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沥青混凝土是典型的多相离散随机介质,为了研究沥青混凝土各结构层的空隙率与探地雷达波场特征之间的关系,本文基于沥青混凝土各结构层对应的多相离散随机介质模型参数,应用量化约束多相离散随机介质模型建模算法,构建了不同空隙率的多相离散随机介质三维模型,并基于商用屏蔽型蝶形天线三维模型数值模拟了探地雷达波在其中的传播特征,研究了多相离散随机介质空隙率与探地雷达波场特征之间的关系.研究结果表明:在半无限空间中,多相离散随机介质的空隙率越大,探地雷达波散射越强烈、地面直达波正相位振幅越强;对于上、中、下面层厚度分别为4 cm、6 cm、8 cm的层状多相离散随机介质,地面直达波正相位振幅强度主要取决于上面层多相离散随机介质空隙率大小,受中面层多相离散随机介质空隙率的影响较小;地面直达波负相位的振幅强度主要与中面层多相离散随机介质空隙率大小相关,其振幅强度随空隙率的增大而增强,且地面直达波正、负相位振幅强度与下面层多相离散随机介质空隙率无关;下面层多相离散随机介质的空隙率与下层介质分界面之间的反射波振幅强度成正比例关系.研究结果为探地雷达定量估算沥青混凝土各结构层的空隙率提供了理论依据.
Asphalt concrete is a typical heterogeneous discrete random medium. In order to study the relationship between the void fraction of asphalt concrete structure layers and the characteristics of the GPR wavefields, based on the parameters of the multiphase discrete random medium model corresponding to each structural layer of asphalt concrete, The multi-phase discrete stochastic media model modeling algorithm with quantitative constraints was used to construct a three-dimensional model of multi-phase discrete random media with different void ratios. The propagation characteristics of GPR waves were simulated based on the three-dimensional model of commercial shielded butterfly antenna. The relationship between the porosity of multi-phase discrete random media and the characteristics of the GPR wavefield is studied. The results show that the larger the porosity of the multiphase discrete random medium in the semi-infinite space, the more intense the GPR wave scattering, The amplitude of the positive phase of ground direct wave is stronger. For the layered multi-phase discrete random medium with upper, middle and lower layer thicknesses of 4 cm, 6 cm and 8 cm respectively, the direct phase amplitude intensity of ground direct wave mainly depends on the polyphase The porosity of discrete random media is less affected by the porosity of the heterogeneously dispersed random medium in the middle layer. The amplitude intensity of the negative phase of the direct wave in ground surface is mainly The correlation between the void fraction and the amplitude of the random medium in the mid-plane is related to the increase of the void fraction. The amplitude of the direct and negative phase of the ground-surface direct wave has nothing to do with the void fraction of the heterogeneous random medium in the lower layer. The porosity of phase discrete random medium is directly proportional to the intensity of the reflected wave at the interface of the lower medium.The results provide a theoretical basis for quantitatively estimating the porosity of each layer of asphalt concrete by ground penetrating radar.