• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.1-11
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• 2017

In this study, 1/6 small-scale model tests of helical piles were conducted to evaluate their installation time and ultimate capacities. Model sand layers were constructed using sand pluviating method to produce uniform soil relative density. For installation of different helical piles varying locations (vertical center-to-center spacings of 50 mm and 150 mm) of helix plates, two different rotation speeds of 15 rpm and 30 rpm were implemented. Cone penetration equipment was installed within the hallow section of the helical pile to increase ultimate capacity of helical pile and to evaluate soil properties of plugged soils and soils below pile tip after installation of the piles. Based on the test results, the most fasted installation was possible under the condition of "rotation speed of 30 rpm and center-to-center spacing of 50 mm", and the highest ultimate capacity was mobilized under the condition of "rotation speed of 30 rpm and center-to-center spacing of 150 mm with cone penetration implementation."

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.631-642
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• 2013

The standard CPT(Cone Penetration Test), which can be easily performed to investigate in-situ soil engineering properties, has been widely used. CPT are also widely being utilized in centrifuge model tests. In this study, a miniature cone with 10mm diameter was developed and its applicability in the centrifuge was evaluated. The developed miniature cone was equipped with a four degree-of-freedom in-flight robot. A series of cone penetration tests was performed under four centrifuge acceleration levels. As results, the cone resistances measured at the same confining stress within shallow penetration depth were affected by the centrifugal accelerations. The critical depth was proportional to the cone diameter and relative density. Cone resistances results below the critical depth and soil parameters obtained from the laboratory tests were compared with those by previously proposed empirical relations.

• Smart Structures and Systems
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• v.17 no.2
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• pp.209-230
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• 2016

The Canton Tower is a high-rise slender structure with a height of 610 m. A structural health monitoring system has been instrumented on the structure, by which data is continuously monitored. This paper presents an investigation on the identified modal properties of the Canton Tower using ambient vibration data collected during a whole day (24 hours). A recently developed Fast Bayesian FFT method is utilized for operational modal analysis on the basis of the measured acceleration data. The approach views modal identification as an inference problem where probability is used as a measure for the relative plausibility of outcomes given a model of the structure and measured data. Focusing on the first several modes, the modal properties of this supertall slender structure are identified on non-overlapping time windows during the whole day under normal wind speed. With the identified modal parameters and the associated posterior uncertainty, the distribution of the modal parameters in the future is predicted and assessed. By defining the modal root-mean-square value in terms of the power spectral density of modal force identified, the identified natural frequencies and damping ratios versus the vibration amplitude are investigated with the associated posterior uncertainty considered. Meanwhile, the correlations between modal parameters and temperature, modal parameters and wind speed are studied. For comparison purpose, the frequency domain decomposition (FDD) method is also utilized to identify the modal parameters. The identified results obtained by the Bayesian method, the FDD method and a finite element model are compared and discussed.

• Geotechnical Engineering
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• v.9 no.4
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• pp.7-16
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• 1993

Calibration chamber tests were conducted on open -ended model piles driven into dried siliceous sands with different soil conditions in order to clarify the effect of soil conditions on plug capacity, The model pile used in the test series was devised so that the bearing capacity of an open -ended pile could be measured out into three components , outside shaft resistance. plug resistance and tip resistance. Under several assumption, the value of earth pressure coefficient in the soil plug is calculated. It is gradually reduced with increase in the longitudinal distance from the pile tip. At the bottom of soil plug, it tends to decrease with increase in the penetration depth and relative density, and to increase with the increase of ambient pressure. In comparison of measured and calculated plug capacities using the one -dimensional analysis, we note that API code and one -dimensional analysis combined with P suggested by Randolph et al. and O'Neill et al. result in great underestimation of the plug capacity. Therefore, based on the test results, an empirical equation was suggested to compute the earth pressured coefficient to be used in the calculation of plug capacity using the one -dimensional analysis. and it produces proper plug capacities for all soil conditions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.6
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• pp.110-117
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• 2011

Seashore landfill projects use undersea pump dredging method for construction of airport and factory site. Coarse grain soil from the dredging is considered for use at inland. West sea shore bottom consists of primarily coarser grained silt-sand and this component contains far more percentage than is the case with East sea and South sea area. This soil shows very different characteristic at consolidation and compaction behavior. This research targets to utilize this type of dredging soil. Test specimen is from West sea (Saemangum) dredged soil landfill site. Model analysis is done for getting prediction of original soil relative density and N-value from dynamic compaction energy variance. Dynamic compaction energy is calculated for efficient foundation design.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.5
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• pp.193-202
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• 2023

In this paper, a dynamic centrifuge model test was conducted on a 24.8-meter-deep excavation consisting of a 20 m sand layer and 4.8 m bedrock, classified as S3 by Korean seismic design code KDS 17 10 00. A braced excavation wall supports the hole. From the results, the mechanism of seismically induced earth pressure was investigated, and their distribution and loading points were analyzed. During earthquake loadings, active seismic earth pressure decreases from the at-rest earth pressure since the backfill laterally expands at the movement of the wall toward the active direction. Yet, the passive seismic earth pressure increases from the at-rest earth pressure since the backfill pushes to the wall and laterally compresses at it, moving toward a passive direction and returning to the initial position. The seismic earth pressure distribution shows a half-diamond distribution in the dense sand and a uniform distribution in loose sand. The loading point of dynamic thrust corresponding with seismic earth pressure is at the center of the soil backfill. The dynamic thrust increased differently depending on the backfill's relative density and input motion type. Still, in general, the dynamic thrust increased rapidly when the maximum horizontal displacement of the wall exceeded 0.05 H%.

