Patent Publication Number: US-10767479-B2

Title: Method and apparatus for removing pavement structures using plasma blasting

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This provisional application draws from U.S. Pat. No. 8,628,146, filed by Martin Baltazar-Lopez and Steve Best, issued on Jan. 14, 2010, entitled “Method of and apparatus for plasma blasting”. The entire patent incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to the field of pavement structure removal. More specifically, the present invention relates to the field of plasma blasting to remove pavement structures. 
     Description of the Related Art 
     The field of removing pavement structures generally comprises conventional jackhammering. Specifically, whether for mining or civil construction, the pavement structure excavation process generally includes mechanical fracturing and grinding as the primary mechanism for breaking up the pavement. Jackhammering is inefficient, loud, and can cause physical damage to the operator. Mechanical grinding is sometimes used for asphalt, but does not work well for removing concrete surfaces. A better solution to this problem is needed. 
     An alternate method of surface processing for the excavation of hard rock incorporates the use of electrically powered plasma blasting. In this method, a capacitor bank is charged over a relatively long period of time at a low current, and then discharged in a very short pulse at a very high current into a blasting probe comprised of two or more electrodes immersed in an incompressible fluid media. The fluid media is in direct or indirect contact with the pavement to be fractured. 
     Previous plasma blasting probes suffered from difficulties in reusability due to the lack of control of the dynamics of the plasma spark. This lack of control also prevented the aiming of the shock waves from the blast into a desired direction. 
     The present invention, eliminates the issues articulated above as well as other issues with the currently known products. 
     SUMMARY OF THE INVENTION 
     A pavement structure removal method is described that first uses two saws to cut two slits in a pavement structure to separate a working area from the rest of the pavement, and then drilling boreholes in the pavement in between the two slits, filling the boreholes with incompressible fluid (water, for example), inserting plasma blast probes in the boreholes, and blasting the pavement using the plasma blast probes. The fractured pavement is then removed using conventional methods, such as grinding, shoveling, or excavating. 
     A method for fracturing pavement is described herein. The method is made up of the steps of drilling a borehole in the pavement using a drill and removing the drill. The method als includes the steps of inserting a plasma blast probe into the borehole, where the blast probe is designed to focus the blast horizontally and slightly upwards by locating a gap between a plurality of electrodes low in the blast probe, initiating a plasma blast in the plasma blast probe by creating a plasma spark between the electrodes, and removing the plasma blast probe from the borehole. 
     In some embodiments, the method also include the step of vacuuming pavement debris from the borehole before inserting the plasma blast probe. It could also include the step of flushing pavement debris from the borehole with water before inserting the plasma blast probe. The method could also include cutting the pavement with a saw. In some embodiments, there are a plurality of drills and plasma probes drilling and blasting simultaneously. In some cases the drill and plasma probe are mounted on a platform. The method could also include the steps of moving the platform and repeating the method at a new location. Alternatively, the method could include drilling one borehole and inserting the blast probe in a second borehole simultaneously. In some embodiments, the steps also include filling the borehole with blast media. The plasma blast probe could include a housing in the shape of a cylinder. 
     An apparatus for fracturing pavement is described below. The apparatus is made up of a platform mounted on a plurality of wheels, where the wheels are in contact with the pavement, a power source, and a drill electrically connected to the power source and mechanically mounted on the platform such that the drill can drill a borehole to and a bottom surface of the pavement. The apparatus also includes a plasma blast probe, mounted on the platform such that the plasma blast probe can be inserted in a borehole to the bottom surface of the pavement, a power storage device, electrically connected to the power source and mechanically mounted on the platform and connected to the plasma blast probe, and a plurality of electrodes mounted inside of the plasma blast probe and electrically connected to the power storage device. 
     In some embodiments, the drill has a carbide drill bit. The apparatus could also include a saw electrically connected to the power source and mechanically connected to the platform such that the saw can cut the pavement from a top surface to the bottom surface. The saw could have a diamond tipped saw blade. The platform could be attached to a motorized vehicle. The platform could have a plurality of drills and plasma blast probes mounted on it. The apparatus could also include an air compressor electrically connected to the power source and mechanically connected to the platform wherein the air compressor can force compressed air into the borehole. The apparatus could also include a special purpose controller electrically connected to the power source and to the plasma blast probe to control characteristics of the plasma blast. The special purpose controller could be electrically connected to the drill to control a depth of the borehole. The apparatus could also include a pump electrically connected to the power source and mechanically mounted on the platform and controlled by the special purpose controller to pump blast media into the borehole. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
         FIG. 1  shows the prior art plasma blasting system in accordance with some embodiments of the Present Application. 
