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Existing Pipeline Renewal and Replacement Methods 67

2.5 Emerging Design Concepts for Pipeline
Renewal Systems*
A conventionally buried pipe is designed to “carry” or “transfer” all
the loads, which includes the weight of soil backfill placed over it,
hydrostatic pressures, vacuum, internal working pressures, and loads
applied at the ground surface. As mentioned earlier, current methods
for structural design of flexible gravity pipe liners by the Appendix X1
of ASTM F1216-09 consider two external load cases for dimensioning
of the liner pipe. The first is sustained hydrostatic pressure due to
groundwater acting in the annular space between the liner pipe and
the existing pipe. The second load case assumes that overtime earth
and traffic loads will be transferred from the existing pipe-soil struc-
ture to the new liner pipe. This concept is particularly true in the
treatment of the “fully deteriorated pipe condition” by ASTM F1216-
09, for two reasons described below:
1. The soil load reaching the liner pipe is overestimated by treat-
ing the liner as it had been directly buried in a trench. The
more correct liner pipe condition, even in circumstances where
the existing pipe may continue to deteriorate after renewal,
is a tunnel lining situation (Schrock and Gumbel, 1997).
2. The formula used to describe liner pipe response to transferred
soil load, and hence calculate the required wall thickness, has
been incorrectly modified from an already conservative theory
for open-cut applications, which entail further irrational safety
factors (Gumbel, 1998).

The basic design concept proposed at the ASCE Pipeline Division
Web site (www.pipelinedivision.org) is to develop buckling pressure
or safe water head charts for each renewal technique. These charts
incorporate existing pipe imperfections, but allow variations of the
existing pipe imperfections. The most appropriate form of chart may
vary according to the type of renewal technique and/or liner material
(ASCE, Pipeline Division). Reader is encouraged to refer to the publi-
cations by ASCE pipeline division for more information.

2.5.1 Long-Term Testing
The design life of pipeline systems has always been a major con-
cern due to early deterioration of some pipe materials as well as
unexpected and excessive repair and maintenance costs. For
example, there are limited established design methodologies for
all pipe lining systems. The existing ASTM Standard F1216-09,

∗For more information see www.pipelinedivision.org.