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 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 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: 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.

Abstract: The extraction machine for underground ore extraction operations, with extraction of the extraction product by blasting has an advancing support equipment (11) and a face conveyor (18) coupled to it as well as at least one boring device (26) for the production of shot holes (23) and a loading device (27) to supply the face conveyor (18) with the blast rock loosened by blasting, whereby the boring device (26) and the loading device (27) are assigned to a common boring and loading machine (24), which can be driven along the face conveyor (18) at right angles to the direction of mining in the direction towards the rock face (20) running parallel to the direction of mining, or away from this.

Abstract: A three dimensional multi-phase tunneling method and equipments thereof, make it possible that a drilling and blasting process can be carried out simultaneously during excavating a pilot tunnel by means of tunnel boring machine (TBM), thereby is capable of reducing the period and the cost of excavation.

Abstract: The present invention is directed to a boom supporting a slide assembly. The slide assembly includes a guide track, a drill, and a stemming member for use in small charge blasting. The drill is initially moved along the guide track to form the drill hole. After the hole is completed, the drill is retracted along the guide track, and the stemming member is moved along the guide track and placed in the drill hole. After the stemming member fractures the rock, the stemming member is retracted along the guide track and the steps repeated to break new material. The stemming member has a breech and barrel that are located in the hole. The breech is either side- or front-discharging.

Abstract: A method of stemming a borehole (6) includes the steps of placing a first layer (16) of stemming in the borehole, placing a spherical body (20) in the borehole on top of the layer (16), the body being relatively incompressible and a diameter slightly smaller than the diameter of the borehole, and placing a second layer (18) of stemming in the borehole over the body. The stemming (16, 18) may be placed in the borehole either in direct contact with an explosive (8), or spaced from it by a gas bag (24) or the like form a deck (22). In accordance with an alternate application, the stemming layers (16, 18) may be placed in the borehole prior to placement of an explosive material such that it serves as backfill. Preferably, the stemming includes crushed rock and drill cuttings such as those produced during formation of the borehole. However, other available materials may also be used such as gravel.

Abstract: Rock and other hard materials, such as concrete, are fragmented by a controlled small-charge blasting process. A cartridge containing an explosive charge is inserted at the bottom of a hole drilled in the rock. The explosive charge is configured to provide the desired pressure in the hole bottom, including, if desired, a strong shock spike at the hole bottom to enhance microfracturing. The cartridge is held in place or stemmed by a massive stemming bar of high-strength material such as steel 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 cartridge incorporates additional internal volume designed to control the application of pressure in the bottom hole volume by the detonating explosive.

Abstract: The present invention is directed to a method for breaking rock and other hard materials using small-charged blasting techniques followed by a mechanical impact breaker. In small-charge blasting techniques, a gas is released into the bottom of a sealed hole located at a free surface of the hard material. The gas pressure rises rapidly in the hole until the gas pressure causes the hard material to fracture. In one embodiment, the a deeper hole is drilled and/or a small amount of blasting agent is used to cause the formation of a network of subsurface fractures while either not removing any of the rock or removing the rock with very low energy flyrock. In another embodiment, only the central portion of the face is broken and/or removed by blasting. The impact breaker is then used to complete fracturing and removal of the material.

Abstract: An apparatus and process for the production of any emulsion explosives composition and loading it into a blast hole (7) which utilize a loading conduit (4) having a shear inducing means (5) and a liquid lubrication source (b) adapted to provide a layer of liquid lubricant between the conduit (4) and emulsion explosives composition being pumped through the loading conduit (4). The conduit also comprises a mixing means (8) located at or near the outlet of the conduit (4), the mixing means (8) incorporates at least some of the liquid layer into the emulsion explosives composition.

Abstract: A portable system for drilling geophysical shot holes in mixed geologic conditions. The system includes a drill for creating a shot hole in unconsolidated soil and for maintaining gauge in mixed geologic conditions. An explosive projectile for contacting hard rock is directed by a shot barrel, and a compressed air device removes residue from the shot hole. A controller can selectively discharge explosive projectiles when the drill bit encounters hard rock, and can cease the discharge of explosive projectiles when the drill bit encounters unconsolidated soil below hard rock. The system is particularly useful in preparing a slender shot hole in remote conditions restricting the mobility of drilling equipment, and in mixed geologic conditions comprising unconsolidated soils and hard rock aggregates or base rock.

