• Geomechanics and Engineering
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• v.6 no.3
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• pp.249-262
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• 2014

Tire chips and tire chips-soil mixtures can be used as alternative fill material in many civil engineering applications. In this study, the potential benefits of using tire chips as lightweight material to improve the bearing capacity and the settlement behavior of sand slope was investigated experimentally. For this aim, a series of direct shear and model loading tests were conducted. In direct shear tests, the effect of contents of the tire chips on the shear strength parameters of sand was investigated. Different mixing ratios of 0, 5, 10, 15 and 20% by volume were used and the optimum mixing ratio was obtained. Then, laboratory model tests were performed on a model strip footing on sand slope reinforced with randomly distributed tire chips. The loading tests were carried out on sand slope with relative density of 65% and the slope angle of $30^{\circ}C$. In the loading tests the percentage of tire chips to sand was taken as same as in direct shear tests. The results indicated that at the same loading level the settlement of strip footing on sand-tire chips mixture was about 30% less than in the case of pure sand. Addition of tire chips to sand increases BCR (bearing capacity ratio) from 1.17 to 1.88 with respect to tire chips content. The maximum BCR is attained at tire chips content of 10%.

• Advances in concrete construction
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• v.11 no.4
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• pp.307-314
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• 2021

Activated hwangtoh (ACT) is a natural resource abundant in South Korea, approximately 15.0% of soil. It is an efficient mineral admixture that has activated pozzolanic properties through high-temperature heating and rapid cooling. The purpose of this study is to improve a curb mixture that can reduce NOx outside and investigate durability performance. To this end, mortar curb specimens were manufactured by replacing OPC with ACT. The ACT substitution ratios of 0.0, 10.0, and 25.0% were considered, and mechanical and durability tests on the curb specimens were conducted at 28 and 91 days of age. Steam curing was carried out for three days for the production of curbs, which was very effective to strength development at early ages. The reduction in strength at early ages could be compensated through this process, and no significant performance degradation was evaluated in the tests on chloride attack, carbonation, and freezing and thawing. The mortar curb with an ACT of 10.0~25.0% replacement ratio exhibited clear NOx reduction through photocatalytic (TiO2) treatment. This is due to the increase in physical absorption through surface absorption and the photocatalyst-containing TiO2 coating. In this study, the reasonable range of the ACT replacement ratio for NOx reduction was quantitatively evaluated through a comprehensive analysis of each test.

• Geomechanics and Engineering
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• v.36 no.3
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• pp.247-258
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• 2024

Tailings are waste materials of mining operations, consisting of a mixture of clay, silt, sand with a high content of unrecoverable metals, process water, and chemical reagents. They are usually discharged as slurry into the storage area retained by dams or earth embankments. Poor knowledge of the hydro-mechanical behaviour of tailings has often resulted in a high rate of failures in which static liquefaction has been widely recognized as one of the major causes of dam collapse. Many studies have dealt with the static liquefaction of coarse soils in saturated conditions. This research provides an extension to the case of silty tailings in unsaturated conditions. The static liquefaction resistance was evaluated in terms of stress-strain behavior by means of monotonic triaxial tests. Its dependency on the preparation method, the volumetric water content, the void ratio, and the degree of saturation was studied and compared with literature data. The static liquefaction response was proved to be dependent mainly on the preparation technique and degree of saturation that, in turn, controls the excess of pore pressure whose leading role is investigated by means of the relationship between the -B Skempton parameter and the degree of saturation. A preliminary interpretation of the static liquefaction response of Stava tailings is also provided within the Critical State framework.

