Report No. : GEO Report No. 176

Report Title : Interim Report on Non-destructive Tests for Checking the Integrity of Cement Grout Sleeve of Installed Soil Nails (2005), 45 p.

Author : W.M. Cheung & D.O.K. Lo


As part of the development work in enhancing the quality control of soil nail installation works, an in-house project has been conducted by the Geotechnical Engineering Office of Civil Engineering Department to identify and develop practical non-destructive means for checking the integrity of cement grout sleeve.

The study has identified three techniques for field trial. They are the Sonic Echo Method, Surface Wave Time Domain Reflectometry and the Electrical Resistance Method. The findings of the field tests are discussed in the Report.

Based on the study, it is considered that the Electrical Resistance Method has the highest potential for field application. The method is capable of identifying soil nails of significant grouting defects or anomalies. However, the method cannot distinguish explicitly the type of defects, which may be in the forms of grout defect or atypical short reinforcement. Nevertheless, the Electrical Resistance Method looks promising as a quick, convenient and economical means to aid identifying soil nails that have significant grouting defects.

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