The document discusses rock mass classification using the Q-system. It begins by defining rock mass and describing different types based on discontinuities, from massive to heavily jointed rock. It then discusses the Q-system which evaluates rock mass quality based on factors like degree of jointing, joint roughness, alteration, water conditions and stresses. These factors are used to calculate a Q-value, with higher values indicating better rock mass stability. The Q-system provides guidelines for rock support design based on the Q-value. Overall, the document provides an overview of rock mass characteristics and classifications using the Q-system.

1. GROUP 1
• ZEESHAN AHMAD 301
• MUJEEB HUSSAIN 302
• MUNEEB HUSSAIN 303
• SHAHEER RAZA 304
• MUHAMMAD ADNAN 305
• MUHAMMAD SHAHJAHAN 306
• MUHAMMAD ARIF 307
• SYED SADAR ABBAS 308
• MUHAMMAD AMJAD 309
• IJLAL RAZA 310

2. ROCK MASS
ROCK MASS IS A NON-
HOMOGENEOUS, ANISOTROPIC
AND DISCONTINUOUS MEDIUM ;
OFTEN IT IS A PRE-STRESSED
MASS

3. ROCK MASS DESCRIPTION
MASSIVE ROCK
ROCK MASS WITH FEW DISCONTINUITIES IS TERMED AS MASSIVE ROCK
BLOCKEY/JOINTED ROCK
ROCK MASS WITH MODERATE NUMBER OF DISCONTINUITIES IS TERMED AS
JOINTED ROCK.
HEAVILY JOINTED ROCK
ROCK MASS WITH LARGE NUMBER OF DISCONTINUITIES IS TERMED AS HEAVILY
JOINTED ROCK.

4. MASSIVE ROCK JOINTED ROCK
Rock Quality

5. Heavily Jointed Rock
Massive Rock

6. INTRODUCTION TO ROCK MASS
CLASSIFICATION
ROCK MASS CLASSIFICATION SCHEMES HAVE BEEN DEVELOPED TO
ASSIST (PRIMARILY) IN THE COLLECTION OF ROCK INTO COMMON
OR SIMILAR GROUPS.
THE FIRST TRULY ORGANIZED SYSTEM WAS PROPOSED BY DR.
KARL TERZAGHI (1946) AND HAS BEEN FOLLOWED BY A NUMBER
OF SCHEMES PROPOSED BY OTHERS.

7. WHY WE STUDY ROCK MASS?
CONSTRUCTION OF DAMS, TUNNELS ROADS IS CARRIED OUT ON
ROCK MASS, THEREFORE IT IS VERY NECESSARY TO STUDY THE
BEHAVIOR OF ROCK MASS.
STUDY OF ROCK MASS INCLUDES ALL THOSE PARAMETERS WHICH
EFFECTS THE STABILITY OF ROCK MASS.
Q-SYSTEM BRIEFLY DESCRIBE THE BEHAVIOR OF ROCK MASS.

8. AREAS OF APPLICATION
• Q VALUE IS USED FOR CLASSIFICATION OF THE
ROCK MASS AROUND AN UNDER GROUND
OPENING, AS WELL AS Q VALUE IS USED FOR
FIELD MAPPING.
• THE DIFFERENT Q VALUES ARE RELATED TO
DIFFERENT TYPES OF PERMANENT SUPPORT.

9. • THE Q SYSTEM CAN BE USED AS GUIDELINE IN THE ROCK
SUPPORT DESIGN.
• IN PRE INVESTIGATION THE Q VALUE CAN BE OBTAINED
FROM CORE BUT IN SUCH CASE SOME OF THE PARAMETERS
ARE DIFFICULT TO ESTIMATE.

10. ROCK MASS STABILITY
• ROCK MASS STABILITY IS INFLUENCED BY
• 1) DEGREE OF JOINTING
• 2) JOINT FRICTION
• 3) STRESS

11. THE Q-SYSTEM
• HIGH Q-VALUES INDICATE GOOD STABILITY.
• LOW Q-VALUES INDICATE POOR STABILITY.
• Q-VALUE IS CALCULATED BY USING FOLLOWING EQUATION;
• RQD = DEGREE OF JOINTING
• JN = NUMBER OF JOINT SETS
• JR=JOINT ROUGHNESS NUMBER
• JA=JOINT ALTERATION NUMBER
• JW=JOINT WATER REDUCTION FACTOR
• SRF=STRESS REDUCTION FACTOR

