• The Journal of Engineering Geology
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• v.20 no.4
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• pp.425-436
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• 2010

We established a stochastic 3-D fracture network system for fractured rock masses located in Il-Gwang Mine, Busan, to explore the relationship between the acidity of mine drainage and fracture geometry. A field scanline survey and borehole image processing were performed to estimate the best probability distributions of fracture geometry parameters. The stochastic 3-D fracture network system constructed for the rock masses was validated and deemed to be successful. The 3-D fracture network model was suitable for developing conceptual ideas on fluid flow in fractures at a field experimental site. An injection well and three observation wells were drilled at the field experimental site to monitor the acidity of mine drainage induced by the injection of fresh water. The field experiment, which was run for 29 days, yielded a significant relationship (with a high coefficient of determination) between the fracture geometry parameters and the acidity of mine drainage. The results show that pH increased with increasing relative frequency of fracture strike, and decreased with increasing fracture density. The concentration of $SO^{2-}_4$ decreased with increasing relative frequency of fracture strike, and increased with increasing fracture density.

• The Journal of Engineering Geology
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• v.20 no.2
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• pp.121-126
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• 2010

Current technology for radioactive waste disposal facility is operated as part of KURT site characterization in terms of reliability assessment is conducted to expand. In this study, a geological model of KURT surrounding area on the basis of flow characteristics of the site-scale hydrogeological study was about. Distributed in the study area into four boreholes were plotted using the stereo net NS, NW, EW, Low-angle fracture group was able to identify the components of geological models and include top soil layer, belt of weathering, Low-angle fracture zone, fracture zone was divided into. Separated by fracture of the hydraulic test of through the groundwater aquifer that provides the flow hydraulic conductivity and insulation hydraulic affecting the slope of the normal distribution for the size and direction by performing statistical analysis of fracture in the direction of local ns The advantage was confirmed. In addition, Low-angle fracture hydraulic conductivity of the value of 3.61e-07 m/s has a value greater than the major fracture, the fracture zones exist in the base rock and base rock and the hydraulic characteristics of the different methods applied and had to have a different interpretation judged by was.

• Journal of Korean Society of Rural Planning
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• v.15 no.2
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• pp.81-96
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• 2009

This study has found out the status of the environment ecology(topography structure. land-use, flora, plant community structure, wildbird) in 10 uninhabited islands(i.e. Kei island, Hadon island, Sangdon island, Daewa island, Hwanggang island, Naebi island, Oebi island, Prickly castor-oil tree island, Tongin island, Yuk island), Namhae-gun, Gyeongsangnam-do. Moreover, It has suggested ways of improving the environment ecology status by classifying the type of environment ecology about the degree of use and damage that based on the results of environment ecology survey. According to the results of topography structure survey, the survey site altitude was ranged within 1m$\sim$25m, otherwise, the radient was classified the rock area(.i.e. slope of less than $5^{\circ}$ the dead level) and the slope area where is steep slope. Moreover, there was showed evenly a variety of aspect. Land-use were divided the field(Kei island), dry native grasslands(Hadon island), naturalized grasslands(Sangdon island), Pinus thunbergii community(Dacwa island, Hwanggang island, Naebi island, Yuk island), the rock area(Oebi island, Prickly castor-oil tree island, Tongin island). As the results of flora survey, the number of plant species were 30$\sim$115 species and the naturalized species were found 2$\sim$12 species in each site. The results of plant community structure analysis, The dominant species were Pinus thunbergii and Pinus densiflora were in upper tree layer, furthermore, it were Pinus thunbergii, Eurya japonica, Prunus sargentii, Celtis sinensis, Morus bombycis, ect. in cannopy tree layer. In shrub layer, the dominant species were Rosa multiflora, Rubus crataegifolius, Parthenocissus tricuspidata, etc. The status of wildbird bird, had been found 42 species 938 individuals, especially, there were Bubo bubo kiautschensis(natural monument No. 324) and Haematopus ostralegus osculans(natural monument No. 326). According to these synthetic results, we are able to classify the 5 types of environment ecology such as the natural coast forest that composed of Pinus thunbergii and Pinus densiflora(Daewa island, Hwanggang island, Naebi island, Oebi island, Tongin island, Yuk island), the field in vegetation area(Kei island), vegetation succession area of fallow field type(Hadon island), vegetation damage area by the forest fire and disturbance elements(Prickly castor-oil tree island), dominant naturalized species grassland by grazing cattle(Sangdon island).

