International Journal of Civil Engineering (IJCE) ISSN(P): 2278-9987; ISSN(E): 2278-9995 Vol. 2, Issue 5, Nov 2013, 9-16 © IASET
BLASTABILITY INDEX ON POOR QUALITY ROCK MASS M. CHATZIANGELOU1 & B. CHRISTARAS2 1
Department of Civil Infrastructure Engineering, School of Technological Applications of Thessaloniki, Greece 2
Department of Geology, Aristotle University of Thessaloniki, Thessaloniki, Greece
ABSTRACT The present paper proposes a new combined classification system connecting the quality and blastability of poor and friable rock mass, heavily broken with mixture of angular and rounded rock pieces. The proposed methodology and research that result in the Blastability Quality System (BQS) are described, and three useful diagrams of the above new system aroused from our estimations. The proposed BQS is an easily and widely used tool as it is a quickly calculator for blasting and rock mass quality. Taking into account our research calculations and the parameters of BQS, we came to some conclusions for the relation of the blast ability index magnitude with the space and orientation of discontinuities.
KEYWORDS: Blastability, Blasting, Classification System, Rock Mass INTRODUCTION The property, which is referred as “blastability” of a rock mass, determines how easy is to explore a rock mass under specified blast design, explosive characteristics and specified legislative constraints depending on the site specifics. Two different rock masses, when are subjected to identical blast geometry and energy input from explosives, produce quite different degrees of fragmentation (Ajoy & Akhilesh, 2012). This is because they have different resistance to fragmentation by blasting (Blanco & Kumar, 2012).Rock mass comprises of several different rock types and is affected by different stages of alteration in varying stress conditions. Blast ability appears to be a kind of intrinsic property, like the hardness of a rock and, apart from the possibility of blast fragmentation from previous blasting events, it is uncontrollable. Many rock mass quality classification systems (RQD, Q, RMR, GSI) have been developed for drilling and excavation ability estimation. The present paper is trying to create a new system, connecting the quality and blastability of rockmass, which can be, easily, used as an in situquick method, for tunnel excavation, in order to estimate quickly the explosive results, in addition to drilling and excavation methods. The rock mass, used in this study, is poor and friable, shared with lack of blockiness due to the close spacing of weak schistosity or sheer planes and disintegrated with poorly interlocked, heavily broken rock mass with mixture of angular and rounded rock pieces. Although the quality is very poor, a light blast may be needed as the small rock pieces are tightly connected.
ALREADY KNOWN APPROACH; BLASTABILITY INDEX CONCERNING ROCK MASS CLASSIFICATION SYSTEMS The factors, which influence the blasting results, fall into two groups. The first group refers to the intact rock properties, which include strength, hardness, elasticity, deformability, density of rock, etc. These properties depend on rock texture, internal bonds, composition and distribution of minerals forming the rock (Zhang et al., 2011). The second group refers
to
the
discontinuity
structure
that
involves
orientation,
spacing
and
extent
of
discontinuities
(Singh & Sinha, 2012). The discontinuity structure has been created by a range of long-term geological processes.