         FIG. 2A  shows a close up view of the prior art blasting probe in accordance with some embodiments of the Present Application. 
         FIG. 2B  shows an axial view of the prior art blasting probe in accordance with some embodiments of the Present Application. 
         FIG. 3  shows a close up view of the prior art blasting probe comprising two dielectric separators for high energy blasting in accordance with some embodiments of the Present Application. 
         FIG. 4  shows a prior art flow chart illustrating a method of using the plasma blasting system to break or fracture a solid in accordance with some embodiments of the Present Application. 
         FIG. 5  shows a drawing of the improved probe from the top to the blast tip. 
         FIG. 6  shows a detailed view into the improved blast tip. 
         FIG. 7  illustrates an apparatus for removing pavement using drills and plasma blasting bits. 
         FIG. 8  shows the progression of the pavement removal. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a plasma blasting system  100  for fracturing a solid  102  in accordance with some embodiments where electrical energy is deposited at a high rate (e.g. a few microseconds), into a blasting media  104  (e.g. an electrolyte or water), wherein this fast discharge in the blasting media  104  creates plasma confined in a borehole  122  within the solid  102 . A pressure wave created by the discharge plasma emanates from the blast region thereby fracturing the solid  102 . 
     The Plasma Blasting System 
     In some embodiments, the plasma blasting system  100  comprises a power supply  106 , an electrical storage unit  108 , a voltage protection device  110 , a high voltage switch  112 , a transmission line  114 , a cable  116 , a blasting probe  118  and a blasting media  104 . In some embodiments, the plasma blasting system  100  comprises any number of blasting probes and corresponding blasting media. The power supply  106  comprises any electrical power supply capable of supplying a sufficient voltage to the electrical storage unit  108 . The electrical storage unit  108  comprises a capacitor bank or any other suitable electrical storage means. The voltage protection device  110  comprises a crowbar circuit, with voltage-reversal protection means as is well known in the art. The high voltage switch  112  comprises a spark gap, an ignitron, a solid state switch, or any other switch capable of handling high voltages and high currents. In some embodiments, the transmission line  114  and cable  116  comprise a coaxial cable. Alternatively, the transmission line  114  and cable  116  comprises any transmission cable capable of adequately transmitting the pulsed electrical power. 
     In some embodiments, the power supply  106  couples to the voltage protection device  110  and the electrical storage unit  108  via the power line  140  such that the power supply  106  is able to supply power to the electrical storage unit  108  through the power line  140  and the voltage protection device  110  is able to prevent voltage reversal from harming the system. In some embodiments, the power supply  106 , voltage protection device  110  and electric storage unit  108  also couple to the high voltage switch  112  via the transmission line  114  such that the switch  112  is able to receive a specified voltage/current from the electric storage unit  108 . The switch  112  then couples to the cable  116  which couples to the blasting probe  118  each that the switch  112  is able to selectively allow the specified voltage/amperage received from the electric storage unit  108  to be transmitted through the line  116  to the blasting probe  118 . 
     Simple Plasma Blasting Probe 
       FIG. 2A  shows one embodiment for a blasting probe.  FIGS. 5 and 6  show another embodiment. As seen in  FIG. 2A , the blasting probe  118  comprises an adjustment unit  120 , one or more ground electrodes  124 , one or more high voltage electrodes  126  and a dielectric separator  128 , wherein the end of the high voltage electrode  126  and the dielectric separator  128  constitute an adjustable blasting probe tip  130 . The adjustable blasting probe tip  130  is reusable. Specifically, the adjustable blasting probe tip  130  comprises a material and is configured in a geometry such that the force from the blasts will not deform or otherwise harm the tip  130 . Alternatively, any number of dielectric separators comprising any number and amount of different dielectric materials are able to be utilized to separate the ground electrode  124  from the high voltage electrode  126 . In some embodiments, as shown in  FIG. 2B , the high voltage electrode  126  is encircled by the hollow ground electrode  124 . Furthermore, in those embodiments the dielectric separator  128  also encircles the high voltage electrode  126  and is used as a buffer between the hollow ground electrode  124  and the high voltage electrode  126  such that the three  124 ,  126 ,  128  share an axis and there is no empty space between the high voltage and ground electrodes  124 ,  126 . Alternatively, any other configuration of one or more ground electrodes  124 , high voltage electrodes  126  and dielectric separators  128  are able to be used wherein the dielectric separator  128  is positioned between the one or more ground electrodes  124  and the high voltage electrode  126 . For example, the configuration shown in  FIG. 2B  could be switched such that the ground electrode was encircled by the high voltage electrode with the dielectric separator again sandwiched in between, wherein the end of the ground electrode and the dielectric separator would then comprise the adjustable probe tip. 
