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Publication numberUS3721471 A
Publication typeGrant
Publication dateMar 20, 1973
Filing dateOct 28, 1971
Priority dateOct 28, 1971
Publication numberUS 3721471 A, US 3721471A, US-A-3721471, US3721471 A, US3721471A
InventorsO Bergmann, D Coursen
Original AssigneeDu Pont
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Drill-and-blast module
US 3721471 A
Abstract  available in
Images(3)
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Claims  available in
Description  (OCR text may contain errors)

United States Patent 1 Bergmann et al.

[ 1March 20, 1973 [54] DRILL-AND-BLAST MODULE [75] Inventors: Osvvald Ri Bergirialin, Township, N.J.; David L. Coursen,

Newark, Del.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

[22] Filed: Oct. 28, 1971 [21] Appl. No.: 193,323

Related 1.1.8. Application Data [62] Division as. No. 878,005, Nov. 19, 1969.

[52] US. Cl. ..299/55, 102/23, 299/13 [51] Int. Cl. ..E21c 37/00 {58] Field of Search ..299/l3, 55, 56, 64; 102/22,

[56] References Cited UNITED STATES PATENTS 3,362,329 1/1968 Epstein ..102/70.2 A 3,408,937 11/1968 Lewis et al. ....l02/70.2 A 3,511,538 5/1970 Guenter ..299/13 Primary Examiner-Ernest R. Purser AttorneyJames J. Flynn [57] ABSTRACT Working, e.g., excavating, a geological mass by a succession of substantially continuous drill-1oad-b1ast sequences, each sequence comprising drilling a hole in the mass, placing a charge of condensed secondary explosive in the hole, and initiating the charge by projecting propagative energy, e.g., the kinetic energy of a high-velocity projectile, through an inactive medi- 9 Claims, 10 Drawing Figures 21,471 PATENTEDmzoms 3 7 sum ear 3 DRILL-AND-BLAST MODULE This application is a division of U.S. Pat. application Ser. No. 878,005 filed Nov. 19, 1969.

BACKGROUND OF THE INVENTION This invention relates to an improved drill-and-blast process wherein a secondary explosive charge is loaded into a drill hole and then initiated therein by the rapid release of energy projected to the charge through an inactive medium, e.g., the atmosphere, and to a drill-andblast module useful for carrying out the process in a rapid, cyclic manner,

Drill-and-blast processes have long provided man with a powerful tool for performing useful work, affording the energy required, for example, for excavation operations of various kinds, i.e., operations in which material is dug out and removed at or below the earth's surface either to form a useful cavity, e.g., in tunneling, or to derive profit from the removed material, e.g., in mining. The explosive energy afforded by drill-and-blast processes also has been utilized for other purposes, e.g., in seismic prospecting, to provide information regarding the location of useful geological strata, such as gas or oil-bearing strata. At the present time there is an ever-increasing need for prospecting and excavation operations, and especially for underground excavations, e.g., for constructing water and vehicle tunnels, parking spaces, and military defense sites, and for exploiting very large mineral deposits under conservation constraints. However, significant reductions incost and increases in the sustained rate of working, e.g., tunnel advance, are needed if prospecting and excavation are to be utilized effectively to meet the cha'llenges of urbanization and natural resource conservation.

In the conventional drill-and-blast method of working a geological mass such as rock for excavation thereof, holes are drilled in a predetermined pattern in the rock; after all of the holes have been drilled, a secondary explosive charge is loaded therein, usually by hand; an initiating device, i.e., a blasting cap or primer, is placed in contact with the charge in each hole, or with detonating cord leading to the charge, and connected to a remotely located common actuating device such as a blasting machine; and the charges thereafter are initiated by energizing of the actuating device. In underground excavation, after a ventilation period or smoke time, which is necessary to clear the airborn fumes and dust produced as a result of such a blast, the round is concluded with the mucking operation, i.e., the loading and transporting of the disintegrated material (muck) from the excavation to a disposal area. This cycle is then repeated.

In recent years, mechanical excavators, or moles, have been developed which are capable of boring a tunnel or shaft, or mining out ore, by means of a rotat ing cutterhead driven by electric or hydraulic motors, the muck being picked up by a wheel which discharges it onto a belt conveyor that carries it back behind the machine. At their present respective levels of technological development, mechanical excavators have a greater driving capability per day in weak and medium-strength rock than the drill-and-blast method. This is due chiefly to the fact that the mechanical method involves a near-continuous operation, although delays are encountered because of changes in geological conditions, mechanical and electrical failures, the need for frequent cutter changes, etc.

There are serious limitations to the use of mechanical excavators, however. One of these is that mechanical excavators cannot be used effectively in hard and/or abrasive rock, e.g., rock having a compressive strength of more than about 15,000 psi or a Mohs Scale hardness greater than about 5. Rock of this nature is presently encountered in about one-third of the excavation projects, and it is expected that this percentage will increase as future public construction demands force excavations to be made at greater depths and in areas of known hard-rock conditions. A second limitation is that the initial investment in mechanical excavators is high, and consequently their use in many short tunnels cannot be economically justified even though the excavator would be technically capable of driving the tunnel. Furthermore, investment in a new excavator usually is necessary in each mechanical tun nel-driving project because the different diameter requirements and geological conditions encountered from project to project necessitate the designing of a machine for each individual tunnel, even though machines which have been used in completed projects may still have some useful life. With respect to mining operations, continuous mining machines sometimes are too large and inflexible to permit the efficient mining of narrow ore seams. For reasons such as these, the drilland-blast method of excavation is the method of choice in many operations at the present time.

As now practiced, however, the drill-and-blast method of excavation has inherent delays in each cycle which cause the rate of heading advance, or driving capability per day, to be low. The low rate of advance, requirement of large labor crews, and costs of expended materials make the total excavation costs high. Cycle delays and high manpower requirements are inherent in the procedures presently employed to prepare the formation for the disintegration step, i.e., the blast, and by the condition of the environment in the work area during and after blast. The preparative operations include moving the drilling equipment up to the face, drilling the holes, moving back the drilling equipment, charging the holes with secondary explosive, placing assemblies (i.e., blasting caps) containing primary explosive charges in contact with the secondary explosive, or in contact with detonating cords leading to the secondary explosives in the holes, and connecting the assemblies that contain primary explosive charges to a source of energy so that a continuous energy-storing, as well as energy-transmitting, circuit is formed from a remotely located common energy source, e.g., a blasting machine or power line, to the secondary explosive charges. The initial energy, e.g., an

electrical pulse emitted by the common energy source,

thus is transmitted to the secondary explosive through an active medium, i.e., one containing stored energy (the primary explosive), which is used in turn to initiate the secondary explosive.

Because of the time required to drill, load, and otherwise prepare the holes for blasting, it has been necessa ry, in the interest of efficiency, to design the rounds (the drill hole arrangement at the face) to pull large cross-sectional areas of the face in one blast, e.g., the full crosssectional area (full-face method), or a large part of it (top heading and bench method). Rounds of this size require a large number of drill holes and consequently the detonation of a large number of explosive charges. For example, for a full-face round in a typical railroad tunnel 28 feet high and 21 feet wide, about 900 pounds of explosive may be detonated per round. Because of the pressure and rock-throw effects resulting from blasts of this magnitude, the immediate blast area must be cleared of personnel and equipment. This is the reason why remote emission of the initiation pulse, and therefore connection of all of the charges into an energy-transmitting circuit, have been necessa- Large single blasts such as have been employed heretofore can produce strong ground vibrations which may be detrimental to surrounding structures. In addition, such blasts produce large quantities of airborn fumes and dust which must be exhausted before personnel can move in with mucking equipment. Usually fans must be operated for a period of at least about twenty minutes to clear the area so that work can be resumed. After the smoke time, the mucking machine is moved in, the round is mucked out, and the mucker is moved out.

Drilling procedures have been made more efficient in recent years with the introduction of modern drilling machines, such as pneumatic percussive drills mounted on a drill jumbo (a mobile work platform), and drill hole loading time has been reduced considerably with the availability of such devices as a pneumatic cartridge loader having a semiautomatic breech-piece for feeding cartridges into a loading tube continuously, and a robot loader for moving the tube in the drill hole. However, the efficient use of equipment and manpower still has necessitated large-round blasts, and delays therefore have remained considerable owing to the time required for moving the drilling equipment up to the face to be blasted; moving it back before the blast; moving the loading personnel and equipment in and out; performing the manual operations of connecting the blasting leads (cap leg wires, or lengths of detonating fuse or safety fuse) to form a blasting circuit to the remote actuating device; and smoke time.

