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@PHDTHESIS{Jacobs:680774,
author = {Jacobs, Felix},
othercontributors = {Ziegler, Martin and Meyer, Norbert and Heerten, Georg},
title = {{I}nteraktionsmodell zur {B}emessung von
{V}erankerungsgräben mit {G}eogittern},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2016-11974},
pages = {1 Online-Ressource (XXIV, 212 Seiten) : Illustrationen,
Diagramme},
year = {2016},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2017; Dissertation, Rheinisch-Westfälische
Technische Hochschule Aachen, 2016},
abstract = {Since the 1970’s geogrids are being used for soil
reinforcement in all fields of geotechnics as in bearing
layers under transportation ways and foundations and as in
slopes. Generally, it is the goal to build these bearing
layers stiffer and these slopes steeper than possible with a
locally available soil without additives. The reinforcement
of locally available soils additionally leads to more
economic and sustainable constructions.Surface-parallel
geogrids in slopes, as in veneer cover systems, e.g., of
landfills, take up the downward-directed part of the top
soil’s weight. Hence, the geogrid tensile force increases
along the slope from bottom to top. This high tensile force
has to be anchored within a small area at the top, which is
often carried out in anchorage trenches. The current design
of the German EBGEO (2010) regards only the ultimate and not
the serviceability limit state, and is based on some
assumptions that, based on this work and e.g. BAM (2012),
are rated to be too simplifying. Additionally, the design
does not comprise a proof of the junctions between
longitudinal and transverse tensile members of the grids,
although these are being loaded regularly. Especially in
regard to landfill constructions with their required
endurance of 100 years, a design model should be
sufficiently detailed and conservative (Koerner 2012a, p.
454). Due to these arguments, the execution of anchorage
trenches in landfill constructions in Germany is currently
restricted. Therefore, in this work a mechanically based
model for the design of anchorage trenches with geogrids,
taking into account all decisive effects, was developed to
resolve the uncertainties of the current design after EBGEO
(2010). After a comprehensive literature review, the
nonlinear influences on the pullout behavior of normal
stress, number of transverse members, soil type and soil
density were quantified with pullout tests using four
geogrid products and three soils. Basing on these findings,
a mechanically based interaction model for horizontal
anchorage was developed that combines various existing
approaches and takes into account the load transfer
mechanisms of friction on the surfaces of the longitudinal
tensile members as well as bearing in front of the
transverse tensile members.For use in an anchorage trench
with a non-horizontal but deviated geogrid alignment, this
model had to be upgraded. Therefore, approaches to take into
account deviation effects and different possible failure
mechanisms were combined with the interaction model for
horizontal anchorage. With its mechanically based approaches
for the interaction, the deviation effects and the failure
mechanisms and due to its successful validation, this model
could be used for modeling the resistance mobilization of
geogrids in anchorage trenches.With the developed anchorage
trench model, the design approach of EBGEO (2010) was
checked with characteristic calculations within a parametric
study. The comparison showed that the deviations along the
geogrid led to an increase in resistance and in stiffness of
anchorage trenches. In almost all cases, the failure
mechanism sliding with only resistance forces at the bottom
side of the geogrid was decisive, which is not considered in
the current design practice. In total, the design of EBGEO
(2010), even when considering the mechanism sliding, tended
to unsafe results for anchorage trenches with lower
stiffness. In order to still be able to safely design with
the approach of EBGEO (2010), the resulting resistance has
to be reduced by a model factor of γMF,EBGEO = 1.67. Only
for anchorage trenches with higher stiffness of kR ≥ 1820
kPa, EBGEO design leads to safe results without the model
factor. However, in almost all cases, design with EBGEO
(2010) and the model factor is not economic.For safe and, at
the same time, economic design of geogrid anchorage
trenches, the model was incorporated into a design concept,
which was based on the existing design concept for anchorage
trenches. For the known proofs of the ultimate limit state,
the model gives the design resistance, while the tensile
force resulting at the top of the slope, as design action,
can still be determined according to EBGEO (2010).
Additionally, the design model comprises two proofs against
failure of the junctions between longitudinal and transverse
tensile members (shear resistance and maximum allowable
displacement), for which the model calculates the design
actions. For the first time, with the developed model a
design of the serviceability limit state is possible. For
these, the model calculates the geogrid displacement at the
top of the slope for the regarded load case as design
action.To be able to use the design model for design of the
ultimate limit state not only with the written code and the
software Matlab, but also with a simple spreadsheet
calculation, it was simplified by a coarse discretization of
the geogrid into only three sections. The resulting reduced
accuracy of the simplified design model is taken into
account using a stiffness-dependent model factor that was
defined.Thereby, a safe design of the ultimate limit state
is possible with the simplified design model as well as the
detailed design model, in contrast to design with EBGEO
(2010), including a proof of the geogrid junctions. By
introduction of a model factor for the approach of EBGEO
(2010), design using EBGEO (2010) is still possible.
However, this design is less economic than using the
presented new design models. Additionally, with the detailed
design model, for the first time, a design of the
serviceability limit state is possible.},
cin = {314310},
ddc = {624},
cid = {$I:(DE-82)314310_20140620$},
typ = {PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:82-rwth-2016-119740},
url = {https://publications.rwth-aachen.de/record/680774},
}
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