Method and apparatus for on-grade boring

• US 20030152428A1
• Filed: 12/20/2002
• Published: 08/14/2003
• Est. Priority Date: 12/20/2001
• Status: Active Grant

• Current Assignee: Earth Tool Company LLC (Charles Machine Works Incorporated The)
• Original Assignee: Earth Tool Company LLC (Charles Machine Works Incorporated The)
• Inventors: Wentworth, Steven W., Crane, Robert F., Randa, Mark D.
• Granted Patent: US 7,086,808 B2
• Time in Patent Office: Days
• US Class Current: 405/184.2
• CPC Class Codes: E02F 5/10 with arrangements for reinforcing trenches or ditches; with arrangements for making or assembling conduits or for laying conduits or cables laying pipes per se F16L1/00, making pipes in situ F16L1/038; laying electric cables per se H02G1/06; drainage device- laying apparatus E02B11/02
• CPC Class Codes: E21B 10/40 with leading portion
• CPC Class Codes: E21B 7/064 specially adapted drill bits therefor
• CPC Class Codes: E21B 7/30 without earth removal
• CPC Class Codes: F16L 55/1658 the old pipe being ruptured prior to insertion of a new pipe
• CPC Class Codes: H02G 1/06 for laying cables, e.g. laying apparatus on vehicle

Abstract

A method for installation of an underground pipe includes an initial step of boring a pilot hole through the ground at a predetermined grade angle by extending a drill string having a steerable boring bit mounted thereon through the ground. Upon reaching an end location for the pilot hole, the bit is removed from the drill string, and an expander having a diameter greater than the pilot hole is attached to the drill string, which expander is backed by an impact device such as a pneumatic impactor including a striker that delivers repeated impacts to a rearwardly facing surface of the expander, and by a pipe drawn along behind the expander. The expander is pulled back through the pilot hole at the grade angle while the impactor is operated to aid progress of the expander through the ground and pull the pipe into place behind the expander. Typically in this method the replacement pipe is coupled to a rear end of the expander and the boring bit has a sonde housing containing a sonde attached thereto to indicate to an operator the orientation of a steering face on the boring bit.

Claims

1. A method for installation of an underground pipe, comprising

boring a pilot hole through the ground at a predetermined grade angle by extending a drill string having a steerable boring bit mounted thereon through the ground;

upon reaching an end location for the pilot hole, removing the bit from the drill string and attaching an expander having a diameter greater than the pilot hole to the drill string, which expander is backed by an impact device including a striker that delivers repeated impacts to a rearwardly facing surface of the expander, and by a pipe drawn along behind the expander; and

pulling the expander back through the pilot hole at the grade angle while operating the impactor to aid progress of the expander through the ground and pulling the pipe into place behind the expander.

2. The method of claim 1, wherein the pipe is coupled to a rear end of the expander.

3. The method of claim 1, wherein the grade angle is in the range of 0.1 to 5 degrees.

4. The method of claim 1, wherein the boring bit has a sonde housing containing a sonde attached thereto to indicate to an operator the orientation of a steering face on the boring bit, and the boring bit has an outer diameter that does not substantially exceed the outer diameter of the sonde housing.

5. The method of claim 1, wherein the expander moves forwardly over a short distance in response to an impact from the striker without transmitting any substantial impact force to the drill string.

6. The method of claim 1, further comprising:

securing a cutting back reamer to the drill string ahead of the expander, which cutting back reamer has a maximum outer diameter no more than 90% of the maximum outer diameter of the expander,

rotating the drill string and cutting back reamer during the pulling step independently of the expander and impact device, which do not substantially rotate due to a rotatable connection between the cutting reamer and the expander.

7. The method of claim 6, wherein the cutting back reamer is configured to permit steering of the cutting reamer, further comprising correcting deviations from grade by steering using the cutting reamer.

8. The method of claim 1, wherein the impactor is a pneumatic impactor, further comprising supply compressed air to the impactor through a lengthwise flow passage in the drill string, cutting reamer and expander.

9. The method of claim 1, further comprising:

supplying a drilling fluid through the drill string, which fluid flows throw a flow passage in the cutting back reamer out into surrounding soil; and

wherein the impactor is a pneumatic impactor, further comprising supply compressed air to the impactor through a hose disposed in the product pipe.