The use of blasting caps in a remotely actuated large blasting circuit to initiate the charges in the drill holes in drill-and-blast processes thus can be seen to be uneconomical from the viewpoint of expenditure of time and manpower. In addition, since the caps are consumed in the blast, their cost also is a factor to be considered. Also, with respect to safety considerations, the use of blasting caps is not entirely without risk since they contain a primary (high sensitive) explosive charge adjacent to a less-sensitive secondary explosive base charge, thereby forming a continuous reaction train from the primary explosive in the cap to the secondary explosive charge in the drill hole when the cap has been placed in initiating position. Thus it is most important to guard against accidental ignition of the ignition charge, adjacent to the primary explosive charge, in the positioned cap as well as in caps located in a storage area or in transit to the charge in the drill hole. Also, because of the interdependency of all of the charges in a round with respect to electrical initiation, once they have been connected, accidental generation of voltage at any one location in the electric circuit is likely to set off all of the charges. Apart from considerations of safety and materials cost, however, another serious drawback to the initiation methods now employed in blasting is that they are not amenable to mechanization and efficient operation in small blast cycles and, consequently, represent a formidable barrier to the performance of drill-and-blast operations on a rapid, near-continuous basis, i.e., in a substantially continuous cyclic succession of uninterrupted drill-loadblast sequences, a manner of operation which obviously is the most reasonable approach to decreasing cost and time. Such mechanization and small-blastcycle operation not only would greatly increase the efficiency of drill-and-blast excavation operations, but also would provide an efficient means of utilizing 'the drill-and-blast technique for the common-depth-point method of seismic prospecting. Particularly in areas where the surface layer (e.g., fractured rock, coral, unconsolidated ice or frozen ground) strongly absorbs seismic energy, the use of explosives in drill holes in the latter method would provide higher-energy signals and information concerning deeper layers than the gas exploders currently in use.

SUMMARY OF THE INVENTION This invention provides an improved drill-and-blast process in which secondary explosive charges confined in drill holes in a geological mass to be worked, e.g., rock, are initiated by the rapid release therein of energy projected to the charges in the drill holes through an inactive medium, e.g., the atmosphere, rather than via a continuous reaction train containing a primary explosive. More specifically, the process of this invention comprises performing a succession of substantially continuous drill-load-blast sequences, each sequence at a single location in the mass different from the locations where other sequences are performed, and each sequence comprising the steps of (a) drilling a hole in the mass; (b) placing a charge of condensed secondary explosive in the hole so that the explosive is confined and supported by the wall of the hole; and (c) initiating the explosive charge in the hole by projecting propagative energy, e.g., the kinetic energy of a high-velocity projectile, through an inactive medium, e.g., the atmosphere, to the charge from a location which confronts, and is separated from, the hole in a manner such that energy is released into the charge at a rate sufficiently high to cause detonation thereof. Preferably, and especially when the process is an excavation process, the succession of sequences is also substantially continuous, i.e., the process is comprised of substantially continuous drill-load-blast sequences in substantially continuous succession.

Propagative energy is energy which derives from the intensity and time dependence of the dynamic physical phenomena utilized to transport it from one place to another, e.g., the energy which derives from the intensity and time dependence of an electromagnetic field or of shock wave pressure, the velocity of a projectile, etc.

The term inactive medium, as used herein to describe the environment through which the propagative energy is projected to the charge, denotes a medium, e.g., the atmosphere, which contains no stored energy of its own, thus making no energy contribution to the initiation process. Thus, the energy is projected into the charge in the absence, or without the intervention, of a primary explosive in a physically continuous reaction train with the charge, or, more specifically, in the absence of a blasting cap.

A sequence" as used herein denotes a drill-load (charge placementyblast (charge initiation) operation at a given location (drilling a hole, loading the same hole with explosive, and initiating the explosive in the same hole). The sequence is followed by one or more other such sequences at different locations, thereby producing a succession of sequences or cycles.

The term substantially continuous, when used herein to describe the drill-load-blast sequences, means that the steps of the sequence follow closely one upon the other without the intervention of additional steps which are not directly concerned with operations performed on the mass being worked. For example, the sequences are not interrupted for the length of time required to move vehicular equipment back away from the formation and move different equipment up, con nect blasting leads to the explosive charges, and move all equipment and personnel out of the area to a remote position. A substantially continuous sequence in the present process typically is one in which the total dead time," i.e., the time between drilling and charge placement steps plus the time between charge placement and charge initiation steps, is only on the order of 5 minutes or less.

The term substantially continuous when used herein to describe the succession of sequences in a preferred embodiment, has generally the same connotation as described above for continuity of sequence steps. That is, sequence follows closely upon sequence, either before or after completion of the previous sequence, from the first to the last in the succession, without delays or interruptions between the last step of one sequence (blast) and the first step of the next (drill) to exhaust the area of fumes or move equipment up to the mass from a remote position. A substantially continuous succession of sequences in the present process typically is one in which the dead time," i.e., time between sequences, is less than about minutes, dead time between sequences in the present process, when used for excavating, usually being much less, i.e., less than about 1-2 minutes.

In a most efficient embodiment of the process, a number of sequences are carried out substantially concurrently as a group or set of sequences, followed by one. or more other such groups in, usually substantially continuous, succession. In this case, each cycle of the cyclic process or succession is a cycle of groups of sequences. The term substantially concurrently as applied herein to the performance of the sequences in a group denotes that all of the sequences are begun and completed over a selected time period after which another cycle begins. The term is not used to imply that the same step is carried out in every sequence of the group at precisely thesame time.

All drill-load-blast sequences, and preferably also cyclic successions of sequences or groups of sequences, are carried out substantially continuously, as explained above. However, the specific time employed per sequence and succession, and the time pattern in which the sequences are performed relative to other sequences can vary depending on such factors as the equipment available, working space available, etc. One

or more drills, one or more explosive loaders, and one or more energy-projecting devices can be employed.

For carrying out the process more rapidly and efficiently, especially in constricted areas, a novel drilland-blast module also is provided by the present invention, the module comprising, in combination,

a. drilling means comprising an elongated member,

e.g., a drill steel, having a bit at one end, and positioned on support means in axially movable relationship therewith;

. explosives-delivery means for delivering explosive into a hole made by the drilling means, the explosives-delivery means being positioned on support means in axially movable relationship therewith and in predetermined alignment with respect to the drilling means, the explosives-delivery means comprising a tube having one discharge end and an explosives feed end; and

0. means for projecting energy, e.g., a gun, for initiating explosive delivered into a hole by the explosives-delivery means, the energy-projecting means being positioned on support means in predetermined alignment with the drilling means and explosives-delivery means; the drilling means, explosives-delivery means, and energy-projecting means being (1) supported in a manner such that the bit of the drilling means, discharge end of the explosives-delivery means, and energy-exiting end of the energy-projecting means, e.g., a gun muzzle, are located near a common, operating end, and (2) positioned, or adapted to be positioned, in a manner such that the energy-projecting means projects energy on a path that leads into an explosive charge delivered by the explosives-delivery means into a hole drilled by the drilling means; the movable relationship of the drilling means and explosives-delivery means with the support means being such that the bit of the drilling means and the discharge end of the explosives-delivery means extend sequentially beyond all other components of the module in an axial direction at the operating end.

The module, when positioned near a mass of material to be blasted, e.g., a rock face or the earths surface, and suitably energized, in rapid sequence drills a hole in the material, loads explosive into the hole, and initiates the explosive by the projection and release of energy into the explosive, preferably by projectile impact, and can repeat the sequence at any desired number of other locations. For this reason, the three working components, i.e., the drilling means, explosives-delivery means, and energy-projecting means, are positioned, or adapted to be positioned, in a manner such that the explosives-delivery means delivers explosive into a hole made by the drilling means, and the energy-projecting means projects energy on a path that leads into the explosive in the hole. In other words, the longitudinal axes of the drilling means, explosivesdelivery means, and energy-projecting means pass, simultaneously or sequentially, through substantially a common point in space located a desired distance outside the module near the operating end corresponding to the location at which the drill bit initially penetrates the formation, i.e., at the mouth of the drill hole. By substantially a common point we mean that at the desired location outside the module, i.e., at the mouth of the drill hole, on a normal to the drill axis the three longitudinal axes all pass through the same point, or the axes of the explosives-delivery means and energy-projecting means pass through points which are within one drill hole radius from the point through which the drill passes (i.e., on the axis of the drill hole). This passage through substantially a common point may be accomplished by positioning the three working components on axes which converge at the desired point, or by providing positioning means, e.g., an indexing mechanism, to cause the axes substantially to coincide sequentially. The converging non-coincidable design, while feasible, is not preferred, however, since it requires a precise positioning of the module with respect to distance from a point on the mass to be worked and precise maintenance of the same distance through the entire drilling, loading, and initiation sequence. Therefore, in a preferred embodiment, the support means cooperate(s) with a positioning means adapted to sequentially position, e.g., by pivoting and/or sliding, the drilling means, explosives-delivery means, and energy-projecting means on substantially a common longitudinal axis.

The longitudinal axes of the drilling means, explosives-delivery means, and energy-projecting means which sequentially coincide or converge as described are the longitudinal axis of the elongated member, e.g., the drill steel, to which the bit is attached, the longitudinal axis of the bore of the delivery tube, and the axis along which the energy is projected from the energyprojecting member, e.g., the longitudinal axis of a gun bore.

