Rut depth prediction of granular pavements using the repeated load triaxial apparatus and application in New Zealand specifications for granular materials

Equation 1, while the part of Equation 1 being subtracted (i.e. on the right of the subtraction sign) was included to ensure that deviatoric stress, q, is zero if the resulting permanent strain rate is also zero. Permanent strain rate is thus defined by Equation 1:

where, e = 2.718282; εp(rate or magn) = secant permanent strain rate or can be just permanent strain magnitude; a, b & c = constants obtained by regression analysis fitted to the measured RLT data; p = mean principal stress (MPa); and q = mean principal stress difference (MPa).