Abstract: A device for unblocking mine raises which has multiple flexible arms attached to a top hollow tube which carries the explosive material. Flexible extension poles are attached to a top hollow tube section and hollow tube sections. The flexible arms allow for easy, precise and safe positioning of the explosive material.

Abstract: A cutterhead is supported at the front part of a main frame so as to incline at a specified angle with respect to a vertical plane. The main frame includes (i) a roof support disposed at a position corresponding to where a reaction force acts in the direction of the periphery of a tunnel against a force caused by rotation of the cutterhead, and (ii) a pusher for pushing the roof support toward the cutterhead resisting the reaction force.

Abstract: The invention comprises a method of preventing afterblast sulfide dust explosions in blasting operations involving sulfide-containing ores, which method comprises (a) loading a borehole that has been drilled into a sulfide-containing ore body with an emulsion blasting agent that comprises an emulsifier, a continuous organic fuel phase, a density control agent, and a discontinuous oxidizer salt solution phase that comprises inorganic oxidizer salt(s), water and urea as a chemical inhibitor in an amount of from about 1% to about 10% by weight of the blasting agent, the blasting agent being loaded in a coupling relationship with the borehole; and (b) detonating the blasting agent.

Abstract: A method for completing a well penetrating a solid carbonaceous subterranean formation by positioning a perforating gun in an uncased portion of a wellbore penetrating the solid carbonaceous subterranean formation; perforating the coal formation; and, producing fluids and particulate coal from the coal formation through the well to form a cavity in the coal formation surrounding the well.

Abstract: Method and Apparatus are disclosed for dynamically determining the efficiency of blast design parameters at a mine site from measured machine loader characteristics whereby a microprocessor system receives signals indicative of power train and work implement linkage measurements and develops diggability ratio indices therefrom to ascertain the blast design efficiency.

Abstract: Rock slabs or pieces are broken from larger rocks or from rock formations with reduced cracking of the broken rock slabs or pieces by drilling bore holes along the desired break lines, placing detonating cord into the bore holes, filling the bore holes with a shock transmitting and moderating composition, and detonating the detonation cord. The shock transmitting and moderating composition is preferably a gel with shock absorbing material such as microspheres suspended therein.

Abstract: A non-explosive rock breaking method is disclosed. The method is accomplished by first drilling a hole into a rock. A charging system is then positioned adjacent the hole and a propellant cartridge is inserted within the charging system. The propellant cartridge contains a propellant and means for igniting the propellant. Finally, the propellant cartridge is forced through the charging system and into the hole to ignite the propellant. A cartridge and apparatus for performing the method are also disclosed.

Abstract: The present invention is directed to a method for breaking rock and other hard materials using small-charge blasting techniques followed by a mechanical impact breaker. In small-charge blasting techniques, a gas is released into the bottom of a sealed hole located in a free surface of the hard material. The gas pressure rises rapidly in the hole until the gas pressure causes the hard material to fracture. The impact breaker is then used to complete fracturing of the material and to remove the fractured material.

Abstract: The present invention is directed to a cartridge for use in fracturing materials, such as rock. The cartridge includes a base member, a body member, a propellant, and a device for sealing a surface of the cartridge to the surface of a hole in the material. Upon ignition of the propellant, gas pressure rapidly rises in the hole due to the sealing device. The gas pressure causes the material to form a penetrating cone fracture. Various cartridge configurations are presented depending upon the specific needs of each application.

Abstract: This invention is in the field of perforating gun systems used, for example, to gain access to underground oil and gas formations. In particular, this invention relates to an expendable holder assembly for shaped charges of such systems.

Abstract: The present invention relates to a method for forming a parallel bore hole and a slant bore hole (or V-shaped V bore hole) together within the same area of a working face, and then blasting the working face by using a delay electric detonator. The method of this invention includes the steps of drilling a number of V holes at a predetermined angle in a horizontal angle cut pattern or in a vertical angle cut pattern about the central zone of a working face, drilling a number of parallel cut hole within a projective area of the above mentioned slant holes; loading an electric detonator in the slant holes and an explosive material by indirect priming in the parallel cut holes up to the bottom of the slant holes; blasting the slant holes to form a slant free surface; blasting a center cut hole out of the parallel cut holes to form two free surfaces having a funnel shape; and sequentially blasting a middle cut hole and an outer cut hole out of the parallel cut holes to form a cubical space.

