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2015.04.10 1Tunnelling and Underground
Construction Technology
Tunnelling and Underground
Construction Technology
Course Lectures
Part 3.1 – Tunnel support design based on
Rock mass Classification methods
Dr Ákos TÓTH
2015.04.10 2
Rock Mass Property and Classification
2015.04.10 3
Rock Mass Property and Classification
2015.04.10 4
Principal Geometrical Characteristics of Rock Joints
Number of joint sets
Joint persistence
Joint plane orientation
Joint spacing, joint frequency, block size, and RQD
Joint surface roughness and matching
Joint aperture and filling
Geometrical Properties of Rock Joints
2015.04.10 5
Number of Joint Sets
Joints are generally in sets, i.e.,
parallel joints. The number of joint
sets can be up to 5. Typically one
joint set cuts the rock mass into
plates, two perpendicular sets cut
rock into column and three into
blocks, and more sets cut rocks
into mixed shapes of blocks and
wedges.
Geometrical Properties of Rock Joints
1 set
3 sets
2015.04.10 6
Geometrical Properties of Rock Joints
I Massive, occasional random fractures
II One joint set
III One joint set plus random fractures
IV Two joint sets
V Two joint sets plus random fractures
VI Three joint sets
VII Three joint sets plus random fractures
VIII Four or more joint sets
IX Crushed rock, earth-like
ISRM suggested descriptionMechanical
properties of the
rock mass is
influenced by
joint sets. More
joint sets provide
more
possibilities of
potential slide
planes .
2015.04.10 7
Joint Persistence
Persistence is the areal extent or length of a
discontinuity, and can be crudely quantified by
observing the trace lengths of discontinuities on
exposed surfaces. The persistence of joint sets
controls large scale sliding or 'down-stepping'
failure of slope, dam foundation and tunnel
excavation.
Geometrical Properties of Rock Joints
2015.04.10 8
ISRM Suggested Description Surface Trace Length (m)
Very low persistence < 1
Low persistence 1 – 3
Medium persistence 3 – 10
High persistence 10 – 20
Very high persistence > 20
2015.04.10 9
Joint Plane Orientation
Orientation of joint sets controls
the possibility of unstable
conditions or excessive
deformations. The mutual
orientation of joints determines
the shape of the rock blocks.
Orientation is defined by dip angle
(inclination) and dip direction
(facing) or strike (running).
Geometrical Properties of Rock Joints
2015.04.10 10
Geometrical Properties of Rock Joints
Dip angle
Dip direction
StrikeN
N
Horizontal planeOrientation:
Dip direction / Dip
220/55Measured clockwise on horizontal plane: 220
Measured on vertical plane: 55
Vertical plane
Line of maximum dip
2015.04.10 11
Geometrical Properties of Rock Joints
A geological compass to
measure dip and direction of
joint plane
An electronic geological
compass
2015.04.10 12
Joint Plane Orientation
Dip direction and strike direction are always
perpendicular. Dip direction/dip format is generally
used, e.g., 210/35, or 030/35. Sometimes, strike/dip
format is used, e.g., 120/35SW (=dip direction/dip
210/35), or 120/35NE (=dip direction/dip 030/35).
Normal (pole) to the plane is perpendicular to the
plane. Orientation of the normal is given by:
trend of normal = dip direction of the plane 180,
plunge of normal = 90 – dip.
Geometrical Properties of Rock Joints
2015.04.10 13
Joint Plane Orientation
Orientation of a joint plane can be represented
graphically using hemispherical projection method.
The projection method is to represent a 3D plane by
a 2D presentation. Use the projection, joint
orientation data can be assessed in 2D form. It can
be used to analyse large number of joint data and
examine the rock slope stability and slide of rock
block in underground excavation.
Geometrical Properties of Rock Joints
2015.04.10 14
Spherical projections plot and analyze joint orientation data
2015.04.10 15
Geometrical Properties of Rock Joints
2015.04.10 16
Plotting and analysis of joint orientation data performed by computer
2015.04.10 17
Joint Spacing, Frequency, Block Size, and RQD
Fracturing degree of a rock mass is controlled by
the number of joint in the rock mass. More joints
mean that less average spacing between joints.
Joint spacing controls the size of individual rock
blocks. It controls the mode of failure and flow. For
example, a close spacing gives low mass cohesion
and circular or even flow failure.
Geometrical Properties of Rock Joints
2015.04.10 18
Joint Spacing
Joint spacing is the perpendicular distance between
joints. For a joint set, is usually expressed as the
mean spacing of that joint set. Often the apparent
spacing is measured.
Measurements of joint spacing are different on
different measuring faces and directions. For
example, in a rock mass with mainly vertical joints,
measurements in vertical direction have far greater
spacing then that in horizontal direction.
Geometrical Properties of Rock Joints
2015.04.10 19
Geometrical Properties of Rock Joints
Apparent spacing in x, y and z directions
True spacingApparent spacingon the plane
2015.04.10 20
Geometrical Properties of Rock Joints
Description Joint Spacing (m)
Extremely close spacing < 0.02
Very close spacing 0.02 – 0.06
Close spacing 0.06 – 0.2
Moderate spacing 0.2 – 0.6
Wide spacing 0.6 – 2
Very wide spacing 2 – 6
Extremely wide spacing > 6
Classification of joint spacing
2015.04.10 21
Joint Frequency
Joint frequency (), is defined as number of joint per
metre length. It is therefore simply the inverse of
joint spacing (sj), i.e.,
= 1 / sj
Geometrical Properties of Rock Joints
2015.04.10 22
RQD
Rock Quality Designation (RQD) is defined as the
percentage of rock cores that have length equal or
greater than 10 cm over the total drill length.
RQD = Li / L x 100%, Li > 10 cm
RQD = (L1 + L2 + … + Ln) / L x 100%
Geometrical Properties of Rock Joints
<10 cm <10 cm <10 cm core loss
X X XX XL1 L2 L3 L4 L5 LnLi
L
2015.04.10 23
2015.04.10 24
RQD = (L1 + L2 + … + Ln) / L x 100%
= number of joints / length = n / L
Geometrical Properties of Rock Joints
X X XX XL1 L2 L3 L4 L5 LnLi
<10 cm <10 cm <10 cm fault
L
Outcrop Face
Tape1 2 i n
2015.04.10 25
RQD can be correlated to joint frequency ():
RQD = 100 (0.1 + 1) e–0.1
For = 6 and 16/m, it can be approximated by:
RQD = 110.4 – 3.68
RQD was initially proposed as an attempt to
describe rock quality, in reality, it only describes
fracturing degree, but not other properties such as
joint alteration, groundwater and rock strength.
