High strength reinforcement can be used over piles. In supporting the fill between the piles, the reinforcement acts as a tension membrane transferring the vertical load of the embankment directly onto the piles. This enables the size of the pile caps to be reduced substantially. Because the reinforcement counteracts the horizontal thrust at the side of the embankment, no raking piles are required. The maximum allowable extension in the geosynthetic reinforcement acting across the width of the embankment should be 6% with a maximum allowable creep extension of typically 1%. The same limits on extension apply in the direction along the length of the embankment.
The determination of the overall working tensile properties of the reinforcement require for design can be divided into two parts. The first involves the determination of the working tensile properties required to transfer the vertical loading of the embankment fill (and surcharge) onto the piles. The second part involves the determination of the working tensile properties required to resist the horizontal outward thrust of the embankment. These required tensile properties act across the width of the embankment only.
Once the appropriate working tensile properties have been established for each part of the design, the required overall working tensile properties can be determined. The required overall working tensile loads are the sum of the two parts of the design in both the longitudinal and cross direction of the embankment. The required overall tensile extensions are the minimum determined from each of the two parts of the design. In Italy, as well as in Europe, the design over piles typically follows BS 8006-1 or EBGEO.