The term module is used herein to denote an apparatus which is a functional unit or assembly of components adapted to be operative as a unit within a larger assembly in which it can be interchanged with another such unit and, if desired, operated together with other such units.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing, which illustrates specificembodiments of the invention,

FIGS. 1 through 4 are longitudinal cross-sectional views of a typical module of this invention through a given, substantially vertical plane (with respect to the horizon) at different times;

FIGS. 1A through 4A are cross-sectional views of the module shown in FIGS. 1 through 4, respectively, as observed through a given vertical plane substantially normal to the plane of view of FIGS. 1 through 4 and intersecting said plane at the location indicated by dotted line A-A' and viewed in the direction of the arrows;

FIG. 5 is a longitudinal cross-sectional view of a portion of a module of this invention in which the energyprojecting means differs from that shown in FIGS. 1 through 4; and

FIG. 6 is a front, partially plan, view of a face in a geological mass being worked in small blast cycles according to the process of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present process, charges of condensed secondary explosive are confined in drill holes and thereafter are initiated, each by rapidly releasing energy into the charge by projecting propagative energy to the charge through an inactive medium, e.g., theatmosphere. This mode of initiation is differentiable from those which employ a primary explosive in a continuous reaction train with the charge, and from that which is employed in drill-and-blast processes are commonly practiced, i.e., the initiation of the charges in all of the drill holes by a common energy emission, i.e., an electrical pulse or flame, generated remote from the drill holes, the multiple charges having previously been joined together in a single energy-transmitting circuit. Use of the method of initiation employed in the present process eliminates the time-consuming operations required to prepare conventional electrical or nonelectrical blasting circuits, reduces man-power requirements, and permits excavation processes to be effected with considerably smaller blast cycles than heretofore. In addition, the hazards of accidental detonation which are encountered when sensitive primary explosive compositions, as in blasting caps, are present in continuous reaction trains with the charges are avoided.

An efficient drill-and-blast process requires that as much as possible of the available explosive energy be manifest in the form of high pressure working on the formation surrounding the drill hole, e.g., to break the formation. This is accomplished by having as much of the explosive as possible surrounded by the formation with avoidance of any substantial intervening compressible layer, e.g., an air annulus, between the explosive and the formation. For this reason, the explosive charge is positioned within a drill hole so that it is confined by the formation and contacts the walls of the hole sufficiently to be supported thereby. In each drillload-blast sequence, the hole is drilled, at the selected location, and then the explosive is loaded into the drilled hole, by any of the various ways that are suitable for the type of explosive charge employed, and the length and direction of the hole. For example, if the charge .consists of one or more explosive cartridges or packages, or a solid explosive in bulk, pneumatic loading may be employed. Water gel explosives can be pumped in. The velocity of loading should be low enough that the explosive does not detonate spontaneously by impact with the formation or with a previously loaded cartridge. Such spontaneous detonation during loading is avoided since it can destroy the loading equipment.

The selection of the explosive to be used in the present process is made, as in any blasting process, on the basis of safety, performance, convenience, and economics. To provide the pressures required in hard rock, the explosive should be a condensed, e.g., solid (cast or packed powder), semisolid, or liquid, detonating explosive, and it should be relatively insensitive to heat and mild shock, i.e., it is a secondary explosive rather than a primary explosive. A primary explosive is one which detonates when brought in contact with a flame or incandescent wire, whereas secondary explosives require, at least in practical commercial application, the use of a detonator and frequently a booster for initiation of detonation (Melvin A. Cook, The Science of High Explosives, Reinhold, 1958, pp. 1-4). Representative secondary explosives include dynamites, ammonium nitrate/fuel oil mixtures, TNT, PETN, nitrostarch, and the currently popular waterbearing explosives as exemplified in US Pats. Nos. 3,202,556, 3,355,336, 3,431,155 and 3,444,014. The ingredients of the explosive composition can be premixed and the mixture loaded into the holes, or, where feasible, as in the case of ammonium nitrate prills and fuel oil, the ingredients can be mixed during loading by feeding into a common stream, or loaded separately and mixed in the holes. The explosive charge in a given drill hole can be uniform in composition and/or density throughout its length; or different compositions, or the same composition at different densities, can be employed. If a particular selected composition is insufficiently sensitive to a given energy-projecting system, successful detonation can be achieved by adding a small amount of a sensitizing ingredient, e.g., a finely divided metal fuel, to the composition, or making the charge more sensitive only in the portion thereof where the energy is initially released, e.g., the portion where projectile impact occurs, care being taken, however, to avoid sensitizing the charge to the levels characteristic of the primary explosives (e.g. lead styphnate or lead azide), which are unsafe to handle in bulk under field conditions. Special sensitizing measures may be avoided, however, by altering conditions in the energyprojecting system, such as projectile velocity, area of impact, nose configuration, etc., as will be described hereinafter.

After the drill hole has been loaded, the charge of secondary explosive therein is initiated by means of propagative energy projected to the charge through an inactive medium from a location which confronts, and is separated from, the hole, the energy being released into the charge at a high rate per unit volume of charge in the vicinity of energy release. High rate of release is required to achieve a high local pressure and thereby to initiate detonation. Various types of propagative energy can be so projected and released to produce the required detonation. For example, kinetic energy of motion (e.g., via a projectile), electromagnetic radiation (e.g., via a focussed pulse of light from a laser), or electrical energy (e.g., via a high-energy electrical discharge through an electrode) can be used. The medium through which the energy travels to the charge from the point of projection or emission, e.g., a gun chamber, a laser, or a source of electrical energy such as a capacitor, is inactive (i.e., contains no stored energy), and in most instances will simply be the atmosphere in the vicinity of the mass being worked. In the case of electrical energy, the energy is transmitted at least in part through an electrode. Since the energy is projected locally and a pulse of energy is projected for each of the charges, the initiation step can be performed after loading without the delays required to connect the charges to each other and to a common energy source. This permits efficient blasting in small blast cycles.

Of the various ways of projecting and releasing energy that can be used in the present process, propulsion of a high-velocity projectile and impact thereof with the charge are preferred from the standpoint of ease of operation and availability and cost of equipment. Various kinds of projectiles and ways of propelling the projectile can be employed, provided the impact velocity is sufficiently high and the mass of the projectile sufficiently great to release the energy at a sufficiently high rate, i.e., to subject the charge to high enough pressure over a sufficient area and time that it is caused to detonate completely at its expected velocity under the conditions prevailing in the drill hole. Complete, highorder detonation is required so that the maximum potential of the explosive, e.g., for fragmenting, or introducing seismic energy into, the surrounding formation may be utilized. Thus, as used herein, the term initiation refers to the supplying of an impulse which brings the explosive charge in the drill hole to complete detonation at a rate which falls within a range commonly encountered with the particular explosive composition in question when initiated by conventional means.

In the preferred case of projectile impact initiation, the chief factors determining whether or not such detonation will occur in a given explosive are the velocity of the projectile on impact, the shock impedance of the projectile, and its mass and shape. The minimum projectile velocity is higher as the sensitivity of the explosive to impact and the shock impedance of the projectile are less. For a given explosive and projectile material, the minimum impact velocity required to produce detonation usually is lower as the mass of the projectile is greater (up to a certain maximum) and the area of the projectile nose, i.e., the area of the projectile surface which impacts squarely against the explosive, is larger. Also, for a given system and with a bluntnose projectile, the required detonation may be achieved at lower impact velocities if the trajectory of the projectile is substantially on the drill hole axis (head-on or non-glancing impact). As will be seen from the subsequent examples, certain dynamites are initiated reliably by .22-caliber bullets (3.5 grams; pointed nose) at impact velocities as low as 1500 feet per second, while certain water-gel explosives require higher impact velocities, e.g., about 2800 feet per second, with the same ammunition. On the basis of wider applicability with respect to explosives with which the projectile system is useful, therefore, a system in which bullets are propelled to at least about 3000 feet per second muzzle velocity (about 2800 feet per second impact velocity at a distance of 15 feet from the muzzle) is preferred.

The projectile is a body of material propelled to high velocity. It can be a unitary solid, e.g., a bullet, or solid particles, e.g., shot. A high-velocity fluid jet, such as a water jet, also can be used. Since the required impact velocity and high projectile shock impedance can be attained more readily with solid projectiles, solids are preferred, and particularly unitary solids. Unitary solid projectiles should be made of materials, preferably metals, which are strong enough to withstand the pressure and heat applied during propulsion. Their configuration is generally cylindrical with their forward end pointed or blunt, or spherical. For explosives which are initiated readily by projectile impact, e.g., gelatin dynamites, the pointed-nose bullet found in commercial ammunition rounds can be employed. For less-sensitive explosives, it may be helpful to use a blunt-nose bullet, or one which has a conical cavity in the nose surface. Although the nose of the projectile may carry a secondary explosive charge thereon to assist in the initiation, inert projectiles are preferred since they are safer to store and deliver, and cheaper. When the projectile is propelled, the gun can be in substantial axial alignment with the drill hole, or positioned at a small angle thereto. Substantial axial alignment is preferred to assure accuracy of impact and complete detonation. However, especially if the projectile has a pointed nose, the projectile can come in at an angle, e.g., up to about to the hole axis, the allowable misalignment in any given case depending on the nature of the mass being worked and impact conditions W The type of gun employed to propel the projectile is not critical provided it is capable of affording the required muzzle and impact velocities with the type of projectile and propellant, or ammunition, used. Any small arms, e.g., rifles, shotguns, and pistols, can be used. Air guns also can be employed.

