• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.445-454
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• 2006

Myungji Housing Complex is located in the Nakdong River plain in which the Busan soft clays are developed. It has thick soft soil laver of about GL(-)50m including loose sandy layers, upper and lower clayey layers. The clayey layers have been being consolidated since the land reclamation was completed to build the place for Housing Complex(Apartment) in 1997. Therefore, as one of a series of advance preparations of this project, study was carried on the geotechnical characteristics under the foundation The first part of this paper represents a brief geological history. Then, geotechnical characteristics of clay was analyzed in the classical developments in soft clay. They were based on the geotechnical data obtained by site investigations performed from 1992 to 2005. Finally, we evaluated the average degree of consolidation at this point in time and the residual settlements of upper clayey layer using dissipation and oedometer tests for this project

• Geomechanics and Engineering
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• v.30 no.5
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• pp.437-448
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• 2022

Alluvial soil is challenging to work with due to its high compressibility. Thus, consolidation settlement of this type of soil should be accurately estimated. Accurate estimation of the consolidation settlement of alluvial soil requires accurate prediction of compressibility parameters. Geotechnical engineers usually use empirical correlations to estimate these compressibility parameters. However, no attempts have been made to develop correlations to estimate compressibility parameters of alluvial soil. Thus, this paper aims to develop new models to predict the compression and recompression indices (Cc and Cr) of alluvial soils. As part of the study, geotechnical laboratory tests have been conducted on large number of undisturbed samples of local alluvial soil. The obtained results from these tests in addition to available results from the literature from different parts in the world have been compiled to form the database of this study. This database is then employed to examine the accuracy of the available empirical correlations of the compressibility parameters and to develop the new models to estimate the compressibility parameters using the nonlinear regression analysis. The accuracy of the new models has been accessed using mean absolute error, root mean square error, mean, percentage of predictions with error range of ±20%, percentage of predictions with error range of ±30%, and coefficient of determination. It was found that the new models outperform the available correlations. Thus, these models can be used by geotechnical engineers with more confidence to predict Cc and Cr.

• Geomechanics and Engineering
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• v.28 no.2
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• pp.157-169
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• 2022

Preloading of soft clays is a common ground stabilization method for improvement of compressibility and the undrained shear strength. The waiting period under preload is a primary design criterion controlling the degree of improvement obtained. Upon unloading the overconsolidation attained with respect to actual loads defines the long term performance. This paper presents a laboratory study for investigation of creep behavior of Famagusta Bay alluvial soft soil preloaded under various effective stresses for analysis of long term performance based on the degree of overconsolidation. Traditional one-dimensional consolidation tests as well as modified creep tests are performed on reconstituted soft specimens. Compressibility parameters are precisely backcalculated using one dimensional consolidation theory and the coefficient of creep is determined using the traditional Cassagrande method as well as two modified methods based on log cycles of time and the inflection of the creep curve. The test results indicated that the long term creep can be successfully predicted considering the proposed method. The creep coefficients derived as part of this method can also be related to the recompression index (recompression index, swelling index) considering the results of the testing method adopted in this study.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.215-218
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• 2005

This study was carried out to find problems of the farmland according to the large scale land consolidation projects. Field ramp have problems such as steep slope, narrow width and the difficulty of entering into field and exiting from it. In case of the even ratio of the paddy plot, It showed that the difference of the maximum average level were 8.4cm for the general plots($0.3{\sim}0.4ha$), 12.6cm for the large scale plots($0.8{\sim}1.0ha$), and the level of outlet part was higher than the level of inlet part in some plots. Also, most of presently using inlets are closed and opened manually. It showed that farmers had difficult in the operating of the inlets or the outlets. So it is required the development of the suitable inlets and the suitable outlets.

