• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.150-159
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• 2014

A simplified method for the calculation of buckling and vibrational characteristics of initially stressed rectangular plate and antisymmetric angle-ply laminated plates is presented in this paper using the natural frequencies under unloading state. The equation of motion of rectangular plate with two opposite edges simply supported is investigated on the basis of Rayleigh-Ritz method and Mindlin plate theory with effect of the curvature term. The relationships of the non-dimensional natural frequencies with initial stresses the coeffcients of critical buckling and the boundaries of the dynamic principal instability region can be characterized by the non-dimensional natureal frequencies under unloading state. Numerical examples are presented to verify the simplified equations and to illustrate potential applications of the analysis.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2006.09a
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• pp.37-45
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• 2006

우리나라에는 현재 고리, 월성, 영광 등 11기의 원자력 발전소가 운영되면서 전체 전력생산량의 40% 이상을 담당하고 있으며, 2006년까지는 12기가 추가 건설되어 총 23기의 원자력 발전소가 운영되어 국내 총 전력생산량의 절반 이상을 담당하게 될 예정이다. 하지만 이러한 원자력 발전은 필연적으로 인체에 유해한 각종 방사성 폐기물을 생산하게 되므로 이에 대한 처분기술은 대단히 높은 안전율을 고려하여 확보되어야 한다. 한국원자력연구소의 기초연구에 의하면 국내 실정상 지하 암반내 심층처분이 가장 유리한 시스템인 것으로 보고되고 있으며, 그 중에서도 심도 500m 이상의 고심도 지하 암반내에 터널을 뚫고 터널 바닥면에 처분공을 일렬로 굴착하여 이 처분공 내에 canister로 밀봉된 방사성폐기물을 유기하는 KBS-3 처분 시스템을 제안하고 있다. 본 연구에서는 KBS-3 처분 시스템을 고려할 경우, 필연적으로 야기되는 고심도 지하에서의 초기응력성분이 처분 시스템에 미치는 영향을 분석하기 위해 수치해석을 실시하였으며 이와 함께 제반 설계정수 중에서 초기응력값이 어떠한 비중을 차지하는지를 살펴보았다.

• Tunnel and Underground Space
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• v.32 no.1
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• pp.1-19
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• 2022

In this report, new standard, published by Japanese Geotechnical Society, on in-situ stress measurements by hydraulic fracturing was reviewed. In the standard, modification was made for the calculation of fracture re-opening pressure in consideration of fracture surface roughness and residual aperture. The standard also presents how much the system compliance influences the estimation of the fracture re-opening pressure and subsequent in-situ stresses. It is shown that the stiffer the rock mass is, the system compliance should be sufficiently small enough so as to obtain in-situ stress measurement with higher confidence.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.637-648
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• 2017

In this paper, the effects of initial built-in deformation and temperature deformation on the stress distribution of discontinuous precast concrete track slab under train load were examined. According to the results, when train load is put on a precast concrete slab with initial built-in deformation and deformation due to temperature gradient, the maximum tensile stresses develop at the upper side of slab in the slab center, edge center and corner of shear pocket; the stress distribution is different from that of the case under train load only. Therefore, to accurately predict the actual weak points and failure modes, one should calculate the stress under train load considering the initial built-in and temperature deformation of the slab.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.436-436
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• 2004

사용후 연료 건식 저장 용기가 낙하, 토네이도, 미사일, 홍수 및 지진으로 인한 사고에 대하여 전복이 발생되었을 때 강체 평면과 충돌에 의한 충돌 하중시의 구조 응력 평가하였다. 이를 위해 저장 용기의 무게 중심이 한계를 넘었을 때의 초기 전복 시작각을 무게 중심을 계산을 통해 구하였다. 상용 코드를 사용하여 전복 응력 해석 수행시 저장 용기의 강체 운동에 의하여 계산 시간이 길어지는 데, 이런 계산 시간을 줄이기 위해 일차 충돌 직전까지의 모델의 속도와 각속도 계산식을 이론적인 방법으로 구하여 해석 초기 조건으로 사용하는 방법에 대하여 제안하였다.(중략)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5C
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• pp.273-282
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• 2008

A series of analytical formula to compute settlements accounting for possible variations of initial effective stresses were derived. The comparison of computed values from conventional and newly-derived equations shows that computed settlements via the conventional equation unrealistically vary with the chosen number of layers in a clay stratum and also are 45~100% less than the value obtained from the newly-derived equation with exact mathematical integration.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.185-205
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• 1999