• Journal of the Mineralogical Society of Korea
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• v.28 no.3
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• pp.209-220
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• 2015

The aim of this study was leaching valuable metal ions from mine waste rocks which were abandoned mine site using indigenous aerobic bacteria. In order to tolerate the the indigenous aerobic bacteria to the heavy metal ions they were repeatedly adapted in $CuSO_4{\cdot}5H_2O$ environment. As the repeated generation-adaptation progressed, the pH values of the growth-medium were gradually decreased. During bio-leaching experiments with indigenous aerobic bacteria raised in a heavy metal ion environment for 42 days, the pH of the leaching solution was decreased while increasing the adaptation period. The indigeous bacteria were much more active on the surface of Younhwa waste rocks which contained relatively few the chalcopyrite and Cu content than the Goseong mine waste rocks, and also the amount of Cu and Fe ions were leached more in the Younhwa sample(leaching rate of 92.79% and 55.88%, respectively) than the Goseong sample(leaching rate of 66.77% and 21.83%, respectively). Accordingly, it is confirmed that valuable metal ions can be leached from the mine waste rocks, if any indigenous bacteria which inhabits a mine environment site for a long time with heavy metal ions can be used, and these bacteria can be progressively adapted in the growth-solutions containing the target heavy metals.

• Tunnel and Underground Space
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• v.26 no.1
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• pp.24-31
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• 2016

Recently, many studies have been conducted to use fixed-wing and rotary-wing unmanned aerial vehicles (UAVs, Drones) for topographic surveying in open-pit mines. Because the fixed-wing and rotary-wing UAVs have different characteristics such as flight height, speed, time and performance of mounted cameras, their results of topographic surveying at a same site need to be compared. This study selected a construction site in Yangsan-si, Gyeongsangnam-do, Korea as a study area and compared the topographic surveying results from a fixed-wing UAV (SenseFly eBee) and a popular rotary-wing UAV (DJI Phantom2 Vision+). As results of data processing for aerial photos taken from eBee and Phantom2 Vision+, orthomosaic images and digital surface models with about 4 cm grid spacing could be generated. Comparisons of the X, Y, Z-coordinates of 7 ground control points measured by differential global positioning system and those determined by eBee and Phantom2 Vision+ revealed that the root mean squared errors of X, Y, Z-coordinates were around 10 cm, respectively.

• Tunnel and Underground Space
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• v.29 no.6
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• pp.480-507
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• 2019

This paper aims at optimizing the auxiliary ventilation system in large-opening limestone mines with unducted fans. An extensive CFD and also site study were carried out for optimization at the blind entries. The fan location, operating mode, and layout are the parameters for optimization. Since the jet stream discharged from the auxiliary fan is flowing faster than 15 m/s in most of the cases, the stream collides with floor, sides or roof and even with the jet stream generated from the other fan placed upstream. Then, it is likely to lose a large portion of its inertial force and then its ventilation efficiency drops considerably. Therefore, the optimal fan installation interval is defined in this study as an interval that maximizes the uninterrupted flowing distance of the jet stream, while the cross-sectional installation location can be optimized to minimize the energy loss due to possible collision with the entry sides. Consequently, the optimization of the fan location will improve ventilation efficiency and subsequently the energy cost. A number of different three-dimensional computational domains representing a full-scale underground space were developed for the CFD study. The velocity profiles and the CO concentrations were studied to design and optimize the auxiliary ventilation system without duct and at the same time mine site experiments were carried out for comparison purposes. The ultimate goal is to optimize the auxiliary ventilation system without tubing to provide a reliable, low-cost and efficient solution to maintain the clean and safe work environment in local large-opening underground limestone mines.

