System And Apparatus For Locating And Avoiding An Underground Obstacle

Abstract

A method and apparatus for detecting and avoiding an underground object during a horizontal directional drilling operation. The apparatus comprises a boring tool with a ground penetrating radar detection system. The boring tool is operatively connected to a drill string and advanced through the earth to create a borehole. The radar detection system includes at least one transmitter, at least one detector, and a processor. The transmitter is located on a surface of the boring tool and is adapted to transmit electromagnetic waves. At least one detector is located on the surface of the boring tool, and detects the electromagnetic waves reflected by underground objects. The processor determines the location of the underground object from characteristics of the reflected waves. Using this information, the drill string may be pulled back up the borehole or redirected to avoid the object. The boring tool may be caused to breakout of the existing borehole using a pivoting boring tool. Alternatively, a shoe protruding from the boring tool may be engaged to push the boring tool into an opposite wall of the borehole.

1 . An apparatus for redirecting a drill string from an existing borehole, the apparatus comprising:
 a housing supported on the drill string;   a drill bit operatively connected to the housing; and   a redirection assembly adapted to force the drill bit into a side wall of an existing borehole at a point remote from an end of the existing borehole.   
   
   
       2 . The apparatus of  claim 1  further comprising an underground object locating system. 
   
   
       3 . The apparatus of  claim 2 , wherein the underground object locating system comprises:
 at least one transmitter located proximate the drill bit, wherein said transmitter is adapted to transmit electromagnetic waves;   at least one receiver located proximate the drill bit, wherein said receiver is adapted to detect electromagnetic waves reflected from underground objects; and   a processor adapted to determine a location of the underground object using the waves detected by the receiver.   
   
   
       4 . The apparatus of  claim 3  wherein the at least one transmitter transmits ground penetrating radar. 
   
   
       5 . The apparatus of  claim 1  wherein the redirection assembly comprises:
 a shoe operatively connected to the housing; and   an extension assembly operatively connected to the shoe;   wherein the extension assembly operates to extend the shoe from the housing.   
   
   
       6 . The apparatus of  claim 5  wherein the extension assembly comprises a piston. 
   
   
       7 . The apparatus of  claim 5  wherein the drill bit comprises a slant-faced bit. 
   
   
       8 . The apparatus of  claim 7  wherein the shoe is extended from the housing proximate the slant-faced side of the drill bit. 
   
   
       9 . The apparatus of claim  21  wherein the redirection assembly comprises a rotation assembly supported by the housing, wherein the rotation assembly is adapted to pivot the drill bit relative to the housing. 
   
   
       10 . The apparatus of  claim 9  wherein the drill bit comprises a slant-faced bit. 
   
   
       11 . The apparatus of  claim 9  wherein the rotation assembly comprises:
 a gearhead supported in the housing;   a cam mechanism operatively coupled to the gearhead and the drill bit; and   a pivot pin adapted to rotatably connect the housing to the drill bit; and   wherein rotation of the gearhead causes the cam mechanism to pivot the drill bit about the pivot pin.   
   
   
       12 . A method for redirecting a drill string from an existing borehole, the method comprising:
 detecting an object in a projected path of a drill bit on an end of a drill string;   retracting the drill string a predetermined distance in the borehole such that the drill bit is at a position remote from an end of the borehole;   pivoting the drill bit at the end of the drill string such that the drill bit is forced into a side wall of the borehole; and   advancing the drill string without rotation so the drill bit exits the borehole through the side wall of the borehole.   
   
   
       13 . The method of  claim 12  wherein the drill string is retracted 5 feet from the end of the borehole. 
   
   
       14 . The method of  claim 12  further comprising advancing and rotating the drill bit so a new borehole is created.