Geometrical Properties of Rock Joints
2015.04.10 26
Geometrical Properties of Rock Joints
2015.04.10 27
Block Size and Volumetric Joint Count
Joint space also defines the size of rock blocks.
When a rock mass contains more joints numbers,
the joints have lower average spacing and smaller
block size.
RQD can be related to volumetric joint count Jv by:
RQD = 115 – 3.3 Jv, for Jv between 4.5 and 30.
Jv < 4.5, RQD = 100%, Jv > 30, RQD = 0%.
Geometrical Properties of Rock Joints
2015.04.10 28
Geometrical Properties of Rock Joints
Designation Volumetric Joint Count, joints/m3
Very large blocks < 1
Large blocks 1 – 3
Medium-sized blocks 3 – 10
Small blocks 10 – 30
Very small blocks > 30
Crushed rock > 60
ISRM suggested block size designations
2015.04.10 29
Joint Surface Roughness and Matching
A joint is an interface of two contacting surfaces.
The surfaces can be smooth or rough; they can be in
good contact and matched, or they can be poorly
contacted and mismatched.
Geometrical Properties of Rock Joints
The condition of contact
also governs the aperture
of the interface. The
interface can be filled with
intrusive or weathered
materials.
2015.04.10 30
Joint Roughness
Joint surface roughness is a measure of surface
unevenness and waviness relative to its mean plane.
The roughness is characterised by large scale
waviness (undulation) and small scale unevenness
(irregularity) of a joint surface. It is the principal
governing factor the direction of shear displacement
and shear strength, and in turn, the stability of
potentially sliding blocks.
Geometrical Properties of Rock Joints
2015.04.10 31
Geometrical Properties of Rock Joints
2015.04.10 32
Joint Roughness
Roughness should first be described in metre scale
(step, undulating, and planar) and then in centimetre
scale (rough, smooth, and slickensided), as
suggested by ISRM. It is not a quantitative measure.
Joint Roughness Coefficient (JRC) is a quantitative
measure of roughness, varying from 0 for the
smooth flat surface to 20 for the very rough surface.
Joint roughness is affected by geometrical scale.
Geometrical Properties of Rock Joints
2015.04.10 33
JRC number is
obtained by directly
comparing the
actual joint surface
profile with the
typical profile in the
chart.
JRC20 is the profile
for 20 cm and
JRC100 for 100 cm.
The value of JRC
decreases with
increasing size.
2015.04.10 34
Joint Roughness in 3D
In realty, profiles of joint surfaces are 3D features.
ISRM and JRC descriptions are 2D based. It is
therefore suggested to take several linear profiles of
a surface for the description and JRC indexing.
Joint surface is a rough profile that can be described
by statistic method and fractal. Fractal method is
applicable not only in 2D (linear profile), but also in
3D (surface plane profile). It is a useful tool to
quantify the surface profile.
Geometrical Properties of Rock Joints
2015.04.10 35
A joint surfaces is 3D. Each
2D measurement may give
defferent linear profiles.
2015.04.10 36
Geometrical Properties of Rock Joints
A joint surfaces in 3D, also
noting change of linear
profiles in directions.
Calculating fractal for a 3D
surface profile.
2015.04.10 37
Joint Matching
A joint is an interface of two surfaces. Properties of
a joint are also controlled by the relative positioning
of the two surfaces, in addition to the profiles. For
example, joints in fully contacted and interlocked
positions has little possibility of movement and is
also difficult to shear, as compared to the same
rough joints in point contact where movement can
easily occur. Often, joints are differentiated as
matched and mismatched. A Joint Matching
Coefficient (JMC) has been suggested.
Geometrical Properties of Rock Joints
2015.04.10 38
Geometrical Properties of Rock Joints
JMC is 1 for completely matched
joint and two surfaces fully in
contact.
JMC is 0 for completely
mismatched joint and two
surfaces in contact at a few points
only.
2015.04.10 39
Joint Aperture and Filling
In a natural joint, it is very seldom that the two
surfaces are in complete contact. There usually
exists an opening or a gap between the two
surfaces. The perpendicular distance separating
the adjacent rock walls is termed as aperture. Joint
opening is either filled with air and water (open joint)
or with infill materials (filled joint). Open or filled
joints with large apertures have low shear strength.
Aperture also associates with flow and permeability.
Geometrical Properties of Rock Joints
2015.04.10 40
Geometrical Properties of Rock Joints
2015.04.10 41
Geometrical Properties of Rock Joints
Aperture Description
< 0.1 mm Very tight
"Closed feature"0.1 ~ 0.25 mm Tight
0.25 ~ 0.5 mm Partly open
0.5 ~ 2.5 mm Open "Gapped
Feature"2.5 ~ 10 mm Widely open
1 ~ 10 cm Very widely open
"Open feature"10 ~ 100 cm Extremely widely open
> 1 m Cavernous
Classification of discontinuity aperture
2015.04.10 42
Joint Aperture and Filling
Aperture can be the real aperture and equivalent
hydraulic aperture. The later is particularly
important when permeability is concerned.
Filling is material in the rock discontinuities
separating the adjacent rock surfaces. In general,
properties of the filling material affect shear
strength, deformability and permeability of the
discontinuities.
Geometrical Properties of Rock Joints
2015.04.10 43
Rock Mass Properties
Rock mass is a matrix consisting of rock material
and rock discontinuities. Properties of rock mass
therefore are governed by the parameters of rock
joints and rock material, as well as boundary
conditions.
The behaviour of rock changes from continuous
elastic for intact rock materials to discontinues
running of highly fractured rock masses, depending
mainly on the existence of rock joints.
Rock Mass Property and Classification
2015.04.10 44
Point Load Index
Point load test is a simple
index test for rock material.
It gives the standard point
load index, Is(50).
Strength and Deformation
Granite 5 – 15
Gabbro 6 – 15
Andesite 10 – 15
Basalt 9 – 15
Sandstone 1 – 8
Mudstone 0.1 – 6
Limestone 3 – 7
Gneiss 5 – 15
Schist 5 – 10
Slate 1 – 9
Marble 4 – 12
Quartzite 5 – 15
2015.04.10 45
Correlation between Point Load Index and Strengths
c 22 Is(50)
Correction factor can vary between 10 and 30.
t 1.25 Is(50)
Is(50) should be used as an independent strength
index.
