基于GprMax对路面地下缺陷探地雷达的正演模拟研究

Research on GPR Forward Simulation of Pavement Subsurface Defects Based on GprMax

摘要: 在交通基础设施长期使用过程中，车辆载荷、环境因素、施工工艺等各种复杂的因素都会给地下结构造成空洞、裂缝或者脱空等问题。本文利用GprMax对探地雷达数据进行正演模拟，分析不同情况下地下空洞的雷达图特征。得到的正演结果二维剖面结果表明：不同大小的空洞，空洞体积越大下方反射或者散射效应所产生的次级弱回波信号越多。不同介质对雷达回波的影响产生的也不同，相比空气、砂石、水三种介质，其中空气介质的反射最强，砂石介质最弱。不同形状的空洞对产生正演回波图像的电磁波传播路径和能量分布规律也不同。不同深度的空洞其深度越深能量反射越弱。正演模拟实际空洞与实际空洞图谱变化基本一致。对于城市道路的浅层深度0.3~1.5 m的空洞，600 MHZ的天线能较为清晰地观察出空洞形状和深度。结合实际案例，通过对比正演模拟的雷达回波图谱得到较为一致的结果，可为探地雷达检测地下病害提供理论支持和依据。

Abstract: In the long-term use of transportation infrastructure, vehicle loads, environmental factors, construction technology and other complex factors will cause problems such as cavities, cracks or voids in underground structures. In this paper, GprMax is used to carry out forward simulation of GPR data, and analyze the radar map characteristics of underground cavities under different conditions. The two-dimensional section results of the forward modeling results show that the larger the cavity volume, the more secondary weak echo signals are generated by the reflection or scattering effect. Different media have different effects on radar echo. Compared with air, sand and water, the reflection of air media is the strongest and sand and stone media is the weakest. The propagation path and energy distribution of electromagnetic wave generated by different shapes of cavities are also different. The deeper the hole is, the weaker the energy reflection is. The forward simulation of actual cavity pairs is basically consistent with the changes of actual cavity spectra. For the cavity with a shallow depth of 0.3~1.5 m in urban roads, the 600 MHz antenna can clearly observe the shape and depth of the cavity. Combined with the actual case, the more consistent results are obtained by comparing the forward simulation radar echo spectrum, which can provide theoretical support and basis for the detection of underground diseases by GPR.