October 13, 1916. THE COLLIERY GUARDIAN 701 _____________________________________________________________________________________________________________________________________________________________________ laid flatwise, alternately with a quarter shaft bratticed off with 3 by 12 material, and the hoisting compart- ments divided by 4 by 6 buntons. No trouble was experienced in sinking until the bed of sand at the 38 ft. level was encountered. This sand carried a small amount of water and, as a shaft protection, a con- crete ring was put in behind the curb. The next trouble was experienced from the 42 to 48 ft. level. It had been the intention to assemble the shoe at this level, but what appeared to be a firm green clay proved to be jointed clay with a seam of quicksand through it and the exposed wall would not stand. Temporary 2 by 12 curbing was put in place, and then regular curbing carried on down. At the .50 ft. level, in order to safeguard the assembling of the steel shoe, 125 wooden mine ties, 3 by 4 in. by 4 ft. long, were sledged into the clay just below the curb as shown in the detailed sketch of sink- ing shoe. Steel angles, 6 by 4in., were fastened with lag screws to the under side of the ties. An excava- /SifricL 2 E £ I i Fig. 6.—Details of Sinking Shoe. tion 6 ft. deep was then made, undercutting the ties 16 in., and a false curb of 2 by 6 boards built. The shoe was then assembled at this point. The shoe consisted of four sheets of f in. steel, two 8 ft. long by 5 ft. high and two 14 ft. long by 5 ft. high, with 3 in. angles at the corners, and a 6 in. pressure angle placed 18 in. from the bottom of the shoe. The curbing w^as then built inside the shoe to a height per- mitting the jack screws to be placed against the curb timbers of the shaft, as shown in the sketch. The clay was then excavated, the shoe lowered into the sand, and pumping started. The sand carried about 60 gals, of water per minute, which would rise about 18 ft. above the sand when pumping was stopped. In order to avoid the formation of. cavities behind the curb, as little sand as possible was excavated. To prevent an inrush of sand under the shoe, at least 1| to 2 ft. of sand had to be left within the shoe. The method of sinking was to agitate the 3and at the bottom of the shoe and force the shoe through it by means of the jack screws bearing against the shoe and the curb of the shaft. Two methods were used to agitate the sand. First, while the men could reach the bottom of the shoe, they stirred the sand with spades. By this method the shoe was lowered about 78 in. in the sand. Later the pumping system shown in the sketch was used. In this second process the discharge of the No. 6 pump could, when desired, be sent through five |dn. pipes, as indicated in the drawing, and these five jets of water could be played upon the sand at the bottom of the shoe. It was found that these jets would agitate the sand sufficiently to permit the jack screws to push the shoe down, except when the sand was at too high a level inside the shoe, in which case sand would have to be excavated before the jet process could be resumed. In using this process the men would stir the sand with the jets for about 10 min., and then tighten the jack screws. When sufficient space was obtained between the timbers in the shoe and the curbing above, the jack screws of one side were removed, and sets of timber put in place on top of the timbers in the shoe, and then the other jack screws were moved. An advance of 18 in. per day was exceptional by this method. More often it was less than a foot. Necessarily some sand had to be excavated at times. This had a tendency to cave the dirt around the shaft, which in turn caused an excessive down pressure and broke the curbing apart a number of times. An attempt was made to overcome this trouble by supporting the curb with I beams and cables from the surface as shown in fig. 3. Ten 12 in. I beams were supported on cribs at the surface, and ten 8 in. I beams were swung under the 4 by 6 angle below the ties, these beams being con- nected by 20 | in. steel cables. When the sinking was resumed, the curbing continued to break, the I beams bent, and two cables were broken. Since it appeared impossible to hold the curb, it was decided to timber the shaft solid from the 8 ft. level (where the most uniform break occurred) to the bottom of the shoe, and then drop this portion of the shaft through the remain- ing 5 ft. of sand. To do this, the ties were driven back into the wall and solid timbering put in between the shoe and the upper curbing of the shaft. The entire shaft curbing from the 8 ft. level down was then tied together with 2 by 6 in. stringers. At the 8ft. level, 2 by 4 