• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.600-602
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• 2012

폐단면리브 적용 판의 면내 압축좌굴 거동 특성 중에서 보강재 강성이 작고 비교적 낮은 임계하중을 받는 경우 전체기둥좌굴 거동이 예상된다. 본 논문은 폐단면리브 단면 강성의 고려 방안에 따라 단순 보 유사모형을 정립하고 전체좌굴에 대해 에너지 근사해법을 적용하여 전체좌굴강도 근사해를 유도하기 위한 기초적인 연구방안으로써 검토한 내용을 소개하고자 한다. 유사모형의 폐단면리브 중심에서 휨강성이 발휘되는 것으로 가정하여 모형화 하였다. 폐단면리브 보강판의 프로토타입 모델에 대해 직교이방성 $[(0^{\circ})_4]_s$와 Cross-ply $[(0^{\circ}/90^{\circ})_2]_s$ 적층단면을 각각 고려한 유한요소 해석을 실시하였다. U리브 단면강성에 따른 복합적층 보강판의 탄성좌굴강도 해석결과를 근사해 공식과 비교하고 U리브로 보강된 복합적층판의 좌굴모드 변화양상을 수치해석적으로 검토하였다.

• Geotechnical Engineering
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• v.3 no.2
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• pp.17-28
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• 1987

Reliability of the cone penetration test (CPT) for estimating shear strength of marine soils is investigated in this paper. For sands, the uncertainty about the angle of internal friction is analyzed. It includes the spatial variation of the soil and the model error in the equation used for interpretation. The most serious uncertainty encountered was the error in the interpretative models. Different methods of interpretation gave quite different values. Subjective opinion was introduced to combine all the interpretative models in a systematic manner. For clays, the undrained Shear Strength from the CPT results is usually =derived by empirical correlations between cone resistance and untrained shear strength from laboratory tests or field vane tests, expressed in terms of cone factor and function of overburden pressure. The uncertainty of the undrained shear strength is caused by data scatter of the cone factor in the correlation, model error of the cone factor, effect of anisotropy, and spatial variability of cone resistance. Among these uncertainties, the most serious one was the data scatter of the cone factor in the .correlation. Between the laboratory test and the field vane test used for correlation, the field vane test was more reliable.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.133-140
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• 2003

The sandwich plate has been widely used as an efficient structural member because it has high strength-to-weight and high stiffness-to-weight ratios. To properly design the aluminum extrusion plate , it is necessary to analyze structural behaviors of the extrusions, however, the aluminum extrusions have been rarely studied until now. In the optimization process through numerous iterative calculations, finite element analysis of the sandwich plate with hollow core section requires a considerable amount of computation time and cost. In this paper, the aluminum extrusion plate with truss-core is transformed into an equivalent homogeneous orthotropic plate with appropriate elastic constants. The procedure to evaluate accurate equivalent elastic constants is also established. Using these elastic constants, simple theoretical formulas of the stresses and deflection are proposed in case of the simply-supported orthotropic thick plate under uniform pressure. Through the comparison with the results by commercial FEM code(ANSYS), it is verified that the proposed simpified formula has a good efficiency and accuracy.

• Geotechnical Engineering
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• v.14 no.4
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• pp.33-46
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• 1998

Anisotropy of stiffness, from extremely small strains to post-failure strains, of isotropically consolidated air-pluviated sands in plane strain compression was studied by using the newly developed instrumentation for small strain measurements. Seven types of sand of the world-wide origins were tested, which have been extensively used for research purposes. Stress-strain at the specimen boundaries. It was found that the maximum Young's modulus $E_{max}$ was irrespective of the angle $\delta$ of the $\delta_1$ direction relative to the bedding plane. However, the normalized$ E_{max}$ was varied with the types of sand. Furthermore, the dependency of the strain and stress level on the stiffness was increased as $\delta$ decreased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.04a
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• pp.181-187
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• 1997

고강도 알루미늄 합금 링롤재의 급냉, 링 팽창(expansion) 및 링 압축(compression) 응력제거처리후 잔류응력을 예측하기 위하여 2차원 축대칭 열해석 및 탄소성 해석을 수행하였다. 급냉 및 응력제거처리 후 2단 과시효 처리(T73)된 링롤재에 대하여 3단계 절단법(Three step sectioning method)을 적용하여 링롤재의 두께에 따른 잔류응력 분포를 측정하였으며, 측정결과를 급냉 및 응력제거처리후 잔류응력 해석결과와 비교분석하였다. 링의 급냉후 원주 및 축방향의 잔류응력 해석값은 T73후 측정값과 비슷한 경향을 보였으며, 링의 내면과 외면에서 압축응력을 나타내었고 중심에서 인장응력을 나타내었다. 잔류응력은 링 팽창(T7351) 및 링 압축(T7352) 적용후 T73에 비해 현저히 감소하였으며, 축방향의 제거 효과가 원주방향보다 우수하게 나타났다. 또한 링 압축에 의한 제거효과가 링 팽창보다 크게 나타났다. 링롤재의 응력제거처리는 제거 효과 및 실용성 측면에서 링 압축 공정이 유리하며, 치수제어 및 장비용량 측면에서 링 팽창 공정이 유리하다는 결론을 얻었다.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.149-156
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• 2020