Another suitable way of initiating the explosive charge in the drill hole is to impinge the focussed output of a pulsed laser onto the charge. In such an embodirnent, the ease of initiation of a given explosive charge can be enhanced by increasing the power of the laser, e.g., by use of a Q-switched rather than a freerunning laser, and by having the end of the charge nearest the mouth of the drill hole under suitable confinement. For example, a transparent plastic layer can be employed over the end of the charge, either as a separate unit, or as an end of a cartridge unit, and the focussed laser beam allowed to pass through the plastic to the charge. While the specific amount of energy required to initiate an explosive reliably by a laser beam varies with the particular explosive composition, for the more sensitive secondary explosives such as pentaerythritol tetranitrate, gelatin dynamites, etc. about 0.025 joule/sq mm or more of incident energy is capable of causing initiation when a Q-switched laser beam is focussed on the surface of the charge. Often the charge can be made more sensitive to initiation by incorporating in it a small amount of material having a high light-absorption coefficient, e.g., carbon black. This increases the rate of release of the energy per unit volume.

In still another method of initiating the explosive charge in the drill hole, one or more expendable electrodes are positioned in, or in close proximity to, the charge, e.g., by means of a wire-feeding mechanism, such as those that have been developed for feeding wire offa roll, and energy is projected through and along the electrode by electrically discharging a capacitor bank through the electrode.

A great advantage of the present process is derived from the fact that all of the process steps, including initiation of the charges, are performed locally, with the necessary equipment operating close to the mass being worked on. Thus, the energy to be released into the charges is projected from a location which confronts the mass, although being separated from it. The minimum distance between the energy-projecting device, e.g., a gun, and the drill holes will depend chiefly on the total weight of explosive detonated in one blast cycle (i.e., in holes detonating within milliseconds of each other), the nature of the rock breakage produced (direction and velocity of missiles), and the impact and shock-resistance of the device. As a general rule, the energy-projecting device will be separated from the mass by a distance which is approximately proportional to the cube root of the weight of explosive detonated per cycle. Although large separation distances can be employed, e.g., up to about 1 to 2 tunnel or shaft diameters, it is preferred to work as close to the mass as is feasible with the equipment used. This is especially true when the drill-and-blast module of the invention is employed. In such a case, the module is positioned close enough to the face for the drill to make the desired size hole, e.g., within a few feet, and it is more efficient to perform the blast step, e.g., fire the gun, with the module in about the same position, or at any rate to avoid having to move the module back from the face before blasting.

The length of the explosive charge with respect to the length of the drill hole will vary depending on the type of work being performed. In excavation, it normally will be more efficient to substantially fill the hole with explosive. A layer of gas or liquid, e.g., air or water, or a solid layer, e.g., cardboard or plastic, between the mouth of the drill hole and the end of the charge where the energy is to be released does not preclude satisfactory initiation of the charge under certain circumstances, although the nature and maximum depth of such a layer, beyond which initiation becomes impossible or erratic, varies with the particular type of propagative energy used for initiation, the explosive composition, and the magnitude of the energy. Any material between the mouth of the drill hole and the end of the charge where energy is to be released, as well as between the energy-projection location and the mouth of the drill hole, should be a material which, in the amount present, does not absorb a major fraction of projected energy. For example, a light-absorptive, light-scattering or light defocussing environment should be avoided between a laser device and the charge, and an electrically conductive environment should be avoided around an electrode. With laser initiation, any optically transparent material can be present. In the case of initiation by projectile impact, gases can be present, as well as liquids or solids to a certain depth. For example, explosives such as certain dynamites (Gelex 2), when wrapped in a paper cartridge (cartridge end about three-eighths inch thick, for example) and covered by a layer of water up to about four inches thick in a 1.75-2.00-inch-diameter drill hole, can be initiated reliably by the impact of a commercial fully jacketed .22-caliber bullet (3.5 grams) impacting the water at a velocity of about 2800-3600 feet per second. In practice, any layer of liquid or solid material present over the end of the charge usually will be due to conditions encountered in the area to be blasted, e.g., water, or to the condition of the explosive charged, e.g., a cartridge end.

The location pattern of the sequences (hole pattern), the time pattern in which the drill-load-blast sequences are performed, the number of sequences carried out concurrently (holes per cycle), and the amount of ex plosive detonated per sequence or concurrent group of sequences are all conditions that can vary widely, depending on many factors such as the nature of the work to be performed, the overall size and physical properties of the mass being worked, the number of drill-andblast modules (or separated components) available, the impact and shock-resistance of the equipment (since it confronts the mass during blast), the degree of constriction of the working area, ventilation and noise abatement requirements and capability, etc. For operations such as in seismic prospecting, secondary blasting, etc., one vehicle-mounted module may be moved along the surface as required and employed to perform a succession of single rapid drill-load-blast sequences at desired locations in a desired time pattern. In operations such as trenching or underground excavation, the use of multiple modules to perform multiple sequences concurrently in groups is more efficient, more modules (or more sequences per group or cycle) giving faster advance. The specific number of sequences employed per concurrent group (i.e., holes per cycle) depends on the number of modules, and the space, available, the impact and shock-resistance of the modules, and mounting assembly employed, how close to the face the modules are employed, the size of the charges, and the time interval between blasts. Considering all of these factors, in most cases the size of the cycles will be less than about one-half the size of the entire round, most often up to about 35 percent of the total number of holes required, or such that no more than about 100 pounds, usually up to about 30 pounds, of explosive detonates per cycle.

The angle of the drill holes with respect to the face also will depend on the type of work desired. In some instances, the holes will need to be drilled non-normal to a face because of space restrictions at the sides, roof, and floor of a tunnel. In other instances, oblique holes will be used to provide a special type of cut. Any of the patterns commonly employed in drill-and-blast operations can be employed in the present process.

The present process can be used for excavating in any geological mass, but is particularly advantageous when used in hard abrasive rock, e.g., rock having a compressive strength of more than about 15,000 psi or a Mohs Scale harness greater than about 5, where mechanical excavators are presently ineffective. Moreover, since the application of the process is applicable to a wide range of geological conditions, the process offers the important advantage of being adaptable to use with changing conditions as are commonly encountered, i.e., major differences in rock types and arrangements occuring within relatively small vertical and horizontal distances. Naturally, the process can be employed in excavating for construction purposes, as well as for mineral recovery, e.g., ferrous and nonferrous metal ore mining, stone mining and quarrying, etc., and in seismic prospecting operations.

The drill-and-blast module of the present invention incorporates three basic working components within its structure, i.e., drilling means, means for delivering explosive comprising an explosives-delivery or drill-holeloading tube, and energy-projecting means, e.g., a gun, as well as support means on which the three other components are mounted and which maintain(s) the required positions of the three components relative to one another. Any mounting scheme which is convenient can be employed provided the working end of each component, i.e., the drill bit, discharge end of the delivery tube, and energy-exiting end of the energyprojecting member, e.g., the gun muzzle, are located near a common end, i.e., the operating end of the module, and provided the components are capable of moving as required, i.e., the drill and delivery tube movable axially with respect to the support means, and, in the preferred embodiment, a support means movable, e.g., pivotally and/or slidably, so as to permit the three basic components to be positioned sequentially on a common axis. With these basic components and motions, the module can, in rapid sequence, drill a hole in a geological mass, load explosive into the drill hole, and initiate the explosive, and rapidly repeat the sequence, thereby performing the desired work on the mass. 7 it The general configuration and dimensions of the module will be determined on the basis of economic factors as well as on the range of drill hole depths it will be required to produce and load, the number and types of constructional elements and types of driving mechanisms employed in the module, the positions of the basic components relative to one another, etc. Considering the relative dimensions of drill holes commonly employed in blasting, i.e., diameters of about 05-15 inches and depths of up to about feet, and avoiding telescoping components, which, while feasible, are not preferred since their dependable repeated functioning in a possibly dusty atmosphere may be difficult to achieve, the module usually will be elongate, i.e., long in proportion to its width. The overall configuration of the module, i.e., the shape of the body formed when one or more surfaces are generated about the periphery of its components, is immaterial to its operation, and can be generally cylindrical or prismoidal, with any convenient cross-section, e.g., circular, oval, or polygonal, as is the case when the basic components are substantially parallel to one another; or frustoconical or wedge-shaped, as may occur when the axes of the basic components are convergent. Since, as has been mentioned previously, it is preferred that the proper positioning of the basic components during their operation depend on a sequential coinciding, rather than on a convergence, of their axes, and since convergence is unnecessary when the axes are adapted to coincide sequentially, as well as less efficient with respect to space utilization, substantially parallel positioning of the basic components, and therefore a generally cylindrical module, are preferred. In this preferred embodiment, it will be understood that the cross-sectional area of the cylinder along the cylindrical axis may vary, e.g., decrease from one end to the other, because of the presence of certain constructional elements, or a slight obliqueness, e.g., up to about 10, of the basic component positions with respect to the cylindrical axis.