10
M. Chatziangelou & B. Christaras
The coefficient of the Blast ability Index (BI) is a quantitative measure of the blastability of a rock mass. It is more advantageous, the coefficient BI to be determined before blasting, in order to help with the blast design of an excavation operation. Without any realistic chance, in the short term of a practical analytical solution of defining the value of a BI, for a given rock mass as a function of material properties, the development of a comprehensive assessment system for quantifying the blastability of rock masses is appear to have great potential(Latham and Lu, 1999). Blastability index (BI) is used for the description of ease of blasting and it is also related to power factor. When the BI is lower to 8, the ease of blasting is described as “very difficult”. When the BI range is between 8 and 13, the ease of blasting is described as “difficult”. When the BI range is between 13 and 20, the ease of blasting is described as “moderate”. When the BI range is between 20 and 40, the ease of blasting is described as “easy”. When the BI is higher than 40, the ease of blasting is described as “very easy”. The above parameters are closely related to excavation cost which is depended on the explosion, vibration, alteration, powder creation etc. (Kaushik & Phalguni, 2003). In our study, BI is preferred to be calculated based on the following formula (Lilly, 1986), based on rock mass description, joint density and orientation, specific gravity and hardness: BI = 0.5 x (RMD+JPS+JPO+SGI+H) Where, BI = Blastability Index RMD (Rock mass Description)
JPS (Joint Plan Spacing)
JPO (Joint Plane Orientation)
SGI = Specific Gravity Influence
=
10, for Powdery/Friable rockmass
=
20, for Blocky rockmass
=
50, for Totally Massive rockmass
=
10, for Closely Spacing (<0.1m)
=
20, for Intermediate (0.1-1.0m)
=
50, for Widely Spacing (>1.0m)
=
10, for Horizontal
=
20, for Dip out of the Face
=
30, for Strike Normal to Face
=
40, for Dip into Face
=
25 x Specific Gravity of rock (t/m3) – 50
H = Hardness in Mho Scale (1-10) Considering that blastability index is based on rock mass description, joint density and orientation, evokes the same parameters that the Rock Mass Rating System - RMR (Bieniawski, 1989) is also based on. Also, the above classification can be described by the Geological Strength Index – GSI (Hoek, 1994).
NEW APPROACH CONNECTING BLASTABILITY AND QUALITY ABILITY The lower part of the GSI diagram, which refers to i) laminated and sheared rock mass, with lack of blockiness due to the close spacing of weak schistosity or sheer planes and ii) disintegrated rock mass, with poorly interlocked,
11
Blastability Index on Poor Quality Rock Mass
heavily broken rock with mixture of angular and rounded rock pieces, isdivided into eight parts (Figure 1); A -for GSI about 0-12, B – for GSI about 12-23, C – for GSI about 22-23, D – for GSI 7-17, E – for GSI about 18-28, F – for GSI
STRUCTURE
DECREASING SURFACE QUALITY
90
INTACT OF MASSIVE intact rock specimens of massive in situ rock with few widely spaced discontinuities
VERY POOR Slickenside, highly weathered surfaces with soft clay coatings or fillings
POOR Slickensided, highly weathered surfaces with compact coatings of rillings or angular fragments
FAIR Smooth, moderately weathered and altered surfaces
GOOD Rough, slightly weathered, iron stained surfaces
VERY GOOD Very rough, fresh unweathered surfaces
GEOLOGICAL STRENGTH INDEX FOR JOINTED ROCKS (Hoek and Marinos, 2000) From the lithology, structure and surface conditions of the discontinuities, estimate the average value of GSI. Do not try to be too precise. Quoting a range from 33 to 37 is more realistic than stating that GSI=35. Note that the table does not apply to structurally controlled failures.Where weak planar structural planes are present in an unfavourable orientation with respect to the excavation face, these will dominate the rock mass behaviour. The shear strength of surfaces in rocks that are prone to deterioration as a result of changes in moisture content will be reduces if water is present.When working with rocks in the fair to very poor categories, a shift to the right may be made for wet conditions. Water pressure is dealt with by effective stress analysis.
SURFACE CONDITIONS
about 16-36, G – for GSI 35-43, H - for GSI 42-50.
