沥青路面结构层模量反演最佳特征点的确定

Determination of optimal identity points for backcalculating the structural layer moduli of asphalt pavement

基于落锤式弯沉仪(falling weight deflectometer,FWD)检测数据的路面结构层反演模量逐渐成为评价路面结构承载力的重要指标.在结构层模量反演方法中,弯沉盆规律法能够得到反演唯一解,工程应用性强.但现阶段弯沉盆规律法中,用于反演路面基层模量、面层模量的特征点位置的确定均基于理论分析,未得到实测弯沉盆数据的验证.因此,为进一步确定特征点的最佳位置,我们对不同路面结构不同层位的弯沉盆实测数据进行了研究.首先,利用交通运输部RIOHTRACK足尺环道试验的弯沉数据,分析了不同特征点位置对基层反演模量的影响;其次,以基于不同层位弯沉数据反演出的基层模量是否具有一致性为原则,确定了特征点的最佳位置;最后,利用独立弯沉数据对其准确性进行了验证.结果表明,对于实测弯沉盆数据,特征点选取位置对逐层反演基层模量一致性具有显著影响;对于2层结构体系,特征点位置选取为距离荷载中心点30 cm处,对于3层结构体系,特征点位置选取为荷载中心点和距离荷载中心点60 cm处时,逐层反演的基层模量一致性最好.

The backcalculated structural moduli of asphalt pavement using the falling weight deflectomer(FWD)deflection basin data has been increasingly used for evaluating the bearing capacity of non-destructive pavement structures.The current backcalculation methods can be divided into 2 categories,i.e.,one algorithm based on deflection basin matching and the other algorithm based on deflection basin law.The principle of the former algorithm is to find a set of structural layer moduli so that the theoretical deflection and the measured deflection have the highest matching degree,and the later algorithm uses some regular and special points according to the law of the deflection basin affected by the structural parameters to backcalculate layer moduli.Research has shown that the former algorithm has a problem in whether there is a unique solution and the inversion efficiency.While the basin law algorithm is able to generate a unique solution,which makes it more suitable for engineering applications.However,the identity points used in the current basin law algorithm were determined based on the theoretically calculated FWD deflection basins.The accuracy of these identity points needs to be further validated using the field measured FWD data.Therefore,in order to determine the optimal positions of the identity points accurately,this paper analyzed the law of backcalculated moduli of pavement structure based on the measured layer-by-layer deflection basins of different pavement structures.First of all,the influence of different identity points on the backcalculated base moduli was investigated using the deflection data from the full scale testing track of RIOH.Then,the optimal positions of the identity points were determined,based on the principle of the consistency of the backcalculated base modulus using the measured deflection basin data,which means that the backcalculated modulus values of base layers should be almost the same.Finally,the accuracy of the optimization identity point method was verified by independent deflection data.The results indicated that the positions of identity points had significant effects on the backcalculated moduli for the base layer.When the position of the base identity point was unchanged,the variability of the backcalculated base modulus tended to decrease first and then increase as the position of the surface identity points as far away from the load center.And according to the deflection data from the full scale testing track of RIOH,we concluded that,for the two-layers asphalt pavement,when the optimal position of the identity point was 30 cm far from the load center while the positions for three-layers asphalt pavement were 0 and 60 cm away from the load center,the backcalculated base modulus based on layer-by-layer deflection data had the best consistency.Based on the inversion analysis of the independent deflection data,the accuracy of the position of the identity points determined in this study was verified.The verification results showed that the modified method proposed in this study could be used to accurately backcalculate the modulus of the pavement structure layer in other engineering,and the method was highly applicable.At the same time,the method proposed in this study had stable results and low variability,which can meet the needs of engineering.