10. A method for installation of an underground pipe, comprising

boring a pilot hole through the ground at a predetermined grade angle by extending a drill string having a steerable boring bit mounted thereon through the ground;

upon reaching an end location for the pilot hole, removing the bit from the drill string and attaching a drill head including a cutting reamer having a diameter greater than the pilot hole to the drill string, which cutting reamer is configured to permit steering when rotated over less than 360 degrees and is backed by a device for pulling a pipe along behind the expander, the device including a rotatable connection whereby the cutting reamer can rotate in unison with the drill string without substantial rotation of the pulling device and pipe;

pulling the pipe back through the pilot hole at the grade angle,

detecting deviations of the pipe from the grade angle; and

steering using the cutting reamer to correct deviations from the grade angle.

11. The method of claim 10, wherein the drill head includes an expander having a diameter greater than the diameter of the cutting reamer, which expander is backed by an impact device including a striker that delivers repeated impacts to a rearwardly facing surface of the expander effective to form a hole for the underground pipe by compaction.

12. The method of claim 11, wherein the pipe is coupled to a rear end of the drill head.

13. The method of claim 10, wherein the grade angle is in the range of 0.1 to 5 degrees.

14. The method of claim 10, wherein the cutting reamer has a forwardly tapering, generally conical shape with a cut away steering face on one side thereof.

15. The method of claim 10, wherein the cutting reamer has a forwardly tapering, generally conical shape and is mounted non-concentrically relative to the drill string.

16. An apparatus for installation of an underground pipe, comprising:

a forwardly tapering cutting back reamer having front and rear connecting portions, wherein the front connecting portion is configured for attaching the cutting back reamer to a drill string for rotation therewith, and the rear connection portion includes a bearing joint;

an expander connected to the cutting back reamer by the bearing joint so that the expander does not substantially rotate as the drill string and cutting reamer rotate, which expander has a larger outer diameter than the cutting back reamer and is configured to form a hole by compaction of surrounding soil; and

an impact device including a striker that delivers repeated impacts to a rearwardly facing surface of the expander.

17. The apparatus of claim 16, further comprising means for pulling a pipe along behind the expander and impact device.

18. The apparatus of claim 16, further comprising a tubular body having substantially the same outer diameter as a maximum outer diameter of the expander, which tubular body extends rearwardly from the expander, wherein a ratio of effective length of the expander and body to the diameter of the body is at least 3.5 to 1.

19. The apparatus of claim 16, wherein the cutting back reamer has a maximum outer diameter no more than 90% of the maximum outer diameter of the expander.

20. An apparatus for installation of an underground pipe, comprising:

a forwardly tapering cutting back reamer having front and rear connecting portions, wherein the front connecting portion is configured for attaching the cutting back reamer to a drill string for rotation therewith, and the rear connection portion includes a bearing joint, wherein the cutting back reamer is configured to permit steering of the cutting reamer by rotation through less than 360 degrees and return to its starting position for one or more cycles,

means connected to the bearing joint for pulling a pipe along behind the cutting back reamer without substantial rotation of the pipe.

21. The apparatus of claim 20, further comprising a sonde housing mounted in alignment with a steering portion of the cutting back reamer for rotation therewith to indicate to an operator the orientation of the steering portion of the back reamer.

22. The apparatus of claim 21, wherein the cutting back reamer has a generally conical shape, and the steering portion comprises a cut away steering face on one side thereof.

23. The apparatus of claim 21, wherein the cutting reamer has a forwardly tapering, generally conical shape and is mounted non-concentrically relative to the drill string, such that the steering portion comprises an eccentrically extending portion of the cutting reamer.

24. A method for installation of an underground pipe, comprising

boring a pilot hole through the ground at a predetermined grade angle by extending a drill string having a steerable boring bit mounted thereon through the ground;

upon reaching an end location for the pilot hole, removing the bit from the drill string and attaching a drill head including a steerable expander having a diameter greater than the pilot hole to the drill string, which steerable expander is configured to permit steering when rotated over less than 360 degrees, an impact device including a striker that delivers repeated impacts to a rearwardly facing surface of the steerable expander, a rotatable connection whereby the steerable expander can rotate in unison with the drill string without substantial rotation of the impact device and pipe, and a pipe drawn along behind the expander;

pulling the pipe back through the pilot hole at the grade angle while operating the impactor;

detecting deviations of the pipe from the grade angle; and

steering using the steerable expander to correct deviations from the grade angle.

25. An apparatus suitable for use in a back reaming step of a method for installation of an underground pipe, comprising:

a steerable expander having a steering surface;

an adapter on which the steerable expander is mounted for unison rotation with the adapter;

a sonde housing containing a sonde that is mounted in a position effective to indicate the orientation of the steering surface of the steerable expander;

an impact device including a striker that delivers repeated impacts to a rearwardly facing surface of the steerable expander;

a rotatable connection whereby the steerable expander can rotate in unison with the adapter and sonde housing without substantial rotation of the impact device and a pipe drawn along behind the impact device.