ON THE PARAMETERS AND NUMBER OF DRILLING MACHINES FOR INSTALLATION ON DRILLING JUMBOS

O. D. Alimov, P. A. Samoilov

Recently, in the technical literature [1–4] devoted to the technique of driving horizontal development workings in rocks of medium and high strength, many researchers and production workers have expressed the need to create, in the near future, drilling jumbos more advanced than those currently in existence. To reduce the time spent drilling the face and to increase labor productivity, such jumbos must be equipped with powerful drilling machines mounted on supporting-and-feeding devices (manipulators and automatic feeders) with mechanized drives. These propositions are shared by all authors who speak in favor of drilling jumbos.

As for the specific questions of the type and required power of drilling machines and of the appropriate number of them on one drilling jumbo, no answer is given in the literature known to us. It is true that the literature contains a number of proposals concerning the number of drilling machines on a drilling jumbo, but they are presented without sufficient justification. In confirmation of this, we shall merely note that, for the same conditions, various researchers recommend constructing drilling jumbos with a number of drilling machines ranging from 1 to 20.

This article presents some results of the authors’ investigations on this question as applied to the driving of haulage workings under the mining-engineering conditions of the Gornaya Shoriya mines.

Type and principal characteristics of drilling machines for drilling jumbos

At the mines of Gornaya Shoriya, most haulage workings are single-track, with a cross section of 6.5–9 m²; they are driven through rocks with a strength coefficient \(f = 9 \div 14\) on the scale

Prof. M. M. Protodyakonov. In a number of cases, rocks with a hardness of 16–18 are encountered. Two-track workings with a cross section of \(12\text{–}14\ m^2\) are driven less often.

Blast-holes are usually drilled to a depth of \(1.8\text{–}2.2\ m\). Greater depths are not practiced, since with the mechanization of blast-hole drilling existing at these mines, more than a shift must be spent on drilling off the face, which complicates the organization of heading operations.

For drilling blast-holes in these rocks it is possible to use percussive-rotary machines (pneumatic drilling hammers) and rotary-percussive machines. The latter, in the form of experimental models, appeared in foreign practice comparatively recently and have not yet been adopted by the industry of the USSR. Therefore, in creating drilling jumbos in the near future, we consider it expedient to install on them pneumatic machines of percussive-rotary action, which have proved themselves well in practice. The question of the advisability of using drilling jumbos with rotary-percussive machines can be decided only after a comprehensive study of this drilling method.

One of the main indicators of the efficient operation of a drilling machine and its mounting-and-feed device is the minimum expenditure of time for drilling off the face.

The duration of drilling each blast-hole in the face, which depends, as is known, on the depth of the blast-hole, the machine drilling speed, and the time spent on auxiliary and preparatory-final operations, may be written as

\[ t = t_1 + t_2 + \frac{T_{\mathrm{p.z}}}{n_{\mathrm{sh}}}\ \text{min.}, \tag{1} \]

where

\[ t_1=\frac{l_{\mathrm{sh}}}{v} \]

is the machine drilling time for one blast-hole, min.;

\(l_{\mathrm{sh}}\) — blast-hole depth, \(m\);

\(v\) — machine drilling speed, \(m/\text{min}\);

\(t_2\) — time for auxiliary operations, referred to one blast-hole, min.;

\(T_{\mathrm{p.z}}\) — time expenditures for preparatory-final operations, min.;

\(n_{\mathrm{sh}}\) — number of blast-holes in the set drilled by one machine.

The time expenditures for drilling one blast-hole 2 and \(3\ m\) deep as a function of the machine drilling speed, calculated by formula (1), are given in Fig. 1. The calculations were carried out for two different values of the time spent on auxiliary and preparatory-final operations, referred to one blast-hole,

\[ t_3 = t_2 + \frac{T_{\mathrm{p.z}}}{n_{\mathrm{sh}}}, \]

namely: \(t_3 = 7.0\) min. and \(t_3 = 4.0\) min. Moreover, the first value of the total expenditures was obtained on the basis of chronometric observations of the operation of BT-3 drilling jumbos.

at the mines of Gornaya Shoriya [1], while the second was adopted provisionally, taking into account the possibility of reducing the duration of auxiliary operations through the use of long-stroke automatic feeds and more advanced manipulators with electric or hydraulic drives for their lifting and rotation mechanisms.

