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M E C H A N I Z A T I O N AND A U T O M A T I O N
M E T H O D S OF R O T A R Y BOREHOLE D R I L L I N G
(UDC 622.235.1) (UDC 622.233.6)
O. D. A t i m o v a n d L. T . D v o r n i k o v
Mining Institute Academy of Sciences, Siberian Branch, Novosibirsk; Polytechnic Institiute, Tomsk Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Polcznykh Iskopaemykh, No. 3, pp. 91-96, May-June, 1965 Original article submitted October 14, 1964
The graph of rotary borehole drilling rate versus feed pressure has four sections (Fig. 1): I) abrasion of the rock; II) transitional; III) bulk disintegration; IV) a zone where the rise of drilling rate fails off. The greatest ef- fect is achieved in section HI, where the pressure shears off large rock fragments. In this section the rock is crushed with least expenditure of energy.
The slope a of the linear part of section III on the V = F (Pf) curve varies with the rock strength. In most cases this section obeys the equation
v = k (pz=po) ,
where k is some coefficient of proportionality depending on tan c~, and P0 is the min imum feed pressure at which bulk fragmentation of the face begins.
After analyzing numerous experimental results by many workers, the present authors have come to the con- clusion that for optimum drill rotation rates k is constant for each rock, while P0 can be fairly accurately represented by the equation P0 = 35f , where f is the rock hardness coefficient on the Protod'yakonov scale.
Table 1 is a collection of data by many experimenters on the drilling conditions for various rocks at the most efficient bit rotation rates. From these data, k is plotted versus the hardness coefficients of the rocks (Fig. 2).
As k characterizes the effect of rotary drilling in various rocks, it can be called the coefficient of drilling
eff iciency.
%
2
\
\ / "4
I _ ] I I
A /oB
t /
pa A,/
I I I IV
Pf, kg
Fig. 1. Drilling rate V(1) and energy consumption of fragmentation Aro t (2), plotted versus feed pressure. 1) Aro t =F (Pf); 2) V=F (Pf).
Statistical processing of the data in Table 1 (plus other data) gives the following equation for k versus f :
for :f = 2-6
for ~ =6-16
k-- x0-1.3~;
k = 3 .1-0 .19~ .
These relations are valid for a 42 mm diameter drill bit (i.e., stand- ard RP type), and for feed pressures in a certain range (section III in Fig. 1).
The feed pressure range is l imited by one of the following factors: the bit geometry; the bit steadiness; or the rate at which the fragments are cleared from the bit.
Owing to their geometry, the maximum advance of standard bits can- not exceed 6 mm per revolution. Thus, for the rotation rates most widely used in practice,100-400 rev/min, the maximum drilling rate is 600-2400 mm/rnin . At high drilling rates the face begins to come into contact with the rear edge of the drill (point A in Fig. 1) and the linear relation between V and Pf ceases to hold (section IV).
250
TABLE1
Rock and hardness coeff ic ient
Coal, f = 2--3
Fine-gra ined sandstone, f = 4 - 5
Siltstone, f = 5
Soft sandstone, f = 6
Marble, f = 6
Limestone, ~ = 6
Sandstone, f = 6 - 8
Medium-gra ined sandstone, f = 8
Limestone, ~e = i0
Dolomit ized l imestone, ~= 12
Coarse-gra ined quartz sandstone, I-- 1 4 - 1 7
Optimum rotat ion rate. r e v / m i n
800
425
450
270
525
400
400
270
345
345
200
Feed pressure, kg
50 75
115
300 430 650
290 425
250 320 380
I00 150 180
400 600 800
250 380 760
550 750
II00
250 420
600 750
200 385 375
500 850
1100
Dril l ing rate, mm/min
375 500 820
970 1350 2220
1020 1450
300 430 640
160 270 360
400
720
1180
250 500
1140
400 700
1330
150 330 650 725
50 200 360
61 112 149
kay
7.00
Author and source
P. N. Iyudin [9]
3.70 A . N . Volkov [5]
3.45 A . N . Volkov [5]
2.00 A . D . Imas [8]
2.00 O. D. Alimov, N, S. Kolodyazhnyi,
and V. N. Karminskii [I0]
1.90 G.N. Pokrovskii [2]
1.66 N. S, Kolodyazhnyi and L. T. Dvorni-
kov [11]
1.56 A . N . Volkov [5]
1.17 I . E . Rudavskii [3]
0.71 I . E . Rudavskii [3]
M. K. Tsekhin [6]
The max imum pressure which a bit can sustain without breaking is 1200-1500 kg. For weaker rocks this l imi t is lower, as the dynamic load on the cutt ing edge i sg r e a t e r . The most suitable feed pressures are as follows: for rocks with f > 10, 1200-1500 kg, for f = 8-10, 800-1000 kg, for f = 6-7. up to 750-800 kg, and for ] = 4 -5 , up to 400-500 kg.
