Show holdi holding ng the osburn fault the bunker bullion published at intervals by the employees of the bunker hill and sullivan mining company of kellogg idaho gives a most interesting description in its last number of the concrete work being done in the kellogg tunnel where it passes through the osburn fault the article being written by max G richardson mr richardson says bad piece of ground it is quite generally known that when the bunker hill mine was run in 1900 1902 a great deal of difficulty was experienced in passing through what is known as the osburn fault two at least of the men who worked all through that strenuous piece of tunneling are still on the bunker hill payroll J W jarrett who is now night watchman and willard furbush who subsequently worked for a long time in the mills and who is now an operator at the smelter just prior to hitting the fault proper these men tell of some hard breaking ground which was so short that it off badly and had to be timbered up very quickly then some soft talcy dalcy ground was encountered and this had to be handled by the method according to jarrett one day shift crew got about ready to put in a set of timbers the night shift had so much difficulty placing the set that they finally put the cap upon a post which was a foot too short in endeavoring to change the post the next day the fault broke out pouring a mixture of quicksand and water under pressure through every crack it could find with such force that the stream shot clean clea n across the tunnel and would tear the skin from a hand held in its course move much muck no one seems to know the exact number of cars of muck taken out of this one set but all agree that it ran into the hundreds and that it took ellmost thirty days of constant work and desperate attempts before the next advance of five feet was made and the next set finally placed six by six inch timbers twelve feet long were used as for the sides and roof and were driven in by a rammer made of a big pole having three bolts running crosswise through it so that six men could swing it to the face boards were used and all cracks in the rock were wedged tight with shingles subsequently as new timbering became necessary new posts and caps were put in between the sets already in place until at the present time there is an almost unbroken row of sets for quite a distance with no room for further re in the many years that have elapsed since the fault was broken into the water has been thoroughly drained out and it is anticipated that no very great difficulty will be experienced in opening up above the tunnel sets by regular operations using extraordinary care to prevent a run which would tie up traffic in the tunnel and thus force the mine to shut down consequently mr easton decided to put a concrete arch under each of the worst places three timber men J M erickson arnie and frank kambel with the following assistants paul kaloper Kal opet silas smith W H and clifford caughill have been at the work for some time three eaves caves running from thirty to sixty feet in height above the tunnel sets have been caught up some very bad ground has been held in place by and breast boards and angle posts have been set outside the tunnel sets to take the load off the old timbers several new tunnel sets have been set in place and at the present time concrete walls and arches are being poured in a 50 foot stretch of bad ground which has considerable weight and has a tendency to run the osburn fault has not been tapped yet but erickson who has the timbering in charge feels confident that it will not occasion much trouble this time how it Is being done the first step in concreting is the placing of inch helper posts as close to the track and air pipe as may be possible and then the removal of the old oid posts the muck etc is then cleared out about two feet below track level or until solid hot bot torn is reached wall forms are built close behind the helper posts leaving at least eighteen inches width of room for concrete outside them these wall forms are extended up to the top of the old caps arch ribs cut to a radius which will give one part raise to six feet of span between the walls are thrown across and braced on five rows of stringers running lengthwise above the caps the wall rooms are both poured full of concrete and then each side of the arch leaving above three feet in the center for an arch key when the concrete has haa set sufficiently to bear up evenly under the caps of the upper set except across the threefoot three foot key the center posts are chopped out the gap in the forms boarded over and the narrow keys driven in by the compressed air gun until the balance of the roof is solidly packed since the thrust of the arch is held by the ground on either side the concrete arch is under compression and needs no enforcement re for it can only breake break under sufficient weight to crack and pulverize thirty to forty eight inches of solid concrete the necessity of handling all concrete materials in the cramped space in the tunnel and keeping out of the way of even the small amount of traffic which goes on during the graveyard shift makes this arch work slow and inconvenient but it presents no particular difficulties the sand gravel and cement are dumped by a wheelbarrow into a bucket which is hoisted by a 1000 pound capacity bar hoist spilled into a hopper and drawn from it into the concrete or cement gun this gun is simply a right angle elbow reducing from fifteen inches down to a 5 inch discharge having a 2 inell inch air line cut in at the back of the elbow and facing into the 5 inch pipe line once the materials and water are inside the gun gull the top is closed the air turned on and the materials are kicked out into the pipe and lifted through it around the necessary turns tarns to the forms all the contents being mixed en ell route besides the writer the concrete crew of paul peterson carl carlson carison mgt andrew carlson carison bob shaw uric lyons and john hietala |