Research on propagation characteristics of L (0, 2) mode guided waves in the pipe with soil cover conditions

In highway guardrail systems, the buried section of pipes with soil filling on the interior results in discrepancies during guided wave inspection. This study investigates the propagation characteristics of L (0, 2) mode guided waves in the pipes, particularly focusing on the effects of soil cover conditions on wave behavior. Using modal analysis within the COMSOL, we simulated the dispersion curves and displacement distribution structures of guided waves in different modes. The L (0, 2) mode was selected for its relatively stable wave speed and minimal radial displacement, making it suitable for the study of guided wave propagation characteristics under various soil cover conditions. A finite element simulation model was developed to account for guided wave propagation in steel pipes with different soil cover conditions. This study observed diminished reflection echoes at the transition from the exposed to the soil-covered pipeline section, concomitant with a minor reduction in wave velocity within the soil-covered regions. Specifically, the L (0, 2) mode guided waves exhibited alterations in both wave velocity and reflection coefficients across varying soil cover conditions. The velocity decrement was approximated to 1.5 % with external soil cover and escalated to about 3.5 % with combined internal and external soil cover. Experimental validation substantiated the propagation characteristics of L (0, 2) mode guided waves in steel pipes under soil cover conditions. The findings provide a theoretical foundation for the detection of burial length in guardrail steel pipes.