Non-destructive Method for Evaluating Grouted Ratio of Soil Nail Using Electromagnetic Wave

Abstract

Although soil nails have been widely used for stabilizing slopes, they are often only partially grouted. Thus, grouted ratio of soil nails should be evaluated to prevent landslides. The purpose of this study was to investigate the suitability of a non-destructive method using electromagnetic waves for evaluating grouted ratio of soil nails. Experimental studies were performed with steel bars, partially grouted steel bars, and fully grouted steel bars in air. Partially and fully grouted steel bars were also installed in soils to simulate soil nails installed on slopes. Electromagnetic waves were generated and received using a time domain reflectometer by configuring a two-conductor transmission line formed by two parallel steel bars or two parallel grouted steel bars. Results of experiments showed that the respective round-trip travel time of electromagnetic waves increased with increasing length of the steel bar, grouted steel bar in air, and grouted steel bar in soils. The velocity of electromagnetic waves was the greatest in steel bars but the lowest in grouted steel bars in soils. In addition, the velocity of the electromagnetic waves decreased with increasing grouted ratio. This study suggests that electromagnetic waves might be useful for evaluating grouted ratios of soil nails to stabilize slopes.