• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.43-51
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• 2014

In the earth structures of railways, large coarse granular materials are widely used as fill materials. However, experimental studies that consider the dynamic properties of these coarse granular materials have rarely been carried out in Korea due to the lack of a large scale test apparatus in this country. In this study, large scale cyclic triaxial tests were carried out for materials such as reinforced roadbed (subballast, graded crushed stone), transition zone gravel, and the upper subgrade of a railway. These specimens were prepared according to certain conditions (dry unit weight, grain size distribution, and so on) specified in the Korea railroad design standard. Based on these large triaxial test results, normalized shear modulus and damping ratio curves according to small strain level are suggested. A model and coefficients for each material are also proposed.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.640-649
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• 2010

Coarse granular materials such as gravel and crushed stone have been used as an important fill materials to large soil structure of railway, road, dam and so on. Although much studies for general soil materials have been carried out domestically, the studies for coarse materials were insufficient. Particularly, it is the level in which the study for dynamic properties(Elastic modulus and damping ratio) of coarse materials, applies the foreign country literature. This is due to the lack of large equipment for element test. But large soil structures made of coarse granular materials are generally important infrastructures. Therefore, the reliable design parameters for coarse materials should be obtained for safe and economic design, construction and maintenance. Triaxial test is the laboratory test method that is capable of controlling a confining pressure and boundary condition. In this project, we made a multi-purpose large triaxial testing system. This testing system is able to test coarse granular materials with maximum particle diameter of 100mm and support both the load control and displacement control. The load cell is installed inside of triaxial cell and the axial displacement is measured locally in order to control and measure more accurately in the small strain level. The verification test of this testing system was carried out with urethane verification specimens. So, from now on the useful information for coarse granular materials are expected to suggested by performing many tests with various material and condition.

• Journal of the Korean GEO-environmental Society
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• v.17 no.3
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• pp.5-12
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• 2016

Stone column is the method that replace soft ground such as weak clay and loose sand with gravel or crushed stone which has relatively high stiffness and low compressive. Stone column increases bearing capacity of the soft ground, reduces settlement, produces ground improvement effect by consolidation drain, and is effective to prevent soil liquefaction in sandy ground during an earthquake. Stone column has been used in many civil works, and has recorded quite a lot of construction achievement internationally, but there is no standardized settlement calculation method yet. Therefore, in this study, the applicability of the existing theoretical equations were evaluated through comparison and analysis to predict a reasonable settlement of the Stone column. Consequently, Hook's law formula was verified to be the most close to numerical analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.211-220
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• 2012

Coarse granular materials such as gravel, rubble is used as major fill materials in earth structures of railway, road and dam. Therefore, it is essential to accurately evaluate properties of these materials for reasonable design and construction. In the precedent study, we built large triaxial testing system and verified system compliance with a focus on the dynamic properties. And we could secured the reliability of the system. In this study, the cyclic triaxial tests were performed in various experimental conditions on coarse granular material. Two series of parallel graded samples are prepared by mixing crushed rock. The influence of grain size, loading pattern, loading frequency, and fine contents were analyzed and discussed.

• Economic and Environmental Geology
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• v.54 no.5
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• pp.581-594
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• 2021

In 2020, about 132 million m³ of aggregate was produced in Korea. Of the total domestic aggregates produced in 2020, about 33.3 % was sand and about 66.7% was gravel. It estimated that of the 132 million m³ of aggregates in Korea in 2020, about 52% was produced by screening crushed aggregate, by 36% by forest aggregate, 3% by land aggregate, 5.6% by sea aggregate and 2.5% by washing each other, and 0.4% by river aggregate. This indicates that screening crushed aggregate and forest aggregate are the main producers of domestic aggregates. Leading producing metropolitan cities were Gyeonggi-do, Gyeongsangnam-do, Chungcheongbuk-do, Gangwon-do, Chungcheongnam-do, Incheon in order decreasing volume, which together accounted for about 72.4% of total product. In 2020, aggregates were produced in 153 cities, about 67% of the 231 cities of Korea, 38 local governments have developed aggregates of more than 1 million m³, and the combined production of the 38 cities accounted for about 65% of national total. This means that the aggregate extraction trend of local governments is becoming larger and more concentrated. In 2020, at 153 local governments, a total of 889 operations produced aggregates with 420 operations by permission, 469 operations by declaration. A review of production by size of operation indicated that about 17 million m³ (12.8% of the total aggregate) was produced by 14 operations reporting production of more than 1 million m³. In about 420 operations, the maximum period of permit is 32 years to at least 2 months. When the remaining period of permit is taken into account, only about 55% of active operations can be developed the aggregate after 2021. In order to maintain the permitted aggregate volume by 2020 level, it will be necessary to obtain an extension permit or find new operation sites for at least 200 or more operations.

