• Tunnel and Underground Space
• /
• v.21 no.2
• /
• pp.138-144
• /
• 2011

Mine closure does often accompany the flooding of mine galleries due to ceasing a pumping operation. When a mine gallery is flooded, rocks around the gallery are fully saturated and the gallery is subject to a water pressure. The uniaxial unconfined compressive strength of a rock depends on its water content and decreases as the water content increases. A water pressure may originate the crack growth of a rock or the discontinuity growth of rock mass. Although the water in a gallery will give some support pressure inside the gallery, the degradation of rock mass properties caused by a water pressure will reduce the stability of the gallery. In this study, 2-dimensional discontinuous and 3-dimensional continuous numerical analyses have been conducted to evaluate an effect that a reduction of rock mass properties around the gallery induced by a water pressure has on the stability of mine gallery. The numerical analyses show that a reduction of rock mass properties caused by a water pressure increases displacements of rock mass around mine gallery. 2-dimensional model is found to give larger values of displacement than 3-dimensional model.

• Tunnel and Underground Space
• /
• v.21 no.5
• /
• pp.370-376
• /
• 2011

To design the drainage system of a mine, it is very important to evaluate the groundwater inflow to the mine workings. In this study, continuous steady state flow through rock mass around mine openings developed in Sungok area of Gagok Mine was analyzed. Saturated only model and Saturated/unsaturated model were used as material models of rock mass. Groundwater quantities flowing into Sungok 160 level which is 1216 m long are computed as 1450 $m^3$/day in case of a saturated model and as 1071 $m^3$/day in case of a saturated/unsaturated model. An effect that hydraulic conductivity has on inflow turned out be greater than precipitation and inflow increased linearly with increase of hydraulic conductivity. It was found that change of hydraulic conductivity ratio and orientation have an impact on the variation of inflow and water table.

• Tunnel and Underground Space
• /
• v.30 no.1
• /
• pp.76-86
• /
• 2020

In this study, a small autonomous driving robot was developed for underground mines using the Light Detection and Ranging (LiDAR) sensor. The developed robot measures the distances to the left and right wall surfaces using the LiDAR sensor, and automatically controls its steering to drive along the centerline of mine tunnel. A field experiment was conducted in an underground amethyst mine to test the driving performance of developed robot. During five repeated driving tests, the robot showed stable driving performance overall. There were no collision accidents with the wall of mine tunnel.

• Tunnel and Underground Space
• /
• v.26 no.6
• /
• pp.455-465
• /
• 2016

The collapse of underground mine development void for mineral resources can cause the subsidence of ground surface. In order to prevent the subsidence of ground, data such as maps or pictures of past mining site is important information for current mine reclamation works. In particular, mine subsidence management was based on mining maps and pictures. The process of the mining area surveys, safety evaluation, and ground reinforcement are normally possible with information such as maps and pictures in past mining. During the Japanese colonial period and 1960's, a lot of mines were developed in Korea indiscriminately. However, mining information at that time is limited to use. In the future, mining information will become even more rare. MIRECO intends to establish a realistic alternative solution. In this study, the basic numerical information of developed mine tunnels in Korea is statistically reviewed, and advanced underground cavity measuring technology was studied. 4,473 mine tunnel opening data of 1,784 abandoned mines in korea were collected and sorted. As a result of the analysis, the average value of small mine tunnel openings in Korea was 1.982 m in height and 1.959 m in width. The mean value of shape factor was analyzed as 0.485. The summary of these numerical mine data will be helpful for understanding and researching Korean abandoned mines. Therefore, the development of measurement technology for abandoned mine cavities and tunnels is expected to facilitate more effective mine subsidence management works in Korea.

• Explosives and Blasting
• /
• v.28 no.1
• /
• pp.55-62
• /
• 2010

Explosive welding was planed in a closed drift of a mine for its reuse. In this study, we analyzed the stabilization of roof and pillar which were expected to be affected by overpressure experienced during the continual explosive welding. Three equations, normal equation, CONWEP and DDESB, were used for the estimation of overpressure. The investigation shows that the continual use of the explosive welding in a drift may result in considerable damage on the drift.