According to Fig. 1, the time spent on drilling one blasthole decreases as the machine drilling speed increases.

Fig. 1. Dependence of the duration of drilling one blasthole and the power of the drilling machine on drilling speed:
1—duration of drilling at \(t_z = 7\) min.; 2—duration of drilling at \(t_z = 4\) min.

At the same time, the most effective influence of speed on reducing the duration of drilling a blasthole is observed when the drilling speed is increased only up to \(1200\ \mathrm{mm/min}\) for a blasthole depth of \(2\ \mathrm{m}\), and only up to \(1500\ \mathrm{mm/min}\) when drilling blastholes \(3\ \mathrm{m}\) deep. A further increase in drilling speed has no significant effect on the total time required to drill one blasthole.

Drilling a blasthole at one speed or another requires certain expenditures of power [5]. The power expenditures for drilling can be determined from the formula

\[ N=\frac{A_{\mathrm{ob}} v \pi d_{\mathrm{sh}}^{2}}{60\cdot 75\cdot 4\cdot 10} =\frac{A_{\mathrm{ob}} v d_{\mathrm{sh}}^{2}}{57\,320}\ \mathrm{h.p.}, \tag{2} \]

where \(A_{\mathrm{vol}}\) is the volumetric work of destruction, kgm/cm³;
\(v\) is the machine drilling speed, mm/min;
\(d_{\mathrm{h}}\) is the blasthole diameter, cm.

The volumetric work of destruction depends on the strength of the rock, the geometry of the drilling tool, and the method of drilling. According to our investigations [6], the average value of the volumetric work of destruction for rocks characteristic of the mines of Gornaya Shoriya, in percussion-rotary drilling with single-chisel bits of diameter 40–46 mm, is \(A_{\mathrm{vol}} = 16\text{--}22\) kgm/cm³ for rock strength \(f = 9 \div 14\), and \(A_{\mathrm{vol}} = 25\text{--}30\) kgm/cm³ for \(f = 16 \div 18\).

The power values determined from formula (2) for the case of drilling blastholes 40 mm in diameter are plotted in Fig. 1. According to the figure, the required power of the drilling machine increases as the drilling speed increases, and the more intensively, the greater the energy consumption. To achieve blasthole drilling speeds of 1200–1500 mm/min, for example in rocks with \(f = 9 \div 18\) \((A_{\mathrm{vol}} = 16 \div 30\) kgm/cm³), the power of the drilling machine must be 5.5–12 hp.

As is known, the power developed by a percussion-rotary drilling machine is determined by the formula

\[ N = \frac{A n}{75 \cdot 60}\ \text{hp}, \tag{3} \]

where \(A\) is the kinetic energy of the striker piston before impact with the drill, kgm;
\(n\) is the number of blows of the striker piston per minute.

In view of the fact that the power of a drilling hammer is directly proportional to the product \(An\), the justification of drilling speeds that can be provided by drilling machines installed on a drill carriage must begin with determining the possible values of the energy and number of blows of drilling hammers.

Modern pneumatic drilling hammers, when operating with an air pressure of 4–6 atm, develop an impact energy from 3 to 8.0 kgm and a number of blows from 1400 to 3600 per minute.

