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| case history |
| Stabilization of a road embankment
on very soft clay soil, for the construction of a new Expressway
in Bangkok, Thailand |
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| PRODUCT |
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TENAX LBO 302 SAMP bi-oriented
geogrids |
| LOCATION |
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Bangkok, Thailand, 1991 |
| OWNER |
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Expressway and Rapid transit
Authority of Thailand
Bangkok Expressway Co. Ltd |
| PROJECT |
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Freeman Fox Intercon Consultant
Ltd. Bangkok |
| CONTRACTOR |
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Kumagai Gumi Co. Ltd, Japan
BBCE Joint Venture: (Bilfinger +
Berger Bauaktiengesellschaft, Germany
Ch. Karnchang Co. Ltd, Thailand
Expert transport Co. Ltd, Thailand |
Problem
The new Bangkok Expressway was crossing a marshy area with
a very soft soil consisting of normal consolidated Bangkok
clays, 20 m deep. The site investigations showed that the
bearing capacity of the foundation soil was too low to support
a "traditional" highway embankment.
The first idea was therefore to widen the embankment base
with large berms, in order to distribute the load on a wider
area, thus involving deeper soil layers and therefore increasing
the global bearing capacity. It appeared fundamental to provide
the enlarged base with a sufficient stiffness, in order to
decrease both the vertical stresses and the differential settlements.
In addition to the above considerations, a high stiffness
was required for the initial construction phase to allow the
heavy plant to operate on site without sinking into the extremely
soft soil that was often waterlogged.
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Road section on marshy soil
(unconsolidated soft clay)
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solution
The design required four horizontal layers of biaxially oriented
geogrids for stabilizing this embankment. The geogrids were installed
at 300 mm vertical spacing. The design engineers, considering the
fundamental structural function performed by the geogrids, issued
very stringent specifications for the reinforcement. The geogrid
manufacturer was required to provide evidence that a professional
quality control procedure would be implemented during the production
process and that a certificate of conformity for the specific product
would be issued for this project, including:
- Testing certificates by independent laboratories;
- Tensile creep test results, adequate to determine the design
tensile strength of the geogrids for a design of 1 year under
constant load (1 year was the anticipated time for the consolidation
of the clay soil under the embankment);
- Tensile secant modulus at 2% and 5% elongation;
- Proof of UV stabilization.
The geogrids chosen by the Contractor, with the
full approval of the design engineers, were TENAX LBO 302 SAMP bi-oriented
geogrids. The TENAX engineers were able to produce a proper answer
to all the project requirements. In addition, the whole production
lot for the Bangkok Expressway (about 150.000 m² of geogrids)
were tested and certified by SGS (Societé Générale
de Surveillance), a specialised international QC/QA firm. |
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conclusions
TENAX geogrids in this project, as well as in many others, have
proven to be a product with the highest technical characteristics
and with guaranteed properties. TENAX LBO 302 SAMP passed severe
controls before being utilized as a structural element for the stabilization
of an embankment on very soft soil.
The ease of installation of
TENAX geogrids allowed the Contractor to maintain high installation
rates and allowed to use an innovative technology for stabilizing
the embankment, thus obtaining consistent savings over traditional
solutions.
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geo@tenax.net