• Geomechanics and Engineering
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• v.13 no.3
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• pp.489-504
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• 2017

The localized shear and the slip lines are easily observed in elastic-brittle-plastic rock. After yielding, the strength of the brittle rock suddenly drops from the peak value to the residual value, and there are slip lines which divide the macro rock into numbers of elements. There are slippages of elements along the slip lines and the displacement field in the plastic region is discontinuous. With some restraints, the discontinuities can be described by the combination of two smooth functions, one is for the meaning of averaging the original function, and the other is for characterizing the breaks of the original function. The slip lines around the circular opening in the plastic region of an isotropic H-B rock which subjected to a hydrostatic in situ stress can be described by the logarithmic spirals. After failure, the deformation mechanism of the plastic region is mainly attributed to the slippage, and a slippage parameter is introduced. A new analytical solution is presented for the plane strain analysis of displacements around circular openings. The displacements obtained by using the new solution are found to be well coincide with the exact solutions from the published sources.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.13-22
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• 2007

This study was carried out to scrutinize possibility of manufacturing pitch pine (Pinus rigida) glued laminated timber in order to add values of pitch pine trees. Also, it was investigated to improve bending performance of pitch pine glulam. Pitch pine was imported as one of major plantation species in Korean peninsula. Machine stress rated grades of pitch pine lumber mostly ranged between E7 and E9. which grades were more or less inferior to producing high quality glulam. However, the adhesive properties between pitch pine and pitch pine, and between pitch pine and Japanese larch (Larix kaempferi Carr.), such as shear bond strength, wood failure rate and de-lamination rate of bonded layer submerged in cold and boiling water, were higher than Korean Standard criteria. These properties are essential for manufacturing glulam with single species or multiple species. The modulus of rupture (MOR) of pitch pine glulam exceeded the criterion of Korean Standard for glulam strength grade but modulus of elasticity (MOE) was lower than the criterion. On the other hand, the bending performances (MOR and MOE) were improved 20 percent by mixing with Japanese larch laminar. It is effective to arrange higher quality Japanese larch laminar at the outer layer of glulam for improving bending performances. In conclusion, it is possible to use low quality pitch pine as laminar of structural glulam for adding values of pitch pine.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.4
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• pp.369-376
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• 2003

In this paper, a nonlinear structural analysis for the composite structure composed of the spent nuclear fuel disposal canister and the 50㎝ thick bentonite buffer is carried out to predict the collapse of the canister while the horizontal symmetric sudden rock movement of 10㎝ is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Elastoplastic material model is adopted. Drucket-Prager yield criterion is used for the material yield prediction of the bentonite buffer and von-Mises yield criterion is used for the material yield prediction of the canister(cast iron, copper). Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffet, the canister structure still endures elastic small strains and stresses below the yield strength. Hence, the 50㎝ thick bentonite buffet can protect the canister safely against the 10㎝ sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the canister structure due to the shear deformation of the bentonite buffer.

• Journal of the Korean Geotechnical Society
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• v.31 no.2
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• pp.65-73
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• 2015

The bank revetment work which is conducted on the slope of river bank to protect against flowing water as a geotechnical structure has been applied as an average value of critical tractive force based on domestic and international standard design. Currently, an appropriate evaluation is needed for the hydraulic stability and geotechnical behavior analysis of bank revetments because of the effects of climate change and ambiguous design criterion. This study has compared the critical tractive forces of soil improvement material and conventional materials used for the bank revetment work. Through various experiments, the shear strength of mixtures with soil improvement material was investigated by curing time and mixture ratio. It was found that the critical tractive force of the mixture obtained from a scour test is suitable to the reinforcement of the slope of river bank which has problems such as seepage erosion and scour.

• Geotechnical Engineering
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• v.3 no.2
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• pp.55-70
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• 1987

An analytical solution procedure is described to estimate the developed passive lateral earth Pressures behind a vertical rigid retaintng wall rotating about its toe into a mass of cohesionless soil. Various stases of wall rotation, starting from an at-rest state to an initial Passive state to a full Passive state, are considered in the analysis. Condition of failure defined by a modified Mohr-coulomb criterion, together with equilibrium conditions, is used to obtain the necessary equations for the solution. Using methods of stress characteristics and numerical finite difference, a complete solution within and on the boundaries of the entire solution domain is made possible. The variations of the soil shear strength and the wall friction at various depths and stages of wall rotation are also taken into account in the analysis. The results predicted by the developed method of analysis are compared with those obtained from the experimental model tests on loose and dense sand. The comparisons show good agreements at various stages of retaining wall rotation Fin- ally, results of analytical parametric study are presented to demonstrate the effects of wall fric- tion on the resultant thrust and distribution of developed lateral earth pressures.

