Geotechnical design and construction methodology of structural elements on near vertical cliff faces

Unusual geotechnical challenges are faced when designing and constructing structures on near vertical cliff faces. On a recent project for a public climbing attraction, typical processes for geotechnical assessment and design, such as rock mass characterisation, stability hazard identification, rock dowel design and construction phase services required bespoke solutions and considerable forethought to overcome access limitations. This paper presents an overview of the geotechnical design, construction methodology, and verification process tailored for the development of multiple structural elements connected to the cliff face utilising rock dowels on near-vertical rock faces.

The design approach includes a thorough site investigation process, including geological mapping, rock mass characterisation, and hazard susceptibility zoning. Combining rope access assessments, unmanned aerial vehicle (UAV) based LIDAR (light detection and ranging) and digital imaging allowed for a detailed assessment of the stability and rock mass behaviour of the face at broad and local scales.

The proposed methodology comprises dividing the site into zones characterised by mass/material characteristics, hazard susceptibility, access similarities, structural constraints, and client priorities to optimise the concept design development. Special attention was given to analysing the complex interactions between structural elements and the surrounding rock mass to maintain long-term stability at multiple scales coupled with structural integrity.

The construction phase encompassed a staged approach, utilising advanced rope access drilling and anchoring techniques, and precision instrumentation for rock dowel testing. Collaboration between the asset owners, geotechnical engineers, structural designers, and construction professionals is emphasised throughout the program to address unforeseen challenges in the design and construction of the structures.