Hydraulic fracturing tests were performed in two inclined boreholes for the design of underground oil storages in Korea. Extensions of their application limits were expected through a precise comparison between the interpretation techniques for the vertical and the inclined boreholes. Especially, it was verified that the magnitude of in-situ stress can be varied even in the same rock mass with a variety of geographic/geotechnical characteristics. It was also demonstrated that its orientation can be changed even in the same borehole with the existence of explicit discontinuities.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.03a
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• pp.79-88
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• 2008

Since the hydraulic fracturing field testing method was introduced first to Korean geotechnical engineers in 1994, there have been lots of progresses in a hardware system as well as an interpretation tool. The hydrofracturing system of first generation was the pipe-line type, so it was not easy to handle. It had been modified to a wire-line system at their second generation. It was more compact one but it also needed an additional air-compressor. Our current system is much more compact and operated by all-in-one system, so it doesn't need an additional air-compressor. With a progress in a hardware system, the software for analyzing the in-situ stress regime has also been progressed. For example, the shut-in pressure, which is the most ambiguous parameter to be obtained from hydrofracturing pressure curves, can now be acquired automatically from the various methods. While the hardware and software for hydrofracturing tests are being developed during the last decade, the author could accumulate the field test results which can cover the almost whole area of South Korea. Currently these field data are used widely in a feasibility study or a preliminary design step for tunnel construction in Korea. Regarding the difficulties in a site selection and a test performance for the in-situ stress measurement at an off-shore area, the in-situ stress regime obtained from the field experiences in the land area can be used indirectly for the design of a sub-sea tunnel. From the hydrofracturing stress measurements, the trend of magnitude and direction of in-situ stress field was shown identically with the geological information in Korea.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.597-604
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• 2015

When a tunnel is constructed by drilling and blasting operation, the excavated perimeter becomes uneven due to overbreak at the drill holes so that the thickness of shotcrete tends to be irregular. In this case, the conventional stress analyses for tunnel lining of a uniform thickness cannot be readily applicable. In this study, the profile of tunnel perimeter assumed to be sinusoidal in order to simulate the uneven tunnel perimeter and to control the thickness of shotcrete by using the amplitude and wavelength. By adopting the sinusoidal function to a theoretical solution of stress analysis for uniform lining, the range of axial stress of irregular shotcrete can be estimated. The applicability of the approximate solution has been verified by performing a series of numerical analyses for various conditions. It is shown that the axial stress of shorcrete is highly dependent upon the irregularity of shotcrete, together with the ground property and initial stress conditions. It is also shown the shear stress is dependent upon the wavelength, and the stress condition becomes unfavorable where the thickness of shotcrete is relatively small. The approach developed in this study shows that the stress state where the thickness is relatively small is unfavourable, and it is necessary to take complementary measures when installing shotcrete after blasting.

• Journal of the Korean GEO-environmental Society
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• v.19 no.12
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• pp.47-58
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• 2018

Duncan & Chang(1970) proposed the Duncan-Chang model that a linear relation of transformed stress-strain plots was reconstituted from a nonlinear relation of stress-strain curve of triaxial compression test using hyperbolic theory so as to estimate an initial tangent modulus and ultimate deviator stress for the soil specimen. Although the transformed stress-strain plots show a linear relationship theoretically, they actually show a nonlinearity at both low and high values of strain of the test. This phenomenon indicates that the stress-strain curve is not a complete form of a hyperbola. So, if linear regression analyses for the transformed stress-strain plot are performed over a full range of strain of a test, error in the estimation of their linear equations is unavoidable depending on ranges of strain with non-linearity. In order to reduce such an error, a modified regression analysis method is proposed in this study, in which linear regression analyses for transformed stress-strain plots are performed over the entire range of strain except the range the non-linearity is shown around starting and ending of the test, and then the initial tangent modulus and ultimate deviator stresses are calculated. Isotropically consolidated-drained triaxial compression tests were performed on compacted weathered soil with a modified Proctor density to obtain their model parameters. The modified regression analyses for transformed stress-strain plots were performed and analyzed results are compared with results estimated by 2 points method (Duncan et al., 1980). As a result of analyses, initial tangent moduli are about 4.0% higher and ultimate deviator stresses are about 2.9% lower than those values estimated by Duncan's 2 points method.