• Geomechanics and Engineering
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• 제22권5호
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• pp.461-473
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• 2020

Natural rock mass contains defects of different shapes, usually filled with inclusions such as clay or gravel. The presence of inclusions affects the failure characteristics and mechanical properties of rock mass. In this study, the strength and failure characteristics of rock with inclusions were studied using the particle flow code under uniaxial compression. The results show that the presence of inclusions not only improves the mechanical properties of rock with defects but also increases the bearing capacity of rock. Circular inclusion has the most obvious effect on improving model strength. The inclusions affect the stress distribution, development of initial crack, change in crack propagation characteristics, and failure mode of rock. In defect models, concentration area of the maximum tensile stress is generated at the top and bottom of defect, and the maximum compressive stress is distributed on the left and right sides of defect. In filled models, the tensile stress and compressive stress are uniformly distributed. Failing mode of defect models is mainly tensile failure, while that of filled models is mainly shear failure.

• 한국터널지하공간학회 논문집
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• 제15권6호
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• pp.613-623
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• 2013

현재 국내 석회석광산은 개발 방식 및 특성에 따라 환경적, 사회적, 경영적 측면에서 다양한 문제 등을 내포한 채 운영되고 있다. 따라서 최근에는 이 같은 문제점들을 저감하고 지속가능한 광산개발을 위하여, 갱내채광 혹은 시설물 갱내화 등 다양한 노력이 계속되고 있다. 이러한 노력은 기존의 광산개발 공간 외에 새로운 지하대형공간의 생성을 유발하기 때문에, 작업자 및 시설물의 안전성확보를 위하여 발생 가능한 다양한 종류의 리스크에 대한 재난관리 필요성이 제기되고 있다. 본 연구에서는 지하대형공간을 구축하고 시설물을 갱내화하여 본격가동을 앞둔 석회석광업현장의 작업자들을 대상으로 설문조사를 실시하여 리스크 위험도평가 및 업무영향력분석 후 재난관리를 위한 업무우선순위를 도출하였다. 그 결과, 대상 현장의 경우 파분쇄 및 분립선별공정에서 안전수칙 불이행으로 인한 리스크에 대하여 위험도가 가장 높은 것으로 나타났다. 또한, 이 리스크에 대한 재난발생시 업무연속성 유지를 위한 영향력을 분석결과 우선적으로 갱내외의 연계작업이 원활하게 이루어지도록 해야 하는 것으로 나타났다.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2009년도 추계학술발표논문집
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• pp.263-266
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• 2009

석탄광산의 선탄장(選炭場)에서 운용하는 장치들로부터 발생하는 석탄분진의 입도분포를 현장조사와 실내분석을 통하여 파악하였으며, 연구결과는 광해(鑛害)로서 작용하는 석탄분진을 포집하는 집진기(A Dust Collector)의 설계에 필요한 자료로 제시하고자 한다. 연구결과 TB업체의 분진 입도분포는 $1{\mu}m$이하의 미세(微細)입자와 $100{\mu}m$이상의 조대(粗大)입자가 차지하는 비중이 미약한 반면, 특히 $5{\mu}m{\sim}80{\mu}m$ 사이에 분포되는 분진들이 89.2%로 나타나 발생분진의 대부분을 차지하는 것으로 파악되었다. 이들 중 원심집진기에 포집된 분진은 $70{\mu}m$이하에서 89.5%인 반면 여과집진기에서 포집된 분진의 90.0%가 $20{\mu}m$이하인 것으로 나타났다. SD업체의 분진 또한 $1{\mu}m$이하와 $100{\mu}m$이상 입자는 적은 분포를 보인 반면, $5{\mu}m{\sim}70{\mu}m$사이에 분포되는 분진들이 89.6%로 나타나 발생분진의 대부분을 차지하는 것으로 파악되었다. 이들 중 여과집진기에 포집된 분진의 입도는 $30{\mu}m$이하에서 96.2%인 것으로 나타났다.

