• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.35-44
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• 2017

A large amount of recycled aggregates was produced and crushed from old buildings and pavements. In this study, when these aggregates are re-used in subbase or subgrade materials in near construction sites, their engineering characteristics caused by crushing are investigated in terms of permeability and shear strength. Three different sizes of aggregates (31.5-45.0 mm, 19.0-31.5 mm, 9.5-19.0 mm) and their mixtures, a total of 7 types of aggregates were used in compaction tests (modified D and B methods). After compaction tests, aggregates were sieved and analyzed with four different breakage factors ($B_{15}$, $C_c$, $B_{10}$, $B_r$). The D compaction method gave 2.0-8.0 times more crushable than B compaction method. The breakage factors for the largest size aggregate was 1.4-3.0 times higher than those of the smallest size aggregate. For aggregates with 5.6-9.5 mm sizes, the samples were prepared with $B_{15}$ of 1, 3, 10, 20, 30, 50, 60, and 70 for permeability and direct shear tests. As $B_{15}$ increased, the hydraulic conductivity decreased up to 1/22 for $B_{15}=50$. As $B_{15}$ increased from 1 to 50, the peak friction angle increased from $46.1^{\circ}$ to $54.5^{\circ}$. On the other hand, the friction angle decreased after $B_{15}=60$.

• International Journal of Highway Engineering
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• v.6 no.3 s.21
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• pp.55-64
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• 2004

Maximum dry unit weight, ${\gamma}_{dmax}$, is the most important engineering properties for subgrade soil. Existing models to predict ${\gamma}_{dmax}$ containing many parameters, seem to be rather complex. This paper presents new simple models to predict ${\gamma}_{dmax}$. for sandy soils, A number of sieve analysis and compaction tests for 36 types of sands were conducted to develop the regression-based models. Parameters used to estimate ${\gamma}_{dmax}$ are both the geometric mean and geometric standard deviation of the soils, or the particle-size distribution curve parameters. Maximum dry unit weights predicted by the models are in good agreement with the laboratory measurements for the soil samples obtained at 16 locations within the Korea.

• Journal of Wetlands Research
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• v.19 no.3
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• pp.359-365
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• 2017

Impermeable surfaces such as transportation land uses including roads and parking lots accumulate high heavy metals and particulate matters concentration especially during dry season which worsens the river water quality and distort the water circulation system during rainfall events. Recently, the government has been promoting policies to install Low Impact Development (LID) facilities such as permeable pavements or grass blocks in parking lots or pavements. However, transition of asphalt-paved surfaces to permeable pavement generated asphalt wastes which are detrimental to the environment and has cost implications due to its removal and disposal. Therefore this study was conducted to provide a method of constructing a cost-effective permeable pavement to reduce waste generation and cost. In this study, comparative analysis of the water circulation capacity and economic efficiency of the traditional construction method and new method proposed in this study through the lab-scale experiment. The proposed method was to make holes in existing asphalt pavements, layout geotextile fabric and permeable base media such as sand before compaction. After compaction, layout grass blocks on the compacted base media then layout sand in between each grass blocks before compaction. Apparently, there was no significant difference between the traditional installation method of permeable pavement and the proposed method in this study considering surface runoff, infiltrated volume, stored volume, and rainfall-runoff delay time. The proposed method in this study generated 86% less wastes compared to the traditional installation method and has 70% cost reduction considering asphalt removal and disposal. The construction method proposed in this study yielded similar performance compared to the traditional installation method and water circulation effect, but was proven to be less complicated and economical.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.173-178
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• 1993

The most appropriate mixing ratio of fly ash to bottom ash obtained from compaction characteristics and CBR values is varying from 5:5 to 6:4. But these mixed ashes are frost-susceptible materials according to judging by the paticle-size distribution because of a lot of silty-size paticles. In this study, the frost-susceptibility of compacted coal ash with proper mixing ratio is examined experimentally for use of subgrade materials. And, the efforts have been made to find proper cement addition in making these mixed ashes frost-insusceptible. It was revealed that these mixed ashes are frost-susceptible, and 4% of cement content is required to be made frost-insusceptable. It was found that amount of frost heave of these mixed ashes decreases with the unconfined compressive strength, and increases with log k if the permeability coefficient k is as low as the water into the freezing front of these mixed ashes is restricted.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.207-213
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• 1992

In this study, the strength and durability of compacted coal ash with proper mixing ratio of fly ash to bottom ash, such as 5:5 or 6:4, are examined for use of highway embankment and subgrade materials. Right after compaction, the strength of bituminous mixed coal ash is greater than that of anthracite mixed coal ash. The distinguished increase of strength with curing time is observed only in Ho-nam mixed coal ash that contains a lot of free lime, and the strength increase with curing time are not seen or little in the others. The durability in sinking test is good also in Ho-nam mixed coal ash, but satisfactory by adding 2% cement in the others. And it is seen that the effects of the strength increase with adding cement are greater in coal ash with proper mixing ratio than in fly ash or bottom ash respectly.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.357-364
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• 2002

This paper describes the feasibility of compacting subgrade layer in thicker lifts than currently permitted as 20 cm. This project involved constructing and testing a full scale test section in highway. Soil stiffness in field was evaluated by a nondestructive testing method, called Geogage. Quality control tests and FE Analysis were also conducted. Typical dynamic compaction roller of 11ton weight is applied for full scale test and a Mohr-Coulomb model and Plane strain condition are used for FE Analysis. The results showed that compaction-induced stress and dissipated energy are mainly depend on depth of soil and it could be possible to increase thickness of a lift.

