隧道衬砌结构不规则空洞正演模拟与时频分析

Forward simulation and time-frequency analysis of irregular cavities in tunnel lining structure

为有效识别隧道衬砌结构各种形状的空洞,采用时域有限差分法进行正演模拟,分别分析空洞形状、充填介质和埋深对探地雷达电磁反射波成像效果和时频特征的影响,并通过室内模型试验进行验证。研究结果表明:空洞反射波的响应特征均表现为开口向下的抛物线。随着空洞上部边界由直线逐渐过渡至圆弧形或尖角形,正演模拟图中反射波的次数减少,反射信号减弱,且连续小波变换时频图中的能量值也越来越小。空洞埋深越浅,空洞充填介质的介电常数越大,则所得模拟图像的信号越强。该研究成果可为隧道衬砌结构内空洞周围的病害发育预测和判断提供参考。

To effectively identify various cavitiesin tunnel lining structures,the finite difference time domain method was used to forward simulation.The influence of cavity shape,filling medium and burial depth on electromagnetic reflection imaging effect and time-frequency characteristics of GPR was analyzed respectively.And those analyses were then validated through laboratory model tests.Results indicate that the reflection response characteristics of cavities are manifested by a downward-opening parabola.As the cavity top-boundary transitions gradually from straight line to arc or sharp angle,the number of reflection wave in the forward simulation decreases,the reflected signal is abate.Moreover,the energy in the continuous wavelet transform time-frequency diagram decreases gradually.The shallower the buried depth of the cavity and the larger the dielectric constant of the cavity filling medium,the stronger the simulated image signal.The results can provide reference for the prediction and judgment of disease development around cavities in tunnel lining structures.