Numerical modeling approach for design of water-retaining dams in underground hard rock mines—a case example
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During transition from open pit extractions to underground mining of an orebody, often both the open pit and the underground workings operate simultaneously, before the former is closed. To avoid the risk of inundation, the underground workings connecting or driven closer to the open pit are isolated using bulkheads. In this paper, the authors reviewed some of the theoretical equations and norms followed worldwide for determining the safe dimensions of a bulkhead to withstand water pressure. It is found that the theoretical equations are insufficient to represent the actual mode of failure and the ultimate pressure–bearing capacity of a bulkhead, as they were developed based on only one mode of failure of the dam construction material. For better representation of the bulkhead failure and its strength determination, it is found prudent to conduct strain-softening numerical modeling simulating a real mining scenario. Mode of dam failure and effect of parameters such as dam thickness and roadway dimensions on the ultimate pressure–bearing capacity of an arched bulkhead are studied. Numerical modeling studies show that the failure initiates with tensile cracking of the dam surface, but the bulkhead ultimately fails in a combination of tension and shear yielding. On comparison, it is found that the tensile failure theories underestimate the pressure-bearing capacity of a dam, while the shear strength– and crushing strength–based equations overestimate the same. Further, an application of the numerical modeling technique for design of water-retaining dams at an underground mine for its safe isolation from the open pit is presented.
KeywordsBulkhead design Water-retaining dam Numerical modeling Strain softening Underground mining
The authors would like to thank the Director of CSIR-Central Institute of Mining and Fuel Research for the permission to publish this work. The help and support provided by the officials of Hindustan Zinc Ltd. during the study are gratefully acknowledged.
Compliance with ethical standards
The views expressed in this paper are those of the authors and not necessarily of the institute to which they belong.
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