• Journal of the Korean Geotechnical Society
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• v.31 no.3
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• pp.63-72
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• 2015

This paper describes the correlation and relationship between elastic moduli measured by three stiffness measurement methods with different mechanical characteristics to evaluate the compaction characteristics of subgrade soils. The Soil Stiffness Gauge (SSG) with very small strain (${\approx}0.001%$) ranges, static Plate Loading Test (PLT) with mid-level strain (${\approx}0.01{\sim}0.1%$) ranges, and Dynamic Cone Penetrometer (DCP) using penetration resistance were implemented to measure the elastic modulus. To use the elastic modulus measured by different measurement methods with a wide range of strain in practice, it is required to identify the correlation and relationship of measured values in advance. The comparison results of the measured elastic moduli ($E_{SSG}$, $E_{PLT}$, $E_{DCP}$) using the three measurement methods for domestic and overseas subgrade soils under various conditions indicate that the evaluated elastic modulus relies on the types of soils and the level of stress condition. The correlation analysis of the measured elastic moduli except the data of cement treated soils indicates that the static elastic modulus ($E_{PLT}$) is evaluated as about 60 to 80% of the dynamic elastic modulus ($E_{SSG}$). Unusual soils such as cement treated soils are required to be corrected by the stress correction during the correlation analysis with typical soils, because these types of soils are sensitive to the stress condition when measuring the static elastic modulus ($E_{PLT}$) of soils. In addition, when considering the use of DCP data for the evaluation of the elastic modulus ($E_{DCP}$), the measured data of the elastic modulus less than 200 MPa show more reliable correlation.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.19-25
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• 2009

The current study developed light-weighted mixed soil that can solve problems related with soft soil such as ground subsidence, sliding and lateral displacement of ground. By reducing weight of reclaimed soil through mixing phosphogypsum and recycled EPS beads with the weathered granite soil. A series of geotechnical laboratory tests including physical index test, compaction test, CBR test, and direct shear test were performed and engineering properties were reviewed in order to assess applicability of the light-weighted mixed soil for roads and abutment and various back-filling materials at the reclamation area. Based on the laboratory test results, it was found that the maximum dry unit weight of the light-weighted soil ranges $14.32{\sim}15.79kN/m^3$ and the optimum water content ranges 21.91~24.23%, which means there is 11~19.3% weight decrease effect when comparing with general weathered granite soil. Also it was found that the corrected CBR value ranges 10.4~18.4% satisfying the domestic regulations on road subgrade and back-filling material. In addition, as for shear strength parameter, cohesion ranges 10.79~18.64 kPa and internal frictional angle ranges $35.4{\sim}37.2^{\circ}$, which are similar with those of general construction soil and back-filling material used in Korea. So it can be concluded that light-weighted mixed soil with phosphogypsum can be used effectively for soft reclamation ground as actual filling material and back-filling material. From the current study, it was found that light-weighted mixed soil with phosphogypsum has not only weight reduction effect, but also has no special problems in shear strength and bearing capacity. Therefore, it is expected that phosphogypsum can be recycled in bulk as road subgrade and back-filling material at the reclamation area.

• Geotechnical Engineering
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• v.7 no.4
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• pp.25-34
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• 1991

In this study, relationships between CBR values tested by Korean Standards (KS CBR) and the elastic moduli from CU compression tests are developed for the subgrade soils. Triaxial compression and KS CBR tests are carried out on five types of samples from 15 points in Korean ezpressways. Triaxial compression tests are performed under 3 types of coifining pressures to generalize the CBR -elastic modulus relationship as functions of confining pressured and mean principal stresses. From the regression analyses of experimental results, equations for relationships between the KS CBR and elastic moduli of roadbed Boils are proposed. An equation for the relation- ship between the KS CBR and the maximum dry density of roadbed soil is also proposed.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.2
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• pp.23-30
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• 2010

The research presents moisture content measuring and calibration method of road pavement, especially asphalt concrete pavement for performance evaluation or remaining life prediction using Time Domain Reflectometry(TDR) sensor, CS616 made by campbell INC. Before calibration test of CS616, accomplished a sensor verification tests. Verification test items were covering depth and interference effect of two CS616 sensors, temperature effects between $5^{\circ}C\sim25^{\circ}C$ and compaction ratio effects. Covering depth and interference effects between two CS616 sensors were just small and the effects of temperature and compaction ratio effected a Volumetric Moisture Contents at $\pm6%$ under disregard appeared with the fact that was possible. Also, obtained the calibration equation of the subgrade and subbase course, $R^2$ showed above of all 0.9.