US3113518A - Container for explosive materials - Google Patents

Description

Dec. 10, 1963 H. D. DoAN CONTAINER FOR ExPLosIvE MATERIALS Filed Aug. l1, 1960 Sappor/memer for o/a//ng bag appar/member- /bfhok/ing bay M//v//e ffl/ing are /vo/e F/Lssure Free- R. ma. WD ,n 6 fm e H dw e. fm wo c e .u r Ww /r w /06 .m www F 0/ A65/vr United States Patent O 3,113,518 CNTAR FOR EXPLOSIVE MATERIALS Herbert 1). Doau, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Aug. 11, 1960, Ser. No. 49,016 1 Claim. (Cl. 102-24) This invention relates to explosives and more particularly is concerned with a tube-like device for charging and containing an explosive in a bore hole and a method for its use. i Bore holes, i.e. blast holes, for quarry, open pit mining or construction are prepared by drilling or rock piercing to a desired depth in a preselected stratum. Many times these holes as prepared have sharp edged rocks around their diameter. Also, these blast holes cut across fissures in the various strata and are subjected to the action of both relatively fast and slow flowing seepage water entrapped in the ground.

Economical blasting on a commercial scale favors the use of free-owing or bulk-type explosives for use in such types of operation. However, when bulk explosives, as for example, bulk ammonia dynamites, ammonium nitrate-fuel oil, ammonium nitrate-light metal-ammonia, ammonium nitrate-light metal-water and ammonium nitrate-light metal-aqueous ammonia are placed in bore holes containing iissures and/or water, reduced effectiveness, loss of the explosive material, actual hole misires, and poor distribution of the explosive in the bore hole can result. Historically, tubing of thin-walled polyethylene, or polyethylene reinforced with fibers has been used to contain bulk explosives in such bore holes. However, this material has low puncture and rupture strength even when used in fairly thick walled form which results in holes, punctures and outright rips in the tubing as it is inserted into the bore hole or as the particulated freeflowing explosive is placed therein. Such openings in the tube result many times in explosive loss and water dilution, in quenching of the load thereby causing the misfires of the load upon detonation and in expensive hole redrilling.

It is the principal object of the present invention to provide a container for bulk explosives that has a high degree of resistance to puncture, rupture, and tear.

It is a further object of the present invention to provide a tubular encasement for containing bulk explosives whereby a certainty of maintaining these explosives in a preselected and predetermined condition in a water-lilled or iissured bore hole can be maintained.

It is another object of the present invention to provide a thin-walled, commercially acceptable casing for explosives which gives an unexpected improvement over those materials currently used for such casing.

It is a further object of the present invention to provide a tubular encasement for bulk explosives which is iiexible, impervious to water and similar fluids, expandable and which when lled with explosive in a bore hole will conform with the wall of the bore hole and act as a lining for the bore hole but which will be highly resistant to tear and rupture upon contact with jagged or sharp rock edges as may be present along the length of the wall of said bore hole.

Other objects and advantages will be apparent from the detailed description presented hereinafter and by reference to the accompanying drawings.

The device of the present invention which gives these unexpected results is a container or a bore hole lining prepared from a mixture of high density polyethylene and polyisobutylene which when utilized to contain bulk explosive materials in a bore hole maintains these materials in a predetermined condition with a high degree of icc.

certainty even though the bore hole be tissured or water lled. The drawings accompanying this specification show the device of the instant invention both in unlled (FIGURE l), partialy filled (FIGURE 2), and lilled, armed and stemmed (FIGURE 3) stages positioned in a ssured bore hole.

The explosive containing device of the instant invention will be substantially tubular in shape and will be prepared from a mixture of high density polyethylene and polyisobutylene. The actual plastic mix composition preferred for blending and forming into the tube-like member having the desired unexpected Vhigh resistance to rupture, tear and burst strength when encompassing such explosive loads will be about 70 percent by weight of high density polyethylene and about 30 percent by Weight of polyisobutylene. Compositions ranging both higher and lower in polyisobutylene can be utilized. However, if the polyisobutylene content of the composition is increased to any great extent much above 35 percent the resulting tubular member becomes somewhat sticky in feel. If the amount of polyisobutylene is reduced much below that composition which is shown, the tubular member loses the unexpected and desired high resistance to rupture, burst and tear needed in this application.

The tubular member itself can have a wall thickness of varying dimensions wherein this thickness can range from about 0.001 inch to about 0.10 inch or more, but highly satisfactory rupture and tear resistance and burst strengths have been found with use of an economical, commercially available tube having a nominal wall thickness of about 0.006 inch.

The explosive container can be made bag-like in shape with a closed or sealed bottom and of such a length to insure complete filling of a bore hole. Alternatively, for ease of utility, the tubing can be supplied in a continuous long roll. Predetermined lengths of this tubing, as desired can then be taken or cut oii from the end ofthe roll, one end of this so removed length can then be sealed oi, as by tying a knot therein and this end of the resulting bag-like container then be placed into the bottom of the bore hole.

