Correctly locating the tunnel lining cavity is extremely important tunnel quality inspection. High-accuracy imaging results are hard to obtain because conventional one-way wave migration is greatly affected by lateral velocity change and inclination limitation and because the diffracted wave cannot be accurately returned to the real spatial position of the lining cavity. This paper presents a tunnel lining cavity imaging method based on the ground-penetrating radar (GPR) reverse-time migration (RTM) algorithm. The principle of GPR RTM is described in detail using the electromagnetic wave equation. The finite-difference timedomain method is employed to calculate the backward extrapolation electromagnetic fields, and the zero-time imaging condition based on the exploding-reflector concept is used to obtain the RTM results. On this basis, the GPR RTM program is compiled and applied to the simulated and observed GPR data of a typical tunnel lining cavity GPR model and a physical lining cavity model. Comparison of RTM and Kirchhoff migration results reveals that the RTM can better converge the diffracted waves of steel bar and cavity to their true position and have higher resolution and better suppress the effect of multiple interference and clutter scattering waves. In addition, comparison of RTM results of different degrees of noise shows that RTM has strong anti-interference ability and can be used for the accurate interpretation of radar profile in a strong interference environment.

正确定位隧道衬砌腔是非常重要的隧道质量检查。很难获得高精度的成像结果，这是因为常规的单向波迁移受横向速度变化和倾斜度限制的影响很大，并且由于衍射波无法准确地返回到衬砌腔体的实际空间位置。提出了一种基于探地雷达反时偏移算法的隧道衬砌空洞成像方法。使用电磁波方程式详细描述了GPR RTM的原理。采用时域有限差分法计算后向外推电磁场，并采用基于爆炸反射器原理的零时成像条件获得RTM结果。在此基础上，编译GPR RTM程序，并将其应用于典型隧道衬砌腔体GPR模型和物理衬砌腔体模型的模拟和观测GPR数据。通过对RTM和Kirchhoff偏移结果的比较发现，RTM可以更好地将钢筋和型腔的衍射波收敛到它们的真实位置，并且具有更高的分辨率，并且可以更好地抑制多重干扰和杂波散射波的影响。另外，通过比较不同噪声程度的RTM结果，可以看出RTM具有很强的抗干扰能力，可以在强干扰环境下用于雷达轮廓的准确解释。RTM和基尔霍夫迁移结果的比较表明，RTM可以更好地将钢筋和型腔的衍射波收敛到它们的真实位置，并且具有更高的分辨率，并且可以更好地抑制多重干扰和杂波散射波的影响。另外，通过比较不同噪声程度的RTM结果，可以看出RTM具有很强的抗干扰能力，可以在强干扰环境下用于雷达轮廓的准确解释。通过对RTM和Kirchhoff偏移结果的比较发现，RTM可以更好地将钢筋和型腔的衍射波收敛到它们的真实位置，并且具有更高的分辨率，并且可以更好地抑制多重干扰和杂波散射波的影响。另外，通过比较不同噪声程度的RTM结果，可以看出RTM具有很强的抗干扰能力，可以在强干扰环境下用于雷达廓线的准确解释。