According to investigations of the mechanism of rock destruction [6–8], when drilling blastholes 40–46 mm in diameter in rocks of medium and high strength, increasing the impact energy from 3.5 to 20–25 kgm does not lead to any substantial increase in the volumetric work of destruction. Therefore, increasing the hammer impact energy from 3.0–8.0 to 20–25 kgm while maintaining the same blow frequency would make it possible to increase the drilling speed by a factor of 3–6. At present, an obstacle to achieving this is the insufficient durability of the drilling tool. The quality of the material and the tool-manufacturing technology used in mines and ore mines apparently will not permit, in the coming years, an increase in the impact energy of drilling mo—

hammers above 7–8.0 kgm. Consequently, an increase in the power of drilling machines of this type can be achieved by increasing the blow frequency. The required blow frequency at various specified powers and values of the energy of a single blow is shown in Fig. 2, where it is evident how much greater the blow frequency of newly designed drilling hammers must be in order to provide powers of 5.5–12 hp.

The results of observations of the process of drill-bit penetration into rock during the operation of modern drilling hammers [8] make it possible to assume that the process of interaction between the bit and the rock will not change qualitatively, and that the magnitude of the volumetric work of breakage will remain constant when the blow frequency of drilling hammers is increased to 6000 per minute (with blow energy above 3.0 kgm and a drill length of 2 m). This number of blows in Fig. 2 is taken as the maximum \((n_{\max})\), which should be aimed at when designing new drilling hammers. It should be noted that modern drilling hammers of the PM-508, KTsM-4 type, produced in series, have a frequency on the order of 1600 blows per minute at a blow energy—

Fig. 2. Dependence of drilling-hammer power on the number and energy of blows.

of 3.5–6 kgm. In recent years, industry has produced hand-held high-frequency hammers with a number of blows of 2600–3600 per minute.

Investigations of the internal processes of high-frequency hammers, carried out at the Department of Mining Machines and Mine Transport of the Tomsk Polytechnic Institute by V. F. Gorbunov [9], showed that the number of blows of high-frequency hammers operating according to a scheme with separate spool-valve distribution (types PR-25, RH-754) can be increased to \(n_{\max}^{1}=4000\) blows/min, and for hammers operating according to the scheme of spoolless hammers (type T-10), to \(n_{\max}^{\prime\prime}=4500\) blows/min. This value of the blow frequency in Fig. 2 bounds the region in which the required power of the hammer can be provided by machines of the simplest design—pneumatic drilling hammers with one working piston.

An increase in frequency above 4000–4500 blows/min while maintaining the working air pressure of 4–6 atm will apparently require a radical change in the design of drilling hammers. One possible direction for accomplishing this is the creation of two-piston drilling hammers, in which blows are delivered to the drilling tool alternately by two freely moving pistons. In recent years such impact units have been developed for rotary-percussive machines, whose blow frequency reaches 6000 per minute. These impact units have not become widespread in practice because of the complexity of manufacture and low reliability in operation. The principal drawback of such machines is the low strength of the impact units, despite the fact that the energy of a single blow does not exceed 3–4 kgm.

On the basis of the foregoing, we believe that, for equipping drilling jumbos that will be developed in the coming years for driving workings in hard rocks, it is necessary to orient toward single-piston drilling hammers, carefully selecting their characteristics and refining the design. At the same time, research and design work should be carried out with the aim of creating reliable impact machines for drilling jumbos with a blow frequency of up to 6000 per minute.

Taking into account the considerations stated above, for work from drilling jumbos one may recommend drilling machines with the following parameters of the impact units: blow energy \(A=5\text{–}8\) kgm and number of blows \(n=4000\text{–}4500\) blows/min.

At these values of energy and blow frequency, the machine power (Fig. 2) will increase to \(N=5.0\text{–}7.0\) hp, as compared with 2.0–2.1 hp for the KTsM-4 hammer.

Table 1 gives the results of calculations of the duration of drilling one blast-hole in rocks \(f=9 \div 18\) when using

zation of drilling machines of the power recommended by us. The calculations were carried out with the aid of the nomogram shown in Fig. 1.

Note. The table has been compiled for drilling holes 40 mm in diameter.

* The drilling speed and duration of drilling a hole by a KTsM-4 drilling hammer are taken as 100%.

