THE INFLUENCE OF TECHNOLOGY AND WORK ORGANIZATION ON THE RATE OF DRIVING EXPLORATION MINE WORKINGS AT THE ELDORADO DEPOSIT

A. D. Gromov, V. G. Lukyanov

(Presented by the scientific seminar of the Department of Geodesy, Mining, and Construction)

In recent years, within the system of the Ministry of Geology of the USSR, more than 200 thousand m of underground exploration mine workings have been driven annually, and about 10–12% of the total expenditures on geological exploration work have been spent on them.

Of this volume, 8.2% of the workings are driven manually without the use of explosives, 31.8% with mechanized drilling of blastholes and manual removal of rock, and 60% with comprehensive mechanization of the principal driving operations. About 28% of the workings are driven at a rate of 100 m per month or more, with an average rate of 68.7 m/month per crew. In the total volume of underground exploration mine-work driving, 96–98% is accounted for by horizontal workings.

Despite the high level of mechanization of mine-driving operations—blasthole drilling is mechanized by 92% and rock removal by 60%—the cost of driving underground exploration workings has increased by approximately 2–2.5 times in comparison with 1959, mainly because of the low efficiency of equipment use. That is, with the existing mechanization it is necessary to identify reserves for increasing the rate of driving exploration mine workings and reducing their cost. For this purpose, a group of staff members of the Department of Geodesy and Mining carried out work to identify internal reserves for increasing the rate of driving horizontal exploration mine workings at the Eldorado deposit.

Exploration of the Eldorado deposit by mine workings is being conducted by the Northern Expedition of the Krasnoyarsk Geological Administration. The bedrock gold-ore deposit is represented by quartz veins located within a mass of garnet-mica and mica schists. The rock category by drillability is XVI–XVII according to the 1969 Unified Norms and Rates classification. The elevated rock category determined the drill-and-blast method for driving the exploration mine workings. The workings (adits, drifts, crosscuts) are driven for lengths from 20 to 1000 m. Crosscuts 20–30 m long are driven with a cross section of 5.1 m², without support of the excavated space; adits and drifts up to 1000 m long, with a cross section of 6.4 m², are driven with and without support of the excavated space. Blasthole drilling is carried out with PR-24 LU and PR-30 LU high-frequency rock drills mounted on P-18 LA pneumatic supports. Rock loading is carried out by a PPN-1s machine into cars with a capacity of 0.8 m³.

Delivery of loaded mine cars to the dump is carried out by AK-2U storage-battery electric locomotives. Mine-car exchange is performed by means of portable turnouts or dead-end sidings. Detonite 10A is used as the explosive; the method of blasting is by fuse.

The organization of work in driving geological-exploration mine workings was adopted as cyclical. A drifting crew consisting of 8--12 persons performed 1.5--2.5 cycles per day. In the course of work the drifters drilled the face, loaded the rock into mine cars, delivered the train of loaded cars to the dump, extended the ventilation pipes, and laid the rail tracks. Blast-hole drilling was carried out with two or three rock drills. Two drifters were engaged in loading the rock; the third, if the crew consisted of 12 persons, drilled blast holes in another face. The crew loaded 5--7 mine cars, work at the face was stopped, and the drifters delivered the train of loaded cars to the dump, unloaded it, and delivered the train of empty cars back for loading. Three to four trains of mine cars were loaded in one advance.

As required, the crew extended the ventilation-pipe line and laid the rail tracks. With this organization of work, the main technical-and-economic indicators of the crew were as follows:

The time expenditures for carrying out individual operations, determined as a result of time-study observations, are given in Table 1. The cycle consists of the following operations and lasts

\[ T_c = t_b + t_l + t_e + t_{dr} + t_{ch} + t_v + t_{rt} + t_{tr} + t_{ins} = \]

\[ = 160.74 + 57.66 + 60.50 + 168 + 45 + 40 + 48 + 10.25 + 15, \]

\[ T_c = 595 \text{ min}, \]

where:

\(t_b\) -- time for drilling blast holes, min;

\(t_l\) -- time for loading rock, min;

\(t_e\) -- time for exchanging mine cars during loading, min;

\(t_{dr}\) -- time for delivering the train to the dump, unloading it, and delivering the train back, min;

\(t_{ch}\) -- time for charging blast holes and blasting, min;

\(t_v\) -- ventilation time, min;

\(t_{rt}\) -- time for laying rail tracks, min.

\(t_{\text{mov}}\) — time for moving the track crossover, per cycle, min;

\(t_{\text{vent}}\) — time for extending the ventilation pipes, per cycle, min, i.e., in a day, with this organization of work, 2.4 cycles can be performed. In this case the time of unproductive downtime is not taken into account; it amounts to about 30%. Downtime occurs because of the absence of drills, jamming of the drill shank in the perforator, insufficient compressed-air pressure at the face required for simultaneous operation of three perforators, or of a perforator and a rock-loading machine, and the absence of an adequate number of service personnel.

Table 1

Analyzing the data presented above, the following conclusions may be drawn: increasing the rate of driving horizontal exploration mine workings is an achievable task. For this it is necessary:

1. To reduce the time for exchanging cars during rock loading. For this, the distance of the track crossover from the face must be no more than 20–25 m, or transloaders should be used during rock loading.

2. When loading rock with bucket-type machines, no fewer than three drift miners should be employed when the haulage distance for loaded trains is more than 1000 m (two load, one delivers the loaded cars to the dump and brings the empty ones back), since the machine downtime during the exchange and unloading of trains when loading is done by two drift miners amounts to about 28% of the cycle time.

3. Taking into account the low abrasiveness of the rocks, replace intermittent-action PPN-1s machines with continuous-action PNB machines.

4. Reduce the time for charging blastholes through the use of charging devices or by increasing the number of workers doing the charging.

5. Shorten the ventilation time.

6. Reduce downtime.

To determine by how much the time for carrying out individual operations of the cycle would be reduced, the following was done: one of the employees was included in the crew and assisted the drift miners in loading the rock and exchanging cars. The haulage distance was reduced to 20 m. As a result, the time for exchanging cars was reduced to 25 minutes per cycle; the time for loading the rock remained the same, the use-

the downtime of the rock-loading machine during delivery of the train to the dump was eliminated; the time for exchanging trains at the closed permanent passing loop was added—10 minutes per cycle. The cycle execution time in this case was:

\[ T'_{\mathrm{ts}}=t_b+t_p+t_v+t_{dr}+t_{zv}+t_{pr}+t_{put}+t_{per}+t_{ven}= \]

\[ =160,74+57,66+25+10+45+40+48+10,5+5=401,8\ \text{min}. \]

From this it may be concluded that increasing the number of miners to three reduces the cycle execution time by

\[ T''=T_{\mathrm{ts}}-T'_{\mathrm{ts}}=9,92\ \text{hours}-6,97\ \text{hours}=2,22\ \text{hours}. \]

In one day it is possible to complete 3 cycles with a seven-hour work shift and to increase the rate of drifting from 90 m per month, with 2.4 cycles completed per day and an advance of the face per cycle equal to 1.25 m, to 110 or more meters when 3 cycles are completed per day.

Thus, there is a real possibility of increasing drifting rates to 150–200 m per month if the above-mentioned shortcomings are eliminated.