• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3596-3601
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• 2015

Enhancement of the existing program for analyzing a pile driven by vibro hammer was tried. Damping effect of dynamic soil resistance and clutch friction were added to the existing governing equation which constitute vibrating system of vibro hammer-pile-soil. Parameters of the modified Ramberg-Osgood model which simulates dynamic load transfer curves for the developed program were recomputed. Comparing the results of the modified program with those of the field tests, pile displacement with time and load transfer behavior were more similar to those of the field test. The penetration rates obtained from the modified program were more close to those of the field test rather than those of the commertical program.

• Journal of the Korean Wood Science and Technology
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• v.47 no.6
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• pp.667-673
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• 2019

The performance of a wooden deck made of refractory materials that have difficulties in achieving target penetrations as stipulated in the specification and quality standards for treated wood in Korea, was assessed via a case study in this research. A wooden deck built in Jinju in 2009 was selected for this study because of its fabrication method using pressure and treated refractory materials. The penetration and retention analysis did not satisfy the domestic standard for treated wood. Inspection of the deck in 2019 revealed that the deck had been attacked by decay fungi. Cap rails showed much deeper and wider checking on their surface compared with the top and base rails, resulting in a severe fungal attack. The decking boards exhibited severe fungal decay primarily in the end parts. However, the rails and balusters without checks and posts were virtually free of fungal attack irrespective of the preservative penetration measures. Copper content in the soil 5 cm away from the deck was less than 150 mg/kg, implying that copper movement in the soil was very limited. These results suggest that the inhibition of surface propagation and the protection of end surfaces are essential factors in increasing the longevity of treated wooden decks; further, the results also showed that the deck was within an acceptable range from the point of copper contamination.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.147-154
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• 2008

Weathered soil slope loses its shear strength if it is exposed in the air for a long time or in contact with water. And this kind of strength loss is remarkable in dam slope which has very big difference in water level according to the season. In this study, shear strength loss of weathered soil due to saturation had been found out through dryness and wetness repetition direct shear test. Also relation between penetration blow number(Nc) and shear strength parameter had been found out through small sized dynamic cone penetration test device and the correlation equation of Nc had been proposed through artificial neural network analysis to estimate shear strength parameter easily.

• Journal of the Korean Geosynthetics Society
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• v.21 no.2
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• pp.31-38
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• 2022

Recently, irregular torrential rainfall have frequently occurred due to abnormal climate, and landslide damage is increasing. In Korea, more than 70% of the total land is mountainous areas, appropriate measures are needed to prevent landslides by heavy rainfall. When improved soil is applied to the surface of the slope, it is possible to suppress an increase in groundwater level due to rainfall penetration and secure stability of the slope. In this study, the appropriate depth of improved soil that can confirm the increase in groundwater level and secure stability by applying improved soil to the weathered soil slope was studied. A total of three cases were analyzed for the slope of the cross-section: standard slope for weathered soil (1:1.5, 1:1.8, and 1:2.0). For rainfall conditions, referring to the regional frequency probability rainfall provided by the Water resource Management Information System, the increase in groundwater level by stage was confirmed by assuming a 500-year frequency precipitation maximum duration of 48 hours. As a result of the study, in the case of natural slopes, the slope was completely saturated before 48 hours the rainfall duration, and there was a possibility of collapse. the improvement depth in the slope of 1:1.5 was appropriate for more than 1m from the surface regardless of the rainfall duration, and in the the slope of 1:1.8 was appropriate of 1m for more than 36 hours. in the slope of 1:2.0, it was appropriate for that safety when improved soil of 0.5m for rainfall duration 48 hours or more.

• Ocean Systems Engineering
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• v.7 no.2
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• pp.107-120
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• 2017

Spud-can is used for fixing jack-up rig on seabed. It needs to be inserted up to the required depth during the installation process to secure enough soil reaction and prevent overturning accidents. On the other hand, it should be extracted from seabed soils as fast as possible during the extraction process to minimize the corresponding operational cost. To achieve such goals, spud-can may be equipped with water-jetting system including monitoring and control. To develop such a smart spud-can, a reliable numerical simulation tool is essential and it has also to be validated against physical model tests. In this regard, authors developed a numerical simulation tool by using a commercial program ANSYS with extended Drucker-Prager (EDP) formula. Authors also conducted small-scale (1/100) physical model tests for verification and calibration purpose. By using the numerical model, a systematic parametric study is conducted both for sand and K(kaolin)-clay with varying important soil parameters and the best estimated soil properties of the physical test are deduced. Then, by using the selected soil properties, the numerical and experimental results for a sand/K-clay multi-layer case are cross-checked to show reasonably good agreement. The validated numerical model will be useful in the next-stage study which includes controllable water-jetting.

