• Journal of the Korean GEO-environmental Society
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• v.13 no.9
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• pp.5-16
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• 2012

In the case of using the soil materials created by cutting in-situ ground directly without adjusting particle size, it is recommendable to seek the compaction property or material constant required for filling design or density control through indoor test, and many studies on this subject have been carried out during that time. The researches conducted during that time, however, were focused on the mixed materials with different diameters that exist in a natural condition. There has been no study conducted using coal fly ash that is by-product of the thermal power plant that is actively considered as the building materials. Therefore, this study was aimed at implementing compaction test and examining the basic engineering property in order to explore the influence of crushing the particles through compacting the admixture of crushed stone and coal fly ash produced from thermal power plant on its engineering property, and then the impact of the admixture volume of each material on compaction property and material property by conducting the One-Dimensional Compression Test. As result of compaction test, the optimum moisture ratio of coal fly ash was shown to be approx. 23%. As result of compaction test in accordance with the mixed ratio of coal fly ash and crushed stone under the same compaction energy and moisture ratio, dry unit weight tended to drop when the mixed ratio of coal fly ash exceeded 30%, while it reached approx. $1.81gf/cm^3$ when the mixed ratio was 30%. As result of One-Dimensional Compression Test in accordance with the mixed ratio of crushed stone and coal fly ash, the change in void ratio by particle crushing was at the highest level in the case of coal fly ash 100%, while the lowest level in the case of crushed stone 100%. In the case of mixed materials of crushed stone and coal fly ash, compression index was at the lowest level in case of coal fly ash 30%, and therefore this ratio of mixed material was judged to be the most stable from an engineering aspect.

• The Journal of Engineering Geology
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• v.32 no.1
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• pp.173-191
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• 2022

In this study, the shear wave velocity of the ground was measured using Flat TDR, and the precision analysis of the measured value and the verification of field applicability were performed. The shear wave velocity measurement value was derived in the field using the piezo-stack combined in the Flat TDR. analyzed. As a result of the experiment, the average value of the change in shear wave speed at the time of grout material injection was 10.15 m/s at the beginning of age, and the average value of the change in shear wave speed after the 7th to 14th days was 65.99 m/s, showing a tendency to increase with age. Also, it was found that dry density and shear wave speed increased as the water content increased on the dry side, and that the dry density and shear wave rate decreased as the water content increased on the wet side as the water content increased. The shear modulus value derived from the field test was confirmed to be a minimum of 17.36 MPa and a maximum of 28.13 MPa, confirming a measurement value similar to the reference value. Through this, it can be seen that the measured value of the shear modulus using Flat TDR is reliable data, and it can be determined that the compaction management of the site can be effectively managed in the future.

• Geomechanics and Engineering
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• v.36 no.6
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• pp.619-629
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• 2024

To improve the utilization rate of phosphate tailings (PTs) and widen the sources of subgrade filler, the PTs is employed to modify clay, forming a PTs modified clay, applied in the subgrade. Accordingly, the environmental friendliness of PTs was investigated. Subsequently, an optimal proportion was determined through compaction and California Bearing Ratio (CBR) experiments. Afterward, the stability of mixture with the optimal proportion was further evaluated through the water stability and dry-wet stability experiments. Finally, via the gradation and microstructure experiments, the strength mechanism of PTs modified clay was analyzed. The results show that the PTs were classified in the non-hazardous solid wastes, belonging to Class A building materials. With the increase of PTs content and the decrease of clay content, the optimum water content and the swelling degree gradually decrease, while the maximum dry density and CBR first increase and then decrease, reaching their peak value at 50% PTs content, which is the optimal proportion. The resilient modulus of PTs modified clay at the optimal proportion reaches 110.2 MPa. The water stability coefficient becomes stable after soaking for 4 days, while the dry-wet stability coefficient decreases with the increase of cycles and tends to be stable after 8 cycles. Under the long-term action, the dry-wet change has a greater adverse impact than continuous soaking. The analysis demonstrates that the better strength mainly comes from the skeleton role of PTs and the cementation of clay. The systematic laboratory test results and economic analysis collectively provide data evidence for the advantages of PTs modified clay as a subgrade filler.

• Journal of the Korean GEO-environmental Society
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• v.13 no.1
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• pp.31-36
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• 2012

Recently, industrial by-products are exponentially growing because energy consumption is increasing due to rapid industrial development and improved living standards. The purpose of this study is to determine the proper mixing ratio to meet the liner conditions(must be less than $1{\times}10^{-7}$cm/sec), using pond ash and bentonite as liner. As the result of the compaction test, depending on the increase mixing ratio of bentonite, the maximum dry unit weight was decreased but the optimum moisture content was tended to be increased at the compaction curve. As the result of the permeability test, depending on the increase mixing ratio of bentonite, the coefficient of permeability showed tendency to be decreased in the form of index and the tendency was caused by the hydration reactions filling the void of the pond ash. When the mixing ratio of bentonite was approximately over 15%, it was satisfied with the land fill liner conditions. In other words, it is necessary to consider other mixtures containing the cement or another material in the economical aspect for application of the pond ash.

• Journal of the Korean GEO-environmental Society
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• v.11 no.6
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• pp.47-55
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• 2010

The recycled fine aggregates were mixed with weathered granite soils typically used for fill materials and tested engineering properties, physical properties, and compaction characteristics according to the mixing ratio of the mixed soils. The results of this study were as follows. For the results of A-type compaction test, the recycled fine aggregates showed low effects compared to the weathered soils, but the mixed soils which were mixed with the weathered granite soils and the recycled fine aggregates showed good compaction effects. Especially, the mixing ratio of 70:30 by weight showed for maximum compaction result. From the results of the direct shear test, the cohesion was ince csed according to proportion of the weathered granite soils. The weathered granite soils neared the optimum moisture content showed for maximum shear strength paramcoers, while the cohesion of the mixed soil was relatively ince csed in the wet side of the optimum moisture content. This trend was seemed to remained cence composition in the recycled fine aggregates. The internal friction angle of the recycled fine aggregates and the mixed soils showed maximum value near dry side of the optimum moisture contents. And the internal friction angles of the mixed soils were increased according to higher proportion of the recycled fine aggregates.