Permeation grouting effectively enhances soil strength and decreases permeability of soil; however, the flow of grout is heavily affected by anisotropy of hydraulic conductivity in layers. Therefore, this study investigates the effect of permeability anisotropy on the effective radius of horizontal permeation grout using computational fluid dynamics (CFD). We modeled the horizontal permeation grout flow as a two-phase viscous fluid flow in porous media, and the model incorporated the chemical diffusion and the viscosity variation due to hardening. The numerical simulation reveals that the permeability anisotropy shapes the grout bulb to be elliptic and the dissolution-driven diffusion causes a gradual change in grout pore saturation at the edge of the grout bulb. For the grout pore saturations of 10%, 50% and 90%, the horizontal and vertical radii of grout bulb are estimated when the horizontal-to-vertical permeability ratio varies from 0.01 to 100, and the predictive model equations are suggested. This result contributes to more efficient design of injection strategy in formation layers with permeability anisotropy.

• Tunnel and Underground Space
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• v.26 no.5
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• pp.363-374
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• 2016

All five independent elastic constants of a transversely isotropic rock sometimes need to be determined from a single specimen. Saint-Venant approximation has been widely used for a long time in the analysis of single specimen test. This paper has proven how this empirical equation can be mathematically transformed into a form of the apparent Young's modulus based on theory of elasticity. The transformed equation is a monotonous function on anisotropic angle and can be useful in the analysis of the in-situ stress measurement in an anisotropic rock mass. The estimations of data in literatures have shown that the measured values of $G^2$ are uniform on anisotropic angles and smaller than that of Saint-Venant's case. This decrement may be caused by sliding of the interface of strata and the decrement rate is inferred to relate well with the combination of bonding condition of strata and strength of rock material. Accumulation of these kinds of studies in the future enables to define the decrement and to determine elastic constants of a transversely isotropic rock from a single specimen from modifying Saint-Venant approximation.

• Tunnel and Underground Space
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• v.28 no.5
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• pp.442-456
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• 2018

Scaled model tests were performed to evaluate the reinforcement effect of rock bolts in anisotropic rock mass. For this purpose, two tunnel cases were experimented which had different tunnel sizes, rock strengths, anisotropic angles and coefficients of lateral pressure. The fully grouted rock bolts of the D25 deformed bar were modeled as the basting pins with bead and were systematically installed at the roof and the side wall of the model tunnel. As results of the first case experimentations, the unsupported model showed initial crack at the roof of tunnel, but the supported model with rock bolts showed initial crack at the floor of tunnel where rock bolts were not installed. The crack initiating pressure and the maximum pressure of the supported model with rock bolts were 11% and 7% larger than those of the unsupported model, respectively. Moreover, the effect of the existing discontinuities in anisotropic rock mass on the fracture behavior of tunnel was reduced in the supported model, and so the reinforcement effect of rock bolt turned out to be experimentally verified. As results of the second case experimentations considering different support patterns, the crack initiating pressures of models were larger and the reduction ratios of tunnel area according to applied load were smaller as the length and the quantity of rock bolts were larger. Therefore, it was found that the performance of the rock bolts turned out to be improved as they were larger.

• The Journal of Engineering Geology
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• v.8 no.2
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• pp.153-161
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• 1998

An anisotropic characteristics of stratified sedimentary rocks should be considered in the design of tunnel. The second line of Taegu subway is under construction through the sedimentary rocks which is stratified by alternation of shale and sandstone, and Tongsoe over bridge road is planned to be constructed along the subway line. Thus the subway twin tunnels will be subjected by the bridge load of 76.2 MN per pier that will be placed in between the twin tunnels of the subway line. A numerical analysis is carried out for the stability of the twin tunnel, and the result shows that the maximum principal stress of surrounding ground is increased by 5∼6 MPa and the additional displacement of concrete lining is reached up to 8∼10mm due to the external bridge load. For the safety operation of the subway, reinforcement of the tunnel structure is highly recommended.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.11b
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• pp.31-50
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• 2002

The sedimentary rocks deposited in Taegu and Kyongbuk region consist of various rocks such as the shale, mudstone, siltstone and sandstone. The characteristics of the sedimentary rocks are distinguished from those of igneous rocks and metamorphy rocks for the stratum caused by deposit environment. This study investigated engineering characteristics of the anisotropy, weathering rock and filled rock joints in the notable features of sedimentary rocks.