12. QUOTIENT FACTORS
I. RELATIVE BLOCK SIZE (RQD/JN)
II. INTER-BLOCK SHEAR STRENGTH (JR/JA)
III. ACTIVE STRESSES (JW/SRF)

13. RELATIVE BLOCK SIZE (RQD/JN)
THE FIRST, RQD/JN, IS RELATED TO THE
ROCK MASS GEOMETRY: Q INCREASES
WITH INCREASING RQD AND
DECREASING NUMBER OF
DISCONTINUITY SETS. RQD INCREASES
WITH DECREASING NUMBER OF
DISCONTINUITY SETS, SO THE
NUMERATOR AND DENOMINATOR OF
THE QUOTIENT MUTUALLY REINFORCE
ONE ANOTHER.

14. BASICALLY, THE HIGHER THE VALUE OF THIS QUOTIENT,
THE BETTER THE ’GEOMETRICAL QUALITY’ OF THE ROCK
MASS.
MOREOVER, THERE IS ALSO THE PROBLEM (WHICH IS, IN
FACT, COMMON TO BOTH THE RMR SYSTEM AND THE Q-
SYSTEM) THAT RQD GENERALLY EXHIBITS ANISOTROPY, YET
ANISOTROPY IS NOT CONSIDERED.

15. INTER-BLOCK SHEAR STRENGTH
(JR/JA)
THE SECOND QUOTIENT, JR/JA, RELATES TO THE ’INTER-
BLOCK SHEAR STRENGTH’ WITH HIGH VALUES OF THIS
QUOTIENT REPRESENTING BETTER ‘MECHANICAL QUALITY’
OF THE ROCK MASS: THE QUOTIENT INCREASES WITH
INCREASING DISCONTINUITY ROUGHNESS AND DECREASING
DISCONTINUITY SURFACE ALTERATION.
THE DIFFERENT DISCONTINUITY SETS IN THE ROCK MASS
MAY HAVE DIFFERENT ROUGHNESS AND DEGREES OF
ALTERATION, SO THE Q-SYSTEM USES THE WORST CASE.

16. ACTIVE STRESSES (JW/SRF)
THE THIRD QUOTIENT, JW/SRF, IS AN ’ENVIRONMENTAL FACTOR’
INCORPORATING WATER PRESSURES AND FLOWS, THE PRESENCE OF
SHEAR ZONES, SQUEEZING AND SWELLING ROCKS AND THE INSITU
STRESS STATE.
 THE QUOTIENT INCREASES WITH DECREASING WATER PRESSURE OR
FLOW RATE, AND ALSO WITH FAVORABLE ROCK MASS STRENGTH TO
INSITU STRESS RATIOS.

17. GENERAL CALCULATION OF Q-VALUE
• Q-VALUE CAN BE CALCULATED BY
UNDERGROUND MAPPING.
• Q-VALUE CAN BE OBTAINED AT THE
SURFACE.
• ALTERNATIVELY Q-VALUE CAN BE
OBTAINED BY CORE LOGGING.
• Q-VALUE CAN RANGE BETWEEN 0.001 FOR
AN EXCEPTIONALLY POOR TO 1000 FOR
AN EXCEPTIONALLY GOOD ROCK MASS.

19. RELATION OF RQD AND Q VALUE.
• AS WE HAVE THE FORMULA OF Q SYSTEM WHICH IS GIVEN
BELOW.
SO FROM FORMULA WE CAN SEE THAT THE RQD AND Q
SYSTEM HAVE DIRECT RELATIONSHIP SO IF THE RQD IS MORE
THEN THE Q VALUE IS ALSO MORE.

20. ROCK QUALITY DESIGNATION (RQD)
RQD WAS INTRODUCED BY DEERE IN 1963 AND WAS MEANT TO BE
USED AS A SIMPLE CLASSIFICATION SYSTEM FOR THE STABILITY
OF ROCK MASSES.
RQD IS A ROUGH MEASUREMENT OF THE DEGREE OF JOINTING OR
FRACTURES IN A ROCK MASS, MEASURED AS A PERCENTAGE OF
THE DRILL CORE (OF ROCK MASS) IN LENGTHS OF 10 CM OR MORE.
HIGH-QUALITY ROCK HAS AN RQD OF MORE THAN 75%, LOW
QUALITY OF LESS THAN 50%.

