US3541797A

US3541797A - Apparatus for loading boreholes

Info

Publication number: US3541797A
Application number: US755108A
Authority: US
Inventors: Iain G H Stewart
Original assignee: African Explosives and Chemical Industries Ltd
Current assignee: African Explosives and Chemical Industries Ltd
Priority date: 1967-08-29
Filing date: 1968-08-26
Publication date: 1970-11-24
Anticipated expiration: 1987-11-24
Also published as: FR1597508A; IE32836L; ES357656A1; IE32836B1; DE1758885B1; GB1202478A; NO119515B

Description

NQW FY1511 19m I. 5. H. STEWART 3,541,797

APPARATUS FOR LOADING BOREHOLES Filed Aug. 26, 1968 2 Sheets-Sheet 1 SUPPLY HOPPER Mag 040.;

FIGURE 3 NW. H4, 1970 I. G. H. STEWART 3,541,797

APPARATUS FOR LOADING liofillllohms Filed Aug. 26, 1968 6 2 Sheets-Sheet 2 FIGURE 6 3,541,797 APPARATUS FOR LOADING BOREHOLES Iain G. H. Stewart, Glendower, Edenvale, Transvaal,

Republic of South Africa, assignor to African Explosives and Chemical Industries Limited lFiletl Aug. 26, 1968, Ser. No. 755,108 Claims priority, application Republic of South Africa, Aug. 29, 1967, 67/5,162 llnt. Cl. E0211 7/24 US. Cl. 61--35 9 Claims AlBfiTlRACT OF THE DIISCLOSURE Apparatus for filling a borehole with a slurried or plastic mass. The apparatus comprises a tubular member having an open bore, at least one flexible annular element mounted on the tubular member and a flexible hose connecting the inlet end of the tubular member to supply means for supplying the slurried or plastic mass.

This invention relates to loading boreholes. More particularly, it relates to loading holes bored in civil engineering and mining operations for the purposes of cement grouting, foundation construction and blasting with explosives.

It is well known practice to fill or load boreholes simply by pouring the less viscous slurries down holes, which are substantially vertical to the ground surface. Materials of a more viscous nature are placed in the holes by being pumped through hoses inserted to varying depths within the holes. The principal difliculty with this loading procedure is the impossibility of seeing the rate at which the hole is being filled, which knowledge would enable the operator to withdraw the hose at a similar rate. If the hose is withdrawn too slowly, it becomes embedded in the material and is likely to leave a columnar gap or cavity on being withdrawn. Conversely, if the hose is withdrawn too rapidly, the material is likely to be dropped from a height above the rising surface of the slurry and entrap pockets of air. In most of these operations, discontinuity in the material filling of the hole is undesired or detrimental for the intended purpose.

The difliculty of loading materials against gravity in boreholes, slanting upwardly from the horizontal, is too well known to require elaboration.

There is yet another problem to be solved when boreholes contain substantial quantities of water. Slurries dropped or pumped into holes under wet conditions may be adversely affected by too great a degree of dilution so that, for instance, the grouting or cement mixture loses its property of strength when set or the explosive mixture cannot be initiated by a detonator or the explosion fails to propagate through the mixture.

It is extremely difficult, if not impossible, to fill holes of small diameter with a highly viscous material and more particularly if the holes contain water.

The chief object of the present invention is to enable operators to fill boreholes more completely with loading materials than appears feasible with known procedures.

A further object is to load wet boreholes in such a manner that the loading materials are not deleteriously affected by the water in the holes. Other objects will become apparent from the following description of the invention.

Accordingly, for filling a borehole with a slurried or plastic mass, this invention provides apparatus comprising a tubular member having an open bore, at least one flexible annular element mounted on the tubular member and a. flexible hose connecting the inlet end of the tubular member to supply means for supplying the slurried or plastic mass. The flexible annular element may be a flat 3,541,797 Patented Nov. 24, 111970 ring or washer or disc of a suitable material such as natural or synthetic rubber or a synthetic plastics material.