In order to achieve effective loading of a given bore hole the diameter of the tubing to be utilized will be substantially the same as or even a little bit larger than the diameter of a given bore hole being iilled.

The following examples will serve to further illustrate the effectiveness of the tubular member of the instant invention but is not meant to limit the invention thereto.

Four 10-inch diameter blast holes about 35 feet deep were drilled in taconite. These holes as pierced into the rock were somewhat irregular in diameter with rough and sharp edges of rock being evident around the wall of each hole down throughout its length. Shortly after drilling,

additionally each of the holes became substantially lilled i with ground Water which seeped into the opening from fissures in the various strata of the rock. A bag was prepared by taking lengths of a single thickness of nominal 0.006 inch wall thickness high density polyethylene-polyisobutylene lll-inch diameter tubular film (blend containing about 70 percent by weight of the polyethylene and about 30 percent by weight polyisobutylene) from a roll of the material and knotting the bottom of this length. A small amount of a 50-50 weight percent mixture of coarse aluminum and magnesium metal chips was placed into the bottom of the bag, and after weighting the bag, it was placed in the bore hole. Additional amounts of the coarse, jagged edged metal chips were poured into the bag until it iilled about 15 feet of the bore hole. The metal then was flooded with an ammoniacal solution of ammonium nitrate containing about 4-6 percent water, 25 to about 35 percent ammonia, balance ammonium nitrate. This action forced the wall of the bag into intimate contact with the rock of the bore hole Wall. The resulting explosive composition itself contained about 40 percent by weight of the metal and about 60 percent by weight of the solution and was designed so that for highest elective explosive results excess water Was to be excluded therefrom.

After the explosive composition had been prepared in the plastic bag which had been inserted into the bore hole, the load was watched for evidence of bubbling and frothing and mix reactivity, this being an indication that foreign water would have leaked into the explosive load from the bore hole. This was not evidenced. Furthermore, no leakage from the container into the rock formation had occurred since the predetermined liquid levels in the holes as obtained with calculated quantities of solution did not recede as would have been the case had undesirable leaking of the mix from the plastic bag occurred.

Each of the holes was then armed with a conventional detonator, stemmed and fired. The explosive loads in all four holes detonated with good eficiency and showed a reliability of explosive blast of about 100 percent.

In a comparative set of four holes, inch diameter bags of the single ply and having a wall thickness nominally of about 0.006 inch of polyethylene (not containing polyisobutylene) lm were prepared as described above, these placed in the bore holes and loaded with a metallized mix of the same composition as used above.

As the ammonium nitrate solution was added to the metal-containing bags the material in one of the four blast holes immediately commenced a violent reaction, indicating the presence of unwanted water which apparently had leaked through punctures in the polyethylene. The linings in the remaining three holes obviously had ruptured, for solution in amounts exceeding four times the predetermined quantities as poured into each of the linings in the bore holes Without producing the desired liquid level within the bore hole.

Armng, stemming and firing these latter four holes in the manner as was described above for the first set, because of water contamination and solution leakage from the punctured and ruptured polyethylene bags gave a blast reliability of only about 25 percent.

This device is also useful with other bulk explosives such as TNT, free flowing dynamites, prilled ammonium nitrate plus 6 percent fuel oil, ammoniacal ammonium nitrate solutions used with from 20 to about 60 percent by weight light metal such as magnesium, aluminum and alloys and mixtures thereof.

Various modifications can be made in the device and method of the present invention without departing from the spirit or scope thereof for it is understood that I limit myself only as defined in the appended claim.

I claim:

An explosive device which comprises in combination a bore hole, a lining for said bore hole, and a free-lowing bulk explosive, said lining being a bag-like tubular member prepared from a mixture of about 70 percent high density polyethylene and about 30 percent polyisobutylene, and having a diameter about the same as that of said bore hole and a nominal wall thickness of about 0.006 inch, said bag-like lining being at least as long as said bore hole, said explosive comprising on a weight basis from about 20 to about 60 percent of a mixture of magnesium and aluminum chips percent magnesium and 50 percent aluminum on a weight basis) and from about 80 to about 40 Weight percent of an ammoniacal solution of ammonium nitrate, said solution containing about percent ammonium nitrate, said explosive being placed inside said bag-like lining and forcing the Wall of said lining into intimate contact with the wall of the bore hole.

References Cited in the le of this patent UNITED STATES PATENTS 2,168,030 Holmes Aug. 1, 1939 2,369,471 Latham Feb. 13, 1945 2,393,594 Davis Jan. 29, 1946 2,468,165 Brister et al Apr. 26, 1949 2,879,149 Brown Mar. 24, 1959 2,903,969 Kolbe Sept. 15, 1959 2,954,284 Toulmin Sept. 27, 1960

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