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| Reinforced polypropylene (1.1mm) |
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Pages in this section include:
| Description |
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Reinforced polypropylene (PPR) is similar to unreinforced polypropylene
(PPU) but has a backing of a fibrous material or can be internally
reinforced with scrim. PPR has the advantage of higher strength
and lower measured strains when placed under stress. Its disadvantage
is that it has lower thermal expansion properties than PPU.
PPR often has a geotextile underlay to provide additional protection
from damage by sharp protrusions in the subgrade layer. An overlay
of geotextile can also be used to provide protection from sharp
angular soil cover.
| Experience |
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A PPR trial was conducted along a 200m test section of Finley Main
Channel by Murray Irrigation Limited.
| Site
preparation |
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Subgrade preparation required:
- Bank reprofiling.
- Silt and clod removal.
| Installation |
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Method of installation
Installation occurred during July 2003. The material
arrived in 150m rolls 4.5m wide. To allow easier
installation and reduce labour requirements on site,
and reduce the amount of joining in wet and dirty
site conditions, some workshop fabrication was undertaken.
Panels were welded together in the workshop and folded
up like a tarpaulin for transport to the site. A
crew of six was required to unfold and manoeuvre
the material into place and join the panels.
Prefabrication of the PPR in the workshop was completed
using a fusion welder, with in-situ joins being completed
by a light-weight welder.
Approximately one full day was spent prefabricating
the material in the workshop (three workers from
the supplier), with 1.5 days required for the installation.
The liner was anchored in trenches along the channel
bank and the end treatment utilised geosynthetic
clay lining (GCL).
 Figure 1 Channel section near completion
Specialised equipment
Specialist welding tools.
Installation Issues
Conditions were less than ideal for the installation,
with the channel bed being quite wet due to 50mm of rainfall
in the preceding two weeks. In addition to this, groundwater
intrusion necessitated regular pumping to dewater the channel.
Water ponded in the bottom of the liner and caused difficulties
during welding. Effort was required in order to keep the joins
clean during welding.
Because of the flexibility of the material the last 5m of material
at every join was able to be folded back on itself to enable
the material to be joined in a clean and dry environment above
the previous sheet. This negated the need to place PPR off-cuts
as drop sheets in the channel beneath each join, and meant that
all the material was available to achieve the full 200m trial.
Access to the site was restricted due to wet conditions. A fence
on one side of the channel also limited access. Only vehicles
with tracks could access the site.
Weather
considerations
Wind conditions during installation were calm. Windier conditions
would cause significantly greater installation problems, particularly
with large sections of material.
| Durability |
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No literature reporting PPR’s longevity is
available, but the supplier estimates a useful life
of 20 years.
| Seepage
reduction |
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The baseline seepage
rate at the PPR site
in the Finley Main Channel
is 5.2L/m2/day. No post-remediation
pondage tests have been
undertaken as yet.
| Cost |
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A breakdown of the costs is presented in the table below. The total
lining cost of $60,912 (2003), or $16.92/m2, is based on a supplied
surface area of 3,600m2.
Table 1 Breakdown of costs for PPR (1.1mm)
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Item
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Cost ($)
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Cost ($/m2)1
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Earth works (excavator, loader, etc.)
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$3,322 |
$0.92 |
| Materials |
$38,000 |
$10.55 |
| Delivery |
$1,400 |
$0.38 |
| Installation |
$12,000 |
$3.33 |
| MIL staff wages, on-costs, etc. |
$3,230 |
$0.90 |
| Fencing |
$1,710 |
$8.55/m |
| Misc. |
$1,250 |
$0.35 |
| TOTAL |
$60,912 |
$16.92 |
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1. Cost per square metre based on 3,600m2 of material supplied.
2. Cost per metre of fencing based on 200m section of channel.
Cost for materials and installation are specific to this
job. Costs for materials and transport would be reduced in
larger applications. Other costs would be expected to reduce
marginally as economies of scale in earth works, installation,
utilisation of staff, and fencing are achieved. The costs
are exclusive of GST.
| Advantages
and disadvantages |
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Advantages
- Despite some unfavourable conditions in the form of
the wet subgrade, installation of the PPR was considered
to be quite good.
Disadvantages
- PPR is not suited to installation under windy conditions,
as this makes it difficult to lay the material, and can
cause the sheets to move during welding.
- Wet subgrade
conditions can interfere with the welding process.
- Exposed
installations require fencing to prevent risk of damage
by animals.
| Related
pages |
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Flexible membrane lining
techniques
Flexible
membrane materials
Covered liners
High-density
polyethylene (0.75mm)
Geosynthetic
clay liners
Exposed liners
High-density
polyethylene (2mm exposed)
High-density
polyethylene (1.5mm exposed)
Linear
low-density PE and very low-density PE
(1.5mm)
DamSeal
Unreinforced
polypropylene (1mm)
Unreinforced
polypropylene (0.75mm)
Butyl
rubber
Asphalt |
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