• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.15-25
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• 2003

Time Domain Refletometry, or TDR, is a remote sensing electrical measurement technique that has been used for many years to determine the spatial location and nature of various objects, especially in the United States of America and Australia at mining industry. Since early on 1990, the TDR techniques have been applied to the geotechnical engineering such as : deformation measurement of rock slope and landslide, monitoring of ground water content and ground water level change, investigation of ground contamination and its movement. The first application of this technique, in 1996, to the domestic area is to determine the possibility of ground settlement caused by subsidence from abandoned underground mines at the Tongri and Gosari in Gangwon-d. In this paper, through the results of analysed deformation data between conventional measurements and the TDR, it was concluded that the TDR technique is a useful instrumentation method for the prediction of ground deformation.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.463-472
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• 2009

Many old domestic mines were excavated with the room and pillar method or the sublevel caving method and they involve the great possibility of surface subsidence, especially in the shallow depth mines. In most of these cases, the mine roadways and openings are very irregular in shape and the information about the local geology is uncertain. Consequently it is not simple to standardize the estimation method for the possibility of subsidence, especially the sinkhole subsidence. In this study, the fuzzy reasoning method has been applied for development of estimating the possibility of subsidence occurrence in abandoned mine area. This method has the advantage in producing the reliable estimation results with a simple performance procedure even when the precise information on the local geology and mining conditions is rare. For the verification of applicability of this method, the developed method has been applied to Kumho mine in Bonghwa, Kyungbook province and the Choong-ju mine in Iryu, Choongbook province where the surface subsidence occurred already.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.3
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• pp.543-560
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• 2018

With the increased development in downtown underground space facilities that vertically cross under a railway at a shallow depth, the demand for non-open cut method is increasing. However, most construction sites still adopt the pipe roof method, where medium and large diameter steel pipes are pressed in to form a roof, enabling excavation of the inside space. Among the many factors that influence the loosening region and loads that occur while pressing in steel pipes, the size of the pipe has the largest impact, and this factor may correspond to the magnitude of load applied to the underground structure inside the steel pipe roof. The super equilibrium method (SEM) has been developed to minimize ground disturbance and loosening load, and uses small diameter pipes of approximately 114 mm instead of conventional medium and large diameter pipes. This small diameter steel pipe is called an SEM pile. After SEM piles are pressed in and the grouting reinforcement is constructed, a crossing structure is pressed in by using a hydraulic jack without ground subsidence or heaving. The SEM pile, which plays the role of timbering, is a fore-poling pile of approximately 5 m length that prevents ground collapse and supports surface load during excavation of toe part. The loosening region should be adequately calculated to estimate the spacing and construction length of the piles and stiffness of members. In this paper, we conducted a comparative analysis of calculations of loosening load that occurs during the press-in of SEM pile to obtain an optimal design of SEM. We analyzed the influence of factors in main theoretical and empirical formulas applied for calculating loosening regions, and carried out FEM analysis to see an appropriate loosening load to the SEM pile. In order to estimate the soil loosening caused by actual SEM-pile indentation and excavation, a steel pipe indentation reduction model test was conducted. Soil subsidence and soil loosening were investigated quantitatively according to soil/steel pipe (H/D).

• Tunnel and Underground Space
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• v.22 no.6
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• pp.383-392
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• 2012

This study introduces $M_{(i,j,k)}BCP$ (Mining Business Continuity Planning) which is the smart management system of mine disasters to achieve the safe and eco-friendly mining. Where, 'i' is mine kinds, 'j' is mining processes, and 'k' is risks at process respectively. By specifically setting 'i=1=limestone mine', this study also suggests that $M_{(i,j,k)}BCP$ is the smart management system of limestone mine. Mining risks used in this study were obtained from professional survey and literature review. This study classified these risks by five different mining processes and reduced risk numbers approximately 60 to 26. And they were all allocated into $M_{(i,j,k)}BCP$ and assessed. To do assess risks, this study used four risk indexes which are probability, casualty, facility loss, and discontinuity respectively. By the results of the assessment of risks, results could be four specific groups based on their causes and impacts. In addition, one of the results showed that the most possible risks at limestone mine was the roof-fall and rock-fall in digging process. This result means that $M_{(1,2,1)}BCP$ should be established as a first priority at limestone mine.

• Tunnel and Underground Space
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• v.19 no.4
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• pp.287-303
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• 2009

Rock mass in Baekrokdam at the summit of Hallasan in Jeju island is composed of two volcanic rock types: Baekrokdam trachybasalt at the eastern region and Hallasan trachyte at the western region. On-going rockfall and subsequent collapse of Baekrokdam wall rock are closely linked to the weathering of trachyte distributed in the western region of Baekrokdam. Samples of Hallasan trachyte showing different weathering grades had been collected and the polarizing microscopic observation, X-ray diffraction analysis and analysis for chemical weathering had been conducted. Formation of secondary minerals, especially clay minerals, by chemical weathering has not been identified, but the change of chemical weathering indices indicated that chemical weathering process had been proceeded to the degree for increasing and decreasing the contents of some chemical components. Changes in physical and mechanical rock properties due to weathering has also been examined. Artificial weathering test of freezing-thawing reveals that the process of crack initiation and propagation deteriorated the mechanical characteristics of Hallasan trachyte and $D_B$ = 1.5 or porosity = $20{\sim}21%$ would be the ultimate limiting value induced by the mechanical weathering processes.

• Tunnel and Underground Space
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• v.33 no.5
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• pp.388-398
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• 2023

The changes in groundwater flow due to mining development act as a contributing factor to major issues such as ground subsidence, strength reduction and collapse. For the sustainable mining development, measures for dealing with fluctuations in seasonal underground water inflow, power losses, pump damage, and unexpected increases in inflow must be put in place. In this study, the aim is to identify the causes of underground seepage through the examination of hydrological connectivity between the study area and nearby limestone mine. A tracer tes for assessing subsurface connectivity has been planned. A variety of tracers, such as dyes and ions, were applied in lab test to select the optimal tracer material, and a hydrological model of the study area was implemented through field test. Finally, the hydrological connectivity between the external stream and underground water in the mine was analyzed.