Abstract: A non-explosive rock breaking method. The method is accomplished by first drilling a hole into a rock. A charging system is then positioned adjacent the hole and a propellant cartridge is inserted within the charging hosing. The propellant cartridge contains a propellant and means for igniting the propellant. Finally, the propellant cartridge is forced through the charging hose and into the hole to ignite the propellant. A cartridge and apparatus for performing the method are also disclosed.

Abstract: When driving a tube (24) into the ground, primarily for subsequently loading the tube with an explosive substance and subsequent blasting of the surrounding ground, a driving rod (20) whose rear end is provided with an insert end (13) which can be connected to a percussion machine (36) is employed in the driving operation. The non-metallic tube (24) is fitted over the driving rod (20), against an axial stop (16). A forwardly located, conical sacrificial tip (28) has a base cross-section dimension (30) which corresponds to the outer dimension of the tube (24), followed by a neck portion providing a shoulder (31). The tip (28) is supported by the shoulder (31) with clamping engagement with the tube in an orifice of the tube, and forms, together with the tube (24), a unit (24, 28) which is fitted onto the driving rod (20) and brought into impact contact between an anvil surface (33) on the tip (28) and the forward end (21) of the device.

Abstract: An improved method and equipment of removing a minable product, such as coal, from an underground seam of minable product, such as a coal seam, includes the steps of drilling a vertical hole from the earth's surface through the seam of minable product, installing in the recovery hole an improved recoverable down hole tool, having a vertical auger and a hollow shaft extending from the earth's surface to the auger in the down hole tool, water pumped down the hollow shaft exiting through nozzles mounted from below the auger segments in the down hole tool and spaced vertically along the length of the hollow shaft to the earth's surface through the seam of minable product, the injection holes being drilled in a pattern extending from the recovery hole inserting and sequentially igniting explosives in the injection holes, injecting water sequentially in the injection holes and removing the fractured minable product by operating the down hole tool and water nozzles in the recovery hole and raising said minable produ

Abstract: A guidance system and method for keeping a tunnel boring, machine continuously on a plan line. The guidance system requires no machine operator calculations and provides the boring machine operator with a graphic display of past, present and projected positions of the boring machine from a horizontal and vertical perspective. The system uses a laser beam transmitter placed to the rear of the tunnel boring machine along with a front opaque target with a horizontal and vertical cross-hair and a rear transparent target with a horizontal and vertical cross-hair. The front and rear targets are disposed on the front and the rear of the boring machine. Also, an on-board programmable computer is installed on the boring machine for imputing data as to horizontal offset and vertical offset readings from the front and rear targets as the boring machine advances forward. Typically the boring machine moves forward in increments of four feet with offset readings taken by the operator after each increment.

Abstract: The present invention is a system for severing pipe. The system includes an explosively actuated pipe cutter, a pressure actuated initiator, and a means for suspending the cutter and the initiator inside the pipe and pressure sealing the interior of the pipe.In a particular embodiment of the invention, the initiator includes a time delay to enable reduction in pressure applied to the interior of the pipe for actuating the initiator.

Abstract: An object of this invention is to improve precision in the operation, operating efficiency, and reliability of an excavator. A soil condition at a place where an excavator (1) is advanced is inputted, and a reference number of revolutions of a cutter (9) and a reference advancing speed of the excavator (1) are set in correspondence with the inputted soil condition. Meanwhile, a load on each actuator (17, 18) is detected. The actuator (18) for rotating the cutter is controlled so as to allow the set reference number of revolutions to be obtained for the cutter (9). In a case where the load on each of the actuators (17, 18) is within a predetermined range, the actuator (17) for advancing is controlled so as to allow the set reference advancing speed to be obtained for the excavator (1).