in. by 16 ft. planks were spiked to the lower curb, the upper ends projecting above the break as shown in fig. 4, preventing the loose material from falling down the shaft. The jet sy,stm, with occasional excavations of sand, was resumed, and the shoe, with 50 ft. of curbing, was lowered through the sand. In landing the shaft on the solid, seven boulders from 1 to 2 ft. in diameter were encountered. Six of these were under the cutting edge of the shoe, and were removed only after being broken up by means of a long chisel and sledge. While lowering the shaft through the sand, the upper timbers of the shaft buckled 18 in. out of line. This necessitated re-timbering of the shaft from the top of the sand to the surface, an expensive undertaking, because the old timbers had to be cut out and replaced in sections. On completion of the re-timbering, sinking through the shale was commenced. Three shifts of four sinkers each were used with an average daily advance of 5 ft. The only problem involved in sinking through the shale was the elimination of the water, a considerable pro- portion of which was choked off when the solid was reached. This water was taken care of by placing a water ring at the 85 ft. level with a pump located at that point to elevate the water to the surface as shown in fig. 5. - Air Shaft Sunk by Drop Shaft Method. The air shaft was located 350 ft. from the main shaft, and its sinking conditions were similar except that the surface at this point was 10 ft. lower than at the main shaft, making the actual distance to be traversed to the solid. 63 ft. 6 in. The equipment wa*s the same as that used at the main shaft. The air shaft followed a drill hole tapped by an entry from the main shaft, so that most of the water was drained through this drill hole and then pumped to the surface. Two shifts of three sinkers, one top man, and an engineer were employed. The size of the excavation was the same as before, 8 by 14 ft. The steel shoe was similar to the one in the main shaft, except that it was 10 ft. high instead of 5 ft. The timbering for the first 30 ft. above the shoe consisted of 4 by 6 laid flat, tied together by lag screws fin. diameter by 10 in. long, spaced 2 ft. apart. The shaft was divided into three equal compartments by 4 by 6 buntons as shown in the accompanying top view. The middle compartment was left free, and was used for hoisting purposes. The end compartments were braced by 4 by 6 extending from the ends of the shaft to the sides. Four steel straps f in. by 2 in. tied the shaft timbers together from top to bottom. An excavation 10 ft. deep was first made, the shoe assembled and lined with- timbers. The sinking was continued until the shoe was hung up by the friction on the sides. Then a platform was built every 5 ft. in the end compartments. These 5 ft. chambers were filled with sand to give additional weight, and the sinking con- tinued. The ground surrounding the shoe gradually broke in an oval shape. At one place it was necessary to fire a small charge of powder in order to loosen the ground sufficiently at one end of the shaft. TOP VIEW 4 x 6 Flat SECTION A.-B 14' B vvu /-■ 2 Strap* U Lag Screws ‘Sand.- .Drift: I 7/ Fig. 7.—Top View and Section of Shaft. As the shoe was sunk, timbers were added at the top of the curbing. This method of building the curb at the top is decidedly better than that of adding timbers at the bottom, since the timbers are placed much more accurately and expeditiously. One difficulty experienced in the drop-shaft method was to keep the bottom of the shoe level. When one side of the shoe got lower than the other it kicked the opposite side outw’ard. To right it, the lower side was blocked until the higher side caught up. The progress through the drift material, until the sand was reached, was slow, much slower than at the main shaft. The drop shaft went much faster, however, after reaching the sand. In fact, the difficulty at that time was to keep the bottom of the shaft from moving faster than the top. When within 10 in. of the bottom of the sand the shaft broke apart 20 ft. up from the shoe. This was due to the fact that the movement of the shoe was faster than that of the top of the shaft, and to the insufficient strength of the straps connecting the top and bottom of the curb. At this point (20 ft. above the shoe) the curb separated from 6 to 8 in., and the upper part of the shaft kicked over 9 in. north and east of the lower part. A temporary platform of 8 by 8 timber was put in the end compartments of the shaft at this place, and time given for the upper part of the shaft to settle down before .starting the excavation again. The sinking was then continued, and the shoe landed on the solid without further