Abstract: Methods for evaluating drill pattern parameters such as burden, spacing, borehole diameter, etc., at a blast site are disclosed. One method involves accumulating the burden contributed by successive layers of rock and matching the accumulated rock burden to a target value for a borehole having a length related to the average height of the layers. Another method relates to varying drill pattern parameters and characteristics to match blast design constraints, including the substitution of one explosive material for another by the proper balance of materials and/or output energies to the associated rock burden. Analysis of deviations from target rock burdens and corrective measures are disclosed, as well as cost optimization methods. The various methods can be practiced using an appropriately programmed general purpose computer.

Abstract: A method of blasting in which rock pile profile associated with a blast field is controlled by precise control of the detonation delay times between and/or within individual blastholes in the blast field, in combination with the control of one or more other blast parameters. One or more of the blast parameters may by blasthole geometry, explosive charge or blast initiation location.

Abstract: A drill hole (350) extends into rock to be blasted. A blasting accessory (310) includes a container portion (312) for holding a predetermined volume of stemming material, and a spacer (330) for spacing the stemming material a predetermined distance from a surface, e.g. a blind bottom of the drill hole. The container portion has a top (320) surrounded by a dilatable, inverted skirt forming a seal (342), and forms a support for a blasting substance like an explosive.

Abstract: An actuation and/or communication device for the downhole environment. The device includes a selectively implosion resistant canister; and an environment within the canister and releasable upon implosion of the canister. A method for actuating a downhole device and/or communicating. The method includes delivering a selectively implosion resistant canister having an environment internal to the canister releasable upon implosion of the canister to a selected location within a borehole; imploding the canister; releasing the environment; and receiving a signal generated by the release of the environment. A method for an actuating a tool and/or communicating including delivering of an implosive device to a selected location; creating a rarefaction event by imploding said device; and affecting a tool in response to the event.

Abstract: Disclosed is a device and method for externally perforating a well-bore casing. The perforating apparatus is attached to the outside of the casing itself and is conveyed along with the casing when it is inserted into the well bore. The perforation is accomplished using two groups of charges which are contained in protective pressure chambers which are arranged radially around the outside of the wellbore casing. The pressure chambers form longitudinally extending ribs which conveniently serve to center the casing within the well bore. One group of charges is aimed inward in order to perforate the casing. A second group is aimed outward in order to perforate the formation. In an alternative embodiment, only one group of bi-directional charges is provided.

Abstract: A method and apparatus for placement of continuous pre-split, gel explosive in an elongated borehole or cavity. An anchor is attached to one end of a selected length of continuous gel explosive. A suitable anchor is a flexible, plastic “pilgrim's hat” with a hole in the narrow, closed end. The size of the anchor depends on the width of the borehole; the flared skirt should be narrow enough to permit insertion of the anchor into the hole but wide enough to resist removal. One end of the explosive charge is pressed through the hole in the anchor. The remainder of the length of explosive is placed inside a tubular member, such as PVC pipe. The loaded pipe then is inserted into the borehole or cavity with the anchor leading. The pipe is used to push the anchor back into the hole to the desired depth. Then, the pipe is withdrawn. The flexible skirt on the anchor engages the sidewall of the borehole and thus resists removal with the pipe.

Abstract: Embodied herein is a perforating gun wall that withstands short, high energy pulses of an explosion retained within a loading tube with numerous explosive shaped charges. The perforating gun wall includes two or more layers with an impact strength sufficient to maintain the structural integrity of the gun wall without splitting due to the explosion. Each layer is sleeved within the preceding layer forming a sleeved assembly. One or more of the inner layers includes one or more holes aligned with one or more explosive shaped charges. Each layer comprise a defined material property that reduces occurrences of catastrophic failure.

Abstract: A modular explosives cartridge comprises a tubular body having lockable coupling members secured on opposite ends thereof to form a bayonet coupling between opposite ends of respective cartridges to form an elongate tubular explosives cartridge. The lockable coupling members each include a sealing membrane to form a sealed closure at opposite ends of the tubular body, the sealing membranes being pierced during coupling to form a continuous column of explosive composition within said elongate tubular cartridge.