The support means for the three working components can be a unitary element, e.g., a rod, bar, pipe, or slab, or a skeletal framework of elements, of rigid construction, preferably made of metal, e.g., steel. If an external housing member, such as a cylinder or box, is employed to protect the components against impact, the housing member can serve as a support means with each of the three components mounted in the housing wall. Alternatively, the housing member can serve as a support along with an internal support. For example, when the energy-projecting means is a laser, it may be desirable to mount the laser in the wall of the housing member, and the explosives delivery tube and drilling means on a common internal support means. Any convenient means of mounting the components onto the support can be employed, provided that the drilling means and explosives delivery tube are capable of unobstructed axial motion with respect to the support so that they can both sequentially extend beyond all other components of the module at the operating end, the drill bit being capable of extending beyond the other components for a distance at least equal to the depth of the drill hole required, and the delivery tube for only the short distance, at the minimum, required to insert its discharge end into the drilled hole, although preferably it will be capable of extending farther into the hole.

In order that the module perform in a predetermined manner, i.e., that the achieved conditions such as the location and angle of the drilled hole, explosive loading and density, and trajectory of the projected energy, are in accordance with the preselected conditions, it is necessary that the relative positions of the basic components be maintained during operation of the module, that is, that the components be supported while in extended as well as retracted positions. For this reason, it is preferred that any axially movable basic component which is insufficiently rigid to maintain its required position during operation be held in position by the support for a major portion of the components length, and more preferably for essentially its full length, when in the retracted position, and that the distance between the end of the support at the operating end of the module and the mass to be worked when the component is extended beyond the support end, be insufficient to cause the component to move out of its predetermined axial position. Added assurance of good positioning of the extensible components is achieved by providing guide means on the support near its end through which the components travel as they move axially beyond the support end. Also, the distance between the end of the support and the face can be decreased without having to move the entire module closer to the face by having the support independently axially movable with respect to a module mounting member to which it is affixed. A protruding peg capable of anchoring itself in a rock formation, e.g., by a piercing (a stinger) or suction action, can be provided at the end of the support means, if desired.

The specific distances to which the axially movable components can be extended are not critical to the function of the module and depend on the depth of drill hole(s) required and how close to the face the module is operated. From a given operating position of the module, the explosives delivery tube need not extend as far as the drill bit, and both tube and drilling means will extend farther than the support when the latter moves with respect to a mounting member.

The module is adapted to be mounted on an external supporting arm, preferably via the support means in the module. While the modules support means may be designed to permit it to be joined directly to an external supporting arm, it usually will be more practical to affix a separate mounting member to the module's support, this mounting member later to be joined with a mounting member on the external supporting arm. A convenient construction is one in which the modules mounting member affords the re-positioning capability required of the basic components to cause them to sequentially coincide. For example, the mounting member 'may incorporate a pivot, permitting the supmechanism can be, for example, an hydraulically actuated mechanism, providing either linear motion, as does an hydraulic cylinder, or rotary motion, as does a rotary actuator. Preferably, the indexing mechanism communicates directly with the mounting member for the module, e.g., a groove-containing member through which the support means slides in an axial direction. With respect to pivoting motion, a preferred procedure is to have the drilling means on the desired axis in the rest (vertical) position, with the explosives delivery tube and energy-projecting means mounted on the same side, or opposite sides, of the drilling means and rotate the support in one direction to position the tube on the axis desired, and farther in the same direction, or in the opposite direction, to position the energy-projecting path thereon.

All of the structural components of the module, as well as the motion-imparting mechanism therein, must be shielded against the effects of air blast and possible missile impact resulting from the detonation of the explosive charges in the drill holes. Such shielding may be provided, for example, by a transverse metal plate (i.e., a plate mounted with its large surfaces substantially normal to the module axis) between the module(s) and the mass being worked, wit h the module(s) operating through apertures in the plate. Such shielding for the module(s) affords less maneuverability of the module, however, and is not readily adaptable for use with masses of all sizes. Therefore, it is preferred that the module components be surrounded by a shock and impact-resistant shielding means, i.e., a housing member, permitting the module to be operated in direct confrontation with the mass with no additional shielding necessary between the module and mass. The housing member is made of a sufficiently tough material, e.g., a metal such as certain steels, and is sufficiently thick that it will not rupture or plasticially deform to any great degree as a result of the shock pressures and missile (rock) impacts to which it is exposed. For a given metal, the minimum necessary thickness of the housing will be determined in any given case by the size of the blast (i.e., amount of explosive detonated), size and velocity of rock fragments produced, how close to the blast the module operates, etc. For operation under moderate conditions, e.g., blasts of less than about 4 pounds of explosive, rocks up to about 12 inches in size and moving at velocities up to about 40 feet per second, and distances of at least about 2 feet between the module and face, a housing which has a shell at least about 0.5 inch thick may be employed. Like the configuration of the module, the configuration of the housing member is immaterial, but usually it will be generally cylindrical or prismoidal, as described previously for the module configuration.

Usually, the module will be mounted in the housing member wall by affixing to the housing wall a mounting member which is in engagement with the support means of the module. Affixing the support means directly to the housing wall is not preferred since repositioning of the components would, in such a design, require movement of the housing as well.

The housing member, like the module itself, is elongate, and, since it is required to shield all of the module components, at least during the blast, the operating end of the housing member is adapted to be closed. The non-operating end can be open, but usually will be permanently closed. The operating end is adapted to be opened and closed, for example, as is shown in FIGS. 1 through 5, wherein a shock and impact-resistant swingable closure member, e.g., one or more doors, erected on the housing cylinder at the operating end of the module, is adapted to occupy an open or closed position with respect to the end of the housing cylinder in response to a force imparted by a motion-imparting means, e.g., an hydraulic cylinder, communicating with the closure member from a location within the housing member. The closure member has an aperture or porthole therein which, when the closure member is closed, falls on an axis which is coincident with the axis on which the three working components of the module preferably sequentially coincide. The closure member is moved to the open position when the drilling means, loader, or support means is to be moved axially to an extended position; and to the closed position when all axially extendable members are in the retracted position and the energy is to be emitted from the energyprojecting member. The porthole allows unimpeded travel of the energy from the energy-projecting member to the explosive charge in the drill hole. A conical or wedge-shaped closure configuration is preferred as a means of providing added protection against rock impacts.

The effect of shock and impact on the module can also be moderated by use of energy-absorbing means together with the housing, e.g., by the use of springs in the system for mounting the module on a supporting arm. A particularly useful energy-absorbing device is an inflated pneumatic member, i.e., an elastic member holding fluid under pressure. Such a member, resembling an automobile tire in its function, for example, when engaging the end of the housing cylinder, e.g., as shown in FIGS. 1 through 4, serves to cushion the front of the module from the impact of shock waves and flyrock. Several such members can be employed sideby-side around the housing when additional, and lateral, cushioning is desired.

In the process of this invention, greater efficiency is achieved, e.g., in terms of weight of material excavated per unit time, by performing multiple drill-load-blast sequences concurrently. With the module of this invention, multiple-sequence cycles are achieved by employ ing a number of modules equal to the selected number of sequences to be performed concurrently. Multiple modules each comprising a single drilling means, single explosives delivery means, and single energy-projecting means, suitably supported and housed, can be employed. However, when efficient utilization of space and weight is of prime consideration, it is preferred to employ a composite module which incorporates two or more single-component modules or module units suitably clustered within a common housing member. The geometric arrangement or cluster pattern of the basic module units within the composite module, and the specific number of units, can vary as required. For example, for working concurrently in essentially straight-line or block drill-hole patterns, a linear or block cluster of units can be employed, the overall configuration of the module in such cases being essentially that of a parallelipiped. For working in a curved pattern, the cluster may be in the form of an arc of a circle. In the composite module, each unit can be complete within itself, i.e., have its own drilling means, explosives delivery means, and energy-projecting means; or a common component, e.g., an explosives delivery means, can be shared by more than one unit. 7

Any type of drilling means can be used in the module, e.g., a percussion drill or hammer, a rotary drill, or one employing both percussion and rotary action. An electrical disintegration drill, providing heat and rotation, also can be used. For hard rock, rotary percussion drills are preferred. For convenience, i.e., in order to make use of ready-made components, where available, and in order not to multiply the number of constructional elements unnecessarily, in a preferred module the drilling means and support member constitute a rotary percussion drill and feed, respectively, both constructed of metal, e.g., steel. The drill rotation can be imparted through a pneumatically or hydraulically operated door mounted in the feed channel, and axial thrust for extension and drilling can be applied through a heavy-weight chain feed driven by a pneumatic or hydraulic motor. The explosives delivery tube and energy-projecting means are mounted on support means, e.g., the drill feed channel, in a manner such that axial motion of the drill and the delivery tube is unimpeded.

