WO1996029567A1

WO1996029567A1 - Method and arrangement for supplying reinforcing charges to boreholes

Info

Publication number: WO1996029567A1
Application number: PCT/SE1996/000341
Authority: WO
Inventors: Hans Wallin; Pekka Eriksson
Original assignee: Bofors Liab Ab
Priority date: 1995-03-23
Filing date: 1996-03-19
Publication date: 1996-09-26
Also published as: SE9501035D0; SE504200C2; SE9501035L

Abstract

The present invention relates to a method and an arrangement for, in association with blasting works, guiding of initiating and/or reinforcing charges (5, 12) consisting of solid explosive into the desired position in such boreholes (2) as are subsequently to be charged with pumpable bulk explosive. According to the invention, use is made of the pump hose (1) with which the bulk explosive is to be supplied in order to guide the solid explosive charges into the desired position in the boreholes (2). The invention therefore means that the charging hose, in addition to its ordinary function, is also to be used instead of and as charging rod.

Description

METHOD AMD .ARRANGEMENT FOR SUPPLYING REINFORCING CHARGES TO BOREHOLES

The present invention relates to a method and an arrangement for, in the charging of chiefly elongate boreholes for blasting with pumpable slurry, solid or pulverulent so-called bulk explosives supplemented with solid reinforcing and/or initiating charges, supplying these solid charging units to the correct position in the boreholeβ.

The so-called bulk explosives are used generally in the majority of all large-scale civil blasting works such as in mining, in tunnel driving and in other major groundworks since they are cheap and easy to handle. Their low sensitivity to mechanical influence is in this case also a clear advantage. Bulk explosives are pumpable and/or ejector-transportable products containing two or more components which as a rule are brought together and mixed only at or close to the blasting site in association with the charging of the boreholes being prepared. For initiating bulk explosives, it is solid initiating charges which are required, in view of their low sensitivity. The effect achieved in the form of blasted and split rock can furthermore be increased to a great extent if the bulk explosive is supplemented with solid reinforcing charges of more piercing explosives. Both the initiating and the reinforcing charges are as a rule to be arranged close to the inner or lower end of the boreholes which means that they must be guided into place before the bulk explosive is supplied to the boreholes.

Recently, access to suitable reinforcing charges manufactured from high-energy explosives preserved from scrapped so-called discarded military ammunition has increased, as a result of which it has been possible to obtain such charges at an advantageous price which has considerably increased the interest in these reinforcing charges since it has been possible with the aid of these to increase the explosive effect to a very great extent. This supplement has proved especially valuable when there is a requirement to have rock masses blasted directly into suitable easily loadable pieces, i.e. obtain a suitable lump yield.

Previously, when use was made of the combination of solid unit charges for initiating and reinforcing the explosive effect obtained and of bulk explosives, the solid charges were as a rule lowered in separate lines or sometimes in their own ignition cables in order subsequently, as soon as it was confirmed that these charges had reached the intended position, to pump down the bulk explosive. In the case of laterally or upwardly directed boreholes, the old charging rod was correspondingly used, with which the solid charges were pushed into place.

According to the present invention, use is now instead made of the pump hose with which the bulk explosive is supplied in order to guide the initiating and reinforcing charges down to the bottom of the boreholes or alternatively in to their innermost end.

The connection between the nozzle of the pump hose and the explosive unit, i.e. the initiating or reinforcing charge, is in this case preferably to be dimensioned in such a manner that it is more than well able to hold the explosive unit, but that on the other hand it is released when the bulk explosive begins to be pressed out of the nozzle. This is achieved most simply by the nozzle of the pump hose being pressed firmly into an empty space adapted to it in the explosive unit or alternatively by the explosive unit being presβed firmly into the mouth of the nozzle. In its most simple variants, the friction between the parts and any slight deformation of one or both can then ensure that these hold together while the bulk explosive pumped out through the nozzle can act on the end wall of the explosive unit facing the opening of the nozzle in the direction of detachment. This type of operation can. be obtained with a number of different purely construetionally very simple forms of the respective nozzle -and the explosive unit. The holding together of the parts can also be supplemented by any more simple type of conventional catch.

