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| Clay lining example: Channel 12 |
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Pages in this section include:
| Site
preparation |
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Before commencement of clay lining works, the channel was desilted
and remodelled with batter slopes of 1:2. The banks and batters
were stripped to a minimum depth of 200mm to remove all topsoil,
trees and root systems. The stripped foundation was then ripped
to a minimum depth of 200mm and then compacted.
| Installation |
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Design features included:
- 600mm clay lining in bed
- 750mm clay lining on batters
- 1:2 batter slope
- 300mm compacted freeboard
- 150mm protective cover over the
bank crest to minimise shrinkage and dispersion and encourage
grass cover.
Method of installation
The clay was sourced from borrow sites which were tested to
have an Emerson Class Number of 4 or greater in accordance
with AS1289
3.8.1. The clay material was within 2% of optimum moisture content
and had a liquid limit less than 35 in accordance with AS1289
3.1.1. It was placed in layers not exceeding 150mm and compacted
by track
rolling with a dozer to achieve 95% minimum dry density. The
compaction achievements were confirmed by laboratory testing.
A protective
cover was placed that comprised topsoil from stripping, and other
material with a liquid load limit less than 35, containing organic
material, and with a pH between 6 and 8.
Specialised equipment
Earthmoving and compaction equipment required is readily available
to water authorities and earthworks contractors.
Installation issues
Compaction was difficult in one section of channel due to the
nature of the underlying bed material. Generally, all works went
to plan,
and significant time savings were made because the width of the
channel allowed stripped material to be left on site rather
than hauled away.
| Durability |
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The estimate lifespan of clay lining is 30 years, and the presence
of a protective cover can extend this.
| Seepage
reduction |
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The baseline seepage rate was between 3.4 and 6.7L/m2/day. While
there has been no post-remediation monitoring of seepage rates,
clay lining is estimated to have reduced seepage by 70-90%.
| Cost |
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The final cost of earthworks was $201,000 (2002), which over
a channel surface area of 12,400m2 corresponds to a lining cost
of
$16.20 per m2.
These costs were achieved by sourcing the clay from a nearby
dam, and avoiding haulage of the stripped material.
| Related
pages |
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Earthen lining techniques
Compacted earthen liners
Clay lining example: Waranga Western
Channel
Other Australian examples
Channel bank lining
Loose earthen linings
Bentonite treatments
Modified soil earthen linings
Soil sealants |
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