• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1253-1257
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• 2010

그라우팅은 건설공사에서 지반의 갈라진 틈이나 공동, 공극 등에 적절한 충전재를 압력을 이용하여 주입하는 것으로, 굴착공사 시 누수방지와 불안정한 지반의 보강을 위하여 광범위하게 사용되고 있다. 가장 많이 사용되고 있는 그라우팅 주입재의 재료로는 물유리계를 주재료로 사용하는 약액주입공법이 많이 사용되어지고 있다. 기존의 물유리계 재료를 사용할 경우 발생하는 용출현상 및 강도저하를 보완하기 위하여 가소성을 부과한 무기질계 재료ECG(Eco Clean Grouting)를 사용하여, 강도 및 내구성이 우수하고 주입재의 용출 현상이 발생하지 않아 환경오염 문제가 거의 없는 영구적인 차수 및 보강에 적합한지와 친환경적 특성을 확인한다. 본 연구는 가소성 무기질계 재료인 ECG(Eco Clean Grouting)재료를 사용하여 현재 많이 사용되는 재료인 물유리계 재료로 일축압축강도, 체적변화, 내구성 평가, 투수시험, 어독성 시험, 용탈시험등을 수행하여 비교 분석 하였다. 일축압축 시험결과 재령 28일 강도는 ECG가 물유리재료에 비해 크게 발현되었고, 내화학성시험 결과 ECG의 길이변화율이 거의 없는 것으로 내화학성에서 강점을 보였다.

• Geotechnical Engineering
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• v.3 no.2
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• pp.17-28
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• 1987

Reliability of the cone penetration test (CPT) for estimating shear strength of marine soils is investigated in this paper. For sands, the uncertainty about the angle of internal friction is analyzed. It includes the spatial variation of the soil and the model error in the equation used for interpretation. The most serious uncertainty encountered was the error in the interpretative models. Different methods of interpretation gave quite different values. Subjective opinion was introduced to combine all the interpretative models in a systematic manner. For clays, the undrained Shear Strength from the CPT results is usually =derived by empirical correlations between cone resistance and untrained shear strength from laboratory tests or field vane tests, expressed in terms of cone factor and function of overburden pressure. The uncertainty of the undrained shear strength is caused by data scatter of the cone factor in the correlation, model error of the cone factor, effect of anisotropy, and spatial variability of cone resistance. Among these uncertainties, the most serious one was the data scatter of the cone factor in the .correlation. Between the laboratory test and the field vane test used for correlation, the field vane test was more reliable.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.701-704
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• 2008

The case of failure of Alkali-silica reaction (ASR) on the cement concrete pavement was reported in Korea. In the United States America, the fly ash has less than 10 percent Cao reported that prevent expansion by ASR. Most of all fly ash in Korea have less than 10 percent CaO, therefore it is similar ASTM F fly ash in the USA. Crushed aggregates of the test section had expansion behavior by potential ASR that the ASTM C 1260 test method tested expansion 0.17 percent during 14 days. The test section of concrete pavement used crushed aggregate was constructed that fly ash have 20 percent weight of cementitious materials to prevent expansion by ASR. This study was performed flexural strength test for elapsed days and durability by freeze-thaw test. It was shown that flexural strength was increased elapsed days and good performed freeze-thaw test. This study shown that fly ash concrete pavement was good performance in the test section.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.145-157
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• 2017

Because of Recent intensive rainfall, nationally landslides and slope failure phenomenon has been frequently occur. Providing proposed-measures to the natural disasters that occur in these localities and the slope, must be derived ground of strength parameters(shear strength) as a design input data. However, it is such as extra deforestation and a lot of economic costs in order to make the access to the current area and the slopes ground survey is required. Thus, by small dynamic cone penetration test machine using the human to carry in the field, it is possible to easily measure the characteristics and strength constant of the ground of more than one region. In this study through researching analysis of the domestic and foreign small dynamic cone penetration test method, it has proposed a cone material and test methods suitable for the country. Cone penetration test Nc in the field has comparated with analysis of the value and the standard penetration test N value. And, in addition to this, direct shear test and borehole shear test were performed by depth, bedrock, and soil type and passing #200 and the correlation of the Nc value. In particular, in the present study, for the sandy soil that has distict distribute in mountain, it is proposed relation of shear strength corresponding to the Nc value (cohesion and internal friction angle) in order to calculate such effective ground shear strength.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.169-179
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• 2003