     The adjustment unit  120  comprises any suitable probe tip adjustment means as are well known in the art. Further, the adjustment unit  120  couples to the adjustable tip  130  such that the adjustment unit  120  is able to selectively adjust/move the adjustable tip  130  axially away from or towards the end of the ground electrode  124 , thereby adjusting the electrode gap  132 . In some embodiments, the adjustment unit  120  adjusts/moves the adjustable tip  130  automatically. The term “electrode gap” is defined as the distance between the high voltage and ground electrode  126 ,  124  through the blasting media  104 . Thus, by moving the adjustable tip  130  axially in or out in relation to the end of the ground electrode  124 , the adjustment unit  120  is able to adjust the power of the blasting probe  118 . As a result, a change in the distance separating the electrodes  124 ,  126  in the blasting probe  118  is able to be used to vary the electrical power deposited into the solid  102  to be broken or fractured. Accordingly, by allowing more refined control over the electrode gap  132  via the adjustable tip  130 , better control over the blasting and breakage yield is able to be obtained. 
     Another embodiment, as shown in  FIG. 3 , is substantially similar to the embodiment shown in  FIG. 2A  except for the differences described herein. As shown in  FIG. 3 , the blasting probe  118  comprises an adjustment unit (not shown), a ground electrode  324 , a high voltage electrode  326 , and two different types of dielectric separators, a first dielectric separator  328 A and a second dielectric separator  328 B. Further, in this embodiment, the adjustable blasting probe tip  330  comprises the end portion of the high voltage electrode  326  and the second dielectric separator  328 B. The adjustment unit (not shown) is coupled to the high voltage electrode  326  and the second dielectric separator  328 B (via the first dielectric separator  328 A), and adjusts/moves the adjustable probe tip  330  axially away from or towards the end of the ground electrode  324 , thereby adjusting the electrode gap  332 . In some embodiments, the second dielectric separator  328 B is a tougher material than the first dielectric separator  328 A such that the second dielectric separator  328 B better resists structural deformation and is therefore able to better support the adjustable probe tip  330 . Similar to the embodiment in  FIG. 2A , the first dielectric  328 A is encircled by the ground electrode  324  and encircles the high voltage electrode  326  such that all three share a common axis. However, unlike  FIG. 2A , towards the end of the high voltage electrode  326 , the first dielectric separator  328 A is supplanted by a wider second dielectric separator  328 B which surrounds the high voltage electrode  326  and forms a conic or parabolic support configuration as illustrated in the  FIG. 3 . The conic or parabolic support configuration is designed to add further support to the adjustable probe tip  330 . Alternatively, any other support configuration could be used to support the adjustable probe tip. Alternatively, the adjustable probe tip  330  is configured to be resistant to deformation. In some embodiments, the second dielectric separator comprises a polycarbonate tip. Alternatively, any other dielectric material is able to be used. In some embodiments, only one dielectric separator is able to be used wherein the single dielectric separator both surrounds the high voltage electrode throughout the blast probe and forms the conic or parabolic support configuration around the adjustable probe tip. In particular, the embodiment shown in  FIG. 3  is well suited for higher power blasting, wherein the adjustable blast tip tends to bend and ultimately break. Thus, due to the configuration shown in  FIG. 3 , the adjustable probe tip  330  is able to be reinforced with the second dielectric material  328 B in that the second dielectric material  328 B is positioned in a conic or parabolic geometry around the adjustable tip such that the adjustable probe tip  330  is protected from bending due to the blast. 
     In one embodiment, water is used as the blasting media  104 . The water could be poured down the borehole  122  before or after the probe  118  is inserted in the borehole  122 . In some embodiments, such as horizontal boreholes  122  or bore holes  122  that extend upward, the blasting media  104  could be contained in a balloon or could be forced under pressure into the borehole  122  with the probe  118 . 
     As shown in  FIGS. 1 and 2 , the blasting media  104  is positioned within the borehole  122  of the solid  102 , with the adjustable tip  130  and at least a portion of the ground electrode  124  suspended within the blasting media  104  within the solid  102 . Correspondingly, the blasting media  104  is also in contact with the inner wall of the borehole  122  of the solid  102 . The amount of blasting media  104  to be used is dependent on the size of the solid and the size of the blast desired and its calculation is well known in the art. 