In order to hold the ring securely on the tubular member or nozzle of the apparatus, it may be seated in a groove or slot encircling the tubular member transverse to its longitudinal axis. In another modification of the invention, the ring may be clamped on the tubular member by suitable means fitted to the member. Clamping and screwing devices for securing annular fittings around the outer circumference of pipes and tubes are well known and are, therefore, not described and illustrated in this specification. Any such mechanical means suitable for the purpose may be employed. The major portion of the ring stands proud of the surface of the tubular member to provide a circular disc-like structure on the body of the member.

In another embodiment of the invention, two flexible annular elements are mounted on the tubular member. Such an arrangement assists in aligning the apparatus centrally in the hole and, thereafter, maintains it in a position substantially co-axial with the hole during its passage through the hole.

In yet another embodiment of the invention, at least one of the flexible annular elements is paired with a second, co-operating flexible annular element of greater diameter and having performations therein to perform in combination with the element as a non-return valve. The perforations in the second flexible annular element may be orifices or slots through its material surrounding the tubular member.

For a more complete understanding of the invention, embodiments of the apparatus and the method employed will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a view in perspective of the apparatus,

FIG. 2 is a view, partly in section, of a borehole and aparatus at the commencement of a borehole loading operation,

FIG. 3 is a view, partly in section, of a borehole and apparatus at the conclusion of a borehole loading operation,

FIG. 4 is a view in perspective of another embodiment of the invention,

FIG. 5 is a view, partly in section, of a borehole and the apparatus illustrated in FIG. 4 at the commencement of a borehole loading operation, and

FIG. 6 is a view, partly in section, of a borehole and the apparatus illustrated in FIG. 4 at the commencement borehole loading operation.

Referring to the drawings in which similar parts are indicated by like numerals, FIG. 1 shows the complete assembly of tubular member 4, flexible

annular elements

5 and 6 and flexible hose 7. The tubular member 4 is illustrated as a nozzle with an open bore, the inlet end of which communicates with the bore of the hose 7 and the outlet or discharge end of which is shown at 8. The hose 7 covering the inlet end of the nozzle 4 may be fastened thereto by a circular clip but, usually, the grip of the hose over the end of the nozzle is sufficiently tight to prevent disengagement during a loading operation. The end of the hose 7 remote from the nozzle 4 is connected to supply means, such as a pump, a pressurized slurry container or a mixer-placer unit provided with a pump (not shown), for supplying the slurry or plastic mass under pressure to the nozzle 4. In these drawings, the flexible

annular elements

5 and 6 are flat neoprene rings or discs secured in shallow, circular grooves as at 9 and 10 on the nozzle 4.

In practice, the apparatus is pushed down a borehole 11 by means of hose 7 until it is felt to have touched the bottom of the hole as illustrated in FIG. 2. If there is water in the hole, it is displaced past the rearwardly flexed neoprene rings. The neoprene rings and 6 are then flexed into the opposite direction by slightly retracting hose 7. At this stage, the

neoprene rings

5 and 6 act as flexible seals between the nozzle 4 and the wall 12 of the borehole 11. Pumping of the slurry or plastic mass is then started.

As soon as the spaceas defined by the wall 12 and the face of the borehole, the neoprene ring 5 and the surface of the nozzle 4 projecting from itis filled with the mass 13, the pressure exerted by the discharge from outlet 8 of the continuing flow of mass 13 forces the apparatus to rise in the borehole 11. If there is water as indicated by reference numeral 14, lying in the borehole, it may have been urged to flow past the ring 5 by the mass 13 and will then be raised by the piston action of the nozzle as the nozzle is displaced from the bottom of the hole. The neoprene rings act as barriers to separate the mass 13 from the water 14 as well as to ensure that the space forwardly of ring 5 in the borehole 11 is completely filled with the mass 13.

As the apparatus begins to rise in the borehole, the

neoprene rings

5 and 6 are flexed in the direction as shown in FIG. 3. In this trailing position, the efficiency of the seal improves with the increase of pressure differential across the neoprene ring 5. A portion of the mass 13 may escape into the space between the two

rings

5 and 6 due to surface irregularities in the borehole. However, this action will only further serve to ensure that the borehole 11 is completely filled with mass 13 to the exclusion of water 14 and unwanted air gaps.