Clear ing fragments from the hole can also affect the upper l imi t of the l inear i ty of V = F (Pf). If c lear ing is inadequate, section IV m a y begin at r e l a t ive ly low feed pressures.
The graph of dri l l ing ra te venous bit rotat ion rate has a m a x i m u m . This phenomenon has been recorded by many investigators and has led to the concept of "op t imum bit rotat ion rate ." At the opt imum bit rotat ion rate the dr i l l ing ef f ic iency is greatest and the power consumption least; it is thus very important to discover nop t.
251
K
6
5
3
2
4
0
1 fSO0 ~z~O0
f200
"~ r
800
c~ d ~ 600
zoo
\ 200
8 ~2 f 0 4 8 ~2 f
Fig, 2 Fig. 3. Optimum bit rotation versus
rock hardness coefficient.
Table 2 gives recommendations from many investigators on the optimal bit rotation rates in various rocks. From these data. Fig. 3 plots the zone of good n values versus f . To a first approximation this graph can be repre-
sented by the formula C
nopt ~-- 7 - " (2)
where C is a constant coefficient with mean value 2200 r e v / i n i n . In Fig. 3 the curve nop t = 2200 / f is given by
the dashed line.
TABLE 2
Rock and source
Clay shales [8] . . . . . . . . . . . . . . . . Shales and soft sandstones [3] . . . . . . . Schistose sandstone [2] . . . . . . . . . . .
Coefficient of hardness
2--3
2 4--5
Recommended rotation rate,
r e v / m i n
600--1000 up to 1500
600
Coefficient from formula (2).
r e , / m i n
1800--2000
3000
1400--3000
Sandstone [5] . . . . . . . . . . . . . . . . . Nemark bauxite [7] . . . . . . . . . . . . .
Siltstone [12] . . . . . . . . . . . . . . . . . J , .
�9 �9 �9 ~ ~ ~ �9 �9 ~ ~ 1 7 6 �9 �9 �9
v ,
�9 �9 �9 �9 . �9 �9 �9 �9 �9 o e i . . �9
, u .
�9 �9 �9 �9 �9 ~ I e �9 ~ �9 �9 �9 , . �9
4
4--5
5
6
6--8
8 --I0
425
700 450
385
300 200
1700
2800--3500
2250
2300
1800--2400
1600--2000
e �9 . o . . e o . . ~ �9 . , �9 ~
Sand-c lay shale [6] . . . . . . . . . . . .
F ine-gra ined sandstone [6] . . . . . . . . Limestone [7] . . . . . . . . . . . . . . . . Fine-grained quartz sandstone [6] . . . . Granite [ 1 3 ] . . . . . . . . . . . . . . . . .
Medium-hard rocks [4] . . . . . . . . . . .
Granite [14] . . . . . . . . . . . . . . . . . Porphyroid, diabase [14] . . . . . . . . . .
Polymetal l ic ore [14] . . . . . . . . . . . .
I0--12
6
8
8--I0
12
I0--12
6--I0
15
12
6--8
116
300-400
300
345
125
100-300
150-400
50--70
125
210-286
1160-1400
1800-4002
2400
2700--3450
1500
1200-3000
1500-2400
750-1500
1500
1700
252
TABLE 3
Rock and source
Coal [15] . . . . . . . . . . . . . . . . . . . .
Gypsum [16] . . . . . . . . . . . . . . . . . .
Rock salt [16] . . . . . . . . . . . . . . . . .
