Discontinuity survey and brittle fracture characterisation in open pit slopes using photogrammetry

Author(s): 
Zack Tuckey, Justine Paul and Jeff Price
Date: 
Monday, October 10, 2016
First presented: 
Asia Pacific Slope Stability in Mining Conference, Brisbane, Septmeber 6-9
Type: 
Presentation
Category: 
Geotechnical

Remote sensing techniques such as ground-based photogrammetry and LiDAR have become routine supplements to traditional rock mass characterisation approaches, greatly enhancing discontinuity survey capability. Concurrently, discrete fracture network simulations, constructed using field discontinuity mapping data, are increasingly being applied to advanced numerical modelling studies of rock slope stability, leading to improved understanding of progressive slope failure involving brittle fracture initiation, propagation, and coalescence. Despite continuing technological advances, predictive modelling of rock slope stability is still limited by our inability to observe the hidden interior structure of a rock mass, and by computational limitations restricting the explicit simulation of small scale material heterogeneity and localisation phenomena inherent to brittle fracture.

We present discontinuity mapping observations from a photogrammetry investigation of an Australian open pit slope, with emphasis on the influence of survey scale and resolution on discontinuity characterisation. We also discuss the application of fractography principles to interpretation of brittle rock mass damage, focussing on characterisation of irregular brittle fractures induced by blasting, and on incipient discontinuities which retain cohesion and tensile strength from intact rock bridges. Based on the results, we make recommendations for improving photogrammetry-based discontinuity mapping procedures, in order to improve collection of both quantitative data on discontinuity persistence and intensity, and also qualitative characterisation of rock mass damage in open pit slopes.

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