• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4C
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• pp.163-174
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• 2009

Mechanical device using the load cell or strain gage sensor can be influenced by tempearute changes because temperature change can cause a shift in the load cell or straing gage output at zero loading. In this paper, micro cone penetrometers with 1~7mm in diameter, are developed by using an optical fiber sensor (FBG: Fiber Bragg Grating) to compensate the continous temperature change during cone penetration test. Note the temperature compensated method using optical fiber sensor which has hair-size in diameter, and is not affected by environmental conditions because the measured data is the wavelength shifting of the light instead of the intensity of the electric voltage. Temperature effect test shows that the output voltage of strain gage changes and increases with an increase in the temperature. A developed FBG cone penetrometer, however, achieves excellent temperature compensation during penetration, and produces continuous change of underground temperature. In addition, the temperature compensated FBG cone shows the excellent sensitivity and detects the interface of the layered soils with higher resolution. This study demonstrates that the fiber optic sensor renders the possibility of the ultra small size cone and the new fiber optic cone may produce more reliable temperature compensated tip resistance.

• Fire Science and Engineering
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• v.26 no.1
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• pp.89-95
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• 2012

In this study, we were manufactured wood flour-HDPE composites by modular co-rotating twin screw extruder with L/D ratio of 42. We was measured cone calorimeter test and thermogravimetric analysis (TGA) to find the combustion characteristics and thermal properties for wood flour-HDPE composites. We then evaluated the effect of three additive-type flame retardants on fire resistance performance. The cone calorimeter test showed that the heat release rate (HRR) of untreated composites was the highest Peak HRR ($446.6kW/m^2$) as well as Mean HRR ($185.5kW/m^2$). From the TGA, it was shown that composites added flame retardants began early thermal decomposition and improved thermal stability.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.910-921
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• 2004

In this study, the pilot tests on the reclaimed land were performed in order to find the suitable construction method with dynamic compaction Type I, Type II at different dynamic energy and hydraulic hammer compaction. The estimation of the compaction through the various pilot tests was performed by the CPT-qc, SPT-N and field density tests. As the result of the pilot tests, it shows that the dynamic compaction method is better than the hydraulic hammer compaction method in the effect of the ground improvement, especially dynamic compaction Type I is much superior to others. When it comes to method for measuring the intensity of the ground, the value of the cone penetration test-resistance(qc) is much suitable for the ground. Besides, the standards for the compaction control, which showed that over 10Mpa at 0 through 5meters in the upper layer and 7Mpa at 5 through 8meters in the lower layer in the CPT-qc, could be found without discrimination of the upper road and lower road on the reclaimed land. And it also found that the intensity of the reclaimed land gets back to the original status in about 10 through 15 days.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1796-1801
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• 2007

Piezocone penetration testing(CPTu) results such as cone resistance$(q_c)$, sleeve friction$(f_s)$, and pore pressure(u), have been carried out at 5 sites in Honam high-speed railway areas of Korea, in order to continuously estimate the characteristics of soil layers and the undrained shear strength$(S_u)$ in a soft ground. For the applications of the conventional CPTu results to undrained shear strength, the cone factors$(N_{kt})$ were deduced based on Field vane tests, and Monte-Carlo Simulation(MCS). Moreover the correlations of the undrained shear strength of CPTu by soil depths were compared and revised with the results of triaxial compression(UU test), field vane and Dilatometer tests(DMT). The depths of soft foundation at 5 sites in Honam high-speed railway areas were calculated based on the results of the various field tests in addition CPTu. The applicability of CPTu for a soft foundation criterion referred to the criteria of high-speed railway and related agencies in Korea was evaluated.

