• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.6
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• pp.697-705
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• 2020

This paper deals with an analysis of crustal movement for the sourthern part of Korean peninsula using GNSS (Global Navigation Satellite System) data. An earthquake of more than 5.0 occurred in the southeastern region of the Korean Peninsula, and it is necessary to evaluate the risk of earthquakes in various ways.In order to reveal long-term tectonic movement patten in Pohang and Gyeongju provinces, we derived crustal movement parameters related with elastic theory. We used GAMIT/GLOBK for analyzing seven-year interval GNSS data of CORS (Continuously Operating Reference Stations). The azimuth of velocity vectors trended generally about 110° with an mean magnitude of 31mm/yr.The main characteristics of the strain change for seven-year in Korea obtaind from our study. Direction of the principal axis of the maximum compression is ENE-WSW as a whole, through there are some exceptions. The mean rate of the maximum shear strain change is (0.11±0.07)μ/yr, that is approximately one third that of Chubu district, Central Japan. Taking into account our results, the mean rate of maximum shear in southern part of Korean peninsula is considered as reasonable. The mean azimuth of principal strain is about (85.4°±26.8°). There are some exceptions of azimuth because the average azimuth differ from the left and right side in Yangsan fault which are about (73.2°±21.5°) and (105.2°±17.0°) respectively, It is noteworthy that the high seismicity areas in the southern part of Korea peninsula almost coincides with the area of large strain rate. As a conclusion, it could be stated that the our study represents the characteristics of crustal deformation in the southern part of peninsula, and contributes to the researches on earthquake disaster management.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.103-111
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• 2008

Soils naturally contain grains of different minerals which may be dissolved under chemical or physical processes. The dissolution leads changes in microstructure of particulate media, such as an increase in local void or permeability, which affects the strength and deformation of soils. This study focuses on the small strain stiffness characteristics of vanishing mixtures, which consist of sand and salt particles at different volume fractions. Experiments are carried out in a conventional oedometer cell (Ko-loading) integrated with bender elements for the measurement of shear waves. Dissolutions of particles are implemented by saturating the mixtures at various confining stresses. Axial deformation and shear waves are recorded after each loading stage and during dissolution process. Experimental results show that after dissolution, the vertical strain and the void ratio increase, while the shear wave velocity and small strain shear modulus decrease. The decrease of the velocity results from the void ratio increase and particle contact decrease. The process monitoring during dissolution of the particles shows that the vertical strain dramatically increases at the beginning of the saturation process and converges after vanishing process finishes, and that the shear wave velocity decreases at the beginning and increases due to the particle reorientation. Specimens prepared by sand and salt particles are proved to be able to provide a valuable insight in macro structural behaviors of the vanishings mixtures.

• Composites Research
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• v.17 no.5
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• pp.39-46
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• 2004

In this study, the strength of spatially reinforced composites (SRC) are predicted by using stiffness reduction for each structural element composed of a rod stiffness in each direction and a matrix stiffness proportional to its rod volume fraction. Maximum failure strain criteria is applied to rod failure, and modified Tsai-Wu failure criteria to matrix failure. The material properties composed of the tensile failure strain of a rod, the compressive failure strain of 3D SRC, the tensile and compressive strength of the 3D SRC in the $45^{\cir}$ rotated direction from a rod and the shear strength of the 3D SRC are measured to predict the SRC strength. The strength distributions of the 3D/4D SRC in rod and off-rod direction have the largest and the smallest values, respectively. A variable load step is selected to increase an efficiency of strength distribution calculation. Uniform load step is applied when a load history is needed. The results of compressive strength from analysis and experiment show the 18 % difference though the initial slop is coincident with each other.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.1
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• pp.59-78
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• 2024

