Page 389 - Trenchless Technology Piping Installation and Inspection

Inspection and QA/QC for Trenchless Installation and Replacement Methods 339

off-site. Precautions must be taken to ensure worker safety if
removal of soil is accomplished through the use of a foam pig
and compressed air.

Overcut Allowance
3
The standard overcut is between / and / in. over radius both on the
1
4 4
outside and inside of the casing pipe. Overcut up to 1 in. can be per-
mitted depending on the diameter of the ramming tool, depth and
ground conditions leaving the 6 o’clock open.
Watertight Joints
Soil tight pipe joints are required to ensure the integrity of the road-
bed. Pipe must be constructed to prevent earth infiltration through-
out its entire length.

Lubrication Fluids
1. Lubrication must be made of bentonite, water, and/or poly-
mers and used for inside and sometimes outside of the pipe.
2. A lubrication system must be provided that injects lubricant
on the inside to facilitate spoil removal and sometimes out-
side of the pipe to lower the friction developed on the sides of
the pipe during ramming.
Figure 8.21 suggests a checklist for inspection of pipe-ramming
operations.

8.6 Horizontal Directional Drilling

8.6.1 Introduction
The elements of an horizontal directional drilling (HDD) installation
are (see Fig. 8.22)

1. A rig, which provides the physical means—thrust and torque,
to open the borehole and pull in the product.
2. A transmitter/receiver system for tracking the location of the
bore.
3. The down-hole equipment—drill pipe, drill bits, and reamers,
which converts the physical capabilities of the rig to open the
borehole and pull in the product.
4. The drilling fluid, which serves to stabilize the borehole, cools
the down-hole equipment, and removes the spoils from the
borehole.