How are the integrated climatic model as discussed in Enhanced Integrated Climatic Model Version 2.0, and the thornthwaite moisture index (TMI) used to calculate erosion, suction, and frost heaving in Pavement Mechanistic-Empirical Design?

Specifically interested in how precipitation affects pavement performance within Pavement Mechanistic Empirical Design (PMED) software.


1 Answer 1


Erosion, frost heaving, and suction are all ultimately caused by precipitation on the pavement. Precipitation is used in the following models:

  • The Enhanced Integrated Climatic Model (EICM) uses precipitation to calculate the monthly Thornwaite Moisture Index (TMI).

  • The TMI is used in calculating the equilibrium suction for the base and subgrade layers. The suction values are used to estimate water content within each sublayer which impacts the resilient modulus values.

  • The flexible roughness model uses the mean annual rainfall to calculate the frost and swell potential for the site factor parameter in the model.

  • The continuously reinforced concrete pavement (CRCP) model uses annual rainfall for the erosion calculation

The Pavement ME Design software does not currently model precipitation infiltration into the pavement system from the surface. It assumes that the pavement system has adequate drainage.


  1. Mechanistic Empirical Pavement Design Guide – A Manual of Practice

  2. NCHRP 1-37A Documentation – Main document and double letter appendices

  3. NCHRP Report 602 – Calibration and Validation of the Enhanced Integrated Climatic Model for Pavement Design


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