difficulty, aside from hitting two small boulders at the bottom of the sand. As the excavation was larger than necessary for an air shaft, it fivas decided to cement the shaft for a distance of 28 ft. from the bottom of the shoe, in order to shut off the water. A wall of cement 4 to 8 in. thick was accordingly then constructed. After the cement was given time to set thoroughly, the excavation was again started in the shale, and continued without difficulty to the coal. Sinking through the shale in the air shaft cost slightly more than in the main shaft, because work in the mine prevented as careful supervision being given the sinkers in the air shaft. One difficulty encountered in drop shaft sinking was in keeping the position of the shaft vertical. At one time this shaft was 2 ft. out of plumb. By regulating the movement at the bottom of the shoe, the shaft partly righted itself, until at the finish, in a total depth of 63 ft. 6 in. io the shale, the bottom of the shaft was 16 in. to the south and 10 in. to the east of the top. Part of this variation was remedied in the cementing of the shaft. A much larger amount of sand was removed in .sinking the air shaft by the drop shaft method than in sinking the main shaft. This could be done without danger of a cavity forming, because the surface dirt followed the air shaft down as it descended. When the sinking through the sand was completed, the surface directly surround- ing the air shaft had caved to a depth of 15 to 16 ft., and for a distance of 20 ft. in all directions from the shaft. In fact, all the shale that was removed through the remaining 92 ft. to the coal did not fill this space at the surface. A comparison of the costs of the two shafts is as follows :— Labour :— Through drift material Through sand Through shale Main shaft. Dols. . 916-80 ... . 1,941-80 ... . 1,065-68 ... Air shaft. Dols. 789-08 541-62 1,213-30 3,924-28 ... 2,544-00 Superintendence . 600-00 ... 435-50 Re-timbering Cementing . 1,343-23 207-68 Total labour cost . 5,867-51 ... 3,187-18 Materials :— Curbing Supplies . 1,878-62 ... . 900-14 ... 1,195-17 642-74 Power, light, water, insurance etc .’ 1,248-50 ... ________ 649-71 Total curbing, etc., cost... 4,027-26 _________ _________ 2,487-62 Total cost of shafts ....... 9,894-77 ... 5,674-80 Conclusions. In this particular work there was no question about the superiority of the drop shaft method of sinking. It made a net saving of 4,300 dols. in the total cost of the air shaft compared with the main shaft. A saving of 2,700 dols. was effected in the labour cost, while in the cost of materials, power, etc., the saving was 1,600dole. A saving in time also resulted, 30 day,s being required to traverse the sand with the main shaft, while the air shaft was dropped through it in 17 days. From the results obtained in these two shafts, and from the experience of others in the western interior coal field, the author believes that the drop shaft method of sinking is the safest, most economical, and most successful that can be adopted for sinking through soft material that lies within 100 ft. of the surface. At greater depths a variation of the method can be used by first sinking a larger shaft close to the soft material, and then telescoping a drop shaft within it. ______________________________ Exports and Imports of Mining Machinery.—The value of imports and exports of mining machinery during September are given below :— September. Jan.-Sept. 1915. 1916. 1915. 1916. Imports _________ 10.042 ... 17,863 . 68,218 ...105,321 Exports __________ 45,006 ... 79,936 .. 444,653 ...528,934 These figures are not inclusive of prime movers or electrical machinery. According to destination, the value of exports was as under :— September. Jan.-Sept. 1915. 1916. 1915. 1916. ___ £ £ £ £ Countries in Europe ... 2,336 ... 8,333 ...46,762 ... 42,447 United States of America... — ... 144 .. 113 ... 649 Countries in S. America ... 4,456 .. 1,804 ...15,366 ... 17,851 British South Africa ... 21,797 ...47,326 ..194.255 263,643 East Indies ...... 4,011 ... 7,417 ...42,235 ... 66,265 Australia ................ 928 ... 376 ...19,124 ... 16,270 New Zealand ........... 1,024 ... 676 8,287 ... 11,196 Other countries .......... 10,454 .. 13,860 ..118,511 ...110,613 Total ............ 45,006 ...79,936 ..444,653 ...528,934 The following shows the value of exports of prime movers other than electrical :— September. Jan.-Sept. 1915. . 1916. 1915. 1916. All prime movers (except <£ .£ ,£ <£ electrical) ........... 516.234 ,.335.876,..4,850,987.. 3.249,164 Rail locomotives _______ 290,900... 97,268...2,079,121... 923,955 Pumping................ 48.050 47,765... 366,313... 395,591 Winding................ 256... 3,882... 12,292... 13,307