• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.3
• /
• pp.118-125
• /
• 2011

The size and distribution of concrete void was one among the factor determining durability of concrete. Recently, there was a lot of researches related to the High-Fludity Concrete(HFC) with field applications. However, the research about the void structure having an effect on durability of concrete is insufficient. Therefore, in this research, Conventional Concrete(CC) and HFC using lime stone powder and fly-ash of 30 MPa range was manufactured and observed the void structure of CC and HFC. Experimental results showed that average pore diameter in the case of the 30 MPa range HFC was to be lower than CC and SEM analyzed result, HFC was firmer inner structure than CC.

• Tunnel and Underground Space
• /
• v.10 no.1
• /
• pp.80-91
• /
• 2000

Open cut mining of limestone is generally considered to be more advantageous than underground mining in recovery, grade control, economics, and safety, but it causes substantial environmental pollutants such as ground vibration, noise, dust. It also changes ground surface and may destroy vegetation. The Halla limestone mine which lies adjacent to Baikdu mountains range is selected for a model study. To reduce environmental hazards, and to conserve original surface and woods, both open cut and underground mining methods must be adopted. In case of sub-level sloping. a unit block of 87m high, 70m wide, and 100∼l20m long is suggested with an estimated overall recovery of 42%. Some suggestions to reduce the environmental hazards are also included. The followings must be considered in determining the degree of fragmentation; the discontinuity conditions in the rock mass and the charge concentration both at the bottom and column of the hole. In addition to adopting a barrier wall for reducing environmental hazards, the probable production from underground mining is also discussed.

• Journal of the Mineralogical Society of Korea
• /
• v.7 no.1
• /
• pp.1-13
• /
• 1994

The industrial minerals play an important role in mining sector. More than 70 % of total mineral production come from industrial mineral sector. This paper reviews geological occurrence of kaolin, pyrophyllite and limestone, and current demand-supply status of major industrial minerals in the Republic of Korea. The kaolin is mainly distributed in the Kyeongsang province, formed by deep weathering of Precambrian anorthosite on mountainside of gentle slope. The pyrophyllite mainly occurs in the Kyeongsang and Chulla provinces, formed by hydrothermal alteration of late Cretaceous andesitic and rhyolitic rocks. Pyrophyllite comprises massive and lenticular bodies and contains minor amounts of kaolin, alunite and pyrite, in some places andalusite and illite. The limestone(Great Limestone Series of Cambrian age) is distributed widely in the Kwangwon and Chungcheong provinces. The limestone bodies are approzimately 70 km long and 3 km wide, elongated NE-ward, and show high grade of CaO content. In 1992, the self-sufficiency ratio of 44 nonfuel (metallic and non-metallic) minerals was no more than 30 percent. However, the ratio of 27 industrial minerals (non-metallic) represents high value of about 72 percent. The export/productjon ratio of the industrial minerals shows decreasing patterns from 12.2 % in 1983 to 4.2 % in 1992. Also the import/production ratio shows rapidly decreasing pattern from 84 % in 1983 to 38.2 % in 1992.

• Resources Recycling
• /
• v.19 no.2
• /
• pp.54-62
• /
• 2010

In order to obtain the basic data for recycling of coal mine tailings, the characteristics of coal mine tailings, the formation of AMD from the tailings and the leaching of heavy metal from the tailings were studied. The samples were characterized in terms of chemical composition, mineral composition and content of heavy metal of the tailings were investigated. The effects of time, temperature, content of pyrite, sulfide minerals on the formation of AMD were also investigated. For the leaching tests, the KS method, TCLP method and column test were used. From the investigated data, we can see that the coal mine tailings can be used as aggregate for filling used gallery. We can also see that the formation of AMD from coal mine tailings can be prevented by mixing 4% or more limestone with it.

• Tunnel and Underground Space
• /
• v.26 no.4
• /
• pp.274-282
• /
• 2016

Natural ventilation is employed in limestone mines that have been currently operated in Korea, and there has been a growing issue of a significantly weak airflow caused by the large-scale excavation. Thus, the air quality in the working area is considerably poor. In order to improve this circumstance, it is mainly required to examine ventilation performance. In this study, the examination of ventilation efficiency was conducted by using tracer gas method. The result of this work indicated detailedly the ventilation problems in research mine, in that extremely low air velocity, recirculation, and air change rate were evaluated quantitatively using tracer gas. Therefore the ventilation performance evaluation using tracer gas can be opted as a precise method to improve the working area in mines.

