Show chute types 1 in n metal mi mines nes BY CHARLES A MITRE R chutes chute s are used principally for passing ore and waste to different levels in a mine they are also used for storage and frequently quent ly when not necessary for ore or waste are kept open entirely for ventilation in general chutes are feet high the usual distance between levels some exceptional chutes are much longer while others are shorter than this figure when a raise is driven it is customarily divided into two compartments one for the manway and timber way and the other the chute for the passage of ore or waste the various types of raises which are commonly used are as follows two compartment raises one for chute and the other for men and timber six post square set raise generally used in square set in medium ground four post aquara set raise occasionally used in caving methods this raise is similar to the six post raise with the exception that the compartments are much smaller crib raise used in square set top slice cut and fill and shrinkage in heavy or broken ground raw chute usually oblong in shape about 4 feet x 7 feet with no timber except a partition between the chute and manway used only in hard ground mined by cut and fill shrinkage and to some extent by caving methods one compartment raises chute only four post raise used us ed in caving methods in medium ground crib raise used in heavy ground mined by caving methods in rare cases angle mining engineer Engl neer phelps dodge corporation bisbee ariz in paper delivered before the eighth annual safety council 0 iron is used in its construction to prevent excessive wear raw chute or finger raise circular about 3 feet in diameter no timber employed in its construction used only in medium or fairly hard ground rock built chute constructed in the shape of a well generally about 6 feet in ft diameter this class of chute is built in loose ground concrete chute for heavy ground usually circular used where there is a great deal of wear in a chute requisites for a standard chute the requisites for a standard chute are safety in location and operation efficiency in handling ore and waste economical construction and upkeep safety ety formerly chutes were located in the center of drifts so as to facilitate the dumping arrangements and permit the use of end e dump cars while this was a great convenience it car c from the haulage point of view of inell le ried fied with it the constant danger to be falling into the chute boards were laid over these openings and to be removed remo when cars were dumped freau antly 1 ever miners would forget to replace t when the cars were empty and many a dinall 0 op ope euille has lost his life by falling into inta an this P of this character in some states state s tice is now prohibited the law the si side that the chute shall come up at stead of in the center of the drift chute the manway adjacent to a the should be located far enough from froin lip g haulage track so that the men di not step s and down the will erectly in front of a moving train d one of the principal things to te be edis ed is the hanging up of a chute it is usually a dangerous procedure for a runner to bring down a chute which has been choked or hung up should this occur some distance up for instance 80 to feet it may cause an air blast which would break the chute and injure the trammer clearance for cars the chute mouth should be high enough so that a man will not have his fingers caught between chute and car this is very difficult at present as there are mines where five different kinds and sizes of cars are used all being loaded from the same chute such a diversity in sizes of cars naturally results in insufficient clearance for the larger ones and too great a clearance for the small cars this latter condition in itself creates a danger as when small cars are used the ore dropping from a distance at high speed may injure the runner especially when the car is about full and it is necessary for him to close the chute gate immediately trolley wire tn in all average drifts having electric haulage the trolley wire is immediately above the mouth of the chute the larger drifts have the advantage of an extra set above the trolley wire upon which the chute runner works there being a flooring between him and the wire thus preventing his coming in contact with the electric current some provision must always be made in the smaller drifts to protect the runner from the trolley wire in some instances the live wire is insulated and carried along the opposite side of the drift the overhead wire being dead tor for a distance of about ten feet and acting merely as a guide for the trolley wheel in other cases the overhead live wire is boxed in with boards on the sides and has a hinged door beneath which cabbe can be pulled up and hooked in this way completely isolating the trolley wire another practice is to have a switch near the chute so that the current in this section of the wire can be turned off and on at will in exceptional cases the trolley wire is cut about five feet on each side of the chute mouth and may be detached and moved away bodily this however involves considerable sid erable trouble clearance for chute runner A A bypass by pass is frequently made by taking out a half set of ground immediately opposite site the chute and a bench Is provided upon which the runner stands this should be high enough to enable him to reach across and tap the chute and also to use a picky poke to advantage in loosening the large boulders which frequently clog up the mouth the bypass by pass is a great safety provision in that it gives the operator an opportunity port unity to step out of the way in case there is an unexpected rush of ore out of the chute in caving methods where there are lines of chutes on both sides of the drift a bypass by pass is impossible and the runner must load his cars by standing at the side of the particular chute which he is drawing eff efficiency ici ency it is important that all chutes be properly located with respect to the levels above and beneath the through which they pass upon the location of the chute depends the convenience of the arrangement ran gement as well as the distance A chute should be adapted to the peculiar needs of the ore body in question in certain classes of ore large chutes are necessary while in others smaller ones may be used to advantage in some cases a great many thousand tons of ore must pass through before the chute is finally abandoned and the tonnage grades down from this to but a few tons in other cases consequently the construction of the chute in the first instance must be stronger more lasting and naturally more expensive than the type of chute which would do in the second place the construction of a chute should also be such that the ore will now flow readily into the cars one of the difficulties with chutes that has not yet been overcome is the fact that all ore has a tendency to hang up or stick in the chute A suggestion which has been made and tried out is to have a breaker staggered on each set right down the chute the ore on being dumped into the chute on the level above strikes the first breaker and is thrown across onto the breaker on the other side and from there zig down the entire length without stopping until it gets near the chute mouth these breakers impede the progress of the ore and prevent it from packing solid in the bottom of the chute naturally the chute is less liable to hang up very good results were obtained from a trial of this chute the only objection being the extra cost of construction in placing the breakers on the sides the inclination of the chute mouth has a great deal to do with its efficient operation as certain classes of ore run much more readily than others the character of the ore therefore must be taken into account before adopting a standard chute and mouth economy the cost of constructing chutes should be kept at a minimum it would be a waste of money to have a chute constructed to last far longer than the life of the while on the other hand it would also be poor economy to have a chute so lightly constructed that it will need constant repairs long before that section of the has been abandoned formerly chutes were made having a wooden bottom and the ore taken out immediately beneath the chute mouth As a consequence the ore dropping down the chute soon wore out the bottom and then filled in the sides of the drift As a matter of fact this is still practiced in a number of districts even though it involves an unnecessary expense to the company for upkeep and repairs repairs this practice is obsolete in the most up to date mines wherever possible the bottom of the chute should be in solid ore or rock so as to decrease the cost of upkeep as ore striking on a wooden bottom would soon cut through when the size and character of the chute with due reference to the class of ore has been worked out and decided upon it is then economical to have the timbers selected and cut to measure on surface so that the total number of pieces necessary for its construction can be sent down at any time and the chute mouth installed without any additional cutting underground |