• Journal of Korean Medical classics
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• v.12 no.1
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• pp.113-138
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• 1999

Distension of hydrops is the pathosis that the hydration is retented in abdomen and that is caused by disturbance of hydrometabolism. Most of hydrops belongs to Consolidation. In part of OhRyungJinAek-Byeul of Youngchu"靈樞 五癃津液別", the general explanation of hydrops is briefed. But there was nothing about pathogenesis, pathology, symptoms and the method of treatment. The part SuChang of Youngchu "靈樞 水脹" divided it by Superficial-swelling, Hidden-swelling, Ovarian-hydrops, Stony-uterin-mass and explained it to cure by Category of pathology. So, the books JeByeongWonHuRon"諸病源候論" ChonGeumYoBang"千金要方", WoiDaeBiYo"外臺秘要", TaePyeungSeongHyeBang"太平聖惠方", BoJeBang"普濟方", EuiHakGangMok"醫學綱目", DongEuiBoGam"東醫寶鑑" etc. published later, show the method of treatments and medications with quotation the original text of this part. And it is convinced that more profound research of this part is inevitable to understand the correct meaning of hydrops that explained by many of ancient medical scholars, and to apply it to clinical medicine. There is an explanation on Distension hydrops in the prologue of this part. And t six kinds of disease in this part is simila to edema, so it is called SuChang"水脹", pathology of Edema. Superficial-swellin Hidden-Swelling is reported in the fir chapter, differential diagnosis of Ovarian-hydrops, Stony-uterin-mass is rep in the second chapter, and treatment Superficial swelling. Hidden Swelling reported in the third chapter. Briefly looking over that chapter, Distension of hydrops is recognized as stay of hydration at the abdomen as a result of disturbance of hydrometabolism and it says about symtoms, pathogenesis, pathology, differential diagnosis, treatment of Hydrops Superficial-swelling Hidden-swelling Ovarian-hydrops Stony-uterinmass. And it says about a few things that Superficial-swelling, Hidden-swelling could be differentiated by colors of skin and distension of abdomen, and Ovarian-hydrops, Stony-ulerin-mass could be differentiated that it occurs which sex and whether mensturation occurs or not, and treatment of Superficial-swelling, Hidden-swelling, Ovarian-hydrops.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1542-1549
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• 2009

The function of subgrade in the railway is to support track load on the subgrade as well as train load. Unlike the traditional railway, the uppermost subgrade layer in the Gyeongbu high speed railway was constructed as the reinforced road bed. The reinforced road bed comprises sub-ballast in the upper part and grade ballast in the lower part. The filling material such as soil and rocks in the subgrade can be settled by consolidation of original ground, compression due to self weight, plastic displacement due to train operation, and unequal settlement due to embankment material or improper compaction, therefore many efforts have been given for sufficient compaction and use of proper filling materials in the construction stage. The purpose of this study is to investigate the deformation state of subgrade in the Gyeongbu high speed railway. The investigation on the subgrade settlement was performed by choosing representative sections suspected to be settled based on the previous GPR test results and track maintenance history, measuring the settlement for some time period after installing settlement measuring instruments on and under the reinforced road bed. and analyzing the long-term subgrade settlement data from monitoring system which was installed at the construction stage of the high speed railway.

• Composites Research
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• v.29 no.5
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• pp.315-320
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• 2016

Conventionally, composite aircraft structures are fabricated within autoclave at high pressure. However, autoclave process has several disadvantages including high curing costs and limitation of part size. Recently, out-of-autoclave (OoA) processes have been investigated in many studies to replace conventional autoclave process. A newly developed OoA prepreg, using conventional ovens, can significantly reduce the curing costs and produce autoclave-quality parts. Nevertheless, manufacture of void-free complex shape structure using OoA process presents significant challenges because of the low consolidation pressure. In this study, integrated skin-spar-rib composite part was fabricated using OoA prepreg. And cross-sectional macro- and micro-graphs of the part were examined in order to assess the possibility of replacing conventional autoclave process.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.981-984
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• 2008

The super tall building above 100 floors is required that each floor's height is more than 4 meters, and each core wall's thickness is more than 60cm. Therefore, for the successive accomplishment of super tall building, the full scale mock-up test was required. The test results are as follows; Real strength of core wall was satisfied with design strength at 28 days regardless of types of strength, and according to the consolidation effect, lower part's strength was a little higher than upper part's strength. Lateral force of HSC was evaluated with max. $4.5ton/m^2$, and hydration temperature of mock-up test was evaluated that maximun heat of central part revealed about $80^{\circ}C$ at 70MPa and $65^{\circ}C$ at 50MPa, and, the difference between inner and outter part revealed about $30^{\circ}C$ at 70MPa and $12^{\circ}C$ at 50MPa. Also, no crack by hydration temperature was not shown on the surface.