23. RQD-VALUESANDVOLUMETRICJOINTING
• IN AN UNDERGROUND IT IS USUALLY POSSIBLE TO GET
THREE DIMENSIONAL VIEW OF ROCK MASS.
• THIS MEANS THAT THE RQD VALUE IS ESTIMATED FROM THE
NUMBERS OF JOINTS PER M3(METER CUBE).
• THE FOLLOWING FORMULA MAY BE USED:
RQD=110-2.5JV
WHERE JV IS THE NUMBER OF JOINTS PER
METER CUBE

24. • BASED ON THE FORMULA ABOVE, THE NUMBER
OF JOINT PER M3 FOR EACH RQD CLASS IS SHOWN
IN TABLE 1

25. RQD IN BLASTED UNDERGROUND
EXCAVATIONS
THESE ARTIFICIAL JOINTS SHOULD NOT BE TAKEN INTO ACCOUNT WHEN
EVALUATING THE RQD. HOWEVER, THEY MAY BE IMPORTANT FOR THE
STABILITY OF SINGLE BLOCKS. SINGLE BLOCKS MUST BE SUPPORTED
INDEPENDENTLY.

26. RQD IN SOFT ROCKS
SOME SOFT ROCKS MAY HAVE NO OR VERY FEW JOINTS AND
SHOULD THEREFORE BY DEFINITION HAVE A HIGH RQD
VALUE.
IN SUCH ROCKS DEFORMATION MAY BE INDEPENDENT OF
JOINTS AND THIS IS DESCRIBED IN Q-SYSTEM BY USING A
HIGH SRF VALUE.
IF THE ROCKS ARE WEAKLY CONSOLIDATED OR STRONGLY
WEATHERED AND APPEARS AS SOIL THE RQD VALUE WILL BE
0 EVEN IF NO JOINT SEEMS TO EXIST.

27. LIMITATIONS OF THE RQD
• • RQD GIVES NO INFORMATION OF THE CORE PIECES < 10CM
EXCLUDED, I.E. IT DOES NOT MATTER WHETHER THE
• DISCARDED PIECES ARE EARTH-LIKE MATERIALS OR FRESH
ROCK PIECES UP TO 10CM LENGTH
• GIVES WRONG VALUES WHERE JOINTS CONTAIN THIN CLAY
FILLINGS OR WEATHERED MATERIAL

28. • • DOES NOT TAKE DIRECT ACCOUNT OF JOINT ORIENTATION
• • RQD = 0 WHERE THE JOINT INTERCEPT (DISTANCE
BETWEEN THE JOINTS IN THE DRILL CORES) IS 10CM OR
LESS, WHILE RQD = 100 WHERE THE DISTANCE IS 11CM OR
MORE.

29. JOINT SET NUMBER JN
SHAPE AND SIZE OF THE BLOCKS IN A ROCK MASS DEPEND ON THE JOINT GEOMETRY.
THERE WILL OFTEN BE 2-4 JOINT SETS AT A CERTAIN LOCATION. JOINTS WITHIN A JOINT SET WILL
BE NEARLY PARALLEL TO ONE ANOTHER AND WILL DISPLAY A CHARACTERISTIC JOINT SPACING.
 JOINTS THAT DO NOT OCCUR SYSTEMATICALLY OR THAT HAVE A SPACING OF SEVERAL METERS
ARE CALLED RANDOM JOINTS.
HOWEVER, THE EFFECT OF SPACING STRONGLY DEPENDS ON THE SPAN OR HEIGHT OF THE
UNDERGROUND OPENING.
 IF MORE THAN ONE JOINT BELONGING TO A JOINT SET APPEARS IN THE UNDERGROUND
OPENING, IT HAS AN EFFECT ON THE STABILITY AND SHOULD BE REGARDED AS A JOINT SET.

30. IN ORDER TO GET AN IMPRESSION OF THE JOINT PATTERN THE
ORIENTATION OF A NUMBER OF JOINTS CAN BE MEASURED AND
PLOTTED ON TO A STEREO NET AS SHOWN IN FIGURE.
n
One joint set J = 2
Two joint set Jn=4

31. n
n
n
n
Two joint sets J = 4
Three joint sets J = 9
> Three joint sets J = 12
Columnar jointing with three joint directions, but J = 4
Figure 2 Different joint patterns shown as block diagrams and in stereonets.
Note:
The number of joint directions is not always
the same as the number of joint sets

32. TABLE JOINT SET NUMBERS.
Condition Jn
Massive, Non or few Joints 0.5 – 1.0
One Joint Set 2
One joint set plus random 3
Two joint sets 4
Two joint sets plus random 6
Three joint sets 9
Three joint set plus random 12
Four or more joint sets,
random, heavily jointed,
“sugar cube” , etc.
15
Crushed rock, earth like 20

