MACHINERY FOR BORING ARTESIAN WELLS.

Press, Volume XII, Issue 1580, 29 November 1867, Page 3

MACHINERY FOR BORING ARTESIAN WELLS.

[From the " Engineer."]

The artesian wells at present sunk in the Paris basin of the tertiary formation range in size generally from about Sin. down to 2in. diameter, with a depth of about 330 ft. to 350 ft. The bore-hole is usually lined with copper, in order to make the wells water-tight and bring the water to the surface without loss. These works frequently present considerable difficulties in their execution, from the frequent changes in the nature of the soil passed through, and from the impediments that are so often encountered in driving the tubes through the beds of sand and clay. Borings of a much larger size are now in process of execution in Paris for the purpose of bringing to the surface a large supply of the artesian waters, whose existence has been proved by the well at Grenelle of 3-fin. diameter that was sunk in 1841, and the subsequent one of 2fin. diameter sunk at Passy in 1861. Each of these two artesian wells required six or seven years work for its completion. A large artesian well is now being constructed by M. Dru, at Buttreaux Cailles, for the supply of the city of Paris, which is intended to be carried down through the green sand to a depth of 2600 ft. or 2800 ft. The boring is at present 490 ft. deep, and its diameter is as large as 3ft. llin.

During the last two years and a-half the writer had also been sin king-in a similar well of Ift. 7in. diameter for supplying the sugar refinery of M. Say, in Paris. This well ia now 1570 ft. deep, and it is expected that the water-bearing strata will be reached at a depth of about 1800 ft. For the smaller wells hand-boring tools are in use, but these are limited to borings of inconsiderable depth and small diameter. For borings of the diameter of these large wells _it is necessary to make use of special tools, worked entirely by steam power; and in some cases of sinking mine shafts, took of as large a diameter as 14ft. 9in. Lave been used. The boring is effected % a rotary motion, ia the case of the Bma\l diameter, and for considerable depths percussive action alone is em- j ployed, raising the tool and letting it | fell with successive strokes.

M. Dru illustrated the apparatus he employed in boring the large wells that have been mentioned, by diagrams drawn to a scale*of one-thirtieth size. The boring-rod is suspended from the j outer end. of a working beam, which, is I made of timber hooped with iron, working upon a middle bearing, and is connected at the inner end to a vertical steam cylinder of lOin. diameter and 39in. stroke. The stroke of the boringrod is reduced to 22in., by the inner end of the beam being made longer than the outer end, serving as a partial counter-balance for the weight of the boring-rod,

The steam cylinder is single-acting, being used only to lift the boring-rod at each stroke, and the rod is lowered again by releasing the steam from the top side of the piston ; the stroke is limited by timber stops both below and above the end of the working beam.. A friction break is applied to the drum to regulate the rate of lowering the boring-rod. M. Dru went on to say that the boring tool is the part of most importance in the apparatus, and the one that baa involved most difficulty in maturing -its construction. The points to be aimed at in this are —simplicity of construction and repairs, the greatest force of blow possible for each unit of Btriking surface, and freedom from liability to get turned aside and choked. The tool used in small borings is a single;chisel, but for the large borings jt ia found best to divide the tool-face into separate chisels, each of convenient size and weight for forging, but keeping all the chisels in a straight line, whereby the extent of striking surface fc reduced, and the tool is rendered less liable to be turned aside by meeting a hard portion of flint on a single point of tbe striking edge, vtueh.'irould diminish the effect of the blow.

ft the whole length of the boringrod were allowed to fall suddenly to the bottom of a large bore-hole atl each stroke, frequent breakages would occur; and it is therefore found requijnte to. arrange for the tool to be detached from the boring-rod at a fixed P°iut in each stroke, and this has led to the general adoption of free-falling ™qlb. There have been several confauces for effecting this object, and & Bru described and illustrated his Pjan of self-acting free-falling tool. *pw tool consists of four principal pieces—a hook, a catch, a pawl, and a aisengaging-Eod. The hook has the chisels- fixed in its lower end, and Jhdes between two vertical edges of a ° x » WQ ich is screwed to the lower end ? the boring-rod, and the catch works ? j • Same s P ace u P otl a centre P" 1 jj*eo1 in a box, so that the tool is lifted J? t]le rod when hooked on the catch. &8 pawl at the same time being oppose the tail end of the catch, secures " jrom getting unhooked from the °°1; hut this pawl is centered in a sliding hoop, forming the top the disengaging rod, which slides weely Up and dovyn w } tn i n a nxea fiance upon the boriug-rod, being J r f? ed °7 two guides outside the box the boring-rod, and the hoop rests pou the upper one of these guides. «• lowering the boring-rod the disen-Pging-rod reaches the bottom of the «ore-hole first, and then being stopped PcSTenta the pawl from descending any

lower, and causes the inclined back of the catch to slide down past the pawl, forcing tlie catch out of the hook, aud thus allowing the tool to fall freely and strike its blow : and this height of fall of the tool will always be the same, !>eing determined only by the length of the diseugaging-rod.

