Environmental Engineering Reference
In-Depth Information
Table 2.
Tunnels primary support.
ZG1
shotcrete with fiber reinforcement (0,15 m)
and swellex bolts (4 m), in the vault where
necessary
ZG2
shotcrete with fiber reinforcement (0,15 m) and
systematic swellex bolts (4 m), in the vault
(2 m × 2 m mesh) and in the walls where
necessary
ZG3
shotcrete with fiber reinforcement (0,20 m
in walls and in the vault of the water stor-
age tunnel, 0,15 m in the other cases) and
heB160 metal ribs 1 m spaced
a)
b)
Figure
12.
a)
Finite
element
mesh
(phase
127);
b) adopted construction sequence.
Figure 11.
Tunnels lining-type for the ZG2 zone.
Figure 13.
Primary support model of the pumping
station.
zones 2 m advances were made to ZG2 and 1 m in
the ZG3 zone, keeping a distance of 20 m ahead of
the excavation.
Table 3.
Rockbolts properties.
D ext
(mm)
e
(mm)
a
(mm 2 )
ea
(×10 3 )
Q fail
(ton)
Designation
Mai R38n
37
9,5
717
150,6
50
4
nUMeRical MoDellinG oF The
PUMPinG sTaTion
s. swellex
54
3,0
480
100,9
17
Table 4.
structural elements properties.
4.1 General aspects
Due to the complex geometry and stratigraphy, 3D
and 2D analyses were conducted in order to verify
both the construction method and the chosen pri-
mary support. The 3D analyses were performed
by the Finite element Method software pack-
age PlaXis 3D TUnnel v1.2, which enabled
the modelling of the soil-structure interaction and
the complete excavation sequence. in Figure 12, the
finite element mesh used for stage 127 is shown.
The entire calculation of the structure included a
total of 142 phases, taking almost 16 hours to run
(29,000 elements mesh).
The behaviour of the rock mass was modelled
by the Mohr-coulomb model with the parameters
presented in Table 1.
Particular care was given to the 3D modelling
of the support where shell elements were used to
model the vertical walls and the roof arch; solid
elements were used to model the top walls and the
forepoles and geotextile elements for rockbolts
( Fig. 13 ).
Designation γ (kn/m 3 )
ea (×10 6 )
ei (×10 3 )
υ
BP20
24
5,80
19,3
0,2
BP15 +heB
25
5,25
11,3
0,2
25
7,44
31,3
0,2
BP20 +heB
Forepoles
-
1,60
85,3
0,2
Tables 3 and 4 present the properties of all mate-
rials used to model the primary support.
The performed calculations characterized the
expected displacements, used to define the warn-
ing levels for the structure, the stress state during
the construction sequence and the forces in the
structural elements of the support and, in particu-
lar, in the rockbolts.
4.2 Initial stress state
Because of the irregular terrain profile, it is dif-
ficult to simulate in PlaXis 3D TUnnel the
 
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