Carbonaceous a rg i l l i t e [6] . . . . . . . . .
C lay shale [17] . . . . . . . . . . . . . . . .
" " [6] . . . . . . . . . . . . . . . . . n ,~ , ,
. . �9 . . . . . . . . . . . . . �9
Sandy a rg i l l i t e [6] . . . . . . . . . . . . . .
S iltstones [ 5] . . . . . . . . . . . . . . . . . .
F ine-gra ined sandstone [ 5] . . . . . . . . .
Limestone [9] . . . . . . . . . . . . . . . . .
Argillaceous sandstone [6] . . . . . . . . . Sandstone [4] . . . . . . . . . . . . . . . . . Syenite [18] . . . . . . . . . . . . . . . . . .
Sandstone [2] . . . . . . . . . . . . . . . . . Limestone [2] . . . . . . . . . . . . . . . . . Medium-grained sandstone [5] . . . . . .
Limestone [9] . . . . . . . . . . . . . . . . . Sandy-c lay shale [6] . . . . . . . . . . . . .
Limestone [3] . . . . . . . . . . . . . . . . . Medium-grained sandstone [6] . . . . . .
Coarse-grained sandstone [20] . . . . . .
F ine-gra ined quartz sandstone [6] . . . . Diorite [4] . . . . . . . . . . . . . . . . . . .
Granite [2] . . . . . . . . . . . . . . . . . . . Hard coarse-grained quartz sandstone[6]
Coefficient of hardness
up t o 2 1 . 8 - 2 . 2 2.6 - 3 . 4
2.5
3 - 4 4.4 4 5 5
4 - 6
5 - 6 6
6--8 6_8 ~
4 - 5 6 8
8 8
10
10.7 8 - 1 4
12.3 1 4 - 1 6
1 2 - 1 4
17
Rational dril l ing conditions
rptation rate, r e v / m i n
kW 800-1000
i000--1200
300
69O
300
1220 4OO 45O 425 917
3OO 400 45O
580 580 425
1220 2O0
45O 2O0
274
125 152
110 125
Specific feed pressure,
kg
55 250
2OO
5OO 6O
500 63
5OO 1000
6OO 2O
5OO 1000
66O
8OO 8OO
II00
63
800
6OO
85O
83O
i000
1500
8OO 1100
drill ing
rate, r e v / mi n
107
power ex- penditure, force,
i.3
3.6
up to i0
2.7
1.74
2.7
3.0
2.65
3.5
4.0
1.4
2.7
4.8
5.15
4.0
3.5
6.0
2.7
2.8
2.77
2.9
2.7
1.240
1.038
2.38
power con- sumption, k g / c m s
5.45
8.0
6.5
9.2
17.4
12.6
14.3
10.2
8
9
I0
12.6
8.3
30.5
9.23
13.2
12.1
51.5
30.0
18.7
27.5
26
48.5
55
36.7
5O
Many investigators [1, 5, 6] have noted that the work required to crush unk volume by rotary dril l ing under "rat ionar ' (efficient) conditions is related to the compression of strength of the rock, or the hardness coefficient f,
by the l inear law
Arev_~ ~ . f (3)
Table 3 gives the recommended rat ional drilling conditions for rocks from f = 1.8 to f = 17. In all cases we de- termined the work per unit volume by starting from the power expenditure and the volume of drilled fragments. The results are shown graphically in Fig. 4. The scatter of the points is main ly due to errors in the data on the dril l ing conditions, which may reach 20-25% [2]. To a fair approximation we can take 5 in (3) as constant and equal to 2.8 kg" m / c m 8. The r.m.s, error is 5 + 0.3 kg. m / c m s.
From the known power consumption of the crushing process we can determine the machine power N necessary for drill ing at a given rate. An e lementary transformation of the known formulae gives
N=AVr. (4)
where A is a constant coefficient equal to the work per unit volume to crush unit hole length in rock with ~ = 1.
watt �9 m i n For standard bits of types RP-2 and RP-7, A = 0.64 , and by (1) the power is
cm
N----O,64kf (p]-- Po).
253
6 0 - -
50
K.
0
Fig. 4.