Abstract: A rock breaker uses shotgun cartridges or other firearm ammunition as the explosive charge at the bottom of a drilled borehole. The breaker includes a heavy steel rod or bar, a gun with a firing chamber for the ammunition which screws onto the rod, a long firing pin running through a central passage in the rod, and a firing trigger mechanism at the external end of the bar which strikes the firing pin to fire the cartridge within the borehole. A tubular sleeve surround the main body of the rod and includes slits the end to allow it to expand. The rod has a conical taper at the internal end against which the end of the sleeve expands when the sleeve is forced along the rod toward the taper by a nut threaded onto the external end of the rod. As the sleeve end expands, it pushes against the borehole and holds the explosive gasses within, and also prevents the breaker from flying out of the borehole.

Abstract: A device for generating a shockwave for initiating detonation of a main explosive charge and a method for producing same are provided. A device according to the instant invention is capable of producing a more planar wave front than is possible according to the prior art. Also, the wave front generated by such a generator flattens out in less time than in the prior art, and therefore the weight and axial length of a warhead equipped with a generator according to the instant invention may be substantially reduced without a corresponding reduction of the detonator's explosive yield.

Abstract: A method and apparatus for perforating a formation surrounding a wellbore and initiating and propagating a fracture in that formation to stimulate hydrocarbon production from the wellbore. The technique uses a perforation and propellant loading device which perforates and fractures in a single operation to greatly increase the efficiency over current perforation techniques. Efficiency is increased by a number of factors including firing the perforating shaped charge through a gas zone, reducing the overall perforation damage to the formation, increasing operation speed, and increasing pressure in the area of the borehole surrounding the production zone before perforation and propagation are initiated. In accordance with the invention, the timing of the propellant ignition and charge detonation are critical to achieve the desired results.

Abstract: Mining apparatus is disclosed in which a cutting wheel supporting a plurality of roller-cutters rotates about a horizontal axis and is supported on a slewing boom for cutting a tunnel with a flat floor and roof and elliptical walls as it slews across a mining face. The slewing boom is supported on a main beam assembly, the front end of which rests on powered crawler tracks and the rear end of which passes through a gripper assembly which may be clamped between the floor and roof of the tunnel, and against which the main beam assembly may be urged forward for engaging the roller-cutters with the mining face. A preload crawler is urged against the roof of the tunnel above the powered crawler tracks to locate the main beam assembly rigidly relative to the tunnel such that the roller-cutters may cut the rock in the mining face with minimal loss of cutting force due to vibration.

Abstract: Rock and other hard materials, such as concrete, are broken by a controlled-fracturing process referred to as penetrating-cone fracture. The fracturing process is accomplished by pressurizing the bottom of a drill hole in such a way as to initiate and propagate a controlled fracture from the sharp hole-bottom corner while not crushing the surrounding rock. A cartridge containing a propellant charge is inserted at the bottom of a short hole drilled in the rock. The cartridge is stemmed by a massive bar. A firing pin in the stemming bar strikes a primer which then ignites the propellant in the cartridge. The cartridge incorporates a relief volume designed to control propellant burning rates and pressures and thus the pressure at the hole bottom. The cartridge is designed with a tapered wall, which is thicker nearer the stemming bar, and with a large radius of the inside surface of the cartridge base, which reduce the possibility for premature cartridge rupture and loss of propellant generated gases.

Abstract: There is disclosed a method and an apparatus for easily controlling the advancing direction of an excavating machine without causing the excavating machine to largely trace in a zigzag way. The direction control is done by the steps of mounting a reflector on a head portion of a shield body so as to receive a light beam directed along an imaginary reference line, mounting a target on a tail portion of the shield body so as to receive the reflected light beam from the reflector, controlling means for correcting the direction so that the reflected light beam may be irradiated at an objective position within the target, and thereby controlling the advancing direction of the excavating machine so that a subjective portion at the front end of the head portion may follow along the reference line.

Abstract: A method for controlling advancement of a drilling apparatus comprising a drill head having tools therein and at least one conveying tube is disclosed. The method utilizes changes in pressure sensed in the drill head or the conveying tube as a means for assessing forces acting on tools in the drill head. The measured pressure information is transmitted to control equipment which adjusts the driving force applied by a power unit to the apparatus to effect the drilling operation. The method thereby provides an effective means of preventing damage to the tools.

