Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42D—BLASTING
  • F42D1/00—Blasting methods or apparatus, e.g. loading or tamping
  • F42D1/08—Tamping methods; Methods for loading boreholes with explosives; Apparatus therefor
  • F42D1/10—Feeding explosives in granular or slurry form; Feeding explosives by pneumatic or hydraulic pressure

Definitions

• ABSTRACT In a method of filling aquiferous boreholes with a powdered ammonium nitrate explosive containing swelling and water-repellentizing agents which is uncartridged by means of a gaseous propellant from a pressure tank through a conduit. the improvement which comprises feeding said explosive composition to said aquiferous borehole through an orifice positioned toward the bottom of the borehole and thereafter step-wise or continuously withdrawing from the bottom such orifice from such conduit such that the orifice is located no more than 50 cm above the surface of the delivered explosive and below the surface of the water in the borehole.
• This invention is directed to a process of filling boreholes with explosives. More particularly, this invention is directed to a method of filling an aquiferous borehole with a powdered ammonium nitrate type explosive whereby water need not be removed prior to the time that the explosive composition is introduced into the borehole. Still more particularly, this invention is directed to a process wherein in a one-step operation a borehole is charged with an explosive composition, and water present in said borehole is displaced upwardly toward the entrance to such borehole.
• this invention contemplates an improvement in a method of filling aquiferous boreholes with (l explosives (2) wherein the explosives are carried by a gaseous propellant, said improvement comprising delivering said explosive to the bottom of said borehole by means of a gaseous propellant and during the filling process withdrawing from the borehole in a step-wise or continuous manner, the orifice from which said propellant and said explosives emanate so as to position the orifice above the surface of the delivered explosive and below the surface of the water in the borehole.
• the present invention contemplates an improvement in a method of filling aquiferous boreholes with (l) explosives (2) by use of a gaseous propellant from a pressure tank through a conduit, said improvement comprising positioning the orifice of said conduit toward the bottom of the borehole and during the filling of said borehole with said explosive step-wise or continuously withdrawing said orifice from the borehole such that the orifice is positioned no more than 50 cm above the surface of the delivered explosive and below the surface of the water in the borehole.
• the orifice from which the explosive and propellant emanate is positioned no more than cm above the surface of the delivered explosive.
• boreholes that are initially filled with water can be filled with explosives such as powdered ammonium nitrate explosives without removing the water prior to the filling operation.
• explosives such as powdered ammonium nitrate explosives
• a powdered ammonium nitrate explosive can be propelled into an aquiferous borehole by the use of compressed air.
• the orifice from which the ammonium nitrate explosive and compressed air are discharged is positioned no more than 50 cm above the surface of the bottom of the borehole.
• the orifice is stepwise or gradually removed so that it is positioned no more than 50 cm above the surface of explosive already placed in the borehole. Preferably, it is positioned no more than 10 cm above the surface of the explosive within the borehole.
• the air discharged from the hose orifice during the injection and filling operation has been found to result advantageously in a virtual partition between the explosive and the water above it.
• the method of the present invention'can therefore easily be applied to boreholes completely filled with water. Particularly advantageous is the great degree to which the borehole can be filled with explosive offsetting the small technical expenditure required for good lasting power.
• the invention has been described above as being applicable to powdered explosives (l) broadly. It is particularly contemplated to use as the explosive an ammonium nitrate explosive alone or in admixture with other substances such as an aluminum powder, a mineral oil and the like. Additionally, the invention has been described as employing a gaseous propellant which propels the explosive into the borehole at the bottom thereof, which gaseous propellant lifts the water in the aquiferous borehole. While any number of different gaseous propellants, including the halogenated alkanes, can be employed for this purpose, it is, of course, preferable to use a readialy available, inexpensive gaseous propellant. Nitrogen and air are particularly contemplated.
• the withdrawal of the hose in the method of the invention can be performed easily and in a simple manner, since the operator can easily feel from the slight vibration of the hose as the explosive flows through it whether the explosive is still freely flowing or whether the amount flowing through is diminishing because the level of the explosive rising in the borehole is approaching too closely to the hose orifice, thereby impairing the discharge of the explosive from the hose. In the latter case the hose is then simply withdrawn by a certain amount so that the explosive again flows freely. At the same time it is easily possible to assure the perfect flow of material in the hose by appropriate automatic devices, such as a microphone mounted on the hose and containing a system for the automatic withdrawal of the hose.
• ammonium nitrate Up to 50% by weight of the ammonium nitrate may be replaced by other oxygen-yielding salts, such as nitrates or perchlorates of the alkali or alkaline earth metals, for example. Also, these oxygen-yielding salts should, like the ammonium nitrate, be in a grain shape and fineness which will assure easy air injection.
• the expression long-chain is to be underployed together with a water-repellentizing agent.
• repellentizing agents can be present in the explosive in the absence of the swelling agent.
• Lubricants such as graphite of molybdenum disulfides, for example, may also be added to the explosive.
• the powdered ammonium nitrate explosives can contain combustible substances, such as mineral oil or diesel oil, nitrotoluenes, coal dust, glycol, urea, wood flour or vegetable flour. They can also contain metallic combustibles such as aluminum, magnesium or alloys of that nature.
