430 THE COLLIERY GUARDIAN. March 2, 1917. Extending the Work. As Messrs. Simon-Carves and Company had proved the success of their system on the upper portion of the shafts, we decided to enter into a further contract to dry the whole length of the shafts, which virtually meant treating the tubbing, and the brickwork immediately below it. Close inspection proved that the tubbing was sound, and could, by systematic wedging, be made quite tight, except for two or three bad joints near the bottom in No. 2 pit, and the “ making up ring ” in No. 1 pit. In No. 2 pit there were leakages just below the tubbing, but as the brickwork was in fairly good condition, it did not present much difficulty. In No. 1 pit, the brick- work below the tubbing was loose and open-jointed, and at a point about a yard below the tubbing there was an opening through which flowed a feeder of at least 20 gals, per minute. On August 21, 1916, work on the second contract was commenced, by injecting in the top ring of tubbing. The tubbing is of the usual English type, with external flanges, each segment having two 1 in. plug holes cast in the middle bracket; and it was through these holes that the cement liquor was injected. In order to do this, the plugs were bored about 2 in. deep, and an internal thread was tapped in the hole to receive a | in. pipe. The injection pipes for this work were IJin. at the end, to which the three-way valves were attached, and reduced to $ in. to fit the plug holes in the tubbing. Having screwed the plug holes, the remainder of the plug was bored out and the injection pipe, with valve attached, was quickly screwed in, the valve being set to allow the water to escape until the operation was completed. This only took a few minutes, and the escape of water was not very serious. It was not intended to cement the whole of the space at the back of the tubbing, but to make good the joint between the top of the tubbing and the foot of the coffering, with the. object of preventing the surface water getting past 'that point. The next operation was to seal the tubbing curb and the bad places in the bottom rings in both shafts. In No. 2 shaft this was successfully accomplished by injecting about 25 tons of cement behind the tubbing and in the brickwork below. Special Problems. In No. 1 pit, however, the problem was far more diffi- cult, owing to the “ making up ring,” before mentioned, and the bad state of the walling. The engineer in charge had to use his utmost skill to prevent the wedges and bricks from being blown out, and so causing a repeti- tion of the trouble which we had in the previous December. About 20 tons of cement were injected above and below the “ making up ring ”—as much as five tons at a single operation—but this did not seal up the tubbing curb, as was proved by the fact that a considerable flow still came from the hole previously mentioned, about 3 ft. below the bottom of the tubbing. It was evident that there still remained a large cavity behind the tubbing curb'through which the water could escape, and this could not be closed until the brickwork was made sufficiently strong to resist the pressure of the injected cement. The brickwork was therefore repaired with bricks set in cement, and, in order to allow the feeder to escape (otherwise it would have burst out the new brickwork) a special concrete block (see sketch) was moulded, having an injection pipe cast into it, and was built into the shaft wall. After allowing three days for setting, we commenced to inject, but the water burst through in another place. Another block was moulded and built in as before, but at the next injection the water again. burst through at still another place. The third bad place was treated as the others, and this time we were successful in com- pletely sealing off the flow. By the end of August the water was practically stopped, although there still remained several small feeders (amounting to not more than 5 gals, per minute in all) which had to be finally checked before the job could be said to be complete. These were of no great moment, and it was agreed to leave them until the winter rains came to> raise the water level and increase the pressure, when they could be treated together with any other leakages which it,was thought might by then have developed. Beneficial Results. We were now able to notice the benefits which had accrued. The pumping was reduced from 16 to six hours per day, and the ventilation increased in efficiency, although the fan was now running at a reduced water gauge; and we were free from those irritating stoppages caused by water breaking out into the winding