Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD
Slope stability classification
Weathering
Robert Hack
Engineering Geology, ESA, Faculty of Geoinformation
Science and Earth Observation (ITC)
University Twente, The Netherlands
Duluth, Minnesota, USA, 17 May 2011
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD
Rock Quality Designation
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Drill core measures
Total Core Recovery
∑ total length of core
TCR =
* 100 %
total length drilled
Solid Core Recovery
∑ length pieces of solid core
SCR =
* 100 %
total length drilled
(after Price et al. 2009. Engineering
Geology. Publ. Springer, Germany)
Rock Quality Designation
∑ length pieces of intact core with length (*) > 10 cm
* 100 %
total length drilled
*) along centre line of core
SCR & RQD : Obvious drilling breaks to be excluded ( pieces should
be fitted together and counted as one piece)
RQD =
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD (Rock Quality Designation)
Originally:
A rock mass classification system (Deere, 1964)
- Depending on the RQD only a rock mass quality was
assigned to a rock mass
<25% - Very Poor; 25-50% - Poor; 50-75% - Fair; 75-90% - Good; 90-100% -Excellent
This function of the RQD is not used anymore
RQD at present:
A standard in borehole core description
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD (Rock Quality Designation)
RQD at present:
- A standard in borehole core description
And used in:
- rock mass classification schemes for tunnels, slopes, etc. (Qsystem, RMR, SMR, etc)
- excavatability classifications
- rock mass strength (RMR)
- rock mass permeability
- etc., etc., etc.
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD (Rock Quality Designation)
RQD at present:
Probably the most popular rock mass parameter
Used for virtually everything
Is this justified…………………
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Problems with RQD (1)
1. Arbitrary length of 10 cm
2. Orientation of borehole in relation with discontinuity
spacing
spacing discontinuities 0.09 m
horizontal
borehole
RQD = 0 %
horizontal
borehole
RQD = 100 %
vertical borehole RQD = 0 %
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Problems with RQD (2)
3. Weak rock pieces (weathered pieces of rock or infill
material) that are not sound should not be considered for
determining the RQD (Deere et al., 1967, 1988). To
exclude infill material will usually not be too difficult;
however, excluding pieces of weathered, not sound rock
is fairly arbitrary.
4. The RQD value is influenced by drilling equipment,
drilling operators and core handling. Especially RQD
values of weak rocks can be considerably reduced due to
inexperienced operators or poor drilling equipment.
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Problems with RQD (3)
5. No standard core barrel - single, double, or triple barrel ?
6. Diameter of boreholes
7. Drilling fractures should be re-fitted, but what are drilling
fractures?
8. RQD should be determined per lithology, but where is the
lithology boundary if washed away?
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD without borehole (Palmstrøm, 1)
Jv = the volumetric discontinuity count
= total number of discontinuities per m3
= the sum of the number of discontinuities
per metre length of all discontinuity sets
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD without borehole (Palmstrøm, 2)
IF J v ≥ 4.5 ===> RQD = ( 115 - 3.3 * J v ) %
IF J v < 4.5 ===> RQD = 100 %
3
=
total
number
of
discontinu
ities
per
Jv
m
(= sum of number of discontinuities per metre
length of all discontinuity sets)
(ISRM, 1978, Palmstrøm,1975)
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
bedding planes: spacing 0.4 m
Joint 2: spacing 1.0 m
Joint 1: spacing 3.0 m
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD without borehole (Palmstrøm, 3)
Example1:
Bedding spacing 0.4 m = 2.5 discontinuity per meter
Joint 1 spacing = 3.0 m = 0.33 discontinuity per meter
Joint 2 spacing = 1.0 m = 1 discontinuity per meter
Jv = 2.5 + 0.33 + 1 = 3.83 discontinuities per m3
JV < 4.5
RQD = 100 %
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
foliation planes: spacing 0.3 m
Joint 2: spacing 0.4 m
(perpendicular to slope)
Joint 1: spacing 0.4 m
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD without borehole (Palmstrøm, 3)
Example 2:
Foliation spacing 0.3 m = 2.5 discontinuity per meter
Joint 1 spacing = 0.4 m = 2.5 discontinuity per meter
Joint 2 spacing = 0.4 m = 3.3 discontinuity per meter
Jv = 2.5 + 2.5 + 3.3 = 8.3 discontinuities per m3
JV > 4.5
RQD = (115 – 3.3 * Jv) = 88 %
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RQD without borehole (Palmstrøm, 3)
More complicated and sophisticated relations exist for RQD
without a bore hole
However: It will always be a simulation
RQD is inherent to the process of drilling
Without drilling some features determining the RQD are lost
such as: washing out weak layers, fractures due to drilling, etc.
