Rock Slope Geohazard Assessment and Mitigation to Protect People and Infrastructure

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Billions of dollars of new infrastructure will be built in steep terrain in Canada over the coming decade due to population growth and new natural gas, oil, and mining developments. People living or working near steep rock slopes and the associated infrastructure are exposed to geohazards. The long-term objectives of the research program are to improve geohazard assessment techniques and to build the missing links between geohazard assessment and the design of appropriate risk mitigation measures to reduce losses associated with rock falling from steep rock slopes. The short-term objectives address three deficiencies in the current risk management for steep rock slopes. Existing geohazard assessment methods can take too long and can expose geotechnical engineers doing the assessment to unsafe fieldwork. Overly simplistic geometric formulae (in current building codes) are used to define areas where it is safe to build; these formulae do not consider important factors such as the rock mass quality and the infrastructure vulnerability. New technologies such as slope meshing have been introduced in Canada but design methods are needed for specifying how these should be used.  The research objectives are to: 1) Improve assessment techniques for steep rock faces by using drones and by testing the effectiveness of various sensor packages on drones. A range of digital colour cameras will be compared with lidar sensors and an infrared camera. 2) Develop a rationale to determine setback distances that define safe locations for a structure on a lot by incorporating rock mass and slope geometry considerations as well as building vulnerability. A multi-criteria approach to calculation of setbacks will be a significant improvement over current practices. 3) Create design methodologies for slope stabilization with bolted mesh that advance beyond the currently used simple failure mechanism/loading assumptions by improving knowledge of fundamental support – rock mass interactions through numerical simulation of full-scale tests. Furthermore, the design will explicitly incorporate data that are now acquired in rock slope hazard rating systems, yet astonishingly, not used for support design purposes. The research on setback distances will lead to delineation of where it is safe to build, thus preventing construction of homes located too close to rock cuts for hillside residential development. For rock slopes along highways, railways, and in open pit mines, the research on design of rock stabilization with bolted mesh will save lives and reduce economic and environmental losses. The research using drones for rapid and safe characterization of cliffs above homes, highways, and railways will enable more rapid response and timely decisions about evacuations or reopening of transportation routes when slope instability occurs.