From the data presented in the table it is evident that increasing the power of the drilling machine by 2.5—3.3 times makes it possible to increase the drilling speed proportionally and to reduce the total duration of drilling one hole 2 m deep by 1.3—1.5 times. If, in addition, the time expenditure $t_z$ is reduced from 7 to 4 min. by improving the design of feeders and manipulators, the duration of drilling one hole will decrease by 2.1—2.2 times. With an increase in hole depth to 3 m, the effect of the indicated measures will be still greater.

Number of drilling machines on a drilling jumbo

The study of advanced domestic and foreign experience in driving horizontal workings shows that, owing to the low drilling speeds that can be provided by existing percussion-rotary drilling machines, reducing the duration of drilling the face of development workings

the workings is achieved mainly by increasing the number of machines operating simultaneously. With high-speed methods of driving workings, the number of drilling machines installed at one face reaches 10–12 [10]. In this case, each drilling machine accounts for only 0.9–1.5 \(m^2\) of the area of the face being worked. A large number of simultaneously operating machines and of workers servicing them on a small working area creates unfavorable conditions for the drillers’ work and reduces their productivity.

In this connection it may be assumed that the creation of drilling machines providing higher drilling speeds, and a reduction in the time spent on preparatory-final and auxiliary operations, will make it possible to obtain high rates of driving workings with lower labor expenditures.

The total time expenditures for drilling the face may be determined from the formula

\[ T = T_{\text{p.-f.}} + \frac{l'_{\text{sh}} n'_{\text{sh}}}{v_1 m_1}\ \text{min.}, \tag{4} \]

where \(l'_{\text{sh}}\) is the average depth of a blasthole according to the drilling-and-blasting plan for the given face, \(m\);

\(n'_{\text{sh}}\) is the number of blastholes in the face;

\(m_1\) is the number of drilling machines working at the face;

\(v_1\) is the drilling speed in terms of total time expenditures, i.e., taking into account both the time expenditures for drilling the blasthole itself and the time expenditures for auxiliary operations, \(m/min\)

\[ v_1 = \frac{l'_{\text{sh}}}{t_1 + t_2} = \frac{l'_{\text{sh}} v}{l'_{\text{sh}} + t_2 v}. \tag{5} \]

Graphical dependences of the drilling speed in terms of total time expenditures on the magnitude of the machine drilling speed and the time expenditures for auxiliary work for the cases considered by us are given in Fig. 3.

According to Fig. 3, increasing the machine drilling speed above 1000–1250 \(mm/min\), with substantial time expenditures on auxiliary work (\(t_2 = 5\) min.) and a blasthole depth of 2 \(m\), does not lead to a substantial increase in the drilling speed in terms of total time expenditures and therefore is hardly advisable. At the same time, with smaller auxiliary expenditures (\(t_2 = 2.5\) min.) and a blasthole depth of 3 \(m\), the drilling speed in terms of total time expenditures increases substantially when the machine speed is raised to 2000 \(mm/min\) and more. If our recommendations for creating drilling hammers with a power of 5.0–7.0 hp (see table) are implemented, and the time expenditures for auxiliary work are reduced to \(t_2 = 2.5\) min., it is possible to ensure a drilling speed in terms of total time expenditures of

total time expenditures to 540 mm/min for rocks with \(f = 16 \div 18\) and to 680 mm/min for \(f = 9 \div 14\).

The results of calculations of the total duration of drilling blastholes in the face of a single-track working, performed by formula (4), for \(l'_{\text{sh}} = 3\) m, \(n'_{\text{sh}} = 30\) blastholes, and \(T_{\text{p.z}} = 50\) min, are given in Fig. 4.