• Tunnel and Underground Space
• /
• v.13 no.6
• /
• pp.421-433
• /
• 2003

Demand for limestone production from both the underground and opencast mines in Korea is gradually increasing. Increase in productivity with safe mining operations is the emphasis laid on the mining industry. KIGAM has undertaken a detailed investigation to apply RMR and Q classification system for the design of underground limestone mining operations. The field investigations were confined to the underground mines of Daesung Mining Development Co. Ltd. and Pyunghae Mines of Korean Airport Service. Modification to the standard RMR and Q for limestone mines in Korea along with the correlation between these two systems are discussed while attempts were also made to calculate the width of a safe unsupported span.

• Tunnel and Underground Space
• /
• v.17 no.6
• /
• pp.503-510
• /
• 2007

Rock classification schemes such as RMR, Q-system were applied to investigate the stability of large-scale gangways mined in a limestone mine. 22 areas for engineering geological surveys were selected and rock classifications at each survey point had been carried out. Considering the fact that the observed gangways have not experienced some severe failure and have been stably maintained till now, it is found that Q-system is more reasonable than RMR in evaluating the stability of unsupported span. Also, extended Mathews stability graph method which is a kind of revised Q-system was used to assess the stability of gangways and the results represent that all gangways except for one area are under stable condition. Based on above the mentioned results, the empirical equations to design the maximum unsupported span and critical height of a large-scale gangway are suggested.

• The Journal of Engineering Geology
• /
• v.20 no.1
• /
• pp.71-78
• /
• 2010

The Gagok mine is a contact metasomatic deposit, located at Gagok-myeon, Samcheok city and Cheoram-dong, Taebaek city, Gangwon province. The deposit lies within the limestone of Myobong and Pungchon formations, and exists the contact of intrusive granite porphyry. In order to determine the direction and extension of mineralization in the gallery and around the entrance of the ore deposit, we used the ground magnetic survey, the direct current (dc) resistivity survey using dipole-dipole array, and resistivity tomography survey. The ground magnetic survey did not detect the anomalous zone due to ore deposit, while the dc resistivity survey and resistivity tomography survey were successful in delineating the anomalous zone related to the extension of fault toward $N50^{\circ}W$.

• Tunnel and Underground Space
• /
• v.15 no.6 s.59
• /
• pp.425-431
• /
• 2005

A series of geotechnical surveys and in-situ tests were carried out to evaluate the stability of underground mine cave in an abandoned coal mine. After the closure of the mine, the underground mine drifts have been utilized for a tourist route since 1999. The dimension of the main cave is 5m width, 3m height and 230m length. The surrounding rock mass of the cave is consist of black shale, coal and limestone. Also, the main cave is intersected by two fault zone. Detailed field investigations including Rock Mass Rating(RMR), Geological Strength Index(GSI) and Q classification were performed to evaluate the stability of the main cave and to examine the necessity of reinforcement. Based on the results of rock mass classification and numerical analysis, suitable support design was recommended for the main cave. RMR and Q values of the rock masses were classified in the range of fair to good. According to the support categories proposed by Grimstad & Barton(1993), these classes fall in the reinforcement category of the Type 3 to Type 1. A Type 3 reinforcement category signifies systematic bolting and no support is necessary for the Type 1 case. From the result of numerical analysis, it was inferred that additional support on the several unstable blocks is required to ensure stability of the cave.

• Tunnel and Underground Space
• /
• v.27 no.1
• /
• pp.1-11
• /
• 2017

Most of the local limestone mines are developed as large-opening underground mines, while mine ventilation is heavily dependent on the natural ventilation and auxiliary systems, rather than the mechanical ventilation system using main fans. The current auxiliary ventilation system with fan and ducting requires optimization since enhanced deployment of diesel equipment demands higher airflow rate and the associated cost is expected to be too excessive for the local mine operators. This paper aims at optimizing the fan capacity for the working site ventilation through comparing the fan pressure in the mine airway and the ventilation efficiency of an axial-flow fan and a propeller fan developed in this study.