     The method and operation  400  of the plasma blasting system  100  will now be discussed in conjunction with a flow chart illustrated in  FIG. 4 . In operation, as shown in  FIGS. 1 and 2 , the adjustable tip  130  is axially extended or retracted by the adjustment unit  120  thereby adjusting the electrode gap  132  based on the size of the solid  102  to be broken and/or the blast energy desired at the step  402 . The blast probe  118  is then inserted into the borehole  122  of the solid such that at least a portion of the ground and high voltage electrodes  124 ,  126  of the plasma blasting probe  118  are submerged or put in contact with the blasting media  104  which is in direct contact with the solid  102  to be fractured or broken at the step  404 . Alternatively, the electrode gap  132  is able to be adjusted after insertion of the blasting probe  118  into the borehole  122 . The electrical storage unit  108  is then charged by the power supply  106  at a relatively low rate of speed (e.g., a few seconds) at the step  406 . The switch  112  is then activated causing the energy stored in the electrical storage unit  108  to discharge at a very high rate of speed (e.g. tens of microseconds) forming a pulse of electrical energy (e.g. tens of thousands of Amperes) that is transmitted via the transmission line  114  and cable  116  to the plasma blasting probe  118  to the ground and high voltage electrodes  124 ,  126  causing a plasma stream to form across the electrode gap  132  through the blast media  104  between the high voltage electrode  126  and the ground electrode  124  at the step  408 . 
     During the first microseconds of the electrical breakdown, the blasting media  104  is subjected to a sudden increase in temperature (e.g. about 5000 to 10,000° C. or more) due to a plasma channel formed between the electrodes  124 ,  126 , which is confined in the borehole  122  and not able to dissipate. The heat generated vaporizes or reacts with part of the blasting media  104 , depending on if the blasting media  104  comprises a liquid or a solid respectively, creating a steep pressure rise confined in the borehole  122 . Because the discharge is very brief, a blast wave comprising a layer of compressed water vapor (or other vaporized blasting media  104 ) is formed in front of the vapor containing most of the energy from the discharge. It is this blast wave that then applies force to the inner walls of the borehole  122  and ultimately breaks or fractures the solid  102 . Specifically, when the pressure expressed by the wave front (which is able to reach up to 2.5 GPa or more), exceeds the tensile strength of the solid  102 , fracture is expected. Thus, the blasting ability depends on the tensile strength of the solid  102  where the plasma blasting probe  118  is placed, and on the intensity of the pressure formed. The plasma blasting system  100  described herein is able to provide pressures well above the tensile strengths of common rocks (e.g. granite=10-20 MPa, tuff=1-4 MPa, and concrete=7 MPa). Thus, the major cause of the fracturing or breaking of the solid  102  is the impact of this compressed water shock wave front which is comparable to one resulting from a high-energy chemical explosive (e.g., dynamite). 
     As the reaction continues, the blast wave begins propagating outward toward regions with lower atmospheric pressure. As the wave propagates, the pressure of the blast wave front falls with increasing distance. This finally leads to cooling of the gasses and a reversal of flow as a low-pressure region is created behind the wave front, resulting in equilibrium. 
     If the blasting media  104  comprises a thixotropic fluid as discussed above, when the pulsed discharge vaporizes part of the fluid, the other part rheologically reacts by instantaneously increasing in viscosity, due to being subjected to the force of the vaporized wave front, such that outer part of the fluid acts solid like. This now high viscosity thixotropic fluid thereby seals the borehole  122  where the blasting probe  118  is inserted. Simultaneously, when the plasma blasting system  100  is discharged, and cracks or fractures begin to form in the solid  102 , this newly high viscosity thixotropic fluid temporarily seals them thereby allowing for a longer time of confinement of the plasma. Thus, the vapors are prevented from escaping before building up a blast wave with sufficient pressure. This increase in pressure makes the blasting process  400  described herein more efficient, resulting in a more dramatic breakage effect on the solid  102  using the same or less energy compared to traditional plasma blasting techniques when water or other non-thixotropic media are used. 
     Similarly, if the blasting media  104  comprises an ER fluid as discussed above, when the pulsed discharge vaporizes part of the fluid, a strong electrical field is formed instantaneously increasing the non-vaporized fluid in viscosity such that it acts solid like. Similar to above, this now high viscosity ER fluid thereby seals the borehole  122  where the blasting probe  118  is inserted. Simultaneously, when the plasma blasting system  100  is discharged, and cracks or fractures begin to form in the solid  102 , this newly high viscosity ER fluid temporarily seals them thereby allowing for a longer time of confinement of the plasma. Thus, again the vapors are prevented from escaping before building up a blast wave with sufficient pressure. 
