• Journal of the Korean Geotechnical Society
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• v.39 no.1
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• pp.27-38
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• 2023

In this study, the impact of pile tip geometry, including shape, size, and angle, on the drivability and stress concentration during pile driving was investigated using 3D printing technology and finite element numerical analysis. A series of field loading tests were conducted on a test pile with various pile tip conditions, including width, angle, and shape. The changes in settlement were quantified as a ratio to the settlement of a conventional pile tip case and large deformation finite element analysis was used to investigate the maximum stress on a pile tip and the location of possible damage during pile driving. The results showed that by modifying the shape, size, and angle of the pile tip, the drivability of the pile could be improved and the maximum stress concentration around the pile tip could be significantly reduced, thereby ensuring the structural integrity of the pile during pile driving.

• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.5-13
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• 2015

For the bearing capacity evaluation, dynamic pile tests instead of static pile tests have been commonly used in embedded piles, which are known to have low noise and low vibration construction method. The objective of this study is to analyze the bearing capacity and penetration behaviors of embedded piles, which are constructed in different ground conditions, by using force and velocity signals obtained in the final blows during construction of embedded piles. For the dynamic pile analyses, the CAse Pile Wave Analysis Program (CAPWAP) and Wave Equation Analysis of Piles (WEAP) have been commonly used. In this study, the CAPWAP and WEAP are used for the analyses of the dynamic pile tests, which are conducted on embedded piles. The input values, output values, and force-velocity graphs of CAPWAP determined by analyzing the measured force-velocity signals are investigated. In addition, similar force-velocity singals are obtained from the WEAP by analyzing the input values of the WEAP. Considering the subsurface investigation results around the pile tips, if the N-value increases exponentially along the depth, toe quake value should be small, and therefore large bearing capacity is identified. On the contrary, if the N-value increases linearly, the bearing capacity is small because of large toe quake value. Furthermore, the stiffness of hammer cushion and pile cushion, which is difficult to find correct values, is recommended lower than 500 kN/mm. This study demonstrates that the results of WEAP may be similar to those of CAPWAP and the WEAP can be used to estimate the bearing capacity of embedded piles.

• Journal of the Korean Geotechnical Society
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• v.30 no.10
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• pp.33-44
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• 2014

The preliminary design of suction pile as the supporting system for concrete floating structures was performed for the pilot project of the southwest coast area in Korea. Prior to starting design work, site conditions of the area including ground and hydraulic conditions, and a 100-year return period external force were throughly evaluated. The suction pile for mooring of the offshore floating structures has to satisfy the lateral resistance against external force as well as the penetration ability according to the soil conditions such as soil types, shear strengths, effective stresses, and seepage forces. In the design, the required penetration depths, which were stable for lateral resistance, were evaluated with the diameters of cylindrical suction pile as the final installing ones. And the design suction pressures at each penetrating depths, at which sand boiling did not occur, were assessed through the comparison of penetration and penetrationresistance forces. As a result, it was impossible for suction piles with the diameter range of 3.0~5.0 m to penetrate into required penetration depths. On the other hand, suction piles with the diameter range of 6.0 m and 7.0 m satisfied both the horizontal stability and the penetration ability by design suction pressures at the required penetration depths of 8.5 m and 8.0 m, respectively.

• The Journal of the Petrological Society of Korea
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• v.9 no.3
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• pp.121-141
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• 2000

Granitic and pophyroblastic gneisses are widely distributed in the Seungju-Suncheon area, the southwestern part of the Sobacksan Massif. Two groups of metamorphic P-T conditions are recognized from granitic gneiss. $622-760^{\circ}C/6.2~7.4\;kbar$(Group I) are estimated from garnet cores and samples with weak retrograde metamorphism. $606~785^{\circ}C/3.7~5.4\;kbar$(Group II) are estimated from garnet rims which have lower pyrope and higher spessartine contents due to the effect of retrograde metamorphism. The metamorphic P-T conditions estimated from porphyroblastic gneiss are $489~669^{\circ}C$, 2.1~4.8 kbar which are similar to the P-T conditions of Group II in the granitic gneiss. The whole rock-garnet Sm/Nd isotopic ages determined from granitic and porphyroblastic gneisses are, respectively, $1417{\pm}52\;Ma\;and\;1421{\pm}14\;Ma$. These date indicate that intermediate-P/T type metamorphism represented by Group I may have occurred between the intrusion of granite gneiss and the intrusion of porphyroblastic gneiss(between 1890 Ma~2120 Ma) and two gneisses experienced low-P/T type metamorphism after the intrusion of porphyroblastic gneiss at 1417~1421 Ma.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.141-152
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• 2022

