GRASS GIS manual: r.rock.stability

NAME

r.rock.stability - A tool for preliminary rock failure susceptibility mapping.

KEYWORDS

SYNOPSIS

r.rock.stability

r.rock.stability --help

r.rock.stability dem=string imme=integer incl=integer f4=string rmr=string prefix=string [tc=float] [imme2=integer] [incl2=integer] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

--overwrite: Allow output files to overwrite existing files
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

dem=string [required]: Dtm of the zone
imme=integer [required]: Dip direction of the joint (0-360); Options: 0-360
incl=integer [required]: Dip of the joint (0-90); Options: 0-90
f4=string [required]: F4 index; Options: Natural Slope +15, Pre-splitting +10, Smooth blasting +8, Normal blasting or mechanical excavation 0, Poor blasting -8
rmr=string [required]: RMR index
prefix=string [required]: Prefix for output maps
tc=float: Total Condition of joint, for SSPC output; Options: 0.018975 - 1.0165
imme2=integer: Dip direction of the joint (0-360). For SMR_wedge output; Options: 0-360
incl2=integer: Dip of the joint (0-90). For SMR_wedge output; Options: 0-90

DESCRIPTION
INPUT
OUTPUT
REFERENCES
SEE ALSO
AUTHORS

DESCRIPTION

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:

RMRb is the RMR index resulting from Bieniawski's Rock Mass Classification (1989)
F1 depends on the parallelism between discontinuity and slope dip direction
F2 depends on the discontinuity dip in the case of planar failure and the plunge, or of the intersection line in wedge failure. As regards toppling failure, this parameter takes the value 1.0
F3 depends on the relationship between slope and discontinuity dips (toppling or planar failure cases) or the immersion line dip (wedge failure case)
F4 is a correction factor that depends on the excavation method used:

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:

sliding occurs if: TC < 0,0113*AP
toppling occurs if: TC < 0,0087*(-90-AP+dip)

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)

1,00 Wavy
0,95 Slightly wavy
0,85 Curved
0,80 Slightly curved
0,75 Straight

Rs (roughness in small scale - area of 0,2x0,2m2):

0,95 Rough stepped
0,90 Smooth stepped
0,85 Polished stepped
0,80 Rough undulating
0,75 Smooth undulating
0,70 Polished undulating
0,65 Rough planar
0,60 Smooth planar
0,55 Polished planar.

Im (Infill material)

Cemented --> Infill (1,07), No Infill (1,00)
Non softening and sheared material e.g. free of clay, talc, etc --> Coarse (0,95) Medium (0,90) Fine (0,85)
Soft sheared material e.g. clay, talc, etc --> Coarse (0,75) Medium (0,65) Fine (0,55)
Gouge < irregularities (0,42); Gouge > irregularities (0,17); flowing material (0,05)

Ka (karst):

1,00 None
0.92 Karst

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.

INPUT

Digital Elevation Model = name

Name of elevation raster map

Dip direction = string

Value of the direction of the discontinuity measured clockwise starting from North. North is 0° or 360°, East (90°). South (180°), West (270°)

Dip = string

Angle of inclination of the discontinuity relative to a horizontal plane.

F4 = string

Correction factor according to Romana's classification

RMR = string or map

Value of RMRb according to Bieniawski's classification

TC (optional) = string or map

Value of TC according to Hack's classification

Output prefix = name

Name of prefix used for output raster maps

OUTPUT

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

Ia 91-100 None

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

SMR classes	SMR values	Suggest supports
Ia	91-100	None
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

REFERENCES

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.

AUTHORS

Andrea Filipello, University of Turin, Italy

Daniele Strigaro, University of Milan, Italy

SOURCE CODE

Available at: r.rock.stability source code (history)