N/A
N/A
VERY BLOCKY - interlocked, partially disturbed mass with multi-faceted angular blocks formed by 4 or more joint sets
BLOCKY / DISTURBED / SEAMY- folded with angular blocks formed by many intersecting discontinuity sets. Persistence of bedding planes or schistosity
DISINTEGRATED - poorly interlocked, heavily broken rock mass with mixture of angular and rounded rock pieces
DECREASING INTERLOCKING OF ROCK PIECES
80 BLOCKY - well interlocked undisturbed rock mass consisting of cubical blocks formed by three intersecting discontinuity sets
70 60
50
40
30
H
G
F
20
Å
D 10
LAMINATED / SHEARED Lack of blockiness due to close spacing of weak schistosity of shear planes
N/A
N/A
C
Â
Á
Figure 1: Eight Parts Division of GSI Diagram Taking into account the blast ability parameters, the BI is calculated for every possible combination of the above parameters, which refers to powdery/friable rock mass. That means RMD is equal to 10 (powdery / friable rock mass). JPS is used equal to 10 for closely spacing, 20 for intermediate spacing and 50 for widely spacing. JPO is used equal to 10 for horizontal discontinuities, 20 for inclined discontinuities, where the excavation drives against dip direction, 30 for inclined discontinuities with strike parallel to face, 40 for inclined discontinuities, where the excavation drives with dip direction. SGI is calculated using specific gravity of rocks from 1 t/m3 to 3 t/m3.Mohs hardness scale (H) is estimated using the average price of Mohs hardness scale of the minerals which compose the rock mass. For every possible RMR combination, new combinations are calculated in addition to GSI range. Subsequently, we group the above estimations and we come to the conclusion of specified RMR range on GSI parts, taking into account rock mass hardness, discontinuity spacing and orientation. Also, the range of Blastability Index is calculated. Three useful diagrams of composite rock mass quality systems (GSI and RMR) and blastability index (BI) result from the above estimations (Figure 2-4).
BLASTABILITY QUALITY SYSTEM (BQS) The above new BQ System (Figure 2-4) connects the rock mass classification systems RMR and GSI, structural data, hardness of rock mass, and blastability index. Initially, the discontinuities spacing is characterized; for close spaced discontinuities, with spacing lower than 0,1m, figure 2 is used. For intermediate spaced discontinuities, with spacing between 0,1m and 1m, figure 3 is used. For widely spaced discontinuities, with spacing higher than 1m, figure 4 is used.
12
M. Chatziangelou & B. Christaras
Looking the lower part of the figures 2, 3, and 4, there is a combined Geological Strength Index diagram with RMR areas for every rock mass classification according to BI. So, having completed the above classification, inputting the spacing and the orientation of discontinuities combined with rock mass hardness, the Blastability Index (BI) range can easily be determined. At the final stage we can input structure and surface conditions in order to estimate Geological Strength Index (GSI) and Rock Mass Rating (RMR). This is a very useful approach as it includes the most useful characteristics of rock mass, which are easily estimated and used in situ; looking a rock mass picture can easily characterize discontinuities spacing and orientation. Also, we can estimate rock mass hardness using a Schmidt Hammer. In addition to BQS easily and wide use, it is a quickly calculator for BI and rock mass quality, which make our choice of excavation, blast and support measures quicker.
EXAMPLES OF USING BQ SYSTEM The excavations, during the construction of Asprovalta-Strymona’s part of Egnatia Highwayin Northern Greece, were very difficult because of rock mass quality. Rock mass was consisted of weathered and cracked gneiss with pegmatitic veins, or cracked marbles. There was no cohesion between rock mass pieces, so as they formed potential sliding wedges. When the face area of disintegrated wedges had been uncovered, the sliding was happened suddenly (Christaras et al, 2001). So, although the use of blasting was needed, the explosion had to be very careful, so as no accident may happen. Looking at the rock mass example on figure 5, rock mass has close spaced discontinuities. Using the figure 2, the orientation of discontinuities may be determined. Looking again figure 5, strike is parallel to tunnel axis. At next stage, rock mass hardness needs to be also determined. So, as the rock mass is very weathered, it is extremely soft to medium hard. Looking the figure 2, the BI is estimated14-41 and blasting is characterized as moderate to easy. That means, a small amount of explosives could be used in order to help rock mass pieces to move, helping the excavation. could be used in order to help rock mass pieces to move, helping the excavation.
