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| case history |
| 17 m high wall with an inclination
of 80° and green facing, Iserlohn, Germany |
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| PRODUCT |
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TENAX TT 701 SAMP
TENAX LBO 220 SAMP |
| LOCATION |
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Iserlohn, Germany |
| OWNER |
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Lobbe Holding GmbH
& Co |
| PROJECT |
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Herold & Köhler,
Weimar |
| CONTRACTOR |
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Lobbe und Hoy |
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problem
In 1997 Lobbe Holding GmbH & Co. planned a new head
office building in Iserlohn. The construction site is characterised
by terrain which slopes strongly towards the North. The
construction site is bounded on the West by a railway line
and on the North by the A46 motorway.
The difference in
elevation between the North and South boundaries is 17 m.
The aim of the construction was to protect the new building
from the noise of the A46 and to allow a parking area to
be placed in front of the building. A flexible and steep
wall system which could be adapted easily to the form of
the area and to the environment (green face) was requested
by the owner and the authorities.
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Aerial view of completed project
Surface of the construction site
in original condition |
solution
Several different solutions were discussed, designs and calculations
were carried out and the most economic solution was to use the locally
available recycled material with a pH value of 11.5 and integral
TENAX geogrids. The recycled material needed a high chemically resistant
reinforcement with a low factor of safety against installation damage.
The design according DIN V 1054.100 (partial safety concept) required
for the 17 m high wall with an inclination of 80° the following
layout:
- TENAX TT 701 SAMP a mono-oriented, integral HDPE geogrid with
a vertical spacing of 0,45 m in the lower part and 0,90 m in
the upper part as the primary reinforcement;
- TENAX LBO 220 SAMP a bi-oriented, integral PP geogrid as secondary
reinforcement.
The inclination system was made with formwork beams,
which were anchored with steel elements, shaped like a horseshoe,
in every third layer of the construction. Behind the steel formwork
a vegetation and erosion control mat was placed and additionally
supported with 30 cm topsoil and special seeds for a quick vegetation.
Both the primary and secondary reinforcement was installed only
in the horizontal plane without any back wrapping. To avoid desiccation
at the 80° steep wall a superficial water irrigation system
was put in place. |
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Safety railing and inclination guides |
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West surface during construction, half complete
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West side, completed |
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| conclusions |
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The construction of geosynthetic reinforced
earth embankments with an inclination of 80° and green facing
is fundamentally possible and economic.
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When the inclination is between 60° and
80°, special steps have to be taken so that the green facing
is durable. A sensible solution is a division between primary
and secondary green facing. The green facing must be carefully
planned.
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In order to take into account the climatic
conditions specific to the natural environment in this place
with respect to the selection of plants and design of the green
facing, the advice of a biological engineer is always recommended
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Analogous to conventional concrete retaining
constructions, geosynthetic earth constructions must be carefully
designed and planned. Because of a lack of long-term experience
with this method at this time, and the resulting difficulty
in predicting the deformation of systems of this sort, a program
of deformation measurements is to be recommended.
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From an economical point of view, it is necessary
to design with the product-specific reduction factors taking
into account the intended fill soil.
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The calculation of this building was worked
out in accordance with DIN V 1054-100 (partial safety concept).
A comparative calculation in accordance with the summation security
concept provided the same results.
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Settlements after one year have been lower
than the calculated ones. The vertical settlement after one
year was between 20 and 30 mm and the horizontal displacement
was not measurable.
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geo@tenax.net