• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2C
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• pp.73-80
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• 2006

The shear behavior of four different interfaces consisting of four types of geosynthetics was investigated, and both static and dynamic test for the geosynthetic interfaces were conducted. The monotonic shear experiments were performed by using an inclined board apparatus and large direct shear device. The interface shear strength obtained from the inclined board test was compared with calculated values from large direct shear tests. The comparison results indicated that direct shear tests show high possibility to over-predict the shear strength in the low normal stress range where direct shear tests are not performed. Curved failure envelopes were also obtained for interface cases where two static shear tests were conducted. By comparing the friction angles measured from three tests, i.e. direct shear, inclined board, and shaking table test, it was found that the friction angle might be different depending on the test method and normal stresses applied in the research. Therefore, it was concluded that the testing method should be determined carefully by considering the type of loads and the normal stress expected in the field with using the geosynthetic materials installed in the site.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.337-342
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• 2010

Generally most sluice gates are closed and opened by a mechanical winch, a winch using an oil-pressure, or a winch mixing both. Because of their size and structure, they should be safely operated with more than two pulling devices helping each other. At the moment of their opening and closing, there usually occur some additional loads to the structure which cannot be exactly measurable at the stage of designing. Such additional loads can cause the sluice gate to be unbalanced and make it hard to open and close the gate, and by also overloading a winch, they can inflict a significant damage to the safety of the sluice gate. This paper explains a FDC(Force-Displacement Control) system which simultaneously considered the oil-pressure and displacement in order to evenly distribute the force and make a winch balanced at the opening and closing motion. This FDC system was implemented by means of the PID(Proportional Integral Derivative) function of XG 5000 program. It was experimented on a model of the sluice gate winch with the hydraulic oil pressure cylinder. The experiments showed that the developed FDC system made the winch of hydraulic oil pressure cylinder open and close cooperatively in spite of various external loads. Therefore the FDC system is proven effective when it is applied to a winch of sluice gate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.251-258
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• 2009

In this study, the optimum design conditions for embankment construction on soft clay layer improved by soil compaction pile (SCP) are discussed by comparing the practical design method to the reliability design which is based on the loss function and advanced first order second moment (AFOSM) method. The results are summarized as follows; 1) the relationship between safety factor and failure probability becomes heavy exponentially, failure probability decreases rapidly till 1% approximately until safety factor is smaller than 1.2 and after then, failure probability decrease gradually along the increase of the safety factor. The design safety factor of 1.2 may be the critical value that has been established on considering both relationships appropriately, 2) the safety factor of 1.15 at the minimum expected total cost is a little smaller than the design safety factor of 1.2 and the failure probability is about 1%, 3) the sensitivities of the ratio of stress share and the internal friction angle of sand is larger than the variables related the undrained shear strength of soft layer. This result means that the distribution characteristic of n and ${\phi}$ influences on the stability analysis considerably and they should be considered necessarily on stability analysis of embankment on soft layer improved by SCP, 4) new failure points of the input variables at the design safety factor of 1.2(below failure probability of 0.1~0.3%) is far 1~2 times of standard deviation from the initial design values of themselves.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.531-541
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• 2023

The most important thing in the 4th industry, AI era, and smart construction era is digital data. Basic data in the civil engineering field begins with ground investigation. The Ministry of Land, Infrastructure and Transport operates the Geotechnical Information Database Center to manage ground survey data, including drilling but the focus is on data distribution. This study seeks to devise a plan for long-term use of the results of drilling investigation conducted for the design and construction of various construction projects. For this purpose, a pilot area was set up and a 'geotechnical design parameters digital map' was created using some geotechnical design parameters from the drilling investigation data. Using the developed algorithm, a digital map of friction angle and permeability coefficient for the hard rock stratum in the pilot area was created. Geotechnical design parameters digital map can identify the overall condition of the ground, but reliability needs to be improved due to the lack of initial data input. Through additional research, it will be possible to produce a more complete geotechnical design parameters digital map.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.573-586
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• 2023

Joints or weak planes can induce anisotropy in the strength and deformability of fractured rock masses. Comprehending this anisotropic behavior is crucial to engineering geology. This study used plaster as a friction material to mold specimens with a single joint. The strength and deformability of the specimens were measured in true triaxial compression tests. The measured results were compared with three-dimensional numerical analysis based on the distinct element method, conducted under identical conditions, to assess the reliability of the modeled values. The numerical results highlight that the principal stress conditions in the field, in conjunction with joint orientations, are crucial factors to the study of the strength and deformability of fractured rock masses. The strength of a transversely isotropic rock mass derived numerically considering changes in the dip angle of the joint notably increases as the intermediate principal stress increases. This increment varies depending on the dip of the joint. Moreover, the interplay between the dip direction of the joint and the two horizontal principal stress directions dictates the strength of the transversely isotropic rock mass. For a rock mass with two joint sets, the set with the steeper dip angle governs the overall strength. If a rock bridge effect occurs owing to the limited continuity of one of the joint sets, the orientation of the set with longer continuity dominates the strength of the entire rock mass. Although conventional three-dimensional failure criteria for fractured rock masses have limited applicability in the field, supplementing them with numerical analysis proves highly beneficial.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.79-85
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• 2023

