Page 58 - Trenchless Technology Piping Installation and Inspection

New Pipeline Installations 31

FIGURE 1.23 Impact moling. (Source: TT Technologies.)

1.7 Characteristics and Applications of Trenchless
Construction Methods
This section provides information on the various trenchless methods
and their applicability to the individual types of pipelines and utility
installations. Restriction on the selection of a construction method
may include ground conditions, availability of experienced trench-
less technology contractors and appropriate equipment, cost, safety,
and the technical feasibility of the method desired. The materials pre-
sented in this section should only be used as a guide. Each project is
unique and for a safe and successful operation, judgment of a profes-
sional engineer knowledgeable in trenchless technology methods is
required. Standard pipe sizes, bore lengths, and bore depths are con-
siderations in determining the appropriate method. Table 1.5 pres-
ents main characteristics of trenchless methods for new installations
including range of lengths and diameters. Table 1.6 provides appro-
priate techniques for specific applications.
Table 1.7 presents minimum safe installation depths for various
trenchless installation methods categorized into different pipe diame-
ters and soil conditions. While minimum installation depths depend
heavily on subsurface conditions, method used and pipe diameter,
other factors such as type of trenchless equipment used, operator’s
skills, project location, surface conditions, and adjacent utilities and
structures are also important. It should be noted that as technology
develops, each method may expand its capabilities including range of
depth, length, and diameter applications. The installation depth should
be determined on case-by-case basis, considering all the risks.
Table 1.8 presents selection of trenchless method based on the type
of pipe, pipe installation, and method of excavation and soil removal.