     During testing, the blast probe of the blasting system described herein was inserted into solids comprising either concrete or granite with cast or drilled boreholes having a one inch diameter. A capacitor bank system was used for the electrical storage unit and was charged at a low current and then discharged at a high current via the high voltage switch  112 . Peak power achieved was measured in gigawatts. Pulse rise times were around 10-20 μsec and pulse lengths were on the order of 50-100 μsec. The system was able to produce pressures of up to 2.5 GPa and break concrete and granite blocks with masses of more than 850 kg with one discharge. 
     Advanced Plasma Blasting Probe 
       FIG. 5  shows an alternative probe  500  embodiment. Probe coupler  501  electrically connects to cable  116  for receiving power from the capacitors  108  and mechanically connects to tethers (could be the cable  116  seen in  FIGS. 1 and 7  or other mechanical devices to prevent the probe  500  from departing the borehole  122  after the blast. The probe coupler  501  may incorporate a high voltage coaxial BNC-type high voltage/high current connector to compensate lateral Lorentz′ forces on the central electrode and to allow for easy connection of the probe  500  to the wires  114 . The mechanical connection may include an eye hook to allow carabiners or wire rope clip to connect to the probe  500 . Other mechanical connections could also be used. The probe connection  501  could be made of plastic or metal. The probe connector  501  could be circular in shape and 2 inches in diameter for applications where the probe is inserted in a borehole  122  that is the same depth as the probe  500 . In other embodiments, the probe  500  may be inserted in a deep hole, in which case the probe connector  501  must be smaller than the borehole  122 . 
     The probe connector  501  is mechanically connected to the shaft connector  502  with screws, welds, or other mechanical connections. The shaft connector  502  is connected to the probe shaft  503 . The connection to the probe shaft  503  could be through male threads on the top of the probe shaft  503  and female threads on the shaft connector  502 . Alternately, the shaft connector  502  could include a set screw on through the side to keep the shaft  503  connected to the shaft connector  502 . The shaft connector  502  could be a donut shape and made of stainless steel, copper, aluminum, or another conductive material. Electrically, the shaft connector  502  is connected to the ground side of the cable  116 . An insulated wire from the probe connector  501  to the high voltage electrode  602  passes through the center of the shaft connector  502 . For a 2 inch borehole  122 , the shaft connector could be about 1.75 inches in diameter. 
     The shaft  503  is a hollow shaft that may be threaded  507  at one (or both) ends. The shaft  503  made of stainless steel, copper, aluminum, or another conductive material. Electrically, the shaft  503  is connected to the ground side of the cable  116  through the shaft connector  502 . An insulated wire from the probe connector  501  to the high voltage electrode  602  passes through the center of the shaft  503 . Mechanically, the shaft  503  is connected to the shaft connector  502  as described above. At the other end, the shaft  503  is connected to the cage  506  through the threaded bolt  508  into the shafts threads  507 , or through another mechanical connection (welding, set screws, etc). The shaft  503  may be circular and 1.5 inches in diameter in a 2 inch borehole  122  application. The shaft may be 40 inches long, in one embodiment. At several intervals in the shaft, blast force inhibitors  504   a ,  504   b ,  504   c  may be placed to inhibit the escape of blast wave and the blasting media  104  during the blast. The blast force inhibitors  504   a ,  504   b ,  504   c  may be made of the same material as the shaft  503  and may be welded to the shaft, machined into the shaft, slip fitted onto the shaft or connected with set screws. The inhibitors  504   a ,  504   b ,  504   c  could be shaped as a donut. 
     The shaft  503  connects to the cage  506  through a threaded bolt  508  that threads into the shaft&#39;s threads  507 . This allows adjustment of the positioning of the cage  506  and the blast. Other methods of connecting the cage  503  to the shaft  506  could be used without deviating from the invention (for example, a set screw or welding). The cage  506  may be circular and may be 1.75 inches in diameter. The cage  506  may be 4-6 inches long, and may include 4-8 holes  604  in the side to allow the blast to impact the side of the blast hole  122 . These holes  604  may be 2-4 inches high and may be 0.5-1 inch wide, with 0.2-0.4 inch pillars in the cage  506  attaching the bottom of the cage  506  to the top. The cage  506  could be made of high strength steel, carbon steel, copper, titanium, tungsten, aluminum, cast iron, or similar materials of sufficient strength to withstand the blast. Electrically, the cage  506  is part of the ground circuit from the shaft  503  to the ground electrode  601 . 
