ICGCM Papers:
Numerical Modeling Developments and Applications
 
 
3-D Discontinuum Numerical Modeling of Rock Mass Stability Investigations due to Ore Extraction and Backfilling, and Subsidence Estimation for an Underground Mine
35th International Conference on Ground Control in Mining
3-D Discontinuum Numerical Modeling of Rock Mass Stability Investigations due to Ore Extraction and Backfilling, and Subsidence Estimation for an Underground Mine
by
Pinnaduwa H.S.W. Kulatilake, University of Arizona, Tucson, United StatesGang Huang, University of Science and Technology Beijing, Beijing, ChinaSrisharan Shreedharan, University of Arizona, Tucson, United StatesSijing CaiHongqing Song, University of Science and Technology Beijing, Beijing, China
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[Conference] 35th International Conference on Ground Control in Mining
[Price] Free  [Comments] 0
[Topical Area] Numerical Modeling Developments and Applications
[Author] Pinnaduwa H.S.W. Kulatilake, University of Arizona, Tucson, United StatesGang Huang, University of Science and Technology Beijing, Beijing, ChinaSrisharan Shreedharan, University of Arizona, Tucson, United StatesSijing CaiHongqing Song, University of Science and Technology Beijing, Beijing, China
[Abstract] 
Key Conclusions:
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It was possible to include the essential features of complex lithology and fault system, rock mass and joint/fault mechanical properties, backfill properties, in-situ stresses and sequential stoping and backfilling operations in developing the numerical model to investigate stability around stopes and to estimate the surface subsidence. The paper is an excellent addition to the literature in the fields of rock mass stability around underground excavations and surface subsidence estimation in a complex geologic region, with irregular orebodies and incorporating realistic excavation sequences and backfilling operations.
Key Findings:
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The numerical model indicated large failure zones around the stopes, compressive stresses in pillars greater than their strengths, and deformations up to 50 cm on the roof of the stopes. Backfilling was seen to prevent subsequent deformations in the stopes. The excavation of the upper stopes was found to destabilize the area around the lower stopes thereby causing large deformations after the excavation of the lower stopes. Due to the irregular shape of the orebody, the surface subsidence weighs more towards the left side of the model with a maximum subsidence of about 22.5 cm observed 150 m to the left of the central axis.
Objective of the Paper:
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The distinct element method (DEM) and specifically 3DEC has been selected to carry out analyses on the stability of the underground excavations and surface subsidence at Luohe mine, because it adequately describes behavior of discontinuities and allows for stoping and backfilling simulations. The lithological and structural geology information, rock mass and joint/fault mechanical properties, backfill properties and in-situ stress measurements have been obtained from unpublished reports from the mine to create accurate numerical models. The results of the numerical simulations of 16 sequential stoping and backfilling operations have been used to study and discuss the stability of the underground excavations and to estimate the possible subsidence due to future mining activities at Luohe iron mine.
Problem Statement:
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Luohe iron mine is located in the south of Hefei city, Anhui province in China. The mineral deposits in this location were discovered in the 1960s and the total iron ore reserve was estimated to be about 300 million tonnes. The mineral in the ore is predominantly pyrite. The major orebody lies at a depth of 400 m, with an average thickness of 250 m. The mining method adopted in this mine is open stoping with subsequent backfilling. The excavation process began in 2007 and the orebody was divided into two sections- the east and west parts, for the purpose of ore extraction. By early 2014, six stopes were designed with a production rate of 2 million tons and gradually being increased to the design capacity of 3 million tons per annum, at the end of the first phase. The landscape above the underground mine contains multiple villages, farmlands and other miscellaneous infrastructure facilities which must be protected from any adverse effects arising from the mining activities at Luohe. Specifically, ore extraction and blasting are known to cause surface subsidence. While the mine has taken precautions in the form of backfilling, to prevent long-term subsidence, the process of ore extraction itself may cause some level of irreversible subsidence. Hence, there is a need to study the stability of the stopes designed at Luohe, with special emphasis on estimations of future subsidence.