1709
Technical Committee 204 /
Comité technique 204
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
linning should be grouted. Fig.3 shows the stresses in the
grouting zone obtained by using Plaxis 8.2.
Figure 3. The calculated stresses in the grouting zone
After the grouting, the enlarged cross-section of the tunnel
was examined with Geo4 Tunnel module. The safety factor of
the calculations is 1.69 (Fig. 4).
Figure 4. The safety factor of the enlarged section using Geo4
The results of this stability calculations suggest that the
enlargement of the cross-section of the tunnel can be made only
after grouting of the area behind the present linning structure.
The head of the tunnel can be excavated gradually at its base.
After the excavation of a short span, the linning should be
closed immediately.
4.2
Interaction of different cellar systems
There is a network of cellar systems in this area. They were cut
more than a hundred year before to explore limestone. It was
not known that they are so close to each other. Later on they
were used as wine cellars and now an underground “wine city”
is planned in them. Thus the two different cellar system planed
to be connected, and the safety of them has to be investigated.
The layers of the second cellar system is showed in the table
2. Under the upper silty clay layer the porous limestone is very
thick (about 15 meters), and in it there are some thin (about 0,5
meters) bentonite layers. The main geotechnical properties of
them are also shown in table 2.
Table 2. Layers of the second cellar system
Layers
density
(kg/m3)
sig c
(MPa)
sig t
(MPa)
E
(MPa)
ν
(‐)
silty clay
1900
-
-
-
-
porous
limestone
1510
1.60
0.41
226
0.25
The silty clay layer is not important from the point of view
of the stability of the cellars because it is the thin cover soil
layer of the porous limestone. Therefore it is not analysed.
In the studied cross-section the cellars are above each other
(Fig. 5). The height of the vaults at the right side of the Fig. 5 is
5 meters, and here the thickness of the cover is enough for
developing the arch effect above the vaults as it can be see on
Fig. 5.
Figure 5. The stress distribution around the interacting cellars
calculated using Phase
2
software
This calculation is a simplification of a 3 dimensional
problem. The geometry of the cellars is not planed and there is
no exact assesment available. Thus the three dimensional
modeling of the cellar system was not possible. The safety
factor of this cross-section was n=1.5 taking into consideration
the load of a huge wine barrel with volume of 30.000 l.
This is not a final result because the 3D model is also needed
and has to be calculated, therefore for the investigation the real
safety of this cellar the exact assessment of the geometry is
needed.
4.3
Effect of surface loading on the stability of a cellar system
A building is planed above a cellar system cut into porous
limestone. The site plan of the buildig and bellow the cellars are
showed on Fig. 6. The yellow part of the figure shows the
pillars beetween the cellars. Black colour indicates the footing
of the planned house and dark grey sign the pillars which are
under the footing. As it can be seen on Fig 6. the cellars cover
about 70% of the area under the planned building.
Figure 6. Site plan of the footing and the cellars
The geological section consists of 0.3 m thick soil layer,
under it there is 0.8 m moderatly jointed porous limestone.
Under this layer the intact porous limestone is found with the
cut cellars.
In the intact porous limestone there is a 0.4 m thin bentonite
layer, which is located under the shoulder of the vaults of the
cellars. The cover of the cellar system is only 2.7 meters.
