Method and apparatus for installment of underground utilities

Abstract: A method and apparatus for installing underground utilities using an offset head fluid jet drilling and reaming apparatus (38). The drill is maneuverable and provides means for remote sensing of orientation and depth. Embodi­ ments are illustrated with single and multiple jet cutting orifices.

Description: This invention pertains to the drilling of soft materials, more particularly to drilling materials such as earth with the use of high pressure fluid, with still greater particularity to the drilling of soil for the purpose of installing utilities. Due to the aesthetic and safety considerations, utilities such as electricity, telephone, water and gas are often supplied from underground lines. The most common means of installing such lines is the cut and cover technique, where a ditch is first dug in the area where the line is desired. The utility line is then installed in the ditch and the ditch covered. This technique is most satisfactory for new construction. In built up areas, the cut and cover technique has a number of problems. First, a ditch often cannot be dug without disturbing existing structures and traffic areas. Digging the trench also creates a greatly increased chance of disturbing existing utility lines. Finally, the trench after refilling, often remains as a partial obstruction to traffic. For the above reasons, a number of means of boring through unconsolidated material such as soil have been proposed. To date none of the boring methods have met with widespread commercial adoption. U.S. 4 401 170 discloses a method of drilling and reaming an arcuate underground passageway beneath an obstacle in which a directional drill attached to a drill string having periodic concentric collars is advanced in an inverted arcuate path to form a pilot hole underneath the obstacle followed by a larger concentric washover pipe. When the washover pipe reaches the surface on the other side of the obstacle a first reamer is attached to the end of the washover pipe exiting the drilling path, second reamer of smaller diameter than the first reamer is attached to the other end of the first reamer by means providing for some separation between the two reamers, and a production casing of smaller diameter than the second reamer is attached to the other end of the second reamer with a swivel. The remaining length of the first portion of casing is supported some distance above the ground on rollers located above and beyond the exit point of the pilot hole. The reamers are operated by rotating the washover pipe and simultaneously drawing the washover pipe through the pipe hole. GB 2,126,267A discloses apparatus for drilling a steered underground passageway comprising a bendable tubular drill string, a nozzle mounted on the front end of the drill string, linear drive means for advancing the drill string, rotary drive means for rotating the nozzle and fluid supply means for supplying pressurised drilling fluid to said nozzle, said nozzle being arranged in use to generate a fluid cutting jet which cuts a path offset from the axis of rotation of the nozzle whereby the nozzle and drill string can proceed in a straight direction if advanced with rotation of the nozzle and can deviate in direction of offset if advanced without rotation of the nozzle. According to the present invention there is provided an underground utility installation apparatus for drilling a steered underground passageway in soil or other soft material comprising a bendable tubuiar drill string a nozzle mounted on the front end of the drill string, linear drive means for advancing the drill string, rotary drive means for rotating the nozzle, fluid supply means for supplying pressurised drilling fluid to said nozzle, said nozzle being arranged to in use to generate a fluid cutting jet which cuts a path offset from the axis of rotation of the nozzle with the velocity component of the jet along the axis of rotation being greater than the velocity component of the jet transverse to the axis of rotation whereby the nozzle and drill string can proceed in a straight direction using the cutting jet advanced with rotation of the nozzle and can deviate in the direction of offset if advanced without rotation of the nozzle and a smooth tapered guide surface being provided on the head of the nozzle