| Show THE SLASH SYSTEM OP OF MINING G claude T rice in engineering and mining couf journal nal this system of M mining is a modification of both the square set system and the caving system which is being employed at the jordan and the telegraph mines of the united states mining company at bingham utah it has been in use there for several years and has proved quite satisfactory like other methods it has its advantages and disadvantages but its cardinal point is that it is a very safe method of mining in heavy it is an underhand square set method in which the overburden is allowed to follow down after the caved timbers the ground at the united states mines is heavy and the are large the wall rock is limestone in which a soft sulphide ore has been deposited by replacement A raise is put up to the top of the then the top slash is mined out by means of square sets the posts being planted on the ground with braces or spreaders between them at the bottom the set is lagged and a floor is also laid when the sets have been pushed to the boundaries and the ore on that floor or slash has been mined out holes are bored into the posts and loaded with dynamite they are then blasted and the overburden caved down upon the floor in case the ground becomes too heavy the floors can be mined in sections and each section caved as soon as the ore in that section is mined out the miners then drop down a set in the raise and begin to mine out another floor or slash the floor of the slash above is caught up by the square sets and so the waste is kept from mixing with the ore this slash or floor or of ore is mined out as before a floor of two inch plank lagging being laid as the mining progresses this slash is caved and tho the process repeated in the slash below the timbers used in these mines are inch oregon pine the posts are 7 feet 7 feet 4 inches or 7 feet 8 inches long the caps are 5 feet 4 inches long as are also the girts so that the caps and girts are placed at 5 foot centers no timber is recovered and no back of ore I 1 is caved the advantages es of this method are that all the ore is recovered that smaller timbers can be used and that the method is safe for the miners the disadvantages are that a bottom of ore must be taken out on each floor it is like continually mining on a sill floor except that sill timbers are not laid As a result the cost of breaking the ore is high raises must L be driven in the solid rock instead of carried up in the sets as in the case of ordinary square set mining moreover the are very hot and the air poor because there are no raises to levels I 1 above to promote ven ventilation ti lation the decay of tse the timbers which follow down with the caved ov overburden er burden soon fouls what little air gets up into the the crushing of the caved overburden and the timbers also aids in in making the air hot this system could be easily converted into a regular caving system by caving a back of ore each slice but on account of the value of the ore and the consequent loss of some of it entailed by the caving system this is not attempted at the united states mines As with any system it is simply that method which is cheapest considering everything coming into the problem |
