Two important steps can be recognised in the rockfall analysis: the potential failure detection and the run out simulation. Analyzing the stability of rock slopes, most important kinematisms are slidings (planar or wedge) and topplings. r.rock.stability is a module that allows users to apply geomechanical classifications (SMR and SSPC) for the preliminary assessment of the susceptibility of rock slopes to failures induced by these kinematisms.
SMR approach (default):SMR (Slope Mass Rating) is a widely used geomechanical classification developed by Romana (1995). The final SMR rating is obtained by means of next expression: SMR=RMRb+(F1*F2*F3)+F4 where:
r.rock.stability calculate F1, F2 and F3 index by combining DEM (slope and aspect) and joint dip and dip direction.
F1, F2 and F3 are calculated according two functions of Romana (1995) and of Tomàs et al. (2007). The functions proposed by Romana are discrete, instead Tomàs et al. (2007) proposed continuous functions that reduced subjective interpretations.
SSPC approach (optional): inserting TC value (or a map of TC values) it's possible to obtain a SSPC map according to Hack's classification (Hack, 1998). Only a part of the method introduced by Hack is used in the module: the orientation dependent stability (the stability depend on relation between slope and discontinuity orientation). According to the author:
where AP is the apparent dip, TC is the condition factor for a discontinuity. TC can be calculated by multiplying the large scale roughness, the small scale roughness, the infill material and the karst factors observed in the field:
TC=Rl Rs Im Ka.
Rl (roughness in large scale - area between 0,2x0,2 m2 and 1x1 m2)
Rs (roughness in small scale - area of 0,2x0,2m2):
Im (Infill material)
NOTE: high pixel values indicate high susceptibility
SMR wedge (optional): inserting dip and dip direction it's possible to calculate the SMR index of wedge.
Digital Elevation Model = name
Dip direction = string
Dip = string
F4 = string
RMR = string or map
TC (optional) = string or map
Output prefix = name
r.rock.stability generates 3 raster maps of SMR (prefix_toppling; prefix_planar; prefix_wedge;) values distribution according to mechanism: planar sliding, toppling and wedge (if optional dip and dip direction is inserted).
|SMR classes||SMR values||Suggest supports|
|Ib||81-90||None, scaling is required|
|IIa||71-80||(None, toe ditch or fence), spot bolting|
|IIb||61-70||(Toe ditch or fence nets), spot or systematic bolting|
|IIIa||51-60||(Toe ditch and/or fence nets), spot or systematic bolting, spot shotcrete|
|IIIb||41-50||(Toe ditch and/or fence nets), spot or systematic bolting/anchor, toe wall and/or dental concrete|
|IVa||31-40||Anchor systematic shotcrete, toe wall and/or dental concrete (or re-excavation), drainage|
|IVb||21-30||Systematic reinforced shotcrete, toe wall and/or concrete, re-excavation, deep drainage|
|Va||11-20||Gravity or anchored wall, re-excavation|
BIENIAWSKI Z.T. (1989). Engineering Rock Mass Classifications. John Wiley and Sons: New York.
FILIPELLO A., GIULIANI A., MANDRONE G. (2010) - Rock Slopes Failure Susceptibility Analysis: From Remote Sensing Measurements to Geographic Information System Raster Modules. American Journal of Environmental Sciences 6 (6): 489-494, 2010 ISSN 1553-345X © 2010 Science Publications.
HACK HRGK (1998) Slope stability probability classification, SSPC, 2nd edn. ITC, Enschede, The Netherlands, 258 pp, ISBN 90 6164 154 3
ROMANA M. (1995). The geomechanical classification SMR for slope correction. Proc. Int. Congress on Rock Mechanics 3: 1085-1092.
TOMÀS, R., DELGADO, J.,SERON, J.B. (2007). Modification of slope mass rating(SMR) by continuous functions. International Journal of Rock Mechanics and Mining Sciences 44: 1062-1069.
Andrea Filipello, University of Turin, Italy
Daniele Strigaro, University of Milan, Italy
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