• Journal of the Speleological Society of Korea
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• no.44
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• pp.3-16
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• 1995

동굴에는 석회동굴 그밖에 용암굴과 파식굴 등으로 구별되는데 그 대부분은 석회동굴이다. 석회동굴인 경우 이의 생성과정과 그 특성을 보면 다음과 같다. 지표면에 내린 빗물은 땅속에 스며들어가 지하수류를 이루어 투수층을 따라 흘러 빠져 들어간다. 이때 이 공동이 동굴이 되는데 공동의 천정면에서 떨어지는 물방울이 그 위 지층에서 석회암층을 스며 내릴 때에는 석회질이 용해된 물방울이 공동천정에서 고드름 모양으로 종유석을 발달시키거나 또는 공동바닥에 떨어져 석순을 성장시킨다. 이것이 석회동굴이다.(중략)

• Journal of the Korean GEO-environmental Society
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• v.6 no.1
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• pp.63-72
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• 2005

From the geological and engineering point of view, the limestone is so rigid that it is able to act as a bedrock but if there are some unstable elements which are solubility cavity and cracking zone in the ground, the settlement and bearing capacity of a structure will be required to long-term stability investigations and countermeasures about those problems. When comparing the allowable bearing capacity, the results of Bell's method and the Bowles' method are similar but the results of Hoek-Brown's method are very larger than the others. For weathered limestone, stability is changed by size and depth of the cavity of limestone, but soft and hard rock are stable regardless of size and depth of the cavity.

• The Journal of the Petrological Society of Korea
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• v.16 no.2 s.48
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• pp.47-58
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• 2007

This study examines the distribution of basement rocks in Gyochon-ri, Muan-eup, Muan-gun, Jeonnam where ground subsidence occurred in June 2005, and traces corrosion of limestone. Mica schist and rhyolite are distributed in the surface of the study area, but thick limestone layer with large and small caverns are distributed underground. A horizon of limestone with maximum width of 300 m and 4 km of length was found along the detour which is in the north of pound subsidence. Such identification of limestone presence would be very useful to predict potential ground subsidence. Limestone in this area was disturbed by fold and fault due to severe shearing deformation. Small caverns were frequently found in anticline part of folds formed in limestone layer. Schists with different thicknesses were intercalated in the limestone with shearing deformation and consist of sheet silicate minerals (chlorite and mica) and quartz. In sections of weathered specimen, it is shown that biotite of schist part was altered into chlorite and corrosion of calcite around the schist followed. This suggest that ground water permeated between intercalated sheet silicate minerals and corrosion of limestone began. And small caverns were generated where active corrosion occurred. This study suggests that because of many reasons (for instance, reclamation of the Bulmu reservior and excess pumping), cavern water level was lowered and cave sediments were removed, and it caused ground subsidence to occur.

• Economic and Environmental Geology
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• v.39 no.5 s.180
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• pp.597-605
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• 2006

In this study, we examined the applicability of 3-D electrical resistivity survey to detect underground cavities within ground subsidence area at the field test site, located at Yongweol-ri, Muan-gun in Korea. Underground cavities are widely present within the limesilicate bedrock overlain by the alluvial deposits in the area of the test site where the ground subsidences have occurred in the past. The limesilicate cavities are mostly filled with groundwater and clays in the test site. Thus, cavities have low electrical resistivity compared to the surrounding host bedrock. The results of the study have shown that the zones of low resistivity correspond to the zones of the cavities identified in the boreholes at the test site, and that the 3-D electrical resistivity survey is very effective to detect underground cavities.

• Journal of the Speleological Society of Korea
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• no.48
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• pp.9-16
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• 1996

석회동굴은 유구한 지구 표면 지층의 역사를 되새겨 주는 석회암 층에서 형성되는 지하동굴이다. 바다 속에서 퇴적되어 형성된 석회암 층이 융기 작용으로 지표면에 상승되어 이른 바 석회암 지표 층을 이루고 있는 곳에서는 빗물에 의한 화학작용으로 땅 표면에서 카르스트 윤회과정의 갖가지 지형지물이 발달되는데, 이 때에 지하에 스며든 지하수의 물리 작용으로 곧 지하수류가 흘러 지나간 공동이 생기게 되고, 나아가서는 낙반 및 확장 등으로 지하동굴이 확장되는데, 2차적인 지하수 침투작용으로 석회질 용해수에 의한 2차 생성물이 형성되어 이른 바 화려한 석회동굴이 이루어진다. 그 석회암의 화학 성분 여하에 따라, 그리고 지하수의 지하 투수량에 따라 석회동굴의 양상은 달리 나타나게 된다.

• Explosives and Blasting
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• v.34 no.3
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• pp.10-16
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• 2016

Recently, transition from open pit to underground mining in limestone mines is an increasing trend in Korea due to environmental issues such as noise, dust and vibrations caused by crushers and equipment. The severe damages in the surrounding rock mass of underground opening caused by explosive blasting may lead to rock fall hazards or casualties. It is well known that variables which mainly affect blast-induced rock falls in underground mining are: blast vibration level, joint orientation and distribution and shape of the cross sections of underground structures. In this study, UDEC program, which is a DEM code, is used to simulate blast vibration-induced rock fall in underground openings. Variation of joint space, joint angle and joint normal stiffness was considered to investigate the effect of joint characteristics on the blast vibration-induced rock fall in underground opening. Finally, jointed rock mass models considering blast-induced damage zone were examined to simulate the critical blast vibration value which may cause rock falls in underground opening.

• Tunnel and Underground Space
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• v.15 no.5 s.58
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• pp.369-377
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• 2005

The stability of underground openings is a major concern for the safety and productivity of mining operations. Rock mass classification methods provide the basis of many empirical design methods as well as a basis for numerical analysis. Of the many factors which influence the stability of openings, the span of the opening for a given rock mass condition provides an important parameter of design. In this paper, the critical span curves proposed by Lang, the Mathews stability graph method and the modified critical span curve suggested by the authors have been assessed. The modified critical span curve was proposed by using Mathews stability graph method. The modified critical span curve by the author have been used to assess the stability of underground openings in several limestone mines.

• Tunnel and Underground Space
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• v.28 no.4
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• pp.358-371
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• 2018

The stability of openings in the underground mine is major concern in the operation of mines that must ensure productivity and safety. Among many rock conditions affecting cavities stability, the width and height of the opening is an important design factor. In this paper, we consider to determine the maximum unsupported span of a opening in a limestone mine by using the Q system among several rock classification schemes. In order to determine the span of the unsupported opening in the limestone mine, rock mass classifications were carried out at over 200 sites in the underground limestone mines. The relationships by using the Q system and the stability graph proposed by Mathews to determine the maximum span of the unsupported opening were derived and compared. We propose a new classification method that combines GSI and RMR rock classification systems to make it easy to use in a field.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.167-172
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• 2008

A microgravity survey was applied for detecting and mapping karstic cavities over limestone area at Gaeun. The gravity data were collected at about 1, 100 stations by 4 m interval. The density distribution beneath the profiles was drawn by two dimensional inversion based on the minimum support stabilizing functional, which generated better focused images of density discontinuities. We also imaged three dimensional density distribution by growing body inversion. The density image showed that the cavities were dissolved, enlarged and connected into a cavity network system.

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