• Geomechanics and Engineering
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• v.37 no.3
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• pp.253-262
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• 2024

Dynamic properties are pivotal in soil analysis, yet their experimental determination is hampered by complex methodologies and the need for costly equipment. This study aims to predict dynamic soil properties using static properties that are relatively easier to obtain, employing machine learning techniques. The static properties considered include soil cohesion, friction angle, water content, specific gravity, and compressional strength. In contrast, the dynamic properties of interest are the velocities of compressional and shear waves. Data for this study are sourced from 26 boreholes, as detailed in a geotechnical investigation report database, comprising a total of 130 data points. An importance analysis, grounded in the random forest algorithm, is conducted to evaluate the significance of each dynamic property. This analysis informs the prediction of dynamic properties, prioritizing those static properties identified as most influential. The efficacy of these predictions is quantified using the coefficient of determination, which indicated exceptionally high reliability, with values reaching 0.99 in both training and testing phases when all input properties are considered. The conventional method is used for predicting dynamic properties through Standard Penetration Test (SPT) and compared the outcomes with this technique. The error ratio has decreased by approximately 0.95, thereby validating its reliability. This research marks a significant advancement in the indirect estimation of the relationship between static and dynamic soil properties through the application of machine learning techniques.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.792-801
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• 2016

Standard Penetration Test (SPT) and Cone Penetration Test (CPT) are widely used in geotechnical investigation methods for railway roadbed. However, SPT can not be used on the Railway track, since the equipment may contact to the electric lines. However, a portable equipment can be used for geotechnical investigation without electrical hazard. Dynamic Cone Penetrometer (DCP) is one of representative portable equipments. A normal portable DCP has usually not enough driving energy and the rigidity of cone-rod, so it is impossible to investigate the required investigate penetration depth. In this study, The adaptability of Pagani cone test which is one of portable dynamic cone penetrometer is studied and compared with SPT-N data. As a result of this study, the proposed correlation factors between Pagani cone test and SPT-N values after corrections is 1.48 for sandy soil and 1.33 for clayey soil.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.3
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• pp.155-159
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• 2004

This experiment was carried out to evaluate the microclimate of wheat canopy, growth and yield characteristics of wheat under north-south and east-west row orientation. The variety used in this experiment was "AG South 2000", which was developed in USA. Solar radiation, air temperature, relative humidity, and soil temperature were monitored by data logger from March to May in 2002, The ratio of light penetration to the bottom from the upper canopy was 36.8% in north-south and 21.4% in east-west row orientation. Temporal march of light penetration to the bottom from March to May decreased as wheat developed canopy structure and decreased a little from May as plant were matured. The highest light penetration to the bottom from upper canopy occurred at 13：00 in both north-south and east-west row orientations, respectively which were 36 times in north-south and 27 times in east-west row orientation, respectively. Daily maximum temperature at the bottom of canopy occurred at 14：00 with 29 times in north-south, while 19 times were obtained at 14：00 and 15：00, respectively in east-west row orientation. Relative humidity at the bottom of the canopy in east-west yow orientation showed higher than that of north-south row orientation. Occurrence of daily maximum soil temperature of north-south showed one hour later compared with east-west yow orientation. 1000 grain weight and test weight of north-south row orientation was higher than those of east-west vow orientation. Correlation coefficient between solar radiation of upper canopy and 1000 grain weight showed r=$0.8132^{*}$, and between air temperature of upper canopy and number of spikes per $\textrm{m}^{2}$ and 1000 grain weight showed significant positive correlation with r=$0.8139^{*}$, and r=$0.8293^{*}$, respectively.

• Journal of the Korean Geotechnical Society
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• v.31 no.8
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• pp.29-38
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• 2015

This paper presents the application of the Coupled Eulerian-Lagrangian (CEL) numerical technique to simulate the driving of open-ended piles into sandy soil. The main objective of this study was to investigate the applicability of CEL technique to the behavior of the driven pile penetration. Comprehensive studies to verify the behavior of driven pile penetration are presented in this paper. Through comparison with results of field load tests, the CEL methodology was found to be in good agreement with the general trend observed by in situ measurement, and the CEL approach accurately simulated the behavior of driven pipe piles.

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.53-66
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• 2022

The national ground survey database (GeoInfo) distributes numerous ground survey data nationwide. Many standard penetration test results exist in this database; however, the number of shear wave velocity (V_S) data is small. Hence, to use abundant standard penetration test-N values to predict V_S, this study proposed a new empirical N-V_S relationship model using GeoInfo data. The proposed N-V_S model is a single equation regardless of geological layer types; the layer type only specifies the upper limit of V_S. To validate the proposed model, residual analysis was performed using a test dataset that was not used for the model development. Therefore, this study's proposed model performed better than N-V_S models from previous studies. Since the N-V_S model in this study was developed using sufficient data from GeoInfo, we expect that it is the most applicable to GeoInfo dataset for V_S prediction.