damaged material in plaxis 3d

Hi Eslam,

You can think of a damaged or fatigued pavement as a material with decreased stiffness modulus.
Depending on the damage development stage (i.e. Stage I: cracking at the surface and internal defects of the specimen, Stage II: release of high-density energy at the internal defects of the specimen due to the cracking, Stage III: severe damage and rapidly increasing fatigue damage rate until failure), you may have a different variation trend of the stiffness modulus.
To evaluate the decreased stiffness modulus, you should run a laboratory test (e.g., semi-circular bending test) or use empirical relationships that relate the elastic stiffness of the fatigue beam to the crack length of the pavement.