CLOSE SPACED DISCONTINUITIES Strike perpendicular to tunnel axis Gradient discontinuities
STRUCTURE
DECREASING SURFACE QUALITY
DECREASING SURFACE QUALITY 50
40
(6)
50
VERY POOR
(4)
POOR
FAIR
(3)
(5)
(1)
DECREASING SURFACE QUALITY RMR: 0-20
40
VERY GOOD
VERY POOR
(4)
POOR
(3)
FAIR
(2)
(5)
(1)
ΒΙ = 4-37
DECREASING SURFACE QUALITY RMR: 0-20 20
40
VERY GOOD
VERY POOR
(4)
POOR
FAIR
(2)
GOOD
(3)
(5)
(1)
VERY GOOD
(5) (4)
VERY POOR
FAIR
POOR
(3)
(2)
GOOD
ΒΙ = 19-47
50
RMR: 0-20 20
Excavation drives against dip direction
Excavation drives with dip direction
ΒΙ = 17-42
(1)
VERY GOOD
GEOLOGICAL STRENGTH INDEX (GSI)
SURFACE CONDITIONS
ΒΙ = 14-41
Horizontal and gradient discontinuities
(2)
Hard and very hard rockmass (MOHS 8-10)
GOOD
Extremely soft to medium hard rockmass (MOHS 0-7)
GOOD
Strike parallel to tunnel axis
50
RMR: 0-20 20
40
20
DISINTEGRATED
RMR: 41-60
RMR: 41-60
30
N/A
30
RMR: 21-40
RMR: 21-40
10
10
10
(7)
LAMINATED / SHEARED
RMR: 41-60
30
RMR: 21-40
N/A
N/A
N/A
N/A
RMR: 0-20 (1)
RMR: 0-20 (5)
Very rough, fresh unweathered surfaces
N/A
RMR: 41-60
(6)
(3)
N/A
RMR: 0-20
Slickenside, highly weathered surfaces with soft clay coatings or fillings Poorly interlocked, heavily broken rock mass with mixture of angular and rounded rock pieces
Smooth, moderately weathered and altered surfaces (4)
Slickensided, highly weathered surfaces with compact coatings of rillings or angular fragments
(7)
Lack of blockiness due to close spacing of weak schistosity of shear planes
Figure 2: BQS for Close Spaced Discontinuities
RMR: 21-40 10
N/A
(2)
Rough, slightly weathered, iron stained surfaces
30
RMR: 0-20
13
Blastability Index on Poor Quality Rock Mass
INTERMEDIATE SPACED DISCONTINUITIES Gradient discontinuities
STRUCTURE
RMR: 21-40
(6)
RMR: 0-20 20
RMR: 21-40
40
DECREASING SURFACE QUALITY
DECREASING SURFACE QUALITY 50
RMR: 0-20 20
RMR: 21-40
VERY POOR
(4)
FAIR
POOR
(2)
GOOD
(3)
(5)
(1)
(5)
VERY POOR
(4)
FAIR
POOR
(3)
(2)
GOOD
DECREASING SURFACE QUALITY
DECREASING SURFACE QUALITY
50
RMR: 0-20 40
ΒΙ = 19-44
(1)
VERY GOOD
VERY POOR
(4)
FAIR
POOR
(2)
GOOD
(3)
(5)
(1)
VERY GOOD
(5)
VERY POOR
(4)
POOR
(3)
(2)
GOOD
ΒΙ = 24-52
50 40
From extremely soft to soft rock mass (MOHS 0-4)
ΒΙ = 17-47
(1)
(5)
VERY GOOD
VERY POOR
(4)
FAIR
POOR
(3)
(2)
GOOD
DECREASING SURFACE QUALITY 50
RMR: 0-20 20
Strike parallel to tunnel axis Strike perpendicular to tunnel axis when excavation drives with dip direction
Hard and very hard rockmass (MOHS 8-10)
ΒΙ = 14-46
(1)
VERY GOOD
(5)
VERY POOR
(4)
POOR
(3)
FAIR
GOOD
(2)