As the boring-rod continues to be lowered to the bottom of the hole the catch fails back into its original po?i!ion, and engages with the hook ready for lifting the tool in the next stroke.

The boring-rods employed are of two kinds, wrought-iron and wood. The wood for the rods requires to be carefully selected, and care has to be taken to choose the timber from the thick part of the tree, and not the toppings ; and in France Lorraine or Vosges deals are preferred.

The boring-rods, whether of wood or iron, are screwed together either by solid sockets or with separate collars. The boring-rod is guided iv the lower part of the larger diameter of the hole by a lantern, consisting of four vertical iron bars curved in at both ends, where they are secured by movable sockets upon the boring-rods, and fixed by a nut at the top ; these bars admit of being readily adjusted to any required diameter. In raising up or letting clown the boriug-rod two lengths of about thirty feet each are detached or added at once, and a few shorter rods of different lengths are used to make up the exact length required. The coupling screw by which the boringrod is connected to the working beam serves to complete the adjustment of length ; this is turned by a cross-bar, and then secured by a cross pin through the screw.

In ordinary work breakages of the boring-rod generally take place in the iron, aud more particularly at the part screwed, as tliat is the weakest part. In the case of breakages of the rods occurring, the tools usually employed for picking up the broken ends are in a conical screwed socket and a claw. Tools with nippers are sometimes used in large borings, as it is not advisable to subject the rods to a twist.

In boring through chalk, as in the ease of the wells in the Paris basin, M. Dru stated that the hole is first made of about half the final diameter for 60ft. to 90ft. depth, and it is then enlarged to the full diameter by using a larger tool. This is done for convenience of working, for if the whole area were acted upon at once it would involve crushing all the flints in the chalk ; but •by putting a scoop in the advance hole, the flints that are detached by the blows of the tool are received there without getting broken during the working of the second larger tool When the boring tool has detached, a sufficient quantity of material the boring-rod is drawn up by means of the <Jrum and rope worked by the steam engine ; a scoop is then lowered into the bore-hole by a wire rope from another drum, and the scoop is then drawn up again with the excavated material. This scoop consists of a rivited iron cylinder, with a handle at the top that can either be screwed to the boring-rod or attached to the wire rope ; and the bottom is closed by a large valve opening inwards. On lowering this cylinder to the bottom of the bore-hole the valve opens, and the loose material enters the cylinder, where it is retained by the closing of the valve, whilst the cylinder is drawn up to the surface. The resistance experienced in boring through different strata is very various, and some rocks passed through are so hard that with 1200 blows per day of theboringtool, weighing nearly lOcwt., with 19in. height of fall, the bore-hole was advanced only 3in. to 4in. per day.

As the opposite case, strata of running sand have been met with so wet that a slight movement of the rod at the bottom of the hole was sufficient to make the sand rise 30ft. to 40ft. in fie bore-hole. In these cases the writer has adopted the Chinese method of effecting a speedy clearance, by means of a scoop closed by a large ball clack at the bottom, and suspended by a rope, to which a vertical movement is given; and each time the scoop falls upon the sand a portion of this is forced up into the scoop and retained there by the ball valve.

M. Dru concluded his interesting paper by pointing out that an artesian well is always some time in settling down to its permanent working state, and when the water first reaches the surface it undergoes considerable fluctuations, being charged from time to time with the substances at the bottom of the bore-hole. The velocity of the flow of water from the artesian wells varies considerably, and the following are some examples of the delivery at the surface by those already completed in the Paris basin: —

Velocity of Diameter of Gallons discharge, bore-hole, delivered Feet per Inches, perminute minute. St. Denis ... 288 29 161 Eldeuf ... 2 95 66 222 Stains ... 2 95 176 593 Grenelle ... 374 84 6yß Borings of large diameter for mines or other shafts are also sunk by means of the same description of boring tools, only considerably increased in size, extending up to as much as 14ft diameter. The well is then lined with cast iron or wrought iron tubing, for the purpose of making it watertight; and a special contrivance has been adopted for making a watertight joint between the tubing and the bottom of the well, or with "another portion of tubing previously lowered down. This is done by a stuffing-box, which contains a packing of moss. The upper portion of the tubing is drawn down to the lower portion by the tightening screws, so as to compress the moss packing when the weight is not sufficient for the purpose. A space is left between the tubing and the side of the well to admit of the passage of the stuffingbox flange, and also for running iv concrete for the completion of the operation. The joint is thus simply made by pressing out the moss packing against the sides of the well; and this material, being easily compressible and not liable to decay under water, is found to make a very satisfactory and durable joint.