Pavements & traffic · Pavement design

Granular pavement thickness (thin surfacing) calculator

Total granular cover above the subgrade from CBR and design traffic: t = [219 − 211 log CBR + 58 (log CBR)²] log(DESA/120).

Standard: Austroads AGPT02 Figure 12.2 design chart equation

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Diagram for the worked example

log CBR = LOG10(5) = 0.69897
Required total thickness = (219-211*0.69897+58*0.69897^2)*LOG10(1.000e+6/120) = 391.51 mm
Subbase thickness = t − base = MAX(0,391.51-150) = 241.51 mm

Flexible pavement: mechanistic check (CIRCLY-style) — Mechanistic check of a flexible pavement under the Austroads Standard Axle. Layers are transformed by…
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Asphalt overlay from FWD deflections — Falling-weight deflectometer bowls at each test point give the surface modulus (from D0), the subgrade…
Design traffic (ESA) for pavements — Cumulative heavy vehicle axle groups and ESAs over the design period with compound growth.
Mechanistic pavement criteria (subgrade & asphalt) — Allowable repetitions from subgrade vertical strain N = (9300/µε)⁷ and asphalt fatigue N = RF[6918(0.856Vb +…
Weighted plasticity index & base suitability — Weighted plasticity index and plasticity modulus for unbound pavement material checks.

For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.