Quality defects, such as noncompactness, cavity, and water leakage, typically appear behind tunnel linings given the lack of standardization and loose management in tunnel construction. Thus, a method for acquiring characteristic information from tunnel lining cavity fillings using frequency band energy of wavelet packet transform (FBEWPT) was proposed in this study to master the reflection characteristics of ground-penetrating radar (GPR) signal. A forward simulation of tunnel lining cavity fillings, including air, wet clay, silt, and water, w...
