US2867171A - Mine blasts - Google Patents

Description

Jan 5, 1959 A. A. K; A. E. DEMELENNE 2,857,17

MINE BLAsTs Filed March 31, 1954 Jamal/l (l a 7 INVENTOR DML MINE BLASTS Anatole a. k. a. Edgard Demelenne, Mons,Belgium Application March 31, 1954, Serial No. 420,195

Claims priority, application Belgium April 10, 1953 2 Claims. (Cl. 102-22) This invention relates to 'blasting in mines, and more particularly concerns means whereby such blasting may be effected with greater security and in a simpler manner than heretofore, while at the same `time providing in addition for improved working conditions in the mines Where these blasts are effected.

In the Belgian Patent No. 515,939 dated December l, 1952, and the corresponding British application No. 33,187/53 dated November 30, 1953, both for: Improvements in means for opposing dust in workings, particularly in coal mines it is proposed to inject a liquid into the rock or the coal layers while making use of the detonation of an explosive to ensure the injection, using the explosive cartridges usually employed in mine blasts, but however only using those called safety cartridges where fire-damp is present or presumed to be present. The injection liquid may be any liquid in pure or mixed form, in solution or other state, particularly water.

It s known that in mine blasting, both in rocks and in coal, both in levels and cuttings, when the detonation of the explosive is effected in the presence of a quantity of a suitable liquid the inflammatory effect of the explosion on the fire-damp and the lire-damp mixtures is eliminated or at least considerably reduced.

It has been found that good results may be obtained by using water as the inammation inhibiting liquid.

However the action of the selected inhibiting liquid may be improved by the judicious addition of materials or substances having by themselves an inhibiting effect on the inflammation, as for example sodium chloride or calcium chloride which are knownto possess this property.

The preferred form under which the addition may be associated to the inhibiting liquid is in solution, but the additional materials or substances may be also simply mixed with, or suspended in the liquid.

According to the explosive used, the selected inhibiting liquid, the additive incorporated therein, and the precise result to be attained, the quantity of the liquid is proportioned.

In blastings, either effected in the usual manner or in the presence of a liquid as hereabove indicated and in this latter case whether the liquid is used for injection, or for mining operations, subsequently to the loading of the mine holes the entrance of said holes is closed by a tamping. In prior practice, such a tamping has been commonly made of clay or of solid particles more or less strongly rammed, but such a tamping may be formed also with advantage by means of a liquid charge.

The liquid of the charge serving as a tamping may also act, at least in part, for laying down the dust of the blast.

As liquid, use may be made of any non-inammable liquid and naturally of any inflammation inhibiting liquid, together with the addition of materials or substances having by themselves an inflammation inhibiting action, preferably in a soluble or dissolved form.

The quantity of liquid to be used may vary in accordance with the tamping to 'be made and the other conditions of blasting.

assaut Patented Jan. 6, 1959 Moreover, as the tampngliquid may intervene in the desired action-injection for the dust laying, or inhibition of the inammation in a mining operation, or the laying of the blast dust, or several of these aims simultaneously the quantity of liquid provided for the tamping may be modified accordingly.

In firing effected by means of tampings, a reduction in the quantity of dust formed has been noticed and also that the puff of fume resulting from the detonation was less opaque than in the case of the usual clay tamping. It is believed that this results from some absorption by the liquid of the detonation products.

Means may be provided for amplifying .the effects referred to, thus improving the conditions making for safety and health in the mines.

To this end there is yadded to the liquid forming the tamping a substance adapted to reduce the surface tension of said liquid, `or substances or products capable of increasing the agglomeration of the tine dust particles which are thus more easily and more rapidly laid down and thus become innocuous or less noxious.

Accordingly, the liquid used as tamping comprises materials or substances able to attenuate or suppress the toxicity of .the gases and fumes evolved by the explosion, in particular materials or substances which, by reaction with poisonous gases, such for example as CO, NO, NO2 or SO2, render the latter innocuous or less noxious.

Naturally these additional materials or substances arel so selected that from mutual reaction, no noxious or otherwise undesirable compounds' will result, especially compounds able to alter the inflammation inhibiting effect of the liquid against fire-damp.

The manner in which the presence of the inhibiting liquid is ensured at the moment the detonation takes place may vary, but it is convenient to arrange the inhibiting liquid in the form of portable charges.

Where the liquid charge is mainly intended to serve as a tamping, preferably this charge is a portable element.

Preferred embodiments of .the invention will now be described with reference to the annexed drawing, where- 1n:

Figs. l and 2 illustrate in plan View and end View, respectively, an enveloped liquid charge;

Figs. 3 and 4 illustrate in `plan View with parts broken away, and end view, respectively, a modified construction of enveloped liquid charge;

Figs. 5 to 7 illustrate Various arrangements of `blasting cartridges and liquid charges' in mine holes.

