The Ophelia Tunnel in the Cripple Creek District of Colorado was driven for the purpose of draining mines, and transporting ore and waste from the deep levels of such properties as it might cut. The methods employed in advancing this tunnel are by no means unknown to many people interested in this form of operation; nevertheless they may prove of interest to those unacquainted with the methods adopted in this instance, and also, perhaps, to those to whom this is a twice or often-told tale.

Lower Gold Hill, Ophelia Tunnel in foreground

This tunnel has been driven to a point approximately 8,500 feet in a direct line from its portal. It is for its entire length nine feet by nine feet in the clear, and in places will show ten feet by twelve feet.

The tunnel was driven through granite, then into breccia, with intervening dykes of phonolite, andesite, and nephaline basalt, at an average rate of 350 to 375 feet per month. Three hundred and fifty feet per month was considered low, and such a result called for investigation by the management of the causes which reduced the work accomplished to this figure.

The record month showed an advance of 395 feet and 8 inches. This speed in driving was obtained by careful planning of the work, so there would be no loss of time or idleness for either the men or equipment. This required a thorough study of the conditions that were to be met and overcome, and careful oversight to see that the plans adopted were carried out.

The plant used in this work consisted of;

• two 60-horse power boilers
• one straight line, two-stage air compressors
• one high-pressure, three stage, locomotive-charging compressors
• one compressed air locomotive
• and Sullivan "Class UE-2" 3-1-8 inch drills.

The working day was divided into three shifts of eight hours each.

Plan of Work.

In the actual tunnel-driving work, there were seven men to a shift; two machine drillmen, two machine helpers and three "muckers." Each shift was supposed to drill, load and shoot a round of from eighteen to twenty-two holes, drilled from 5½ to 7 feet in depth, as well as to load the "muck" resulting from the work of the previous shift into the cars, and deliver the cars to the compressed-air haulage engine.

The management feels that under the three shift plan the men do better work and take more pride in its results, owing to the fact that the men know that another shift is following close on their heels to perform the same operations that they have performed, and that the following shift depends upon the satisfactory completion of this shift's work for the accomplishment of their own.

The method pursued was essentially as follows:

Fig. The Heading—Showing Muck Pile, Car and Sheets in Ophelia Tunnel.

As soon as the smoke resulting from the shooting done by the previous shift was cleared, the new shift of drillmen, helpers and "muckers" all went to work, and the broken rock from the face was thrown back sufficiently to allow the columns for mounting the drills to be put in place. The two drillmen worked together, and the two helpers worked together in pairs, relieving each other at intervals; the "muckers" going immediately to work, getting the "muck" into the cars and on its way to the dump.

When the helpers were working on the muck pile, the drillmen were back of the work; looking up equipment; seeing that all the machine drills, steel, hose, tools, blocking, etc., that would be required for the shift's work were on hand, and, if anything was found missing, taking steps to secure it.

When the drillmen were working on the muck pile, the helpers were employed in bringing the required material up to the face, where it would be readily available.

It may be objected that this would be possible only in a short tunnel, but in this tunnel, about one and two-thirds miles long, this work was accomplished by each shift every day. As soon as the muck was cleared away from the face, the columns were put in place; the drills mounted, and the drilling of the new round commenced.

In clearing away the muck, care was taken that it should not fall back toward the face until a sufficient space was provided in which to set the columns. After the columns were set the muck was allowed, and in fact encouraged, to fall back, until it had filled the space in front of the face up to such a level that the tops of the jack screws of the columns could just be reached.

By this method, the back holes, or those nearest the top of the tunnel, were the first to be drilled, and the drillmen and helpers worked from the top of the muck pile. This did away with any form of staging, and while the drillmen worked towards the bottom of the tunnel, the muckers were removing the pile, thus always giving the drillmen a standing ground of proper height, or really a self-adjusting platform, much wider and more solid than any portable timber staging.

It was of course necessary for the muckers to finish loading out the muck before the drillmen reached the bottom holes or "lifters," but they did not stop work until the end of the shift was reached, as there was rail laying, and the placing of sheets, to occupy their attention until the holes were loaded and ready for shooting.

Everyone on the shift was busy from the time he reached the heading until the holes were loaded and fuses spit. The only time lost in the twenty four hours of the day was that required for changing shifts and the clearing of powder smoke.

Fig. Sullivan Air Drills in Ophelia Tunnel, Cripple Creek, Colo.

Full length mining columns were used in order to reduce the amount of blocking needed at the top and bottom of the columns, and to insure the removal of the muck from the face, clear to the bottom of the tunnel before the set up, so that resetting would not be required when the bottom holes were reached.

Care was always taken to see that the men were well supplied with all material for their work. Empty cars were always kept at the face; an extra machine drill was constantly on hand, so that if one of the drills in use required repairs, it could be laid aside, to be put in order by a skilled mechanic.

Thus the drillman and his helper were not delayed by making repairs. Plenty of sharp drill steel and water for use in the holes were kept close to the face.

Arrangement of Drill Holes.

