非均质机场水泥道面板底脱空雷达波响应

Radar wave response of slab bottom voids in heterogeneous airport concrete pavement

为研究机场刚性道面配筋与非均质材料对板底脱空探地雷达波响应的影响规律,采用PFC3D离散元模拟和gprMax电磁仿真构建道面多相非均质电磁差分模型,进而建立板底脱空长度与脱空顶部反射波幅值的函数关系.研究结果表明:雷达波信号在非均质中的波场快照和剖面图呈现随机扰动特征,含水脱空回波信号受非均质材料衰减作用影响显著;脱空与钢筋层间形成能量团,增强了脱空回波信号,空气脱空回波信号受能量团增强作用显著.脱空长度小于第一临界点时,回波信号振幅强度与脱空长度呈二次函数相关;脱空长度大于第一临界点时,随脱空长度的增长,振幅先下降,后在第二临界点保持不变.该研究为探地雷达定量估算水泥道面板底脱空的长度发展提供了理论依据.

To study the influence principles of rebars and heterogeneous materials on the ground-penetrating radar wave responses of slab bottom voids, the simulations of PFC3D discrete element and gprMax electromagnetic were adopted to build multiphase heterogeneous electromagnetic difference models. The models were used to build a relationship between the lengths of the slab bottom voids and the amplitudes of radar echo signals in the top of the voids. The results of numerical experiments demonstrate that wavefield snapshots and profiles of radar wave signals in heterogeneous medium show random disturbance characteristics. The echo signals of a water-containing void are significantly affected by the attenuation of heterogeneous materials. There is an energy cluster between the bottom void and the rebar layer, which enhances the amplitudes of the void echo signals. The echo signals of the air-filled voids are significantly enhanced by the energy cluster. When the void length is smaller than the first critical point, the amplitude of a void echo signal is quadratically related to the void length, while when the void length is larger than the first critical point, the amplitude first decreases with the increase in the void length and then remains unchanged at the second critical point. This study provides a theoretical basis for the quantitative measurement of the voids at the bottom of concrete pavement slab by ground-penetrating radar.