  The pull test is a destructive detection method, and it can t measure the
actual length of the bolt. As such, ultrasonic echo is one of the most
important non-destructive testing methods for bolt quality detection. In this
paper, the variance modal decomposition method is introduced into the bolt
detection signal analysis. Based on the morphological filtering and the VMD
method, the VMD combined morphological filtering principle is established into
the bolt detection signal analysis method. MF-VMD was used in order to analyze
the simulation vibration signal and the actual bolt detection signal. The
results showed that the MF-VMD is able to effectively separate the intrinsic
mode function, even when under the background of strong interference. Compared
with the conventional VMD method, the proposed method is able to remove the
noise interference. The intrinsic mode function of the field detection signal
can be effectively identified by the reflection of the signal at the bottom of
the bolt.
