A Study of Blast Induced Rock Mass Displacement Through Physical Measurements and Rigid Body Dynamics Simulations

Alan Tordoir (2009). A Study of Blast Induced Rock Mass Displacement Through Physical Measurements and Rigid Body Dynamics Simulations PhD Thesis, Sustainable Minerals Institute, The University of Queensland.

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Author Alan Tordoir
Thesis Title A Study of Blast Induced Rock Mass Displacement Through Physical Measurements and Rigid Body Dynamics Simulations
School, Centre or Institute Sustainable Minerals Institute
Institution The University of Queensland
Publication date 2009-08
Thesis type PhD Thesis
Supervisor Dr Italo Onederra
Professor Alan Bye
Dr Dion Weatherley
Total pages 323
Total colour pages 112
Total black and white pages 211
Subjects 04 Earth Sciences
Abstract/Summary Abstract In open pit mining operations, blast induced rock mass displacement can have a significant impact on ore recovery and downstream productivity. A comprehensive review of the literature has shown that quantifying displacement on a regular basis has generally been limited by the complexity involved in measuring the process. As a result, various empirical and numerical modelling approaches have been developed to estimate the magnitude of displacement for given blast design inputs. Advanced three-dimensional numerical approaches are limited by their computational requirements and are yet to be routinely applied to full scale conditions. The use of simpler numerical approaches have shown potential but previous attempts have been limited by the oversimplification of boundary conditions, disregard for key processes such as inter-particle collisions and are generally two dimensional in nature. The implementation of these models within the production environment has been onerous as a result of the numerous calibration parameters required to generate reliable results. The recent development of the Blast Movement Monitoring (BMM) system and advances in software and hardware dedicated to computational rigid body dynamics, have facilitated new avenues in which blast induced rock mass displacement can be studied and modelled. The main objective of this thesis is to improve our knowledge of the key factors that influence rock mass displacement through: • the analysis of direct physical measurements of full scale production blasts; • and the development of a practical three dimensional blast movement modelling framework aimed at the production stages of operating mines. To gain a better understanding of the main factors which control rock mass displacement in open pit production blasting environments, a comprehensive analysis of physically measured displacement data has been conducted using a combination of advanced data mining and classical statistical techniques. Three main data sets were used for this analysis, including existing data published as part of two Masters thesis from the Mackay School of Mines; data collected during the development of the BMM system at the University of Queensland’s Julius Kruttschnitt Mineral Research Centre (JKMRC), and new data collected as part of this thesis to supplement the sparse areas within the Mackay and JKMRC data sets. This new data set was gathered at the Mogalakwena Platinum Mine in the Republic of South Africa. Results from the analysis of the three data sets has shown that the main parameters controlling rock mass displacement in open pit production blasting include the three dimensional explosive energy distribution, the orientation of timing contours and confinement effects such as the distance from the free face and stemming influence. These parameters provide the basis from which displacement outcomes such as the magnitude and direction of movement can be estimated and allowed the development of a novel framework to model blast induced rock mass displacement in three dimensions. The proposed modelling framework takes a mechanistic approach by combining rigid body dynamics with established empirical relations and material properties to simulate the displacement of the rock mass under specified blasting conditions. To improve on the current limitations of existing models, the framework addresses six major requirements. These are: 1. the ability to model displacement in three dimensional space while taking into account particle interaction, 2. the ability to incorporate input parameters available to engineers onsite, 3. the ability to model the transition from unconfined to confined blasting conditions, 4. the ability to run within a reasonable time frame, 5. the ability to be calibrated to production blasting conditions using existing technology, and 6. the ability to build models that can be linked directly to block modelling techniques found in geological and mine planning software. The modelling framework consists of a discretised block model of the blast volume that can be described by the positions and orientations of the blocks at each time step during the simulation. All blocks are assigned two initial conditions based on spatial energy distribution and timing contour analysis. These initial conditions define the blocks initial displacement vector prior to the rigid body dynamics program’s particle collision algorithms taking over. To account for the loss of shock and ineffective energy during the breakage process, an energy loss weighting factor is applied to the calculated energy values. Results from three case studies of full scale production blasts have shown that the model generally responds well to the horizontal component of the three-dimensional displacement vector but is less accurate in the vertical displacement direction. This is the first time that a three dimensional displacement model has been evaluated against actual sub-surface displacement data. The model evaluation has indicated that the introduced energy loss factor can be successfully used as a calibration parameter. For all three case studies, the model ran within a reasonable time frame, the longest averaging 45 minutes to simulate a blast volume in the order of 125,000 m3. Detailed analysis has also helped identify the main limitations of the current framework and directions for future work.
Keyword Blast movement, blast movement modelling, Blast Movement Monitor (BMM), Self-Organising Maps (SOM), rigid body dynamics, physics engines
Additional Notes Colour: 18, 29,38, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 53, 54, 60, 75, 77, 83, 86, 87, 91, 93, 94, 96, 97, 98, 101, 104, 113, 114, 116, 117, 122, 125, 127, 138, 140, 141, 143, 144, 145, 147, 148, 154, 160, 162, 166, 177, 179, 181, 183, 184, 185, 187, 188, 190, 192, 193, 194, 195, 196, 213, 233, 234, 235, 236, 237, 261, 262, 263, 264, 265, 266, 267, 271, 272, 273, 277, 278, 280, 282, 283, 284, 286, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 319 Landscape: 40, 60, 68, 70, 72, 75, 77, 80, 122, 125, 127, 166, 184, 187, 190, 213, 261, 262, 263, 264, 265, 266, 267, 288, 289, 290, 291, 292, 293, 294, 295, 296, 297, 298, 299, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 312, 313, 314, 315, 316, 317

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Created: Fri, 23 Apr 2010, 17:56:21 EST by Mr Alan Tordoir on behalf of Library - Information Access Service