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To assist in lowering the great weight of the steel tubbing, it is provided with a water-tight bottom in which is a nozzle having a stop-cock by which a sufficient amount of water can be let into the tubbing to sink it gradually. The tubbing is thus floated in the shaft until it finally rests on the solid bed leveled to receive it. A special moss packing below the tubbing makes a watertight joint when the water is pumped out.

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FIG. 2

The Lippman system differs from the KindChaudron in that the shaft is bored the desired diameter at one operation by using the cutting tool shown in Fig. 2. The tools are made and the cutting teeth secured in a manner similar to that employed in the Kind-Chaudron system.

ENLARGING AND DEEPENING SHAFTS

Enlarging Shafts.-Shafts may be enlarged by extending one end or one side of the shaft, for then timbering already in place is made use of, the alinement of the shaft is maintained, excavating is done easily, and less readjust

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ment of hoisting sheaves, stops, etc., is necessary. In order not to interfere with the hoisting of coal, the widening operations are commonly carried on at night.

A method used for doing the work is shown in Fig. 1. Cleats a are nailed on the old lining and buntons b placed on them across the shaft; on these is laid a temporary platform on which the men work. The enlarging is begun on the surface and carried downwards, a section about 8 ft. high being taken out from each platform. The drillers work on the rock bench cd and load the waste directly into cars on the regular hoisting cage. The end ef is timbered and backed as in sinking a new shaft. The timber joints at the corners g and h are left undisturbed. Each alternate side timber is taken out for part of its length and a new timber dovetailed in between it and the timbers above and below, the parts being joined by a feather-edge joint. The dotted lines show the original position of the partitions and linings. These cannot be moved if mining operations are being carried on until the widening is completed for the depth of the shaft.

If both the length and breadth of the shaft are to be increased, mining operations must be suspended as the shaft will have to be entirely relined. Shafts have been enlarged and retimbered by filling them to the surface with cinders and ashes. The retimbering or enlarging begins at the surface, and the method, while costly, is often cheaper in the end than endeavoring to use one or more sides or ends of the old shaft.

FIG. 1

Deepening Shafts.-First Method.-A false bottom of heavy timbers is provided in the sump as a resting place for the cage, and sinking is begun on

the bottom of the sump. When the new seam is reached, a new sump is made, new guides are extended from the bottom upwards to meet the old guides, the false bottom is removed, and the cage ropes spliced, or new ones of sufficient length to allow the cages to hoist from the lower seam substituted for the old ropes. This method is often used where material is being hoisted during the day and sinking done at night. A small sinking cage is slung under the regular cage or a bucket is used instead, the material being hoisted to the old shaftbottom level and there taken back into the old workings and gobbed. The disadvantages of this method are that all the water from the old sump drains through the false bottom and down on the sinkers at their work, and there is always danger of materials falling down the shaft on the sinkers.

Second Method.-At a short distance from the shaft bottom and on a passageway that is not much used, a steep slope ab, Fig. 2, or small shaft is sunk, the depth of sinking depending on the amount of rock necessary to be left as a support under the old sump while the deepening proceeds. At the foot of the slope a level heading bc is first driven to the opposite face of the shaft; the roof of this heading is strongly timbered by setting the collars in hitches cut in the sides, before the work of excavating the shaft below is commenced. When this is done, the excavation is begun and carried down in exact line with the shaft above, the material being removed by a hoisting bucket, operated by a wind

FIG. 2

lass or temporary hoisting engine located at some point near the head of the slope. The turther operation of sinking, timbering, etc., is the same as that previously described. When the sinking is complete and the shaft timbered, the main sump s is drained and the two shafts connected by driving downwards from the bottom of the sump, or upwards from below from a strong temporary staging erected at c.

Third Method.-Fig. 3 shows the method of deepening a shaft while the upper part is in use, by opening only that portion of the shaft area not under the hoistway for a distance of 12 to 15 ft., and then widening it out the entire size of the main shaft. This leaves a roof of rock (pentice) that shields the men. When another lift has been sunk, the pentice is cut away and another started for the next drop. The hoisting is done by an underground engine or by a bucket and windlass.

The main hoisting engine may be used by setting out one of the cages and

passing the hoisting rope through a hole drilled through the pentice and attaching it to the sinking cage.

Upraising.-Shafts are sometimes driven from the bottom upwards as when two parallel seams are to be worked through the same opening. From the labor standpoint the process is much cheaper, as there is no hoisting to do. The material extracted is generally stowed in the old workings below, but sometimes when room is not available it is sent to the surface. Before commencing to drive upwards, a careful survey is made to establish the four corners of the shaft in the mine immediately under the surface location. Four iron pins are driven in the bottom to mark these corners. If necessary, posts or timber cribs are set to secure the roof around the place before blasting is begun. When the excavation has proceeded upwards 8 or 10 ft. in the roof, the bottom is cleaned up, the pins located, and the shaft tested for alinement by hanging plumb-bobs in each of the four corners. Timbering is then begun by first setting a heavy square frame f, Fig. 4, in the roof, resting on substantial posts and sills, as shown in the figure. The inside measurements of the frame must correspond to the size of the shaft in the clear when timbered. This frame is exactly located by means of the plumb-bobs hanging over the four points previously established, and is then firmly wedged in place. The timbering of the shaft is built up on this frame after the ordinary manner of shaft timbering.

The timbering is carried as close to the roof as practicable, and a partition is carried up dividing the shaft into two compartments. This partition may later be used in the opera

A heavy bulkhead is now constructed at the bottom of the shaft, and a chute arranged under the larger compartment h, by which the loose material excavated above and thrown into this compartment may drawn and loaded as required. To control the descent of the loose material in this compartment, a door is arranged at the foot of the chute. The compartment m serves the double purpose of a manway and airshaft, and for this purpose it is divided by a temporary partition.

