考虑沥青层表面细观构造的探地雷达空隙率检测研究

Research on Asphalt Pavement Air Voids Content Estimation Utilizing GPR Considering the Surface Microscopic Structure

沥青路面空隙率对道路路用性能及服务寿命具有决定性作用,为实现沥青层空隙率精确检测,考虑表面细观构造影响提出一种基于探地雷达的测量方法。首先,通过时域有限差分(FDTD)仿真软件,建立多空隙薄层-均匀空隙层数值模型,量化模拟了表面细观构造对空隙率检测精度的影响。其次,基于全波形反演理论提出一种检测算法,对反射波进行分解并计算均匀空隙层介电常数。最后,通过FDTD数值模型及实验室实测对该算法有效性进行验证。结果表明:均匀层空隙率检测值随薄层空隙率增加先变大后减小,沥青层表面细观构造对空隙率检测精度具有较大影响。反射波经全波形反演法分解重构后与原波形具有较高吻合度,可精确计算均匀层介电常数。相较于传统金属板反射法,全波形反演法FDTD模型空隙率检测误差降低了24.0%,实验室检测误差降低了6.6%,验证了该方法的可行性。

Air voids content is the most important factor for asphalt pavement which have close relationship with road performance and durability.In order to predict the air voids content of asphalt layer with high accuracy,a method was proposed considering the surface microscopic structure based on ground penetrating radar(GPR).Firstly,the numerical model of porous thin layer-uniform voids layer was established based on the finite-difference time-domain(FDTD)software,and the influence of surface microscopic structure on the prediction accuracy of air voids content was quantitatively simulated.After that,the algorithm was developed to decompose the electromagnetic wave reflected from the surface and calculate the dielectric constant of the uniform voids layer based on the full waveform inversion theory.Finally,the effectivity of the algorithm was verified through FDTD numerical models and laboratory measurements.The results show that:the air voids content of the uniform layer first increased and then decreased with the increase of the air voids content of the porous thin layer,and the surface microscopic structure of the asphalt layer influenced the accuracy of air voids content prediction significantly.The reflection wave decomposed and reconstructed by the full waveform inversion method was in good correspondence with the original waveform,and the dielectric constant of the uniform layer can be calculated accurately.Compared to the traditional metal reflection method,the average error of air voids content estimation obtained from the FDTD models and laboratory measurements using the proposed method was reduced by 24.0%and 6.6%,respectively,which verified the feasibility of this method.