33. JOINT ROUGHNESS NUMBER (JR)
JOINT FRICTION DEPENDS ON THE CHARACTER OF THE JOINT WALL
SURFACES, IF THEY ARE UNDULATING, PLANAR, ROUGH OR
SMOOTH. THE JOINT ROUGHNESS NUMBER DESCRIBES THESE
CONDITIONS. THE DESCRIPTION IS BASED ON ROUGHNESS IN TWO
SCALES:
 THE TERMS ROUGH, SMOOTH AND SLICKENSIDE REFER TO SMALL
STRUCTURES IN A SCALE OF CENTIMETERS OR MILLIMETERS. THIS
CAN BE EVALUATED BY RUNNING A FINGER ALONG THE JOINT
WALL; SMALL SCALE ROUGHNESS WILL THEN BE FELT.
IT IS ALSO POSSIBLE TO MEASURE THE ROUGHNESS BY A SIMPLE
INSTRUMENT SO CALLED PROFILOMETER.

34. Stepped
I Rough
II Smooth
III Slickensided
Undulating
IV Rough
V Smooth
VI Slickensided
Planar
VII Rough
VIII Smooth
Scale
dm - m mm - cm

35. Profilometer or Surface roughness tester

36. LARGE SCALE ROUGHNESS IS MEASURED ON A DM TO M
SCALE AND IS MEASURED BY LAYING A 1 M LONG RULER
ON THE JOINT SURFACE TO DETERMINE THE LARGE
SCALE ROUGHNESS AMPLITUDE.
THE TERMS STEPPED, UNDULATING AND PLANAR ARE
USED FOR LARGE SCALE ROUGHNESS.
Jr =
max. amplitude (amax) from
planarity
length of joint (L)

37. JOINT ALTERATION NUMBER (JA)
IN ADDITION TO THE JOINT ROUGHNESS THE JOINT INFILL
WILL BE SIGNIFICANT FOR JOINT FRICTION.
WHEN CONSIDERING JOINT INFILL, TWO FACTORS ARE
IMPORTANT; THICKNESS AND MINERAL COMPOSITION.
IN THE DETERMINATION OF A JOINT ALTERATION NUMBER,
THE JOINT INFILL IS DIVIDED INTO THREE CATEGORIES BASED
ON THICKNESS.
a) ROCK WALL CONTACT
b) ROCK WALL CONTACT BEFORE 10 CM OF SHEAR
DEFORMATION
c) NO ROCK WALL CONTACT DURING SHEAR DEFORMATION.
WITHIN EACH OF 3 CATEGORIES THE JR VALUE ARE
EVALUATED BASED ON THE MINERAL CONTENT OF THE INFILL
ACCORDING TO TABLE GIVEN:

38. A) ROCK WALL CONTACT (NO MINERAL
FILLING)
Sr
.n
o
Alteration of joint number angle Valu
e of
Ja
a Tightly healed , hard , non-softening 0.75
b Unaltered joint walls, surface staining
only
25-35 1
c Slightly altered joint walls, Non-
softening mineral coating : sandy
particles, clay-free disintegrated rock
etc.
25-30 2
d Silty or sandy clay coating , small clay
fraction
20-25 3

39. a Sandy particles , clay-free disintegrated
rock etc.
25-30 4
b Strongly over consolidated non-
consolidated non-softening , clay mineral
filling(<5mm thickness)
16-24 6
c Medium or low over-consolidation clay
mineral filling(<5mm thickness)
12-16 8
d Swelling clay filling i.e. montmorillonite. 6-12 8-12
B) ROCK WALL CONTACT BEFORE
10CM SHEAR ( THIN MINERAL FILLING)
SR.
NO
Angle
Ja

40. a Zones or bands of disintegrated or crush
rock.
16-24 6
b Zones or bands of clay, disintegrated or
crush rock.
12-16 8
c Zones or bands of clay, disintegrated or
crush rock. Swelling clay it depend upon
on % of swelling clay size paticles.
6-12 8-12
d Thick continuous zones or bands of clay.
Strongly over consolidated.
12-16 10
e Thick continuous zones or bands of clay.
Medium to low over consolidation.
12-16 13
f Thick continuous zones or bands of clay,
it depend upon on % of swelling clay-size
particles.
6-12 13-20
C) NO ROCK WALL CONTACT
SR.
NO
Description Angle
Ja