• 터널과지하공간
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• 제22권6호
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• pp.383-392
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• 2012

본 연구에서는 안전하고 친환경적인 광산관리를 위해 스마트 광산재난관리체계인 $M_{(i,j,k)}BCP$(Mining Business Continuity Planning)를 제안하였다. 여기서 'i'는 광산의 종류, 'j'는 광산의 업무공정, 그리고 'k'는 공정별 리스크 이다. 특히, 본 연구는 'i=1=석회석 광산'으로 규정하고 석회석광산의 재난관리체계를 $M_{(i,j,k)}BCP$로 제안하였다. 본 논문에 사용된 광산 리스크들은 문헌자료와 전문가 의견 분석을 통하여 얻었으며, 이러한 리스크들을 석회석 광산의 5대 공정에 맞도록 분류하여 그 수를 약 60개에서 26개로 줄였다. 줄여진 리스크들은 $M_{(i,j,k)}BCP$에 할당되고 평가되었다. 본 연구에서 리스크 평가에 사용한 척도는 1회 이상 발생빈도, 인명피해, 시설물피해, 업무중단시간 등 4가지이다. 리스크 평가 결과에 의하면, 리스크들은 4개의 특화된 군으로 분리될 수 있었다. 또한, 석회석 광산에서는 '채광 중 갱내 낙반 또는 붕락 발생 리스크'의 발생가능성과 위험도가 가장 높은 것으로 나타났다. 이 리스크에 대한 재난관리체계는 '$M_{(1,2,1)}BCP$'이다. 이는 석회석광산 개발시 $M_{(1,2,1)}BCP$가 최우선적으로 수립되어야 함을 의미한다.

• Geomechanics and Engineering
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• 제22권3호
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• pp.255-264
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• 2020

With the ongoing development of deep mining of coal resources, some coal mine dynamic disasters have exhibited characteristics of both coal-gas outbursts and rockbursts. Therefore, research is required on the mechanism of rockburst-outburst coupling disaster. In this study, the failure characteristics of coal-rock combination structures were investigated using lab-scale physical simulation experiments. The energy criterion of the rockburst-outburst coupling disaster was obtained, and the mechanism of the disaster induced by the gas-solid coupling instability of the coal-rock combination structure was determined. The experimental results indicate that the damage of the coal-rock structure is significantly different from that of a coal body. The influence of the coal-rock structure should be considered in the study of rockburst-outburst coupling disaster. The deformation degree of the roof is controlled by the more significant main role of the gas pressure and the difference in the strength between the rock body and the coal body. The outburst holes and spall characteristics of the coal body after the failure of the coal-rock structure are strongly affected by the difference in strength between the roof and the coal body. The research results provide an in-depth understanding of the mechanism of rockburst-outburst coupling disasters in deep mining.

• 한국지구과학회지
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• 제43권1호
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• pp.119-127
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• 2022

최근 들어 기후변화로 인한 태풍의 강도는 강력해졌다. 광산지역의 광미와 폐석은 수해로 인해 환경에 악영향을 미쳤을 것으로 추정된다. 강릉지역은 3,693호(1936), 루사(2002), 매미(2003), 메기(2004) 등의 국내 최대 태풍의 영향은 받았다. 이번 연구는 태풍으로 인한 수해 이후 하천을 따라 그 주변에 높은 농도의 비소가 검출된 사례를 기초로 하였다. 환경피해 관련 법은 오염 원인자의 책임을 명확히 하고 있지만, 잠재적인 자연재해 지역에서는 세심한 적용이 필요하다. 이러한 지역에서 자연재해의 영향을 최소화하기 위해서 관련 법들의 개선과 연계가 필요하다. 이 연구가 하류 지역에서 혼재된 오염물질 대응에 도움이 되길 기대한다.

• Geomechanics and Engineering
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• 제24권6호
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• pp.519-529
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• 2021