     In an alternative embodiment, a single blast cage could be made of weaker materials, such as plastic, with a wire connected from the shaft to the ground electrode  601  at the bottom of the cage  506 . 
     The details of the cage  506  can be viewed in  FIG. 6 . A ground electrode  601  is located at the bottom of the cage  506 . The ground electrode  601  is made of a conductive material such as steel, aluminum, copper or similar. The ground electrode  601  could be a bolt screwed in female threads at the bottom of the cage  506 . Or a nut could be inserted into the bottom of the cage for threading the bolt  601  and securing it to the cage  506 . The bolt  601  can be adjusted with washers or nuts on both sides of the cage  506  to allow regulate the gap between the ground electrode bolt  601  and the high voltage electrode  602 , depending upon the type of solid  102 . 
     The wire that runs down the shaft  503 , as connected to the cable  116  at the probe connector  501 , is electrically connected to the high voltage electrode  602 . A dielectric separator  603  keeps the electricity from coming in contact with the cage  506 . Instead, when the power is applied, a spark is formed between the high voltage electrode  602  and the ground electrode  601 . In order to prevent the spark from forming between the high voltage electrode  602  and the cage  506 , the distance between the high voltage electrode  602  and the ground electrode  601  must be less than the distance from the high voltage electrode  602  and the cage  506  walls. The two electrodes  601 ,  602  are on the same axis with the tips opposing each other. If the cage is 1.75 inches in diameter, the cage  506  walls will be about 0.8 inches from the high voltage electrode  602 , so the distance between the high voltage electrode  602  and the ground electrode  601  should be less than 0.7 inches. In another embodiment, an insulator could be added inside the cage to prevent sparks between the electrode  602  and the cage when the distance between the high voltage electrode  602  and the ground electrode  601  is larger. 
     This cage  506  design creates a mostly cylindrical shock wave with the force applied to the sides of the borehole  122 . In another embodiment, additional metal or plastic cone-shaped elements may be inserted around lower  601  and upper electrodes  602  to direct a shock wave outside the probe and to reduce axial forces inside the cage. 
     In one embodiment, a balloon filled with water could be inserted in the cage  506  or the cage  506  could be enclosed in a water filled balloon to keep the water around the electrodes  601 ,  602  in a horizontal or upside down application. 
     The method of and apparatus for plasma blasting described herein has numerous advantages. Specifically, by adjusting the blasting probe&#39;s tip and thereby the electrode gap, the plasma blasting system is able to provide better control over the power deposited into the specimen to be broken. Consequently, the power used is able to be adjusted according to the size and tensile strength of the solid to be broken instead of using the same amount of power regardless of the solid to be broken. Furthermore, the system efficiency is also increased by using a thixotropic or reactive materials (RM) blasting media in the plasma blasting system. Specifically, the thixotropic or RM properties of the blasting media maximize the amount of force applied to the solid relative to the energy input into the system by not allowing the energy to easily escape the borehole as described above and to add energy from the RM reaction. Moreover, because the thixotropic or RM blasting media is inert, it is safer than the use of combustible chemicals and/or explosives. As a result, the plasma blasting system is more efficient in terms of energy, safer in terms of its inert qualities, and requires smaller components thereby dramatically decreasing the cost of operation. 
     Accordingly, for the mining and civil construction industries this will represent more volume of rock breakage per blast at lower cost with better control. For the public works construction around populated areas this represents less vibration, reduced noise and little to no flying rock produced. For the space exploration industry where chemical explosives are a big concern, the use of this inert blasting media is an excellent alternative. Overall, the method of and apparatus for plasma blasting described herein provides an effective reduction in cost per blast and a higher volume breakage yield of a solid substance while being safe, environmentally friendly and providing better control. 
     Pavement Removal 
     The above plasma blasting probes can be very useful in the removal of pavement, especially rigid pavement such as Portland cement concrete. Because the concrete is rigid and hard, it is difficult to break using traditional methods such as jackhammers or grinding machines. Grinding machines are often used for flexible pavement such as hot mix asphalt, but the grinding machines are less effective with rigid pavement. Jackhammers are often used to break up the rigid concrete, but this is labor intensive, and can be harmful to the workers. Another method for the removal of pavement is to cut the concrete into large blocks that are lifted intact into trucks for removal. But block removal does not work if the concrete has deteriorated. Furthermore, block removal leaves huge blocks of concrete that need to be broken up at a later time. 
