Show IN METAL MINES FOR SAFETY by byron 0 pickard water in water used in is added at the hose nozzle that is to say a dry mixture of sand and cement passes through 1 the gun and through 6 the material hose to the nozzle where water is added in proper proportion to insure adhesion of the to the face of the rock and timber surface four to five gallons of water per minute should be avail available availably abl e As the water joins the mixture within the nozzle the water pressure must exceed the air pressure by about 20 pounds in each experiment mine water was used in mines where the water is either acid or strongly alkaline it would not be advisable to use it as the best permanent qualities of b unite are obtained with relatively pure water the writers did not find any appreciable variation oi of effect on the from a range of water temperature between 50 and compressed air in connection with the air ir pressure required for the operation of the cement gun varies varie s with the length of the hose the kind of work being done and the distance at which the man holding the nozzle must stand from the shooting surface in each mine in which the authors experimented the maximum air pressure was about 90 pounds the nl N l 1 gun required cubic feet of actual free air per minute at 35 to 60 the nozzle pressure for timbers was about 8 to 15 pounds with 50 feet of hose with feet of hose from 21 to 5 pounds increase was required in building the buttresses and the bulkhead for the fire door 35 to 40 pounds air nozzle pressure was used permitting a much greater feed and faster work toward the top of the bulkhead and on the finish the nozzle pressure was cut down to 15 pounds owing to fo the fhe cramped working places the lowest pressure used in the experimental work was 8 pounds the nozzle air pressure should be adequate to insure free flow through the hose and adhesion of the material effect of water in the compressed air water in the compressed air causes clogging in the gun causing much trouble and long delays where this trouble is experienced a water trap or if none is available a bleeder should be inserted into the air line number of applications theoretically the greater num number berof of coats the better the As each coat is allowed to set its pores will be sealed by the following coat and any cracks that may develop are thus covered and sealed three coats gave excellent results for rock work the first coat should be as thin and dry as possible we endeavored after some experimentation to cover rock surfaces with a thin neat coat of cement permitting free rebound this coat was followed with 3 16 to 14 inch of after setting over night the third coat was put on about 14 inch thick making a total thickness on rock surfaces from 12 to 34 inch on timbers covered with enforcing wire the first coats should cover the reinforcement and therefore is often 14 to inch thick this coat is followed with at least two thin coats bringing the total thickness to 12 inch or more in the man holding the nozzle should not permit the to pile up but he should work the nozzle back and forth spreading the in thin th in layers or coats as in painting sand pockets should be avoided and cracks and pores filled up conclusion of article the opening chapters of which appeared appear edIn aln last ast issue oct 30 1922 effect of the rebounding sand in striking the face only part of the mixture of wet ivet sand cement sticks to it the coarser sand particles especially in the first coat are not cemented together tog ether hence the rebound is often as much as 20 per cent of the first coat during the second and third coats the amount is less as the sand finds a surface to cling to rebound is essential to make good it varies with the air pressure and the distance the nozzle is held from the face free rebound prevents sand pockets and insures tamping of the by the coarser rebounding particles the rebound contains very little cement but more than 95 per cent sand if kept clean this material ma may y be used again after screening sprinkling of underground where the temperature pera ture is constant and the humidity relatively high sprinkling may improve the quality of the but it is not absolutely necessary hence sprinkling was seldom done in these experiments in surface work sprinkling between coats and sprinkling on the finished job for several days prevents the development of superficial cracks through rapid drying length of the hose hose lengths are usually limited to feet vertically above the machine and feet horizontally zon tally size of cement gun the gun used was a an r nl N l 1 or medium sized cement gun it is recommended by the cement gun co inc for mine work and is favored by practically all the mining companies now using guns this cement gun has an actual capacity in excess of square feet of per hour 13 12 inch thick it requires cubic feet of free air per minute at from 35 30 to 60 pounds pressure and about four gallons of water at a pressure of 10 pounds higher than the air pressure its shipping weight is 1500 pounds in the experimental work described in this paper the best est capacity obtained was square feet inch thick per hour the maximum material used in an 8 hour shift was 30 bags of cement and 90 cubic feet 33 cubic yards of sanu material for square feet the re results