Discussion of the Definition of Subgrade Workspace under Heavy Traffic

According to the investigation of pavement disease and the finite element mechanical calculation of pavement,the influence of subgrade stiffness on stress distribution of pavement structure and stress action depth of subgrade of expressway and grade road were analyzed.It indicates that(1) the excessive deformation of subgrade under heavy traffic is an important reason of fatigue cracking of expressway pavement;(2) The excessive deformation of subgrade(even foundation) of grade road is a key factor of early pavement cracking.Under heavy traffic,the subgrade workspace of 0～80 centimeters deep is not enough to the current pavement of expressway and grade road.The subgrade workspace depth of expressway should be 1.5 meters,which has been proved by the field tested wheel load distribution depth.The subgrade workspace depth of grade road should be 2 meters,and the deformation of natural foundation should be considered at the same time.Dispose the upper subgrade by paving a limestone soil of 60 centimeters deep can transit the stiffness between subgrade and semi-rigid subbase course,and it is also an effective method to resist heavy duty and ensure stability of pavement structure under subgrade bearing.