Abstract: A method of logging use of a non-electric detonator, which comprises recording identity data associated with the detonator at the time the detonator is being loaded in a blasthole, recording consumption of the detonator, and relating the identity data associated with the detonator to an inventory of non-electric detonators thereby allowing the inventory to be updated, wherein the identity data associated with the non-electric detonator are recorded using an electronic device.

Abstract: A system for fracturing wells uses a primary propellant charge to initially produce pressures within the well in excess of the maximum fracture extension pressure of the surrounding formation, but below that which would cause damage to the well. A supplemental propellant charge burns for a substantially longer period of time than the primary propellant charge, and thereby maintains pressures within the well in excess of the maximum fracture extension pressure for a significant period of time following completion of the primary propellant burn.

Abstract: A perforating device having a longitudinal axis comprising: a loading tube having an explosive charge; a first layer slidable, non fixedly, and removeably disposed over the loading tube; and at least one outer layer in fixed engagement over the first layer and wherein the outer layer is a solid structure.

Abstract: The manufacture is carried out in a continuous manner simultaneous to the filling of the shot holes, in a mixer, preferably a rotating mixer, wherein a water-based, non-explosive or low sensitivity matrix, an air bubble stabilizing agent, and optionally, an oxidant in granular form and a combustible material are mixed together. The nature of the water-based matrix, together with the use of an air bubble stabilizing agent, allows the incorporation of air during the mixing, regulating the density of the final product and acting on the variables of the process. On coming out of the mixer, the explosive is totally sensitized and has reached its final density, allowing for quality control before filling the shot hole. The process may be carried out on the explosives pumping truck, with compartments for the transportation of a water-based matrix, an oxidant in granular form, a combustible material and a gas bubble stabilizing agent.

Abstract: The invention relates to a method to use a perforating gun in oil and natural gas wells, comprising: a perforating gun with a loading tube and explosive charge; the gun comprises: a first layer disposed over the loading tube and at least one outer layer in engagement over the first layer; the outer layer is a solid structure with scallop openings disposed therein and the scallops are in the solid structure in a defined pattern; wherein the method comprises: suspending the gun with a loading tube and explosive charge in a well bore wherein the gun has a longitudinal axis parallel to the sides of the well bore; detonating the explosive charge in the gun; permitting a gas jet to pierce the first layer and outer layer of the gun perpendicular to the longitudinal axis of the gun, well casing and to enter and fracture the strata surrounding the well.

Abstract: Primer casing (1) comprising sleeve portion (5) and leading portion (5a), wherein sleeve portion (5) includes tabs (6) to retain primer (11) and blasthole engagement means (2), and wherein leading portion (5a) comprises nose cone (8). Engagement means (2) comprises an array of rigid, multiple projections that are hinged and movable between a retracted position and a blasthole engagement position. Explosive loading hose (13) locales within hose receiving sleeve (7) and can be used to push primer casing (1) into the desired location within the blasthole prior to filling the blasthole with bulk explosive. Methods of loading a blasthole comprising inserting primer (11) into primer casing (1) and positioning primer casing (1) at a desired location in a blasthole are also described and claimed.

Abstract: A novel method and device for sealing a borehole that is filled either partially or completely with water. A water-permeable sleeve is capable of expanding to the diameter of the borehole, and is constructed of a material that will allow the passage of water in and out throughout its length, with a series of apertures, but will prevent an explosive charge from escaping. Once the sleeve is in place, a hose, to introduce the explosive charge, is lowered through the sleeve to bottom of the borehole.

Abstract: Apparatus for delivering an emulsion explosives composition comprising unpressurized vessel (10) for storing or supplying the explosives composition to pressure chamber (1); sealable chamber inlet (2) for charging chamber (1) with emulsion explosives composition from vessel (10); and chamber outlet (4). Fluid pressure opening (6) applies a discharge pressure to chamber (1) for delivering emulsion explosives composition through outlet (4) to delivery hose (11) for charging blast holes. The apparatus is characterized by pressure chamber (1) having a maximum operating pressure and a volume such that the pressure volume (pV) value of chamber (1) is less than 10 MPaL.