Abstract: A main charge of explosive is positioned symmetrically about a passageway-forming tubular member, such as a well pipe assembly. The charge is outwardly and radially spaced from the member and is coupled thereto by a dense medium, such as soil, which is adapted to transfer the produced explosive energy to the tubular member in the form of a pressure pulse applied by the medium. Initiation charges are supplied at the outer surface of the main charge, to initiate a detonation wave directed at the tubular member. A layer of dense medium is provided to confine the non-coupled surface of the charge and retard venting of explosive gases away from the tubular member. In the end result, concentrated, converging pressure pulses are applied to the tubular member on detonation, to cause it to be symmetrically crimped to restrict the passageway.

Abstract: A method for breaking a longer round more efficiently in a full face of rock, to construct shafts or tunnels. In the method a relief hole having at least a 200 mm diameter and at least a 15 to 18 foot depth is drilled. Primary and secondary blast holes are drilled about the relief hole, approximately axially parallel to the relief hole. Most of the blast holes are drilled simultaneously with the relief hole. The relief hole is drilled by an in-the-hole (ITH) hammer drill, which if necessary is removed after drilling the relief hole, to allow blast holes to be drilled immediately adjacent the relief hole. The relief hole is drilled at least 10 to 15 percent deeper than the blast holes. Explosive charges are then inserted into the relief hole and most of the blast holes and are detonated in sequence.

Abstract: An improved non-viscous aqueous dust control solution which includes a polyvinyl alcohol and boric acid. The improved solution may be spray applied or applied as a foam. The solution may include cross-linking agents, extenders, plasticizers or surfactants.

Abstract: Coal and other mineral seams are uncovered to a desired width or "cut" by blast casting a portion of the overburden material above the seam into an adjacent pit portion followed by moving a dragline or other excavating apparatus onto a bench surface below the bench height of the unblasted overburden and building an extended bench portion with overburden material from above the seam to be uncovered. The excavating apparatus then moves onto the extended bench and removes overburden material from directly above the seam to a final spoil pile. The excavating apparatus may be returned to the start of the next cut by a return road, by building a return road along the spoil pile or by reversing its direction over the extended bench to uncover the seam.

Abstract: There is disclosed, according to the present invention, an apparatus and method for loading explosives exhibiting little water resistance into water filled blast holes without contamination of the explosives by water. A pressure charger vessel, capable of being filled with bulk explosives of low density and low water resistance, such as ammonium nitrate fuel oil, is connected to a flexible plastic sleeve. A pneumatic plug fixedly connects the lower portion of the pressure charger vessel to the plastic sleeve. The plastic sleeve is lowered into a blast hole by means of a weight. Compressed air is then introduced into the pressure charge vessel and a valve means located between the sleeve and the pressure charger vessel is opened, permitting pressurized ammonium nitrate fuel oil to be pushed downwardly into the flexible plastic sleeve. Projections and recesses on the outer surface of the plastic sleeve facilitate the expulsion of water from the blast hole.

Abstract: A shield tunnelling apparatus is provided that includes a first tubular shield body in which a cutter assembly for excavation and a drive mechanism for driving the cutter assembly are disposed; a second shield body connected to the rear of the first shield body so as to have a common axis therewith; a target disposed in the first shield body so as to receive a light ray directed along the axis; first optical path changing means disposed in the second shield body and capable of changing the optical path of the light ray directed toward the target such that the light ray travels along an optical path displaced away from the axis; and second optical path changing means disposed in the second shield body and capable of changing the optical path of the light ray passing through the first optical path changing means such that the light ray is again directed along the axis.

Abstract: The invention relates to a device and process which utilize the Doppler effect for measurement of the performance of blasting operations, in particular to the measurement of face velocity. The measuring device comprises radiation generating and receiving means and a signal analyzing means.

Abstract: Coal and other mineral seams are uncovered to a desired width by blast casting a portion of the overburden above the seam into an adjacent spoil pit, followed by excavation of a keycut between unblasted overburden and a plug portion of the overburden remaining above the seam and adjacent to the spoil pit. The excavated material forms a temporary spoil pile adjacent to the plug portion and covering the blast cast overburden. The plug portion and the temporary spoil pile are reshaped to form a support pad for the excavating apparatus which is moved onto the pad and then excavates the plug portion and reshaped temporary spoil pile to form a spoil pile laterally spaced from the pad so as to uncover the remaining uncovered portions of the seam.

