Geosynthetics October/November 2019 - 20

Remediation of a uranium ore residues settling basin

to the regulations in force in every country and to the end use of the site after the
remediation work.
For the technical design of a capping
system, an intensive investigation of in
situ soils is required. The following data
are requested:
* geotechnical parameters of tailings/
fill material
* stratification of the subsoil
* tailings pond size
* free water level
* live load of construction machinery

The main challenge
involved with the
capping/closure
of lagoons and
impoundments is the
weak nature of the
material being covered
and the variability
of the mechanical
characteristics with
location and depth.

20

Geosynthetics | October November 2019

The main challenge involved with the
capping/closure of lagoons and impoundments is the weak nature of the material
being covered and the variability of the
mechanical characteristics with location
and depth. Soil strength parameters are
used to perform stability analysis in order
to evaluate the load that can be submitted to the subgrade or to calculate the
strength of the geosynthetic for reinforcement to be used to increase the bearing
capacity of the subgrade.
Geosynthetic reinforcement design
Currently, there is no generally accepted
method available to design the geosynthetic reinforcement according to the
membrane-like loading effects. Edil and
Aydilek (2001) described a design procedure and Espinoza et al. (2012) presented
a case history and a more sophisticated
design method. These designs are based
on bearing capacity analyses in combination with membrane contribution of
the reinforcement. Additionally, Bishop's
method can be used for the stability
analysis in order to assess the behavior of
the soft tailings during the filling progress
at the edge of the geosynthetic.
Sometimes analysis based on wedge
or slice methods (e.g., Janbu) may be
advantageous compared to circle methods (e.g., Bishop, Krey) because of the
better considerations of the contribution

of the geotextile reinforcement. Within
the circle design methods, the reinforcement is considered as a moment that is
strongly influenced by the choice of the
midpoint as well as by the length of the
lever arm. This can lead to inadequate
consideration of the horizontal forces of
the geotextile (Zinck et al. 2007).
Regarding the stability of the system,
typical values of undrained shear strength
of the tailings-ranging approximately
between 0.07 and 0.73 psi (0.5 and 5.0
kPa) can be used and the factor of safety
has to be checked for each stage of filling. The stratification of the cover layers and their soil parameters must be
checked carefully in each stage of filling. Especially the first soil layers up to
2.0-3.3 feet (0.6-1.0 m) may be critical. At this stage the shear resistance of
the weak sludge as well as the counterpressure activated by surcharge is negligible. Therefore, ground failure is likely
to occur. To overcome this problem, the
use of light machinery with very small
live load and the installation of thin soil
layers, up to a maximum of 12 inches (30
cm), should be used.
Another aspect that has been considered in the design when geotextiles
are used in the system (both woven and
nonwoven) is their long-term filtration
behavior with respect to clogging effects.
Filter stability analyses have been carried out and, in general, geocomposites
or woven materials having apparent
opening sizes O 90 in the range from
0.08 to 0.2 mm showed good dewatering and settlement effects. Both effects
increase stability during and after the
construction period (Syllwasschy and
Wilke 2014).
Settlement estimation
Settlement due to consolidation may be
significant and it should be assessed and
consistent with the allowable deformation of the sealing system.



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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