Strength and Deformation
2015.04.10 46
Prime parameters governing rock mass property
Rock Mass Property and Classification
Joint Parameters Material
Parameters
Boundary Conditions
Number of joint sets
Orientation
Spacing
Aperture
Surface roughness
Weathering and
alteration
Compressive
strength
Modulus of
elasticity
Groundwater
pressure and flow
In situ stress
2015.04.10 47
Rock Mass Clasification
Rock Load Factor
It classifies rock mass
into 9 classes. The
concept used in this
classification system is to
estimate the rock load to
be carried by the steel
arches installed to
support a tunnel.
Rock Mass Property and Classification
2015.04.10 48
Rock Class DefinitionRock Load Factor Hp
(feet) (B and Ht in feet)Remark
I. Hard and intact
Hard and intact rock contains no joints and fractures. After
excavation the rock may have popping and spalling at
excavated face.
0Light lining required only if
spalling or popping occurs.
II. Hard stratified
and schistose
Hard rock consists of thick strata and layers. Interface
between strata is cemented. Popping and spalling at
excavated face is common.
0 to 0.5 B
Light support for protection
against spalling. Load may
change between layers.
III. Massive,
moderately jointed
Massive rock contains widely spaced joints and fractures.
Block size is large. Joints are interlocked. Vertical walls do
not require support. Spalling may occur.
0 to 0.25 BLight support for protection
against spalling.
IV. Moderately
blocky and seamy
Rock contains moderately spaced joints. Rock is not
chemically weathered and altered. Joints are not well
interlocked and have small apertures. Vertical walls do not
require support. Spalling may occur.
0.25 B to 0.35 (B + Ht) No side pressure.
V. Very blocky
and seamy
Rock is not chemically weathered, and contains closely
spaced joints. Joints have large apertures and appear
separated. Vertical walls need support.
(0.35 to 1.1) (B + Ht) Little or no side pressure.
VI. Completely
crushed but
chemically intact
Rock is not chemically weathered, and highly fractured with
small fragments. The fragments are loose and not
interlocked. Excavation face in this material needs
considerable support.
1.1 (B + Ht)
Considerable side pressure.
Softening effects by water at
tunnel base. Use circular ribs or
support rib lower end.
VII. Squeezing
rock at moderate
depth
Rock slowly advances into the tunnel without perceptible
increase in volume. Moderate depth is considered as 150 ~
1000 m.
(1.1 to 2.1) (B + Ht)Heavy side pressure. Invert
struts required. Circular ribs
recommended.VIII. Squeezing
rock at great
depth
Rock slowly advances into the tunnel without perceptible
increase in volume. Great depth is considered as more than
1000 m.
(2.1 to 4.5) (B + Ht)
IX. Swelling rock
Rock volume expands (and advances into the tunnel) due to
swelling of clay minerals in the rock at the presence of
moisture.
up to 250 feet,
irrespective of B and Ht
Circular ribs required. In extreme
cases use yielding support.
2015.04.10 49
Comments on the Rock Load Factor Classification
(a) It provides reasonable support pressure
estimates for small tunnels with diameter up to 6
metres.
(b) It gives over-estimates for large tunnels with
diameter above 6 metres.
(c) The estimated support pressure has a wide
range for squeezing and swelling rock conditions
for a meaningful application.
Rock Mass Property and Classification
2015.04.10 50
Active Span and
Stand-Up Time
Stand-up time is the
length of time which
an excavated
opening can stand
without any mean of
support . Rock
classes are assigned
according to the
stand-up time.
Rock Mass Property and Classification
2015.04.10 51
Rock Quality
Designation (RQD)
RQD represents
fracturing degree
of the rock mass.
It partially
reflecting the rock
mass quality.
Rock Mass Property and Classification
RQD Rock Mass Quality
< 25 Very poor
25 – 50 Poor
50 – 75 Fair
75 – 90 Good
90 – 100 Excellent
2015.04.10 52
Rock Mass Rating RMR
RMR system incorporates 5 basic parameters.
(a) Strength of intact rock material: uniaxial compressive
strength or point load index;
(b) RQD;
(c) Spacing of joints: average spacing of all rock
discontinuities;
(d) Condition of joints: joint aperture, roughness, joint surface
weathering and alteration, infilling;
(e) Groundwater conditions: inflow or water pressure.
Rock Mass Property and Classification
2015.04.10 53
RMR Parameters
1.
Strength
of intact
rock
material
Point load
strength index
(MPa)
> 10 4 10 2 4 1 2
Uniaxial
compressive
strength (MPa)
> 250 100 250 50 100 25 50 5 25 1 5 < 1
Rating 15 12 7 4 2 1 0
2.RQD (%) 90 100 75 90 50 75 25 50 < 25
Rating 20 17 13 8 3
3.
Joint spacing
(m)> 2 0.6 2 0.2 0.6 0.06 0.2 < 0.06
Rating 20 15 10 8 5
2015.04.10 54
RMR Parameters
4.
Condition of
joints
not
continuous,
very rough
surfaces,
unweathered,
no separation
slightly
rough
surfaces,
slightly
weathered,
separation <1
mm
slightly rough
surfaces,
highly
weathered,
separation <1
mm
continuous,
slickensided
surfaces, or
gouge <5 mm
thick, or
separation 15
mm
continuous
joints, soft
gouge >5
mm thick,
or
separation
>5 mm
Rating 30 25 20 10 0
5.
Ground-
water
inflow per 10 m tunnel
length (l /min), ornone < 10 10 25 25 125 > 125
joint water pressure/major
in situ stress, or0 0 0.1 0.1 0.2 0.2 0.5 > 0.5
general conditions at
excavation surface
complete
ly drydamp wet dripping flowing
Rating 15 10 7 4 0
2015.04.10 55
RMR and rock mass quality
Rock Mass Property and Classification
RMR Ratings 81 100 61 80 41 60 21 40 < 20
Rock mass class A B C D E
Descriptionvery good
rockgood rock fair rock poor rock
very poor
rock
Average stand-
up time
10 year for
15 m span
6 months for
8 m span
1 week for
5 m span
10 hours for
2.5 m span
30 minutes for
0.5 m span
Rock mass
cohesion (KPa)> 400 300 400 200 300 100 200 < 100
Rock mass
friction angle > 45 35 45 25 35 15 25 < 15
2015.04.10 56
2015.04.10 57
Rock Tunnel Quality Q-System
Q = (RQD / Jn) (Jr / Ja) (Jw / SRF)
Block size Inter-block strength Active stress
RQD - Rock Quality Designation.
