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case history
Reinforcement of a Highway Embankment over Peat Layers
PRODUCT   TENAX LBO 330 SAMP bi-oriented geogrids
LOCATION   Highway M7, Balaton Lake, Hungary, 2004
DESIGNER   Technical University of Budapest, Department of Geotechnics
CONTRACTOR   Vegyépszer Rt.


Problem
The highway M7 from Budapest to Croatia, in the western region of Lake Balaton had to be constructed over thick peat layers with very low CBR values.
Due to the short construction program and the thickness of the peat layers, soil substitution was not an option. 14.5 km of the highway was to be constructed in this area, the peat layers were typically 3 m – 4 m deep. Due to the very low bearing capacity it was difficult to walk on the proposed route and impossible to access the area with trucks.
The most critical part was between km 165+800 to km 167+150, in this section the peat layers were 6 m - 8 m deep.
To carry the new highway a 9 m – 11 m embankment was to be constructed. At the base of the foundation layer a minimum bearing capacity of 25 MPa was required.

  

High water table of the peat layers
High water table of the peat layers

TENAX LBO 330 SAMP and nonwoven geotextile
TENAX LBO 330 SAMP and nonwoven geotextile

 
draw
 

SOLUTIONS
Following laboratory tests of the subsoil a design was carried out by the Technical University of Budapest. The most economical solution was to incorporate a 30 x 30 kN/m TENAX LBO 330 SAMP rigid integral geogrid within the permanent works. A nonwoven geotextile was also specified to act as a filter fabric.

Construction and results at the most critical sections:

Km 165+800 to 166+350:
  - Nonwoven
  - 1 layer TENAX LBO 330 SAMP
  - 50 cm crushed Dolomit (0/120 mm):
E2=34 - 49 MPa
   
   
Km 166+350 – 167+150:
  - Nonwoven
  - 1 layer TENAX LBO 330 SAMP
  - 50 cm crushed Dolomit (0/120 mm):
E2=53 - 68 MPa

The TENAX geogrids were installed using the wraparound technique during the placement and compaction of the Dolomit layers. In both of the sections the measured improvements in the bearing capacity have exceeded the design requirements.


conclusions
The goals of a reinforced granular layer below an embankment that has to be built on soils with a very low bearing capacity are these:

  1. To reduce settlements
  2. To improve the load distribution
  3. To prevent rotational failure at the toe of the slope.

The use of TENAX LBO 330 SAMP integral geogrids substantially increased the bearing capacity and settlement was reduced.
It was possible to access the area with heavy trucks during the construction phase and the embankment could be built with extremely poor underlying subsoil conditions.

  

Installation of the Dolomit fill material
Installation of the Dolomit fill material

Excess geogrid and nonwoven ready for back wrapping
Excess geogrid and nonwoven ready for back wrapping

Back wrapping of the 2 geosynthetic layers
Back wrapping of the 2 geosynthetic layers

     
TENAX LBO SAMP
TENAX LBO SAMP geogrids are specifically designed for the stabilization and the reinforcement of soil. TENAX LBO SAMP geogrids are manufactured from polypropylene (PP), produced by a patented extrusion method and successively biaxially drawn to increase their tensile characteristics.
 
TENAX LBO SAMP geogrids have an elevated tensile modulus and optimal construction damage resistance during installation. Interlocking of the aggregate within the apertures allows for the effective confinement and reinforcement of the soil.
 
TECHNICAL CHARACTERISTICS
TENAX LBO 330 SAMP
    MD TD
Aperture mm 40 27
Strength at 2% strain kN/m 10.5 10.5
Strength at 5% strain kN/m 21.0 21.0
Peak tensile strength kN/m 30.0 30.0
Yield point elongation % 11.0 10.0

MD: machine direction (longitudinal to the roll)
TD: transverse direction (across roll width)
           
TENAX LBO SAMP geogrid   TENAX geogrid: Interlocking of the aggregate within the aperture
  
TENAX LBO
SAMP geogrid 		  Interlocking of the aggregate within the apertures  
 
 
PRODUCTS
TENAX LBO SAMP
 
APPLICATIONS
Paved and unpaved roads
Foundations of roadbeds, embankments and earth dams
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