As interest increases related to the development of eco-friendly energy, the offshore wind turbine market is growing at an increasing rate every year. In line with this, the demand for an installation vessel with large scaled capacity is also increasing rapidly. The wind turbine installation vessel (WTIV) is a fixed penetration of the spudcan in the sea-bed to install the wind turbine. At this time, a review of the spudcan is an important issue regarding structural safety in the entire structure system. In the study, we analyzed the current procedure suggested by classification of societies and new procedures reflect the new loading scenarios based on reasonable operating conditions; which is also verified through FE-analysis. The current procedure shows that the maximum stress is less than the allowable criteria because it does not consider the effect of the sea-bed slope, the leg bending moment, and the spudcan shape. However, results of some load conditions as defined by the new procedure confirm that it is necessary to reinforce the structure to required levels under actual pre-load conditions. Therefore, the new procedure considers additional actual operating conditions and the possible problems were verified through detailed FE-analysis.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.59-70
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• 2010

More than 10 different cases of airline overrun accidents happened annually home and abroad in recent years. So the government put the guidelines to protect that kinds of accidents, which is named 'Runway End Safety Area'. However, the great part of airports are far from the standards, because most of the airports have been built before the guidelines. Moreover, in many cases natural obstacles, ambiance, and local area developments obstruct the extension of the runway to meet the criteria. For these reasons, the Federal Aviation Administration (FAA) recommends that the aviation fields construct 'Aircraft Rapid Arresting System(ARAS)' at the end of the runway. Many airdromes have been constructing the system and some airports have already completed the construction. In this research, our team performed a basic study about low strength perlite concrete to provide the proper material with 'ARAS'. As a result, the unit weight of the low strength perlite concrete was $4.5{\sim}6.4kN/m^3$ and uniaxial compressive strength was measured in the range of $400{\sim}1,470kN/m^2$. In addition, we tested penetration compressive strength by using CBR tester, and we observed that the strength was increased after around 60% of penetration rate. Also, 40% of penetration rate was measured through the penetration test with dump trucks.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.201-207
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• 2006

Soil tests are generally conducted using a membrane to measure a pore water pressure. However, it has also been recognized that the membrane penetrates into the specimen by the change of the confining pressure, and it results in the erroneous measurement in the pore water pressure and the volumetric strain. This study examined the effectiveness of the correction equation of the membrane penetration on the basis of the experimental data acquired during the isotropic unloading and the cyclic shear process using the hollow cylindrical shear test equipment. The results showed that the membrane penetration by the correction equation could be overestimated when the mean effective stress was lower than 20kPa in this study. The limitations originated from the sudden increase near the zero effective stress, and in order to prevent the overestimation in low effective stress condition, the use of the constant a was proposed in this study. Furthermore, the correction equation for the membrane penetration had to be applied carefully when the initial relative density was high and the density changes were occurred by the relocation of the soil particle by the liquefaction.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.3
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• pp.123-127
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• 2013

In this study, the buckling behaviors during the installation of a bucket foundation for an offshore wind turbine tower were investigated. The objective structure was modeled by using a commercial structural analysis program, and the buckling behavior of the model was estimated as Batdorf's parameter Z in the design code. The surrounding soil conditions and loading condition were applied to the verified analysis model. The effects of parameters such as the longitudinal stiffeners and driven depth were estimated for the buckling capacity. As a result, it was found that the longitudinal stiffeners could drastically increase the buckling capacity in a specific region. In addition, the buckling capacities increased linearly when considering the effect of the surrounding soil.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1908-1914
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• 2012

As the turbine capacity and the water depth of wind farms are increasing, the construction cost of substructures and foundations for offshore wind turbines is expected to increase. Since the installation of suction bucket foundation is achieved by both self-weight and applied suction, the construction generally does not require heavy equipment for penetration. This study provides an economic analysis on the tripod which have the bucket foundations and compares that the jacket foundation at 50m water depth on sand layer or soft layer. As the strength of the soil and the number of the foundation is increasing, the construction cost of the tripod with the bucket foundations is more economically feasible than the jacket foundation.

• Journal of the Korean Geophysical Society
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• v.7 no.3
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• pp.171-183
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• 2004

Electrical resistivity survey is widely used to investigate the stability of center-core type fill dam against the seepage phenomenon. In this study, we analyze the resistivity information obtained on a earth fill dam and compare it with the geotechnical SPT result. The analysis shows that the zones showing low resistivity value generally have low N value. However, some zones with high resistivity pattern do not accompany the increase of N value, and even showing low N value. These results imply that the direct identification of resistivity value to the real status of the core material of fill dam is impossible, and a highly resistive zone may be in serious status due to the effect increasing the resistivity value by the piping condition. Therefore, multiple exploration should be planned to reduce the uncertainty in application of geophysical methods to dam safety evaluation.