Referring to Figs. l and 2, in accordance with one embodiment, the liquid is introduced Within a shell 1 which is sealed or otherwise closed and the cross section `of which is made to conform to the mine hole, the constitutive material yof the shell being water-proof and not giving rise to llame firing in order to avoid combustion of portions of the shell that could last after the explosion, and, preferably, being flexible.

When the liquid charge is to perform an inhibiting function, naturally it kwill be desirable that the shell be easily ruptured by the explosion, and on the other hand tests have shown that no inconvenience or detrimental results are experienced should the material of the shell be ruptured by the explosion where the liquid batch serves as a tamping.

For forming the shell use is made of synthetic plastic material or synthetic resins answering the indicated requirements and moreover being suiciently stiff to enable the shell, even when made with thin walls to withstand the necessary handling without damage.

The sealing of the shell may able means such as associated closure members, sticking welding, and particularly autogenous Welding, as shown at in and 1b.

be effected by any'suit" Where the liquid is enclosed within a shell, and particularly a shell made of a pliable or flexible material, as aforesaid, and is used as a tamping there is associated therewith a means ofindicatingathe integrality of the shell, and conveniently apmeans adapted for visualv observation, this permitting the user to easily ascertain the effective presence of a tamping in a mine hole and the condition of the tamping at the moment the blast is effected. Y y

Particularly, spots or coverings such as those designated by 1c may be formed on theshell by means of a fluorescent or phosphorescent or light reflecting product or paint. Where the shell is made of transparent or translucent material, a phosphorescent or fluorescent substance may be incorporated in the liquid therein.

In both cases, instead of a single shell, the tamping may bev provided with la first shell 1 containing the liquid, which shell may be made of a more frangible material, for example a thin synthetic plastic material, and this first shell may be surrounded with a second shell 1d- Figs. 3 and 4-which may act as a protective shell and is then to be adapted for correctly vwithstanding the handling operations while, at suitable selected locations, the protective sell may be removed to uncover the first shell and thereby allow for the indicating means 1c associated with ythe rst shell 1 to be displayed.

For example, the protective shellf1d maybe made of metal, cardboard, or synthetic plastic material, and shaped in the form of atube open at the ends where it permits the ends of the iirst shell to be observed.

In the following there is indicated by way of examples, in what manners the invention may be carried into practice, as well as results of tests which have been effected.

Example 1.Referring to Figs. 5 to 7 and first to Figs. 5 and 6, whatever the purpose, for injection and, or for mining one may proceed as follows: in a mine hole 2 of suitable diameter, for example 40 mm., and appro priate length, there is introduced the cartridge or cartridges of explosive designated 3 and the usual firing devices ldesignated 4, and then a shell enclosed charge 1 of inhibiting liquid as above indicated. The entrance of the hole having preferably been closed by means of a suitable tamping 5, the blasting is effected, causing the shell to be ruptured and permitting the liquid to form the inammation inhibiting atmosphere.

The positions of the liquid charge and of the explosive cartridges in the mine hole could be reversed, as also liquid charges could be placed on either side of an ex plosive charge (Fig. 6), or liquid charges may be caused to alternate with explosive cartridges.

In this Way injection and inhibiting charges may be formed of different liquids and made separately, all such modifications being naturally within the limits of the invention.

In mining or dislocation, blastings, and even when {ire-damp may be present, high explosives may be'used with the well known resulting advantages of efficiency. Thus having in mind a blasting while using a high explosive with water as the inhibiting liquid, the quantity of liquid may be of from 100 to 200 cubic centimeters (cc.) for an explosive charge of about 100 grs., but in some cases a smaller quantity of liquid may be used.

Where the disturbance or dislocation of the rock andY an injection of liquid in the cracks are sought, the quantity of liquid will be normally higher and as high as possible, giving in any case the desired inhibiting effect; for example the quantity of liquid may be from 500 to 800 cc. or more for au explosive charge of about 100 grs. The following inammation inhibiting tests have been made:

' In an experimental chamber-gallery containing air with a content of 9.25% CH4, that is an eminently inammableatmosphere, by means of the proper conventional or classical arrangement and without tamping, two cartridges each containing grs. of a most disruptive dynamite, were caused to explode in the presence of 250-300 cc. water, enclosed within a tube having a diameter of 40 mm. and about 25V cm. length, without inammation of fire-damp mixture.

In a second test effected under the same conditions but with four cartridges each of 100 grs. of dynamite and in the presence of an enclosed charge of about 500 cc. of water, no inflammation of the fire-damp mixture has been experienced.