• Journal of the Korean Institute of Landscape Architecture
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• v.39 no.6
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• pp.110-117
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• 2011

In order to study the growth models between the growth of Sedum takevimense and growth rate in soil with three types of mix ratios, this experiment was carried out on April 3rd, 2011. A nonlinearity regression analysis was performed using the Logistic and Gompertz models by SPSS. According to the study of growth models of Sedum takevimense, the process of growth and management methods after over-wintering were explicitly determined. According to the measured values, the growth in the soil of $P_1P_2V_1$ and $P_2P_1V_1$ was better than that of $P_1$. Particularly, the average length of Sedum takevimense in the soil of $P_1P_2V_1$ was about twice as great as that in the $P_1$. The fitness test of the two growth models was: The predicted value and measured value were separately compared and analysed, the average fitting precision $R^2$ of the Logistic models was 0.995, but the average $R^2$ of the Gompertz models was below 0.978, which showed that the Logistic models were better than the Gompertz models. The growth models also showed that the growth time of Sedum takevimense was divided into three: rapid, most rapid and slow. When managed in the rapid and the most rapid time, it will grow better.

• Journal of the Korean Geotechnical Society
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• v.36 no.1
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• pp.17-28
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• 2020

This study presents the experimental results of ground improvement efficiency induced by enzyme-induced carbonate precipitation (EICP) in soils. First, the optimal mixture ratio of EICP solution was determined by comparing the amount of induced carbonate depending on the different ratio among urea, CaCl₂, and urease. Next, we evaluated the shear stiffness and strength of EICP-treated sandy soil by performing shear wave velocity measurement and triaxial shear test. Furthermore, induced carbonate in treated soil was visually investigated by X-ray CT and SEM analysis. The results showed that the maximum shear stiffness evolved 19~30 times after 6 hours of reaction time compared with non-treated sands. Also, the cohesion and the friction angle tended to increase and decrease, respectively, as the amount of induced carbonate increased.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.1
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• pp.33-39
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• 2024

Understanding the behavior of soil under cyclic loading conditions is essential for assessing its response to seismic events and potential liquefaction. This study investigates the effect of non-plastic fines content (FC) on excess pore pressure generation in medium-density sand-silt mixtures subjected to strain-controlled cyclic direct simple shear (CDSS) tests. The investigation is conducted by analyzing excess pore pressure (EPP) ratios and the number of cycles to liquefaction (Ncyc-liq) under varying shear strain levels and FC values. The study uses Jumunjin sand and silica silt with FC values ranging from 0% to 40% and shear strain levels of 0.1%, 0.2%, 0.5%, and 1.0%. The findings indicate that the EPP ratio increases rapidly during loading cycles, with higher shear strain levels generating more EPP and requiring fewer cycles to reach liquefaction. At 1.0% and 0.5% shear strain levels, FC has a limited effect on Ncyc-liq. However, at a lower shear strain level of 0.2%, increasing FC from 0 to 10% reduces Ncyc-liq from 42 to 27, and as FC increases further, Ncyc-liq also increases. In summary, this study provides valuable insights into the behavior of soil under cyclic loading conditions. It highlights the significance of shear strain levels and FC values in excess pore pressure generation and liquefaction susceptibility.

• Journal of the Korean Wood Science and Technology
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• v.47 no.4
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• pp.393-407
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• 2019

In this study, we prepared lignocellulosic artificial soil that contains Bacillus subtilis (peat moss/perlite/ steam-exploded oak wood/microbial culture = 3:1:3:3, w/w/w/w) for use in the restoration of damaged soil areas. The prepared lignocellulosic artificial soil was mixed with soil at ratios of 0%, 25%, 50%, 75%, and 100%. These mixed soils were then applied to fields, and the resultant physicochemical properties and their effects on the plant growth of Lespedeza cyrtobotrya were observed. The mixture of the prepared artificial soils (mixed at ratios of 25%-100%) with soil had a bulk densities of <$0.04g/cm^3$, porosities of >85%, pH values between 4.3 and 4.7, electrical conductivities of <0.5 dS/m, C/N ratios between 15.0 and 26.5, organic matter content between 23.6% and 43.2%, and bacterial densities between $157{\times}10^6$ and $624{\times}10^6CFU/g$. In addition, the prepared artificial soils mixed with soil at ratios of 25%-50% exhibited higher plant growth rates for L. cyrtobotrya compared with the control. Overall, we identified positive correlations between the plant growth of L. cyrtobotrya and soil bulk density, porosity, water-holding capacity, C/N ratio, organic matter, and bacterial densities.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.611-619
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• 2018