It will be understood that the assembly of nozzle 4 and neoprene rings 5 and 6 acts as a sealing piston in the borehole 11, while accommodating variations in the diameter of the borehole, which may be likened to a cylinder. Moreover, the operator does not have to exercise any control over the rate of speed of withdrawal of the apparatus from the borehole. Having inserted the apparatus in the borehole and reversed the flexure of the flexible rings, he may then let it be ejected at a controlled rate, which is governed entirely by the rate at which the borehole 11 is being properly filled by mass 13.

The conclusion of the borehole loading operation is illustrated in FIG. 3, at which stage the pumping of the mass 13 through hose 7 is stopped. There may be a marker on the hose 7 adjacent the inlet end of the nozzle 4 as a visual warning to the operator to stop pumping or, if desired, pumping may be stopped as soon as the inlet end of the nozzle appears at the mouth of the borehole 11. The apparatus is then removed from the borehole 11 and inserted into another borehole, when the loading procedure described above is repeated.

It will be seen from the illustration in FIG. 3 that the water 14 has been almost completely expelled from borehole 11 and has overflowed from its mouth. The very minor volume of water shown may be removed entirely, if so desired, by continuing the pumping operation until the mass 13 rises to the mouth of borehole 11. In any event, much of this water would be removed by the rings 7 6 and 5 in withdrawing the apparatus from the borehole.

If mass 13 is an explosive composition, any water left in the borehole after withdrawal of the apparatus may be removed and/ or absorbed by the stemming material, such as rock cuttings or rubble, which may be poured into the hole to cover the explosive composition according to normal blasting practice.

Referring now to FIG. 4, in which is depicted a modification of the assembly shown in FIG. 1, reference nu meral 15 indicates a tubular member with an open bore, such as a nozzle. Its inlet end communicates with the bore of flexible hose 16 and that end of the nozzle 15 may be secured within the hose 16 by means of a fastener or circular clip 17, if considered necessary. The outlet or discharge end of the nozzle 15 is shown at 18. The free end of the hose 16 is connected to supply means, such as a pump or pressurized supply hopper (not shown), for supplying the slurry or plastic mass under pressure to the nozzle 15. In this assembly, there is illustrated one pair of flexible annular elements intended to act in combination as one unit 19. There may be more than one such unit 19 mounted on nozzle 15 or there may be both the

type

5 and 6 and the type 19 of flexible annular elements mounted on the same nozzle.

Element 20 is similar to

elements

5 and 6 of FIG. 1 but element 21 is of greater diameter than element 20 and has perforations through its material such as, for instance, slots 22. Preferably, element 20 may be as shown and is of a size which gives little, if any, contact with the wall of the borehole for which it has been selected as having suitable dimensions.

The method for filling a borehole 11, when using the assembly of FIG. 4, follows the same steps as are described above with reference to FIGS. 2 and 3. This description will be amplified with reference to FIGS. 5 and 6 to explain more exactly the action of the paired

elements

20 and 21, co-operating to perform as a unit 19 or flexible annular element 19.

In charging a borehole 11 with a plastic or slurried mass 13 though a tubular member 15 fitted with one or more paired flexible

annular elements

20 and 21, the perforated element 21 is flexed rearwardly as shown in FIG. 5 by frictional contact with the wall 12 of the borehole 11 as the member 15 is pushed down the hole 11. This action separates the two

elements

20 and 21 of the pair 19 and allows water 14, which may be contained in the hole 11, to pass the periphery of the leading, or first, non-perforated element 20 of smaller diameter and then escape through the perforations 22 of the second, or trailing, element 21. In the passage of the apparatus down the hole 11, the water 14 is thus displaced beyond the apparatus without the latter becoming an obstruction in the way of the water. On reaching the bottom of the hole, element 21 is flexed in the opposite direction as previously described. When the mass 13 is pumped through the apparatus and fills the space between the face of the borehole and the leading element 20 to cause the apparatus to rise in the borehole 11, the second or perforated element 21 is flexed in the opposite direction to press against the non-perforated element 20, as shown in FIG. 6. This action closes the perforations 22 and the build up of pressure, created by the mass 13 being pumped into the borehole 11, forces the element 20 against the element 21 and ensures a firm and positive closure of the perforations 22. The pair 19 of

elements

20 and 21 then act as a single unit in the same manner as element 5 or element 6 in the alternative embodiment of the invention shown in FIG. I and described above.