Such a catch can be formed directly in the outer tube of the explosive unit or alternatively in the hose nozzle while a corresponding part can have a locking roll or the like which the catch slips over when the bulk explosive is pressed out through the nozzle.

A large number of other mechanically very simple variants are also possible. In the attached drawings, therefore, only some variants are indicated while the invention as a whole is defined in the subsequent patent claims.

Figures 1 and 4 show longitudinal sections through two different variants of arrangements according to the invention, while Figures 2 and 3 show the cross- sections II-II and III-III in Fig. 1 respectively. Furthermore,

Fig. 5 shows the cross-section according to line V-V in Fig. 4 while Fig.6 shows on larger scale a variant of the circled details in Fig. 4. Finally, Fig.7 shows a variant of the arrangement according to Fig. 1 which can be used even when the charge has a considerably greater diamater than the charging hose.

The arrangement shown in Fig. 1 consists of a nozzle 1 applied to or -quite simply consisting of the outer end of a hose with which bulk explosives are to be guided down into the borehole 2 in which the arrangement is already situated.

The nozzle/charging hose 1 is with its free outer end 3 guided down into the empty end 5a of the protection tube 5 which is otherwise filled with high-energy explosive 4. Cast firmly into the explosive 4 in the protection tube 5 are two thinner plastic tubes 6 and 7 of which the tube 6 extends along the inside of the tube 5 and a short way outside the upper mouth thereof. The tube 6 forms there a continuous duct 8. The tube 7 is in turn arranged parallel to the tube 6 but closer to the central axis of the explosive charge 4. At the bottom of the tube 5, there is another space 5b which is empty of explosive and through which the interiors 8 and 9 of the two tubes 6 and 7 respectively are interconnected. As can be seen from the figure, an ignition cable, fuse or equivalent 10 is guided down through the tube 7, bent in the space 5b and then, with the aid of an explosive cartridge 11 connected thereto and pushed into the space 9, locked against extraction. By means of this bending over, the ignition cable 10 is fixed in the charge and the ignition cable 10 can therefore be used in order to offer resistance e.g. when the charge 5 is to be lowered into a downwardly running borehole. As can be seen from Fig. 1 and Fig. 2, the tube

5 is also provided with an upper space 5a empty of explosive -and the nozzle 1 is now pressed down into this space. The tube 6 which is at least slightly elastically deformable extends well past this empty space and as the nozzle 1 is relatively rigid it is the tube 6 which is deformed as the nozzle 1 is wider than the space which is available in the tube part 5a between the inside of the tube 5 and the outside of the tube 6. By these means, a sort of resilient press fit is achieved between the nozzle and the charge 4-5. This means that the relatively stiff hose for supply of bulk explosive can be used directly as charging rod when the charge 4-5 is introduced into its predetermined place in the borehole. As soon as it is certain that the charge has reached its intended place, the supply of bulk explosive through the hose can be started. When the bulk explosive, which is viscous but pumpable, reaches the upper surface of the charge 4, the nozzle 1 is pressed free from its grip in the tube part 5a. If the charge is to be guided down into a deep borehole and it is uncertain whether the friction between the nozzle 1 and the tubes 5 and 6 is adequate in order to hold the charge, the ignition cable 6 can then be used as a counterholder. As a result of the fact that this lies in a bend between the tubes 6 and 7, it cannot of course slide out of its locked position.

In the arrangement shown in Figs 4 and 5 in a corresponding manner, the nozzle 1 has been guided down into an upper empty space 12a in a protection tube 12 which is in turn filled with the same explosive 4 as in Fig. 1. In this variant, there is only one thinner plastic tube 13 cast firmly into the explosive 4. .An explosive cartridge or detonator 11 has been guided down into the interior 14 of the tube 13. This is joined to an ignition cable 6 in the same manner as in the previous figure.