41. 0 10 20 30 cm
Rock-wall contact
Rock-wall contact before 10 cmshear
No rock-wall contact when sheared
Fig showing rock wall with
and without contact

42. JOINT WATER REDUCTION
FACTOR (JW)
• JOINT WATER MAY SOFTEN OR WASH OUT THE
MINERAL INFILL AND THERE BY
REDUCE THE FRICTION ON THE JOINT PLANES.
• WATER PRESSURE MAY REDUCE THE NORMAL
STRESS ON THE JOINT WALLS CAUSE THE
BLOCKS TO SHARE MORE EASILY
•

43. FACTORS UPON WHICH JW REDUCTION
DEPENDS
• INFLOW
• WATERPRESSUREOBSERVEDINANUNDERGROUNDOPENING.
DIFFERENTVALUESOFJWAREREPRESENTEDINTHETABLEGIVENINTHENEXT
SLIDE

44. TABLE OF JW REDUCTION FACTOR
Joint water reduction factor Values of
Jw
Dry excavation or minor inflow (Humid or a few drips) 1.0
Medium inflow, occasional outwash of joint fillings
(many drips/rain)
0.66
Jet inflow or high pressure incompetent rock with
unfilled joints
0.5
Large inflow or high pressure considerable outwash of
joint fillings
0.33

45. JW IN RELATION TO AND CHANGING WATER
INFLOW
• WATERINFLOWISOBSERVEDINUNDERGROUNDOPENING.
• THEINFLOWMAYALSOORIGINATEFROMTHEINVERTANDMAYBEDIFFICULTTO
OBSERVE.
• THESURROUNDINGMASSMAYBEDRAINEDWITHNOVISIBLEINFLOWFOR
SOMETIMEAFTEREXCAVATION.

46. JW IN RELATION TO AND CHANGING WATER
INFLOW
• INAUNDERGROUNDOPENINGNEARTHESURFACE,INFLOWMAYVARYWITHTHE
SEASONANDAMOUNTOFPRECIPITATION.
• INFLOWMAYINCREASEINPERIODSWITHPRECIPITATIONSANDDECREASEINDRY
SEASON.
• THESECONDITIONSMUSTBEKEPTINMINDWHENDETERMININGTHEJOINTWATER
FACTORREDUCTION

47. EXAMPLE
• GROUTINGWILLREDUCEINFLOWANDTHEJOINTFACTORREDUCTIONVALUESHOULD
THANBEINCREASEDACCORDINGTO REDUCTIONOFTHEINFLOW.
• INSOMECASESTHEUNDERGROUNDOPENINGMAYBEDRYJUSTAFTERTHE
EXCAVATIONBUTINFLOWWILLDEVELOPOVERTIME.
• INOTHERCASELARGEINFLOWJUSTAFTEREXCAVATIONMAYDECREASEAFTER
SOMETIME

48. DISTINGUISHING BETWEEN TWO JW VALUES
• JW=1 FORSINGLEDROPOFWATERDRIPPINGINALIMITEDAREAOFEXCAVATION.
• JW=0.66FORASMALLJETSOFWATERINACONCENTRATEDAREAORFREQUENT
DRIPPINGINAWIDEAREA.

49. SRF
• SRFDESCRIBESTHERELATIONBETWEENSTRESSANDROCKSTRENGTHAROUNDAN
UNDERGROUNDOPENING.
• THEEFFECTSOFSTRESSESCANUSUALLYBEOBSERVEDINANUNDERGROUNDOPENINGAS
SPALLING.SLABBING,DEFORMATION,SQUEEZING
• BOTHSTRESSESANDSTRENGTHOFTHEROCKMASSCANBEMEASUREDANDSRFCANBE
CALCULATED FROMTHERELATIONSHIPBETWEENTHEUNIAXIALCOMPRESSIVESTRENGTHAND
THEMAJORPRINCIPLESTRESS.

50. SRF IN COMPETENT ROCK
• THERELATIONBETWEENTHEROCKSTRENGTHANDSTRESSISACCURATEFORTHESRF-
VALUE.
• MODERATESTRESSESWILLGENERALLYBEMOSTFAVORABLEFORTHESTABILITYAND
SRFWILLBE1.
• MODERATELYHIGHHORIZONTALSTRESSESMAYBEFAVORABLEFORTHECROWNAND
SRFVALUEOF0.5MAYBEUSEDINSAMECASE.