Abstract: A method of removing a mineable product, such as coal, from an underground seam of mineable product, such as a coal seam includes the steps of drilling a vertical hole from the earth's surface through the seam of mineable product, installing in the recovery hole a vertical auger and a pipe extending from the auger to the earth's surface, drilling a plurality of closely spaced apart injection holes from the earth's surface through the seam of mineable product, the injection holes being drilled in a pattern extending from the recovery hole, inserting an explosive in the seam of mineable product where penetrated by each of the injection holes, sequentially igniting the explosive in each of the injection holes to blast fractured mineable material from the seam, injecting water sequentially in the injection holes to move fractured mineable material toward the recovery hole and operating the auger to raise to the earth's surface the fractured mineaable product that has been blasted from the seam.

Abstract: In a method and a device for introducing granular or pulverulent explosive into drill holes the introduction is suitably carried out by means of a hose like or tube like conduit (2) introducable into the drill hole, the explosive being transported through the conduit, e.g. with pressurized air. To obtain an explosive power reduced in relation to that obtained by complete filling of the drill holes with the explosive, only partial filling of the drill holes is carried out by eithera) providing the conduit (2) with a tool (12), which on withdrawal of the conduit out of the drill hole leaves an air filled cavity in the drill hole, orb) arranging in the drill hole elongated filler means (24) and carrying out feeding of the explosive while said means is located within the drill hole.

Abstract: A system for inspecting a forward end portion in a tunneling machine including cutter bits and a chamber such as a tunnel boring machine or a shield tunneling machine. The system includes an apparatus for inspecting a forward end portion comprising at least one through hole provided on the partition wall for defining a chamber, an elongate member slidably and rotatably inserted into the through hole, an image sensor positioned at a forward end of the elongate member for observing a cutter bit or the inside of the chamber, an image display provided in the main body for displaying an image from the image sensor, and a connection for connecting the image sensor and the image display. The system also includes a method for inspecting a forward end portion comprising the steps of defining a cavity in the chamber or in the vicinity of the cutter bits by supplying compressed air, inserting an image sensor into the cavity, and observing the inside of the chamber or the cutter bits using the image sensor.

Abstract: The present invention relates to a method for excavating and preparation of rock cavities and then substantially spherical rock cavities or rock cavities having spherically shaped parts, such as dome-shaped ceilings, which rock cavities are intended as shelter, for the storage of solid or liquid products or for production plants in rock, whereby one drills a first series of radially outwardly extending holes (6) from a first distance (4) from one or more shafts/tunnels (3, 13, 14, 15, 16), preferably radially arranged from the center of a sphere projected; that one drills a second series of radially outwardly extending holes (8) from a second, far more out arranged distance (7) from the center, which holes (8) extend outside the holes of the first series; that one drills a third series of radially outwardly extending holes (10) from a third, further far more out arranged distance (9) from the center, which holes (10) extend outside the holes (8) of the second series; that optionally further series of holes (1

Abstract: Hard compact materials, such as rock, concrete, et cetera, are broken by igniting an appropriately designed explosive or propellant charge placed within the hole or carried in a special charge-containing device with a short barrel which is inserted and sealed into a pre-drilled hole of particular geometry. One or more approximately cylindrical holes are drilled into the material to be broken by conventional drilling, such as used in the mining and construction industries. The holes have a relatively short depth to diameter ratio, being in the range of about 2:1 to 6:1, and preferably about 3:1 to 5:1. The holes are percussively drilled with microfractures in and around hole bottoms to provide fracture initiation sites at the hole bottoms so as to provide preferred fracture initiation roughly parallel to a free surface of material being excavated.

Abstract: A blasting device for unblocking ore passes, backfill raises, mine draw points and any other near vertical raises where rocks or other materials normally fall freely but may get blocked during use, comprises a propulsion unit including an air chamber mounted at the end of a hollow tube and having an inlet for receiving pressurized air and at least one outlet for allowing compressed air jets to exit downwardly from the air chamber to propel the propulsion unit upwardly, a reservoir mounted on the propulsion unit and adapted to hold explosive and an igniter, means for feeding pressurized air into the air chamber through the hollow tube, and an ignition line connected to the igniter for igniting the explosive from a distance.