Crack initiation and propagation in molded gypsum specimens with pre-cracked single flaws

• Main Author: Tan, Eunice Shu Fen.
• Other Authors: School of Civil and Environmental Engineering
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/49271
• Institution: Nanyang Technological University

Discontinuities in rocks can affect the strength and stiffness of rocks which are important factors in rock mechanics. This study aims to observe the initiation and propagation of cracks emanating from a single pre-existing flaw in molded gypsum specimens when tested in uniaxial compression. The effect of the orientation of the artificial flaws was studied by varying the inclination angle of the flaw to the horizontal. Flaws oriented at 0°, 5°, 10° and 15° were introduced to the molded gypsum specimens. The specimens were then subjected to uniaxial compression loading and a high speed video system (high speed camera) was used to record the cracking process. The chronology of cracks was identified by viewing the individual frames in the high speed video. Results from the experimental study showed that the first cracks to initiate were tensile in nature and were usually tensile wing cracks. The initiation of the cracks usually occurred at a distance slightly away from the flaw tip and towards the centre of the flaw for the small flaw inclination angles. These results suggest that even for the small inclination angles not explored extensively previously, the crack initiation and propagation are similar to the studies done previously. However, more studies should be done to reduce the experimental errors and imperfections in the specimens’ preparations and high speed video recordings.