Jn - joint set number.
Jr - joint roughness number.
Ja - joint alteration number indicating the degree of
weathering, alteration and filling.
Jw = joint water reduction factor.
SRF = stress reduction factor.
Rock Mass Property and Classification
2015.04.10 58
Q-System Parameters
1. Rock Quality Designation RQD
A Very Poor 0 – 25
B Poor 25 – 50
C Fair 50 – 75
D Good 75 – 90
E Excellent 90 – 100
Note: (i) Where RQD is reported or measured as 10 (including 0), a nominal value of 10
is used to evaluate Q. (ii) RQD interval of 5, i.e., 100, 95, 90, etc., are sufficiently
accurate.
2015.04.10 59
Q-System Parameters
2. Joint Set Number Jn
A Massive, no or few joints 0.5 – 1
B One joint set 2
C One joint set plus random joints 3
D Two joint set 4
E Two joint set plus random joints 6
F Three joint set 9
G Three joint set plus random joints 12
H Four or more joint sets, heavily jointed 15
J Crushed rock, earthlike 20
Note: (i) For intersections, use (3.0 Jn). (ii) For portals, use (2.0 Jn).
2015.04.10 60
Q-System Parameters
3. Joint Roughness Number Jr
(a) Rock-wall contact, and (b) Rock wall contact before 10 cm shear
A Discontinuous joints 4
B Rough or irregular, undulating 3
C Smooth, undulating 2
D Slickensided, undulating 1.5
E Rough or irregular, planar 1.5
F Smooth, planar 1.0
G Slickensided, planar 0.5
Note: (i) Descriptions refer to small and intermediate scale features, in that order.
(c) No rock-wall contact when sheared
H Zone containing clay minerals thick enough to prevent rock-wall contact 1.0
J Sandy, gravelly or crushed zone thick enough to prevent rock-wall contact 1.0
Note: (ii) Add 1.0 if the mean spacing of the relevant joint set 3 m. (iii) Jr = 0.5 can be used for planar
slickensided joints having lineations, provided the lineations are oriented for minimum strength.
Note: Jr and Ja classification is applied to the joint set or discontinuity that is least
favourable for stability both from the point of view of orientation and shear
resistance.
2015.04.10 61
Q-System Parameters
4. Joint Alteration Number r approx. Ja
(a) Rock-wall contact (no mineral fillings, only coatings)
A Tight healed, hard, non-softening, impermeable filling, i.e., quartz or epidote – 0.75
B Unaltered joint walls, surface staining only 25 – 35 1.0
C Slightly altered joint walls. Non-softening mineral coating, sandy particles, clay-
free disintegrated rock, etc.
25 – 30 2.0
D Silty- or sandy-clay coatings, small clay fraction (non-softening) 20 – 25 3.0
E Softening or low friction mineral coatings, i.e., kaolinite or mica. Also chlorite,
talc, gypsum, graphite, etc., and small quantities of swelling clays
8 – 16 4.0
(b) Rock wall contact before 10 cm shear (thin mineral fillings)
F Sandy particles, clay-free disintegrated rock, etc. 25 – 30 4.0
G Strongly over-consolidated non-softening clay mineral fillings (continuous, but <
5 mm thickness)
16 – 24 6.0
H Medium or low over-consolidated softening clay mineral fillings (continuous, but
< 5 mm thickness)
12 – 16 8.0
J Swelling-clay fillings, i.e., montmorillonite (continuous, but < 5 mm thickness).
Value of Ja depends on percent of swelling clay size particles, and access to
water, etc.
6 – 12 8 – 12
(c) No rock-wall contact when sheared (thick mineral fillings)
K, L, M Zones or bands of disintegrated or crushed rock and clay (see G, H, J for
description of clay condition)
6 – 24 6, 8, 8 – 12
N Zones or bands of silty- or sandy-clay, small clay fraction (non-softening) - 5
O, P, R Thick, continuous zones or bands of clay (see G, H, J for clay condition
description)
6 – 24 10, 13, 13 – 20
2015.04.10 62
Q-System Prameters
5. Joint Water Reduction Factor Water pressure Jw
A Dry excavation or minor inflow, i.e., < 5 l/min
locally
< 1 (kg/cm2) 1.0
B Medium inflow or pressure, occasional outwash
of joint fillings
1 – 2.5 0.66
C Large inflow or high pressure in competent rock
with unfilled joints
2.5 – 10 0.5
D Large inflow or high pressure, considerable
outwash of joint fillings
2.5 – 10 0.33
E Exceptionally high inflow or water pressure at
blasting, decaying with time
> 10 0.2 – 0.1
F Exceptionally high inflow or water pressure
continuing without noticeable decay
> 10 (kg/cm2) 0.1 – 0.05
Note: (i) Factors C to F are crude estimates. Increase Jw if drainage measures are installed.
(ii) Special problems caused by ice formation are not considered.
2015.04.10 63
Q-System Parameters
6. Stress Reduction Factor SRF
(a) Weakness zones intersecting excavation, which may cause loosening of rock mass when
tunnel is excavated
A Multiple occurrences of weakness zones containing clay or chemically
disintegrated rock, very loose surrounding rock (any depth)
10
B Single weakness zone containing clay or chemically disintegrated rock
(depth of excavation 50 m)
5
C Single weakness zone containing clay or chemically disintegrated rock
(depth of excavation > 50 m)
2.5
D Multiple shear zones in competent rock (clay-free) (depth of excavation
50 m)
7.5
E Single shear zone in competent rock (clay-free) (depth of excavation
50 m)
5
F Single shear zone in competent rock (clay-free) (depth of excavation >
50 m)
2.5
G Loose, open joint, heavily jointed (any depth) 5
Note: (i) Reduce SRF value by 25-50% if the relevant shear zones only influence but not
intersect the excavation.