       FIG. 7  illustrates a pavement removal apparatus  700 . The apparatus  700  is built on a platform  701  that could be connected to a truck or a tractor via a hitch  706   a ,  706   b . The hitch  706   a ,  706   b  could be connected to the front or back of the apparatus  700 . Using the front hitch  706   a  has the advantage of allowing the truck or tractor to drive on the existing pavement, allowing for faster and smoother operation. Using the rear hitch  706   b  allows the apparatus  700  to be operated close to barriers, such as walls and confined areas. The hitch  706   a ,  706   b  could be a three-point hitch, a trailer hitch, a plow hitch, or a tractor bucket attachment (or similar) to the truck or tractor. In the preferred embodiment, the truck or tractor is able to lift the apparatus  700 . Ideally, the hitch  706   a ,  706   b  has the capability to maneuver the apparatus  700  with precision, keeping the apparatus  700  level even when the pavement is uneven. 
     The platform  701  could be the width of a lane of road for applications where the pavement is on a roadway. However, other sizes could be used without departing from the invention. 
     In one embodiment, the platform  701  is mounted on two wheels  703   a ,  703   b . This allows the hitch  706   a ,  706   b  to maintain level over various surface conditions. It also allows the hitch  706   a ,  706   b  to vary the level of the saws  702   a ,  702   b . In another embodiment, the apparatus  700  is mounted on four (or more) wheels. This embodiment could include a leveling apparatuses on the platform  701  to assure that the platform  701  is level. This embodiment might include accelerometers at the corners of the platform  701  and a controller to direct the leveling apparatuses. 
     The platform  701  may have saws  702   a ,  702   b  on either side for cutting the pavement at the edge of the area to cut. In another embodiment, the saws  702   a ,  702   b  could be mounted of such that the saws  702   a ,  702   b  could be moved to any distance apart, perhaps by mounting the saws  702   a ,  702   b  on the front of the platform  701  on a rail. Saws  702   a ,  702   b  could be diamond saws, carbide saws, of any other type of saw suitable for cutting pavement. In many embodiments, water is used to cool the saws  702   a ,  702   b  and to minimize the dust from the cutting. The saws  702   a ,  702   b  are powered by the power source  106  through the wire harness  708 . 
     The platform  701  also has a variable number of drills  704   a - i  mounted on the platform. These drills receive their power from the power source  106  through a wiring harness  708 . In some embodiments, each drill can be turned on or off separately so that any width of pavement can be removed. For instance, in the moveable saw embodiment above, the saws  702   a ,  702   b  could be moved in and four drills  704   a - i  activated to use the apparatus  700  to remove a smaller section of pavement. The drills  704   a - i  could be located 1 foot apart in some embodiments and could drill 1 inch holes. The holes could be drilled about 60% of the way into the pavement. The drills  704   a - i  could be diamond tipped drills, carbide tipped, or other material suitable for drilling pavement. The drills  704   a - i  could create a core for removal or could break up the material as it drills. In many embodiments, water is used to cool the drills  704   a - i  and to minimize the dust from the drilling. 
     In addition to powering the drills and the saws, the power source  106  supplies power to the power storage device  108  through the wire harness  708 . 
     There are also a various number of plasma blast probes  705   a - i  mounted on the platform, one each behind and in line with the drills  704   a - i . After the drills  704   a - i  create the boreholes in the pavement, the platform is moved forward and the plasma blast probes  705   a - i  are inserted in the boreholes. The energy stored in the power storage device  108  is then discharged through the cable  116  into the probes to create a plasma blast in the borehole, breaking up the pavement. The plasma blast probes  705   a - i  are described above, although the design may be modified to maximize the blast waves in a symmetrical, horizontal direction. The distance between the drills and the plasma blast probes could be 1 foot in some embodiments. 
     In many applications, the energy from the blast needs to be focused on the horizontal directions, and the forces going down minimized. This could be done by designing the probe  500 ,  705   a - i  to create the plasma blast low in the cage  506  by making the gap in between the electrodes  601 , 602  low in the cage  506 . The cage  506  then protects the surface below the probes  500 ,  705   a - i  and focuses the energy horizontally and slightly upward. Alternately, a metal cone could be placed at the bottom of the borehole to reflect the shock waves going downward back up. 
     The apparatus  700  could vary the depths of the boreholes, the width of the boreholes, the distance between the boreholes, the distance between the drills  704   a - i  and the probes  705   a - i , the energy used in the blasts, and the distance between the electrodes  601 , 602  to manage the precision of the pavement removal and to account for various strengths and characteristics of the pavement. Typically, the pavement is about 12 inches thick, and care must be taken not to damage the compacted gravel underside of the concrete roadway. Other applications could consist of airport runways or bridge decking. 
