Geosynthetics October/November 2019 - 21

Soil investigation should contain consolidation tests to specify settlement during and after the construction period.
If there are no data available, a settlement assumption must be done based on
experience in comparison with similar
soils. It may be useful to install measuring points on the surface of the sludge
to allow control of settlement during
the filling process and verify against the
estimated values, thereby adjusting the
gradient if necessary.
Geosynthetic selection and
installation methods
Typically, woven fabric, geogrids or composite materials like woven/geogrid or
geogrid/nonwoven can be selected for
the capping system. The main function of
woven fabrics and geogrids is to transfer
into the anchor trench tensile stresses
resulting from soil and traffic load across
a larger area. In addition, a nonwoven can
also work as a separator and filter to keep
sludge in place below the geotextile.
Depending on the chemical characteristics of the tailings, different raw
materials should be selected. Normally
polypropylene (PP), polyester (PET, PES)
and polyvinyl alcohol (PVA) can be used
in a normal pH range from 2 to 9.5. In
areas with pH 10 to 13 where long-term
stability must be considered in the design,
only PP and PVA may be used.
The installation of the geosynthetics
depends on the size of the pond and on
the tailings characteristics. It can be done
by unrolling and overlapping them or by
sewing a large panel pulled by external
edges into the pond.

Cover system: Pond 4
The cover consists of the succession of
mineral soils and geosynthetics designed
according to the storage and evaporation
principle with a total thickness of about
6.6 feet (2 m).

FIGURE 2 Typical cover system cross section

The final cover contains the following layers (from the bottom to the top)
(Figure 2):
* tailings
* nonwoven
* two layers of geogrids (installed perpendicularly to each other-T-shape)
* vertical drains
* mineral drainage and bearing layer
* mineral sealing layer ensuring
hydraulic conductivity k ≤ 1∙10-9 m/s
* soil cover
Vertical drains have been included in
the system to make possible the installation of the mineral layer on a very soft
subgrade (i.e., saturated tailings); a nonwoven geotextile was used as a separation
and filtration layer; and two crosswise
geogrids were introduced into the system
as a reinforcement element.
Depending on the position, the stored
tailings differ in their physical behavior.
According to the tailings characteristics, three main different areas can be
identified (Figures 3a and 3b on page
22). While the tailings in the outer edge
and middle region can be considered
as partially dewatered and partially
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Geosynthetics October/November 2019

Table of Contents for the Digital Edition of Geosynthetics October/November 2019

Geosynthetics October/November 2019 - Cover1
Geosynthetics October/November 2019 - Cover2
Geosynthetics October/November 2019 - 1
Geosynthetics October/November 2019 - 2
Geosynthetics October/November 2019 - 3
Geosynthetics October/November 2019 - 4
Geosynthetics October/November 2019 - 5
Geosynthetics October/November 2019 - 6
Geosynthetics October/November 2019 - 7
Geosynthetics October/November 2019 - 8
Geosynthetics October/November 2019 - 9
Geosynthetics October/November 2019 - 10
Geosynthetics October/November 2019 - 11
Geosynthetics October/November 2019 - 12
Geosynthetics October/November 2019 - 13
Geosynthetics October/November 2019 - 14
Geosynthetics October/November 2019 - 15
Geosynthetics October/November 2019 - 16
Geosynthetics October/November 2019 - 17
Geosynthetics October/November 2019 - 18
Geosynthetics October/November 2019 - 19
Geosynthetics October/November 2019 - 20
Geosynthetics October/November 2019 - 21
Geosynthetics October/November 2019 - 22
Geosynthetics October/November 2019 - 23
Geosynthetics October/November 2019 - 24
Geosynthetics October/November 2019 - 25
Geosynthetics October/November 2019 - 26
Geosynthetics October/November 2019 - 27
Geosynthetics October/November 2019 - 28
Geosynthetics October/November 2019 - 29
Geosynthetics October/November 2019 - 30
Geosynthetics October/November 2019 - 31
Geosynthetics October/November 2019 - 32
Geosynthetics October/November 2019 - 33
Geosynthetics October/November 2019 - 34
Geosynthetics October/November 2019 - 35
Geosynthetics October/November 2019 - 36
Geosynthetics October/November 2019 - 37
Geosynthetics October/November 2019 - 38
Geosynthetics October/November 2019 - 39
Geosynthetics October/November 2019 - 40
Geosynthetics October/November 2019 - 41
Geosynthetics October/November 2019 - 42
Geosynthetics October/November 2019 - 43
Geosynthetics October/November 2019 - 44
Geosynthetics October/November 2019 - 45
Geosynthetics October/November 2019 - 46
Geosynthetics October/November 2019 - 47
Geosynthetics October/November 2019 - 48
Geosynthetics October/November 2019 - 49
Geosynthetics October/November 2019 - 50
Geosynthetics October/November 2019 - 51
Geosynthetics October/November 2019 - 52
Geosynthetics October/November 2019 - 53
Geosynthetics October/November 2019 - 54
Geosynthetics October/November 2019 - 55
Geosynthetics October/November 2019 - 56
Geosynthetics October/November 2019 - Cover3
Geosynthetics October/November 2019 - Cover4
Geosynthetics October/November 2019 - Blank1
Geosynthetics October/November 2019 - GeoConf20_1
Geosynthetics October/November 2019 - GeoConf20_2
Geosynthetics October/November 2019 - GeoConf20_4
Geosynthetics October/November 2019 - GeoConf20_5
Geosynthetics October/November 2019 - GeoConf20_6
Geosynthetics October/November 2019 - GeoConf20_7
Geosynthetics October/November 2019 - GeoConf20_3
Geosynthetics October/November 2019 - GeoConf20_8
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