Press fits between the nozzle 1 and the protection tube 12 have been solved in this variant in such a manner that a part of the tube wall in the space 12 has been slit open along two parallel cuts 15, 16 which each cover only a part of the circumference of the tube wall 12, whereupon the tube wall part 12b between them has been pressed in in the manner which can be seen in Fig. 2c, at the same time as the ignition cable 6 has there been drawn between the inside of the tube 12 and the outside of the tube wall part 12b. At the same time as the ignition cable is in this manner fixed in the tube 12, it also ensures that the part 12b maintains its shape. Otherwise, everything functions as in the preceding example, i.e. the hose 1 is used as charging rod, the ignition cable 6 can be used as a counterholder and the pumping in of the bulk explosive ensures the uncoupling between the various parts. In Fig. 6, a variant is shown in which the tube wall part 12b, in this case numbered 12b' , has been made to engage in a locking notch 1' which has been made in the nozzle 1 just beyond the mouth thereof. The operation is the same but the holding between the parts is made somewhat stronger by means of this locking function.

In the variant shown in Fig. 7, the charge 17 has a considerably greater diameter than the charging hose 1. In order to solve this problem, a separate fixing tube 18 has been pressed down into the explosive before the latter has set. For the fastening function between charge and charging hose and for guiding the ignition cable down in the charge, use is made of a plastic tube 19, likewise -guided down in the explosive, with the same function and of the same type as the tube 6 in Fig. 1.

Claims

Case 3571PATENT CLAIMS

1. Method for, in association with blasting works with pumpable bulk explosives supplemented with initiating and/or reinforcing charges (5, 12) in the form of solid explosive units, on the charging of the boreholes (2) intended for said explosives, supplying said solid explosive units (5, 12) to the correct depth in the boreholes (2), characterized in that the respective explosive unit (5, 12) is coupled firmly in the mouth (1) of the respective pump hose, with which the bulk explosive is to be supplied to the respective borehole (2), whereupon the hose (1) is guided in to or down to the intended depth in the respective borehole (2) , whereupon the supply of the bulk explosive through the hose is started and the explosive unit (5, 12) is uncoupled from the hose.

2. Method according to Claim 1, characterized in that the coupling together between the pump hose (1) and the explosive unit (5, 12) is designed in such a manner that the pumpable bulk explosive, when it begins to flow out from the mouth of the hose, frees the explosive unit (5, 12) from the pump hose (1) .

3. Method according to Claim 2, characterized in that the pump hose (1), after the explosive unit (5, 12) has been freed from the same, is gradually drawn up out of the borehole (2) at the same time as this is filled with bulk explosive.

4. Arrangement for, in accordance with the method according to any of Claims 1-3, in association with blasting works with pumpable bulk explosives supplemented with initiating and/or reinforcing charges in the form of solid explosive units (5, 12), on charging of the boreholes (2) intended for said explosives, supplying said solid explosive units (5, 12) to the correct depth in the respective borehole (2) , characterized in that it includes a nozzle (1) for the hose with which the bulk explosive is to be supplied to the boreholes (2), said nozzle (1, 1') constituting a first coupling member while the actual explosive unit is provided with a second coupling member (5a, 6, 12a, 12b, 12b'), it being possible to join these two coupling members detachably to one another.

5. Arrangement according to Claim 5, characterized in that the explosive unit (4, 5) has, at the end which is intended to be coupled together with the nozzle (1) , a space (5a) empty of explosive, in which the outer end of the nozzle (1) can be pressed down.

6. Arrangement according to Claim 5, characterized in that the explosive unit (4, 5) also includes, cast firmly in the explosive (4) , a tube (6) which is elastically deformable at least to a certain extent and the interior (8) of which is adapted for introduction of the actual initiating function in the form of fuse, ignition cable or equivalent (10) and associated explosive cartridge (11) , the tube (6) , where it passes through the empty space (5a) of the explosive unit above the explosive, being positioned in such a manner that, when the nozzle is guided into place in said space, it is at least partially deformed by the latter in order thus to give rise to a resilient press fit against the nozzle between its own outside and the inside of the protection tube (5) which surrounds the explosive charge (4) .

7. Arrangement according to Claim 5 or 6, characterized in that the space empty of explosive (4) , in which the outer end or nozzle (1) of the charging hose is to be guided down, is constituted by a separate tube (18) of suitable diameter cast firmly in the explosive (4) , while the rest of the charge can have a greater diameter.