The important matter of properly placing and drill holes was carried on as follows:

Fig. Arrangement of Drill Holes.

In the illustration, holes Nos. 1 and 2 are cut holes. These were drilled from six to seven feet deep, looking down, and were so placed and directed that their inner ends nearly met. The fuse for these holes was so cut that they were fired first and nearly at the same moment.

Holes Nos. 3 and 4 are cut holes, drilled looking up and about the same depth as Nos. 1 and 2. They were so directed that their inner ends did not meet, as in the case of Nos. 1 and 2. The fuse was so adjusted that these holes were fired just after Nos. 1 and 2.

Holes Nos. 5 and 6 are the back cut holes. They were drilled looking up, and so directed that their inner ends did not meet, nor did they extend beyond the top of the tunnel. These holes were shot together and just after Nos. 3 and 4.

Cut holes Nos. 7 and 8 look down, and were timed to shoot after Nos. 5 and 6.

Holes Nos. 9 and 10, the cut lifters, look down and extend below the proposed bottom of the tunnel.

Holes Nos. 11 and 12, the back rib holes, and holes Nos. 13 and 14, rib holes, look up.

Holes Nos. 15 and 16, also Nos. 17 and 18, rib holes, and holes Nos. 19 and 20, rib lifters, all look down and all extend beyond the line of the side walls, and were all shot at nearly the same time.

Where stiff ground was encountered holes A and B were put in, and shot with holes Nos. 1 and 2 and Nos. 7 and 8 respectively.

Where very stiff ground was found, holes C and D were added and shot with holes Nos. 5 and 6 and Nos. 3 and 4 respectively.

By analyzing the above it will be found that holes Nos. 1 and 2 take out or loosen a wedge-shaped portion of the rock, thus relieving the resistance to the action of the powder in holes Nos. 3 and 4 and holes Nos. 7 and 8. Holes Nos. 3 and 4 and Nos. 7 and 8 clear the way for holes Nos. 5 and 6 and Nos. 9 and 10. Holes Nos. 9 and 10 have a tendency to throw any broken rock above them out of the way of the remaining rib holes. Holes A, B, C and D serve simply to increase the effect of the holes with which they are shot.

By placing the holes in this way and shooting in this order, the break, with very few exceptions, always cleared the rock for the full width and depth of the tunnel, thus doing away with the necessity of following the heading with any work designed to break off projections.

Tamping material for use in the loading of the holes was always employed. It was found that by using this, the results obtained were most satisfactory, and that less powder was consumed.

Handling the Muck.

Said to be 3300 feet to Entrance of Ophelia Tunnel

Two tracks were maintained close to the heading. Before the shots were fired, steel sheets were placed on the floor close to the face, extending back far enough to receive all the broken rock. It was found important to have these sheets weighted, and enough muck was kept at the face to do this properly.

The sheets formed a smooth floor from which to shovel the muck, but unless the sheets were weighted, it was found that the vacuum created by heavy shots was likely to lift them and mix them with the muck, thus not only defeating the purpose for which they were intended, but actually increasing the labor of mucking.

The sheets behind the main portion of the muck pile served to receive part of the muck thrown from the face, and also to facilitate the handling of cars.

A convenience for saving time was the use of a flanged valve on the heading end of the pipe line, instead of the screw valve commonly employed. There was also a telephone system, one station of which was kept well up toward the heading. In case of accident, or when it was necessary to communicate with the portal or power house, the use of the telephone saved valuable time.

Ventilation.

The removal of powder smoke after shooting was accomplished by means of a blower and the compressed air system. As soon as the work of drilling stopped, the engineer would notice the fact that the demand for compressed air had ceased; he would then fill the receivers and pipe lines with air at 100 pounds pressure.

After the holes were loaded and fuses spit, the drillmen would open the gate valve at the heading, allowing a full stream of air under 100 pounds pressure to play on the face through a one-inch whistle cock. This volume of air coming with a high velocity, stirred up the smoke and mixed thoroughly with it.

The pressure in the pipe lines dropped rapidly, and as soon as the pressure reached twenty pounds the engineer started the compressor and kept the pressure at this point, and also started the blower, if it was not already running.

A 15-inch ventilating pipe was used and the smoke was soon thoroughly mixed with fresh air. It was seldom that men could not get to the face twenty minutes after the shots were fired.

It will be seen that every endeavor was made to save time, and that, these efforts being successful, there was a consequent reduction in cost. For various reasons the figures showing the cost per foot for this tunnel cannot be given, but figures shown by the management of this tunnel, compared with figures of the managers of other tunnels, driven under similar conditions of ground, cost of labor, fuel, powder, etc., show the cost of this tunnel to have been very low.

The men were well paid, but no bonus was given for progress above the average rate per month. The Work was done thoroughly; the alignment and grade of the tunnel were kept perfect, and it would seem reason able that the methods employed in driving the tunnel were responsible for its rapid headway and low cost per foot.

Acknowledgements are made to Mr. J. M. Parfet for information upon which this article is based.

^* Mine and Quarry, June, 1907.

I've seen also this article to be referenced to the May 1907 issue in a different source.