• Geomechanics and Engineering
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• v.36 no.3
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• pp.259-276
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• 2024

The undrained shear strength is widely acknowledged as a fundamental mechanical property of soil and is considered a critical engineering parameter. In recent years, researchers have employed various methodologies to evaluate the shear strength of soil under undrained conditions. These methods encompass both numerical analyses and empirical techniques, such as the cone penetration test (CPT), to gain insights into the properties and behavior of soil. However, several of these methods rely on correlation assumptions, which can lead to inconsistent accuracy and precision. The study involved the development of innovative methods using extreme gradient boosting (XGB) to predict the pile set-up component "A" based on two distinct data sets. The first data set includes average modified cone point bearing capacity (q_t), average wall friction (f_s), and effective vertical stress (σ_vo), while the second data set comprises plasticity index (PI), soil undrained shear cohesion (S_u), and the over consolidation ratio (OCR). These data sets were utilized to develop XGBoost-based methods for predicting the pile set-up component "A". To optimize the internal hyperparameters of the XGBoost model, four optimization algorithms were employed: Particle Swarm Optimization (PSO), Social Spider Optimization (SSO), Arithmetic Optimization Algorithm (AOA), and Sine Cosine Optimization Algorithm (SCOA). The results from the first data set indicate that the XGBoost model optimized using the Arithmetic Optimization Algorithm (XGB - AOA) achieved the highest accuracy, with R2 values of 0.9962 for the training part and 0.9807 for the testing part. The performance of the developed models was further evaluated using the RMSE, MAE, and VAF indices. The results revealed that the XGBoost model optimized using XGBoost - AOA outperformed other models in terms of accuracy, with RMSE, MAE, and VAF values of 0.0078, 0.0015, and 99.6189 for the training part and 0.0141, 0.0112, and 98.0394 for the testing part, respectively. These findings suggest that XGBoost - AOA is the most accurate model for predicting the pile set-up component.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.1
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• pp.102-111
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• 1997

Experiments both in laboratory and field were performed to compare and analyze the characteristics of alluvial clay. The alluvial clay was sampled in test site in which large-scaled tests for the part of the site are under process to suggest the rational method for alluvial clay and the criterion for ground settlement monitoring system. The followings were observed through the experiments : 1. Natural water content, plastic limit, and liquid limit of alluvial clay composed of highly fine grains were 40~80%, 10~20%, and 30~55%, respectively. The values of these properties were relatively small at the ground surface, while the values showed maximum at G.L.- l0m and gradually decreased below the level. 2. Shear strength of alluvial clay was proportionally increased to the depth. Unconfined and triaxial compressive strengths were 0.2~0.6kgf/$cm^2$ and 0.1~0.3kgf/$cm^2$, respectively. 3. Compression index and secondary compression index showed maximum values at G.L.-l0m and gradually decreased below the level. The value of consolidation coefficient was relatively large at the ground surface, constant with decreasing the depth, and incresed when G.L. was below -20m. 4. Piezocone test appeared that alluvial clay with N value of 2~4 was uniformly distributed with 20~ 30m thickness from the ground surface, sand seam was nonuniformly distributed, and penetration pore pressure was 0.8 ~ 1 times of the hydrostatic pressure. Undrained shear strength and consolidation coefficient were 0.04 ~ 0.76kgf / $cm^2$ and $2.88{\times} 10{^-4}~1.3{\times} 10{^-2} cm^2/s$ respectively.