• Tunnel and Underground Space
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• v.29 no.6
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• pp.532-541
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• 2019

Even though shotcrete is a main support for securing the stability of tunnel, the performance of shotcrete is not properly checked due to various difficulties arisen from the characteristics of materials themselves which constitute shotcrete, such as steel fibers and accelerators, and the on-site quality control. In this study, the actual conditions of shotcrete applied to expressway tunnel construction sites were tried to find out, and then some improvement was tried to derive. For this purpose, the characteristics of steel fibers and accelerators supplied to the expressway construction sites were investigated. Also, shotcrete specimens were prepared at the tunnel sites and performance tests were carried out. For steel fiber, domestic production states were investigated, and carbon content and tensile strength were measured using the steel fibers collected in the construction sites. For three types of accelerators such as aluminate, cement mineral and alkali-free, basic properties and total amount of alkali contents were analyzed. Shotcrete specimens were prepared using on-site shotcrete machine with regard to mix designs and types of accelerators. Using these specimens, uniaxial compression tests and flexural tests were performed. As the results, compressive strength, flexural strength, flexural toughness, and etc. were compared with types of acclerators and mix designs.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.38-58
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• 2018

The ventilation system plays a crucial role in underground mine safety. The main objective of the ventilation system is to supply sufficient air to dilute the contaminated air at working places and consequently provide tenable environment during the normal operation, while it also should be capable of controlling the fire propagation and facilitate rescue conditions in case of fire in mines. In this study, a smoke control fan was developed for the auxiliary ventilation as well as the fire smoke exhaust. It works as a free-standing auxiliary fan without tubing to dilute or exhaust the contaminated air from the working places. At the same time, it can be employed to extract the fire smoke. This paper aims to examine the smoke control efficiency of the fan when combined with the current ventilation system in mines. A series of the site experiments and numerical simulations were made to evaluate the fan performance in blind entry development sites. The tracer gas method with SF6 was applied to investigate the contaminant behavior at the study sites. The results of the site study at a large-opening limestone mine were compared with the CFD analysis results with respect to the airflow pattern and the gas concentration. This study shows that in blind development entry, the most polluted and risky place, the smoke fan can exhaust toxic gases or fire smoke effectively if it is properly combined with an additional common auxiliary fan. The venturi effect for smoke exhaust from the blind entry was also observed by the numerical analysis. The overall smoke control efficiency was found to be dependent on the fan location and operating method.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.603-615
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• 2020

The design factors of artificial recharge are determined by considering the hydrogeological characteristics of the aquifer. The optimal design factors for artificial recharge were derived after performing the injection tests step by step for each injection type (vertical well, ditch and mixed type), which were built in the test site of the study area. It was analyzed that the difference in the injection effect according to the diameter of the injection well was not large, and the 100 mm well was evaluated as appropriate in consideration of the availability and economy of land use. Since the injection effect was well maintained even in the upper rock, the depth of the injection well was proposed for the alluvial layer and the upper rock layer. On the other hand, in four cases of filter media in the ditch, it was analyzed that the penetration efficiency and the hydraulic interference effect indicated excellent injection performance when a filter medium of 10 to 30 mm diameter was filled in the ditch. In addition, the proper spacing of the injection wells was analyzed as 9~12 m considering the interference efficiency. The interference efficiency attenuation coefficient per 1 m of hole spacing was calculated to be 1.75% in this area. In the future study, the artificial recharge design factors obtained in this stage are applied and verified on site construction and operation. Also it is expected to contribute to securing water in areas where there is always a lack of water.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.675-686
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• 2021

This study investigated the ground displacement occurring in a slope below a waste-rock dumping site and estimated the likelihood of a disaster due to a landslide. To start with, photogrammetry was conducted by unmanned aerial vehicles (UAVs) to investigate the size and extent of the ground displacement. From April 2019 to July 2020, the average error rate of the five UAV surveys was 0.011-0.034 m, and an elevation change of 2.97 m occurred due to the movement of the soil layer. Only some areas of the slope showedelevation change, and this was believed to be due to thegroundwater generated during rainfall rather than the effect of the waste-rock load at the top. Sensitivity analysis for LS-RAPID simulation was performed, and the simulation results were compared and analyzed by applying a digital elevation model (DEM) and a digital surface model (DSM)as terrain data with 10 m, 5 m, and 4 m grids. When data with high spatial resolution were used, the extent of the sedimentation of landslide material tended to be excessively expanded in the DEM. In contrast, in the result of applying a DSM, which reflects the topography in detail, the diffusion range was not significantly affected even when the spatial resolution was changed, and the sedimentation behavior according to the river shape could be accurately expressed. As a result, it was concluded that applying a DSM rather than a DEM does not significantly expand the sedimentation range, and results that reflect the site situation well can be obtained.