For larger holes filled with water, it may require considerable force to push the nozzle, on which is mounted flexible annular elements of the type illustrated in FIG. 1, down to the bottom of the hole. Where such conditions are encountered, it may be advantageous to use the type of element shown in FIG. 4.

Where the rock face is fissured, it is known to use liners of plastics material to ensure the retention of the explosive medium in the borehole. This procedure presents no difficulties in the use of the apparatus and method of the invention since the plastics liner is readily threaded over the nozzle and hose prior to its insertion in the hole. In fact, the placing of the liner is facilitated by this procedure in comparison with the conventional practice of weighting the bottom of the liner with a weight such as a boulder. Filling of the borehole with the explosive slurry than proceeds as described above.

Several trials of the method and apparatus of the invention were conducted at different locations to test the efliciency of operation. All these trials were successful and are described in the following examples.

EXAMPLE I Tests were carried out at the semi-technical plant of applicant. A vertical pipe, having a bore of four inches and a length of twenty feet, was filled with water. Using a positive displacement pump, having a two inch outlet, and seventy feet of plastic tubing of two inch bore connected to the apparatus assembly as exemplified by FIG. 1, the pipe was completely loaded with a dummy explosive slurry. It was observed that the water flowed evenly from the pipe as the apparatus filled it with the slurry and that the apparatus rose steadily in the pipe during the loading operation. The temperature of the water flowing from the pipe did not fall, indicating that there had not been any mixing with the particulate urea in the dummy slurry, which would have lowered the temperature of the resulting solution formed and discharged from the pipe. The quantity of slurry estimated to fill the pipe corresponded very nearly with the volume of the pipe.

This test was repeated twice with equally good results.

EXAMPLE II The test conducted in Example I was repeated three times, using two of the units 19--as illustrated in FIG. 4 as the flexible annular elements mounted on the nozzle in place of the two rings previously used.

The three tests produced excellent results.

EXAMPLE III The test conducted in Example II was repeated but in the absence of water. The dry pipe was loaded successfully to its full capacity with the dummy explosive slurry, indicating that no air gaps were interrupting the continuity of the slurry column.

EXAMPLE IV The test conducted in Example II was repeated but in the absence of water. The dry pipe was loaded successfully to its full capacity with the dummy explosive slurry, indicating that no air gaps were interrupting the continuity of the slurry column.

EXAMPLE V A test was conducted in the quarry of the Mooiplaas Dolomite Quarry at Cordelfos in the Transvaal. Six holes were drilled in loose boulders on the quarry floor measuring one and a half inches in diameter by five feet in depth. Two of these holes were horizontal while four holes sloped upwardly from the horizontal level at various angles between fifteen to twenty degrees. Only one ring, of the type exemplified by FIG. 1, was mounted on the nozzle. Each hole was loaded by the apparatus with six pounds of an explosive slurry composition.

On detonation, the blast was successful.

EXAMPLE VI A test was conducted in a stope on the property of the Vlakfontein Gold Mining Company near Springs, Transvaal, on the following boreholes, which had been drilled a long time previously and were extremely irregular because of rock movement.

6 crater holes measuring 1 /2 inches diameter by 36 inches deep. Horizontal.

3 crater holes measuring 1 /2 inches diameter by 72 inches deep. Horizontal.

stope holes measuring 1 /2 inches diameter by 42 inches deep. Angled downwardly and full of water.

The poor condition of the holes made this test an unfair one and considerable difficulty was experienced in inserting and ejecting the nozzles. Nevertheless, the crater holes and eight of the stope holes were charged with a pumpable, explosive slurry composition through a nozzle on which was mounted one ring of the type exemplified by FIG. 1 and the ensuing blasts were successful.

EXAMPLE VII A test was conducted in a stope on the property of the Vlakfontein Gold Mining Company on the following boreholes, which had been drilled just prior to the time of the test.

7 stope holes measuring 1 /2 inches diameter by 42 inches deep and at angles slightly above and below horizontal.

2 stope holes measuring 1 /2 inches diameter by 42 inches deep and horizontal.

8 holes in the drive at various angles below the horizontal level and all full of water.