VERY GOOD
DECREASING SURFACE QUALITY 50 40
Extremely soft (when strike is perpendicular to tunnel axis) to medium hard rockmass (MOHS 0-7)
ΒΙ = 11-37
(1)
SURFACE CONDITIONS
ΒΙ = 9-34
GEOLOGICAL STRENGTH INDEX (GSI)
Strike parallel to tunnel axis and strike perpendicular to tunnel axis when excavation drives against dip direction
Medium hard to very hard rockmass (MOHS 5-10)
FAIR
Extremely soft to soft rockmass (MOHS 0-4)
VERY GOOD
Horizontal discontinuities
50 40
20
40
20
RMR: 21-40
20
DISINTEGRATED
RMR: 41-60
30
RMR: 41-60
RMR: 41-60
30
30
30
RMR: 41-60
30
30
RMR: 41-60
RMR: 21-40
RMR: 61-80
10
10
10
RMR: 41-60
10
(7)
10
10
RMR: 21-40
LAMINATED / SHEARED
N/A
N/A
N/A
N/A
N/A
RMR: 0-20
N/A
N/A
(5)
Very rough, fresh unweathered surfaces
N/A
RMR: 0-20
RMR: 0-20
(1)
N/A
N/A
N/A
RMR: 0-20
N/A
RMR: 0-20
RMR: 0-20
Slickenside, highly weathered surfaces with soft clay coatings or fillings
(2)
Rough, slightly weathered, iron stained surfaces
(6)
(3)
Poorly interlocked, heavily broken rock mass with mixture of angular and rounded rock pieces
Smooth, moderately weathered and altered surfaces (4)
(7)
Slickensided, highly weathered surfaces with compact coatings of rillings or angular fragments
Lack of blockiness due to close spacing of weak schistosity of shear planes
Figure 3: BQS for Intermediate Spaced Discontinuities
WIDELY SPACED DISCONTINUITIES
STRUCTURE
RMR: 41-60
20
RMR: 21-40 30
Very rough, fresh unweathered surfaces (2) Rough, slightly weathered, iron stained surfaces (3) Smooth, moderately weathered and altered surfaces (4) lickensided, highly weathered surfaces with compact coatings of rillings or angular fragments
10
N/A
DECREASING SURFACE QUALITY
RMR: 61-80
30
10
RMR: 21-40
RMR: 61-80
RMR: 21-40 RMR: 0-20
RMR: 21-40
N/A
RMR: 41-60 RMR: 0-20
N/A
(5) VERY POOR
(3)
FAIR
(4) POOR
(1) VERY GOOD
(2) GOOD
ΒΙ = 32-62 (5) VERY POOR
FAIR
(4) POOR
(3)
(2) GOOD
(5) VERY POOR (1) VERY GOOD
(4) POOR
(3)
FAIR
(2) GOOD
(5) VERY POOR (1) VERY GOOD
FAIR
(4) POOR
Strike perpendicular to Strike parallel to tunnel axis when excavation drives with tunnel axis dip direction
ΒΙ = 42-67
50
RMR: 61-80
RMR: 41-60 RMR: 21-40
30
50 40
20
RMR: 41-60
RMR: 61-80
10
10
N/A
(3)
ΒΙ = 32-57
(2) GOOD
(5) VERY POOR (1) VERY GOOD
FAIR
(4) POOR
ΒΙ = 27-52
40
RMR: 61-80 10
N/A
Strike perpendicular to tunnel axis when excavation drives against dip direction
DECREASING SURFACE QUALITY
20 30
RMR: 41-6010
Horizontal discontinuities
50 40
20
30
N/A N/A
(3)
DECREASING SURFACE QUALITY 50
40
20
(2) GOOD
(4) POOR