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Rock mass
classification systems
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Classification systems are empirical relations
that relate rock mass properties either directly or
via a rating system to an engineering
application, e.g. slope, tunnel
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
For example in the RMR system:
• properties (such as RQD, intact rock strength,
spacing of discontinuities) of the rock mass
are given point ratings
• the points are added to give the RMR rating
the RMR rating is related to:
• the stability of the tunnel
• support measures in the tunnel (e.g. shotcrete,
rock bolts, steel sets)
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RMR:
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
RMR example:
• IRS = 75 MPa: 7 points
• RQD = 80% 17 points
• discontinuity spacing = 45 cm 10
points
• condition: slightly rough, separation <
1 mm, slightly weathered walls 25
points
• groundwater = dry 15 points
RMR rating = 7 + 17+ 10 + 25 + 15 = 74 points
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Classification systems:
• For underground (tunnel):
• Bieniawski (RMR)
• Barton (Q)
• Laubscher (MRMR)
• etcetera
• For slopes:
• Selby
• Bieniawski (RMR)
• Vecchia
• Robertson (RMR)
• Romana (SMR)
• Haines
• SSPC
• etcetera
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Classification systems for slopes
• Romana’s SMR
• Haines and Terbrugge
• SSPC
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Romana’s SMR
SMR = RMR - ( F 1 * F 2 * F 3 ) + F 4
SMR = Slope Mass Rating
RMR = Rock Mass Rating (same as Bieniawski' s RMR)
F 1 = factor for parallelism of the strikes of
discontinuities and slope face
F 2 = factor for discontinuity dip angle
F 3 = factor for relation between slope face and discontinuity dip
F 4 = factor for method of excavation
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Haines and Terbrugge slope
system
280
factor
40 safety =
1 2 45
factor
30 safety =
15
35
marginal on
classification alone
40
240
slope height (m)
200
additional analysis
required
50
55
60
45
160
65
50
70
55
120
80
75
60
classification alone
may be adequate
80
65
70
40
75
0
0
10
20
30
40
50
60
70
80
90
100
MRMR
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
SSPC failure probabilities for
orientation independent failure
10
Das hed pr obability lines indi c ate that the number of sl opes us ed for
the devel opment of the SSPC s ys tem for thes e s ec tions of the
graph is limited and the pr obability lines may not be as c ertai n as
the pr obability lines dr awn with a conti nuous line.