It is evident from Fig. 4 that the total time expenditures for drilling blastholes in the face are substantially reduced only when increasing

Fig. 3. Dependence of the drilling rate in terms of total time expenditures on the machine drilling rate:
\(1\)—\(t_2 = 5\) min, \(l'_{\text{sh}} = 2\) m; \(2\)—\(t_2 = 5\) min, \(l'_{\text{sh}} = 3\) m; \(3\)—\(t_2 = 2.5\) min, \(l'_{\text{sh}} = 2\) m; \(4\)—\(t_2 = 2.5\) min, \(l'_{\text{sh}} = 3\) m.

the number of drilling machines to 4–5 and the drilling rate in terms of total time expenditures to 0.5–0.6 m/min. A further increase in the number of drilling machines at \(v_1 = 0.5\text{–}0.6\) m/min cannot appreciably reduce the total time required for drilling the face. Similar results were obtained by us also for \(l'_{\text{sh}} = 2\) and 2.5 m.

It should also be noted that all calculations in constructing the graphical dependences (Fig. 4) were performed on the assumption that the time expenditures for auxiliary and preparatory-final operations would be the same in magnitude, regardless of the number of drilling machines and the drilling rate provided. In reality, however, with an increase in the number of drilling machines installed on one drilling ...

on a jumbo, beyond four, will evidently increase also the time expenditures for preparatory and concluding operations. In addition, to increase the drilling rate it will be necessary to use more powerful and heavier drilling machines, which will lead to an additional increase in the time spent on auxiliary operations and, naturally, will reduce the effect from using a large number of powerful drilling machines.

Taking the foregoing into account, we believe that, in order to ensure minimum time expenditures for drilling out the face of a single-track working, it is inexpedient to increase the number of drilling machines installed on one jumbo beyond four, and the drilling rate in terms of total time expenditures beyond \(0.5\)—\(0.6\) m/min.

Fig. 4. Duration of drilling holes in the face as a function of the drilling rate in terms of total time expenditures and the number of drilling machines.

The efficiency of the work of drillers is characterized not only by the minimum time expenditures for drilling out the face, but also by the maximum possible productivity of their labor. One of the most important ways of increasing the labor productivity of drillers is simultaneous work on several drilling machines.

The maximum number of drilling machines that one driller is able to service without downtime can be determined from the formula

\[ m_{\max}=\frac{t_1+t_2}{t_2}. \tag{6} \]

The worker’s productivity can be expressed by the number of linear meters drilled in one hour by all the machines that he services, and is calculated by the formula

\[ L=60v_1 m \ \text{linear m/hour}, \tag{7} \]

where \(v_1\) is the drilling speed in terms of total time expenditure, m/min.

Substituting the values of \(m_{\max}\) and \(v_1\) into formula (7), we obtain an expression for determining the maximum possible hourly productivity of a driller

\[ L_{\max}=60\frac{l'_{\mathrm{sh}}}{t_2}\ \text{linear m/hour}. \tag{8} \]

The results of calculations by formulas (7) and (8) are given in Fig. 5, according to which, when drilling the face to a blasthole depth of 2 m with the drilling jumbos of the TB-3, BK-2, etc. types most widely used at present (when using them, the time expenditure for auxiliary operations \(t_2\) is at least 5 min), it is possible to ensure a driller’s labor productivity of no more than 24 linear m/hour. An increase in drillers’ labor productivity by a factor of 2–3 can be achieved by reducing the time expenditure for auxiliary operations, for example, to 2.5 min, by mounting the drilling machines on more advanced drilling jumbos equipped with long-travel feeds and manipulators with hydraulic or electric drive. In this case, when drilling blastholes 2 m deep, the maximum productivity of a driller is \(L_{\max}=48\) linear m/hour, and with a blasthole depth of 3 m, \(L_{\max}=72\) linear m/hour.

When working with KTsM-4 drilling hammers from existing drilling jumbos (\(N=2\text{–}2.2\) hp, \(v=240\text{–}450\) mm/min, and \(t_2=5\) min), as well as with machines having the parameters recommended by us but mounted on more advanced drilling jumbos (\(N=5\text{–}7\) hp, \(v=600\text{–}1550\) mm/min, and \(t_2=2.5\) min), it is advisable for one driller to service 2–3 machines. A larger number of drilling machines per worker does not increase labor productivity. For the same reason, it is irrational to increase the machine drilling speeds above 800 and 1250 mm/min at blasthole depths of 2 and 3 m, respectively.

