• International Journal of Highway Engineering
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• v.5 no.4 s.18
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• pp.13-22
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• 2003

Several design methods from overseas are employed without considering different conditions such as material properties, climate, and traffic condition in this country. Therefore, there are limitations in application. Therefore, new pavement analysis system which is able to design a pavement efficiently and economically should be set up. In this study, 243 probable sections are classified depending on values of layer thickness and elastic modulus, and the effect of load types for the probable sections are analyzed. The section showing larger load distribution is chosen for analysis. As a result of sensitivity, a layer thickness has more influence on pavement than an elastic modulus does. The stress distribution of FWD test load is larger than that of circular load. This study compares outputs between nonlinear elastic model and linear elastic model. Based on the result, this study finds nonlinear elastic model considering stress condition in the ground is recommended for subbase.

• Journal of the Korean Geotechnical Society
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• v.29 no.9
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• pp.55-69
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• 2013

An alternative design method of existing methods based on elastic theory the design method of roadbed considering plastic deformation of roadbed and stress-strain at roadbed materials with the cyclic loading of trains passing. The characteristics of the developed design method considering traffic load, number of cyclic loading and resilience modulus of roadbed materials can evaluate elastic strain as well as plastic settlement with allowable design criteria. The proposed design method is applied to standard roadbed section drawing of HONAM high-speed railway considering design conditions such as allowable elastic and plastic settlement, train speed, the tonnage of trains. As a result, required levels of resilience modulus model parameter ($A_E$), unconfined compressive strength, types of soil material were evaluated.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.395-403
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• 2007

Railroad track consists of relatively simple structures such as rail, sleeper, ballast. Roadbed shares vertical pressure by train load which passed through rail to ballast as base that supports the track. For evaluating stress and displacement of roadbed due to the railroad load is an important role on the track as a basic data for estimation of the durability and design of the roadbed thickness. GEOTRACK program applied multi-layered theory was developed for analyzing railroad track structure. GEOTRACK program is a sort of numerical analysis program which has advantage that can analysis component of track by simple method. In this study, this program was used to preform the numerical analysis by changing track conditions and roadbed conditions such as tie, reinforced roadbed, dynamic wheel load, Resilient modulus and so on. Further detail will be presented on the paper.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1747-1755
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• 2008

Design of the reinforced roadbed thickness is concerned with safe operation of trains at specified levels of speed, axle load and tonnage. There are two methods for evaluating it. One is using an experimental equation and the other is using elastic theory with considering axle load, material properties of subsoils and allowable elastic settlement. Multi-layered theory is used to determine reinforced roadbed thickness by RTRI. Although their reinforced roadbed thickness is designed with an objective of achieving a minimum standard 2.5mm of settlement on the subgrade surface, it is hardly applied to real design. Li(1994) has suggested the experimental model which design approach is to limit plastic strain and deformations for the design period. It is worth due to adopting soil equivalent number of repeated load application. Moreover, it has been a more advanced method than existing design methods because including resilient modulus of subsoil beneath track, soil deviator stress caused by train axle loads and MGT. In this paper, it is analyzed under domestic track conditions to estimate the reinforced roadbed thickness with different soil types.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.107-112
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• 1990

Chromatograms of asphalt cements were observed using high pressure - gel permeation chromatography (HP-GPC). The chromatogram characterzed profile of molecular size distribution of asphalt cements. Bituminous concretes using the asphalt cements were prepared in laboratory to measure mechanical properties, tensile strength (TS) and resilient modulus (MR), in dry and wet conditions. Three sources of AC-20 Asphalt cements and one aggregates were used for GPC test and strength test. Results of mechanical property tests and GPC tests were analyzed to evaluate correlation between those two results. Regression analysis showed strong correlation between a mechanical property and sliced percent areas of GPC profile. Mathematical models were developed for estimating mechanical properties of asphalt cement concrete based on HP-GPC data.

• International Journal of Highway Engineering
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• v.1 no.2
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• pp.135-154
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• 1999

Compaction of asphalt pavement is one of the important processes to make good quality one. There are many laboratory-compaction methods to simulate field compaction, including Marshall compaction, Hveem compaction, gyratory compaction, and etc. The most common method used to determine the fundamental properties of asphalt mixture for design is Marshall method which is using impact energy. However, there is major difference between field compaction using kneading compaction and Marshall compaction using impact energy. Therefore, the gyratory compactor, which currently is the best to simulate the field compaction, was employed. The fundamental properties of asphalt specimen compacted by gyratory compactor and Marshall compactor were determined using laboratory test. From the tests, slag mixture with carbon black or pyrolyzed carbon black showed better performances, such as, in low susceptibility to temperature, high resistance against water and rutting, and high resilient modulus and indirect tensile strength.

