Rock fall hazard Analysis of the impact of exfoliation fracturing on - PDF document

Rock fall hazard Analysis of the impact of exfoliation fracturing on rock fall hazards in the Upper Aar Valley Martin Ziegler, Simon Löw Master topic proposals | 17/02/2015 | 1 Master in Engineering Geology Similarly in Aar Granites in Switzerland.. | | Rockfall hazard 17/02/2015 2 Master in Engineering Geology

Similarly in Aar Granites in Switzerland.. Rockfall hazard | 17/02/2015 | 3 Master in Engineering Geology Similarly in Aar Granites in Switzerland.. | | Rockfall hazard 17/02/2015 4 Master in Engineering Geology

Project framework  Glacial erosion and retreat produce steep landforms prone to rock fall  Rock fall is a major force shaping landscapes and can be hazardeous  Time-dependant weathering processes and fracture propagation loosen rock blocks and promote detachment  Some observations in alpine valleys emphasise the role of stress redistribution and fracturing, i.e., exfoliation fractures, as an important cause in weakening rock slopes  What is the relationship between morphological forms, age of surface exposure, rock mass fracturing and rock fall activity? Rockfall hazard | 17/02/2015 | 5 Master in Engineering Geology Project location Upper Aar Valley (Swiss Alps) | | Rockfall hazard 17/02/2015 6 Master in Engineering Geology

Exfoliation Joints (Sheeting joints) Definition Joints that formed subparallel to the present or a former erosional surface Some characteristics  restricted in occurrence up to ~200 m bgs.  increasing joint spacing with depth  younger than tectonic joints or faults  occur worldwide in different rock types Rockfall hazard | 17/02/2015 | 7 Master in Engineering Geology Site Geology and Exfoliation Fracture Sets | | Rockfall hazard 17/02/2015 8 Master in Engineering Geology

Glacial and Fluvial Morphologies   steep ridges (showing cirques, trimlines) steep ridges (showing cirques, trimlines)   gently-inclined, ~linear upper valley slopes gently-inclined, ~linear upper valley slopes   steep inner-valley troughs steep inner-valley troughs  steep V-shaped gullies at the sides of trough valleys Rockfall hazard | 17/02/2015 | 9 Master in Engineering Geology Goals A. Correlation between rock fall areas and local fracture patterns , with focus on exfoliation fracturing B. Better understanding of the relationship between topographic form, age of surface exposure, and rock fall activity Tasks A. Identification and mapping rock fall release areas and deposits  Assessment of rock fall volumes, fracture properties and rock mass strength  Glacially eroded surfaces (glacial polish, striae and friction cracks, rock surface exposure ages)  How? New field observations, aerial photo interpretation, analysis of photogrammetric models and laser remote sensing, analysis of existing data (e.g., exposure ages) B. Analysis of factors promoting rock fall activity from identified release areas  Investigation of patterns in the spatial distribution of rock fall release areas → with respect to rock mass discontinuities, morphological setting, most likely event age | | Rockfall hazard 17/02/2015 10 Master in Engineering Geology

Your field site in summer / fall 2015 ? Rockfall hazard | 17/02/2015 | 11 Master in Engineering Geology Your field site in summer / fall 2015 ? | | Rockfall hazard 17/02/2015 12 Master in Engineering Geology