Performance Evaluation of Electrical Strain Gauges and Optical Fiber Sensors in Field Soil Nail Pullout Tests

摘要

The pullout resistance of soil nails installed in slopes is affected by a number of factors. The measurement of the pullout resistance and the shear resistance of the soil nail is required. The existing technique of using electrical strain gauges monitoring pullout tests has limitations. This paper introduces two types of optical fibre sensors and associated devices for measurements of strain distnbution in soil nails. The two types of sensors were calibrated first in the laboratory. Typical calibration results are presented.Afterwards, the two types of optical fibre sensors were used to monitor strains of two Fibre Reinforced Polymer (FRP) soil nails in Hong Kong together with electrical resistance-type strain gauges. The field test data were collected and anaiysed. In particular, the strains measured by the two types of optical fibre sensors are compared to those by electrical strain gauges and are found to be in good agreement. The advantages of optical fibre sensors are presented.