     In one embodiment, the drills  704   a - i  and the probes  705   a - i  could be mounted on such that when the drills  704   a - i  finish drilling, they are removed from the boreholes and the probes  705   a - i  are inserted and blast before the platform  701  moves. 
     In another embodiment, the drills  704   a - i  and probes  705   a - i  are mounted such that the boreholes are drilled horizontally into the side pavement. The cage  506  on the probes  705   a - i  could be designed to focus the blast up and to the sides, protecting the under-pavement and loosening the pavement above the horizontal borehole. 
     In still another embodiment, the drill bits could be designed to also incorporate a plasma blast probe, so that the drilling and blasting are performed without removing the drill bit/blast probe. In this embodiment, the drill bit is on the bottom of the probe, and cuts the pavement until the blast probe is at the proper depth. Then the probe initiates the plasma blast. To prevent the drilling debris from blocking the electrodes, a plastic sleeve may need to surround the blast chamber. Alternatively, a suction mechanism could be used to remove the drilling debris. 
     In one embodiment, the functionality of the drills  704   a - i  could be combined with the plasma blast probe  705   a - i . In this embodiment, the probe shown in  FIG. 6  would be modified to mount a drill and bit below the lower electrode  601 . The drill would drill the hole, breaking up the material as if proceeds. The material could be removed via vacuum or via circulating water or compressed air. When the borehole is drilled such that the plasma blast cage  506  is at the proper depth, the drill stops and a plasma blast is initiated to break the pavement. An additional step to clean the probe by flushing the electrodes may be needed. In this embodiment, there is no need for a second row of plasma blast probes  705   a - i  although the line of drill/probe devices should be moved behind the saws  702   a ,  702   b  so that the blast does not create cracking beyond the intended area for removal. 
     A special purpose controller  707  is also located on the platform  701 . The special purpose controller  707  is shielded to protect the controller from electrical, magnetic, and mechanical interference from the plasma blasts. The controller  707  could include a special purpose microprocessor, memory, a mass storage device (hard disk, CD or solid state drive), IO interfaces to the probes  705   a - i  and the drills  704   a - i , power conditioning equipment, a Bluetooth interface, a network interfaces (could be WiFi, Cellular, wired Ethernet, or similar). 
     The controller  707  could operate algorithms to control the separation of the electrodes in the probe  705   a - i  and the amount of energy (varying voltages and/or the number of capacitors) sent to the probe to create the spark/plasma blast. In addition, the controller  707  could control length of time that the spark is present and the timing of one or more plasma blasts if multiple blasts are desired. By controlling these factors the characteristics of the plasma blast can be controlled with precision. In addition, the controller  707  could determine how deep the drills make the boreholes and the depth where plasma blast probe is located when the blast is initiated. 
       FIG. 8  shows the progression of the apparatus  700  across pavement  800 . The pavement is cut with two slits  801   a ,  802   b  created by the saws  702   a ,  702   b . As the saws  702   a ,  702   b  cut through the pavement on the edges, the drills  704   a - i  create the boreholes  802   a - i . Once the boreholes  802   a - i  are drilled, the apparatus  700  move forward one foot (or the distance between the drills  704   a - i  and the probes  705   a - i ) while the saws  702   a ,  702   b  continue to lengthen the slits  801   a ,  801   b . The probes  705   a - i  are then inserted in the boreholes  803   a - i  and the plasma blasts are initiated, creating broken pavement  804   a - i . Meanwhile, the drills  7041 - i  beginning drilling a new set of boreholes  802   a - i . Once the pavement is broken  804   a - i , any number of techniques can be used to remove the cracked and broken pavement. For instance, a skid steer could be used to collect the broken pavement in its bucket or men could be used to shovel the pavement out of the road. Automated bucket devices could scoop up the broken pavement and put it on a transfer line for delivery to a dump truck. 
     The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of principles of construction and operation of the invention. Such reference herein to specific embodiments and details thereof is not intended to limit the scope of the claims appended hereto. It will be readily apparent to one skilled in the art that other various modifications may be made in the embodiment chosen for illustration without departing from the spirit and scope of the invention as defined by the claims. 
     The foregoing devices and operations, including their implementation, will be familiar to, and understood by, those having ordinary skill in the art. 
     The above description of the embodiments, alternative embodiments, and specific examples, are given by way of illustration and should not be viewed as limiting. Further, many changes and modifications within the scope of the present embodiments may be made without departing from the spirit thereof, and the present invention includes such changes and modifications.