The explosives delivery tube has an explosives feed end which communicates with an explosives feed system located outside the confines of the module. The explosives feed system is comprised of an explosives supply unit, e.g., a magazine containing cartridged explosive or bulk solid explosive, or a storage and mixing tank for slurry explosive ingredients; and a feed unit associated therewith capable of delivering the explosive therefrom, e.g., a pneumatic loader for solid explosives, or a pump for slurry explosives. The tube from the module can be attached to the loading tube of a pneumatic loader or to the delivery hose of a slurry pump; or, if long enough, it can replace the loading tube or delivery hose entirely and be attached directly to the explosive-delivery mechanism or pump in the explosives feed system. For loading cartridged explosive, e.g., dynamites, a preferred feed unit is a pneumatic cartridge loader such as is described in US. Pat. No. 3,040,615 and in The Modern Technique of Rock Blasting, N. Langefors and B. Kihlstrom, Stockholm, Almqvist & Wiksell, 1967, pp. 91-101. The delivery tube, both the portion thereof which is in the module and that which is outside the module, should be somewhat flexible and can be made, for example, of metal or plastic. With the pneumatic cartridge loader, a semiautomatic breech piece can be used to feed cartridges continuously.

The axial motion of the tube with respect to the support can be accomplished in any one of various ways.

One way is to have a flexible tube, e.g., a plastic tube, lead into a rigid tube, e.g., a metal tube, which is slidably mounted on the support, e.g., in a guiding track, in the desired position with its free end at the operating end of the module and its other end in communication with a pneumatic positioning cylinder. In another method, i.e., that shown in FIG. 3, the tube may be moved by means of a device, i.e., the so-called robot loader," which is also described by N. Langefors and B. Kihlstrom, op cit. The robot loader acts in conjunction with a pneumatic cartridge loader. The robot loader, mounted on the support means, e.g., the drill feed channel, consists of a pneumatic cylinder which reciprocates a tubular piston-rod. The delivery tube is inserted axially through the piston rod. To the piston-rod is connected a pneumatic grip arrangement, a hand which holds the tube by friction so that it undergoes reciprocating motion. As the tubular pistonrod reciprocates, the pneumatic hand" grips on forward movement and releases on backward movement, thus imparting an incremental forward motion to the delivery tube. For retracting the tube after the drill hole has been loaded, the reverse hand action takes place. Preferably, the delivery tube is passed down to the bottom of the drill hole and moved out slowly with repeated light countermovements so as to pack the ejected cartridges to high density.

In a preferred module, the energy-projecting means is a gun. The term gun denotes an assembly which includes a metal tube or barrel having one open end (the muzzle end) and the other end (the after end) adapted to form a chamber into which projectiles are introduced and gas under pressure is admitted or generated rearward of the projectiles upon command. The term is meant to include devices in which projectiles are propelled by gas admitted into the chamber at high pressure, as well as those in which the propellant gas is produced in the chamber by the burning of a propellent composition. When required, as in the latter case, the after end of the barrel is closed off by a breechblock or plug, seated in a housing which can be opened, for loading ammunition into the chamber (forward of the plug), and closed, for igniting the propellent charge, by a breech mechanism upon command. The type of gun employed is not critical provided it is capable of propelling projectile material of sufficient mass at sufficiently high velocity to subject the explosive in the drill hole to high enough pressure over a sufficient area and time that the explosive is caused to detonate. The impact energy required is more readily attained with solid projectiles, and particularly unitary solids, i.e., bullets as contrasted with shot, and for this reason bullets are the preferred projectiles. Also, while the projectile can be propelled by a stream of gas admitted into the chamber at high pressure, as in an air gun, there is less restriction on the attainable impact velocity when the projectile is propelled by the burning of a propellant composition in the chamber. Consequently, guns which operate on the propellant burning principle are preferred. Thus, in the preferred embodiment the gun consists of a metal barrel having its after end closed off by a breechblock or plug which can be opened, for loading an ammunition round into a chamber forward of the plug, and closed, for igniting the propellant charge in the round, by a breech mechanism operating upon command from outside the module. Empty cartridge cases can be continuously ejected from the module, or collected in a container provided for the purpose in the module, the container being adapted to be emptied periodically. The ammunition primer can be a percussion primer, electric primer, or a combination primer. Electric firing of the primer may be preferred in certain cases when greater precision with respect to time intervals between detonations is required.

The magazine for the ammunition can be located inside or outside the confines of the module. An external magazine is preferred because of space restrictions in the module and also because storage of ammunition at a location removed from the operating area is desirable from a safety viewpoint. Therefore with external storage, a loading or delivery tube for ammunition leads from an external ammunition feed system to the chamber of the gun. The feed system can be, for example, a pneumatic loader such as has been described for loading cartridged explosive into a drill hole.

While the gunmay be constructed completely according to custom design, in most cases it will be possible to adapt a commercially available gun, e.g., a boltaction rifle, semi-automatic rifle, or pistol, for use in the module. Rifling of the bore, while desirable, is not strictly required owing to the relatively small distances over which the projectile will travel when the module is in operation. Remote firing of the gun can be accomplished by applying electrical current to a solenoid which actuates a conventional mechanical firing linkage, i.e., trigger action to cause motion of the firing pin to ignite the ignition mixture by percussion; or by applying current to an insulated firing pin in contact with a bridge wire or an electricallyconductive ignition mixture in an electric primer, the electrical circuit being completed through the cartridge case and ground, and the ignition mixture being ignited by ohmic heating of the bridge wire or conductive mix.

When a laser is used as the energy-projecting means, a housing member is required to prevent the entrance of light-absorbing material, such as rock dust, into the path of the laser beam. The laser" includes a laser rod (e.g., ruby), a total reflector at one end, and a partial reflector at the other end of the rod; one or more flash lamps to pump the laser rod; a high-voltage electrical power source to excite the flash lamp(s); a Q-switch or Q-spoiler in the path of the beam between the front end of the rod and the partial reflector; and a focussing lens. To afford maximum protection to the laser during the blast, it is preferred that the laser be in an off-set position with respect to the beam path. For example, the laser can be mounted in the wall of the housing and the beam reflected onto the desired path by suitably positioned reflectors. In such a case, if positioning of the functioning components onto a common axis is employed, the reflectors can be positioned on a support means and moved thereon to project the beam on the required path.

The module also contains, or is in communication with, suitable motionimparting mechanisms, e.g., hydraulic or pneumatic devices, which perform such movements as axially moving the drilling means, explosives delivery tube, and support means (e.g., drill feed channel); drilling; delivering explosives to the drill hole; in a preferred embodiment, delivering ammunition rounds to the gun chamber and firing the gun; repositioning the basic components (i.e., indexing) and opening and closing the housing door at the operating end. Such mechanisms are well-known to those skilled in the art and their basic mode of operation therefore will not be described herein. All power supply lines, e. g., hydraulic lines, for such devices are shielded in the same way as are the module components, preferably by surrounding them in a suitable housing member. When the module includes a housing member, the power supply lines pass into the module through the housing wall via the mounting member, or via one or more special apertures provided therefor.

As stated previously, the module of the invention, when positioned near a surface of material to be worked, e.g., a rock face, and suitably energized, can in rapid sequence drill a hole in the rock, load explosive into the hole, and initiate the explosive by the rapid release of energy therein, e.g., projectile impact. ln-

asmuch as the operation of the module produces an explosion each time the energy enters the explosive, the module must be mechanically mounted on a-supporting arm or base and its functioning controlled from a suitably shielded location. While any mounting and control scheme can be employed, e.g., impact and shock-resistant jack leg or jack bar mounting with power controls separated from the mass being worked by a barricade substantially parallel to the mass, the fullest benefit of the module is derived when it is incorporated into a machine adapted to support, maneuver, and operate one or more of the modules in a substantially continuous manner. For this reason, the module(s) usually will be mounted on a vehicle, such as a truck, and manipulated by personnel from a location inside the vehicle, the vehicle and personnel being suitably protected from the effects of the relatively small blasts.

For a clearer understanding of the process and module of this invention, reference is now made to the drawing, which illustrates the structure and mode of operation of typical modules, and a typical cyclic pattern in which the process can be carried out.