Abstract: The borehole of many wells, including oil and gas production wells, is frequently cased with a steel or similar metal casing. In order to extract oil or other material existing within the surrounding geologic formation, it is necessary to puncture the casing. Currently, this is accomplished with tubes (guns) containing explosive charges being lowered into the well bore and detonated, causing the tube and well casing to be punctured and the geologic formation shattered. The guns are made from high strength, thick-walled and machined metal. This invention discloses a multi-layered or composite tube that enhances the directional orientation of the explosive charges utilizing less costly and more easily fabricated material. The invention also discloses a gun having properties to allow the desired directionally oriented perforation by the explosive charge without being deformed and jammed within the well casing. Other advantageous are also disclosed.

Abstract: A method of protecting predilled, uncharged bore holes for use in an underground mine engaged in stope mining; the method comprising the steps of filling the uncharged bore holes with a liquid and sealing the entry of the liquid-filled blast holes prior to detonating adjacent blast holes. The liquid to be used will depend on the material being mined. In impervious material, the liquid is water. In porous material, the liquid may be viscous or have sealing properties such as a drilling mud or bentonite mud. Various plugs for sealing the bore holes are also described and claimed.

Abstract: A gas-generator is disclosed to intensify output of oil, gas, including gas from coal formations, or metals extracted by underground leaching by breakage and thermo gas chemical treatment of the critical formation zone with gaseous combustion products from a solid propellant. The rate of increase of gas pressure is raised and the effect on the formation is enhanced by assembling the gas generator using coated and bare charges in a selected ratio. The charges burn radially, so the coated charges, which burn only from the center outwards, burn for longer and with a rising output. A two-peaked pressure characteristic is thus obtained. A high-velocity igniter may also be used to give a third, early pressure peak.

Abstract: A method and apparatus for removing a tubular member (e.g., leg of an abandoned or obsolete fixed platforms in a marine environment) is provided. The apparatus includes a delivery system having a frame carrying explosive shaped charges. The frame includes charges having curved sections which can be moved relative to one another for engaging the inside bore of a tubular member to be severed. The charges are biased (e.g., spring loaded) to be moved automatically to an extended position that engages the tubular member (e.g., platform leg) when a trigger is activated from a remote location. The trigger can be a pin carried in a tube with wires connecting each curved charge section to the pin. When the pin is lifted from its tube, the wires are released enabling the springs to thrust the charges against the inside of a pipe, leg or tubular member to be cut. Once in this position, the charges can be fired.

Abstract: A solid column explosive charge method for blasting rock includes a hollow gas-filled core component arranged collinearly in concentrically spaced relation within a vertical borehole, the core component being seated upon a first layer of particulate explosive material, and a first annular portion of the particulate explosive material being arranged concentrically about the core component. The first layer and the first annular portion are in engagement to define a continuous explosive column. A plurality of core components together with associated layers and annular portions of the explosive charge may be arranged in a continuous vertical column, the total volume of the core components being from 10 percent to 25 percent of the volume of the explosive column. A top layer of inert fill material is arranged above the core component to close the upper end of the bore opening.

Abstract: A device, system and method permitting on-line explosives-based cleaning and deslagging of a fuel burning facility (31) such as a boiler, furnace, incinerator, or scrubber. A coolant, such as ordinary water, is delivered to the explosives (101) to prevent them from detonating due to the heat of the on-line facility. Thus, controlled, appropriately-timed detonation can be initiated as desired, and boiler scale and slag is removed without the need to shut down or cool down the facility.

Abstract: Disclosed herein is a method for generating energy by using exothermic reaction of metal, comprising the steps of reacting an oxidant containing mostly water with combustion substances mainly containing light metals to generate hydrogen; reacting generated hydrogen with nitric acid, sulfuric acid, chlorine peroxide, metal nitrate, metal perchlorate, metal sulfate, and hydrogen peroxide to generate water and heat; continuously repeating the above two steps with the use of water to gradually increase explosive power, and to a method for utilizing generated energy. The method can generate increased amounts of energy by repeatedly reacting oxidants such as water, liquid acid, and metal salt with combustion substances containing mostly light metals, and has economic advantages in that inexpensive substances such as light metal and oil are used as combustion substances.

