surface void formation but less so from intergranular cracking (IGC) and pitting corrosion. Online monitoring of corrosion species is of particular interest for molten chloride systems since besides the expected formation of chromium chloride species CrCl₂ and CrCl₃, other metal chloride species such as FeCl₂, FeCl₃, MoCl₂, MnCl₂ and NiCl₂ will form, depending on the selected structural alloy. The metal chloride concentrations should follow, after an incubation period of about 10,000 hours, a linear projection with a positive slope and a steady increase of < 1 ppm per day. During the incubation period, metal concentration show 1^st order kinetics and increasing linearly with time^1/2. Ideally, a linear increase reflects homogeneous matrix corrosion, while a sharp increase in the metal chloride concentration could set a warning flag for potential material failure within the projected service life, e.g. as result of intergranular cracking or pitting corrosion. Continuous monitoring of metal chloride concentrations can therefore provide direct information about the mechanism of the ongoing corrosion scenario and offer valuable information for a timely warning of prospective material failure.

• Computers and Concrete
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• v.31 no.5
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• pp.395-403
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• 2023

The paper investigates the effect of two parameters - sand content (SC) and grain migration during shearing - on the mechanical properties of gravel-sand mixtures. Consolidated undrained (CU) triaxial tests were carried out on eight series of mixtures containing gravel (1<d<16 mm) and sand (0.1<d<1 mm). The prepared mixtures have sand contents of 0, 10, 15, 20, 40, 54, 94 and 100%, and a relative density of 60%. The transition sand content (TSC) is experimentally defined and marks the transition from gravel-driven to sand-driven behavior. For SC<TSC, the dry density of the mixture increases with SC. This induces an increase in undrained peak strength and dilative trend. The slope and position of the critical state line (CSL) are also deeply dependent on SC. At SC=TSC, the mixtures exhibit the largest dry density and yield the highest undrained peak strength and the largest dilative trend. During shearing, large internal migration of grains was observed at the TSC, causing heterogeneity in the sample. Analysis of the CSL deduced from the final points of the triaxial tests shows that, at the TSC, failure appears to correspond to the behavior of the coarsest fraction of the soil. This fraction is located in the upper part of the sample, where the sand particles had been eliminated by suffusion. On the other hand, in the more stable materials, the CSL is consistent with the bulk grain size distribution of the soil.

• The Journal of Engineering Geology
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• v.18 no.1
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• pp.83-92
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• 2008

In order to analyze infiltration characteristics of rainfall in soil, two laboratory experiments were conducted using an amplitude domain reflectometry (ADR) sensor and a pore water pressure meter (PWP) in this study. The first experiment is to understand the dependency of volumetric water content and temperature for standard sand and weathered granite soil. The second experiment is a laboratory flume test with changes of rainfall condition. As the results of the dependency experiment, the volumetric water content is increased with increase of the output voltage measured by the ADR sensor in both the standard sands and weathered granite soil. Furthermore, the results also indicate necessity of consideration of the temperature dependency under the condition of high volumetric water contents from 0.15 to 0.45. In the flume test, two measurement devices are detected to the variation of volumetric water content and pore water pressure at the installation point of the flume. In especial, the measured values of ADR4 and PWP3 installed on the lower part of slope are higher than those of the others. It means that the lower part of slope plays a role of a runoff face and a beginning point of slope failure.

• Journal of the Korean GEO-environmental Society
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• v.15 no.9
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• pp.69-75
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• 2014

Rock fall protection system installed against rock slope is one of the most conventional way to protect nearby infra structures. Despite of wide application of typical rectangular nets, virtually installed to protect rock slope face, several problems have also been pointed out up to date. Rectangular draped nets are vulnerable to a sudden external shock such as rock fall, because it doesn't have any systematical buffers or shock absorbers. Furthermore, it has been widely recognized from the some cases of rock fall accident in Korea that rock fall protection nets cause wide range of failure in the rock slope faces due to insufficient pullout bearing capacity of fixing parts. Therefore, in this study, we tried to make a consideration about the problems of existing standard rock fall protection nets in Korea, and develop a new type of hexagonal net with a shock absorber based on design rock fall energy. In this paper, laboratory and full scale test procedure is described to analysis the performance of newly developed hexagonal rock fall net, and the key results are presented and discussed.

• Journal of Conservation Science
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• v.28 no.2
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• pp.153-164
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• 2012

The major petroglyphs of Bangudae site were composed mainly of hornfelsed shale. Surface of the rock was formed weathering layer (average porosity 25%) that discriminated mineral and chemical composition against fresh rock (average porosity 0.4%). The lost area of major petroglyphs in the past up images carved to the present was calculated about 23.8%. And occurrence area of exfoliation indicated 1.2% of the whole petroglyphs. As a result of the chromaticity analysis, color of the major petroglyphs was changed brighter and yellower than fresh rock by chemical and biological weathering factors. Average ultrasonic velocity of petroglyphs was measured 2,865m/s. This result indicated that ultrasonic velocity decreased especially bottom of petroglyphs than measured result in 2003 year. The results of the evaluation for slope stability, it identified the possibility of toppling, planar and wedge failure in host rock. The 3D image analysis and modeling data of the cavern obtained for structural reinforcement.

• The Journal of Engineering Geology
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• v.22 no.2
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• pp.223-231
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• 2012

Many cut slopes are located near national highways, resulting in large annual damage to infrastructure from the collapse of cut slopes. Therefore, to effectively maintain cut slopes, high-risk slopes should be identified and monitored. In this paper, we evaluate the effectiveness of the management of cut slopes using the risk score calculated from cut-slope inventory data. The inventory survey, as a simple assessment of the characteristics of various slopes, was performed to collect basic data that could be obtained visually in the field for the management of cut slopes. This method is not a precise survey, and it was composed of the general status and characteristics of cut slopes, the inspector's assessment, and inventory data in order to estimate a risk score for each slope. In this paper, we calculated the risk score by investigating the present status of cut slopes adjacent to 10,461 national roads. In order to evaluate the effectiveness of using risk score data, we compared the score for stable slopes with those of failed cut slopes. Failed cut slopes occurred in sections with the highest risk score. The results show that risk score derived from the inventory survey of cut slopes are useful in the management of cut slopes with risk of failure and in monitoring large numbers of cut slopes.