inclined to the axis of rotation of the nozzle on the side opposite the direction of offset said head being asymmetrical about the axis of rotation of the nozzle whereby said cutting jet and guide surface combine to cause said nozzle and drill string to proceed in a curve through soil or other soft material if advanced without rotation said fluid supply means supplying cutting fluid to generate the fluid cutting jet both when advancing said nozzle in a straight direction during rotation and when advancing said nozzle in said direction of offset without rotation. Electronic guide means may be provided for monitoring the progress of the nozzle through the soil or other soft material. Preferably said guide surface is substantially parallel with the flow axis of said cutting jet. In use, the tool is advanced is a straight path rotating the nozzle and pushing. To advance around a curve, rotation is stopped and the drill orientated so that the head of the nozzle is pointed in the proper direction. The tool is then pushed without rotation until the proper amount of curvature is obtained. During this push, a slight oscillation of the drill can be used to work the head around the rocks and increase cutting. Continued straight advancerient is obtained using rotation. Figure 1 is a perspective view of the advancing frame of the invention; Figure 2 is a partial section elevation view of a section of a drill pipe; Figure 3 is a section view of a nozzle usable with the invention; Figure 4 is a second embodiment of a nozzle usable with the invention; Figure 5 is a partial section elevation view of a reamer for use with apparatus in accordance with the invention; Figure 6 is a partial section elevation view of a nozzle for a third embodiment of the invention; Figure 7 is a schematic view of the transmitter of an embodiment of the invention; Figure 8 is an isometric view of a pitch sensor of an embodiment of the invention. Figure 1 is a perspective view of the advancing frame end of the system. An advancing frame 1 contains the stationary elements of the system. Frame 1 is inclinable to any convenient angle for insertion of the drill. A motor 2 is mounted to frame 1 with a provision for lateral movement. In this embodiment, motor 2 is advanceable by means of a chain 3 which is connected to an advancement motor 4. Activation of motor 4 advances motor 2. A high pressure swivel 6 is connected to the shaft of motor 2. A pipe 7 is also connected to swivel 6 by means of a coupling 8. Swivel 6 allows the supply of high pressure fluid to pipe 7 while motor 2 is rotating pipe 7. Activation of motor 2 causes pipe 7 to rotate. In this embodiment swivel 6 is supplied with fluid at a pressure of from 100 to 280 bar (1500 to 4000 pounds per square inch). The fluid may be water or a water/bentonite slurry or other suitable cutting fluid. The supply is from a conventional high pressure pump (not shown). Figure 2 is a partial section elevation view of a section of a drill pipe 11. In this embodiment pipe ends 12, 13 are attached by respective welds 15, 16 to respective straight pipe sections 17. The plane of each weld 15, 16 is inclined with respect to a radial plane of its respective pipe section 17 at an angle of about 45° to increase fatigue life. Ends 12 and 13 include a 6 degree tapered fit to hold torque and provide ease of disassembly. End 12 includes a key 18 to align with a slot 19 in end 13 to lock sections together and allow rotational forces to be transmitted down a drill string. A streamlined nut 14 encloses end 12. Nut 14 includes a series of internal threads 21 on one end and an external hex 22 on the other end. Threads 21 of nut 14 are threadably engageable with external threads 23 on the end 13. End 13 is further equipped with a hex 24 for a wrench. Finally, end 13 provides a notch 25 which will accept an 0 ring 26 to seal end 13 to end 12. In operation successive lengths of drill line may be formed by attaching ends 12 to ends 13 and tightening nut 14 to provide a leakproof, streamlined joint that transmits rotational motion in either direction. Figure 3 is a section elevation view of a nozzle used with the invention. A section of drill pipe 31 as in Figure 2 is provided with a blank end 32 to which the female half 33 of the nozzle body is attached. Attachment may be by means of welds 34. The end of half 33 not attached to pipe 