95 %
H max / Hslope
probability to be stable > 95 %
90 %
70 %
50 %
30 %
1
10 %
5%
(example)
probability to be stable < 5 %
0.1
0.0
0.2
0.4
0.6
ϕ’mass / slope dip
17 May 2011
0.8
1.0
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Slope Stability probability
Classification (SSPC)
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
SSPC
• three step classification system
• based on probabilities
• independent failure mechanism assessment
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Three step classification system
(1)
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Three step classification system (2)
EXPOSURE ROCK MASS (ERM)
Exposure rock mass parameters significant for slope stability:
• Material properties: strength, susceptibility to weathering
• Discontinuities: orientation and sets (spacing) or single
• Discontinuity properties: roughness, infill, karst
Exposure specific parameters:
• Method of excavation
• Degree of weathering
Factor used to remove the influence of the
method excavation and degree of weathering
REFERENCE ROCK MASS (RRM)
Reference rock mass parameters significant for slope stability:
• Material properties: strength, susceptibility to weathering
• Discontinuities: orientation and sets (spacing) or single
• Discontinuity properties: roughness, infill, karst
Slope specific parameters:
• Method of excavation to be used
• Expected degree of weathering at
end of engineering life-time of slope
Factor used to assess the influence of the
method excavation and future weathering
SLOPE GEOMETRY
Orientation
Height
SLOPE ROCK MASS (SRM)
Slope rock mass parameters significant for slope stability:
• Material properties: strength, susceptibility to weathering
• Discontinuities: orientation and sets (spacing) or single
• Discontinuity properties: roughness, infill, karst
SLOPE STABILITY ASSESSMENT
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Excavation specific parameters for
the excavation which is used to
characterize the rock mass
• Degree of weathering
• Method of excavation
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Slope specific parameters for the
new slope to be made
• Expected degree of weathering at end of
lifetime of the slope
• Method of excavation to be used for the new
slope
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Intact rock strength
By simple means test - hammer blows, crushing
by hand, etc.
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Spacing and persistence of
discontinuities
Based on the block size and block form by
first visual assessment and then quantification
of the characteristic spacing and orientation
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
amplitude roughness:
≈ 5 – 9 cm
wavy
i = 14 - 20°
≈ 5 – 9 cm
slightly wavy
i = 9 - 14°
≈ 3.5 – 7 cm
i = 4 - 8°
curved
slightly curved
≈ 1.5 – 3.5 cm
Shear
strength roughness
large scale
i = 2 - 4°
straight
≈1m
(i-angles and dimensions only approximate)
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
stepped
undulating
amplitude roughness > 2 - 3 mm
amplitude roughness > 2 - 3 mm
Shear
strength roughness
small scale
planar
≈ 0.20 m
(dimensions only approximate)
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Shear strength - Infill
Infill:
•
cemented
•
no infill
•
non-softening (3 grain sizes)
•
softening (3 grain sizes)
•
gauge type (larger or smaller than roughness
amplitude)
•
flowing material
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Orientation dependent stability
Stability depending on relation between slope
and discontinuity orientation
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Sliding criterion
sliding occurs if :
TC < 0.0113 * AP
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Sliding probability
95 %
70 %
50 %
30 %
5%
TC (condition of discontinuity)
1.00
discontinuity stable
with respect to sliding
0.80
0.60
discontinuity unstable
with respect to sliding
0.40
0.20
0.00
0
10
20
30
40
50
60
70
80
90
AP (deg)
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Toppling criterion
TC < 0.0087 * (− 90° − AP + dipdiscontinuity )
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Toppling probability
TC (condition of discontinuity) (-)
1.00
95 %
70 %
50 %
30 %
discontinuity stable
with respect to toppling
0.80
Fig. 9. Toppling criterion.
5%
0.60
0.40
discontinuity unstable
with respect to toppling
0.20
0.00
0
10
20
30
40
50
60
70
80
90
- 90 - AP + slope dip (deg)
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Orientation independent stability
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Probability orientation independent failure
10
Das hed pr obabilit y lines indi c at e that the number of sl opes us ed f or
the devel opment of the SSPC s ys tem f or t hes e s ec tions of the
graph is limited and the pr obability lines may not be as c ert ai n as
the pr obability lines dr awn wit h a conti nuous line.