shaft. The spring on the surface now flowed continuously, increasing in the winter months to about 25 gals, per minute, in addition to which the two culverts leading from the shafts to the river, which had always collected a certain amount of surface water, now discharged more than double their former volume. In the early part of January this year the contractors devoted three or four days to completing the sealing off of the few small leakages which still showed, leaving the shafts practically dry. The length of time consumed on this job must not be taken as a criterion: indeed, the work, if carried on con- tinuously, would not have required more than two months. Messrs. Simon-Carves were at the time engaged in freezing and sinking the upper portion of the new pits of the Llay Main Colliery Company, situate about two miles away, and an arrangement was made with the contractors’ resident engineer (Mr. A. D. Brydon). to prosecute the work at such times as was mutually convenient,,he., when we could put the shafts at his disposal, and when he had men at liberty. This arrangement proved very satisfactory to both parties, and therefore no attempt was made to complete the job in the shortest possible time. The writer has to thank __________________________________ Mr. Brydon for much valuable assistance in preparing this article. Advantages of Cementation. A noticeable feature of this system is that, although it may take weeks to finally stop every small feeder, it is only a matter of days, or even hours, after a success- ful injection before the benefits are apparent. There appears to be a great future before this method of cementation, not only in the treatment of old .shafts, as in the present instance, but in sinking new shafts through water-bearing strata. Running sand, water-bearing marls, and gravels do not lend themselves to treatment by this method, but most of the stratified rocks met with in the coal measures do; and it is possible to inject cement in advance of the sinking, seal off the water, and save some of the cost and inconvenience of Dumping during sinking' opera- tions. The ground having been cemented, there would be no need for coffering, with its attendant liability to failure through unequal, subsidence and distortion, but an ordinary brick lining would serve quite well, take up less room, and thereby save excavation. Another point in its favour is, supposing at any time, either through percolation or distortion, the cemented ground should develop a leak, it is not a great matter to treat the shaft with one or more injections in the immediate locality of the leakage, and effectively repair the damage. _____________________ MINING ACCIDENTS AND LABOUR IN 1915.* The total number of persons employed at mines and at the quarries under the Quarries Act in the United Kingdom and the Isle of Man during the year 1915 was 1,035,600. of whom 973,473 were employed in or about mines, and 62,127 in or about quarries. Of the 973,473 persons employed at mines 766,542 worked under ground, and 206,931 above ground; of the latter, 7,661 were females. Compared with the preceding year there was a decrease of 163,265 males working under ground, and a decrease of 21,654 males and an increase of 937 females working above ground, making a net decrease of 183,982 persons. In mines under the Coal Mines Act, 754.673 persons were employed underground, and 198,969 at the surface, a total of 953,642, or a decrease of 180,104. Table A gives a general summary of the number of persons employed at mines and quarries:— Table A.—Persons Employed at Mines under the Coal and Metalliferous Mines Regulation Acts and at Quarries under the Quarries Act respectively, classified according to Age and Sex. Act. No. of mines or quarries at work. Under- ground in mines and inside at quarries. Males. Above ground at mines and outside at quarries. Total under and above ground. Comparison of total No employed with that of preceding year. Males. Females. Coal Mines Act Metalliferous Mines Act Quarries Act Total in 1915 Total in 1914 2,871 498 6,763 754,b73 11,869 40,029*' 191,418 7,822 22,000 7,521 140 98 9 3,642 1 19,831 62.127 - 180,104 - 3,878 - 16,781 10,132 . 10,791 806,571* 979 881f 221,270 249,683 7,759 6,799 1,035,600 1,236,363 - 200,763 + 152 * Including two females employed inside a quarry. f Including one female employed inside a quarry. .Table B gives statistics relating to employment in coal mines, arranged according to counties :— Table B.—Persons Employed at Coal Mines classified ac cording to Counties. Counties where chiefly worked. York ................. Glamorgan ............ Durham .............. Lancaster.............. Monmouth ............ Northumberland ..... Derby .............. Stafford............... Lanark ............... Nottingham............ Fife................... Other counties ........ Total Under- Above ground, under ground. ,----------A-------x ano Males. Males. Females, above ground. 108.311.. . 32,371 . 41 .. 140,753 112.170.. . 21,737... 97... 134,004 97,195 26,935... 139... 124,269 69,099 17,389...2,985 .. 89,473 46.740.. . 7,938... 72 .. 54,750 33.201.. . 9,264... 45... 42,510 42.967.. . 11,404... 9... 54,380 41.987.. . 13,289... 66... 55,342 40.881.. . 9,284.. .1,587... 51,752 30.309.. . 8,167... 9... 38,485 17.348.. . 3,434...1.027... 21,809 103,312... 27,370...1,395... 132,077 Total in 1915 ........ 743,550...188,582...7,472... 939,604 Total in 1914 ________ 901,857...208,718...6,550...1,116,648 Accidents.—In 1915, 1,298 separate fatal accidents occurred in and about the mines and quarries of the United Kingdom, causing the loss of 1,392 lives. Compared with the previous year, there is a decrease of 2 in the number of fatal accidents and an increase of 54 in the number of lives lost. Of the 1,298 separate fatal accidents, 1,228 causing the loss of 1,318 lives happened at mines, and 70 causing the loss of 74 lives happened at quarries. At mines there was, as compared with the previous year, an increase of 23 in the number of fatal accidents and of 75 in the number of deaths. The death rates for the year were 1'545 per 1,000 persons employed underground, 0'648 per 1,000 persons employed on the surface, and 1'354 per 1,000 persons employed under and above ground at all times. In classifying the accidents according to place or cause, it is found (Table C) that 51'7 per cent, of the * From Part II of the General Report on Mines and Quarries for 1915, edited by Sir Richd. Redmayne, H.M. Chief Inspector of Mines. deaths were due to falls of ground, 30-3 per cent. to. miscellaneous causes Underground, 3T per cent, to explosions of firedamp or coal dust, and 4’8 per cent, to shaft a.cc-dents. Explosions of Firedamp or Coal Fust.—There were 16 fatal accidents by explosion of firedamp or coal dust, resulting in 41 deaths. Compared with the preceding year these figures show an inci ease of six in the number of explosions, and of 15 in the number of deaths. Th- lealh-rate from explosions of firedamp or coal dust per 1,000 persons employed underground in 1915 was 0 <*53, whilst the average death-rate from this cause during the last 10 years was 0T95. Of the 96 fatal and non- fatal explosions, 82 were caused by naked lights, two by defective safety lamps, nine by shot-firing, and three by miscellaneous or unknown causes. Of these 82 explosions, 12 had fatal ivsuits to 15 persons. So long as mines which occasionally produce firedamp are worked with naked lights, explosions of this class will continue to occur, and existing rules are inadequate to prevent them. The Scotch and the South Wales divisions, though employing only about 54 percent, of the number of men employed in the remaining divisions, and producing only 52 per cent, of the output, had more than twice as many explosions from the use of naked lights. Falls of Ground.—681 persons were killed by falls of ground at all mines under the Coal and Metalliferous Mines Regulation Acts, an increase of 77 on the figures for the previous year. One accident caused four deaths, 15 two deaths each, and the remaining 647 one death each. Comparing the number of fatal accidents and deaths from falls with the total number of fatal accidents and deaths at mines, it appears that falls were responsible for 54 per cent, of the total number of accidents and 51’7 per cent, of the total number of deaths. Compared only with fatal accidents and deaths underground, the percentages were 60‘4 of the accidents and 57'5 of the deaths. Shaft Accidents.—Fifty fatal accidents causing 63 deaths, or 4 8 per cent, of the total number of deaths in and about all mines under the Coal and Metalliferous Mines Regulation Acts, were caused by shaft accidents. One accident caused ten deaths, one caused four deaths, another two deaths, andthe remaining 47 caused one death each. Sixty-one deaths occnired in mines under the Coal Mines Act, and two in mines under the Metalliferous Mines Act. The death-rate from shaft accidents per 1,000 persons employed underground was 0'082. Miscellaneous Underground Accidents.—Under this division are included all underground accidents other than those from explosions of firedamp or coal dust, falls of ground and shaft accidents. Under this heading in 1915 there were 368 separate fatal acci- dents and 399 deaths,