31 is provided with internal threads 36. The axis of threads 36 is inclined at an angle from the axis of pipe 31. In this case, the angle is approximately 5 degrees. The internal cavity 37 of half 33 is accordingly offset. A male half 38 of the nozzle body is threadably attachable to female half 33 by means of external threads 39. Male half 38 is further provided with an internal cavity 41 which is colinear with threads 36. The end of cavity 41 furthest from pipe 31 is provided with internal threads 42 to accept a jewel nozzle mount 43. Jewel nozzle mount provides an orifice of fluid resistant material such as synthetic sapphire from which a cutting jet 44 can emerge. The other end of cavity 41 is provided with internal threads 46 to accept a strainer support 47 which provides a support for a strainer 48. A 50 mesh screen has been found effective for use as strainer 48. The result is that if pipe 31 is rotated and supplied with high pressure fluid a rotating cutting jet 44 emerges from jewel mount 43 at about a 5 degree inclination to its axis of rotation. In operation, the nozzle is rotated by rotation of drill pipe 31 through the drill string by motor 2 in Figure 1. This produces a straight hole. This rotation is accompanied by pushing forward of the nozzle through the action of drillpipe 31 by action of motor 4 in Figure 1. To advance around a curve male half 38 is pointed in the direction in which the curve is desired and advanced without rotation. Since half 38 is offset at a 5 degree angle, the resulting hole will be curved. Half 38 can be oscillated to work around rocks. To resume a straight path rotation is restrated by activating motor 2. Figure 4 is a section elevation view of a second embodiment of the male half of the nozzle. Male half 51 is provided with a threaded end 52 joinable to the female half of the Figure 3 embodiment. The other end is provided with three jewel mounts 53, 54, 55 which are arranged in an equilateral triangle and equipped with passages 56, 57, 58 connecting them to a source of high pressure fluid. This embodiment may be more suitable for certain soil types. As many as eight nozzles may be r ecessary depending on soil conditions. Figure 5 is a section elevation view of a reamer for use in a method in accordance with the invention. The reamer is pulled back through the hole drilled by the drill to increase its diameter for larger ut lities. A male coupling 61 is at one end of the rean er and a nut 62 for attachment to a section of drill pipe as in Figure 2 (not shown) An internal passage 63 communicates with the interior of the drill pipe. A baffle cone 64 having a plurality of exit holes 66 lies in passage 63. Fluid flow is thus up the drill pipe through coupling 61 into passage 63 up baffle cone 64 through holes 66 and into the area 67 between baffle cone 64 and the interior of the reamer body 68. A plurality of passages 69-74 communicate to the exterior of the reamer body 68. Each passage 69-74 may be equipped with a jewel orifice 75-80. An end cap 81 is attached to reamer body 68 by bolts 82. 83. End cap 81 is provided with an internal cavity 84 which communicates with cavity 63 in reamer body 68 Cavity 84 includes passages 86, 87 with corresponding jet orifices 88, 89 to provide additional reaming action. Finally, cap 81 includes an attachment point 90 for attachment of a shackle 91 to pull a cable back through the hole. To ream a hole the nozzle is removed after the hole is drilled and the reamer attached by tightening nut 62. Fluid is then pumped down the drill pipe causing cutting jets to emerge from orifices 75-80 and 88 and 89. The drill pipe is then rotated and the reamer drawn back down the hole pulling a cable. The hole is thus reamed to the desired size and the utility line may simultaneously be drawn back through the hole. Figure 6 is a partial section elevation view of a nozzle incorporating a giudance system of the invention. Nozzle 101 includes a male connector 102 and nut 103 similar to the Figure 3 embodiment. A body 104 is connected to connector 102 and includes a passage 106 to allow cutting fluid to flow to an orifice 107 after passing a screen 105 in a tip 108 similar to that in the Figure 3 embodiment. Body 104 includes a cavity 109 for a battery 111 and a mercury switch 11 2. Access to cavity is via a sleeve 113 second cavity 114 for a circuit board 