Soo-Kack Noh

Analysis of Strength Characteristic for Bottom Ash Mixtures as Mixing Ratio and Curing Methods

Bottom Ash is industrial by-product from a thermoelectric power plant. An immense quantities of bottom ash have increased each year, but most of them is reclaimed in ash landfill. In this study, in order to raise recycling rate of Bottom Ash, it is suggested to cure Bottom Ash (BA) mixtures mixed with cement, lime, Fly Ash (FA), and oyster shell (OS). Mixtures of 5~20 % mixing ratio had been cured for 1, 3, 7, 14, and 28 days using sealed curing and air-dry curing method. Unconfined compressive strength test was conducted to determine strength and deformation modulus () change for mixtures as mixing ratio and curing day, water contents of mixtures were measured after test. As a result, strength and were increased as mixing ratio and curing days, but values and tendencies of them appeared in different as kind of mixture, mixing ratio, curing method, and curing days. The results showed the addition of cement, lime, Fly Ash, and oyster soil in Bottom Ash could improved strength and and enlarge its field of being used.

Characterization of CO2 emissions during construction of reservoir embankment elevation in South Korea

PurposeThe environmentally friendly construction of agricultural infrastructure is much needed for sustainable development because construction is recognized as a cause of environmental degradation. The objective of this study was to estimate and characterize carbon dioxide (CO2) emissions during construction of agricultural reservoir embankments for the quantitative environmental assessment and management of CO2 emissions using life cycle assessment method.MethodsTwo reservoirs with different foundation treatment and construction components were selected in this study and their characteristics in CO2 emissions were compared. And CO2 emissions were calculated separately for each of the following major components: construction materials, equipment, and transport. The basic unit of CO2 emissions for construction materials was calculated using the 2009 input–output tables in Korea and the basic unit of CO2 emissions for equipment of transport and construction was also calculated based on the amount of fuel used in a unit time.Results and discussionAccording to the study results, the construction of a water supply process appeared to generate the most emissions among all processes for the two sites. Emissions due to equipment were the highest in site A, while materials generated the most emissions in site B. Differences in emissions are due to differences in the construction process. While the operation time of the equipment in site A increased due to the cofferdam process and a large amount of cement was used in the foundation process in site B.ConclusionsCharacteristic of CO2 emissions differs with different construction processes and thus construction processes need to be optimized for environmental friendly development of agricultural infrastructure through estimation and characterization of CO2 emissions.

The Electrical Properties and Unconfined Compression Strength of Bottom Ash

The objective of this study is to find the electrical properties of Bottom ash from thermoelectric power plants in Korea. By using Parallel Plate Method, the electrical resistivity and dielectric constant were measured at the frequency from 20 Hz to 10 MHz. Also, unconfined strength test, XRF and sieve analysis were performed for finding the relationship between strength, physiochemical properties and electrical properties. In the result, the change of electrical resistivity and dielectric constant of bottom ash against frequency was similar to that of general soil. The proportion of fine grain in bottom ash had the positive correlation with dielectric constant and negative correlation with electrical resistivity. Chloride and sulfur trioxide were proportional to dielectric constant and the more bottom ash had chloride content, the lower electrical resistivity appeared in bottom ash. Unconfined strength of bottom ashes had a range from 200 kPa to 780 kPa and strength was inverse proportional to electrical resistivity.

Alternative Methods for Classification on Weathered Strata

The undisturbed specimens used in this research were sampled in the field by the sequential sampling method. In addition, four testing methods were applied to identify for the characteristics and classification of weathered strata. N-value by standard penetration test was obtained from in the field and then analyzed using normalization method. Other methods such as X-ray grain size distribution, X-ray fluorescence spectroscopy(XRF), and fall cone test were carried out in the lab. These analyzed results indicate that distribution of particle, composition of minerals are changed in accordance with the degree of weathering, unusual strata and depth. Consequently, the weathered strata can be extensively separated into two parts according to the test results and each part was shown different in the strata characteristics. It can be prospected that mechanical characteristics should be different, even though mechanical tests were not applied. Furthermore, these results not only make up for the error by one testing method but also contribute more effectively and economically to the design and the construction.

Analysis of Effect of Compaction Energy on Characters of Grain Size Distribution, Compaction and Permeability Using Fragmentation Fractal

Particles of soil are crushed when soil is compacted in the in-situ or lab. Among many factors that affect the crush of particles, compaction energy is a major factor. Because the crush of particles can change physical properties, the analysis of effect of compaction energy is very important. In this study, the fragmentation fractals were used for determining the change in grain size distribution and the effect due to change in grain size distribution was estimated. Compaction energy was increased by 50, 100, 200 and 300% based on the energy of standard A compaction test. As a result, grain size distribution curves were changed and fine particles increased as compaction energy were increased. Relative compaction were ranged between . Fractal dimension of each site increased as compaction energy increased. Relative compaction is proportional to the fractal dimension but coefficients of permeability were in inverse proportional to the involution of fractal dimension.

