道路碎石垫层异常缺陷的探地雷达响应特征

采用探地雷达技术探测碎石垫层异常,研究碎石垫层脱落、碎石垫层层间具有密实-疏松界面、碎石垫层厚度变化及碎石垫层由松散块石充填4种异常的探地雷达响应特征。时域剖面评价、钻探资料验证、典型单道波形时域及频谱对比分析表明:碎石垫层脱落表现为同相轴的缺失,碎石垫层层间弱反射的反相性,谱能量分布在整个频率范围,且在550~800MHz出现较强信号;碎石垫层间存在密实-疏松界面表现为碎石垫层层间存在同相轴,谱能量集中在中低频区,能量峰较多;碎石垫层厚度变化表现为上下界面反射波时间差的大小(同相轴的上凸或下拉);碎石垫层由松散块石充填表现为强振幅复合波(同相轴杂乱,具有小绕射弧),谱能量峰叠加严重,峰值较大。

Characteristics of ground-penetrating radar response to abnormal defects of road gravel cushion

Ground-penetrating radar (GPR) technology was used to detect the abnormality of a gravel cushion, and the characteristics of GPR response to four abnormal defects, including gravel cushion shedding, gravel cushions with dense and loose interfaces, a gravel cushion with varied thickness, and a gravel cushion filled with loose rock, were studied. Through temporal profile evaluation, drilling data validation, and comparative analysis of a typical single-channel time-domain waveform and its frequency spectrum, the results show the following: the typical single- channel waveform for gravel cushion shedding is characterized by an absence of the event on the profile, the reverse phase of the weak reflection of the interlayer, spectral energy distributed over the whole frequency range, and strong signals appearing in the 550 to 800 MHz bands; the typical single-channel waveform for the gravel cushions with dense and loose interfaces presents the event on the profile, spectrum energy that concentrates in the low-frequency area, and more energy peaks; the typical single-channel waveform for a gravel cushion with varied thickness shows the time difference in reflected waves between the upper and lower interfaces (upward convex event or pull-down event); the typical single-channel waveform for a gravel cushion filled with loose rock shows strong-amplitude complex waves (a random event with a diffraction fringe), significant energy peak superposition, and a higher peak.