• The Journal of Engineering Geology
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• v.30 no.2
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• pp.147-160
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• 2020

Unsaturated hydraulic conductivity of near-surface unconsolidated layers depends on the physical properties and water content of the unconsolidated layers. So far, many studies have been conducted on the unsaturated hydraulic conductivity of near-surface unconsolidated layers. However, researches on hydraulic conductivity of unsaturated fractured rocks have been relatively rare. In relation to the construction of a low/intermediate level radioactive waste surface-disposal facility, this study compared and analyzed van Genuchten parameters (α, n) in the laboratory and the hydraulic conductivity obtained in field tests for fractured hornfels at a radioactive-waste disposal site of Korea. The relationship between the field hydraulic conductivity and van Genuchten parameters using data from the ten depth intervals of three boreholes resulted in that the correlation coefficient (R) between the hydraulic conductivity and the van Genuchten parameter α was 0.7607, showing positive correlation whereas the R between the hydraulic conductivity and the van Genuchten shape-defining parameter n was -0.8720, showing negative correlation. Hence, this study confirmed the relationship between the field hydraulic conductivity and the van Genuchten unsaturated functions for the unsaturated fractured hornfels.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.242-251
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• 2013

Recently, while global concern over offshore resources exploration and development is being increased rapidly, offshore plant industry is highlighted as an industry of high added value. Along with this global trend, domestic concern over offshore plant development is being increased as well. In the overseas case, a marine geotechnical survey guideline for confirming characteristics of seabed sediments is available at the time of installation of offshore plant but such guideline is not available in our country. In this study, survey techniques fit for domestic marine environment was applied according to overseas guideline at southern coastal area, Korea. Among the marine geophysical survey techniques being proposed abroad, magnetic survey and seabed photograph were excluded. However, highly reliable data analysis was enabled for marine geophysical survey, which includes in-situ coring investigation and laboratory soil test. In addition, continuous ocean current survey was included to find scour potential due to the current around the offshore plant. Although coring depth is not so deep, we predicted geological structure through the analysis of amplitude features of seismic data. Characteristics of seabed sediments cold be obtained regionally and directly through combined analysis of marine geophysical survey data and coring data.

• The Journal of Engineering Geology
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• v.12 no.2
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• pp.137-150
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• 2002

Recently, plane failure mode occurred frequently along the bedding plane having low angle dip about 20 degree when cutting slopes were constructed in sedimentary rock region of the Gyeongsang Basin. Landslide of the Whangryeong Mountain which was occurred at Busan Metropolitan City in 1999 belongs to the category mentioned above. Reconstruction for cutting slope of the Whangryeong Mountain has finished in 2000 and final grade of reconstructed cutting slope is 1:2.0. To analyze slope failure mode for landslide of the Whangryeong Mountain, various analyses were performed such as in-situ investigation and test, drilling, laboratory test, aerial photograph interpretation, X-ray diffraction analysis, and slope stability analysis using Stereographic Projection and Limit Equilibrium methods. As the result, it is identified that tension cracks had been developed one year before the landslide took place. The tension crack semis to be formed by merging several joint sets. It appears that failure blocks broke down along the sliding planes of different layers. Risk of plane failure is conformed as a result of stability analysis using Stereographic Projection and Limit Equilibrium methods in case that greenish gray tuffaceous shales, regared as sliding planes, are weathered. From now on, a detailed investigation is needed for the thin layers which is sensitive to weathering, and stability analysis for this layer is performed at cut slope construction site having similar geological condition.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.3
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• pp.37-42
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• 2022

Recently, the semiconductor package structures are becoming thinner and more complex. As the thickness decrease, interfacial delamination due to material mismatch can be further maximized, so the reliability of interface is a critical issue in industry field. Especially, the polymers, which are widely used in semiconductor packaging, are significantly affected by the temperature and moisture. Therefore, in this study, the delamination prediction at the interface of package structure was performed through finite element analysis considering the moisture absorption and desorption under the various temperature conditions. The material properties such as diffusivity and saturated moisture content were obtained from moisture absorption test. The hygro-swelling coefficients of each material were analyzed through TMA and TGA after the moisture absorption. The micro-shear test was conducted to evaluate the adhesion strength of each interface at various temperatures considering the moisture effect. The finite element analysis of interfacial delamination was performed that considers both deformation due to temperature and moisture absorption. Consequently, the interfacial delamination was successfully predicted in consideration of the in-situ moisture desorption and temperature behavior during the reflow process.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.17-30
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• 2009

Underground construction such as tunneling can induce damages on the surrounding rock mass, due to the stress concentration of in situ stresses and excessive energy input during construction sequence, such as blasting. The developed damage on the rock mass can have substantial influence on the mechanical and hydraulic behaviors of the rock masses around a tunnel. In this study, investigation on the generation of damage around an opening in a jointed rock model under biaxial compression condition was conducted. The joint dip angles employed are 30, 45, and 60 degrees to the horizontal, and the synthetic rock mass was made using early strength cement and water. From the biaxial compression test, initiation and propagation of tensile cracks at norm to the joint angle were found. The propagated tensile cracks eventually developed rock blocks, which were dislodged from the rock mass. Furthermore, the propagation process of the tensile cracks varies with joint angle: lower joint angle model shows more stable and progressive tensile crack propagation. The development of the tensile crack can be explained under the hypothesis that the rock segment encompassed by the joint set is subjected to the developing moment, which can be induced by the geometric irregularity around the opening in the rock model. The experiment results were simulated by using discrete element method PFC 2D. From the simulation, as has been observed from the test, a rock mass with lower joint angle produces wider damage region and rock block by tensile cracks. In addition, a rock model with lower joint angle shows progressive tensile cracks generation around the opening from the investigation of the interacted tensile cracks.

• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.27-39
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• 2012

This research is to propose the reinforcing method and design code for the lateral behaviors of the abutment displacement induced from the rainfall infiltration on high landfill slope. First, to make the proper numerical analysis, in-situ soil (weathered granite soil) was taken, and the variance of strength parameters according to water content variance was examined by undrained direct shear test, furthermore, other soil parameters were calculated from the standard penetration test such as elastic modulus and Poisson's ratio etc,. Those parameters were used to calculate the lateral behavior of abutment by finite element method and the member force of pile in high landfill slope according to rainfall infiltration . From the results, the shoe displacement on abutment was calculated as 8.98cm, which is 3 times bigger than the allowable displacement, 3cm. To reinforce it, several reinforcing methods were selected and analyzed such as reinforced retaining wall, soil surcharge, pile reinforcing (5m enlargement, 3-line arrangement, 5m enlargement and 3-line arrangement). In case of 5m enlarged and 3-line arrangement piles, the lateral behavior of shoe showed lower value(2.26 cm) than allowable displacement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.779-788
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• 2019

The compaction grouting method is one of the conventional ground improvement methods, which consolidates and compacts the surrounding ground through the injection of grout materials with low mobility. Injecting the grout into the ground can improve the soil properties, as well as form a composite of soil-grout columns. However, the conventional grout pumping is not applicable to handle multiple injection holes at the same time, which may diminish its constructability when the construction time is not enough. This paper proposes a simultaneous multiple compaction-grouting method using a new pump system developed to cover up simultaneously three injection holes at a time. Field injection tests with a single injection hole and with triangular arrangement of injection holes were conducted to evaluate the applicability of the proposed method to soft clay ground. In addition, a series of standard penetration tests (SPTs) were performed to assess the efficiency of each arrangement in improving the soft ground. It is noted from the in-situ test results that the interval distances between injection holes and the elapse time for ground stabilization are the crucial factors governing the applicability of the simultaneous multiple compaction-grouting method to improve the soft clay ground.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.129-137
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• 2007

It is very urgent to research the proper recycling method of marine dredged soil as construction material for environmental conservation. Couple of developed countries have been lots of related researches on recycling of marine dredged soil for marine environmental conservation. This is highly imperative in our country. A small-scaled model test for underground pipe has been conducted on the use of controlled low strength materials with marine dredged soil. The flexible pipe, which is called PVC, was used. Four different testing materials, such as natural sand, insitu-soil, sand-CLSM with marine dredged soil and insitu-soil CLSM with marine dredged soil, were used. The vertical and lateral displacement of pipe with CLSM is one tenth of common granular materials. Also, the use of CSLM showed lower lateral and vertical pressure than that of common granular materials. The main reason is the effect of cement hardening of CLSM. This could increase of the stiffness of pipe with backfill materials. In this study, the data presented show that marine dredged soil and in-situ soil can be successfully used in CLSM and reduce the deformation and earth pressure on flexible pipe.

• Journal of the Korean Geotechnical Society
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• v.27 no.6
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• pp.17-26
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• 2011

Ground anchor method is one of the most popular reinforcing technology in Korea. For the sound monitoring of slope reinforced by permanent anchor for a long period, monitoring the tension force of ground anchor is very important. However, special technology except conventional load cell has not been developed for this purpose. In this paper, a new method is described to replace the conventional strain gauge and V.W. type load cell which has been commonly used as a prestress force monitoring tool for a short-term and long-term. Four 11.5 m long strain detectable tension type anchors were made using FBG sensor embedded tendon since FBG sensor is smaller than strain gauge type load cell and does not have noise from electromagnetic wave. Each two set strain detectable tension type anchors were installed into the different ground conditions, i.e., soft rock and weathered granite soil. Prestress force of ground anchor was monitored during the loading-unloading step from in-situ pullout test using proposed FBG sensor embedded in the tendon and the conventional load cell Test results show that the prestress force monitored from FBG sensor may well be used practically, for it almost matches with that measured from expensive load cell.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.32-39
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• 2021

Recently, necessities of steel form for reinforced concrete beam and girder have been emphasized in building structures for the reduction of the construction period and the labor cost. SY Beam was developed for the these purposes and is roll-formed using thin steel plate. On this research, we tried to evaluate and verify the performance and behavior of SY Beam under construction loading stage as like pouring in situ concrete. For the standard shape of SY beam, structural modelling with various steel thicknesses has carried out using MIDAS GEN program. From results of modelling, the width and height of SY Beam were determined 600mm and 400mm respectively. For 3 SY Beams, the loading experiment was performed to measure vertical and horizontal displacement under stacking sand, concrete block, and bundle of rebar. As a result, the vertical deflection showed a tendency to decrease as the thickness increased. In the horizontal displacement, the trend according to the thickness was not clearly observed. From the evaluation on the loading experiment, it is considered that the SY Beam can secure both workability and structural safety. In particular, the SY Beam(1.2mm) hardly generates horizontal displacement, so it has excellent load-bearing capacity. So, we judged that the SY Beam with 1.2mm steel plate has excellent performance and consider to be immediately commercially available.