• Agricultural and Biosystems Engineering
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• v.6 no.2
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• pp.59-64
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• 2005

In the study, the cone index, the cohesion and the internal resistant angle of soil were measured before and after tillage in order to suggest relative improvement in soil properties. The tillage methods tested in the study were five combinations of plow and rotary tillage operation and the experiments were performed on five selected test fields. The maximum tillage depth was 20 cm under the ground. The CIs for all the tillage operations were improved in comparison with those before tillage. The best combination of tillage operations for improving the CIs of soil was one plow operation followed by one rotary. After applying the tillage operations, the internal resistance angle reduced by 7-8 degree and the cohesion decreased up to about $1N/cm^2$ in comparison with those before tillage. We concluded that the cone index, the cohesion and the internal resistant angle of soil could be used as measures for representing the relative degree of tillage for a specific tillage operation. In addition, the study was useful as a basic research tool for developing an decision making system that determines an optimal tillage method with soil properties.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.18-23
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• 2010

The estimation of the undrained shear strength $s_u$ for clays using CPT results has been mainly based on the cone factor $N_k$. In this study, a new CPT-based method for the estimation of the undrained shear strength $s_u$ is presented. This aims at reducing uncertainties for the estimation of $s_u$ and enhancing the application of CPT results in more effective manner. For this purpose, a site located at a marine clay deposit is selected and test results from extensive experimental testing program are adopted. The new method defines a direct correlation between the undrained shear strength $s_u$ and the cone resistance $q_t$, excluding the procedure of the overburden pressure correction and therefore undisturbed soil sampling process. In order to verify the new CPT-based method, additional test sites and example sites from literature, which consist of a variety of soil conditions, are selected and examined. It is observed that values of su obtained from the proposed method are in good agreements with measured values of $s_u$ for all the selected verification cases.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.277-283
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• 2004

The time to ignition, heat release rate characteristics and carbon monoxide yield of fiber reinforced and sandwich phenol resin were investigated with cone calorimeter. The fire characteristics of unsaturated polyester, mostly being applied to the existing passenger train, and phenolic resin were compared. Thermal gravimetric analysis(TGA) was used to monitor the degree of thermal decomposition for the phenolic resin. According to the cone calorimeter data, the time to ignition, heat release rate and CO yield was faster and higher as the external heat flux increase. Under the same heat flux, the time to ignition of sandwich type phenolic resin was shorter than that of fiber reinforced. The result of comparison between unsaturated polyester and phenolic resin was that phenolic resin was shown to have better fire resistance than that of unsaturated polyester.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.70-76
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• 2005

The interior materials of the urban subway car in operation are now being changed to new materials that meet the latest law in effect, the fire safety criteria of the urban railway vehicle. It was well known fact that the composite materials, that were applied to last subway car, were weak on the fire. Contrary to this materials, materials in work have good resistance to the fire. On the paper, To investigate the difference of fire safety level on the subway car, cone calorimeter was used to measure the heat release rate and total heat released according to the ISO 5660. A high radiative heat flux of 50kW/m2 was used to burn out all materials and to simulate the condition of fully developed fire case in the tests.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.721-728
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• 2008

Top-Base Method is a stabilization method for light weight structures particularly in the soft ground. It is widely used for the increment of bearing capacity and the effect of restraining settlement when the bearing capacity of the ground is not enough. Top-shaped cone concrete foundations are installed in graveled laid over soft ground. The principle of the basic method is to maximize effect of dispersing the overburden pressure by increasing the contact area of the top-shaped cone. Therefore, the bearing capacity is increased and the settlement is decreased by the embedded resistance of pile part in the ground. In this paper, the plate bearing test was conducted to evaluate the feasibility of Top-Base foundation. Based on the test results, the coefficient of subgrade reaction, elastic modulus, and settlement of foundation on reclaimed land was derived.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1364-1368
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• 2006

By the countermeasure which is caused by with railroad station ground settlement it applied a CGS in each independent foundation. The effectiveness of the ground improvement and the bearing capacity of the compaction pile has been verified by the Cone Penetration Test(CPT) and Load Test. Test result show that penetration resistance and the cone friction force increased a lot and settlement 13.475mm as the standard settlement 40.0mm appeared at below. Also uniaxial compression test result $278kg/cm^2$ as the standard $150kg/cm^2$ appeared far a lot.