Case study on Snowy 2.0, Australia: use of LiDAR and endoscopy for assessing and modelling geological features in underground caverns

Snowy 2.0 is a major pumped hydropower project currently under construction in Australia that will complement the existing Snowy Mountains hydroelectric system, adding an additional 2200 MW to the national energy grid. The Power Station Complex (PSC) for the project comprises 3 caverns, a shaft, and some 10 km of Drill and Blast excavated tunnels, at a depth of over 750m. The Machine and Transformer halls within the PSC are excavated using an observational approach to excavation, requiring a thorough understanding of encountered conditions and excavation behaviour.

Traditional mapping techniques in tunnels face challenges due to limited accessibility and visibility. This case study describes the use of survey controlled Light Detection and Ranging (LiDAR) scans of the excavated face to augment traditional mapping, used together with downhole endoscopy and optical televiewer (OTV) to identify and project major defects in 3D modelling softwares. Integrating these technologies has allowed for comprehensive defect detection, persistence and waviness assessments on the cavern scale, and accurate orientation measurements which can be combined with defect conditions assessed in traditional mapping. This is key in the observational approach to excavation, providing a highly accurate geological model which allows a verification of design assumptions, comparison of geological features to monitoring, highlighting areas where bolt shear may be of concern, and ensuring a comprehensive and accurate owners model for the operations phase of the scheme.