2015.04.10 64
Q-System Parameters
(b) Competent rock, rock stress problems c / 1 / c SRF
H Low stress, near surface, open joints > 200 < 0.01 2.5
J Medium stress, favourable stress condition 200 – 10 0.01 –
0.03
1
K High stress, very tight structure. Usually
favourable to stability, may be unfavourable to
wall stability
10 – 5 0.3 – 0.4 0.5 – 2
L Moderate slabbing after > 1 hour in massive rock 5 – 3 0.5 - 0.65 5 – 50
M Slabbing and rock burst after a few minutes in
massive rock
3 – 2 0.65 – 1 50 – 200
N Heavy rock burst (strain-burst) and immediate
dynamic deformation in massive rock
< 2 > 1 200 – 400
Note: (ii) For strongly anisotropic virgin stress field (if measured): when 5 1 / 3 10,
reduce c to 0.75 c; when 1 / 3 > 10, reduce c to 0.5 c; where c is unconfined
compressive strength, 1 and 3 are major and minor principal stresses, and is
maximum tangential stress (estimated from elastic theory).
(iii) Few cases records available where depth of crown below surface is less than
span width. Suggest SRF increase from 2.5 to 5 for such cases (see H).
2015.04.10 65
Q-value and rock mass quality
Rock Mass Property and Classification
Q-value Class Rock mass quality
400 ~ 1000 A Exceptionally Good
100 ~ 400 A Extremely Good
40 ~ 100 A Very Good
10 ~ 40 B Good
4 ~ 10 C Fair
1 ~ 4 D Poor
0.1 ~ 1 E Very Poor
0.01 ~ 0.1 F Extremely Poor
0.001 ~ 0.01 G Exceptionally Poor
2015.04.10 66
2015.04.10 67
Excavation Support Ratio (ESR)
Rock Mass Property and Classification
Excavation Category ESR
A Temporary mine openings. 3 – 5
B
Permanent mine openings, water tunnels for hydro-
electric projects, pilot tunnels, drifts and headings for
large excavations.
1.6
C
Storage rooms, water treatment plants, minor road and
railway tunnels, surge chambers and access tunnels in
hydro-electric project.
1.3
D
Underground power station caverns, major road and
railway tunnels, civil defense chamber, tunnel portals and
intersections.
1.0
EUnderground nuclear power stations, railway stations,
sports and public facilities, underground factories.0.8
2015.04.10 68
Geological Strength Index GSI
GSI was aimed to estimate the reduction in rock
mass strength for different geological conditions.
The system gives a GSI value estimated from rock
mass structure and rock discontinuity surface
condition. The direct application of GSI value is to
estimate the parameters in the Hoek-Brown strength
criterion for rock masses.
Rock Mass Property and Classification
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2015.04.10 70
GSI and rock mass quality
Rock Mass Property and Classification
GSI Value 76 95 56 75 41 55 21 40 < 20
Rock Mass
Quality
Very
goodGood Fair Poor
Very
poor
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Rock Support using Q-System
• Rock Mass Classification Q-System
• General Support Design Methodology
• Excavation Support Ratio and Equivalent Span
• Roof Support Requirements from Q-Chart
• Design of Wall Support
• Design of Temporary Support
• Maximum Unsupported Span
• Bolt Length and Spacing
• Limitation of Q-System
• Examples
2015.04.10 72Tunnelling and Underground
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Rock Mass Classification Q-System
Rock Tunnel Quality Q-value is a measure of rock mass quality, given as:
Q = (RQD / Jn) (Jr / Ja) (Jw / SRF)
RQD - Rock Quality Designation.
Jn - joint set number.
Jr - joint roughness number.
Ja - joint alteration number (weathering, alteration, filling).
Jw = joint water reduction factor.
SRF = stress reduction factor.
Rock Support using Q-System
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Q-value Class Rock mass quality
400 ~ 1000 A Exceptionally Good
100 ~ 400 A Extremely Good
40 ~ 100 A Very Good
10 ~ 40 B Good
4 ~ 10 C Fair
1 ~ 4 D Poor
0.1 ~ 1 E Very Poor
0.01 ~ 0.1 F Extremely Poor
0.001 ~ 0.01 G Exceptionally Poor
Rock Support using Q-System
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General Support Design Methodology
Q is also a measure of rock stability in relation to
opening size.
It is empirical design based on thousands of cases, to
provide the design of permanent support using Q value.
Support design depends on effective span (diameter or
height) and safety requirement.
Rock Support using Q-System
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Excavation Support Ratio and Equivalent Span
Safety requirement is measured by a term called
Excavation Support Ratio (ESR), which in turn, gives the
Equivalent Dimension (De).
De =Actual excavation span or height
Excavation support ratio, ESR
Rock Support using Q-System
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Excavation Support Ratio (ESR)
Excavation Category ESR
A Temporary mine openings. 3 – 5
B
Permanent mine openings, water tunnels for hydro-electric
projects, pilot tunnels, drifts and headings for large
excavations.
1.6
C
Storage rooms, water treatment plants, minor road and
railway tunnels, surge chambers and access tunnels in
hydro-electric project.
1.3
D
Underground power station caverns, major road and railway
tunnels, civil defence chamber, tunnel portals and
intersections.
1.0
EUnderground nuclear power stations, railway stations, sports
and public facilities, underground factories.0.8
Rock Support using Q-System
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Rock Support using Q-System
Roof Support Requirements from Q-Chart
The design chart using Q-value is the support design requirement for tunnel roof.
1. Horizontal axis is the Q-value of the surrounding rock masses.
2. Left vertical axis is the equivalent dimension of the designed tunnel.
3. Intersection point defines the support requirement zone, which gives type of support and thickness of sprayed concrete.
4. Vertical up from the intersection gives bolt spacing.
5. Horizontal to the right from the intersection gives bolt length.
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Design of Rock Support
1
2
3
5
Q = 1.33, tunnel span = 16m
ESR = 0.8, De = 20m
4
3
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Rock Support using Q-System
Notes on Q-Chart
Bolt length is determined based on the actual span or height (i.e., ESR=1). It is in fact estimated by the following equation, L = 1.4 + 0.184 Span.
Bolt spacing is determined by Q-value, but be aware the thickness for plain and SFR shotcrete are different.
In support zone (2) to (7), ERS effectively is to change the support measure by changing only the thickness of shotcrete.
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Rock Support using Q-System
Design of Wall Support
Wall height should be used in equivalent dimension.
When Q values are used in design wall support, following adjustment should be used:
For Q > 10, Qwall = 5 Q
For 0.1 < Q < 10, Qwall = 2.5 Q
For Q < 0.1, Qwall = Q
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Rock Support using Q-System
Design of Temporary Support
Temporary support measures are primarily bolts and shotcrete (sometimes, steel sets).