In coal mining activities, the abutment stress of the coal has to undergo cyclic loading and unloading, affecting the strength and seepage characteristics of coal; additionally, it can cause dynamic disasters, posing a major challenge for the safety of coal mine production. To improve the understanding of the dynamic disaster mechanism of gas outburst and rock burst coupling, triaxial devices are applied to axial pressure cyclic loading-unloading tests under different axial stress peaks and different pore pressures. The existing empirical formula is use to perform a non-linear regression fitting on the relationship between stress and permeability, and the damage rate of permeability is introduced to analyze the change in permeability. The results show that the permeability curve obtained had "memory", and the peak stress was lower than the conventional loading path. The permeability curve and the volume strain curve show a clear symmetrical relationship, being the former in the form of a negative power function. Owing to the influence of irreversible deformation, the permeability difference and the damage of permeability mainly occur in the initial stage of loading-unloading, and both decrease as the number of cycles of loading-unloading increase. At the end of the first cycle and the second cycle, the permeability decreased in the range of 5.777 - 8.421 % and 4.311-8.713 %, respectively. The permeability decreases with an increase in the axial stress peak, and the damage rate shows the opposite trend. Under the same conditions, the permeability of methane is always lower than that of helium, and it shows a V-shape change trend with increasing methane pressures, and the permeability of the specimen was 3 MPa > 1 MPa > 2 MPa.

• Structural Engineering and Mechanics
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• 제85권3호
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• pp.337-351
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• 2023

In this paper, the shear behavior of soft filling in rectangular-hollow concrete specimens was simulated using the 2D particle flow code (PFC2D). The laboratory-measured properties were used to calibrate some PFC2D micro-properties for modeling the behavior of geo-materials. The dimensions of prepared and modeled samples were 100 mm×100 mm. Some disc type narrow bands were removed from the central part of the model and different lengths of bridge areas (i.e., the distance between internal tips of two joints) with lengths of 30 mm, 50 mm, and 70 mm were produced. Then, the middle of the rectangular hollow was filled with cement material. Three filling sizes with dimensions of 5 mm×5 mm, 10 mm×5 mm, and 15 mm×5 mm were provided for different modeled samples. The parallel bond model was used to calibrate and re-produce these modeled specimens. Therefore, totally, 9 different types of samples were designed for the shear tests in PFC2D. The shear load was gradually applied to the model under a constant loading condition of 3 MPa (σc/3). The loading was continued till shear failure occur in the modeled concrete specimens. It has been shown that both tensile and shear cracks may occur in the fillings. The shear cracks mainly initiated from the crack (joint) tips and coalesced with another one. The shear displacements and shear strengths were both increased as the filling dimensions increased (for the case of a bridge area with a particular fixed length).

• Geomechanics and Engineering
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• 제19권6호
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• pp.499-511
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• 2019

The reliability of reinforced concrete structures is frequently compromised by the deterioration caused by reinforcement corrosion. Evaluating the effect caused by reinforcement corrosion on structural behaviour of corrosion damaged concrete structures is essential for effective and reliable infrastructure management. In lifecycle management of corrosion affected reinforced concrete structures, it is difficult to correctly assess the lifecycle performance due to the uncertainties associated with structural resistance deterioration. This paper presents a stochastic deterioration modelling approach to evaluate the performance deterioration of corroded concrete structures during their service life. The flexural strength deterioration is analytically predicted on the basis of bond strength evolution caused by reinforcement corrosion, which is examined by the experimental and field data available. An assessment criterion is defined to evaluate the flexural strength deterioration for the time-dependent reliability analysis. The results from the worked examples show that the proposed approach is capable of evaluating the structural reliability of corrosion damaged concrete structures.

• Geomechanics and Engineering
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• 제31권4호
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• pp.365-373
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• 2022

In order to investigate the damage evolution law of rock specimens under cyclic loading, cyclic loading tests under constant loads with different amplitudes were carried out on limestone specimens with high strength and brittleness values using acoustic emission (AE) technology and the energy evolution and AE characteristics were evaluated. Based on dissipated energy density and AE counts, the damage variable of specimen was characterized and two damage evolution processes were analyzed and compared. The obtained results showed that the change of AE counts was closely related to radial deformation. Higher cyclic loading values result in more significant radial strain of limestone specimen and larger accumulative AE counts of cyclic loading segment, which indicated Felicity effect. Regarding dissipated energy density, the damage of limestone specimen was defined without considering the influence of radial deformation, which made the damage value of cyclic loading segment higher at lower amplitude loads. The damage of cyclic loading segment was increased with the magnitude of load. When dissipated energy density was applied to define damage, the damage value at unloading segment was smaller than that of AE counts. Under higher cyclic loading values, rocks show obvious damage during both loading and unloading processes. Therefore, during deep rock excavation, the damages caused by the deformation recovery of unloading rocks could not be ignored when considering the damage caused by abutment pressure.