Abstract: A method and apparatus for placement of continuous pre-split, gel explosive in an elongated borehole or cavity. An anchor is attached to one end of a selected length of continuous gel explosive. A suitable anchor is a flexible, plastic “pilgrim's hat” with a hole in the narrow, closed end. The size of the anchor depends on the width of the borehole; the flared skirt should be narrow enough to permit insertion of the anchor into the hole but wide enough to resist removal. One end of the explosive charge is pressed through the hole in the anchor. The remainder of the length of explosive is placed inside a tubular member, such as PVC pipe. The loaded pipe then is inserted into the borehole or cavity with the anchor leading. The pipe is used to push the anchor back into the hole to the desired depth. Then, the pipe is withdrawn. The flexible skirt on the anchor engages the sidewall of the borehole and thus resists removal with the pipe.

Abstract: The present invention is directed to a cartridge that includes a number of advantageous features. For example, the cartridge can include a bulk energetic material, an igniter located in a central portion of the cartridge body, and a low void space in the cartridge.

Abstract: A method of and apparatus for use in establishing a blasting arrangement by loading at least one detonator (14) into each of a plurality of blast holes (30), placing explosive material in each blast hole, connecting to a trunk line (10) a control unit (32) that has a power source (52) incapable of firing the detonators, sequentially connecting the detonators, by means of respective branch lines (12), to the trunk line and leaving each detonator connected to the trunk line. In addition the apparatus includes means (46, 50) for receiving and storing in memory means (34, 44) identity data from each detonator, means (46, 50) for generating a signal to test the integrity of the detonator/trunk line connection and the functionality of the detonator, and means (46, 50) for assigning a predetermined time delay to each detonator to be stored in the memory means. The invention also extends to the control unit (32).

Abstract: Disclosed herein is a rock blasting method using air bladders embedded in explosives. The rock blasting method includes the step of drilling a plurality of loading holes into a rock to predetermined depths in a predetermined arrangement. Thereafter, the loading holes are loaded with a plurality of initial explosives, a plurality of primers and a plurality of explosives in such a way that one or more air bladders are inserted into each of the loading holes and surrounded by the explosives. Thereafter, the loading holes are stemmed with stemming materials in the portions of the loading holes situated over the explosives. The primers are detonated so that the initial explosives and explosives are blown up. Hence, the loading lengths of the explosives are increased in proportion to the lengths of the air bladders so that a projection area formed on the free face of the rock is increased.

Abstract: Apparatus for delivering an emulsion explosives composition comprising unpressurised vessel (10) for storing or supplying the explosives composition to pressure chamber (1); sealable chamber inlet (2) for charging chamber (1) with emulsion explosives composition from vessel (10); and chamber outlet (4). Fluid pressure opening (6) applies a discharge pressure to chamber (1) for delivering emulsion explosives composition through outlet (4) to delivery hose (11) for charging blast holes. The apparatus is characterisedby pressure chamber (1) having a maximum operating pressure and a volume such that the pressure volume (pV) value of chamber (1) is less than 10 MPaL.

Abstract: The procedure involves the mixture of a water based oxidizing product with an oxygen balance greater than 14% consisting of a water solution saturated with oxidizing salts, oxidizing particles in suspension and thickening agents, with a fuel and a gas in a mixer, by means of the formation of an intimate mixture of the oxidizing product and the fuel and the formation of a suspension or emulsion of gas in the mixture. The density of the end explosive product may be varied according to the gas flow and this is controlled before introducing the explosive into the bore. The installation consists of a tank (1) with the oxidizing product, a fuel tank (11), a gas reserve (10), a mixer (5), a pump (3), a dosing device for the fuel (12) with a flow meter (13) and a regulating device of the gas flow (8), and, optionally, a tank (2) with a stabilizer of the gas bubbles, a dosing pump (4) and a flow meter (7).