116. Circuit board 116 includes a transmitter and dipole antenna capable of producing a radio frequency signal when powered by battery 111. A frequency of 83 kHz has been found satisfactory. The antenna is preferably a ferrite rod wrapped with a suitable number of turns of wire. Mercury switch 112 is connected in such a manner to switch off the transmitter when - ever the tip 108 is inclined upwards. This allows a person on the surface to sense the inclination of the tip by measuring the angle of rotation at which the transmitter switches on and off. A number of methods may be used to guide the system. If the Figure 3 or 4 nozzles are used, a cable tracer transmitter can be attached to the drill string. A cable tracer receiver is then used to locate the tool body and drill string. In tests a commercial line tracer producing a CW signal at 83 kHz was used. This tracer is a product of Metrotech, Inc. and called model 810. If the Figure 6 nozzle is used the transmitter is contained in the nozzle and no transmitter need be attached to the drill string. Some tracers provide depth information as well as position. Depth can also be determined accordingly by introducing a pressure transducer through the drill string to the tip. The pressure is then determined relative to the fluid supply level. Such a method provides accuracy of plus or minus one inch (25 mm). Figure 7 is a schematic view of the transmitter. An oscillator 120 controlled by a crystal 121 producing an 80 kHz signal at 122 and a 1.25 kHz signal at 123. The 80 kHz signal passes to a modulator 124 which allows amplitude modulation of the signal and a buffer amplifier 126. The signal is then connected to a variable antenna tuning capacitor 127 to a ferrite dipole antenna 128. While no power connections are shown, it is assumed that all components are supplied with suitable working voltage. If one wants to determine the pitch of the drilling head, it is provided with an electrolytic transducer 129. The common electrode 131 of transducer 129 is grounded and the other electrodes 132, 133 are connected to the inputs of a differential amplifier 134. Electrodes 132, 133 are also connected via resistors 136, 139 and capacitor 138 to the 1.25 kHz output of oscillator 120. The output 137 of differential amplifier 134 is connected to the input of a lock-in amplifier 141 which also receives a reference signal via electrode 142. The result is a DC signal at 143 that varies with the pitch of the head. Signal 143 in turn drives a voltage to frequency converter 144, the output 146 of which is used to modulate the signal at 122. The final result is an amplitude modulated signal from antenna 128 with modulated frequency proportional to the pitch of the head. Figure 8 is an isometric view of the transducer 129. The transducer is housed in a glass envelope 151 which is partially filled with an electrolytic fluid 152. A conductive cylinder 153 is at the center of envelope 151 which is pierced with a connector 154 to cylinder 153. At either end are resistive pads 156, 157 which are, in turn, connected via electrodes 158, 159 respectively to differential amplifier 134 in Figure 7. It is readily apparent that the resistance between electrodes 158, 159 and the common electrode 154 will vary differentially with the inclination of glass tube 151. In operation the position of the drilling head is determined by above ground detectors which detect the dipole field strength and flux pattern to determine the tool's depth and direction. The detector will also pick up the amplitude modulation of the signal. The frequency of the amplitude modulation then may be used to determine the tool's pitch. For example, if V pitch is the signal's amplitude modulation and Wc is the transmitter frequency in radians/second and Wm is the modulation frequency in radians/second and m is the modulation index and since Wm is a function of pitch, we have the following relationship (T is time): V pitch is proportional to (1 + m cos WmT) cos WcT which is equal to cos WcT = m cos (Wc + Wm) T + m cos (Wc - Wm) T Therefore, if for example Wc ≅ 5 × 10⁵ radians/second Wc-Wm < ∼ 10 radians/second or Wc-Wm < < and since the terms cos (Wc + Wm) T and cos WcT can be easily filtered out, Wm can easily be determined. The enbodiments illustrated herein are illustrative only, the invention being defined by the subjoined claims.

