Shoreline Geomechanics at Hopewell Rocks Provincial Park, New Brunswick, Canada: Stability of the Elephant Rock, Sentinel, and Lover’s Arch Formations
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Authors
Hyslop, Amanda
Date
2024-09-05
Type
thesis
Language
eng
Keyword
Sea Stacks , Slope Stability , FEM Numerical Modeling , Photogrammetry , UAV , Rockfall , Bay of Fundy , Hopewell Rocks Provincial Park
Alternative Title
Abstract
Sea stacks are natural pillars of rock that have been detached by wave action and other erosional processes from adjacent cliff-lined shores. The Hopewell Rocks Provincial Park in New Brunswick, Canada is situated along the coast of the Bay of Fundy, which is home to the largest tidal range in the world. The Park is a popular attraction for geotourism, as it hosts numerous sea stacks and arches that can be accessed on foot during low tide and by kayak during high tide. Approximately 2-3 small scale rockfalls from the cliffs occur at the Park each year, and larger scale rockfalls from the sea stacks occur much less frequently. This research investigates the failure mechanism through a back analysis of the partial collapse of the Elephant Rock formation and the stability of the Sentinel, and Lovers’ Arch formations through a forecast stability analysis using geomechanics numerical models. The primary sea stack failure modes in the Park—block failure, sea stack collapse, and sea arch collapse—are evaluated for the Elephant Rock, Sentinel, and Lover's Arch formations, respectively.
The partial failure of the Elephant Rock occurred on March 14th, 2016. The geomechanical interpretation of the failure mechansism is supported by: analyses of a 3D Structure-from-Motion (SfM) photogrammetry model of the failure surface; photographs taken before and after the failure; historic tidal, climate, and weather data; and the historic rockfall database from the Park. The failure mechanism of the Elephant Rock is interpreted to be a multi-stage combination of toppling and sliding failures. The failure was driven by progressive tidal erosion that increased stresses at the base, and freeze-thaw cycles that gradually opened fractures at the base when salt water (marine) and at the top when fresh water (precipitation) reached their respective freezing points.
The forecast stability analyses of the Sentinel sea stack and Lovers’ Arch sea arch formations were completed using 3D finite element method geomechanics numerical models to assess the potential time to failure of the formations. Geometrical input was provided by unmanned aerial vehicle (UAV)-based 3D SfM photogrammetry models. Four scenarios were analyzed including the present (2021) geometry of the formations, as well as three simulated reductions in the widths of the pillar within the tidal erosion zone. The rates of erosion were determined to be approximately 3 to 6 mm per year by comparison of historic 20th century photographs and current (2021) photographs. The results from the numerical models in this study indicate that failure may occur in approximately 415 to 500 years after 2021 for the Sentinel formation, and 250 to 300 years after 2021 for the Lover’s Arch formation.
The results of this study are the first geomechanical interpretations of a past partial collapse and predictive stability analyses of sea stacks and arches at Hopewell Rocks Provincial Park. The analysis framework presented in this thesis can be applied to other coastal stack and arch formations and used to evaluate the risk of collapse to impact public safety and affect geotourism.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.