• Tunnel and Underground Space
• /
• v.28 no.5
• /
• pp.457-475
• /
• 2018

For increase of reality in numerical analysis, a blasting vibration waveform obtained from field blast operations has been directly used for input parameters of dynamic analysis in the form of vibration velocity. A numerical model was built considering the geological characteristics of underground limestone opening as well as the mining stages in this opening, and the effect of blast operations on stability of underground limestone opening was investigated by dynamic numerical analysis. The adequacy of applying the real vibration waveform to dynamic analysis has been approved from the preliminary analysis, and the dynamic numerical analysis results show that the continuous mining operation can cause the collapse of roof in openings and the active yield zone around openings. Therefore, the additional reinforcements should be applied for ensuring the stability of underground limestone openings.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.597-600
• /
• 2008

Correspond in chloride content increase by sea sand uses of bad quality using recycled fine aggregate in this research. together, examined basic properties of matter for activation of been using recycled fine aggregate use definitely. Also, super fundamental principles that is shortcoming that blast furnace slag differential speech has prevents problem of decline and change of countenance limestone power differential speech by purpose to contribute in early age strength as Filler role special quality examine. As experiment result, compressive strength at recycled fine aggregate 10%, limestone power 20% metathesis the highest compressive strength value appear, According to recycled fine aggregate metathesis rate increase, the chloride content reduced by 0.127 ㎏/m$^3$s(metathesis rate 0%), 0.119 ㎏/m$^3$s (metathesis rate 10%), 0.112 ㎏/m$^3$s (metathesis rate l20%), 0.097 ㎏/m$^3$s (metathesis rate 30%).

• Tunnel and Underground Space
• /
• v.27 no.4
• /
• pp.205-216
• /
• 2017

Fluctuations in groundwater level are the major cause of ground subsidence in the abandoned limestone mine. In this study, evaluation of groundwater flow under three different cases of natural condition, aggregate-filling, temporary drainage in groundwater-saturated limestone mine cavities was executed by 3-dimensional analysis. In the case of aggregate-filling, although the water level both in the upper ground of mine cavities and an agricultural watershed was elevated, it was lower than the water level fluctuation of an agricultural water use and rainfall and the flow rate was similar to the flow rate of natural condition. In the case of temporary drainage, as the water level in the upper ground of mine cavities and an agricultural watershed decrease rapidly and the flow rate has increased by 25times, so the risk of ground subsidence increased.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.8 no.2
• /
• pp.23-30
• /
• 2008

UHPC has high performance, high strength and excellent mechanical properties. Moreover UHPC(Ultra High Performance Cementitious Composite) has advantage to reduce cross section under the same load compared with other kinds of concrete. But silica fume which is imported from foreign country has a abundant portion in UHPC mixture in comparison with normal concrete. This is one of the main reason to raise the construction cost. Superior mechanical properties of UHPC due to the optimum filling composition can be changed by replacing the very fine ingredient. The purpose of this research is to grasp the characteristic of UHPC which silica fume and silica flour is replaced with limestone powder. This experiment can be divided into three classes according to the kinds of replacement. The compressive strength and flow of all types were measured and microstructure and hydration phenomena for comparing RPC were analyzed by SEM, XRD, NMR method. As a result, the replacement can be considered to be effective by for the decrease of the UHPC structure construction cost and improvement of the fresh UHPC.

• Analytical Science and Technology
• /
• v.13 no.1
• /
• pp.5-11
• /
• 2000

During the commissioning period in Tonghae thermal power plant which is the largest circulating fluidized bed boiler in the nation, a considerable amount of clinker was formed at FBAC and seal pot. Various attempts, for example, concentration analysis, surface phenomena, thermal characterization, and crystal structure of ash, bed sand, limestone, clinker, and mixture of each gradients have been studied to identify the causes of clinker formed in circulating fluidized bed boiler. As the results, the characterization of black particles in which separated from the clinker is more similar to that of bed sand, on the other hand, white particles are more similar to ash. In addition, the sintering temperature of sand is over $1,200^{\circ}C$ and this temperature was decreased as limestone is added to bed material. The cause of clinker was proved that ash was sticked to molten or sintered sand or limestone in the area of high temperature in the circulating system.