In FIGS. 1 through 4 a module is in position before rock face 1 on a longitudinal axis which is substantially normal to face 1 and parallel to face 2. Each basic working component of the module is shown in three different radial positions, the drilling means being in the vertical plane of view in FIGS. 1 and 2, the explosives delivery tube in FIG. 3, and the energy-projecting means in FIG. 4. When a working component is in this vertical plane, the longitudinal axis of the component substantially coincides with the axis of the drill hole (indicated by a dotted line into the rock in FIG. 1).

Referring to FIGS. 1, 1A, and 2, elongated support means 3, e.g., a drill feed channel, has drilling means mounted thereon, shown as a rotary percussion drill, having an elongated tubular member 4, e.g., a drill steel, and bit 5. The drilling means is movable axially on support means 3, e.g., through a chain feed or screw feed driven by a motor 6, for example an air motor. The motor-driven chain feed or screw feed applies feed pressure or thrust for drilling. Drill action (reciprocation and rotation) is provided by a motor 7, e.g., a pneumatically operated motor. Support means 3 communicates with a mechanism 9, e.g., an hydraulic cylinder, which is adapted to move support means 3 back and forth independently in an axial direction in an axial groove in slide member 37 (3 shown in FIG. 2). Groove-containing slide member 37, attached pivot member 8, having an axis of rotation parallel to the axis of elongated member 4, and flange 12 together constitute the mounting member for the module. An indexing means 31, in this case an hydraulic cylinder (shown in FIG. 1A), communicates with slide member 37 and housing 13, e.g., a metal cylinder. A pointed metal peg or stinger 10 extends axially from the end of support means 3 which faces face 1, and hook-like guide elements 11 extend from support means 3 at the same end, normal to the longitudinal axis, in a manner such that elongated member 4 passes through guide elements 11. Flange 12 attached to pivot member 8 fits through an aperture in the wall of housing 13, flange 12 being adapted to engage a mounting member 14 of a suitable supporting arm for the module. At the operating end of the module, i.e., where drill bit 5 is located, an inflated pneumatic member 15, e.g., a rubber tire, engages the end of housing 13. At this said end, a closure member 16, e.g., a door, is adapted to open or close by actuation of a motor 17, e.g., an hydraulic motor, mounted inside the housing and communicating with closure member 16. The latter has an aperture or porthole 18 therein, so positioned that when the closure member is closed the axis on which the working components sequentially coincide (elongated member 4 axis in FIG. 1) passes through aperture 18.

In FIGS. 3, 19 is an explosives delivery tube, somewhat flexible, e.g., made of plastic, and mounted on support means 3 substantially parallel to elongated member 4, and at the same radial distance as the elongated member from the pivot member 8. One end of tube 19 leads to a conventional explosives feed system, e.g., a pneumatic cartridge loader, as described previously, located outside the confines of the module. The other, free end of the tube is the discharge end and is located at the operating end of the module. Tube 19 passes through the aperture in the wall of housing 13. 20 is a feed mechanism adapted to move tube 19 axially, e.g., a robot loader such as has been described above. Ring-like guide elements 21 extend from support member 3 at the operating end normal to the longitudinal axis, in a manner such that tube 19 passes through the guide elements.

In FIG. 4, 22, 23, and 30 are the barrel, chamber and breech housing, respectively, of a rifle, and 24 is a flexible ammunition delivery tube which leads into the gun chamber 23 and communicates with an ammunition feed system, e.g., a pneumatic loader as previously described, located outside the confines of the module, tube 24 passing through the aperture in the wall of housing 13. The rifle is fixedly mounted on support means 3 substantially parallel to elongated member 4 and at the same radial distance as the elongated member and explosives delivery tube from pivot member 8. The gun muzzle is at the operating end of the module.

Prior to a drill-loadblast sequence, the module is positioned as shown in FIGS. 1 and 1A, elongated member 4 being coaxial with the axis of the drill hole desired, and in a vertical line with pivot member 8.

Motor 17 has been energized to allow closure member 16 to open. In the first step of the sequence (FIGS. 2 and 2A), energizing of mechanism 9 moves support means 3 on slide member 37 axially in the direction of face 1 until stinger firmly engages face 1, helping to stabilize the module when the components are extended. With the support means in this position, the elongated member 4 is moved axially in the direction of face 1 by energizing of motor 6, the drill bit then boring a hole 25 of the desired depth in the rock by the thrust and rotating action imparted to it by the chain or screw feed and motor 7.

After the hole has been drilled, the chain or screw feed acts to retract the drilling means back into the housing 13, and hydraulic cylinder 31 moves slide member 37 so that support means 3 mounted thereon rotates in a counter-clockwise direction by the action of pivot member 8 so as to position explosives delivery tube 19 coaxially with hole 25 and on a vertical line with pivot member 8 (FIGS. 3 and 3A). Tube 19 moves axially and into drill hole 25 by the action of feed mechanism 20. While the delivery tube is in this position, cartridges of condensed high explosive 26 are fed through tube 19 and ejected therefrom into hole 25, e.g., by means of a pneumatic cartridge loader.

After the hole has been loaded with explosive, feed mechanism 20 acts to retract tube 19 back into the housing 13, and hydraulic cylinder 31 again is operated, this time moving slide member 37 and support means 3 mounted thereon, in a clockwise direction so that rifle barrel 22 is coaxial with hole 25 and on a vertical line with pivot member 8 (FIGS. 4 and 4A). Closure member 16 is closed by energizing motor 17, aperture 13, which is larger in diameter than the bullet 27 employed, being coaxial with hole 25. The rifle is fired, e.g., by applying current to the firing pin of the ammunition primer, propelling bullet 27 at high velocity from the rifle muzzle, through aperture 18 and the space between the module and hole 25 and into explosive 26 in the hole 25, along the trajectory indicated by the dotted line. The impact causes the explosive to detonate, and the rock to break and move in a manner as typified in FIG. 4.

FIG. 5 shows a portion of a module similar to that shown in FIGS. l-4, with the exception that in this embodiment a laser is the energy-projecting means, and the design of closure member 16 is modified. The module is shown with components operating in the initiation step of the sequence. In FIG. 5, a laser assembly 32, i.e., rod, lamps, Q-switching device, partial and total reflectors, and focussing lens, is mounted on the wall of housing 13. Laser assembly 32 is connected to a power supply located outside the confines of the module. The laser assembly is located off the drill hole axis. The laser beam 33, after passage through the focusing lens in laser assembly 32, is reflected from parallel reflectors 34 and which direct the beam onto a path coaxial with the drill hole 25. Explosive 26 in the drill hole has a transparent end-cap 36, e.g., a cartridge end, made, for example, of plastic. The module is in a position relative to face 1 such that the focal point of beam 33 is on the surface of explosive 26. Reflectors 34 and 35 are mounted on support member 3 in a manner such that operation of indexing means 31 causes the reflectors to adopt a position such that the path of the beam 33 is coaxial with hole. 25. Closure member 16 is wedge-shaped, and has upper and lower portions which are adapted to open and close. Energizing of the power supply to laser assembly 32 causes emission of a beam 33 of electromagnetic radiation, which travels through the atmosphere to hole 25, passes through transparent end-cap 36, and focusses on the surface of charge 26, causing the charge to detonate.

Typical ways in which the present process and module can be operated to work a geological mass are described in the following examples.

EXAMPLE I As illustrated in FIG. 6, a face 1, substantially flat and vertical, has been opened up in a geological formation such as hard rock, and the face is being advanced, e.g., to drive a tunnel, by the process of this invention. The face is substantially square and is 8 feet high and 8 feet wide. Each round (all of the sequences or holes needed to advance the entire face) consists of 30 holes arranged in parallel columns and rows spaced, for the most part, equidistant from each other. That is, the drill-load-blast sequence of the present process is carried out at 30 locations. The process is being effected in 5 successive groups of sequences, or 5 drill-load-blast cycles per tunnelling round, with 6 sequences, or holes, per cycle. Six modules are employed. In each cycle, six holes are drilled substantially simultaneously and then loaded substantially simultaneously, and then six bullets are propelled, one into each loaded hole, within milliseconds of each other so as to detonate the six charges, the cycle being ended when the continuity of the series of detonations is interrupted for the time interval required to drill a new series of holes (the beginning of the next cycle).

In the situation shown in FIG. 6, the first three cycles (three center rows, designated Cycles 1, 2, and 3) have been concluded, and the fourth cycle 4, is in progress at the blast step of the sequence. The blasting which has been completed has produced rock fragments which have separated from the mass forming horizontal faces 2a and 2b substantially the depth of the drill holes and in planes substantially those of the original holes of Cycles 2 and 3. Rock 28 has accumulated on the floor of the tunnel, exposing a portion 29 of the new vertical face being made.