stilts were variable for square feet of surface and approximately Vs 12 inch ch thickness the follows following ng quantities of material aderial m were used on four i jobs respect respectively respective iv ely job no cement no bags sand cu st ft 1 3 9 2 8 3 4 23 3 7 these variations were probably due to varying of and to varying rebound I 1 i gun crew to do efficient steady work the gu gun n crew should consist of four men two atthe at the gun and two at nozzle they should be ranked as chief and d alsista assistant ri t 91 n men and chief and assistant nozzle men the assistants can alternate with the chiefs in keeping the gun loaded and operating era ting in moving the hose keeping out the kinks tracing trouble in the material hose furnishing furni shing light alight a alig ht to the noza men inen and in operating the nozzle the nozzle r work is tedious and harassing as he is being constant y pelted belted with rebound is water soaked from running wate avater and spray his armago ba back ck and forth lifting the beav vi his g brating hose his goggles lyo 99 les are dimmed with the spray light when working underground is poor on account ot of the le compressed air dratt draft he of aften ten works in restricts restricted una en places and the cement nent dust as a consequence is disagreeable unless lie he wears a respirator while working b the nozzle his throat and nose quickly become coated with ce cent it is customary to pay the gun crew the highest prevailing mine wage and in the writers opinion it is deserved especially by the chief gun runner and chief nozzle man in addition to the gun crew a mixing crew generally two mixers is necessary also a delivery crew composed of one or more car men costs of A summary is given of the unit costs on the cooperative experiments the work was largely experimental yet it was done on a practical scale rather than on a laboratory scale the labor was generally untrained the work had to be carried on without interference to the re regular 6 ular mine operations hence these costs are considerably sider ably higher than actual costs would be where was made as a regular mine operation the labor costs could probably be cut from 15 to 25 per cent possibly mo more re as lost time cost was often greater than working cost the material costs will of course vary with the location of the mine and with the mixtures used TABLE 2 UNIT COSTS FOR EACH experimental experiment no I 1 brattice per sq ft ya in thick labor hours min cost screening and mixing 2 30 placing chicken wire 3 18 shooting 2 1 50 total 2 38 material Cei cement nent bags bat 3 at sand cubic feet bat 9 at cu yd nails pounds 3 chicken wire square feet 1 mesh total cost of qunitin per square feet 1215 experiment no 1 2 station timbers per sq ft Ys in thick labor hours cents cost screening and mixing 21 2 13 1 3 at placing chicken wire 2 ya at 75 1 I 1 at shooting 2 21 13 1 3 at 75 11 1 1 16 ja at cleaning gun 11 1 1 13 3 at 75 23 2 3 at total 62 at 75 at total labor cost material cement bags at sand cubic feet 8 at cu yd nails pounds 37 chicken wire square feet Y mesh total material ma terral cost total cost per square feet 1337 experiment no 3 rock work slate sides of inclined three compartment shaft per sq ft vz to 1 thick labor hours cents cost screening and mixing and sacking 28 at shooting 1 at 2 at 75 delays ra at ila at 75 total labor 43 at 35 at 75 material cement bags 48 at sand cubic feet at 7 ya total material total cost per square beet feet 1207 6 experiment no 4 rock work and timbers prevention of swelling ground and fireproofing of timbers yz yi in thick sides and back only 2700 sq ft of I 1 in chicken wire 2 sq ft of walls not wired per square feet labor hours cost 2 66 placing chicken wire mixing and screening hauling mix to job cleaning up 47 time lost delays dinner vz 32 hr etc 84 1 total labor 1489 material cement bags at sand cu ft 92 3 at a t chicken wire sq ft at nails at total material total cost of per sq ft 1685 total labor cost iiii total material cost for total cost of experiment cost per lineal foot of experiment no 5 rock work test to prevent swelling of balls walls in main ft section sq ft vz 32 in to ya in thick per square feet labor hours cost and setting up gun mixing and screening hauling mix to job time lost delays dinner yz lir hr total labor I 1 material cement bags at sand cu ft at total labor cost total material cost total cost of job cost per lineal foot of experiment no 6 and steel fire door in fireproofed fire proofed section cu ft of per cubic foot labor hours cost m 2043 1265 mixing and screening 2353 hauling mix to job 1838 1247 time lost delays dinner ya hr material cement bags at sand cu f ft t at lumber bd ft 22 at 64 total material total unit cost per cubic foot total labor cost total material cost total material cost door 18 ft vt 11 rod iron for 22 bolts and nuts 2 pr 12 strap hinges 30 ft angle iron 1656 lbs ibs 3 16 sheet metal total cost of bulkhead and fire door the excessive total cost is due to the high back in the drift caused by loose ground falling out when the timbers were removed the bulkhead is 17 feet high and is 8 feet above the top of the door frame the average bulkhead should not cost over one half of the above amount eipl experiment no 7 fireproofing old timber head 2700 sq ft yi