• Geomechanics and Engineering
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• v.19 no.5
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• pp.435-445
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• 2019

A series of element tests with different drainage conditions and strain rates were performed on compacted unsaturated non-plastic silt in unconfined conditions. Soil samples were compacted at water contents from dry to wet of optimum with the degree of saturation varying from 24 to 59.5% while maintaining the degree of compaction at 80%. The tests performed were shear infiltration tests in which specimens had constant net confining pressure, pore air pressure was kept drained and constant, just before the shear process pore water pressure was increased (and kept constant afterwards) to decrease matric suction and to start water infiltration. In constant water content tests, specimens had constant net confining pressure, pore air pressure was kept drained and constant whereas pore water pressure was kept undrained. As a result, the matric suction varied with increase in axial strain throughout the shearing process. In both cases, maximum shear strength was obtained for specimens prepared on dry side of optimum moisture content. Moreover, the gradient of stress path was not affected under different strain rates whereas the intercept of failure was changed due to the drainage conditions implied in this study.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.492-497
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• 2008

The objective of this research is an investigation of engineering properties of weathered granite soil mixed with Phosphogypsum and recycled EPS beads as an light-weighted soil. A series of geotechnical laboratory tests including physical index test, compaction test, CBR test and direct shear test were performed for various mixing ratios. Based on the laboratory test results, it was found that the maximum dry unit weight of the light weight soil ranges $1.46{\sim}1.61g/cm^3$ and the maximum dry unit weight decreases about 11~19.3% with the increase of amount of the recycled EPS beads and the optimum moisture content increase. Since the CBR values of the light weight soil ranges 10.4~18.4%, the light weight soil mixed with Phosphogypsum and recycled EPS beads can be used as a light weight backfill material on the soft soil.

• Smart Structures and Systems
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• v.6 no.7
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• pp.851-866
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• 2010

This paper presents a new concept of using PZT (lead zircornate titanate) transducers as a non-destructive testing (NDT) tool for evaluating quality of concrete. Detection of defects in concrete is very important in order to check the integrity of concrete structures. The electro-mechanical impedance (EMI) response of PZT transducers bonded onto a concrete specimen can be used for evaluating local condition of the specimen. Measurements are carried out by electrically exciting the bonded PZT transducers at high frequency range and taking response measurements of the transducers. In this study, the compression test results showed that concrete specimens without sufficient compaction are likely to fall below the desired strength. In addition, the strength of concrete was greatly reduced as the voids in concrete were increased. It was found that the root mean square deviation (RMSD) values yielded between the EMI signatures for concrete specimens in dry and saturated states showed good agreement with the specimens' compressive strength and permeable voids. A quality metric was introduced for predicting the quality of concrete based on the dry-saturated state of concrete specimens. The simplicity of the method and the current development towards low cost and portable impedance measuring system, offer an advantage over other NDE methods for evaluating concrete quality.

• Geomechanics and Engineering
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• v.27 no.6
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• pp.573-582
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• 2021

From the effect of bound water, this study aims to seek the potential reasons for difference of mechanical experiment results of subgrades soils. To attain the comparatively test condition of bound water, dry forming (DF) and wet forming (WF) were used in the specimen forming process before testing, series of laboratory tests, i.e., CBR tests, direct shear tests and compaction tests. The measured optimal moisture contents, maximum dry densities, CBR, cohesion c, and internal friction angle 𝜑 were given contrastive analysis. Then to detect the adsorptive bound water in the subgrade soils, the thermal gravimetric and differential scanning calorimetry (TG-DSC) test were employed under different heating rates. The free water, loosely bound water and tightly bound water in soils were qualitatively and quantitatively analyzed. It was found that due to the different dehydration mechanics, the lost bound water in DF and WF process show their own characteristics. This may lead to the different mechanical properties of tested soils. The clayey particles have a great influence on the bound water adsorbed ability of subgrade soils. The more the clay content, the greater the difference of mechanical properties tested between the two forming methods. Moreover, in highway construction of southern China, the wet forming method is recommended for its higher authenticity in simulating the subgrade filed humidity.

• Nuclear Engineering and Technology
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• v.26 no.1
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• pp.54-62
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• 1994

The hydraulic properties of domestic natural clay/crushed rock mixture suggested as a candidate backfill material for the low and intermediate level waste repository were investigated. The dry density-water content relationship was studied to define an optimum water content that gives a maximum attainable dry density at constant compaction pressure. The hydraulic conductivities of clay/crushed rock mixture as a function of clay content were also measured. As the clay content decreased, the maximum attainable dry density increased and the optimum water content became more distinct. However the attainable density is not significantly sensitive to water content. The hydraulic conductivities of the mixture increased from 5 $\times$ 10$^{-12}$ m/s to 7 $\times$ 10$^{-10}$ m/s with clay content decreasing from 100 wt.% to 25 wt.% at dry density of 1.2 Mg/㎥. In case of dry density of 1.5 Mg/㎥, they maintain the lower values of 5 $\times$ 10$^{-12}$ m/s even at 25 wt.% clay content. The concept of effective clay dry density was suggested to estimate the hydraulic conductivity of the mixture. It was shown that the effective clay dry density concept can explain welt the hydraulic conductivities of the mixtures with various dry density and crushed rock content.