8. Arrangement according to Claim 5 or 7, characterized in that a part (12b' ) of the wall of the protection tube (12) which surrounds the empty space (5a) of the explosive unit, and in which the nozzle (1) is to be -guided down, is separated from the rest of the tube wall (12) along two parallel slits (15, 16) and compressed into the tube in order to function there as a resilient lock (12b) for the nozzle.

9. Arrangement according to Claim 8, characterized in that the nozzle (1) has a notch (1') in which the inwardly compressed part of the protection tube (12b) of the explosive charge can engage.

AMENDED CLAIMS

[received by the International Bureau on 13 August 1996 (13.08.96) original claims 1-9 replaced by amended claims 1-8 (2 pages)]

1. Method for, in association with blasting works with pumpable bulk explosives supplemented with initiating and /or reinforcing charges (5, 12) in the form of solid explosive units, on the charging of the boreholes (2) intended for said explosives, supplying said solid explosive units (5, 12) to the correct depth in the boreholes (2), characterized in that the respective explosive unit (5, 12) is coupled firmly in the mouth (1) of the respective pump hose, with which the bulk explosive is to be supplied to the respective borehole (2), whereupon the hose (1) is guided into or down to the intended depth in the respective borehole (2), and the coupling together between the pump hose (1) and the explosive unit (5, 12) being so designed that the pumpable bulk explosive, when it begins to flow out from the mouth of the hose, is acting on the end wall of the explosive unit facing the opening of the hose and thereby frees the explosive unit (5, 12) from the pump hose (1).

2. Method according to Claim 1, characterized in that the pump hose (1), after the explosive unit (5, 12) has been freed from the same, is gradually drawn up out of the borehole (2) at the same time as this is filled with bulk explosive.

3. Arrangement for, in accordance with the method according to any of Claims 1 or 2, in association with blasting works with pumpable bulk explosives supplemented with initiating and/or reinforcing charges in the form of solid explosive units (5, 12), on charging of the boreholes (2) intended for said explosives, supplying said solid explosive units (5, 12) to the correct depth in the respective borehole (2), characterized in that it include a nozzle (1) for the hose with which the bulk explosive is to be supplied to the boreholes (2), said nozzle (1, 1') constituting a first coupling member while the actual explosive unit is provided with a second coupling member (5, 6, 12, 12b, 12b'), it being possible to join these two coupling members detachably to one another, each of said coupling members constituting different parts of a resilient press fit the different parts of which are freed from each other when the bulk explosive starts to flow out from the pump hose. 4. Arrangement according to Claim 3, characterized in that the explosive unit (4, 5) has, at the end which is intended to be coupled together with the nozzle (1), a space (5a) empty of explosive, in which the outer end of the nozzle (1) can be pressed down. 5. Arrangement according to Claim 4, characterized in that the explosive unit (4, 5) also includes, cast firmly in the explosive (4), a tube (6) which is elastically deformable at least to a certain extent and the interior (8) of which is adapted for introduction of the actual initiating function in the form of fuse, ignition cable or equivalent (10) and associated explosive cartridge (11), the tube (6), where it passes through the empty space (5a) of the explosive unit above the explosive, being positioned in such a manner that, when the nozzle is guided into place in said space, it is at least partially deformed by the latter in order thus to give rise to a resilient press fit against the nozzle between its own outside and the inside of the protection tube (5) which surrounds the explosive charge (4).

6. Arrangement according to Claim 4 or 5, characterized in that the space empty of explosive (4), in which the outer end or nozzle (1) of the charging hose is to be guided down, is constituted by a separate tube (18) of suitable diameter cast firmly in the explosive (4), while the rest of the charge can have a greater diameter.

7. Arrangement according to Claim 4 or 5, characterized in that a part (12b') of the wall of the protection tube (12) which surrounds the empty space (5a) of the explosive unit, and in which the nozzle (1) is to be guided down, is separated from the rest of the tube wall (12) along two parallel slits (15, 16) and compressed into the tube in order to function there as a resilient lock (12b) for the nozzle.

8. Arrangement according to Claim 7, characterized in that the nozzle (1) has a notch (1 ') in which the inwardly compressed part of the protection tube (12b) of the explosive charge can engage.