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Representing spalling in rock excavations with BBM
Bonded block modelling (BBM) is a relatively new numerical modelling technique that attempts to capture rock mass damage through the interaction and breakage of contacts between “blocks” (volumes) of rock. Its suitability for modelling spalling cases in Scandinavia is evaluated in this report. The intended outcome of this work is to provide up-to-date information, guidance, and insights on how BBM can be applied and used by practitioners. While steadily increasing in quantity, the small number of published works on BBM show promising qualities for modelling rock mass damage. A gap in the literature exists, however, concerning many choices those modelling BBM must make. Additionally, the examples found in the literature typically use block sizes which are significantly larger than those that would be required to represent the spalling phenomenon, as spalling occurs at the inter- and intra-grain level. A well-documented spalling case was selected for analysis: Malmberget Mine’s Öde E8 ventilation shaft. The depth of spalling was approximately 10 cm. A BBM material with very small blocks (near grain size) was created. The rock in the shaft was represented by this BBM material through a careful calibration process. This process included models of UCS and Brazilian tests. It was demonstrated that the configuration of the blocks effects the results. In situ quasi-3D models were created with a BBM region in the expected area of spalling. Results were obtained for the calibrated BBM material calibrated to the laboratory test results, as well as a BBM material where the UCS was reduced to that of the laboratory crack initiation value. Spalling was present in both models; however, the position and form did not match that of the actual case. The reduced strength models had more spalling, but still did not achieve the spalling depth of the actual case. Signs exist that the stiffnesses between and in the continuum portion of the model and the discontinuum portion of the model are resulting in some boundary effects. It is one ...
Representing spalling in rock excavations with BBM
Bonded block modelling (BBM) is a relatively new numerical modelling technique that attempts to capture rock mass damage through the interaction and breakage of contacts between “blocks” (volumes) of rock. Its suitability for modelling spalling cases in Scandinavia is evaluated in this report. The intended outcome of this work is to provide up-to-date information, guidance, and insights on how BBM can be applied and used by practitioners. While steadily increasing in quantity, the small number of published works on BBM show promising qualities for modelling rock mass damage. A gap in the literature exists, however, concerning many choices those modelling BBM must make. Additionally, the examples found in the literature typically use block sizes which are significantly larger than those that would be required to represent the spalling phenomenon, as spalling occurs at the inter- and intra-grain level. A well-documented spalling case was selected for analysis: Malmberget Mine’s Öde E8 ventilation shaft. The depth of spalling was approximately 10 cm. A BBM material with very small blocks (near grain size) was created. The rock in the shaft was represented by this BBM material through a careful calibration process. This process included models of UCS and Brazilian tests. It was demonstrated that the configuration of the blocks effects the results. In situ quasi-3D models were created with a BBM region in the expected area of spalling. Results were obtained for the calibrated BBM material calibrated to the laboratory test results, as well as a BBM material where the UCS was reduced to that of the laboratory crack initiation value. Spalling was present in both models; however, the position and form did not match that of the actual case. The reduced strength models had more spalling, but still did not achieve the spalling depth of the actual case. Signs exist that the stiffnesses between and in the continuum portion of the model and the discontinuum portion of the model are resulting in some boundary effects. It is one ...
Representing spalling in rock excavations with BBM
Vatcher, Jessa (author) / Sjöberg, Jonny (author)
2021-01-01
Trafikverkets forskningsportföljer
Paper
Electronic Resource
English
Spalling of rock projections in unsupported underground excavations, and its prevention
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Spalling Experiments on Large Hard Rock Specimens
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