Example II.-In the boring of a level or gallery in hard schists inclined at 70 to the horizontal, having a normal cross section of 3.5 m. width at the base and 3 m. height, and comprising at about the middle of the height a coal layer having an opening of 0.6 m., upon removal of the layer on 1.2 rn. in front of the working face, four mine holes are bored in the bed of lesser thickness and lesser hardness of the wall of the layer and eight mine holes are bored in the bed of the roof.

All these holes were bored with 1.4 m. as length and a diameter of 40 mm.

A Four of the mine holes of the roof are then loaded as illustrated in Fig. 7 with 4 cartridges of dynamite 3 provided with an instantaneous fuse 4 and against thel explosive there is then pushed a tube 1 made of synthetic plastic material having a length of 40 cm. and a diameter of 35 mm., sealed at its ends and containing about 370 cubic centimeters of water. On firing, the mining of the rock takes place normally, the same as with the tamping of closely packed clay of 40 cm. length as commonly made.

1%.-All the remaining holes are then loaded in the same manner as above, but using a sheated explosive called Scurit-GrisouPoussire" in accordance with the Belgian mining regulation and provided with time fuses. Against the explosive there is then pushed in each hole a tube 1 of 40 crn. length and a diameter of 35 mm. filled with water as above. When the blasting is initiatedfthe mining occurs normally.

In each case it has been observed that the puff of fumeresulting from the detonation was less opaque than in the case of the usual clay tamping, which effect is believed to be due to some absorption of the detonation products by the liquid.

Fume absorption and dust laying Y Example lII.-In a tamping of which Wateris theV constituent, there is added a wetting agent in small proportion, for example of the order of 1% or less.

Various commercially available wetting products may be used and employed at the dose of 'about 0.1%, and good results have been obtained with a wetting product containing ethylene oxide as a base.

Example IV.-In a tamping of which water is the constituent, there is added oxides, for example Fe203, in a proportion of about 1%, or carbonatos, for example CaCO3 or Na2CO3, in a proportion of about 2%, these oxides or carbonates being preferably incorporated in the tamping liquid formed as a saline solution containing alkali chloride, for example at the dose of 5 to 10%. Preferably sodium chloride should be used, which has the advantage of'avoiding the irritation of the throat.

Example V.To the tamping liquid there is added together a wetting agent and products as in Example IV.

Example Vl.-To the tamping liquid there is added oxidising agents such, for example, as potassium permanga nate -KMnO4-, or hydrogen peroxide -HgOgin a proportion of about 1%.

Example VIL-To the tamping liquid there is added together a wetting agent and oxidising agents; or oxides o1" carbonates, particularly in the liquid formed as a saline solution, and Voxidising agents; or a mixture of wetting` agent, oxides or carbonates, particularly in the liquid formed as a saline solution, and oxidising agents.

It results from the tests eected by the applicant that the products and substances above indicated (Examples III-VII) do not at all aiTect the inflammation inhibiting eiect against the tire-damp.

Example VILL-A tube of 10 cm. in length, and a diameter of 40 mm., containing about 120 cubic centimeters of water to which are added agents and substances as above referred to, in the indicated proportions, and placed as a tamping in front of 4 cartridges each containing 100 grs. of dynamite, avoid the inammation in an atmosphere containing 9.5% of fire-damp.

The placing of a tamping formed of an enclosed liquid charge is Very easily effected and it will be appreciated that owing to the invention there is not only a saving of the substantial time necessary for preparing and eii'ecting the usual tamping of clay or other solid materials more or less strongly rammed, but the security against the tire-damp and dust, and the healthfulness of the workings are increased.

Moreover in case a charge has not exploded, such a tamping is readily available and may be easily withdrawn and the appropriate steps undertaken to cause the explosion of the charge, without necessity for attempts being made to explode the charge through sympathy, that is by arranging a further charge in the vicinity, as is done in the case with the clay tamping system.

I claim:

l. A safety device for use with a blasting cartridge coniprising in combination therewith a liquid-tight translucent material casing, a casing lling comprising a name extinguishing medium having luminous substances therein to permit the user to determine the presence of the device in a mine hole.

2. The .invention as set forth in claim 1 including a second casing, provided with at least one end opening, surrounding the said rst recited casing to act as a protective shell.

References Cited in the le of this patent UNITED STATES PATENTS 60,573 Shaffner Dec. 18, 232,640 Hallock Sept. 28, 1880 358,611 Heath et a1. Mar. 1, 1887 748,935 Durham Jan. 5, 1904 1,401,328 Erwin et a1. Dec. 27, 1921 1,776,770 Bleeker Sept. 30, 1930 FOREIGN PATENTS 9,763 Great Britain of 1909 127,232 Great Britain Jan. 20, 1919 763,844 France Feb. 19, 1934 515,939 Belgium Dec. 1, 1952

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