347 1. Introduction The rock disintegration process, which a wide

347 1. Introduction The rock disintegration process, which a wide

Archives of Mining Sciences 51, Issue 3 (2006) 347–354
347
JAROSLAV VASEK*, PETR MARTINEC*, JAN PINKA**
LABORATORY CUTTABILITY AND ABRASIVENESS TESTS FOR PREDICTION OF WORCABLE
ROCKS IN TUNNEL AND MINING PRAXIS
LABORATORYJNE BADANIA SKRAWALNOŚCI I ŚCIERALNOŚCI DLA PROGNOZOWANIA SKAŁ
ŁATWO URABIALNYCH W PRAKTYCE GÓRNICZEJ I PRZY BUDOWIE TUNELI
Unified methodology for determination of so called decisive properties of rocks definition when cutting tools on cutting heads of tunnelling machines are to be used. Laboratory methods, way of measuring
and assessment of rock cutability, abrasiveness, abrasion resistance of rock are presented. Abrasiveness
according to Czech Industrial Standard ON 44112111 and CERCHARE graphical comparison. Area of
workable rocks definition.
Keywords: rock properties, tunnelling machines
Należy zastosować zunifikowaną metodę określenia decydujących właściwości skał przed zastosowaniem odpowiednich głowic urabiających w narzędziach skrawających w urządzeniach do drążenia tuneli.
Przedstawiono metody laboratoryjne pozwalające na pomiar i ocenę urabialności skał, ścieralności oraz
ich wytrzymałości na ścierania. Ścieralność określana jest zgodnie z normą przemysłową obowiązującą
w Czechach ON 44112111 oraz CECHARE. Określono definicję urabialnych skał.
Słowa kluczowe: właściwości skał, maszyny do drążenia tuneli
1. Introduction
The rock disintegration process, which a wide range of civil engineering activities
in the earth’s crust starts with, both on the surface and underground (construction of
railway and road bridges, urban subways, utility tunnels of all kinds, underground sto*
INSTITUTE OF GEONICS OF THE ACADEMY OF SCIENCES OF THE CZECH REPUBLIC, STUDENTSKA 1768, 708 00
OSTRAVA-PORUBA ([email protected], [email protected])
** UNIVERSITY IN KOSICE, MINING FACULTY, DEPARTMENT OF PETROLEUM ENGINEERING, SLOVAK REPUBLIC,
PARK KOMENSKEHO 19, 042 00 KOSICE ([email protected])
348
rage, generating plants, water and sewage treatment plants, but also repositories for
nuclear waste) is likely to be very useful even in the future, in surface and underground
construction in rock masses of other planets of our solar system and the universe. Cutting tools and cutting systems with such a long history and favourable perspective can
therefore play their role even in the distant future. Work tasks focused on the further
broadening of knowledge of the ROCK-CUTTER interactive system and the continued
increasing of its efficiency with the assistance of high-energy water jet “Vasek (1977,
1992, 1996, 2000, 2005), Fowell et al. (1991, 1993, 1997)”, and new physical principles
of material disintegration “Galjaje-Polujanskij (1972)” are issues worthy of continuing
human efforts.
2. Determination of workability of rocks
2.1. Measurement and assessment of rock cutability
Cutability of rock is defined as a technological property of rock expressing magnitude
of external forces necessary for the rock cutting. It is based on assessment of a mean
value of cutting resistance f Fz (integration of the cutting resistance curve), arithmetic
mean of minimum values of cutting resistances Fzmin (10 values), arithmetic mean of
maximum values of cutting resistances Fzmax (10 values), and various importance their
weights. The highest weight-related importance is assigned to maximum cutting resistances, which significantly contribute to reduction of longevity of cutting tools and their
destruction. As an example, we have a presentation of a graphical record of the course
of cutting resistances measured in the case of a cut depth of 15 mm, on a rock block
sample taken from the exploratory gallery MO 9515 BLANKA, chainage 6995 (Fig. 1).
The cutability calculation uses relevant values of minimum, maximum and mean values
of cutting forces. Because 10 minimum values are zero or are found under the zero value, than f Fzmin = 0.0 kN. The mean value, obtained by integration of the force curve,
f Fz = 0.79 kN. Average value of maximum forces f Fzmax = 2.2 kN. Relevant cutability
at a given depth of bite of 15 mm R15 = 12.4 kN.m–1. Cutability R is then determined by
the arithmetic mean of results achieved at measurements with several depths of cut.
Measurement of workability is carried out in compliance with a methodological procedure (ON 441120 “Industrial Standard 1982) [8], on oriented blocks of rock trimmed
to rectangular shapes (length 300 mm, height and width 200 mm), fixed between jaws
of a laboratory pressure plough (Fig. 1).