7 r"
v / | /
m
. J /
2 4 6 8 tO 12 14 16 18 f .
Work required to crush unit volume plotted versus hardness coefficient of rock.
By finding the relations between the principal parame- ters of rotary borehole drilling we can determine the capabil- ities of existing drills and find out how to increase their e f - ficiencies.
L I T E R A T U R E C I T E D
1. L .A. Shreiner, Physical Principles of Rock Mechanics [in Russian], Moscow, Oostoptekhizdat (1950).
2. G . N . Pokrovskii, Principal laws for rotary borehole drilling with constant feed pressure [in Russian], Tr. ZSFAN SSSR, No. 19 (1957),
3. I .E . Rudavskii, Some results on borehole drilling with an electrical rotary drill [in Russian], Izv. Vuzov,Gornyi zhurnal, No. 4 (1959).
4. O .D . Alimov, Investigation of the processes involved in the fragmentation of rocks during borehole drilling [in Russian]. Izd. Tomskogo un-ta (1960).
5. A. N, Volkov, Investigation on the construction of high-efficiency electric rock drills. In symposium, Research on the Mechanization of Mining and Automatics [in Russian], No. 6, Moscow, Gosgortekhizdat (1958).
6. M.K. Tsekhin, On the establishment of optimum regimes for electrical borehole drilling in rocks of the Prokop'evsk deposit [in Russian], Izv. Tomskogo politekhn, in-ta, 93 (1958).
7. V .F . Zimin, V. F. Borovkov, and E. I. Soldatov, Rotary drilling of rocks in bauxite mines [in Russian], Gornyi zhurnal, No. 8 (1962).
8. A . D . Imas, Work on the introduction of rational technological methods for crushing coal and rock by mining machinery. In symposium, Crushing of Coal and Rock [in Russian], Moscow, Ugletekhizdat (1957).
9. P .N . Iyudin, Use of Electric Drills for Drilling Shotholes in Rocks [in Russian], Moscow, Ugletekhizdat (1957). 10. O .D . Alimov, N. S. Kolodyazhnyi, and V. N. Karminskii, Construction of long-travel electric drills with
mechanical feeds [in Russian], Izv. vuzov, Gornyi zhurnal, No. 2 (1963). 11. N .S . Kolodyazhnyi and L. T. Dvornikov, Results of laboratory tests of the ~DP-20 long-travel electric drill
[in Russian], Izv. TPI, 123, Kiev (1963). 12. V .K . Buchnev, Drilling and Shotfiring [in Russian], Moscow, Ugletekhizdat (1951). 13. G . P . Vereskunov, Investigation of conditions for Rotary Borehole Drilling in Hard Rocks [in Russian], Avtoref.
diss., Dnepropetrovsk (1955). 14. V .G . Mikhailov, Borehole Drilling [in Russian], Moscow, Metallurgizdat (1947). 15. V.L . Azarkh, A. D. Imas, and O. P. Shumovskii, Fixing the Conditions for Drilling with Electric Hand Drills
[in Russian], Moscow, Ugletekhizdat (1952). 16. M.O. Krapivin, On the parameters of self-propelled drilling sets for borehole sinking in the underground ex-
traction of rock salt and gypsum. Letter of information on a conference on rock crushing, May 20-22, 1958 [in Russian], Izd. IGD im. A. A. Skochinskogo, Moscow (1959).
1% F .M. Gel'fand and L. D. Markman, Investigation of the Absolute Speed of Drilling Boreholes by the Electrical Rotary Method [in Russian],Nauch. tr. KNIUI CoIL 3, Moscow, Ugletekhizdat (1958).
18. I . F . Medvedev, M. N. Smolyaninov, and V. I. Tyurin, The ~SGP-4 electric drill with hydraulic feed. In symposium, New Equipment for Borehole Drilling, Moscow, Ugletekhizdat (1960).
19. V . T . Sai, Experimental adoption of rotary borehole drilling with flushing, in the Kuzbass [in Russian], Novokuznetsk (1958).
20. A . D . Imas and V. L. Azarkh, Fixing the Conditions for Rock Drilling [in Russian], Moscow, Ugletekhizdat (1952).
254