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Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
conservative values for stress, as t
4
is approx. at 2880 h and t
5
at
6500 h.
6 SUMMARY
5.3
Main findings
Up to the date of printing, the construction is approximately one
year in service. Data recording is available continuously during
installation and in sequences during the service period. Within
the service period, also 24h-measurements have been done to
get an impression of temperature changes within the wall.
Figure 6 gives the strain recording for the total time, indicating
a very low level of strain of less than 1%, as it has to be
expected. Nevertheless, only the three layers on the bottom get a
significant loading. Two layers of geogrids on the top are up to
now not taking any load. As these layers are mainly designed
for a top-load of the construction not performed yet, the results
fit with the expectations.
Full scale laboratory tests have been performed for a full height
panel wall, combined with a geogrid-reinforced soil structure.
Tests are performed at loads up to 450 kPa according to bridge
abutments as well as at dynamic loadings.
A comparable setup of a full scale panel wall has also been
tested in situ. Monitoring of the reinforced wall allows for
satisfactory back-analysis of the constructions steps.
The measured stress conditions fit with the expected low
stress approach for the combined structure, given by FE-
analysis. The findings combine the current results of
international research and updated design approaches (EBGEO)
also for full height panel walls. They allow for the consideration
of a reduced earth pressure distribution in design as well as for
simplified construction.
Removing the prop (t
1
to t
2
) has been expected to increase
the strain in the upper layers of the geogrids. Actually, this
could not been found on site. The absolute values of strain (and
therefore stress) at each layer remained stable.
Due to limitations, the setup and results cannot be transferred
to all combinations of reinforcement, soil and panel-systems,
but allow for further analysis by FE calculations.
For the sum of horizontal loads, compiled for the
representative time t
0
to t
5
, measured forces as well as forces
from FE-calculation and analytical approach by classical earth
pressure theory can be compared. Friction at the toe of the wall,
forces on the temporary prop as well as forces at the geogrids,
measured right behind the wall, have to be compiled.
Figure 7. Comparison of measured lateral stress in situ, prediction by
FE-analysis and prediction by classical earth pressure theory
0
10
20
30
40
50
60
70
t0
t1
t2
t4
t5
xx (horizontal)
[kN/m]
In‐Situ
Plaxis
Eah, analytical (32,5°)
7
REFERENCES
EBGEO - Recommendations for Design and Analysis of Earth
Structures using Geosynthetic Reinforcements. 2nd Edition.
Published by German Geotechnical Society (DGGT). Ernst &
Sohn, Berlin, 2011.
Figure 6. Entire strain recordings of the geogrids (DMS: strain gauge
applied to geogrid).
DIN EN 14475, 2006-04: Execution of special geotechnical works -
Reinforced fill.
0,0
1,0
2,0
3,0
4,0
5,0
6,0
7,0
8,0
26 February 2011
9 July 2011
19 November 2011
1 April 2012
Strain [‰]
Time
DMS +4,0 m
DMS +3,5 m
DMS +2,5 m
DMS +1,5 m
DMS +0,5 m
BS 8006-1, 2010-10: Code of practice for strengthened/reinforced soils
and other fills.
For time t
0
to t
4
, the results gained by PLAXIS come quite
close to the results gained from measurements in situ, Figure 7.
Taking the rotation backwards due to settlements into
consideration (time t
5
), PLAXIS gives a significant increase in
stress, not be found on site.
Pachomow, D., Vollmert, L. & Herold, A. (2007): „Der Ansatz des
horizontalen Erddrucks auf die Front von KBE-Systemen“.
Tagungsband zur 10. FS-KGEO 2007.
Ruiken, A., Ziegler, M., Vollmert, L. & Duzic, I. (2010): “Recent
findings about the confining effects of geogrids from large scale
laboratory testing”. 9th International Conference on Geosynthetics,
Brazil, 2010.
In comparison to the measurements, results given by
classical earth pressure have not been found to represent the
reality for this combination of reinforcement and facing, neither
the laboratory one nor the in-situ one. The difference is at least
between 30% and 40% and therefore in line with the current
status of research on reinforced soils. Compared to the design
situation according to EBGEO, a reduction of lateral stress for
the load case “unit weight of structure” and therefore a cor-
rection factor
g
≥ 0.7 would be acceptable from the author’s
point of view.
Bussert, F. (2006): „Verformungsverhalten geokunststoffbewehrter
Erdstützkörper
–
Einflussgrößen
zur
Ermittlung
der
Gebrauchstauglichkeit“. Dissertation. TU Clausthal, Schriftenreihe
des Instituts für Geotechnik und Markscheidewesen, Heft 13/2006.
Pachomow, D. & Herold, A. (2009): „Zum Last-Verformungsverhalten
von KBE-Konstruktionen im Frontbereich“. Vortrag zum
VI. Geokunststoff-Kolloquium in Bad Wildungen der NAUE
GmbH & Co. KG, Espelkamp.
