Stratégies de caractérisation morpho-structurale des instabilités apparentes des parois rocheuses par LiDAR 3D en carrière urbaine

Abstract

Excavated rock walls in urban environments may exhibit deterioration conditions that are difficult to characterize because of their complex geometry and limited accessibility. In this context, high-resolution three-dimensional models provide a relevant means of documenting the visible morphological and structural characteristics of the rock mass. This thesis proposes an integrated strategy for the morpho-structural characterization of apparent rock wall instabilities using 3D LiDAR data, applied to Francon Quarry in Montréal. The site, which is used for snow and granular material storage, includes high rock walls and several operational configurations. The objective is to identify, map, quantify, and interpret visible features that provide information on the apparent condition of the rock mass, without equating them with a probability of failure, a factor of safety, or an absolute measure of risk. The methodology is based on the processing of 3D models produced from LiDAR and photogrammetric surveys. Structural and kinematic analyses were used to identify bedding, the principal discontinuity sets, and geometrically admissible failure mechanisms. Mapped features were quantified from classified point counts and normalized to compare operational contexts having unequal spatial extents. Nine morphological classes were defined and subsequently grouped into three dominant functions: direct material release, structural predisposition, and progressive degradation. The results reveal contrasting signatures ranging from strong structural predisposition to diffuse progressive degradation, together with localized features associated with material release. A comparative apparent geohazard profile was developed for point dumping platforms, the extended dumping platform, and sectors without direct dumping. Point platforms exhibit a predominantly structural signature accompanied by a substantial progressive-degradation component. The extended platform is dominated by altered surfaces and seepage, whereas sectors without direct dumping display a more diverse signature and a notable contribution from direct-release features. The proposed approach therefore provides a decision-support tool for the characterization, comparison, and monitoring of rock walls, while maintaining a clear distinction between morphological observation, geomechanical interpretation, and risk assessment.

Date	7 Sept 2026
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Jonathan D. Aubertin (Supervisor)