Abstract: A method and apparatus for placement of continuous pre-split, gel explosive in an elongated borehole or cavity. An anchor is attached to one end of a selected length of continuous gel explosive. A suitable anchor is a flexible, plastic “pilgrim's hat” with a hole in the narrow, closed end. The size of the anchor depends on the width of the borehole; the flared skirt should be narrow enough to permit insertion of the anchor into the hole but wide enough to resist removal. One end of the explosive charge is pressed through the hole in the anchor. The remainder of the length of explosive is placed inside a tubular member, such as PVC pipe. The loaded pipe then is inserted into the borehole or cavity with the anchor leading. The pipe is used to push the anchor back into the hole to the desired depth. Then, the pipe is withdrawn. The flexible skirt on the anchor engages the sidewall of the borehole and thus resists removal with the pipe.

Abstract: This invention relates to a method of delivering a water-based explosive by feeding a water-based explosive and a fluid non-explosive carrier into a tubular delivery member in order that the water-based explosive defines a plurality of bodies separated from each other by the carrier. The method further includes the step of feeding the bodies of water-based explosive separated by the carrier through the tubular delivery member to a point of delivery. The invention also relates to a system for delivering a water-based explosive especially to a system for carrying out the above method.

Abstract: The present invention is directed to an improved method of blasting whereby the formation of nitrogen oxide after-blast fumes is reduced. This helps satisfy the need for better fume characteristics in blasting. The method reduces the formation of nitrogen oxides in after-blast fumes resulting from the detonation of a blasting agent in a borehole. The method comprises formulating the blasting agent to contain from about 1% to about 20% silicon powder.

Abstract: The process for sensitizing in situ aqueous explosives before charging the mine holes comprises the formation of an emulsion of dispersion gas-in-liquid from a low sensitivity or non explosive matrix product which consists of a liquid mixture in solution, emulsion or suspension of oxidant in fuel, and a gas. The density of the final explosive product can be varied as a function of the gas flow rate and can be controlled before introducing it into the hole. The installation comprises a tank (1) with the matrix product, a gas reserve (10), a mixture (5), a pump (3), and a gas flow rate regulating device (8) and optionally a tank (2) with a gas bubble stabilizing agent, a dosing pump (4) and a flow meter (7).

Abstract: An explosive system is disclosed which may be used in repair of damaged casing. In a described embodiment, an explosive system includes a flexible elongated tubular container with a liquid explosive disposed within the container. As an alternative, the liquid explosive may be flowed into a wellbore without being retained within a container. The liquid explosive is detonated in the wellbore, thereby fragmenting the damaged casing and forcing it out into a formation surrounding the wellbore.

Abstract: A method for excavating a tunnel rock face by drilling a pattern of lifter holes and line holes. The line holes ensure the grade or slope of the excavation meets specification while reducing the need for cleaning out the face. A longitudinal band of lifter holes is drilled into the tunnel face at an acute angle in relation to the substantially perpendicular reference axis emerging from the tunnel face. A series of line holes, disposed opposedly adjacent to the lifter holes, are drilled at a smaller acute angle. The lifter holes are drilled deeper than the line holes and they do not intersect. Explosives are loaded into the lifter holes. The line holes are expendable and encourage fracturing of the rock.

Abstract: A technique includes arranging perforating charges of a perforating gun into groups of adjacent perforating charges. Each perforating charge of each group is aligned in a direction associated with the group. The groups are oriented to form a phasing for the perforating gun.

Abstract: A carrier for containing explosives (e.g., shaped charges) includes a housing having a plurality of recesses, each recess having a periphery and a side surface extending around the periphery. The side surface is shaped to a geometry to reduce or control reflection of compression waves generated in response to an explosive jet (e.g., a perforating jet) created due to detonation of an explosive. The side surface may be slanted from a bottom surface of the recess, or a predetermined profile may be formed in the side surface to scatter or direct compression waves. One or more shock absorbing inserts may also be placed in recesses formed by the inserts, or the recesses may be capped to trap air so that compression waves generated in the recesses are significantly reduced as compared to compression waves generated in well fluids.

