Horizontal single hole blast testing – Part 2: Field observations and experimental trends from SHB campaigns at two underground salt mines

• Published in: Tunnelling and underground space technology 2021-08, Vol.114, p.103984, Article 103984
• Main Authors: Aubertin, Jonathan D., Hutchinson, D. Jean, Diederichs, Mark
• Format: Article
• Language: English
• Subjects: Craters; Geometry; Lasers; LiDAR; Point cloud processing; Rock blasting; Rock salt; Rocks; Salt mines; Sensors; Single hole blast test; Terrestrial Laser Scanning (TLS); Trends; Underground mines; Underground mining
• ISSN: 0886-7798; 1878-4364
• DOI: 10.1016/j.tust.2021.103984

•Full scale underground blastability investigation via single hole blast tests.•Semi-automated point cloud processing for single hole blast results analysis.•Detailed 3D mapping of blasted crater to capture complete breakout shape.•Burden dependent model to describe non-prismatic cratering behavior.•Applications of single hole blast crater to full face blast design considerations. This results presented in this paper follow the basic principles and methodology developed for horizontal Single Hole Blast (SHB) testing using terrestrial laser scanning (TLS), introduced in Part 1, and shows specific SHB test applications as a mean to investigate rock blasting behavior. Part 1 introduced a detailed procedure for consistent and systematic SHB testing to provide the means for reproducible and comparable data collection and characterization. The concept of crater breakout angle was expanded to account for the observed non linear shape, based on measurements made at small increments along the blasthole to capture variability of the overall geometry. This paper describes SHB testing campaigns conducted at two underground salt mines. Traditional reporting parameters (e.g. breakout angle, crater area) are presented in an enhanced approach by capturing their variation along the blasthole, and with respect to measured burden dimensions. A new crater model is proposed to better capture and represent the observed crater shape, and avoid the simplification of best-fitting triangular crater shapes. Results from the field campaigns are presented in details using LiDAR point clouds and SHB characteristic plots of the crater geometry. The crater model is calibrated from the test results to obtain site-specific burden-dependent trends of the crater shape. Two methods are then proposed for implementing SHB test results into blast pattern designs using the proposed crater model.