Basalt powder sludge (abbreviated BPS) is an inevitable industry by product resulted from the stone processing. Recently, demands for natural materials have been increasing in the construction and landscaping fields, therefore, amounts of BPS have been also increasing. Since most of BPS are used as landfill and earth soil, it is necessary to figure out to expedite their utilization. In this study, by considering the characteristics of precipitation of Jeju, effectiveness of BPS as a filler for asphalt compounds mixed with cement were analyzed. As a result, BPS satisfies quality criterion required in KS F 3501. Marshall mixing designs were performed to determine the optimal asphalt content for the Modified recycling asphalt mixture (27% recycling aggregate) and the Normal asphalt mixture. Effectiveness of BPS were identified by the Marshall Stability Test with the mixing ratio (level 3) of two asphalt compounds and composition ration (level 3) of BPS and cement. Performance of asphalt compounds shown appropriate effect of mixing and composition ratios of the filler were assessed. Test results show that two types of asphalt compounds satisfy the quality standards of the MLIT (2015). Therefore, BPS could be used as filler for asphalt compounds.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.1
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• pp.39-46
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• 1999

This study was performed to examine the effect of initial composition ratio and various reaction conditions on CEC and crystallinity of the product in hydrothermal synthesis of zeolitic materials from fly ash. Na-P1 zeolite was formed from the mixture with $SiO_2/Al_2O_3$ ratio above 2.55, however from the mixture with $SiO_2/Al_2O_3$ ratio below 2.25 hydroxy sodalite was formed. The CEC of reaction product(Na-P1 zeolite) treated with 3N-NaOH, $Na_2O/Al_2O_3$ ratio 2.55 and $SiO_2/Al_2O_3$ ratio 2.0 for 12 hours at $103^{\circ}C$ was about $285cmol^+kg^{-1}$, which was higher than those of the products of other reaction condition. The crystallinity of Na-P1 zeolite as high as 45.1% was attained at the optimum reaction condition of 2N-NaOH, $SiO_2/Al_2O_3$ ratio 2.55, $Na_2O/Al_2O_3$ ratio 1.5 for 12 hours at $103^{\circ}C$. The XRD peak of the reaction product could be measured at 7.16, 5.04, 4.12, 3.18, $2.69{\AA}$ and tetragonal pillar shape observed by SEM image be characteristic for Na-P1 zeolite. Judging from the result, it should be considered the optimum synthesis condition for Na-P1 zeolite from fly ash was 2~3N NaOH, $SiO_2/Al_2O_3$ ratio 2.55 and $Na_2O/Al_2O_3$ ratio 1.5~2.0 for 12 hours at $80{\sim}103^{\circ}C$.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.99-103
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• 2009

This research is the result of investigating engineering characteristics of slime generated during construction of deep mixing method. Mechanical characteristics of slime have been studied through literature review and laboratory tests of unconfined compression test, permeability test and settling tests were performed. As result of field observation of slime being generated, slime started to be produced right after flight auger was penetrated into a ground and its amount was increased in progress. Unconfined compressive strength of specimen with slime obtained from in field was measured in the range of $929.7{\sim}3,509.8kN/m^2$ and the value of unconfined compressive strength was found to be changed significantly with mixing ratio of soil, cement and binder. Permeability of them was measured in the range of $4.53{\times}10^{-7}{\sim}6.62{\times}10^{-6}cm/sec$ so that the mixture was appropriate as a impervious barrier. It was also know that the value of permeability was changed with the mixing ratio of binder. As test results of solidifying slime specimen prepared in the laboratory, good quality of cement mixture with coarse soil of sand were produced, compared with fine soils of silt and clay.