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.69-76
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• 2005

While the repeated traffic loading accumulates the damage of asphalt pavement, the damage has being healed during rest periods. And then, this healing enhances the fatigue life of asphalt pavement. A method was developed to determine the healing rate of asphalt mixture in terms of recovered dissipated creep strain energy (DCSE) per unit time, and the healing properties of four different asphalt mixtures were evaluated. The test procedure consists of repeated loading test and periodical resilient modulus tests. A normalized healing rate in terms of $DCSE/DCSE_{applied}$ was defined to evaluate the healing properties independently of the amount of damage incurred in the mixture. From the test results, it was concluded that the healing rates of asphalt mixtures were increased exponentially as the temperature was increased and more affected by the structural characteristics of mixture such as asphalt content than the binder characteristics such as the polymer modification.

• International Journal of Highway Engineering
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• v.4 no.1 s.11
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• pp.149-159
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• 2002

This study was performed to estimate the high-speed direct tensile strength(DTS1), low-speed direct tensile strength(DTS2) , indirect tensile strength(ITS) resilient modulus(MR) and stiffness index(SI) of sand asphalt mixture based on the absolute viscosity, kinematic viscosity, penetration, softening point and PG grade of binder. DTS2 showed higher correlation with the physical properties than other properties of mixture, and the next was DTS1, ITS, SI and MR in order. Among binder properties, PG grade showed the highest relation with DTS2. Therefore. it was found that the high DTS mixture could be made when the binder with a high PG grade was used. However, since the individual physical property showed a relatively low correlation, various properties were used together in regression analysis. The estimation models of DTS and ITS were over 0.99, respectively. R2 of MR and SI estimation models were over 0.91 and 0.93, respectively. It was concluded that mechanical properties could be estimated with a high coefficient of determination from those physical properties.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.41-52
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• 2008

This study is to evaluate the property for the moisture susceptibility of asphalt mixtures using anti-stripping agent. Asphalt mixtures using lime, hydrated lime and liquid anti-stripping agent are evaluated through the three types of modified moisture conditioning($H_c$, V_s$, F-T). Indirect Tensile Test, that is recommended by AASHTO TP-9, which includes creep test, resilient modulus test and strength test is used to estimate moisture susceptibility. Analysis method through Energy Ratio(ER) that is proposed by Roque at University of Florida is used to evaluate moisture susceptibility and moisture resistance effects of asphalt mixtures using anti-stripping agent. As a test result, material property of asphalt mixtures was changed by moisture conditioning methods and the types of anti-stripping agent. Also, cracking resistance of accumulated moisture damage was changed by moisture conditioning methods and the types of anti-stripping agent. Based on test result, it was found that cracking resistance using Energy Ratio was differed from 10% to 30%.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.75-83
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• 2004

The Indiana Department of Transportation (INDOT) has permitted the use of Lime Kiln Dust (LKD) as a low-cost construction material in creating a workable platform for soil modification (not for soil stabilization) since the early 1990s on selected projects. However, the enhanced strength of soils with LKD has not been accounted for in the subgrade stability calculations in the design process. This study was initiated to evaluate how the lime kiln dust is a comparable material to hydrated lime. A series of laboratory tests were performed to assess the mechanical benefits of lime kiln dust in combination with various predominant fine grained soils encountered in the State of Indiana, such as A-4, A-6 and A-7-6. In the course of this study, several tests such as the Atterberg limits, standard Proctor, unconfined compression, CBR, volume stability, and resilient modulus were performed. As a result, mixtures of fine grained soils with 5% lime or 5% LKD substantially improve unconfined compressive strength up to 60% - 400%. CBR values for treated soils are in the range of 25 to 70 while those for untreated soils range from 3 to 18. In general, significant increase in resilient moduli of the soils treated with lime and LKD was observed. This indicates that lime kiln dust may be a viable, cost effective alternative to hydrated lime in enhancing the strength of fine grained soils.