The laboratory pressure plough is equipped with a three-component dynamic piezoelectric transducer with a range Fz 0-30 kN, Fy, Fx 0-20 kN. The pressure plough is
equipped for the measurement of higher-cutting resistances with a force transducer of
a range Fz (0-50 kN), built into the hydraulic circuit. The PC uses a multiple-function
A/D card Advantech PCL-816 (16 bit, 16 channel, max. reading frequency 100 kHz)
349
8
9
7
6
5
1
2
4
3
Fig. 1. Laboratory testing plough of the Institute of Geonics of the Academy of Sciences
of the Czech Republic, Ostrava.
1 – testing rock block, 2 – testing cutting tool, 3 – hydraulic press (3000 kN), 4 – hydraulic system
for the cutting tool shifting, 5 – path transducer, 6 – piezoelectric transducer of pressure in hydraulic
system, 7 – carriage, 8 – control panel, 9 – television camera for communication with the computer unit.
Rys. 1. Laboratoryjne urządzenie do badań stosowane w Instytucie Geoniki
Czeskiej Akademii Nauk w Ostrawie.
1 – blok skalny, 2 – testowane narzędzie, 3 – prasa hydrauliczna [3000 kN), 4 – układ hydrauliczny
do przesuwania narzędzia skrawającego, 5 – przetwornik toru, 6 – piezoelektryczny przetwornik
ciśnienia w układzie hydraulicznym, 7 – wózek (przenośnik), 8 – tablica kontrolna,
9 – kamera telewizyjna współpracująca z komputerem
for data acquisition from transducers. Communication between the laboratory pressure
plough operator and the computer unit is secured via a video-camera. Passive resistances
of the mechanical system are deducted in the case of the cutting resistance measurements
carried out by means of the transducer built into the hydraulic circuit. A chisel-shaped
test cutting tool with a cutting edge width b = 20 mm and a cutting edge angle α = 43°
is used for measurement and assessment of cutability R.
Measurement and assessment of the influence of the shape of various tools, the
influence of blunting and other parameters of the cutting process are carried out using
points and cutting edges of various shapes.
Cutability R is calculated from measured values of cutting resistances according to
the relationship (1):
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R 3 where
Fz
f Fzi min
f Fzi max
f Fzi
hi
n
—
—
—
—
—
—
n
Fzi min
hi
i 1
n
Fzi
i 1 hi
n
i 1
Fzi max
hi
4n
[kN.m–1]
(1)
cutting resistance [N],
arithmetical mean of minimum values of cutting resistance [N],
arithmetical mean of maximum values of cutting resistance [N],
mean value of cutting resistances [N],
depth of cut [mm],
number of cuts.
In the case of more rock mass quality levels occurring within the excavated crosssection, the overall workability Rc is calculated according to the relationship (2):
m
Rc S R
i 1
i
m
—
—
—
—
[kN.m–1]
(2)
S
i 1
where
Rc
Ri
Si
m
i
i
overall workability of the face cross-section [kN.m–1],
cutability of i-th layer of rock [kN.m–1],
area of i-th layer of rock within the face cross-section [m2],
number of rock layers.
Cutability of rocks (igneous, volcanic and magmatic, metamorphic, sedimentary)
differs each other in the great range of values 30 to 2000 kN.m–1.
2.2. Measuring and assessment of rock abrasiveness
and its abrasion resistance
The abrasiveness of rock is the rock’s capacity to wear down the surface of a cutting
tool in the process of cutting. The principle of the test lies in the determination of the
decrease in the weight of a standardised steel bit (3 mm diameter, 210 HB hardness)
moving across the trimmed surface of a rock body being tested (Fig. 2), under a constant thrust of 100 N, relative to the total length (15 m) of the path of the testing steel
bit. The rock abrasiveness measurement is carried out using a laboratory abrasivenessmeter, in compliance with a methodological procedure “Industrial Standard CSN ON
44 1121 – 1982”. Abrasiveness FV is calculated from the measured values according to
the relationship (3) (Fig. 3).
351
FV GB
L
[mg.m–1]
(3)
where GB is a decrease in the steel bit weight [g], L – total length of the path of the steel
bit around five paths of different radii [m].
2
1
Fig. 2. Abrasiveness-meter. 1 – rock sample, 2 – standardised steel pin.
Rys. 2. Miernik ścieralności. 1 – próbka skalna, 2 – standardowa końcówka stalowa
Abrasiveness Fv [mg . m-1]
14,0
12,0
10,0
8,0
55,8
65,8
36,4
16,2
1,9
Maximal values
of abrasiveness
[mg . m-1]
84
152
689
327
111
Number of tests
(in sum 1363)
Grain sandstone
Fine sandstone
Siltstone
Claystone
6,0
4,0
2,0
0,0
Conglomerate
Petrographic types of sedimentary clastic rocks
Fig. 3. Average values of abrasiveness FV of sedimentary clastic rocks according
to petrographical types of rocks (Ostrava – Karvina coal district)
Rys. 3. Średnie wartości ścieralności FV okruchowych skał osadowych
w zależności od rodzaju skały (Ostrawa – okręg węglowy Karvina)
352
Abrasion resistance of rock AVM is the rock’s capacity to resist the wear with a cutting
tool in the process of interaction. It is calculated according to the equation (4) from a lost
of rock material when abrasiveness according to Industrial Standard CSN ON 441121
– 1982 is measured
AVM GR
L
[mg.m–1]
(4)
where GR is a difference between the mass of sample before and after abrasiveness
tests [g].
