An Examination of Structural Constraints on Rockfall Behaviour using LiDAR Data

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Rowe, Emily
LiDAR , Rockfall , Deformation , Kinematics , Failure Mechanism , Terrestrial Laser Scanning
Rockfall hazards along railway corridors in western Canada increase the risk of train derailment, which could lead to loss of life, infrastructure, and environmental damage. In some cases, such rockfalls exhibit pre-failure deformation prior to their detachment from the slope. The goal of this research is to gain an improved understanding of such precursory behaviour, and how it may be affected by the orientation and condition of discontinuity planes constraining rockfall source blocks. This thesis therefore focuses on the nature of rockfall failure mechanisms, explored using remote terrestrial laser scanning (TLS) data. TLS data was collected at regular 2-3 month intervals at three study sites along the Thompson-Fraser valley in British Columbia, Canada – namely Goldpan, White Canyon, and Mile 109 – from May 2013 to October 2016. A total of 207 rockfalls were identified across all three sites. For each rockfall, the orientation of joints was measured in the post-failure datasets and used to establish a likely failure mechanism. Pre-failure deformation trends were assessed using a roto-translation approach, which expresses the 3-dimensional transformation of a block from one TLS dataset to a successive dataset in terms of translation and rotation components. Rockfalls were classified by their pattern of deformation as well as failure mechanism and it was concluded that toppling blocks are most likely to exhibit detectable translation and rotation deformation using this method. The pre-failure deformation of blocks at the Goldpan site was also examined using a vector-based method, which measures block movement in a direction normal to the slope. The classification of such blocks by their failure mechanism revealed an apparent linear relationship between rockfall volume and deformation magnitude and duration for toppling and wedge sliding failures, though additional rockfall cases are required to confirm this. The methods for analyzing pre-failure deformation applied in this research have limitations and uncertainties, which are discussed. This work forms a basis for the analysis of precursory rockfall behaviour, which may be used to assess the likelihood and mechanism of future rockfall events.
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