For temporary support, the following adjustment can be used:
Increase ESR to 1.5 ESR
or
Increase Q to 5 Q (applicable to roof and wall)
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Rock Support using Q-System
Maximum Unsupported Span
For reasonably good quality rock mass, it is possible to have the tunnel unsupported for a long period.
Maximum unsupported span = 2 ESR Q0.4
Example:
Q = 10, ESR = 1 maximum unsupported span = 5 m
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Rock Support using Q-System
Bolt Length and Spacing
Spot/Local bolting is used to secure individual blocks of rock.
Spacing is depending on the size of the block which can be estimated from observation of the joints.
The bolts should be long enough to obtain adequate anchorage in stable rock beyond the block (1~2 m into the solid rock).
For systematic bolting, the bolt spacing (function of joint spacing) and length is to be estimated from Q-chart.
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Rock Support using Q-System
Bolt Length and Spacing
Alternative to the chart, bolt length can be estimated using the equation below:
L = 1.4 + 0.184 Span (m)
Typical bolts are steel bars between 20 and 40 mm diameter, with bolt capacity up to 250 kN.
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Support description
•The length L of rock bolts can be
also estimated from the excavation
width B and the Excavation Support
Ratio ESR
•The maximum unsupported span
can be estimated from Q and ESR
•The permanent roof support
pressure Proof is estimated from Q, Jn
and Jr
0.152
BL
ESR
0.4Max span (unsupported) =2ESR Q
Grimstad and Barton (1993)
1/ 32
3
n
roof
r
J QP
J
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65 m2
101 holes
115 m2
151 holes
PilotSlash
Bench, 3.5-m high
Chamber section: 275 m2
Tunnel Sections in a Granite
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Rock Support using Q-System
Support Applied in Tunnels in a Granite
Q Support Span 10 m Span 15 m Span 30 m
>40Bolt Spot Spot Spot
SC 40 mm 40 mm 40 mm
10-40Bolt L3, S2.4 m L4, S2.4 m L5, S2.4 m
SC 40 mm 40 mm 50 mm
4-10Bolt L3, S2.2 m L4, S2.2m L5, S2.2 m
SC 40 mm 40 mm 50 mm
1-4Bolt L3, S1.9 m L4, S1.9 m L5, S1.9 m
SC 50 mm 50 mm 75 mm
< 1Bolt L3, S1.5 m L4, S1.5m L5, S1.5 m
SC 75 mm 75 mm 100 mm
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Rock Support using Q-System
Limitation of Q-System
The Q system can be used correctly for:
• Normal hard rock condition
• Very Poor to Good rock mass (0.1<Q<40)
• Jointed blocky rock mass where instability is caused by block falls
• Practical excavation span between 3 and 30 m
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Rock Support using Q-System
Limitation of Q-System
For support zones 2 and 3, with Q-value between 4 and 40, the chart suggests no shotcrete. However, a thin layer of shotcrete at roof is highly recommended.
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Example (a): hydropower access tunnel of 20 m span, wall
height 10 m
Granite rock mass containing 3 joint sets, average RQD is 88%,
average joint spacing is 0.24 m, joint surfaces are generally
stepped and rough, tightly closed and un-weathered with
occasional stains observed, the excavation surface is wet but
not dripping, average rock material uniaxial compressive
strength is 160 MPa, the tunnel is excavated to 150 m below
the ground where no abnormal high in situ stress is expected.
Rock Support using Q-System
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RQD 88% RQD 88
Joint set number 3 sets Jn 9
Joint roughness
numberrough stepped (undulating) Jr 3
Joint alteration number unaltered, some stains Ja 1
Joint water factorwet only (dry excavation or minor
inflow)Jw 1
Stress reduction factor c/1 = 160/(1500.027) = 39.5 SRF 1
Q (88/9) (3/1) (1/1) 29
Rock Support using Q-System
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Design of Rock Support
1
2
3
5
Q = 29, ESR = 1.3, Span = 20m, De = 15.4m
4
3
Qwall=5Q
Ht = 10m
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Example (a): hydropower access tunnel of 20 m span, in granite, with Q=29
Roof support requirement from the Q-chart:
Systematic bolting
Bolt spacing at 2.5 m
Bolt length of 5 m
Thin shotcrete layer (approx. 2 cm) at roof
Side wall support requirement:
Generally no support needed
Rock Support using Q-System
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Example (b): highway tunnel of 20 m span, 10 m high
A sandstone rock mass, fractured by 2 joint sets plus random
fractures, average RQD is 70%, average joint spacing is 0.11
m, joint surfaces are slightly rough, highly weathered with
stains and weathered surface but no clay found on surface,
joints are generally in contact with apertures generally less
than 1 mm, average rock material uniaxial compressive
strength is 85 MPa, the tunnel is to be excavated at 80 m
below ground level and the groundwater table is 10 m below
the ground surface.
Rock Support using Q-System
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RQD 70% RQD 70
Joint set number 2 sets plus random Jn 6
Joint roughness
numberslightly rough (rough planar) Jr 1.5
Joint alteration number
highly weathered only stain,
(altered non-softening mineral
coating)
Ja 2
Joint water factor70 m water head = 7 kg/cm2 = 7
barsJw 0.5
Stress reduction factor c/1 = 85/(800.027) = 39.3 SRF 1
Q (70/6) (1.5/2) (0.5/1) 4.4
Rock Support using Q-System
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Design of Rock Support
1
2
3
5
Q=4.4, ESR=1.0, Span=20m, De=20m 4
3
Qwall=2.5Q
Htl=10m
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Example (b): highway tunnel of 20 m span, 10 m high, in sandstone, with Q=4.4
Roof support requirement from the Q-chart:
Bolt spacing at 2.1 m
Bolt length of 5 m
SFR shotcrete of 7 cm
Side wall support requirement:
Bolting at 2.4 m spacing
Bolt length of 3 m
Thin shotcrete to cover or no shotcrete
Rock Support using Q-System
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Example (c): railway tunnel of 10 m diameter
A highly fractured siltstone rock mass, has 2 joint sets and
many random fractures, average RQD is 41%, joints appears
continuous observed in tunnel, joint surfaces are slicken-sided
and undulating, and are highly weathered, joint are separated
by about 3-5 mm, filled with clay, average rock material uniaxial
compressive strength is 65 MPa, inflow per 10 m tunnel length
is observed at approximately 50 litre/minute, with considerable
outwash of joint fillings. The tunnel is at 220 m below ground.
