• Geomechanics and Engineering
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• 제12권4호
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• pp.657-673
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• 2017

Preventing water seepage and inrush into mines where close multiple-seam longwall mining is practiced is a challenging issue in the coal-rich Ordos region, China. To better protect surface (or ground) water and safely extract coal from seams beneath an aquifer, it is necessary to determine the height of the mining-induced fractured zone in the overburden strata. In situ investigations were carried out in panels 20107 (seam No. $2-2^{upper}$) and 20307 (seam No. $2-2^{middle}$) in the Gaojialiang colliery, Shendong Coalfield, China. Longwall mining-induced strata movement and overburden failure were monitored in boreholes using digital panoramic imaging and a deep hole multi-position extensometer. Our results indicate that after mining of the 20107 working face, the overburden of the failure zone can be divided into seven rock groups. The first group lies above the immediate roof (12.9 m above the top of the coal seam), and falls into the gob after the mining. The strata of the second group to the fifth group form the fractured zone (12.9-102.04 m above the coal seam) and the continuous deformation zone extends from the fifth group to the ground surface. After mining Panel 20307, a gap forms between the fifth rock group and the continuous deformation zone, widening rapidly. Then, the lower portion of the continuous deformation zone cracks and collapses into the fractured zone, extending the height of the failure zone to 87.1 m. Based on field data, a statistical formula for predicting the maximum height of overburden failure induced by close multiple seam mining is presented.

• Geomechanics and Engineering
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• 제28권3호
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• pp.299-311
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• 2022

Water-resisting key stratum (WKS) between coal seams is an important barrier that prevents water inrush from goaf in roof under multi-seam mining. The occurrence of water inrush can be evaluated effectively by analyzing the fracture of WKS in multi-seam mining. A "long beam" water inrush mechanical model was established using the multi-seam mining of No. 2+3 and No. 8 coal seams in Xiqu Mine as the research basis. The model comprehensively considers the pressure from goaf, the gravity of overburden rock, the gravity of accumulated water, and the constraint conditions. The stress distribution expression of the WKS was obtained under different mining distances in No. 8 coal seam. The criterion of breakage at any point of the WKS was obtained by introducing linear Mohr strength theory. By using the mechanical model, the fracture of the WKS in Xiqu Mine was examined and its breaking position was calculated. And the risk of water inrush was also evaluated. Moreover, breaking process of the WKS was reproduced with Flac3D numerical software, and was analyzed with on-site microseismic monitoring data. The results showed that when the coal face of No. 8 coal seam in Xiqu Mine advances to about 80 m ~ 100 m, the WKS is stretched and broken at the position of 60 m ~ 70 m away from the open-off cut, increasing the risk of water inrush from goaf in roof. This finding matched the result of microseismic analysis, confirming the reliability of the water inrush mechanical model. This study therefore provides a theoretical basis for the prevention of water inrush from goaf in roof in Xiqu Mine. It also provides a method for evaluating and monitoring water inrush from goaf in roof.

• 자원환경지질
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• 제41권4호
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• pp.453-464
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• 2008

이 연구에서는 폐탄광 지역에서 발생하는 지반침하와 지하 채굴적 사이의 상관성을 지질, 지하구조, 탄층의 심도와 두께, 지하갱도의 분포 측면에서 분석하고자 하였다. 연구대상 지역은 강원도 삼척시 삼척탄전에 속하며, 채굴적 특성을 고려하지 않은 기존의 연구에서 수치지질도, 수치갱내도, 현장조사보고서 자료와 GIS의 공간분석기법을 적용하여 지반침하 취약성이 높게 분석된 지역에 해당된다. 연구지역에 대한 수치지질도 및 지반안정성 조사 보고서를 기반으로 연구지역내에서 지반침하가 관측된 지역의 분포, 지표 및 지하의 지질구조와 탄층의 분포현황을 분석하였고, 수치갱내도 자료를 이용하여 지하 갱도의 심도 및 중첩분포 현황을 분석하였다. 연구결과, 지표의 암석 강도 저하, 얕은 심도와 두꺼운 층후의 함탄층 존재가 지반침하 발생과 밀접한 관련이 있는 것으로 분석되었다. 또한, 다수의 중첩된 갱도의 분포 및 얕은 심도의 지하 갱도 존재, 단층의 존재 역시 지반침하발생에 영향을 주는 주요인으로 확인되었다. 지반침하 위험지역을 정량적으로 예측함에 있어, 연구결과로 나타난 지반침하 관련 요인을 추가로 데이터베이스화하여 폐탄광 지역별로 적합한 지반침하예측 모델을 구축한다면 폐탄광 지역의 지반침하위험 예측 및 예방에 매우 효과적일 것으로 판단된다.