in to ya H in thick per square feet laboz labor hours cost placing metal lath and setting up mixing and screening time lost delays dinner 44 building scaffold 89 total labor 1258 material cement bags at sand at cu ft at met lath at nails pounds at 08 1018 total material 1749 total unit cost per sq ft total labor cost total material cost total cost experiment no 8 rock work underground air receiver sides f loor floor back of rock drift and face of concrete dam dain vi thick a per square feet labor hours cost 2 hauling mix to job 51 rigging machinery 26 63 balling bailing out 12 20 washing down 4 mixing material 10 53 total labor sq ft total extra labor laying board track water line mucking back in clam am bracing ia total labor sq ft including preparation work 1466 material mixture 2 to I 1 cement bags 26 3 y 91 0 au U sand cu ft 64 64 total total cost of geniti g g p per e r sq ft including extra labor 1858 la oa total cost of excluding extra labor 1055 note mechanical concrete mixer was used experiment no 9 timber work eight sets of three compartment vertical shafts and lagged sides vi in thick per square feet labor hours cost metal lath mixing and screening 86 cleaning up 34 lost time 1 1 total labor 1620 i 95 material cement bags sand cu ft 97 78 met lath 1034 nails pounds 6 35 total material 8 6 total r rost post ost per sq ft 1781 cost per lineal foot of shaft 1291 lost time cost per lineal foot note mechanical concrete mixer was used experiment no 10 lining furnace room in change house sq ft metal lath sq ft rock side not metal lathed bathed sq ft united ff yz in thick sq ft burlap used for uneven surfaces per square feet labor hours cost 4 78 placing burlap placing metal lath mixing and screening lost time total labor cost 1433 1732 material cement bags sand cu f ft t 1017 burlap sq ft nails pounds 57 met lath sq f ft t 43 total material cost 1007 total cost per sq ft 1739 experiment no 11 rock work 94 ft section of ground in shaft per square feet labor hours hour cost preparatory cleaning mixing and screening lost time total labor material cement bags sand cu ft 9 26 0 37 total material cost per sq ft f t 0 total cost 0 0 experiment no 12 larg s underground timber preservation test 4 total area sq ft per square peet feet labor hours cost 0 6 metal lath 0 mixing and screening lost time 1200 total labor 0 0 1517 material cement bags sand cu ft 1687 67 met lath 0 total material 1104 total cost of 2621 total cost per sq ft less lost time 1998 u no 1 11 building transformer house 1800 sq ft ya y in thick per square feet labor hours ho 1 3 cost building frame placing metal lath mixing and screening moving and setting up gun wetting boards and g unite lost time total labor 1359 t material Lf lumber imber bd f t cement bags sand cubic ft met lath sq ft 1083 nails pounds 55 total material 7 1012 total cost per sq ft 1765 grand total cost of transformer house estimated cost if had been built of concrete experiment no 14 fireproofed Fire reproof proofed ed frame assay offrice off fice 2900 goo sq ft g united sq ft covered with metal lath sq ft covered with chicken cli icken wire J in thickness of per square feet labor hours cost placing material lath fath 97 moving and setting up gun mixing and screening lost time total labor 1117 5 87 materials cement bags sand cubic f ft t 8 wire sq ft 1067 nails pounds 6 plas paris lbs ibs 1 17 a S total material cost M total cost per square beet feet i 1 average material tt erial units the amount of cement and sand for three coats 3 to 1 mixture for square feet of surface vi winch ia thick in the several experiments varied as follows cement from 26 to bags average bags sand froni from 64 to 1687 cu ft average cubic feet nails 36 pounds per square feet i ware total area to be covered plus 10 per cent ceni average labor units the average units of labor in these expert exic ments were as follows surface sin face work woric 52 inch thick from 1117 to 1433 man hours per square feet average man hours 13 m 3 underground work ork ta inch thick rock from to i man hours per square feet average man hours g rock and ami 1489 hours la timbers man hours average man solid unite bulk bulkhead hend man hours per cuble cubic foot ite time per St square liture feet with a full crew three coa t of for on square feet of timber and rock can be shot in two nouis hours rock work alone J hour is required TABLE 3 recapitulation of costs of the experiments per sq ft rock hock work k inch thick to 1207 12 1 07 average cost 98 ag timber work required 32 in thick 1216 to lu average cost 1578 ia 0 rock and timber work in y in thic thick 1600 1685 summary of important practical points be several points learned in these experiments may lay summarized as follows 1 the tran transformer stormer house built at the pi y would have been better and cheaper had 15 pound building bul b paper attached to ding 16 inches apart been SUD k buted for the 1 inch plank as the planks warped and saru cracking the easily kiy 2 metal lath has only one advantage it is more reattach fitted into tight places one inch poultry netting for to en enforcing for caig is cheaper and though it costs more t to atta the timbers the finished is of far better quality qua ed 3 when there is doubt should b be u on certain rock walls and concrete dam faces face s Y the |