Rock Support using Q-System
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RQD 41% RQD 41
Joint set number 2 sets plus random Jn 6
Joint roughness
numberSlicken-sided and undulating Jr 1.5
Joint alteration numberhighly weathered filled with 3-5 mm
clayJa 4
Joint water factorlarge inflow with considerable
outwashJw 0.33
Stress reduction factor c/1 = 65/(2200.027) = 11 SRF 1
Q (41/6) (1.5/4) (0.33/1) 0.85
Rock Support using Q-System
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Design of Rock Support
1
2
3
5
Q = 0.85, ESR = 1.0, Span = 10m, De = 10m
4
3
Qwall=2.5Q
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Example (c): railway tunnel of 10 m diameter, in highly fractured siltstone, with Q=0.84
Roof support requirement from the Q-chart:
Bolt spacing at 1.6 m
Bolt length of 3 m
SFR shotcrete of 10 cm
Side wall support requirement:
Bolting at 1.9 m spacing
SFR shotcrete of 6 cm
Rock Support using Q-System
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Rock Support using RMR
• Rock Mass Rating RMR
• General Support Design Methodology
• RMR Adjustment for Tunnelling
• Support Guide using RMR
• Maximum Unsupported Span
• Bolt Length and Spacing
• Guide on Shotcrete
• Limitation of RMR Design System
• Examples
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Rock Mass Rating RMR
RMR system incorporates 5 basic parameters:
1. Strength of intact rock material: uniaxial compressive strength or point
load index;
2. RQD;
3. Spacing of joints: average spacing of all rock discontinuities;
4. Condition of joints: joint aperture, roughness, joint surface weathering
and alteration, infilling;
5. Groundwater conditions: inflow or water pressure.
Rock Support using RMR
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RMR and Rock Mass Quality
RMR Ratings 81 100 61 80 41 60 21 40 < 20
Rock mass
classA B C D E
Descriptionvery good
rockgood rock fair rock poor rock
very poor
rock
Average stand-
up time
10 year
for 15 m
span
6 months
for 8 m
span
1 week
for 5 m
span
10 hours
for 2.5 m
span
30 minutes
for 0.5 m
span
Rock mass
cohesion (KPa)> 400 300 400 200 300 100 200 < 100
Rock mass
friction angle > 45 35 45 25 35 15 25 < 15
Rock Support using RMR
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Rock Support using RMR
RMR Adjustment for Tunnelling
To use RMR for tunnel support design, RMR rating needs to be adjusted for tunnel alignment with respect to joint orientations.
Adjusted RMR = Original RMR + Adjustment
Adjustment is between 0 and -12.
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Rock Support using RMR
Rating adjustment for joint orientations
Conditionvery
favourable
favourabl
efair
unfavoura
ble
very
unfavourable
Rating
adjustment0 2 5 10 12
Effects of joint orientation in tunnelling
Strike to tunnel axis, drive with dipStrike to tunnel axis, drive against
dip
Dip 45 90
very favourable
Dip 20 45
favourable
Dip 45 90
fair
Dip 20 45
unfavourable
Strike // to tunnel axis Sub-horizontal joint (Dip 0 20)
Dip 45 90
very unfavourable
Dip 20 45
fair
irrespective of strike
fair
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General Support Design Methodology
RMR is a measure of rock mass quality, as well as a measure
of rock stability in relation to opening size.
It was initially developed
to estimate the stand-up
time for mines of various
opening size in rocks
of various quality
Rock Support using RMR
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Support Guide using RMR
Support using RMR is empirical based on the RMR value.
The design guide is primarily for tunnels operation.
Tunnel sizes are generally between 2 and 15 metres.
Rock Support using RMR
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Rock Support using RMR
Adjusted
ratings
Original RMR ratings
>80 70-80 60-70 50-60 40-50 30-40 20-30 10-20 0-10
>50 a a a a
40-50 b b b b
30-40 c, d c, d c, d, e d, e
20-30 g f, g f, g, j f, h, j
10-20 i i h, i, j h, j
0-10 k k l l
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a) Generally no support, but joint intersections may require local bolting.
b) Patterned, grouted bolts at 1.0 m spacing.
c) Patterned, grouted bolts at 0.75 m spacing.
d) Patterned, grouted bolts at 1.0 m spacing, and shotcrete 100 mm thick.
e) Patterned, grouted bolts at 1.0 m spacing, and massive concrete 300 mm thick; only used if stress changes are not excessive.
f) Patterned, grouted bolts at 0.75 m spacing, and shotcrete 100 mm thick.
g) Patterned, grouted bolts at 0.75 m spacing, and mesh-reinforced shotcrete 100 mm thick.
Rock Support using RMR
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h) Patterned, grouted bolts at 1.0 m spacing, and massive concrete 450 mm thick; if stress changes are not excessive.
i) Patterned, grouted bolts at 0.75 m spacing, and mesh-reinforced shotcrete 100 mm thick, plus yielding steel arches as repair technique if stress changes are excessive.
j) Stabilize with wire-mesh cover support and massive concrete 450 mm thick; if stress changes are not excessive.
k) Stabilize with wire-mesh cover support followed by 100-150 mm shotcrete (including face if necessary), plus yielding steel arches where stress changes excessive.
l) Avoid failure development in this ground if possible; otherwise, use support systems j or k.
Rock Support using RMR
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Supplementary notes
1. The original RMR rating, as well as the adjusted ratings, must be considered in assessing ground-support requirements.
2. Rock bolts are generally ineffective in highly jointed rock masses and should not be used as the sole support when the joint spacing rating is less than 6.
3. Support recommendations in the table are applicable to mine openings with stress levels less than 30 MPa.
4. Large chambers should only be excavated in rock with adjusted total RMR of 50 or better.
Rock Support using RMR
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Maximum Unsupported Span
Maximum unsupported span and stand-up time can be estimated from the chart.
Rock Support using RMR
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Bolt Length and Spacing
The minimum bolt length is recommended to be the greatest of the following:
1. two times the bolt spacing;
2. three times the average discontinuity spacing for critical rock blocks;
3. 0.5B for spans of B < 6m, or 0.25B for spans of B = 18 to 30m.
For excavations higher than 18m, the lengths of sidewall bolts should be at least 1/5 of the wall height.
Rock Support using RMR
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Bolt Length and Spacing
The maximum bolt spacing is recommended to be ½ bolt length or 1.5 times the average spacing of rock joints.
