PhD Oral Exam - Hooman Dabirmanesh, Civil Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Toppling failure in jointed rock masses presents a complex geological challenge. Conventional numerical methods often struggle to capture its intricacies, particularly when dealing with jointed rock masses. Experimental studies are both time-consuming and financially demanding. To address these challenges, this thesis employs the Discrete Element Method (DEM), a powerful numerical tool capable of accurately simulating toppling failure processes in jointed rock masses, with a specific focus on block-flexural toppling in natural rock slopes. DEM not only accurately replicates toppling failure but also provides an efficient alternative to expensive experiments.

The research convincingly demonstrates DEM's precision in predicting failure surfaces and its ability to accommodate large deformations and discontinuities make it a powerful tool. The Discrete Element Method emerges as a potent and cost-effective tool for simulating toppling failure in jointed rock formations, accommodating large deformations, block interactions, and the consideration of discontinuities during failure. The developed DEM code was utilized to simulate and investigate the toppling failure after being validated with experimental test results. The study also explores key parameters like joint friction angles, spacing, and basal joint sets, investigating their influence on failure mechanics and the overall failure surface, a fundamental assumption in the theoretical method for analyzing toppling failure based on the limit equilibrium method. Overall, this study highlights the assumption of a single failure surface used in the limit equilibrium method is not necessarily valid for block-flexural toppling failures.

Utilizing a developed computational code, this research extends its relevance to real-world scenarios, effectively simulating complex rock slope conditions. It emphasizes the importance of particle size calibration in DEM simulations, highlighting the need to strike a balance between accuracy and computational efficiency. The research reveals that the maximum particle size relative to the minimum sub-domain size, represented by joint spacing or block width, is critical for precise simulations.

The findings indicate that DEM excels in capturing the complexities of toppling failures, especially when challenged with large deformations and block separation. In practical scenarios, DEM outperforms traditional theoretical methods by providing a more accurate assessment of safety factors and offering insights into the intricate micro-level interactions within rock slopes.

Together, this research provides a comprehensive understanding of simulating toppling failure via DEM, facilitating insights into its behavior. The discoveries substantially advance in producing empirical approaches and enhancing our grasp of the intricate toppling failure mechanisms within jointed rock masses, offering invaluable support to the field of geotechnical engineering.