Calculating method of design deflection in asphalt pavement based on south China area

In order to determine a more suitable pavement structure type coefficient Ab for Chinese flexible asphalt pavement structure design,the design deflection calculation method,evolution and applicability in semi-rigid pavement,flexible pavement and composite pavement was analyzed in current asphalt pavement design specifications.Based on measured deflection indicators of 8asphalt pavement expressways in China,the design deflection calculation system for flexible base asphalt pavement was studied,and the design deflection calculation formula was determined for asphalt pavement.Through calculating the thickness of flexible structure layer and strength performance of bottom layer of flexible base pavement in semi-rigid pavement structure,composite pavement structure and flexible pavement structure,the applicable condition for design deflection calculation formula of asphalt pavement was proposed.The results show that in the design deflection calculation of pavement structure,pavement structure type coefficient Ab is 1.0 for semi-rigid base pavement,2.4 for flexible base pavement and is determined using liner interpolation method for composite base pavement.In the flexible-rigid structure of asphalt pavement,the pavement is semi-rigid structure when the flexible layer thickness is less than 21cm,and is flexible structure when the flexible layer thickness is more than 35cm.The pavement is composite structure when the flexible layer thickness is between 21cm and 35cm,which is more suitable for current flexible pavement structure in China.