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Deane de Mesquita Roehl Numerical Analysis of Blast Induced Fracturing in Rock Masses Araken Dumont Ramos Lima, Celso Romanel and Deane de Mesquita Roehl This work presents a numerical methodology based on the finite element method for the analysis of dynamic fracture propagation in rock masses due to blasting loads. The dynamic load is applied at several drilled blast-holes, either as a simultaneous or a sequential event, from which the fractures develop. Both location and direction of fractures are considered not predetermined. Closure of fractures by unloading or fracture interaction is included in the numerical model. The rock mass is admitted as a brittle material and linear elastic fracture mechanics is used for stress analysis considering fracture modes I and II. The corresponding stress intensity factors are obtained from the singular finite elements through calculations of strain-energy release rates. The model employs an adaptive mesh generation scheme by which a new finite element discretization is automatically generated as fractures propagate and finite elements are detached from the fragmented rock mass. Quadratic triangular elements are used and dampers are included on the mesh boundaries to prevent spurious reflection of stress waves.. The numerical solution of the equations of motion in the time domain is accomplished with implicit integration schemes. The pressure pulse on the hole wall is represented with basis on Duval theory. In order to avoid penetration of the fracture surfaces during dynamic propagation a penalty based contact algorithm is also incorporated in the numerical solution. Results illustrating the dynamic fracture propagation in a granite rock mass are presented for some geotechnical problems involving blasting operations.
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