Establishment of the depth of subgrade working area in asphalt pavement

Based on the theory of multi-layer elastic system,load stress of different subgrade depth positions in various kinds of actual asphalt pavements are conducted through software of BISAR.Statistic analysis is done according to the results of calculations.Furthermore,the recommendation of depth of subgrade working area is suggested as the value of 1.4 m for expressway,first-class highway and secondary road which possesses excellent pavement structure or smaller proportion of heavy trucks,or as the value of 1.8 m for secondary road or lower grade roads mainly made by freight vehicles which possess larger proportion of heavy trucks.The above recommended values of depth of subgrade working area can be applied for selecting as the depth and measures of subgrade or base.