Underground Construction - September 2021 - 28

Directional Drilling
Mini-HDD for Placement of HDPE Pipe
in Municipal Applications
Dr. Lawrence M. Slavin
A new set of guidelines for the use of mini-horizontal directional
drilling (mini-HDD) has been developed by the Municipal Advisory
Board (MAB) of the Plastics Pipe Institute (http://plasticpipe.org).
Previously available as Technical Report TR-46, the new
document, MAB Guidelines for Use of Mini-Horizontal Directional
Drilling for Placement of HDPE (PE4710) Pipe in Municipal
Applications, specifi cally addresses water lines, including
potable water and sewer. Designated as MAB-7, the document
provides detailed information for both IPS- and DIPS-size pipes,
constructed of the latest PE4710 material.
Th e document is analogous to ASTM F1962, Standard Guide
for Use of Maxi-Horizontal Directional Drilling for Placement of
Polyethylene Pipe or Conduit Under Obstacles, Including River
Crossings, but at a level appropriate for the less complex miniHDD
technology, and typical project characteristics, as compared
to maxi-HDD installations.
Technical Report MAB-7 comprises 10 main sections, plus
six appendices and references. In particular, guidelines are
provided for proper drill rig positioning, consistent with meeting
required placement depths and drill rod capabilities. In addition,
it provides a practical methodology for estimating the relevant
forces and eff ects present during installation, based on the route
geometry, facilitating proper selection of the pipe wall thickness.
Bore planning, rig setup
FIGURE 1 illustrates a typical mini-HDD bore vertical profi le
trajectory, including occasional pits along the route. Th ese
pits may be required for pipe splicing, completing lateral
connections, or to expose existing utilities. FIGURE 1 designates
certain points along the bore path and their relative distances
from the drill rod entry or exit points.
Th ese distances are a function of the entry angle and drill
rod characteristics (e.g., allowable radius of curvature, or
" bend radius " ), and determine the setup location and space
requirements in which to perform and complete the pipe
Safe Pull Tension (lbs), HDPE (PE4710) Pipe, 1 hour
IPS
Nominal
Size
FIGURE 1 Drill Rig Setup and Related Distances
(Source: Outside Plant Consulting Services, Inc.)
2-in.
3-in.
4-in.
6-in.
8-in.
10-in.
12-in.
7
3,038
6,597
10,906
23,638
40,064
62,237
87,549
Pipe Diameter to Thickness Ratio (DR)
9
11
2,450
5,321
8,796
19,066
32,315
50,200
70,616
-
-
7,361
15,954
27,040
42,006
59,090
13.5
-
-
6,109
13,240
22,441
34,861
49,039
Safe Pull Tension (lbs), HDPE (PE4710) Pipe, 1 hour
DIPS
Nominal
Size
3-in.
4-in.
6-in.
8-in.
FIGURE 2 Drill Rig Minimum Setback Distance
Drill Rods: 10 ft Long, 100 ft Radius of Curvature
(Source: Outside Plant Consulting Services, Inc.)
28 SEPTEMBER 2021 | UCONonline.com
10-in.
12-in.
7
8,445
12,408
25,641
44,109
66,356
93,838
Pipe Diameter to Thickness Ratio (DR)
9
11
6,812
10,008
20,681
35,578
53,522
75,689
-8,375
17,306
29,771
44,786
63,335
13.5
-6,950
14,362
24,707
37,168
52,562
17
-5,610
11,593
19,943
30,002
42,428
17
-
-
4,931
10,687
18,114
28,140
39,584
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Underground Construction - September 2021

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