The apparatus worked smoothly with one ring, of the type exemplified by FIG. 1, mounted on the nozzle and all holes were loaded with a pumpable, explosive slurry composition.

The blasts were successful.

EXAMPLE VIII A test, included in simulated shaft sinking experiments on the property of the Vlakfontein Gold Mining Company, was conducted on eight boreholes measuring one and a half inches by five feet deep. Four of these holes were vertical cut holes and four holes, which surrounded the cut holes, were easers. The cut holes are blasted first and the subsequent blasting of the easers widens the hole created by the first blasting operation.

The working place was flooded to a depth of about six inches under water after completion of the borehole drilling. All eight holes were then loaded with a pumpable, explosive slurry composition through an apparatus assembly as exemplified by FIG. 1.

The loading operation and subsequent blasting of the holes were completely successful.

EXAMPLE IX A test was conducted on the floor of the quarry of the Mooiplaas Dolomite Quarry during a pop shooting or secondary blasting operation. This is an operation, which takes place after the main blasting operation, to break up oversize material too heavy for removal or treatment.

Forty holes, measuring one and a quarter inches in diameter by lengths varying from one to two feet in depth, were drilled into large boulders. The holes were then charged with a pumpable, explosive slurry composition through a nozzle on which was mounted one ring of the type exemplified by FIG. 1.

The loading operation and subsequent shattering of the boulders by blasting the charges in the holes were completely successful.

An advantage of the present invention is that it provides a means for loading boreholes at any inclination to the horizontal.

A further advantage is that the apparatus enables the proper filling of holes of small diameter with viscous masses. The size of the hole will determine the choice of size of nozzle and rings. Furthermore, fairly large variations in borehole diameters may be accommodated by a given set of flexible rings.

I claim:

ll. For filling a borehole with a slurried or plastic mass, apparatus comprising a tubular member having an open bore with an inlet for supply of said mass and an outlet therefor at the opposite end thereof, at least one flat flexible annular element mounted on the tubular member of a dimension larger than the borehole and adapted for continuous circumferential contact with said borehole, said element being flexed rearwardly by contact with the borehole as said member is moved into and out of said hole, said element functioning to serve as a barrier to mass discharged into said borehole from said outlet so that said tubular member is moved out of said borehole by the action of said discharged mass against said element as the borehole is filled, and a flexible hose connecting the inlet end of the tubular member to supply means for supplying the slurried or plastic mass.

2. Apparatus as claimed in claim 1 in which the element is a fiat ring, washer or centrally holed disc.

3. Apparatus as claimed in claim 1 in which the element is of a natural or synthetic rubber or a synthetic plastics material.

4. Apparatus as claimed in claim 1 in which the element is mounted on the tubular member by being seated in a groove or slot encircling the member transverse to its axis.

5. Apparatus as claimed in claim 1 in which two elements are mounted on the tubular member.

6. Apparatus for filling a borehole with a slurried or plastic mass, said apparatus comprising a tubular member having an open bore, at least one flexible annular element mounted on the tubular member and a flexible hose connecting the inlet end of the tubular member to supply means for supplying the slurried or plastic mass, at least one of the flexible annular elements being paired with a second, co-operating flexible annular element of greater diameter and having perforations therein to perform, in combination with the element as a non-return valve.

7. Apparatus as claimed in claim 6 in which the perforations in the second flexible annular element are orifices or slots through its material surrounding the tubular member.

8. Apparatus as claimed in claim 1 in which the supply means is a slurry pump or pressurized supply hopper.

9. For filling a borehole with a slurried or plastic mass, apparatus comprising a tubular member having an open bore, at least one flexible annular element mounted on the tubular member and a flexible hose connected to the inlet end of the tubular member, the free end of the flexible hose being adapted for connection to means for supplying the slurried or plastic mass, at least one of the flexible annular elements being paired with a second, cooperating flexible annular element of greater diameter and having perforations therein to perform in combination with the element as a non-return valve.

References Cited UNITED STATES PATENTS 2,719,768 10/1955 Webber. 2,729,067 1/1956 Patterson e 6153.58 3,255,592 6/1966 Moor 6153.64

REINALDO P. MACHADO, Primary Examiner P. C. KANNAN, Assistant Examiner US. Cl. X.R. 61-45, 53.64