Paper by Arvo Tinni on the Role of SMZ & LMC in pavement design from Sydney Forum 31 March 2008
The paper draws attention to the major differences in design methodology of flexible and rigid pavement designs. For concrete pavements, the design is based on the Equivalent Strength (CBR) of 1000 mm of subgrade. This includes the Selected Material Zone (SMZ) and is calculated using the widely accepted Japanese Public Works formula for equivalency.
The role of the SMZ is to provide a stable support platform of uniform bearing capacity. Its quality is specified to reduce the susceptibility of erosion. As a further insurance, the top 150 mm is lime modified if the material has a CBR <30%.