• Journal of the Korean Geotechnical Society
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• v.28 no.4
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• pp.35-42
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• 2012

This paper evaluates the effect of anisotropic conductivity on the seepage face and reliability index of an homogeneous dam with and without toe drain. The analysis are conducted under steady state saturated-unsaturated seepage condition using finite element method. Various anisotropic conductivity ratios were interpreted under such conditions as the vertical conductivity is reduced while the horizon conductivity is fixed. The shear strength of soil is defined by the modified Mohr-Coulomb failure criterion. The analysis results demonstrate that the length of seepage face and reliability index at the downstream and upstream of the dam increase with an increasing anisotropic ratio. These results of the seepage face and reliability index, however, depend on the total head difference between the upstream slope and downstream toe. The difference in seepage face and reliability index is attributed to the different equipotential head with different anisotropic ratios of the dam material.

• Ocean and Polar Research
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• v.36 no.4
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• pp.487-494
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• 2014

Deep-seabed test miner operated by a self-propelled mining system moving on soft soil is an essential device to secure floating and towing performances. The performances of the tracked vehicle are seriously influenced by noise factors such as the shear strength of the seafloor, bottom current, seafloor slope, speed of tracked vehicle, reaction forces of flexible hose, steering ratio, etc. Due to uncertainties related to noise factors, the design of a deep-sea manganese nodules test miner that satisfies target reliabilities is difficult. Therefore, reliability-based design optimization (RBDO) is required to guarantee system reliability under circumstances where uncertainties related to noise factors prevail. Among noise factors, the bottom current, a bimodal distribution, is censored due to the observation limit of measurement devices. Therefore, estimated distribution of the bottom current is inaccurate without considering these characteristics and the result of RBDO cannot be guaranteed. In this paper, we define censored data as unknown values over the limit of observation. If this data is estimated by using Akaike information criterion (AIC) that cannot consider the characteristics of censored data, the distribution of estimated data cannot guarantee accurate reliability. Therefore, censored AIC that can consider the characteristics of data is used to estimate accurate distribution of the bottom current. Finally, RBDO, under circumstances where uncertainties related to noise factors combined censored data are present, is performed on the mobility of a deep-sea manganese nodules test miner.

• Journal of the Korean Geotechnical Society
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• v.29 no.12
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• pp.35-44
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• 2013

In this study, a particle method without using grid was applied for analysing large deformation problems in soil flows instead of using ordinary finite element or finite difference methods. In the particle method, a continuum equation was discretized by various particle interaction models corresponding to differential operators such as gradient, divergence, and Laplacian. Soil behavior changes from solid to liquid state with increasing water content or external load. The Mohr-Coulomb failure criterion was incorporated into the particle method to analyze such three-dimensional soil behavior. The yielding and hardening behavior of soil before failure was analyzed by treating soil as a viscous liquid. First of all, a sand column test without confining pressure and strength was carried out and then a self-standing clay column test with cohesion was carried out. Large deformation from such column tests due to soil yielding or failure was used for verifying the developed particle method. The developed particle method was able to simulate the three-dimensional plastic deformation of soils due to yielding before failure and calculate the variation of normal and shear stresses both in sand and clay columns.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1C
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• pp.53-63
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• 2011

This paper investigates the effects of tunnelling-induced ground movements on nearby structures, considering soil-structure interactions of different ground (loose sand, dense sand, soft clay, stiff clay) and construction conditions (ground loss). The response of four-story block structures, which are subjected to tunnelling-induced ground movements, has been investigated in different ground and construction conditions (ground loss) using numerical analysis. The structures for numerical analysis has been modelled using Discrete Element Method (DEM) to have real cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The response of four-story block structures has been investigated with a ground movement magnitude and compared in terms of ground and construction conditions (ground loss) considering the magnitude of deformations and cracks in structures. In addition, the damage levels, which are possibly induced in structures, has been provided in terms of ground and construction conditions (ground loss) using the state of strain damage estimation criterion (Son and Cording, 2005). The results of this study will provide a background for better understandings for controlling and minimizing building damage on nearby structures due to tunnelling-induced ground movements.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.146-157
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• 2018

Over the last 10 years, the number of disasters has been increasing in Korea. As a result, the need for temporary residences or shelters for disaster conditions is increasing. In this study, post-disaster refugees housing was developed using lightweight composite panels that are lighter than the materials that make up the existing shelter. To accomplish this, the structural performance of the lightweight composite panel was validated. Among the performance tests on the panels, the transverse load test was conducted according to the ASTM E 72 criteria. As a result of the experiment, when each specimen was subjected to a uniformly distributed load, the allowable load was determined according to the span. All the experiments were ended due to a loss of adhesive at the junction of the skin and core. Further analysis was conducted to calculate the shear stress when the junction was dropped. The mean shear stress at the adhesive surface of a specimen, 150 mm and 200 mm in thickness, was 0.0170MPa and 0.0156MPa, respectively. This suggests that similar values were obtained from panels of equal thickness. In addition, this stress provides a criterion of judgment that could be used to inspect the structural performance of the panels. The performance of the panel was evaluated based on the allowable load, but it may be possible to increase the strength of the lightweight composite panel by improving the joining method to avoid separation from the junction.