Geotechnical News • June 2012
41
WASTE GEOTECHNICS
around frameworks that define the
state of a given soil using void ratio
and effective confining stress only;
however, there is a need to account for
other effects such as particle fabric,
ageing, and field loading modes,
which are known to be significant, but
are currently often disregarded due to
lack of knowledge on the subject.
In addition to the high quality charac-
terization work required to understand
the soil, tailings, and groundwater
conditions in the field, there is a strong
need to advance our understanding of
the mechanical response of tailings
themselves under seismic loading.
Parameters such as strength and
deformation moduli, compressibility,
and hydraulic conductivity derived
from laboratory testing provide
essential input for numerical modeling
and support and confirm field-based
approaches. For example, direct
simple shear testing is considered
suitable as a laboratory element test
to determine cyclic shear resistance
since the method is able to simu-
late the predominant mode of field
loading during earthquake shaking.
Another important consideration in
seismic evaluation of tailings deposits
is the validity of numerical models
used for the prediction of earthquake-
induced ground displacements. Since
high-quality data records from field
case histories are rare, such valida-
tions often become a difficult task.
Physical modeling of well-defined
boundary value problems using
methods such as shaking table and
geotechnical centrifuge testing may
thus play a key role in generating data
for meaningful validation of numeri-
cal models. Work is also needed to
investigate alternative disposal strate-
gies to control or limit the risk due to
liquefaction of tailings.
Mine wastes management also raises
many issues related to environmental
geotechnique. In this regard, signifi-
cant progress has been made on pre-
diction and characterization techniques
to assess the hydro-geochemical
behavior of tailings and waste rocks
that contain reactive minerals. This
aspect nonetheless remains a chal-
lenge, particularly for materials with
a low acid potential where static tests
are insufficient and interpretation of
commonly used kinetic tests results is
uncertain in predicting the long-term
water quality. Control technologies
have also evolved markedly over the
last two decades or so. For instance,
many laboratory, field, and numerical
studies conducted on engineered cover
systems, for both dry and wet cli-
mates, have shown how such systems
can be used effectively to limit the
flow of water or oxygen to the reactive
wastes underneath and thus prevent
Laboratory testing plays a vital role for the characterization of material behavior for mining geotechnique, including the
response of tailings to cyclic loading as illustrated above.