• ammonium nitrate explosives named are already known as such on the basis of the nature and quantity of their composition for use in cartridge form, the cartridge casing, along with the action of the swelling agents and/or water-repellentizing agents, providing substantial protection against the penetration of water into the explosive
• the use of the cartridge casing was the only factor that made it possible at all to use powdered ammonium nitrate explosives in aquiferous boreholes. It has the disadvantage, however, that complete filling of the borehole or full utilization of the borehole volume for the explosive cannot be achieved.
• the last section of the hose can be replaced by a pipe. Holes can be provided laterally at the end of the hose or pipe so that part of the air escapes through them and promotes the displacement of the water.
• An annular bead can also be provided at the end of the hose to aid the pushing of the hose out of the borehole by the delivered explosive on the one hand, and on the other hand, to additionally favor the displacement of the water as a result of the higher velocity of the air jet between the bead and the wall of the borehole.
• the pressure of the propellant e.g. air is between 0.5 and 10 kp/cm excess-pressure.
• the method of the invention can also be utilized to place a higher-energy explosive at the bot tom of the pressure tank and a lower-energy explosive on top of it so that a more powerful explosive will be charged in the bottom of the borehole and a less powerful explosive will be placed above that as the pressure tank empties from the bottom.
• the bottom end of the explosive column in the borehole be as free as possible of water
• the additional air required for this purpose can be delivered to the hose laterally at an appropriate point.
• Aluminum powder 30 weight percent 10 weight percent Mineral oil 2 weight percent Calcium stearate 1 weight percent Guar flour 2 weight percent The mixture was blown'through a 6-meter-long air hose of 25 mm inside diameter from a pressure tank feeding apparatus into a vertical pipe 4.50 m long, with an inside diameter of 80 mm, filled with water.
• the pipes l consisted in its lower portion of a glass-clear section 2 m long for observation of the charging operation.
• the working pressure in the pressure tank was 3 kp/cm At this pressure a ratio by volume between solid and air (converted to a pressure of l kp/cm of 1:2 to l:3 was achieved in the charging hose.
• the column had a moisture distribution as follows: At the bottom, i.e., in the area where the blowing began, there was a plug 10 cm long with a 22% water content. Then followed the main column cm long which was produced by continuous blowing, with a water content of4 Between this comparatively dry portion of the charge column and the water column remaining above it there was a wet section cm long with a water contentofl6%. i g r In use in the borehole the comparatively dry explosive portion constitutes virtually the entire charge column, and the short, moist sections at both ends of the charge column take no part in the total explosive mass.
• An explosive column with 4% moisture content was introduced in another steel pipe with an inside diameter of 52 mm, a wall thickness of4 mm and a length of 450 mm.
• a plug with a moisture content 50 mm long and one with 13% moisture content and I00 mm long deliberately interposed by way of experiment did not interfere with the detonation by the booster charge.
• the same explosive mixture was also blown through a 23-meter-long hose with a 25 mm inside diameter from the pressure tank charger into a 13.5-meter-long, water-filled pipe whose axis was inclined from the vertical (slanting). The inside diameter was again 80 mm. The bottom end of the pipe was again transparent.
• the working pressure in the pressure tank amounted to 4 kp/cm
• some compressed air was additionally blown into the injection hose at a point below the charging tank in order to further loosen up the material to be transported in the hose. In this manner a volume ratio between the material and the air of 1:4 to 1:5 was achieved.
• Example 1 The blowing-in process in the procedure of Example 1 took place with no friction. If this additional air was used and was injected into the charging hose before the valve on the charging tank was opened, the water in the bottom of the borehole was partially displaced before the explosive emerged from the charging hose. This eliminated the wet, approximately 100 mm long plug of explosive at the bottom of the borehole. The continuously charged explosive column had absorbed a moisture content of only I to 3% in this experiment. Between this comparatively dry explosive column and the water above it there was again a more thoroughly wet explosive column of 100 to 200 mm length.
• NH NO prilled (9O weight-71 grain size between 0.8 and 2.5 mm. balance smaller than 0.8 mm) 55.5 weight percent NH,NO ground Aluminum powder 31.0 weight percent 5.0 weight percent that was fluid at 0C.
• a method according to claim 3 wherein the explosive consists of 60 to 98 weight percent ammonium nitrate and 2 to 40 weight percent of a combustible substance, said combustible substance containing up to 10 weight percent, based upon the weight of the explosive, of a swelling agent.
• a method according to claim 3 wherein said explosive consists of 60-98 weight percent ammonium nitrate and 2-40 weight percent of a combustible substance, said combustible substance containing up to 3 weight percent, based upon the weight of said explosive, of a water-repellentizing agent.
• a method according to claim 3 wherein the explosive composition is delivered from a pressure tank which feeds said conduit, which pressure tank is filled with an energy-rich explosive at the bottom thereof and an explosive of lesser energy above said energy-rich explosive whereby, as the pressure tank empties from the bottom, the explosive of greater strength is charged into the bottom of said borehole and the explosive of weaker strength is charged into the portion above said bottom.
• a method according to claim 3 wherein immediately before the commencement of the injection of the explosive, a gaseous propellant is fed through the conduit into the bottom of the borehole whereby to displace a portion of the water contained therein.
• a method according to claim 3 wherein the pressure of the compressed air is between 0.5 and 10 kp/cm excess pressure.

