Rock-fall on:
[Wikipedia]
[Google]
[Amazon]
A rockfall or rock-fallWhittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984. . is a quantity/sheets of
Favourable geology and climate are the principal causal mechanisms of rockfall, factors that include intact condition of the rock mass, discontinuities within the rockmass, weathering susceptibility, ground and surface water, freeze-thaw, root-wedging, and external stresses. A tree may be blown by the wind, and this causes a pressure at the root level and this loosens rocks and can trigger a fall. The pieces of rock collect at the bottom creating a ''talus'' or '' scree''. Rocks falling from the cliff may dislodge other rocks and serve to create another mass wasting process, for example an avalanche.
A cliff that has favorable geology to a rockfall may be said to be incompetent. One that is not favorable to a rockfall, which is better consolidated, may be said to be competent.
In higher altitude mountains, rockfalls may be caused by thawing of rock masses with
Assessing the propagation of rockfall is a key issue for defining the best mitigation strategy as it allows the delineation of run out zones and the quantification of the rock blocks kinematics parameters along their way down to the elements at risk. In this purpose, many approaches may be considered. For example, the energy line method allows expediently estimating the rockfall run out. Numerical models simulating the rock block propagation offer a more detailed characterisation of the rockfall propagation kinematics. These simulation tools in particular focus on the modeling of the rebound of the rock block onto the soil The numerical models in particular provide the rock block passing height and kinetic energy that are necessary for designing passive mitigation structures.
Typically, rockfall events are mitigated in one of two ways: either by passive mitigation or active mitigation. Passive mitigation is where only the effects of the rockfall event are mitigated and are generally employed in the deposition or run-out zones, such as through the use of drape nets, rockfall catchment fences, galeries, ditches, embankments, etc. The rockfall still takes place but an attempt is made to control the outcome. In contrast, active mitigation is carried out in the initiation zone and prevents the rockfall event from ever occurring. Some examples of these measures are rock bolting, slope retention systems, shotcrete, etc. Other active measures might be by changing the geographic or climatic characteristics in the initiation zone, e.g. altering slope geometry, dewatering the slope, revegetation, etc.
Design guides of passive measures with respect to the block trajectory control have been proposed by several authors.Ritchie, A.M. (1963). ''Evaluation of rockfall and its control''. Highway Research Record, No. 17, pp. 13-28.Pierson, L.A., Gullixson C.F., Chassie R.G. (2001) Rockfall Area Design Guide. Final Report SPR-3(032), Oregon Department of Transportation and Federal Highway Administration, FHWA-OR-RD-02-04.Pantelidis, L. (2010). Rock catchment area design charts. In Proceedings of GeoFlorida 2010 (ASCE) Conference on Advances in Analysis, Modelling and Design (pp. 224-233).
A rockfall or rock-fallWhittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984. . is a quantity/sheets of rock
Rock most often refers to:
* Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids
* Rock music, a genre of popular music
Rock or Rocks may also refer to:
Places United Kingdom
* Rock, Caerphilly, a location in Wales ...
that has fallen freely from a cliff face. The term is also used for collapse of rock from roof or walls of mine or quarry workings. "A rockfall is a fragment of rock (a block) detached by sliding, toppling, or falling, that falls along a vertical or sub-vertical cliff, proceeds down slope by bouncing and flying along ballistic trajectories or by rolling on talus or debris slopes."
Alternatively, a "rockfall is the natural downward motion of a detached block or series of blocks with a small volume involving free falling, bouncing, rolling, and sliding". The mode of failure differs from that of a rockslide.
Causal mechanisms
Favourable geology and climate are the principal causal mechanisms of rockfall, factors that include intact condition of the rock mass, discontinuities within the rockmass, weathering susceptibility, ground and surface water, freeze-thaw, root-wedging, and external stresses. A tree may be blown by the wind, and this causes a pressure at the root level and this loosens rocks and can trigger a fall. The pieces of rock collect at the bottom creating a ''talus'' or '' scree''. Rocks falling from the cliff may dislodge other rocks and serve to create another mass wasting process, for example an avalanche.
A cliff that has favorable geology to a rockfall may be said to be incompetent. One that is not favorable to a rockfall, which is better consolidated, may be said to be competent.
In higher altitude mountains, rockfalls may be caused by thawing of rock masses with permafrost
Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface ...
. In contrast, lower altitude mountains with warmer climates rockfalls may be caused by weathering being enhanced by non-freezing conditions.
Propagation
Assessing the propagation of rockfall is a key issue for defining the best mitigation strategy as it allows the delineation of run out zones and the quantification of the rock blocks kinematics parameters along their way down to the elements at risk. In this purpose, many approaches may be considered. For example, the energy line method allows expediently estimating the rockfall run out. Numerical models simulating the rock block propagation offer a more detailed characterisation of the rockfall propagation kinematics. These simulation tools in particular focus on the modeling of the rebound of the rock block onto the soil The numerical models in particular provide the rock block passing height and kinetic energy that are necessary for designing passive mitigation structures.
Mitigation
Typically, rockfall events are mitigated in one of two ways: either by passive mitigation or active mitigation. Passive mitigation is where only the effects of the rockfall event are mitigated and are generally employed in the deposition or run-out zones, such as through the use of drape nets, rockfall catchment fences, galeries, ditches, embankments, etc. The rockfall still takes place but an attempt is made to control the outcome. In contrast, active mitigation is carried out in the initiation zone and prevents the rockfall event from ever occurring. Some examples of these measures are rock bolting, slope retention systems, shotcrete, etc. Other active measures might be by changing the geographic or climatic characteristics in the initiation zone, e.g. altering slope geometry, dewatering the slope, revegetation, etc.
Design guides of passive measures with respect to the block trajectory control have been proposed by several authors.Ritchie, A.M. (1963). ''Evaluation of rockfall and its control''. Highway Research Record, No. 17, pp. 13-28.Pierson, L.A., Gullixson C.F., Chassie R.G. (2001) Rockfall Area Design Guide. Final Report SPR-3(032), Oregon Department of Transportation and Federal Highway Administration, FHWA-OR-RD-02-04.Pantelidis, L. (2010). Rock catchment area design charts. In Proceedings of GeoFlorida 2010 (ASCE) Conference on Advances in Analysis, Modelling and Design (pp. 224-233).
Effects on trees
The effect of rockfalls on trees can be seen in several ways. The tree roots may rotate, via the rotational energy of the rockfall. The tree may move via the application of translational energy. And lastly deformation may occur, either elastic or plastic.Dendrochronology
Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
can reveal a past impact, with missing tree rings
Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmos ...
, as the tree rings grow around and close over a gap; the callus tissue can be seen microscopically. A macroscopic section can be used for dating of avalanche and rockfall events.
See also
* Avalanche * Earthquake * Kinetic energy *Landslide
Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...
* Potential energy
In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.
Common types of potential energy include the gravitational potentia ...
* Protection forest
* Rockslide
* Slope stability
* SMR classification
Slope mass rating (SMR) is a rock mass classification scheme developed by Manuel Romana to describe the strength of an individual rock outcrop or slope. The system is founded upon the more widely used RMR scheme, which is modified with quantitat ...
* Capitólio rockfall
References
External links
{{Authority control Road hazards Landslide types Hazards of outdoor recreation