• Economic and Environmental Geology
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• v.54 no.5
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• pp.549-560
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• 2021

In 2019, at 147 local governments, a total of 872 operations produced aggregates with 414 operations by permission, 458 operations by declaration except the marine operations. The leading aggregate sources were, in descending order of the number of operations, crushed, forest, land, washing, river aggregate. By aggregate type, gravel-only operations were slightly more than sand-only ones. By province, Gyeongsangbuk-do had 149 operations, followed by Gyeonggi-do with 135, Gangwon-do with 113, and Gyeongsangnam-do with 92, Chungcheongbuk-do with 81, and Jeollabuk-do with 70. A review of production by size of operation indicated that about 23,100 thousand m³ (17.6% of the total aggregate) was produced by 17 operations reporting production of more than 1 million m³, about 29,900 thousand m³ was produced by 44 operations reporting production between 500 and <1,000 thousand m³, about 60,000 thousand m³ was produced by 273 operations reporting production between 100 and <200 thousand m³, about 17,000 thousand m³ was produced by 409 operations reporting production between 10 and <100 thousand m³. 129 operations that producted less than 10 thousand m³ accounted for 0.4% of total aggregate produced in Korea in 2019. Operations that produce more than 1 million m³ of aggregate was only from forest and crushed aggregate. The period of permission for aggregate producing based on permission is mostly less than 10 years, and in particular, for river and land aggregates, the permission period is very short, less than 2 years.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.40-46
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• 2013

Based on Korean railway design standards, the thicknesses of the reinforced roadbeds of conventional and high speed railways are different, and so too, for the size distribution of the ballast particles. Accordingly, considerable cost would be required to increase operating speeds of conventional lines, in particular related to changing from a ballasted track system to a ballastless one. In this study, applicability of a roadbed which supports conventional ballasted track, for use as a ballastless track for a high speed rail line was examined. A reinforced roadbed for a conventional railway is 20cm thick, and the type of material used for a conventional reinforced roadbed is M-40 (crushed gravel for road embankments). A dynamics test was conducted to evaluate the occurrence of the permanent settlement of the track substructure. These results suggest that, without changes to the track substructure, an operational speed of 400km/h is feasible with a ballastless track. This result; however, is from laboratory experiments. Further studies, such as numerical analyses or field validation, are required.

• Journal of Wetlands Research
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• v.18 no.2
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• pp.183-193
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• 2016

In this study, design and performance of infiltration trench using woodchip as media for treating stormwater from highway were examined through field monitoring. Average reduction efficiency for TSS, COD, BOD, TN, and TP was 88%, 94%, 85%, 80%, and 75% respectively, which is similar to values reported by other studies and design manuals even though direct comparison is not possible due to different monitoring and design conditions. Mean field infiltration rate estimated by measuring the change of water depth inside the observation well was about 40mm/hr, and the time taken for complete infiltration was about 0.83days, which corresponds well with design criteria recommended by MOE guidelines in Korea. In addition, according to analysis of infiltration rate and reduction efficiency, effective rainfall depth applied for determining water quality volume(WQv), 5mm was found to be properly established as design criteria. Woodchip must be considered and included as an alternative media together with crushed rock and gravel into the design guidelines because it has more advantages in terms of weight, porosity, cost, and easiness of management than other media materials.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.83-91
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• 2015

Porous concrete consists of cement, water and coarse aggregate and has been used for the purpose of decreasing the earth environmental load such as air and water permeability, sound absorption, etc. However, the physical and mechanical properties of porous concrete changes due to compaction load during construction. For such a reason, the purpose of this study is to investigate the physical and mechanical properties of porous concrete according to the kinds of binder, the ratio of water to binder and target void ratio. In particular, this study has been carried out to investigate the influence of compaction load on the void ratio, strength and coefficient of permeability. Aggregate used in this study are by-products generated during production of crushed gravel with a maximum size of 13mm. The results of this study showed that the target void ratio, the coefficient of permeability and compressive strength of porous concrete had a close relationship with the void ratio, and it will be possible that the void ratio is suggested by the mix design of porous concrete. The compressive strength of porous concrete was the highest at the content of the expansive admixture of 5% and compared to non-mixture, 10% mixture of silica fume improved compressive strength about 32%. And in the result of the study to change the compaction load, the compressive strength increased from the load of 15kN, the void ratio decreased from the load of 0.8kN, the coefficient of permeability decreased from the load 35kN, respectively.

• Korean Journal of Agricultural Science
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• v.32 no.1
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• pp.19-27
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• 2005

This study was performed to evaluate the physical and mechanical properties of polymer concrete using unsaturated polyester resin, initiator, heavy calcium carbonate, crushed gravel, recycled coarse aggregate, silica sand and recycled fine aggregate. The unit weight, compressive strength, flexural strength and dynamic modulus of elasticity were decreased with increasing the content of recycled aggregate. The unit weight, compressive strength, flexural strength and dynamic modulus of elasticity were showed in $2,127{\sim}2,239kg/m^3$, 80.5~88.3MPa, 19.2~21.5MPa and $254{\times}10^2{\sim}288{\times}10^2MPa$ at the curing age 7 days, respectively. Therefore, these recycled aggregate can be used for polymer concrete.