In tunnel construction, the stability is evaluated by the settlement of adjacent structures and ground, but the shear strain of the ground is the main factor that determines the failure mechanism of the ground due to the tunnel excavation and the change of the operating load, and can be used to review the stability of the tunnel excavation and to calculate the reinforcement area. In this study, a twin tunnel excavation was simulated on a soft ground in an urban area through a laboratory model test to analyze the behavior of the twin tunnel excavation on the adjacent pile grouped foundation and adjacent ground. Both the displacement and the shear strain of ground were obtained using a close-range photogrammetry during laboratory model test. In addition, two-dimensional finite element numerical analysis was performed based on the model test. The results of a back-analysis showed that the maximum shear strain rate tends to decrease as the horizontal distance between the pillars of the twin tunnel and the vertical distance between the toe of the pile group and the crown of the tunnel were decreased. The impact of the second tunnel on the first tunnel and pile group was decreased as the horizontal distance between the pillars of the twin tunnel was increased. In addition, the vertical distance between the toe of the pile group and the crown of the tunnel had a relatively greater impact on the shear strain results than the horizontal distance of the pillars between the twin tunnels. According to the results of the close-range photogrammetry and numerical analysis, the settlement of adjacent pile group and adjacent ground was measured within the design criteria, but the shear strain of the ground was judged to be outside the range of small strain in all cases and required reinforcement.

• Journal of the Korean Geotechnical Society
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• v.30 no.2
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• pp.5-18
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• 2014

Depending on the underground load support mechanism, anchors are classified as friction anchors, bearing plate anchors and the recently developed combined friction-bearing plate anchors which combine the characteristics of both the friction and bearing plate type anchors. Even though numerous studies have been performed on bearing plate anchors, there were only few studies performed to observe the failure surface of bearing plate anchors. Furthermore most of the soil materials used on these tests were not real sand but carbon rods. In this study, sand was placed in the soil tank and laboratory tests were performed with bearing plate anchors installed with an embedment depth (H/h) ranging from 1~6. The variation in the pullout capacity and the behaviour of soil with the embedment depth (H/h) were observed. Ground deformation analysis program was also used to analyze soil displacement, zero extension direction, maximum shear strain contours. It was determined from the analysis of the results that at ultimate pullout resistance the deformation was 5 mm and the failure surface occurred in a narrower area when compared with results of the previous researches. It was also observed that the width of the fracture surface gradually becomes wider and expands up to the surface as the deformation increases from 10 mm to 15 mm.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.6
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• pp.521-531
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• 2014

This paper is a study for behaviour of cavern type anchorage tunnels for suspension bridges with cable tension. Anchorage behaviour, design method for anchorage, and failure surface angle, ${\delta}$ are analyzed by comparing numerical analysis results and ultimate pullout capacities($P_u$) using bilinear corelation equation. Results show that design depths for cavern type anchorage tunnels are easily checked with linear relationships for $P/{\gamma}/H$ vs. displacement and $P_u/{\gamma}/H$ vs. H/b. The analysis results of maximum shear strain distribution and plastic status show that failure shapes are closer to circular arc model than soil cone model which frequently used. To an easy calculation of the ultimate pullout capacity, we propose a simple bilinear failure model in this study. The calculated ultimate pullout capacities from the proposed bilinear corelation equation using two failure angles results are similar to the ultimate pullout capacities from numerical analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.123-131
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• 2018

This study analyzed the collapse course of a mud stone cut slope during the construction of a express and suggested a countermeasure. Experiments were carried out on bedrock mudstone to investigate the engineering characteristics and the slope stability analysis at the time the design was reviewed. In addition, stability analysis, considering the strength softening characteristics of the slope due to the Swelling-Slaking phenomenon, was also performed. As a result of the Swelling-Slaking test, the slake durability was Low-Medium, and the swell potential was Very Low. A review of the stability analysis performed at the time of the design showed different results from the actual results because LEM analysis had been performed without considering the engineering characteristics of mudstone. As a result of additional stability analysis considering the strength softening characteristics, the slope collapse point and the maximum shear strain point of the stability analysis were the same and the standard safety factor was not satisfied. As a countermeasure, a slope mitigation method was found to be most appropriate. The mitigation slope was calculated by Finite element Analysis. A comparison with BIPS to determine the applicability of a mitigation slope revealed most of the unconsolidated mudstone.