Skid resistance pavement is an accessory to the road and is a facility for the safe driving of cars by increasing the skid resistance of road pavement. In particular, in bad weather conditions such as snow, rain, and black ice, the skid resistance performance of skid resistance pavement greatly affects the safety of road traffic and drivers. However, BPT(British Pendulum Tester) has a test area of only 0.009 m², making it difficult to represent the overall packaging surface. A reliable method of evaluating slip resistance performance is needed for maintaining non-slip packaging. In this study, the conventional BPT test and the skid resistance performance evaluation method of the PFT(Pavement Friction Tester) and µGT(Micro Grip Tester) tests were compared through guidelines and standard investigations and applied to the field skid resistance performance evaluation. In addition, skid resistance pavement with different skid resistance performance was installed at the test-bed and actual road demonstration sites to compare BPN(British Pendulum Number), SN(Skid Number), GN(Grip Number), and to derive correlations for each performance evaluation method. As a result of the experiment, SN and GN showed similar skid resistance performance, and the GN value was derived similar to BPN × 0.01.

• Phonetics and Speech Sciences
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• v.15 no.3
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• pp.59-67
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• 2023

This study aimed to propose an appropriate evaluation method for the perceived level of speech disfluency based on sound prolongation (i.e., increased duration of segments). To this end, 34 Korean-speaking adults (9 males, 25 females, average age: 32.9 yrs.) participated as raters in this study. The participants listened to sentences containing a total of 25 stimuli with the Korean voiceless fricative /s/ extended by 80-ms increments up to 2,000 ms (i.e., 285 ms, 365 ms., ..., 2,125 ms, 2,205 ms), and evaluated them using an equal-appearing interval scale (EAI, 1-7 points, where 1 represents "normal" and 7 represents "severe"). Subsequently, based on the interval-scale results, the sentence stimuli with the prolonged voiceless fricative corresponding to the mild-to-moderate level (rated as 4 points) were selected as the reference modulus for direct magnitude estimation (DME). After scatter plots were created for the two evaluation results, the relationship between the two measured mean values was analyzed using a curve estimation method for the observed data with the highest R²-value to determine whether a linear or curvilinear approximation fit the data better. A curvilinear relationship between the two evaluation results was indicated, suggesting that DME is a more appropriate evaluation method than the EAI scale for assessing the perceived level of disfluency based on sound prolongation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.216-225
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• 2023

This paper describes the finite element analysis and die design change of cold heading punching process to increase the cold forging tool life and reduce the tool wear and stress concentration. Through this study, the optimization of punch tool design has been studied by an analysis of tool stress and wear distribution to improve the tool life. Plastic deformation analysis was carried out in order to understand the cold heading process between tool and workpiece stress distribution. Cold heading punch die design was set up to each process with different four types analysis progressing, the cold heading punch dies shapes with combination of point angle and punch edge corner radius shapes of cold forging dies, punch die material properties and frictional coefficient. The design parameters of point angle and corner radius of punch die geometry, die material properties and frictional coefficient were selected to apply optimization with the DoE (design of experiment) and Taguchi method. DoE and Taguchi method was performed to optimize the cold heading punch die design parameters optimization for bolt head cold forging process, it was possible to expect an reduce the cold heading punch die wear to the 37 % compared with current using cold heading punch in the shop floor.

• Journal of the Korean Geotechnical Society
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• v.39 no.12
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• pp.37-46
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• 2023

Dynamic soil properties are essential factors for predicting the detailed behavior of the ground. However, there are limitations to gathering soil samples and performing additional experiments. In this study, we used an artificial neural network (ANN) to predict dynamic soil properties based on static soil properties. The selected static soil properties were soil cohesion, internal friction angle, porosity, specific gravity, and uniaxial compressive strength, whereas the compressional and shear wave velocities were determined for the dynamic soil properties. The Levenberg-Marquardt and Bayesian regularization methods were used to enhance the reliability of the ANN results, and the reliability associated with each optimization method was compared. The accuracy of the ANN model was represented by the coefficient of determination, which was greater than 0.9 in the training and testing phases, indicating that the proposed ANN model exhibits high reliability. Further, the reliability of the output values was verified with new input data, and the results showed high accuracy.

• Journal of the Korean Geotechnical Society
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• v.40 no.1
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• pp.5-14
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• 2024

PHC piles demonstrate superior resistance to compression and bending moments, and their factory-based production enhances quality assurance and management processes. Despite these advantages that have resulted in widespread use in civil engineering and construction projects, the design process frequently relies on empirical formulas or N-values to estimate the soil-pile friction, which is crucial for bearing capacity, and this reliance underscores a significant lack of experimental validation. In addition, environmental factors, e.g., the pH levels in groundwater and the effects of seawater, are commonly not considered. Thus, this study investigates the influence of vibrating machine foundations on PHC pile models in consideration of the effects of varying pH conditions. Concrete model piles were subjected to a one-month conditioning period in different pH environments (acidic, neutral, and alkaline) and under the influence of seawater. Subsequent repeated direct shear tests were performed on the pile-soil interface, and the disturbed state concept was employed to derive parameters that effectively quantify the dynamic behavior of this interface. The results revealed a descending order of shear stress in neutral, acidic, and alkaline conditions, with the pH-influenced samples exhibiting a more pronounced reduction in shear stress than those affected by seawater.