95 %
H max / Hslope
probability to be stable > 95 %
90 %
70 %
50 %
30 %
1
10 %
5%
(example)
probability to be stable < 5 %
0.1
0.0
0.2
0.4
0.6
ϕ’mass / slope dip
17 May 2011
0.8
1.0
2011-05-17 - RQD classification weathering - Robert Hack
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80
80
visually estimated stability
visually estimated stability
Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
stable (class 1)
stable (class 1)
unstable (class 2)
unstable (class 2)
unstable (class 3)
unstable (class 3)
60
b: Haines
60
number of slopes (%)
number of slopes (%)
a: SSPC
Haines safety factor: 1.2
Comparison
40
20
40
20
0
0
<5
7.5
15
25
35
45
55
65
75
85
92.5
> 95
-45
SSPC stability probability (%)
stable
number of slopes (%)
60
-10
-5
5
15
25
35
45
unstable
stable
Percentages are from total number of slopes
per visually estimated stability class.
visually estimated stability
stable (class 1)
unstable (class 2)
unstable (class 3)
c: SMR
-25
Haines' slope dip - existing slope dip (deg)
unstable
80
-35
visually estimated stability:
class 1 : stable; no signs of present or future slope
failures (number of slopes: 109)
class 2 : small problems; the slope presently shows
signs of active small failures and has the potential for
future small failures (number of slopes: 20)
class 3 : large problems; The slope presently shows
signs of active large failures and has the potential for
future large failures (number of slopes: 55)
40
20
0
5
15
completely
unstable
25
35
45
55
65
75
Romana's SMR (points)
'tentative' describtion of SMR classes:
partially
unstable
stable
stable
85
95
completely
stable
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Poorly blasted slope
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Poorly blasted slope
New cut (in 1990):
Visual assessed: extremely poor instable.
SSPC stability < 8% (13.8 m high, dip 70°, rock mass weathering:
'moderately' and 'dislodged blocks' due to blasting).
Forecast in 1996: SSPC stability: slope dip 45°.
In 2002: Slope dip about 55° (visually assessed unstable).
In 2005: Slope dip about 52° (visually assessed unstable – big blocks
in middle photo have fallen).
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Slope Stability probability
Classification (SSPC)
Saba case - Dutch Antilles
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Landslide in harbour
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Geotechnical zoning
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
SSPC results
Pyroclastic deposits
Rock mass friction
Rock mass cohesion
Calculated maximum
possible height on the
slope
Calculated SSPC
35°
39kPa
13m
17 May 2011
Laboratory / field
27° (measured)
40kPa (measured)
15m (observed)
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Failing slope in Manila, Philippines
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Failing slope in
Manila (2)
• tuff layers with near horizontal weathering horizons
(about every 2-3 m)
• slope height is about 5 m
• SSPC non-orientation dependent stability about 50%
for 7 m slope height
• unfavourable stress configuration due to corner
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Widening existing
road in Bhutan
(Himalayas)
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Bhutan (5)
Method of
excavation
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Widening
existing road in
Bhutan
(Himalayas) (2)
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Widening existing road in
Bhutan (Himalayas) (3)
Above road level:
Visual assessment:
• Joint systems (sub-) vertical
• Present slope about 21 m high, about 90° or overhanging (!)
