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

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Oct 02, 2022 296 likes •376 views

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

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| | Master in Engineering Geology

Analysis of the impact of exfoliation fracturing on rock fall hazards in the Upper Aar Valley

Martin Ziegler, Simon Löw

17/02/2015 Master topic proposals 1

Rock fall hazard

| | Master in Engineering Geology 17/02/2015 Rockfall hazard 2

Similarly in Aar Granites in Switzerland..

SLIDE 2

| | Master in Engineering Geology 17/02/2015 Rockfall hazard 3

Similarly in Aar Granites in Switzerland..

| | Master in Engineering Geology 17/02/2015 Rockfall hazard 4

Similarly in Aar Granites in Switzerland..

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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?

| | Master in Engineering Geology 17/02/2015 Rockfall hazard 6

Project location

Upper Aar Valley (Swiss Alps)

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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

| | Master in Engineering Geology 17/02/2015 Rockfall hazard 8

Site Geology and Exfoliation Fracture Sets

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Glacial and Fluvial Morphologies

steep ridges (showing cirques, trimlines)
gently-inclined, ~linear upper valley slopes
steep inner-valley troughs
steep V-shaped gullies at the sides of

trough valleys

steep ridges (showing cirques, trimlines)
gently-inclined, ~linear upper valley slopes
steep inner-valley troughs

| | Master in Engineering Geology 17/02/2015 Rockfall hazard 10

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

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| | Master in Engineering Geology 17/02/2015 Rockfall hazard 11

Your field site in summer / fall 2015 ?

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