The range of values of abrasiveness and abrasion resistance of rocks measured on
1356 samples of sedimentary clastic rocks according to the described methods in relation to petrographic types of rocks are presented graphically.
Abrasiveness according to Industrial Standard CSN ON 44 1121-1982 and CERCHARE procedures is presented for comparison (Fig. 4).
Cerchar abrasiveness [mg . m-1]
6
5
4
3
2
Cerchar = 2,11071 . FV0,33171
1
0
0
2
4
6
8
10
12
14
16
18
Abrasiveness FV [mg . m-1]
Fig. 4. Abrasiveness FV according to Industrial Standard CSN ON 441121versus CERCHARE procedure
Rys. 4. Ścieralność FV zgodnie z normą CSN ON 441121-1982 oraz obliczana
w oparciu o procedurę CERCHARE
3. Definition of the range of worcable rocks
Workability of rock with cutting tools is a function of more variable quantities. The
most important are considered to be: cuttability R, and abrasiveness FV.
The research and measurements have proved that the area of workable rock is also
limited by consumption of cutting picks Sp (1) (Fig. 5).
353
SP (R 200)( FV 2) 1 ln 1, 23 Kk 5410
(1)
where
R — cuttability [kN.m–1],
FV — abrasiveness [mg.m–1],
KK — koeficient of the quality of cutting pick (for pick s TN 20, KK = 1).
The rock can be considered workable with cutting tools without assistance of a water
jet if the cuttability R ≤ 700 kN.m–1, abrasiveness FV ≤ 3 mg.m–1, and consumption of
picks Sp ≤ 0. 3 ks.m–1.
The method of cutting rock assisted by water jets is expected to extend the ranges
of workable rocks R ≤ 900 kN.m–1, abrasiveness FV ≤ 4 mg.m–1, and pick consumption
Sp ≤ 0.5.
If significantly more abrasion-proof materials with a higher strength are developed
for cutting edges of cutting tools, the range of workable rock will be even wider, and
will cover rocks with higher values of workability and abrasiveness. By then, rollers or
explosives have to be used to reach appropriate cutting performance and tool consumption when rocks with higher values of cuttability, abrasiveness are to be broken.
1600
Cuttability R [N . cm -1]
1400
1200
1000
800
2
600
Sp
3
2
1,0
0,8
0,6
400
1
200
0,3
0,1
0
0
1
2
3
Abrasiveness FV [mg . m-1]
4
5
6
Fig. 5. Definition of areas of workable rocks according to cuttability, abrasiveness and pick consumption.
1 – area of rocks workable with cutting picks, 2 – area of rocks workable with high pressure water jet
assistance, 3 – area of workable rocks with rollers.
Rys. 5. Określenie zakresu urabialności skały w oparciu o skrawalność, ścieralność i zużycie narzędzia.
1 – zakres skały urabialnej przy użyciu końcówek skrawających, 2 – zakres skały urabialnej
przy zastosowaniu także wysokociśnieniowych dysz wodnych, 3 – zakres urabialności
przy użyciu innych urządzeń
354
Conclusion
The presented paper documents a laboratory methods of the Institute of Geonics, Ostrava
for measurement and assessment of cuttability and abrasiveness (abrasion resistance) of
rocks as decisive properties of rocks when cutting tools are to be used on roadheaders and
tunnelling machines for rock extraction. Thereby defined properties of rocks are used to
compare workability of different rocks, for prediction of cutting performance and cutting
tool consumption, for area of effectively workable rocks by cutting tools definition. Abrasiveness of rocks defined according to Institute of Geonics, Ostrava and of the CERCHARE
procedures are presented for comparison, too. Application of this method can be suitably
added to the decision-making process when tunnelling machines are to be used. It can
contribute to diminishing the number of events of improperly selected excavation method,
thus to reaching more favourable client’s economic results. As a result of utilisation of this
method, also the database of information needed for the research process to become perfect
extends. It will help in achieving the objectives of both the client and the research base.
This paper was prepared with support of the project grant A 3086201 of the Grant Agency
of the Academy of Sciences of the Czech Republic.
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REVIEW BY: PROF DR HAB. INŻ. KRZYSZTOF KRAUZE, KRAKÓW
Received: 23 March 2006