A Material Flow Model for Dragline Bucket-Formation Failure Analyses Using the Distinct Element Method
Somua-Gyimah Godfred*, Frimpong Samuel, Awuah-Offei Kwame, Nassib Aouad
Department of Mining & Nuclear Engineering, Missouri University of Science & Technology, 226 McNutt Hall, 1400 N. Bishop Ave., Rolla MO 65409-0330.
The dragline machinery has found applications as a competitive excavator for overburden removal in surface mining operations. This excavator is highly capital intensive with high operating expenditures. However when used with appropriate layout design, optimization and planning, the dragline can achieve favorable economics for material excavation. Dragline operating challenges must be addressed via detailed modeling, simulation and analysis to provide solutions for efficient and effective operations. The mechanics of formation failure differ based on tool geometry, orientation and trajectory. While failure of earth material ahead of the excavation equipment has been the subject of much interest over the years, the failure of material ahead of the dragline bucket has received relatively little attention. In this study, a material flow model has been formulated, verified and validated for understanding formation failure ahead of the bucket during dragline excavation. The model is then used to investigate reported observations about the bucket loading and formation failure processes. The material failure pattern and material density distribution variations generally agree with reported field observations. Starting from an initial zone density of The Region I density rises quickly from 1.01 ton/m3 to 1.25 ton/m3 over 1 m of bucket dragging. Regions II and III densities climbed rapidly from an initial 1.0 ton/m3 to 1.9 ton/m3 and 2.5 ton/m3, respectively over the first 1m of bucket dragging. For each formation type and characteristics, these density variations are important to achieve appropriate maximum suspended loads for preserving dragline longevity.
Key words: Dragline Excavation, Formation Constitutive Model, Discrete Element Modeling, Dragline Bucket CAD Model, Model Verification and Validation, Dragline Simulation, Bucket Region Densities.