However, if wire mesh is to be anchored by the bolts, then a bolt spacing greater than 2 m makes attachment of the mesh practically impossible.
Rock bolt design for major zones of instability created by seams or persistent smooth joints should be the subject of stability analysis.
Rock Support using RMR
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Rock Support using RMR
Guide on Shotcrete
1. Shotcrete (particularly fibre reinforced) thickness should not exceed 20 cm;
2. Thick layers of shotcrete may be applied occasionally to small areas of particularly poor rock.
In general, systematic bolting with fibre reinforced shotcrete should be used for permanent support of roofs of tunnels that will be occupied by people or will contain important processes or machinery.
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Limitation of RMR System
RMR is primarily developed for mining, i.e., for tunnels of limited size. Design guide does not cover size effects.
Design does not consider the usage and safety requirements.
Rock Support using RMR
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Example (a): hydropower access tunnel of 18 m span
Granite rock mass containing 3 joint sets (1 sub-horizontal, 1
sub-vertical and sub-vertical // to tunnel axis), average RQD
is 88%, average joint spacing is 0.24 m, joint surfaces are
generally stepped and rough, tightly closed and unweathered
with occasional stains observed, the excavation surface is wet
but not dripping, average rock material uniaxial compressive
strength is 160 MPa, the tunnel is excavated to 150 m below
the ground.
Rock Support using RMR
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Rock material strength 160 MPa Rating 12
RQD (%) 88% Rating 17
Joint spacing (m) 0.24 m Rating 10
Condition of jointsvery rough, unweathered, no
separationRating 30
Groundwater wet Rating 7
RMR 76
Rock Support using RMR
Joint orientation condition: fair, v fav, v unfav v unfav
Adjustment = -12; Adjusted RMR = 64
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Rock Support using RMR
a. Generally no support, but joint intersections may require local bolting.
Adjusted
ratings
Original RMR ratings
>80 70-80 60-70 50-60 40-50 30-40 20-30 10-20 0-10
>50 a a a a
40-50 b b b b
30-40 c, d c, d c, d, e d, e
20-30 g f, g f, g, j f, h, j
10-20 i i h, i, j h, j
0-10 k k l l
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Example (b): highway tunnel of 20 m span
A sandstone rock mass, fractured by 2 joint sets (1 // to tunnel axis
dipping at 30 and 1 to tunnel axis dipping at 70), plus random
fractures, average RQD is 70%, average joint spacing is 0.11 m, joint
surfaces are slightly rough, highly weathered with stains and
weathered surface but no clay found on surface, joints are generally
in contact with apertures generally less than 1 mm, average rock
material uniaxial compressive strength is 85 MPa, the tunnel is to be
excavated at 80 m below ground level and the groundwater table is
10 m below the ground surface.
Rock Support using RMR
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Rock material
strength85 MPa Rating 7
RQD (%) 70% Rating 13
Joint spacing (m) 0.11 m Rating 8
Condition of jointsslightly rough, highly weathered,
separation < 1mmRating 20
Groundwater water pressure/stress = 0.32 Rating 4
RMR 52
Rock Support using RMR
Joint orientation condition: fair, fair to very favourable fair
Adjustment = -5; Adjusted RMR = 47
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Rock Support using RMR
b. Patterned, grouted bolts at 1.0 m spacing
Adjusted
ratings
Original RMR ratings
>80 70-80 60-70 50-60 40-50 30-40 20-30 10-20 0-10
>50 a a a a
40-50 b b b b
30-40 c, d c, d c, d, e d, e
20-30 g f, g f, g, j f, h, j
10-20 i i h, i, j h, j
0-10 k k l l
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Example (c): railway tunnel of 10 m diameter
A highly fractured siltstone rock mass, has 2 joint sets (1 sub-
horizontal and 1 sub-vertical // to tunnel axis), and many random
fractures, average RQD is 41%, joints appears continuous
observed in tunnel, joint surfaces are slicken-sided and undulating,
and are highly weathered, joint are separated by about 3-5 mm,
filled with clay, average rock material uniaxial compressive strength
is 65 MPa, inflow per 10 m tunnel length is observed at
approximately 50 litre/minute, with considerable outwash of joint
fillings. The tunnel is at 220 m below ground.
Rock Support using RMR
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Rock material strength 65 MPa Rating 7
RQD (%) 41% Rating 8
Joint spacing (m) 0.05 m Rating 5
Condition of jointscontinuous, slicken-sided,
separation 1-5mmRating 10
Groundwater inflow = 50 l/min Rating 4
RMR 34
Rock Support using RMR
Joint orientation condition: fair, very unfavourable very unfavourable
Adjustment = -12; Adjusted RMR = 22
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Rock Support using RMR
g, j. Closely spaced (0.75 m) bolts, wire-mesh, and shotcrete 100 mm thick, followed by cast-in concrete 450 mm thick.
Adjusted
ratings
Original RMR ratings
>80 70-80 60-70 50-60 40-50 30-40 20-30 10-20 0-10
>50 a a a a
40-50 b b b b
30-40 c, d c, d c, d, e d, e
20-30 g f, g f, g, j f, h, j
10-20 i i h, i, j h, j
0-10 k k l l
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Comparison of Q and RMR Support Design Systems
Rock Support using RMR
System Rock Mass 1
(18 m span)
Rock Mass 2
(20 m span)
Rock Mass 3
(10 m span)
RMR Generally no
support, with
possible spot bolts
Systematic bolts at
1.0 m spacing.
Systematic bolts at 0.75 m
spacing, wire-mesh, 10 cm
shotcrete, 45 cm cast-in
concrete
Q Systematic bolts at
2.5 m spacing, no
or thin shotcrete
Systematic bolts at
2.1 m spacing, 7
cm SFR shotcrete
Systematic bolts at 1.6 m
spacing, SFR 10 cm
shotcrete
Major differences
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Comparison and Comments
RMR does not consider tunnel size, it is generally suitable for tunnel between 3-10 m.
RMR does not differentiate roof and wall support.
For rock mass of fair and above quality, RMR and Q give similar support, though Q uses more shotcrete, while RMR uses more bolts (practical in mines).
For very poor rock mass, the difference in support is very large:
• It was recognised Q-system is not initially designed for very poor rock.
• So RMR system is recommended for support design in rock mass of poor and below quality.
Rock Support using RMR
Recommended