Abstract: A method for setting and igniting a charge of explosives for geological investigations, comprising the following steps: a hole (14) is drilled in the ground (12) which is to be investigated; an explosion chamber (22) is hollowed out, whereby said explosion chamber has an expanded form in relation to the bore hole (14) at the end of said bore hole (14); an ignition element (34) and an explosive container (36) containing an explosive in a protective blister (54) surrounding the ignition element are lowered down into the explosion chamber (22); the explosive (42) is pressed out of the explosive container (36) into the explosive chamber (22) and the ignition element (34) is ignited In comparison with conventional methods, the inventive method provides for a considerably smaller diameter of bore hole, whereby said bore hole is substantially easier to drill.

Abstract: The present invention relates to a method of reducing the energy of an emulsion blasting agent as it is being loaded into a borehole and to an improved method of perimeter blasting wherein an energy reducing agent is added to and mixed uniformly throughout an emulsion blasting agent as it is being pumped or conveyed into a perimeter borehole to reduce the energy of the blasting agent to a desired level. In addition, by adding varying amount of gassing agents, the density and sensitivity of the emulsion blasting agent also can be controlled.

Abstract: A tubing and casing cutter is shown which can be assembled in the field from a plurality of pressed segmented pellets of free standing explosive material. The segmented pellets have a liner glued to at least one exposed face thereof. The pellets are glued to a backup plate with two mirror image plates being stacked to form a plate assembly. A plurality of plate assemblies are stacked within a surrounding container to form the cutter. The pressed pellets can also be assembled within a cup-shaped container to form a shaped charge.

Abstract: Reinforced borehole plugs useful in the presplitting and blast removal of earth formations, the improvements provided by the invention comprising inflatable devices intended to support stemming, explosives and the like at suspended locations within a borehole to produce desired blast results. The borehole plugs of the invention comprise inflatable sport balls such as are used on playgrounds as toys and which are reinforced according to the invention to maintain inflation within a borehole, a characteristic which playground balls can only inconsistently provide. The borehole plugs of the invention are preferably inflatable through use of valve structures which permit pumping of an inflating fluid into the plugs once the plugs are respectively suspended at desired locations within boreholes prior to filling the boreholes in whole or in part with stemming and/or explosives and the like.

Abstract: Disclosed herein is a blasting apparatus for forming horizontal underground cavities and blasting method using the same. The blasting apparatus includes a metallic body horizontally formed through the center portion of a loading chamber. A delayed detonator and a shaped explosive are loaded in the loading chamber of the body. A connecting ring is formed on the body for connecting the body to a hoisting rope. The blasting method includes the step of loading a detonator lead, a delayed detonator and a shaped explosive in a loading chamber. The blasting apparatus is suspended over a vertical pit by operating a hoisting device. The blasting apparatus suspended by the hoisting rope is lowered to the entrance of a vertical pit, and a detonator lead drawn out of the body is connected to a leading wire. The blasting apparatus and the leading wire connected to the detonator lead drawn out of the body are lowered into the vertical pit at a position where fluid discharges.

Abstract: The invention uses a pair of opposed tabs on the charge holder to engage a groove in the case of the shape charge. The case is generally conical in shape. However, the front opening of the case has both a first and second circumferential ridge separated by a groove. The diameter of the groove generally matches the distance between tabs. The second ridge can have a flat milled thereon to allow case to be inserted until the tabs contact the forward or first ridge. This locates the tabs between the first and second ridges and over the groove. The case is then rotated so that the tabs are captured between the two ridges. Once installed, the detonation cord is attached to the case. The cord helps prevent any rotation of the case, thereby securing it into the charge holder. Thus, the use of easily milled tabs on the charge holder in conjunction with an easily milled groove and flats on the case provide an improved apparatus and method for securing the shape charge into the charge holder of a perforation gun.

Abstract: A carrier for containing explosives (e.g., shaped charges) includes a housing having a plurality of recesses, each recess having a periphery and a side surface extending around the periphery. The side surface is shaped to a geometry to reduce or control reflection of compression waves generated in response to an explosive jet (e.g., a perforating jet) created due to detonation of an explosive. The side surface may be slanted from a bottom surface of the recess, or a predetermined profile may be formed in the side surface to scatter or direct compression waves. One or more shock absorbing inserts may also be placed in recesses formed by the inserts, or the recesses may be capped to trap air so that compression waves generated in the recesses are significantly reduced as compared to compression waves generated in well fluids.

