Environmental Engineering Reference
In-Depth Information
• The pyroclastics coeicient k
0
affects greatly the
calculation results. The validity of the assumed
value (1.0) is confirmed by the calculation results
of the relation between the crown-wall and wall-
wall convergences, similar to the measured one.
• The coninement loss, λ, in the diferent con-
struction stages has an important effect on the
deformation values at each stage, except in the
last one (excavation of ditches). in this analysis,
the adopted values match the convergences
measurements.
• The most determining parameters of the
calculation are the parameters of the pyroclastics
(c
M
, Φ
M
, ν, e, µ), especially c
M
, Φ
M
and e. it is
obvious that by changing the adopted values of
c
M
and Φ
M
, a different value of e from indicated
in section 4.3.2, concordant with the measured
convergences, would have been obtained.
The adopted values of c
M
, Φ
M
and e of the
pyroclastics are realistic, in the authors´ opinion,
as it's explained below, but other combinations
of parameters can be equally concordant with
the measurements.
JOB TITLE : T3-1+213: Excavación Zanjas
(*10^1)
FLAC (Version 4.00)
LEGEND
1-Jul-03 19:01
step 70103
0.000E+00 <x< 1.500E+01
-4.000E+00 <y< 1.100E+01
X- displacement contours
-6.00E-02
-5.25E-02
-4.50E-02
-3.75E-02
-3.00E-02
-2.25E-02
-1.50E-02
-7.50E-03
0.00E+00
Contour interval= 7.50E-03
Boundary plot
0
0.900
0.700
0.500
0.300
0.100
-0.100
2E
0
Beam plot
-0.300
Itasca Consulting Group, Inc.
Minneapolis, Minnesota USA
0.100
0.300
0.500
0.700
0.900
1.100
1.300
(*10^1)
Figure 11. calculated horizontal displacements after
phase 6, excavation of the ditches.
JOB TITLE : T3-1+213: Excavación Zanjas
FLAC (Version 4.00)
LEGEND
1-Jul-03 19:01
step 70103
0.000E+00 <x< 8.000E+00
-1.000E+00 <y< 7.000E+00
Displacement vectors
Scaled to Ma x = 6.400E-02
Max Vector = 4.074E-02
0
6.500
5.500
4.500
3.500
2E -1
Boundary plot
0
Beam plot
2.500
2E
0
1.500
4.4.5
Other possible values of c
M
, Φ
M
and E
of the pyroclastics
as explained in section 4.3.2., the adopted values
of c
M
and Φ
M
are high, in the range of the high-
est expectable values for this type of material. an
additional check with lower values of c
M
and Φ
M
,
closer to average, has been made. if adopted values
in section 4.3.2. were β
i
= 1000 kPa, ζ
i
= 0.25 and
Gsi = 65, the results would be:
0.500
-0.500
Itasca Consulting Group, Inc.
Minneapolis, Minnesota USA
0.500
1.500
2.500
3.500
4.500
5.500
6.500
7.500
Figure 12. calculated displacement vectors after phase 6,
excavation of the ditches.
JOB TITLE : T3-1+213: Excavación Zanjas
(*10^1)
FLAC (Version 4.00)
LEGEND
1-Jul-03 19:01
step 70103
0.000E+00 <x< 1.500E+01
-4.000E+00 <y< 1.100E+01
Boundary plot
0
c
M
= 0.17 MPa Φ
M
= 19.7°
With these input data, the modulus of defor-
mation concordant with the measurements of
convergences is about 9,000-10,000 MPa. This is
a very high value, clearly unreal. it is similar to
what could be expected in good quality basaltic
lava flows, even though basaltic lava flows and the
pyroclastics deformability are clearly different.
0.900
0.700
0.500
2E 0
Beam plot
Exaggerated Boundary Disp.
Magnification = 5.000E+00
Max Disp = 4.074E-02
Plasticity Indicator
* at yield in shear or vol.
X elastic, at yield in past
o at yield in tension
0.300
0.100
-0.100
-0.300
Itasca Consulting Group, Inc.
Mi nneapolis, Mi nnesota USA
0.100
0.300
0.500
0.700
0.900
1.100
1.300
(*10^1)
Table 1.
horizontal convergences.
Figure 13. calculated yielding ground after phase 6,
excavation of the ditches.
secTion 1+213
convergences (mm)
in addition, this analysis shows a very large
plastic zone around the tunnel, with a thickness of
2 tunnel diameters, which does not seem realistic
either.
Therefore, it is reasonable to think that, although
there are a number of combinations for c
M
, Φ
M
and
e, compatibles with the measurements, the real
ground values should not be very different from the
Phase
calculation
Measured
1: excavation
5
-
2: Plain shotcrete layer
18
-
3: 1st reinforcement layer
9
10
4: Removal of the
repiés
19
17
5: 2nd reinforcement layer
0
0
6: excavation of ditches
28
22