From all that has been set forth above, it may be concluded that, for driving single-track haulage workings with a cross section of 6.5—

9 m² in strong rocks, it is advisable to create drilling jumbos for 3–4 powerful drilling machines. In doing so, special attention should be paid to improving their positioning-and-feeding devices (manipulators and automatic feeders). In order to increase labor productivity, drilling jumbos

Figure labels visible in the diagram:
Vertical axis: productivity of one driller, linear m/hour.
Horizontal axis: machine drilling speed, mm/min.
In the fields: 1 hammer; 2 hammers; 3 hammers; 4 hammers; 5 hammers.
Top diagram: \(L_{\max}=24\) linear m; \(l_{\mathrm{sh}}=2\) m; \(t_2=5\) min.
Middle diagram: \(L_{\max}=48\) linear m; \(l_{\mathrm{sh}}=2\) m; \(t_2=2.5\) min.
Bottom diagram: \(L_{\max}=72\) linear m; \(l_{\mathrm{sh}}=3\) m; \(t_2=2.5\) min.

Fig. 5. Productivity of one driller as a function of the number of machines serviced and of their operating regimes.

for three drilling machines must be serviced by one driller, and for four machines—by two drillers.

When driving double-track workings (with a cross section of 12–14 m²), it is advisable to use simultaneously two jumbos with three or four drilling machines each.

Thus, the creation of new, more advanced drilling jumbos for 3–4 powerful drilling machines will make it possible to achieve

a substantial increase in the labor productivity of drillers, reduce the time required for each cycle of drilling-and-blasting operations, and thereby achieve high rates of advance of workings. Thus, for example, if the process of drilling blastholes in single-track workings, presently carried out at the mines of Gornaya Shoria in rocks with strength \(f = 16 \div 18\) using BT-3-type jumbos, takes 3.6–4.5 hours, then with the creation of more advanced drilling jumbos the duration of this same process can be reduced to 1.4–1.6 hours, i.e., by more than half. An even greater effect from the use of such drilling jumbos can be achieved by increasing the depth of the blastholes to 2.5–3.0 m.

The creation of advanced drilling jumbos will also help to solve more fully the problems of automating a number of operations during drilling, reducing noise and the effect of vibration on the worker, reducing air dustiness at the face, etc., which will make it possible to significantly ease the labor of drillers. However, to date, research and design organizations, as well as mining-machinery plants, have not paid due attention to the problem of creating advanced drilling jumbos, which is significantly hampering the increase in workers’ labor productivity in driving mine workings and is delaying the construction and reconstruction of mining enterprises.

REFERENCES

1. O. D. Alimov, P. A. Samoilov. On the advisability of using drilling carriages at the mines of Gornaya Shoria. Mining Journal, No. 8, 1958.

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4. P. Ya. Taranov. Drilling-and-blasting operations. Ugletekhizdat, 1958.

5. O. D. Alimov. On assessing the quality of machines for drilling blastholes. Article in the present collection.

6. O. D. Alimov, A. A. Alimova. Nomograms for calculating certain parameters of drilling hammers. Article in the present collection.

7. I. A. Ostroushko. Destruction of rocks during drilling. Gostoptekhizdat, 1952.

8. O. D. Alimov. On the mechanism of rock destruction in percussive-rotary drilling. Proceedings of TPI, vol. 75, 1954.

9. V. F. Gorbunov. Experimental study of the working process of pneumatic drilling hammers. Candidate dissertation, Tomsk, TPI, 1958.

10. MUP USSR. High-speed driving of a crosscut at a rate of 870.5 m per month at a Czech mine. Moscow, TsITI, 1955.