Undrained shear strength of clay deposit is one of the most important properties in the design of geotechnical structures. The use of piezocone test is rapidly growing due to its merit that can measure the in-situ undrained shear strength continuously with less error. The reliability of the shear strength from piezocone test depends upon the cone factor applied. Many researchers have suggested different ranges of values for the factors. This study performs to find out the validity of the suggested values in Korea and their charateristics related to the mechanical properties of clay. Piezocone tests were performed at the site of pilot project of ground improvement at Yangsan-Mulgeum Gyeongnam to investigate the charateristics of piezocone factors. The piezocone fators$(N_{kt}, N_{ke}, N_{\Delta u})$ based on the undrained shear strength from quick triaxial compression test are generally within the suggested range. And there appears considerable relations between undrained shear strength and $(N_{kt}, N_{ke}, N_{\Delta u})$ and between preconsolidation pressure and $(N_{kt}, N_{ke})$, while plasticity index, rigidity index and friction ratio do not show any relations with cone factors. The results also reveal that factor $(N_{\Delta u})$ shows higher reliability than factors $(N_{kt} and N_{ke})$, which show smaller standard deviation, breadth of change and scattering.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.110-114
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• 2009

This study is for the evaluation of compressive strength restoration of sandwich composite laminates with adhesively bonded scarf patches. It was used in this study that the sandwich composite laminate with an aluminum honeycomb core and CF1263 woven fabric carbon/epoxy faces was applied to the car body structure for Korean tiling train. In this study, it was damaged by low velocity impact and repaired using scarf repair method. Then, the compressive strength restoration of assessed by compressive after impact (CAI) test. From the test, it could be known that the compressive strength was restored up to 72% by only scarf repair method and 91% applied by an extra ply over the undamaged one.

• Composites Research
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• v.27 no.2
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• pp.77-81
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• 2014

In this study, it was performed damage assessment and repair of small scale aircraft adopted on composite. This aircraft adopted the sandwich structure to skin of wing. This study aims to investigate the residual strength of sandwich composites with nomex honeycomb core and carbon fiber face sheets after the open hole damage by the experimental investigation. The 4-point bending tests were used to find the bending strength, and the open hole was applied to introduce the simulated damage on the specimen. The bending strength test results after open hole were compared with the results of no damaged specimen test. In addition, The damaged composite structure was repaired using external patch repair method after removing damaged area. After that, this study presents comparison results of the experimental investigation between the damaged and the repaired specimen. It was found that the bending strength of repaired specimen was recovered up to 95% of undamaged specimen.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.541-544
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• 2008

Recently, due to the increase of high-rise buildings construction, many researches for making harden of concrete earlier and remove of forms faster are being performed to reduce construction period. The purpose of this study is to analysis which mixing condition and curing temperature of early strength concrete. Porperties of concrete by the different factors, such as the type of active admixtures, mineral admixtures, curing temperature, the amount of binder, etc. Through the test of concrete using the different type of admixture, PC type was more excellent than PNS type admixture. The concrete Strength remarkably will be able to confirm that decreases from temperature below 12$^{\circ}C$.

• Journal of the Korean GEO-environmental Society
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• v.10 no.3
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• pp.5-12
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• 2009

This study presents static and dynamic strength of coal ashes collected from disposal site of power plant. Main compositions of coal ashes were bottom ashes. In order to evaluate static and dynamic characteristics of coal ash, NGI direct-simple shear tests, cyclic simple shear tests and direct shear tests were conducted. The strengths of coal ashes from those tests were compared to those of sands. Bottom ashes among coal ashes used for this study were classified as sand from the grain size distribution and show higher strength properties than the sands. For utilization of coal ashes in civil engineering project, mixing coal ashes with sandy soil using batch plant is inconvenient and the cost is higher than the spreading sand layer and coal layer alternately. In order to simulate both mixing type and layered type construction, sands and coal ashes were mixed with volume ratio 50:50 and prepared sand and coal ash layers alternately with the same volume ratio. From the tests mixed coal ashes-specimen shows slightly higher static and cyclic strength than the layered specimen at the same density. The higher strength seems due to the angular grain of bottom ashes. The cyclic stress ratio at liquefaction decreases rapidly as the number of cycle increases at mixed specimen than that of layered specimen.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.225-234
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• 2008

This study was carried out to select proper loading speed for deformation strength ($S_D$) of asphalt mixtures. Kim test using loading head of diameter(40mm) with radius(10mm) was conducted to measure $S_D$ in different loading speed (10mm/min, 30mm/min, 50mm/min, 70mm/min) and wheel tracking test was also conducted. The regression analyses between the So values and WT results were carried out by loading speeds. Higher $S_D$ was observed as increasing loading speed. This means that loading speed is a high influencing factor on $S_D$. The loading speed of 30mm/min was found as an optimum for better correlation with WT results than any other speeds from the regression analysis between $S_D$ and wheel tracking test results. $S_D$ value measured at other loading speed than 30mm/min has to apply the conversion coefficients.