• Economic and Environmental Geology
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• v.46 no.6
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• pp.535-544
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• 2013

Influence of sulfate on the early hydration in the solidification treatment of abandoned mine tailings was characterized. Solidified specimens using hydrated lime as a binder were prepared with various amounts of added $Na_2SO_4$ and different curing days. Unconfined compressive strength measurement, heavy metal leaching test, XRD analysis were performed after 7-, 14- and 28-days curing. According to curing days strength of solidified specimens using only distilled water increased but those with addition of $Na_2SO_4$ decreased. External cracks of specimens developed definitely with increasing $Na_2SO_4$ concentration and curing days. Concentrations of Cu, Cd, Zn, and As in the leached solutions from solidified specimens decreased significantly but Pb was leached readily in cases of hydrated lime dosage more than 10 wt%. Gypsum and $MgSO_4$ were identified in the cracked solidified specimens by XRD analysis, and pillar-shaped crystals of SEM image were identified as gypsum in reference with EDS analysis. Crystallization of sulfate in the process of lime-tailing solidification caused cracking, which should be supplemented for solidification treatment of highly sulfur-contained tailing.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.673-686
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• 2018

The physical properties of rocks constituting the rock mass were analyzed by using various methods such as 7 kinds of physical properties of about 2,400 data. The correlation equation was derived from the correlation equation with the dependent variables by screening independent variables through the significance level using multiple regression analysis. In order to verify the reliability of this equation, verification was performed through comparison with actual data using artificial neural network learning. The analysis results by petrogenesis and strength confirmed that the elastic wave velocity (compressional wave) and elastic modulus as the main influence factors for the independent variables affecting the dependent variables. This proves that most of the correlation equations using the above items are found in existing studies. And through this study, it is confirmed whether the rock classification is based on the above items in various standards. In addition, the analysis results of representative rocks showed a high correlation as the equation for estimating unconfined compressive strength and elastic modulus exceeds the coefficient of determination 0.8.

• Journal of the Korean GEO-environmental Society
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• v.11 no.5
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• pp.25-34
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• 2010

In this study characteristics for reclaimed ash was studied to enlarge the usage of reclaimed ash which is reaching to 72 million ton producted from whole thermal power plants in South Korea. Fly ash and bottom ash are reclaimed separately at some of thermal power plants. However, typically bottom ash and fly ash are mixed when they are buried at most of the thermal power plant, as a result the engineering characteristics of ponded ash are not investigated properly. In order to investigate the engineering characteristics of the ponded ash, laboratory tests were performed with ponded ash and fly ash from youngheung and samcheonpo thermal power plants. Specific gravity, unit weight, and grain size analysis test were fulfilled to evaluate the physical characteristics and triaxial permeability test, direct shear test, unconfined compressive strength test, compaction test were performed to evaluate the mechanical characteristics. And also engineering characteristics of coal ash from anthracite and Bituminous thermal power plants were compared and studied respectively. As a result of the study, it was confirmed that using coal ash from Bituminous thermal power plants can be effective in the place where lightweight materials are required and using coal ash from anthracite thermal power plants can be effective as backfill material which require higher permeability. Finally, it was confirmed that fly ash from youngheung thermal power plants which has the lowest permeability among the tested material is suitable for a field requiring impermeable material.

• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.251-258
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• 2006

In this paper, the applicability to the Korean rock condition of using the deformation moduli based on Rock Mass Rating (RMR) and Pressuremeter Test (PMT) is evaluated. The correlations among deformation moduli and various rock properties were also analyzed. It appears that the existing correlations using RMR overestimate the deformation moduli and wide variation was found between predicted moduli using these correlations and measured values. As for the correlations among the deformation moduli and various rock properties, Rock Quality Designation (RQD) and unconfined compressive strength (UCS) were found to correlate to deformation moduli reasonably well, but joint spacing and joint conditions appear to correlate poorly to RQD and UCS. Additionally, groundwater can not be correlated with the modulus values. While the depth has very little contribution to deformation modulus, it should be factored in the simple regression analyses with various rock mass properties, especially with the correlations made with UCS, RQD etc. With the deficiencies of these correlations, more in depth analysis techniques such as multivariate correlations may be to reliably estimate deformation modulus of rock mass.

• Clean Technology
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• v.24 no.4
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• pp.315-322
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• 2018

Industrial use of waste oyster shells is limited because of requiring excessive energy for converting natural oyster shells in the form of calcium carbonate ($CaCO_3$) into calcium oxide (CaO) for this purpose. This study aimed to develop energy-saving process for producing solidifying agent using waste oyster shells for backfill materials. It was suggested that oyster shells were converted to calcium sulfates which were mixed with sodium hydroxide solution and red clay, forming solid specimen. The optimal concentrations of sulfuric acid for sulfation of oyster shell and sodium hydroxide to generate calcium hydroxide ($Ca(OH)_2$), were determined. Unconfined compressive strength of solid specimen increased with increasing the content of solidifying agent while it increased also with increasing ratio of natural oyster shells to coal ash. The result clearly demonstrates that solidifying agent consisting of sulfuric acid-treated oyster shell, coal ash, and sodium hydroxide solution, can be effectively utilized for preparing backfill materials using natural oyster shell and coal ash. Sulfuric acid-treated oyster shell-based solidifying agent has not been previously developed and will contribute to broaden industrial application of waste oyster shells.

• Journal of Soil and Groundwater Environment
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• v.6 no.3
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• pp.53-59
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• 2001

There is a lot of method to manage the insanitary landfill but vertical cutoff walls have been widespreadly used and were installed into the subsurface to act as a barrier to horizontal groundwater flow, The stabilized material such as specialized cement or mixed soil with additives has been generally applied for the materials of the deep soil mixing barrier in korea. The amount of the stabilized material is dependent on the field conditions, because the mixing ratio of the material and the field soil should achieve a requirement in the coefficient of permeability, lower than 1.0$\times$$10^{7}$cm/sec. This study determined the quantity and optimized function ratio of the stabilized material in the formation process of the mixed barrier that was added with stabilized material on the field soil classified into SW-SC under USCS (Unified Soil Classification System). After that the fly ash and lime were selected as an additives an that could improve the function of the stabilized material and then the method to improve the functional progress in the usage of putting into the stabilized material as an appropriate ratio was studied and reviewed. The author used the flexible-wall permeameter for measuring the permeability and unconfined compressive strength tester for compressive strength, and in the view of environmental engineering the absorption test of heavy metals and leaching test regulated by Korean Waste Management Act were performed. As the results, the suitable mixing ratio of the stabilized material in the deep soil mixing barrier was determined as 13 percent. To make workability easy, the ratio of stabilized material and water was proven to be 1 : 1.5. With the results, the range of the portion of the additives(fly ash : lime= 70 : 30) was proven to be 20-40% for improving the function of the stabilized material, lowering of permeability. In heavy metal absorption assessment of the mixing barrier system with the additives, the result of heavy metal absorption was proved to be almost same with the case of the original stabilized material; high removal efficiency of heavy metals. In addition, the leaching concentration of heavy metals from the leaching test for the environmental hazard assessment showed lower than the regulated criteria.