Nondestructive health monitoring of soil nails using electromagnetic waves

Abstract

The installed length and grouted length of a soil nail should be evaluated to prevent construction disasters and landslides. The objective of this study is the development and application of a nondestructive method for evaluating the installed length and grouted length of soil nails using electromagnetic waves. Experiments are conducted on steel bars, partially grouted steel bars, fully grouted steel bars, and soil nails. Electromagnetic waves are generated and detected by a time-domain reflectometer. The experimental results show that the respective round-trip travel times increase with an increase in the length of the steel bar, grouted steel bar, and soil nail. The velocities are greatest and lowest for steel bars and soil nails installed in soil, respectively. For partially grouted steel bars, multiple reflections are detected at the interface between the nongrouted sections and grouted sections. The velocity decreases with an increase in the grouted ratio of the soil nail. This study demonstrates that electromagnetic waves can be effectively applied for the evaluation of the installed length and grouted length of the soil nail for health monitoring.