Abstract: A method of blasting rock or similar materials in surface and underground mining operations is described in which neighboring bore holes are charged with explosives and primed with detonators. The detonators are programmed with respective delay intervals according to the firing pattern and the mineralogical/geological environment and the resulting seismic velocities.

Abstract: The invention of the present application provides a method of controlled blasting comprising dispersing an explosive (9) within a blasthole (1) to form a dispersed explosive having a lower average bulk density than said explosive (9) prior to dispersion and detonating said dispersed explosive. Typically the explosive (9) is dispersed in air, however the explosive (9) may be dispersed in other matrices such as other gases or liquids or in gases comprising particulate matter. The explosive (9) may be dispersed using a number of different techniques such as, using a discharge of pressurised fluid or by detonation of a small propellant charge or by falling under gravity in the blasthole. The invention of the present application is particularly useful where a reduced concentration of explosive energy is required such as in perimeter control, presplitting or soft rock conditions, can be controlled by a method which involves dispersion the explosives composition (9) within a blasthole prior to initiating the blast.

Abstract: A tunnel blasting method is disclosed. The method including the step of drilling blast holes such as cut holes, cut spreader holes, floor holes and roof holes to predetermined depths and in a predetermined hole arrangement. The blast holes are loaded with one or more detonators and explosives, stemming the blast holes with stemming materials. The detonators are detonated using a triggering device. In the hole loading step, one or more air bladders are situated in each of the blast holes so that a front free surface or one or more small free surfaces are formed. As a result, a projective area toward a free surface is enlarged and a total blast pressure is increased to increase the fragmentation rate of a rock and reduce blast vibration.

Abstract: A tubular charge holder assembly for a perforating gun made of a tube having a plurality of pairs of diametrically opposed openings. The pairs of openings are formed over a length of the tube, wherein the each pair has a larger and a smaller opening. A shaped charge is located within the pairs of openings in the tubular charge holder so that at least a portion of the rim of a front face of the shaped charge extends out of the larger opening and at least a portion of a rear face of the shaped charge extends out from the smaller opening of the tube. A detonating cord is helically wrapped around the outside surface of the tube such that the detonating cord is positioned so that the cord is proximate to the rear surface of each of the shaped charges installed within the tube. A substantially semi-circular clip is positioned on the outside surface of the tube proximate each of the shaped charges.

Abstract: A cartridge containing an explosive charge is inserted at the bottom of a short hole drilled in the rock. The cartridge is held in place or stemmed by a massive stemming bar of high-strength material such as steel. The cartridge incorporates additional internal volume designed to control the application of pressure in the bottom hole volume by the detonating explosive. The primary method by which the high-pressure gases are contained in the hole bottom until relieved by the opening up of controlled fractures, is by the massive inertial stemming bar which blocks the flow of gas up the drill hole except for a small leak path between the stemming bar and the drill hole walls. The stemming bar is preferably connected to a boom mounted on a carrier. A preferred embodiment incorporates an indexing mechanism to allow both a drill and a small-charge blasting apparatus to be used on the same boom for drilling and subsequent charge insertion and firing operations.

Abstract: Disclosed herein is a center-cut blasting method for tunnel excavation. The center-cut blasting method includes the step of drilling a single central center-cut hole at the center of a center-cut region, drilling a plurality of auxiliary center-cut holes comprised of large unloaded auxiliary holes and loaded auxiliary holes that are alternately arranged around the central center-cut hole to be situated in a circle having a predetermined diameter, and drilling a plurality of spreader center-cut holes outside the auxiliary center-cut holes to be situated in concentric circles centered by the central center-cut hole. Thereafter, the center-cut holes are loaded with delay detonators and explosives and the center-cut holes are stemmed with stemming material at their entrances. The loaded auxiliary holes of the auxiliary center-cut holes are blasted so as to create a circular pre-split. After that, the central center-cut hole is blasted so as to create initial dual free surfaces.