In the opening cycle, Cycle 1 (center row of six holes), the six holes are fired in a pattern which differs from the firing patterns employed in the remaining cycles. In Cycle 1 the two center holes are fired first, the two holes adjacent to the center holes next, and the two outermost holes last, each pair of holes substantially simultaneously, with about 2-millisecond intervals between pairs. The two center holes lie on convergent axes, each about 10 to the normal (to the face), and the remaining holes diverge to the sides about 15 from the normal. In the remaining cycles, the axis of holes at the facial periphery diverge, while the remainder are substantially normal to the face (oblique holes at the top, bottom, and sides are necessitated by the restricted maneuverability of the modules at the periphery). The six holes in each of these cycles are fired singly in direct linear sequence.

The holes are 1.25 inch in diameter and 1.5 feet long. Each hole is filled, and contains approximately one-half pound of cartridged Gelex 2, a semi-gelatin dynamite. (See Examples 2-6). The drills on the modules are rotary percussion drills, and the loaders are pneumatic cartridge loaders in which the dynamic cartridges are pushed forward through loading tubes and ejected into the drill holes, while the cartridge paper is slit and the explosive is packed to high density. The guns are rifles employing commercial .22-caliber ammunition rounds, and they are fired on an axis with the holes from a distance of 10 feet, providing an impact velocity of 3000 feet per second. Each cycle is completed in about 2.5 minutes, the total dead time within the cycle being about 45 seconds. In FIG. 6, the six holes in Cycle 4 have been drilled and loaded with explosive 26. The bullets 27 are shown just before impact. Impact of the bullets with the charges (at about 2 millisecond intervals) causes detonation and rock breakage with the formation of new face 29 to the level of the holes in Cycle 4.

The procedure described for Cycle 4 is repeated for Cycle 5 after clearing any pieces of rock obstructing the drill hole positions (at the locations marked with to expose the complete new face.

After the round of five cycles has been concluded (five 2.5 minute cycles with about 60-second intervals between cycles) and the rock fragments have been removed from the area, an entirely new face about 1.5 feet behind the original face is exposed.

The following examples serve to illustrate the performance of the process of this invention using a highvelocity bullet as the propagative energy for initiating the explosive, the process being illustrated with different combinations of conditions, i.e., explosive composition, drill hole conditions, and bullet impact velocity, mass, and trajectory. The impact velocities exemplified should not be interpreted as being limit velocities for the systems shown, and in any event the operating limits could be changed as conditions such as have been described were changed, e.g., confinement, contact area, or explosive density. Unless specified otherwise, in each example in the the first step of the sequences a l.75inchdiameter l2-inch-long hole is drilled in a rock mass. The hole then is loaded with condensed high explosive, and the explosive is initiated by firing a bullet'from a rifle, which is aligned coaxially with the hole except where specified otherwise. The

rifle is triggered remotely. The distance between the rifle muzzle and the hole is about 10 feet. The impact velocity given is the velocity of the bullet obtained with the ammunition used and measured 15 feet from the muzzle. Except where noted otherwise, the bullets used are soft-point (unjacketed tip) bullets. Where material other than explosive is present in the drill hole, the bullet passes through the other material, impacting the explosive last. In each example, the drill-load-blast sequence is followed by a second sequence at a different location from the first, and efi ected under the same conditions as the first. In every case, the explosive charge detonates, fracturing the rock.

EXAMPLE 17 The present process is employed to accomplish secondary blasting, i.e., to break up large rocks produced from a previous blasting operation. A single module of the type shown in FIG. is employed, the module being mounted on, and operated from, a vehicle, which moves along the surface among the rocks as required to perform a required succession of drilHoadblast sequences. The drill and loader, and the hole and charge size, are the same as in Example 1, except that in this case the bottom (outside end) of the outermost cartridge consists of a 0.5-inch thick disk of transparent plastic, e.g., polystyrene. The energy-projecting device in the module is a laser head, a model LI-IM6, manufactured by Raytheon Company, the laser head comprising a ruby rod 6% inches long and five-eighths inch in diameter, two FX-47A-6.5 flash lamps, a front mirror which is 65 percent reflective at 6950A, and a 99.9 percent refiective rear mirror. Q-switching is achieved by placing a cell filled with a passive liquid Q-switch solution in the path of the beam between the front end of the rod and the 65 percent mirror. A focussing lens (focal length 45 inches) is positioned forward of the 65 percent mirror. The laser head, Q-switch solution, and lens are mounted to the wall of the housing. Two total reflectors (right-angle'glass prisms) are positioned forward of the lens in a manner such that the axis of the focussed beam is shifted from that of the laser rod to an axis parallel thereto, but separated therefrom by 6 inches. The reflecting prisms are mounted on the drill feed channel. During operation, the module is positioned so that the laser beam is aligned coaxially with the drill hole, and the distance between the charge in the drill hole and the prism nearest to it is 36 inches.

Impact Example velocity Number Secondary explosive Ammunition (bullet wt.) Drill hole condition (lb/sec.)

2 GQIQXY' 2 .22-caliber (3.54 g.) Explosive only 3, 600 10 ..d0 2,800 "BO-caliber (9.57 g.) .2, S00 .22-caliber (3.54 g.) ...d0 1,500 Explosive in paper 0 2, S00

covered by t in. of water.

3, 600 J, 800 2, S00 2, 000 total thickness). Explosive plus lZZ-in. air column l, 000 d 22-caliber (3 5; g.) off drill hole axis)... Explosive only r H 2, 000 .22-caliber (3.54g.) 0 oil drill holeaxis)"... do.... 2,800 Water-gelexplosive .do 3,600 ..do ....do .110. '2, 800 16 do Bil-caliber (9.57 g.) .do. 2, S00

* Semi-gelatin dynamite (63% ammonium nitrate, 20% nitroglycerin). Ammonia dynamite (51% ammonium nitrate, 8% nitroglycerin). 32% Ammonium nitrate, 15% sodium nitrate, of an 86% at]. soln of nionomothylnmiim nitrate, 3% ferrophosphorus, 3% line flake Al powder, and 4'5 H30.

l-in.-tliam., Mir-long hole.

After the hole has been drilled and loaded, the laser is activated by application of a high-current pulse to the laser head from a remote power supply unit (Raytheon Model LPS4, with LPS4A control chassis and LPS4B capacitor banks) having a 2200 microfarad capacitance. The capacitors are charged to 3000 volts giving an energy input of 10,000 joules to the laser cavity. The laser output is focussed onto the charge surface, causing initiation thereof with 0.l000 joule/sq mm incident energy (monitored by means of a Lear Siegler Laser Energy Monitor M1-2). Detonation of the charge causes the rock to fracture.

We claim:

1. Apparatus for rapidly working a geological mass which comprises, in combination,

a. drilling means comprising an elongated member having a bit at one end and positioned on support means in axially movable relationship therewith;

. explosives-delivery means for delivering explosive into a hole made by said drilling means, said explosives-delivery means being positioned on support means in axially movable relationship therewith and in predetermined alignment with respect to said drilling means, said explosives-delivery means comprising a tube having one discharge end and an explosives feed en; and

c. means for projecting energy for initiating explosive delivered into a hole by said explosives-delivery means, said energy-projecting means being positioned on support means in predetermined alignment with said drilling means and said explosivedelivery means, said drilling means, explosivesdelivery means, and energy-projecting means being (1) supported in a manner such that the bit of said drilling means, discharge end of said explosive-delivery means, and energy-exiting end of said energy-projecting means are located near a common, operating end, and (2) positioned, or adapted to be positioned, in a manner such that said energy-projecting means projects energy on a path that leads into an explosive charge delivered by said explosives-delivery means into a hole drilled by said drilling means; and the movable relationship of said drilling means and explosivesdelivery means with the support means being such that the bit of said drilling means and the discharge end of said explosives-delivery means extend sequentially beyond all other components of said apparatus in an axial direction at said operating end.

2. An apparatus of claim 1 wherein the support means is movable by an indexing means that cooperates therewith and is adapted to sequentially position said drilling means and said explosivesdelivery means on substantially a common longitudinal axis.

3. An apparatus of claim 2 wherein the support means is movable by an indexing means that cooperates therewith and is adapted to sequentially position the energy-projecting path of said energy-projecting means on substantially said common longitudinalaxis.

4. An apparatus of claim 3 wherein the support means is pivotally movable.

An apparatus of claim 1 wherein the support means is positioned on a mounting member for the apparatus and in axially movable relationship with said mounting member.

6. An apparatus of claim 5 wherein said mounting member is affixed to the inside wall of a housing member having a closure member affixed to its end at the operating end of said apparatus, said closure member being adapted to open and close and having an aperture therein in the energy-projecting path of said energy-projecting means.

7. An apparatus of claim 1 wherein said energy-projecting means is a gun.

8. Apparatus of claim 1 wherein said energy-projecting means is a pulsed laser.

9. Apparatus of claim 8 wherein a focussing lens is present in the path of the laser beam.

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Classifications
U.S. Classification299/55, 102/313, 299/13
International ClassificationE21D9/00, F42D3/04
Cooperative ClassificationF42D3/04, E21D9/006
European ClassificationF42D3/04, E21D9/00F
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