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• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Geophysics And Detection Of Objects (AREA)
• Drilling And Exploitation, And Mining Machines And Methods (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)

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Family Applications (1)

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Cited By (7)

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Citations (6)

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• 1972
  • 1972-09-01 DE DE2243192A patent/DE2243192A1/de active Pending
• 1973
  • 1973-07-12 CH CH1018673A patent/CH552785A/de not_active IP Right Cessation
  • 1973-08-09 ZA ZA735421A patent/ZA735421B/xx unknown
  • 1973-08-27 US US391722A patent/US3921497A/en not_active Expired - Lifetime
  • 1973-08-30 AT AT753573A patent/AT341926B/de not_active IP Right Cessation
  • 1973-08-30 IT IT52246/73A patent/IT990426B/it active
  • 1973-08-31 GB GB4120973A patent/GB1414723A/en not_active Expired
  • 1973-08-31 FR FR7331579A patent/FR2198117B1/fr not_active Expired
  • 1973-08-31 CA CA180,154A patent/CA987935A/en not_active Expired
  • 1973-08-31 BE BE135152A patent/BE804269A/xx unknown
  • 1973-08-31 ES ES418364A patent/ES418364A1/es not_active Expired
  • 1973-08-31 BR BR6747/73A patent/BR7306747D0/pt unknown

Patent Citations (6)

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