• Composites Research
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• v.20 no.4
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• pp.9-17
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• 2007

Powder metallurgy has been employed for the development of SiC particle reinforced aluminum metal matrix composites by means of hot isotropic pressing and vacuum hot pressing. A material model based on micro-mechanical approach then has been presented for the processes. Densification occurs by the inelastic flow of matrix materials during the consolidation, and consequently it depends on many process conditions such as applied pressure, temperature and volume fraction of reinforcement. The model is implemented into finite element software so that the process simulation can be performed enabling the predicted relative density to be compared with experimental data. In order to determine the performance of finished products, further tensile test has been conducted using the developed specimens. The effect of internal void of the materials on mechanical properties therefore can be investigated.

• Geotechnical Engineering
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• v.14 no.3
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• pp.25-46
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• 1998

This paper shows that there are the results of a series of model tests on the behavior of single pipe pile which is subjected to lateral load in, Nak-dong River sand. The purpose of the present paper is to estimate the effect of Non-homogeneity. constraint condition of pile head, lateral load velocity, relative density, and embedded length of pile on the behavior of single pile. These effects can be quantified only by the results of model tests. Also, these are compared with the results of the numerical methods (p-y method, modified Vlasov method; new ${\gamma}$ parameter, Characteristic Load Method'CLM). In this study, a new ${\gamma}$ parameter equation based on the Vlasov method was developed to calculate the modulus of subgrade reaction (E. : nhz.) proportional to the depth. The p-y method of analysis is characterized by nonlinear behavior. and is an effective method of designing deep foundations subjected to lateral loads. The new method, which is called the characteristic load method (CLM). is simpler than p-y analysis. but its results closely approximates p-y analysis results. The method uses dimensional analysis to characterize the nonlinear behavior of laterally loaded piles with respect to be relationships among dimensionless variables. The modulus of subgrade reaction used in p-y analysis and modified Vlasov method obtained from back analysis using direct shear test (DST) results. The coefficients obtained from DST and the modified ones used for the prediction of lateral behavior of ultimate soil reaction range from 0.014 to 0.05. and from 0.2 to 0.4 respectively. It is shown that the predicted numerical results by the new method (CLM), p-y analysis, and modified Vlasov method (new parameter) agree well with measured results as the relative density increases. Also, the characteristic load method established applicability on the Q-Mnu. relationship below y/D=0.2.

• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.51-62
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• 2016

Parametric studies for various site conditions by using 3d numerical model were carried out in order to estimate dynamic behavior of soil-pile-structure system in dry soil deposits. Proposed model was analyzed in time domain using FLAC3D which is commercial finite difference code to properly simulate nonlinear response of soil under strong earthquake. Mohr-Coulomb criterion was adopted as soil constitutive model. Soil nonlinearity was considered by adopting the hysteretic damping model, and an interface model which can simulate separation and slip between soil and pile was adopted. Simplified continuum modeling was used as boundary condition to reduce analysis time. Also, initial shear modulus and yield depth were appropriately determined for accurate simulation of system's nonlinear behavior. Parametric study was performed by varying weight of superstructure, pile length, pile head fixity, soil relative density with proposed numerical model. From the results of parametric study, it is identified that inertial force induced by superstructure is dominant on dynamic behavior of soil-pile-structure system and effect of kinematic force induced by soil movement was relatively small. Difference in dynamic behavior according to the pile length and pile head fixity was also numerically investigated.

• Journal of Korean Medicine Rehabilitation
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• v.26 no.2
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• pp.13-28
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• 2016

Objectives To investigate anti-obesity effects of Galgeun-tang, an herbal formula, in high fat diet induced obese mice model. Methods 24 Male C57Bl/6J mice were randomly assigned to normal group fed with normal research diet (NOR, n=6), high fat diet control group treated with water (HFD, n=6), high fat diet group treated with Orlistat (ORL, n=6, Orlistat 10 mg/kg), and high fat diet group treated with Galgeun-tang (GGT, n=6, Galgeun-tang 700 mg/kg). 12 weeks later, body weight, fat weight, liver weight, blood glucose, total cholesterol, triglyceride, HDL, ALT, AST, obesity related neuropeptides and adipokines, ratio of gut microbiota, and histopathology of liver were evaluated. Results In the GGT group, 1. body weight gain, liver weight gain, and total fat weight gain were significantly less than those in the HFD group. 2. blood glucose level was significantly lower and insulin level was significantly higher than in the HFD group. 3. total cholesterol level and triglyceride (TG) level were significantly lower and high density lipoprotein (HDL) level was significantly higher than in the HFD group. 4. appetite-promoting ARC neuropeptides such as Agrp and Npy were significantly less and appetite-inhibiting ARC neuropeptide, Cart was significantly more than in the HFD group in qRT-PCR analysis. 5. adiponectin level and visfatin level were significantly higher, and resistin level and leptin level was significantly lower than in the HFD group. 6. the relative level of Bacteroidetes was significantly higher, and the relative level of Firmicutes was significantly lower than in the HFD group. 7. the increase of adipose tissue was significantly more inhibited than in the HFD group. Conclusions The present study showed that Glageun-tang exerts anti-obesity effects in that it. 1. inhibited the increase in body weight, liver weight, and total fat weight. 2. decreased the level of TG, and increased the level of HDL. 3. influenced neuropeptides and adipokines that are important in regulating food intake and changes of body weight. 4. modified the beneficial quantitative changes in gut microbiota suppressing the tendency toward obesity.