51. • LOW STRESSES, WHICH WILL OFTEN BE THE CASE WHEN UNDERGROUND
EXCAVATION HAS A SMALL OVERBURDEN, MAY RESULT IN REDUCED
STABILITY DUE TO DILATION. SRF IN SUCH CASE WILL BE 2.5 OR EVEN 5.0.
• SPALLING AND ROCK BURST MAY OCCUR AT VARY HIGH STRESSES AND SRF
VALUES UP TO 400 MAY BE USED IN SOME EXTREME SITUATIONS.

52. • INCASEWHEREHIGHSTRESSESARECOMBINEDWITHJOINTEDROCKS,THEROCK
MASSCOMPRESSIVESTRENGTHISMOREIMPORTANTTHENTHECOMPRESSIVE
STRENGTHOFINTACTROCK.
• INCASESWHERETHEROCKMASSISHEAVILYJOINTEDANDUNDERHIGHSTRESS,A
SQUEEZINGEFFECTISMORELIKELYTOOCCURTHANSPALLING.

53. SRF IN SQUEEZING ROCK
• SQUEEZINGROCKSMEANSROCKMASSESWHEREPLASTIC
DEFORMATIONTAKEPLACEUNDERTHEINFLUENCEOFHIGHROCK
STRESSES.
• THISWILLHAPPENINSOFTROCKSWHENSTRESSESEXCEEDTHE
ROCKMASSSTRENGTH.
• INVERYSOFTROCKSWITHFEWORNOJOINTS,THESTABILITYWILL
DEPENDONTHERELATIONBETWEENTHEROCKCOMPRESSIVE
STRENGTHANDTHESTRESSES.

54. SRF IN SWELLING ROCKS
• SWELLING IS A CHEMICAL PROCESS, INITIATED WHEN WATER IS ADDED TO
ROCKS CONTAINING MINERALS WITH SWELLING PROPERTIES.
• IT MAY BE NECESSARY TO CARRY OUT LABORATORY TEST TO DETERMINE
THE POTENTIAL SWELLING PRESSURE AS A BASIS FOR THE SRF VALUE.
• MOST COMMON SWELLING MINERAL ARE CLAY MINERALS I.E.
MONTMORILLONITE.

55. IMPORTANT APPLICATIONS OF Q SYSTEM
(I) CALCULATION OF COHESIVE COMPONENT
 THE Q SYSTEM CAN BE USED TO CALCULATE COHESIVE
COMPONENT OF ROCK MASS BY USING A SIMPLE QC-
FORMULATION.
IT HAS ADVANTAGE OF NOT REQUIRING SOFTWARE FOR ITS
CALCULATION BECAUSE IT ALREADY EXISTS IN THE
CALCULATION OF THE QC VALUE. THEY ARE DEFINED AS
FOLLOWS:
COHESIVE COMPONENT (CC) = RQD/JN × 1/SRF × ΣC /100

56. CALCULATION OF FRICTIONAL
COMPONENT
THE Q SYSTEM CAN ALSO BE EMPLOYED TO CALCULATE
COHESIVE COMPONENT OF ROCK MASS BY USING A SIMPLE
QC-FORMULATION.
FRICTIONAL COMPONENT OF ROCK MASS IS GIVEN AS
FRICTIONAL COMPONENT (FC) = TAN–1[JR /JA × JW]

57. CONCLUSIONS
• CLASSIFICATION SYSTEM LIKE Q-SYSTEM MAY BE A USEFUL TOOL FOR ESTIMATING THE NEED
FOR TUNNEL SUPPORT AT THE PLANNING STAGE, PARTICULARLY FOR TUNNELS IN HARD AND
JOINTED ROCK MASSES WITHOUT OVERSTRESSING.
• THERE ARE, HOWEVER, A NUMBER OF RESTRICTIONS THAT SHOULD BE APPLIED IF AND WHEN
THE SYSTEM IS GOING TO BE USED IN OTHER ROCK MASSES AND IN COMPLICATED GROUND
CONDITIONS. SO FAR SUCH RESTRICTIONS HAVE NOT BEEN MUCH DISCUSSED IN AVAILABLE
LITERATURE.
• IN THIS PRESENTATION A CRITICAL EVALUATION OF THE PARAMETERS THAT MAKE UP THE
SYSTEM, IS CARRIED OUT.
• POTENTIAL USERS OF THE Q-SYSTEM SHOULD CAREFULLY STUDY THE LIMITATIONS OF THIS
SYSTEM AS WELL AS OTHER CLASSIFICATION SYSTEMS THEY MAY WANT TO APPLY, BEFORE
TAKING THEM INTO USE.