Wednesday the 20th - Geosolve Ltd. -

For unbound granular pavements, standard presentation for hardcopy is a set of graphs showing all parameters plotted against stationing from the defined origin, as shown below.

An example of a basic Client Report can be downloaded here.


FWD Example Report


The successive graphs (commencing from the lowermost) display:

  • Pavement structure (layer thicknesses of basecourse, subbase etc) used in the model.
  • Dynamic central deflection (similar to Benkleman Beam deflection, standardised for temperature, time of loading and standard dual wheel load for 1 ESA).
  • Subgrade strain ratio, i.e. the strain at the top of the subgrade divided by the allowable strain for the material under the proposed traffic.
  • Normalised curvature (Do-D200, relative to expected values for the specified traffic, ie value less than 1 indicate premature distress is likely
  • Normalised modular ratio, values less than 1 substandard compaction if the layer thicknesses in the model are correct (same as as-built) - a very useful parameter for construction quality control
  • Subgrade modulus exponent which allows identification of likely soil type in the subgrade and its susceptibility to moisture. Low values sometimes suggest that subsurface drainage may need improvement if practicable.
  • Subgrade strain ratio. the vertical strain at the top of the subgrade divided by the allowable vertical strain, ie values much less than one indicate underdesign whereas values over 1 indicate possible premature distress
  • Adjusted Structural Number (SNP)
  • Critical layer (where strain governs first, although other layers may be marginal also)
  • Design ESA/lane (equivalent number of standard 8.2 tonne axles over the design life)
  • Subgrade resilient modulus (continuous green line) and equivalent CBR
  • Resilient moduli of pavement layers
  • Remaining life (in years) using either a strain model or HDM deterioration model
  • Required depth of cement stabilisation (if relevant)
  • Required overlay

The vertical sequence and corresponding colour coding are intended to allow rapid assimilation of the structural model and the logic of its conclusions.

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