• Present situation above road highly unstable (visual assessment)
Following SSPC system:
• highly instable
• stability for: 27 m slope with 75° slope dip (orientation
independent stability 85%)
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Future degradation (2)
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Future degradation (3)
3.5
z [m]
3.0
2.5
2.0
1.5
1.0
7.0
7.5
8.0
Excavated 1999
8.5
9.0
y [m]
May 2001
9.5
May 2002
Reduction in slope angle due to weathering, erosion and ravelling (after Huisman)
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Weathering rate
WE ( t ) =
WEinit − R
app
WE
log (1 + t )
WE(t) = degree of weathering at time t
WEinit = (initial) degree of weathering at time t = 0
RappWE = weathering intensity rate
WE as function of time, initial weathering and the
weathering intensity rate
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2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Degradation processes
•
•
•
Main processes involved in degradation:
Loss of structure due to stress release
Weathering (In-situ change by inside or outside
influences)
Erosion (Material transport with no chemical or
structural changes)
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Significance in engineering
• When rock masses degrade in time, slopes
and other works that are stable at present may
become unstable
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
64
Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
65
Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Weathering rates
•Material:
Gypsum layers
Gypsum cemented siltstone layers
Middle Muschelkalk near Vandellos (Spain)
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Weathering intensity rate
SSPC system with applying weathering
intensity rate:
- original slope cut about 50º (1998)
- in 15 years decrease to 35º
17 May 2011
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Kota Kinabalu, Malaysia
Main road: 10 years old
moderately weathered
SSPC
stability:
Sandstone:
stable
Shale:
ravelling
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
68
Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Kota Kinabalu, Malaysia
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
69
Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Kota Kinabalu,
Malaysia
Side road: 5 years old
slightly weathered
SSPC
stability:
Sandstone:
stable
Shale:
unstable
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
Kota Kinabalu,
Malaysia
SSPC friction & cohesion:
friction (deg)
cohesion (kPa)
shale
slightly (5 years)
moderately (10 years)
4
2
2.4
1.1
sandstone
slightly (5 years)
moderately (10 years)
20
11
10.0
6.3
17 May 2011
2011-05-17 - RQD classification weathering - Robert Hack
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Hack, R., 2011. RQD; Slope stability classification; Weathering. In: Engineering Geology Course, Duluth, Minnesota, USA, 17 May 2011. ITC, Enschede, The Netherlands. 72 slides.
References
Barton N.R., Lien R. & Lunde J. (1974). Engineering Classification of Rock Masses for the Design of Tunnel
Support. Rock Mechanics. 6. publ. Springer Verlag. pp.189 - 236.
Barton N.R. (2000) TBM Tunnelling in Jointed and Faulted Rock. Published by Taylor & Francis, 2000
Bieniawski Z.T. (1989). Engineering Rock Mass Classifications. publ. Wiley, New York. 251 pp.
ISBN 9058093417, 9789058093417. 184 pp.
Hack HRGK, Price, D & Rengers N (2003) A new approach to rock slope stability - a probability classification
(SSPC). Bulletin of Engineering Geology and the Environment. Springer Verlag. Vol. 62: article: DOI
10.1007/s10064-002-0155-4. pp. 167-184 & erratum: DOI 10.1007/s10064-002-0171-4. pp 185-185
Haines A. & Terbrugge P.J. (1991). Preliminary estimation of rock slope stability using rock mass classification
systems. Proc. 7th Cong. on Rock Mechanics. ISRM. Aachen, Germany. 2, ed. Wittke W. publ. Balkema,
Rotterdam. pp. 887 - 892.
Huisman M, Hack HRGK & Nieuwenhuis JD (2006) Predicting rock mass decay in engineering lifetimes: the
influence of slope aspect and climate. Environmental & Engineering Geoscience. Vol XII, no. 1, Feb. 2006,
pp. 49-61.
ISRM (1978). Suggested methods for the quantitative description of discontinuities in rock masses. Int. Journal
Rock Mechanics, Mining Sciences & Geomechanical Abstr. 15, pp. 319 - 368.
Deere D.U. (1964). Technical description of rock cores. Rock Mechanics Engineering Geology 1. pp. 16 - 22.
Deere D.U. (1989). Rock quality designation (RQD) after twenty years. U.S. Army Corps of Engineers Contract
Report GL-89-1. Waterways Experiment Station, Vicksburg, MS, 67.
Palmstrøm A. (1975). Characterization of degree of jointing and rock mass quality. Internal Report. Ing.A.B.
Berdal A/S, Oslo, pp. 1 - 26.
Romana M. (1991). SMR classification. Proc. 7th Cong. on Rock Mechanics. ISRM. Aachen, Germany. 2. ed.
Wittke W. publ. Balkema, Rotterdam. pp. 955 - 960.
17 May 2011
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