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XFEM Modeling of Dynamic Cohesive Crack Propagation in Saturated Porous Media

Babazadeh, Mohsen | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43939 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khoei, Amir Reza
  7. Abstract:
  8. In this thesis, a fully coupled numerical model is developed for the modeling of dynamic cohesive crack propagation and hydraulic fracture in saturated porous media using extended finite element method. Many engineering structures like concrete or soil dams and buildings foundation are built with porous materials like concrete, rock and soil. Behavior of these materials in which void among the solid particles are filled with one or more fluids are so complicated rather than single solid phase. Dynamic analysis of porous mediums containing a discontinuity has many applications in various civil engineering fields including structure, earthquake, hydraulic structures, etc. For instance investigating hydraulic fracture in oil wells, hydraulic fracturing in dams and stability control of gravity dams during an earthquake is dependent on modeling of crack propagation in these media. Mechanical behaviors of saturated porous mediums are related to the interaction of solid skeleton and pore fluid. Therefore numerical analysis of saturated porous mediums can be achieved by deriving governing differential equations and solving the coupled set of equations that consider solid skeleton deformation and pore fluid flow. Cracks can influence overall functions of a structure, so fracture analysis and crack propagation prediction would be an important factor. Cohesive crack model has been used to Model fracture mechanism. This model avoids singularity of stress field around the crack tip which is not a realistic assumption in LEFM. Also it is assumed a cohesive zone will form along the crack propagation path and cohesive traction distribution will be a function of crack separation. Crack propagation in saturated porous mediums and pore fluid flow inside the crack besides the leakage from the crack wall lead to discontinuity in the displacement field and pressure normal derivative to the crack. One of the best numerical methods for considering strong and weak discontinuity in the solution fields is eXtended Finite Element Method. In XFEM, by selecting appropriate enrichment functions and enriching the nodes which are affected by the discontinuity, the need for remeshing would be eliminated. In other words discontinuity modeling would be mesh independent
  9. Keywords:
  10. Saturated Porous Medium ; Cohesive Crack Propagation ; Hydraulic Fracturing ; Dynamic Analysis ; Mixed Mode ; Extended Finite Element Method

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