Development of numerical manifold method for cracking process in rock

• Main Author: Wu, Zhijun
• Other Authors: Wong Ngai Yuen, Louis
• Format: Theses and Dissertations
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: https://hdl.handle.net/10356/59233
• Institution: Nanyang Technological University

In this thesis, the numerical manifold method (NMM) has been extended for cracking problems, such as crack initiation, crack propagation, crack coalescence and structure safety problems associated with cracks. Different failure criteria have been employed to predict the crack initiation and propagation. A crack representative strategy has been adopted to capture the discontinuity across the crack. Crack evolution techniques have been implemented to treat the manifold elements, the physical covers and the loops during the fracturing process. Based on the partition of unity method, The NMM has been coupled with the fracture mechanics to simulate the linear-elastic fracture problems. Asymptotic crack tip functions extracted from the analytical solution have been incorporated into the local approximation spaces for the singular physical covers, which can overcome the limitations the conventional NMM suffers. Combining with the contact techniques inherited from discontinuous deformation analysis (DDA), the frictional crack propagation problems have been investigated. By incorporating a new way to treat the material interface, the influences of the inclusion stiffness on the cracking behavior of specimen containing inclusions have been discussed. By incorporating an elastic-plastic constitutive model, the effects of the plasticity on the cracking behavior have been investigated. By incorporating a visco-elastic constitutive model, the effects of the loading rate on the cracking behavior have also been discussed. The developed program has been applied to simulate the progressive failure of rock slopes. To overcome the limitation of the conventional NMM, which sometimes improperly removes the interface cohesion, the displacement-dependent cohesion removal method has been adopted. Numerical results indicate that the developed NMM is able to capture the entire processes of the progressive slide surface development related to crack initiation, propagation, coalescence and degradation to eventual catastrophic failure. The present study sh’owed that the NMM is promising for failure analysis in rock engineering and deserves to be further improved for more complex applications in the future.