Claims: An underground utility installation apparatus for drilling a steered underground passageway in soil or other soft material comprising a bendable tubular drill string (11) a nozzle (33, 38, 51, 104, 108) mounted on the front end of the drill string, linear drive means (3, 4) for advancing the drill string, rotary drive means (2) for rotating the nozzle (33, 38, 51, 104, 108), fluid supply means (6, 7, 8) for supplying pressurised drilling fluid to said nozzle, said nozzle being arranged to in use to generate a fluid cutting jet (44) which cuts a path offset from the axis of rotation of the nozzle with the velocity component of the jet along the axis of rotation being greater than the velocity component of the jet transverse to the axis of rotation whereby the nozzle and drill string can proceede in a straight direction using the cutting jet if advanced with rotation of the nozzle and can deviate in the direction of offset if advanced without rotation of the nozzle and a smooth tapered guide surface being provided on the head (38, 51, 108) of the nozzle inclined to the axis of rotation of the nozzle on the side opposite the direction of offset said head being asymmetrical about the axis of rotation of the nozzle whereby said cutting jet and guide surface combine to cause said nozzle and drill string (11) to proceed in a curve through soil or other soft material if advanced without rotation, said fluid supply means (6, 7, 8) supplying cutting fluid to generate the fluid cutting jet (40) both when advancing said nozzle in a straight direction during rotation and when advancing said nozzle in said direction of offset without: rotation." Apparatus according to Claim 1 wherein electronic guidance means is provided for monitoring the progress of the nozzle through the soil or other soft material . Apparatus according to Claim 1 or 2 wherein said guide surface is substantially parallel with the flow axis of said cutting jet (44). Apparatus according to Claim 1, 2 or 3 wherein said cutting jet (44) is offset laterally relative to the axis of rotation of the nozzle (33, 38, 51, 104, 108). Apparatus according to any preceding Claim wherein said cutting jet is generated from a leading end surface of the nozzle. Apparatus according to any preceding Claim wherein a further surface of the nozzle diametrically opposite said guide surface has a profile which is parallel with the axis of rotation of the nozzle (33, 38, 51, 104, 108). Apparatus according to Claim 6 where appendant to Claim 5 wherein said leading end surface extends between said further surface and the guide surface . Apparatus according to any preceding Claim wherein the drill string (11) comprises a number of sections (17) in fluid communicaticn with the nozzle and wherein the fluid supply means (6, 7, 8) includes means (6) for supplying high pressure fluid to the interior of the drill string. Apparatus according to Claim 2 or any of Claims 3 to 8 when dependent on Claim 2 wherein the electronic guidance means includes a dipole antenna (128) connected to the nozzle assembly and radio transmitter means (Figure 7) connected to the dipole antenna to provide an oscillating electric current to the dipole. Apparatus according to Claim 9 wherein the transmitter means includes pitch sensing means (112, 129) connected to the nozzle (104, 108) and arranged to control the signal transmitted by said antenna in dependence upon the sensed pitch of the nozzle. Apparatus according to Claim 9 wherein the transmitter means (Figure 7) includes an amplitude modulation means (124) to modulate the amplitude of the transmitter means signal in accordance with the pitch of the nozzle (104, 108). Apparatus according to any preceding Claim wherein sections (17) of the drill string (11) are provided with interlocking key and slot configurations (18, 19) which allow rotational forces to be transmitted along the drill string. Apparatus according to any preceding Claim wherein said rotary drive means (2) is arranged to rotate said drill string (11), and rotation of the drill string is transmitted to the nozzle (33, 38, 51, 104, 108). A method of drilling a steered underground passageway using apparatus according to Claim 1 and comprising supplying pressurised drilling fluid to the nozzle (33, 38, 51, 104, 108) to generate a fluid cutting jet, advancing the nozzle into the ground without rotation to drill a curved section and with rotation to drill a straight section, and monitoring the progress of drilling and applying correction to eliminate any deviation from the desired path. A method according to Claim 14 wherein the monitoring step is accomplished by means of a radio transmission from the vicinity of said fluid jet to a receiver at the surface level. A method according to Claim 14 or Claim 15 further including a step of monitoring a pitch of the fluid jet drill. A method according to any one of Claims 14 to 16 further comprising replacing the nozzle by a reamer and reaming the hole as the drill string and reamer are pulled back through the hole. A method of installing a utility line comprising drilling a hole by the method of Claim 15, and towing the utility line through the drilled hole by connecting it to the drill string and pulling the drill string and utility line back through the drilled hole. A method according to Claim 18 wherein the utility line is connected with the drill string by connecting it to the reamer.

Inventors: GELLER EDWARD, KIRBY MIKE, MERCER JOHN, O'HANLON TOM, REICHMAN JIM, SVENDSEN ROBERT, THEIMER KEN, GELLER, EDWARD, KIRBY, MIKE, MERCER, JOHN, O'HANLON, TOM, REICHMAN, JIM, SVENDSEN, ROBERT, THEIMER, KEN
Applicants: UTILX CORP, UTILX CORPORATION
Application year: 1986
Main classification: E21B7
IPC codes: E21B7, E21B47, E01B7