A ladder is constructed in the manway, by which the workmen travel up and down.

In the operation of upraising, the workmen ascend the manway by the ladder and stand on a temporary plat

unusual to have a lower seam open in advance of development; a condition that is assumed to exist when the method shown in Fig. 4 is used.

SHAFT DRAINAGE AND PUMPING

Surface water is kept out of the shaft by banking around the shaft sills the clay and other material taken out during sinking. The water pumped or hoisted from the shaft is carried away in tight wooden troughs that lead in the direction in which the surface dips, and extend far enough from the shaft to prevent the water from returning. Water within a comparatively short dis

tance from the surface can be drained from the shaft by sinking a well or small shaft adjacent to the main shaft. During the sinking, a hole, or sump, is excavated at one end or in the center of the shaft somewhat in advance of the general work. The water is either bailed out of this hole and hoisted in buckets, or a sinking pump of special form is employed. These pumps may be hung by hooks from the timbering, at any point or simply hung by ropes, and may be hoisted and lowered as desired. Instead of a special sinking pump, a small horizontal pump of ordinary pattern is often set up on a temporary staging, which is moved downwards as the work advances. Either of these pumps is connected with the steam and water pipes in the manway by short lengths of wire-wound rubber hose.

FIG. 1

Water Rings.-To draw away the water made by the shaft, a notch is cut in the rock as shown in Fig. 1, or if the shaft is timbered water rings, or curb rings, are built in the lining as shown in Fig. 2. These catch the water running down the lining and conduct it to the corner of the shaft, from whence a pipe leads it to the sump at the bottom or to a lodgement or a coffer dam.

Coffer Dams.-A coffer dam is a section of solid lining designed to dam back water coming from a bed of water-bearing rock. Sufficient material is excavated from the water-bearing bed to allow a good cement backing to be inserted behind the shaft timbers. This excavation should be carried a short distance into the overlying and underlying impervious rock so as to form a water-tight joint. The space behind the timbers is filled with concrete either at the time they are placed or later through an opening left in them. The timber is often made much stronger and heavier at this point.

Lodgements, or Basins.-Lodgements, or basins, are openings from 6 to 8 ft. high, equal in width to the shaft, and driven, usually, from the end thereof. As they extend from 50 to 60 ft. back from the shaft they hold large quantities of water, which may be pumped thence to the surface instead of from the sump at the shaft bottom, thus effecting a large saving in power. They are commonly floored and lined with cement to prevent the water reaching lower levels through cracks in the rock. The mouth of the lodgement is closed with a timber, or concrete, dam, in which an opening large enough to admit a man is left. In the case of basins, no dam is necessary as it is made by excavating the floor of the lodgement to a sufficient depth to hold the water.

Sump. The shaft is carried far enough below the cage landing at the bottom to provide a catch basin, or sump, large enough to hold the water draining into it from the shaft and workings during 24 hr. The depth of the sump will be the height to which the suction end of the pump can draw water, say, 25 ft. at sea level. Where the mine makes much water, the area of the shaft is not sufficient to afford the required capacity, and the sump must either be extended at one end or a second sump, draining into the first, must be provided.

FIG. 2

At the foot of a slope, or at the landing at any lift, the entry is widened out to accommodate at least two tracks-one for the empty and the other for loaded cars. The empty track should be on the upper side of the entry, or that side nearer the floor of the seam, and the loaded track on that side of the entry nearer the roof of the seam.

Fig. 1 shows an arrangement of tracks often used. At a distance of 40 or 50 ft. above the entry, the slope is widened out to accommodate the branch leading into the entry loaded track. This branch descends with a gradually lessening inclination un

til nearly at the level of the entry it turns into the main loaded track. A short distance above the entry and below the switch b a hinged bridge d is placed, which, when lowered, forms a connecting platform or bridge by which the empty cars are taken off the slope. The empty track e is about 6 ft. higher than the loaded track 1, and is carried over it on a trestle.

The figure shows the plan A and profile B as arranged for a single slope, or one side only

of a slope taking coal from both sides. When coal is to be hoisted from this landing, the bridge is closed, the empty cars lowered in the slope run off over the bridge, the cars unhooked from the rope, and the hook and chain

FIG. 2

thrown down to the track below on which the loaded cars are standing; the loaded cars are then attached to the rope and hauled to the main track on the slope and hoisted. This plan can only be economically employed in a seam of moderate thickness that will not require the taking down of a large amount of the top. The cars can be handled on the landing by gravity.

Fig. 2 shows an excellent method of laying switches in either thick or thin seams where the pitch does not exceed 20°. When there is only one track in the slope and coal is to be hoisted from both sides, the same arrangement is used on each side; but to avoid complications, such as crossings, etc., it is better to locate one of the switches on the main track farther down the slope, as indicated by the dotted lines. The empty track e joins

the loaded track before it reaches the slope track s.

Fig. 3 shows a plan A and profile B of a switch used at the bottom of a slope. The figure shows one side only of the slope, the other side being similar. At the switch a there is a pair of spring latches set for the empty track e and which causes the empty cars coming down the slope to take this track. The empty cars pull the rope in to where it can be attached to the loaded cars, which are standing near the slope on the road l.

Fig. 4 shows a cross-section

of the slope landing shown in

a

FIG. 3 B

Fig. 3 when the empty track e is higher than the loaded track 1, so that both the loaded and empty cars can be handled by gravity.