基于GPR频谱分析的隧道空溶洞解译特征研究

Research on Interpretation Characteristics of Tunnel Empty Cave Based on GPR Spectrum Analysis

通过对完整灰岩和半灰岩半空气2种介质进行现场地质雷达试验,提出了一种新的解译方法,即时间域分段频谱分析法。该方法是先将现场探测的雷达数据进行时间域分段,再分别对各个时间域段进行频谱分析。试验发现:完整灰岩色谱图在0～300 ns时间域内,高振幅的频率主要集中在50～70 MHz,在300～600 ns时间域内,高振幅的频率主要集中在15～35 MHz,这在色谱图上表现为1条水平高振幅带;半灰岩半空气介质中,其灰岩部分色谱图仍有水平高振幅带的现象,而空气部分,其色谱图上高振幅频率分布呈无序状态。将二者结果进行对比并进行现场验证,结果表明,色谱图中水平高振幅带可以作为判别岩溶隧道中空溶洞发育的依据,能有效降低空溶洞对隧道的施工风险。

A new interpretation method, namely time domain segmentation spectrum analysis method, is proposed by conducting on-site geological radar experiments on two limestone and half limestone mediums. The method firstly performs time domain segmentation on the radar data detected on the spot, and then performs spectrum analysis on each time domain segment separately.The experiment found that the complete limestone chromatogram in the 0 to 300 ns time domain, the high amplitude frequency is mainly concentrated in 50 to 70 MHz, in the 300 to 600 ns time domain, the high amplitude frequency is mainly concentrated in the 15 to 35 MHz, which is shown as a horizontal high amplitude band on a chromatogram;in the semi-air semi-limestone medium, the chromatogram of the limestone still has a horizontal high-amplitude band phenomenon, while in the air part, the high-amplitude frequency distribution on the chromatogram is disordered. The results are compared and verified in the field. The results show that the horizontal high amplitude band in the chromatogram can be used as a basis for discriminating the development of hollow caves in karst tunnels, which can effectively reduce the construction risk of empty caves to tunnels.