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Texas Directional Directional Bore | Boring Pilot Hole

Texas Directional Directional Bore | Boring Pilot Hole

Pilot Bore:

A pilot (bore) hole is a small hole drilled as a guide for the boring of a larger hole.

The action of creating the first (usually steerable) pass of any directional boring process, which later requires back reaming or similar bore hole enlargement.

The process begins when a directional bore machine pushes a bore head connected to hollow pipe into the ground at an angle. As each joint of drill pipe is pushed into the ground a new joint of pipe is added behind and torqued until it reaches its predefined destination and exit point.

Texas Directional Directional Bores | Pipe Reaming

Texas Directional Directional Bores | Pipe Reaming


Upon reaching the destination exit point, the drill bit is detached and the end of the drill pipe is attached to a reamer or hole opener (for rock) if the borehole must be enlarged. The reamer is pulled back while rotating the drill pipe with as many consecutive passes as needed to enlarge the hole. Drill pipe is added behind the reamer or hole opener so that there is always drill pipe in the borehole.

Texas Directional Directional Boring | Pipe Pull-Back

Texas Directional Directional Boring | Pipe Pull-Back

Pull Back:

Pull-back is the part of the horizontal directional boring process in which the drill string is withdrawn through the bore back to the entry pit, usually installing the product pipe at the same time.

The success of a horizontal directional boring (HDD) drill is largely dependent on the success of the pull back operation, when the product pipe is installed in the created borehole. The cost of damaging pipeline and the costs for additional measures during and after the pull back operation can be considerable if not managed properly.

Some of the problems which might occur during a pull back operation vary from uncompleted pull back operations to slight coating damages.

When the bore hole is approximately 25% larger than the product pipe to be installed, the end of the product pipe is connected to a reamer or barrel reamer and then a swivel attached to the pipe to be installed and pullback commences.