Geosynthetics August/September 2021 - 32

Construction of roads in underground mines with 3D geocells
For mining road applications, the pavement
design is based on calculations that
involve determining the optimal dimensions
of the geocells, the dimensions of the
section and the thickness of the crushed
stone layer. The initial data includes information
about the width of the mine, its
geological structure, rock parameters,
axial loads from equipment, traffic intensity
and water inflow to the site.
The geosynthetics manufacturer
For mining road
applications, the
pavement design is
based on calculations
that involve
determining the
optimal dimensions
of the geocells, the
dimensions of the
section and the
thickness of the
crushed stone layer.
adopts the general rules for the design of
such roads for mining companies. The
calculation itself can be divided into several
stages: first, the permissible loads
on the foundation and the parameters
of the loads acting on the foundation
are identified.
Next, the height of the geocell is
selected, and the vertical and horizontal
stresses are calculated. Engineers use a
simplified stress distribution approach
to estimate additional vertical stresses at
the interface between the composite and
subgrade layers based on the two-layer
solution of Burmister (1958) for a circular
loading region.
At the last stage, the required thickness
of the composite layer is determined
through the dependence derived by Han
(2015) based on the results of testing
a dirt road with 3D geocells for cyclic
load from a moving vehicle. The tests
are interesting in that they used geocells
made not of ordinary polyethylene, but
of novel-polymeric alloy (NPA), which is
more stable under the influence of longterm
loads. Equation 1 is obtained as a
result of the tests:
(1)
Where
r is the radius of the wheel imprint.
h is the thickness of the composite layer.
Na is the number of design load
applications.
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Geosynthetics | August September 2021
Ebc is the modulus of elasticity of the
composite layer.
Esg is the modulus of elasticity of the
foundation soil.
P is the load on the wheel, equal to
1/2 of the axial load.
mbc is the utilization factor of the bearing
capacity of the composite layer.
Nc is the coefficient of bearing capacity
of the base.
cu is the resistance of the base to shear.
Since Equation 1 contains h in both
sides of the equation, the required thickness
of the composite layer can be found by iteration.
In the authors' experience, the optimal
thickness of the crushed stone layer for
road construction in underground mines is
7.9-9.8 inches (20-25 cm). If this thickness
is not obtained, engineers must recalculate
for a geocell with a different cell size.
However, there are also several procedures
required for the successful implementation
of this technology in underground
mining road applications. During
operation, it is necessary to monitor the
maintenance of the thickness of the protective
layer and the operability of the
drainage ditches. The thickness of the protective
layer above the geocell should be
at least 2 inches (5 cm). If the operators of
mine dump trucks detect a violation of the
integrity of the pavement, or holes or ruts
in the road section, they should inform the
road crew of the mine for corrective work.
It is also necessary to ensure that there is
no stagnation of water in the areas with
the reinforced geocell, as this can lead to
decompaction of crushed stone and faster
destruction of the reinforced roadbed.
Despite the apparent complexity of the
construction and operation of underground
mining roads using reinforced geocells, the
economic efficiency of such a structure
has been proven. By increasing the speed
of movement along the road sections, the
productivity of the mine increases in some
cases by 8%-12%. Fuel consumption is
reduced by 10%. The wear of mechanisms
Geosynthetics August/September 2021

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