The Time-Dependent Behavior Characteristic of Bottom Ash by Maximum Particle Size and Application of Creep Models

This study finds the characteristics of long-term settlement of Bottom Ash and to review the application of Singh-Mitchell creep equation and Burgers Model to the creep behavior of Bottom Ash. In the undrained state, it was confirmed that creep behavior appeared in the range to 30-80 % of the maximum deviator stress by applying condition in other three stresses through triaxial compression test after isotropically consolidation. By using sieve analysis, it was compared to each sample that was passed through 9.5 mm, 2 mm, 0.25 mm sieves. Also, using Singh-Mitchell creep equation and Burgers Model, it was compared between the theoretical behavior and the observed behavior for each sample. In the result, it is found that creep behavior of Bottom Ash is similar to the theoretical behavior of Singh-Mitchell creep equation and Burgers Model in early stage and it is possible to predict creep behavior of Bottom Ash by these models.

Undrained Creep Characteristics of Silty Sands and Comparative Study of Creep model

Soils exhibit creep behavior in which deformation and movement proceed under a state of constant stress or load. In this study, A series of triaxial tests were performed under constant principal stress in order to interpret the undrained creep characteristics of silty sands. Although samples are non-plastic silty sands, the results of tests show that the creep deformation increasing over time. Based on the results of test, Singh-Mitchell model parameters and Generalized model coefficients were calculated. Generalized model showed slightly larger deformation in the primary creep range but secondary creep deformation was almost identical. Although Singh-Mitchell model showed relatively large errors compared to Generalized model because it uses the average of test results, but Singh-Mitchell model can be easily represented by three creep parameters.

Sensitivity Analysis of Soil Properties for the Slope Safety Factor in Embankments utilized Bottom Ash and Dredged Soil Mixture

In the construction industry, the interest for recycling aggregates is rising as more people demand for alternatives due to lack of supply of natural aggregates and environmental problems. However, in order for recycled aggregates to be used in infrastructures, stability and other factors need to be verified. Therefore, the objective of this study is to analyze the sensitivity of soil properties to secure slope safety according to various heights of embankment when bottom ash and dredged soil mixture is applied in the embankment. In most cases, all heights were safe for the slide for the embankment whether the water level is full or sudden draw down. The result of the sensitivity analysis revealed that the unit weight of embankments is highest among all factors to be considered. However, the sensitivity of the unit weight became smaller and the sensitivity of the friction angle of embankments increased with the height of embankments. The sensitivity of factors of core materials is very small because the core has weaker physical properties than those of the embankment. The effect of the height for each factor is different for each slope and water levels. The sensitivity of the unit weight of embankments is most affected when the height is 60m in the upstream slope. To conclude, bottom ash and dredged soil mixture can be applied in the embankment and different factors must be considered in different scale because the sensitivity depends highly on the height of embankments.

Analysis on Correlation between CO 2 Emissions and Production, Acreage of Crops using Environmental Input-Output Analysis

South Korea is under pressure to reduce emissions because of expanding request for reducing emissions. In many industry sectors, emissions were analyzed to reduce emissions. But little effort in researching agricultural sector has been undertaken because it is recognized as environmentally friendly industry. The object of this research is to estimate emissions of crops and analysis on correlation between emissions and production, acreage of crops. In this study, environmental input-output analysis was used to estimate emissions of agricultural sector and spearman correlation coefficient was used to analysis on correlation between emissions and statics like production and acreage. As a result, rice, barley, pulses and horticultural specialities had correlation with acreage and correlation coefficients of these crops were 0.800~0.933. Regression equations about emissions and acreage of rice, barley, pulses and horticultural specialities was made and of these equations were 0.615~0.929. Using equations, emissions of rice, barley, pulses and horticultural specialities can be estimated with acreage.

Analysis of dust emission characteristic by drop impact on decomposed granite soil

Dust is mostly caused by human activity. The effect of natural factors on dust emission were studied in many research, but the little effort in researching artificial factors of dust emission. The object of study is to analysis dust emission characteristic by drop impact. Particle matter 10μm (PM10) was measured by drop impact on paved soil with changing drop height, weight and drop size. Increasing drop height cause more PM10 emission. Increasing drop weight cause more PM10 emission but had limit weight for increasing dust emission. Because the exceed kinetic energy of drop weight penetrate the soil surface. The limit perimeter was exist that separating PM10 emission aspect. Under limit perimeter, PM10 emission was increasing while perimeter was increasing, but over limit perimeter showed the opposite aspect. Regression equations for estimating PM10 with kinetic energy and perimeter were made under limit perimeter and over limit perimeter. The R of those equations were 0.784, 0.743. The error has occurred between measured PM10 and calculated PM10 in the equation under limit perimeter. But using equation of case for over limit perimeter, PM10 can be estimated with kinetic energy and drop perimeter.