(5) VERY POOR (1) VERY GOOD
(3)
FAIR
(2) GOOD
(4) POOR
(3) FAIR
(2) GOOD
(4) POOR
30
ΒΙ = 41-66
50 40
N/A N/A RMR: 0-20
ΒΙ = 31-61
DECREASING SURFACE QUALITY
20
RMR: 41-60
Hard and very hard rock mass(MOHS 8-10)
Strike parallel or Strike perpendicular to perpendicular to tunnel tunnel axis when axis when excavation excavation drives with drives against dip dip direction direction
50
40 RMR: 61-80
RMR: 41-60 N/A
(5) VERY POOR (1) VERY GOOD
(2) GOOD (3) FAIR
(1) VERY GOOD
(5) VERY POOR
(4) POOR
(3) FAIR
GOOD
ΒΙ = 26-51
50
RMR: 0-20 (1)
ΒΙ = 34-59
DECREASING SURFACE QUALITY
40
10
N/A
Horizontal discontinuities
50
RMR: 61-80
RMR: 61-80
Strike parallel to excavation axis
DECREASING SURFACE QUALITY
RMR: 21-40 20 30
(7) LAMINATED N/A SHEARED
(1) VERY GOOD
(4) POOR
(3) FAIR
(5) VERY POOR
(1)
(2) GOOD
40
(2)
ΒΙ = 39-64
DECREASING SURFACE QUALITY
50 DIS (6) INTE GRATED
Strike perpendicular to excavation axis when excavation drives with dip direction
ΒΙ = 24-54 VERY GOOD
GEOLOGICAL STRENGTH INDEX (GSI)
SURFACE CONDITIONS
Horizontal discontinuities and strike perpendicular to excavation axis when excavation drives against dip direction
Medium hard to hard rock mass(MOHS 5-8)
(5) VERY POOR (1) VERY GOOD
Extremely soft to soft rock mass (MOHS 0-4)
N/A
N/A
RMR: 41-60
RMR: 41-60
N/A RMR: 21-40
RMR: 61-80 RMR: 61-80
N/A
RMR: 21-40
40
20
30
10
N/A RMR: 21-40
30
50 40
20
20 30
RMR: 41-60
10
N/A
10
N/A RMR: 21-40
N/A RMR: 21-40
: R M R -80 61
(5) Slickenside, highly weathered surfaces with soft clay coatings or fillings (6) Poorly interlocked, heavily broken rock mass with mixture of angular and rounded rock pieces (7) Lack of blockiness due to close spacing of weak schistosity of shear planes
Figure 3: BQS for Widely Spaced Discontinuities
Figure 5: Weathered and Disintegrated Rock Mass Quality at Asprovalta – Strymona’s Part of Egnatia Highway at Northern Greece Furthermore, looking the lower part of the same figure, we combine the structure of rock mass, which is disintegrated, with the surface conditions, which are poor, estimating an RMR from 0 to 20 (as rock mass is disintegrated to blocky and not to laminated) and a GSI from 20 to 25. Taking into account the poor quality of rock mass, as it is
14
M. Chatziangelou & B. Christaras
described by RMR and GSI classification systems, the choose of rock mass locations, where the explosives were put, needed to be very careful. They could be placed where rock mass were strengthen and hard, so as the forces of the neighborhood locations remained on balance.
