Underground Infrastructure - March 2023 - 21

DIRECTIONALDRILLING
HDD and HDPE - The Perfect Match
Now Available: ASTM Guide for Use of Maxi-HDD Placing HDPE Pipe Under Obstacles
Lawrence M. Slavin, Ph. D
ASTM F1962, Standard Guide for Use of Maxi-Horizontal
Directional Drilling for Placement of Polyethylene Pipe or Conduit
Under Obstacles, Including River Crossings, was originally
approved in 1999, following development within the ASTM's
F17.67 Trenchless Technology Subcommitt ee. It was reissued
in 2005 and 2011, and previously reinstated in 2020.
Corresponding changes to the document, if any, were minimal,
including providing additional or updated references.
Th e most signifi cant was to the alternative guidelines TR-46
provided by the Plastics Pipe Institute (which has been superseded
by its Municipal Advisory Board's MAB-7), as more
appropriate for mini-HDD operations.
However, the latest revision of ASTM F1962, approved in
2022, contains a signifi cant change by providing the physical
properties for the most-recent, high-density polyethylene
(HDPE) material, PE4710. Th is material is signifi cantly
tougher than older, previous polyethylene (PE) products, facilitating
successful completion of more complicated, diffi cult
maxi-HDD projects.
Allowable pulling loads are based on a minimum tensile
yield strength of 3,500 pounds per square inch (psi), with a
signifi cant reduction to limit non-recoverable viscoelastic deformation,
as well as account for the eff ective cumulative load
duration on the pipe (assumed to be 12 hours), resulting in a
safe pull stress of 1,330 psi.
Its convenient methodology for selecting an appropriate
pipe strength (wall-thickness), based on the project characteristics,
has led to its increasing popularity and widespread
usage within industry. ASTM F1962 is the only available
ASTM standard for HDD.
Overview
Th e ASTM document provides overall guidelines for a maxiHDD
operation, addressing preliminary site investigation;
safety and environmental considerations, regulations and
damage prevention; bore path layout and design; implementation;
and inspection and site cleanup. FIGURE 1 illustrates the
operation in a city or urban application.
One of the most signifi cant contributions of ASTM F1962
is the provision of a rational, analytical method for selecting
the pipe strength based on estimated installation loads on the
PE pipe. Th us, ASTM F1962 provides a means of determining
project feasibility, as well as initial design information.
Such results could be further refi ned by competent engineering
expertise, including analysis of pipe and soil characteristics
and interaction, oſt en including the use of relatively sophisticated
soſt ware tools, possibly based on the ASTM F1962
methodology. Th e procedure is straightforward and has been
incorporated into various soſt ware tools, as an engineering and
design aid for such projects.
Th e ASTM standard specifi cally addresses polyethylene
(PE) pipe, a fl exible product, for which the eff ects of any bending
stiff ness on drag forces at route bends or path curvature may
be ignored. Relevant material properties for PE pipe, such as
FIGURE 1. Typical Maxi-HDD Operation (Courtesy of Murphy Pipeline
Contractors)
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