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

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

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.

MASSIVE ROCK JOINTED ROCK

Rock Quality

Heavily Jointed Rock

Massive Rock

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.

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.

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.

• 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.

ROCK MASS STABILITY

• ROCK MASS STABILITY IS INFLUENCED BY

• 1) DEGREE OF JOINTING

• 2) JOINT FRICTION

• 3) STRESS

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

QUOTIENT FACTORS

I. RELATIVE BLOCK SIZE (RQD/JN)

II. INTER-BLOCK SHEAR STRENGTH (JR/JA)

III. ACTIVE STRESSES (JW/SRF)

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.

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.

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.

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.

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.

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.

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%.

RQD-VALUES AND VOLUMETRIC JOINTING

• 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

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

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.

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.

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

• • 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.

JOINT SET NUMBER JNSHAPE 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.

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

O ne joint set J = 2

Two joint set Jn=4

n

n

n

n

Two joint sets J = 4

Three joint sets J = 9

> Three joint sets J = 12

Colum nar jointing w ith 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

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

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.

20

Stepped

I Rough

II Smooth

III Slickensided

Undulating

IV Rough

V Smooth

VI Slickensided

Planar

VII Rough

VIII Smooth

Scale

dm - m mm - cm

Profilometer or Surface roughness tester

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)

    

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:

A) ROCK WALL CONTACT (NO MINERAL FILLING)

Sr.no

Alteration of joint number angle Value 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

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

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 CONTACTSR.NO

Description Angle Ja

0 10 20 30 cm

R ock-w a ll contact

Rock-wall contact before 10 cm shear

N o rock -w a ll contact w hen sheared

Fig showing rock wall with and without contact

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

•

FACTORS UPON WHICH JW REDUCTION DEPENDS

• INFLOW

• WATER PRESSURE OBSERVED IN AN UNDERGROUND OPENING.

DIFFERENT VALUES OF JW ARE REPRESENTED IN THE TABLE GIVEN IN THE NEXT SLIDE

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

JW IN RELATION TO AND CHANGING WATER INFLOW

• WATER INFLOW IS OBSERVED IN UNDERGROUND OPENING.

• THE INFLOW MAY ALSO ORIGINATE FROM THE INVERT AND MAY BE DIFFICULT TO OBSERVE.

• THE SURROUNDING MASS MAY BE DRAINED WITH NO VISIBLE INFLOW FOR SOMETIME AFTER EXCAVATION.

JW IN RELATION TO AND CHANGING WATER INFLOW

• IN A UNDERGROUND OPENING NEAR THE SURFACE, INFLOW MAY VARY WITH THE SEASON AND AMOUNT OF PRECIPITATION.

• INFLOW MAY INCREASE IN PERIODS WITH PRECIPITATIONS AND DECREASE IN DRY SEASON.

• THESE CONDITIONS MUST BE KEPT IN MIND WHEN DETERMINING THE JOINT WATER FACTOR REDUCTION

EXAMPLE

• GROUTING WILL REDUCE INFLOW AND THE JOINT FACTOR REDUCTION VALUE SHOULD THAN BE INCREASED ACCORDING TO REDUCTION OF THE INFLOW.

• IN SOME CASES THE UNDERGROUND OPENING MAY BE DRY JUST AFTER THE EXCAVATION BUT INFLOW WILL DEVELOP OVERTIME.

• IN OTHER CASE LARGE INFLOW JUST AFTER EXCAVATION MAY DECREASE AFTER SOMETIME

DISTINGUISHING BETWEEN TWO JW VALUES

• JW=1 FOR SINGLE DROP OF WATER DRIPPING IN A LIMITED AREA OF EXCAVATION.

• JW=0.66 FOR A SMALL JETS OF WATER IN A CONCENTRATED AREA OR FREQUENT DRIPPING IN A WIDE AREA.

SRF

• SRF DESCRIBES THE RELATION BETWEEN STRESS AND ROCK STRENGTH AROUND AN UNDERGROUND OPENING.

• THE EFFECTS OF STRESSES CAN USUALLY BE OBSERVED IN AN UNDER GROUND OPENING AS SPALLING. SLABBING, DEFORMATION, SQUEEZING

• BOTH STRESSES AND STRENGTH OF THE ROCK MASS CAN BE MEASURED AND SRF CAN BE CALCULATED FROM THE RELATIONSHIP BETWEEN THE UNIAXIAL COMPRESSIVE STRENGTH AND THE MAJOR PRINCIPLE STRESS.

SRF IN COMPETENT ROCK

• THE RELATION BETWEEN THE ROCK STRENGTH AND STRESS IS ACCURATE FOR THE SRF-VALUE.

• MODERATE STRESSES WILL GENERALLY BE MOST FAVORABLE FOR THE STABILITY AND SRF WILL BE 1.

• MODERATELY HIGH HORIZONTAL STRESSES MAY BE FAVORABLE FOR THE CROWN AND SRF VALUE OF 0.5 MAY BE USED IN SAME CASE.

• 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.

• IN CASE WHERE HIGH STRESSES ARE COMBINED WITH JOINTED ROCKS, THE ROCK MASS COMPRESSIVE STRENGTH IS MORE IMPORTANT THEN THE COMPRESSIVE STRENGTH OF INTACT ROCK.

• IN CASES WHERE THE ROCK MASS IS HEAVILY JOINTED AND UNDER HIGH STRESS, A SQUEEZING EFFECT IS MORE LIKELY TO OCCUR THAN SPALLING.

SRF IN SQUEEZING ROCK

• SQUEEZING ROCKS MEANS ROCK MASSES WHERE PLASTIC DEFORMATION TAKE PLACE UNDER THE INFLUENCE OF HIGH ROCK STRESSES.

• THIS WILL HAPPEN IN SOFT ROCKS WHEN STRESSES EXCEED THE ROCK MASS STRENGTH.

• IN VERY SOFT ROCKS WITH FEW OR NO JOINTS, THE STABILITY WILL DEPEND ON THE RELATION BETWEEN THE ROCK COMPRESSIVE STRENGTH AND THE STRESSES.

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.

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

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]

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.