Figure 6: Chloritic Schist Rock Mass during Tunneling of Symbol Mountain at Strymonas-Kavala’s Part of Egnatia Highway at Northern Greece Although the quality of the excavated rock mass, during the tunneling of Symbol Mountain at Strymonas- Kavala’s part of Egnatia Highway in Northern Greece, was characterized as medium - it was consisted by gneiss, amphibolites, marbles and plutonic rocks - the chloritic schist formation, which was created because of gneiss and plutonic rocks contact, generated unexpected failure conditions (Chatziangelou et al, 2010). Chloritic schist was a hard rock mass that excavating machines could difficulty break it. So, blasting helped excavating works. But just when chloritic schist came in touch with the air, the rock mass was very quickly weathered and loose material flowed from the walls and the face of excavation. So, explorers needed to be very careful using light explosion. According to the rock mass example on figure 6, rock mass had intermediate spaced discontinuities. Using the figure 3, the orientation of discontinuities may be determined. Looking again figure 6, there are also horizontal discontinuities. Subsequently, rock mass hardness needs to be also determined. So, as the rock mass is quickly weathered and loosed, its hardness characterizes as extremely soft to soft. Looking the figure 3, the BI is estimated 9-34 and blasting is characterized as very difficult. That means, although high explosives are effective for chloritic schist braking, the pattern of explosives need to be chosen for every location, so as collapses of the roof and sliding from walls to be avoided. Furthermore, looking the lower part of the same figure, we combine the structure of rock mass, which is laminated and sheared, with the surface conditions, which are very poor, because of slickensided discontinuities with highly weathered surfaces with soft clay (chlorite) coatings, estimating an RMR from 0 to 20 (as rock mass is sheared and no way disintegrated) and a GSI from 5 to 10. Taking into account the above characterizations, the puncture of excavation’s outline was chosen, to control the pressures of blasting result.
BLASTABILITY INDEX VERSUS TO STRUCTURAL GEOLOGY Taking into account the calculations of BI for every possible structural appearance of the rockmass, we can easily result in a diagram which connects the structural description, the hardness of rockmass and BI (Figure 7), where rock mass quality 1 refers to close spaced discontinuities, horizontal formations, and inclined formations, where the excavation drives against dip direction. Rock mass quality 2 refers to intermediate spaced discontinuities and horizontal formations. Rock mass quality 3 refers to close spaced discontinuities and gradient formations, where excavation drives with dip direction. Rock mass quality 4 refers to intermediate spaced discontinuities and gradient formations. Rock mass quality 5 refers to
Blastability Index on Poor Quality Rock Mass
15
widely spaced discontinuities, horizontal formations, and soft gradient rock mass, where excavation drives against dip direction. Rock mass quality 6 refers to widely spaced discontinuities and gradient formations (except soft gradient rock mass where excavation drives against dip direction).
Figure 7: Rock Mass Quality versus to Blastability Index Looking at the above diagram, we can easily conclude that
The wider the spacing of discontinuities is, the bigger the BI is.
BI is lower in horizontal formations than in gradient formations.
BI is higher where the excavation drives with dip direction than where it drives against dip direction.
CONCLUSIONS A new Blastability Quality System (BQS) is already developed connecting rock mass quality, discontinuities orientation, hardness and Blastability Index (BI). It is a wide useful system as it can be easily applied during the excavations, helping engineers on quick estimations of rock mass quality and BI, in addition to excavation way, explores and support measures. BQS is a tool which (at the present) can be used for poor and friable rock mass, shared with lack of blockiness due to close spacing of weak schistosity or sheer planes and disintegrated with poorly interlocked, heavily broken with mixture of angular and rounded rock pieces. Taking into account the calculations of BI for every possible structural appearance of the rock mass, we conclude that the wider the spacing of discontinuities is, the bigger the blast ability index is. Also, the blastability index is lower in horizontal formations than in gradient formations. Finally, BI is higher where the excavation drives with dip direction than where it drives against it.
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Chatziangelou, M. Thomopoulos, Ach., Christaras, B. 2010. Excavation data and failure investigation along tunnel of Symbol Mountain, Bulletin of the Geological Society of Greece 2010
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M. Chatziangelou & B. Christaras
5.
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10. Singh P., Sinha Am.2012. Rock Fragmentation by blasting. Taylor & Francis, CRC Press. 872p 11. Zhang Wei, Zhang Dong Sheng, Peng Shao. 2011. New Technology of Efficient Blasting Rock for Large Section Rock Roadway Drivage in Deep Shaft with Complicated Conditions. Applied Mechanics and Materials, Vol. 94-96, pp1766-1770.