Instrumentation of geogrids using novel non-invasive electrical sensing

Accurate strain measurement of geogrids has been challenged by several factors, many of which are due to the unfavourable environmental conditions which geosynthetics are subject to. Existing contributions have seen deployment of standard strain measurement techniques including piezoresistive and fibre-optic sensors. These have faced limitations with poor survivability, low accuracy, and changes to the physical geogrid structure which subsequently alter geogrid behaviour. This report presents a novel, non-invasive, electrical sensor designed for use on geosynthetics specifically. A direct shear apparatus (DSA) was used to apply confining pressure up to 300kPa and strain up to 9.0% to the sensor-enabled geogrids in both dry and wet soil conditions to assess the performance of the novel sensor. Signal phase angle was measured at a range of frequencies at 1mm DSA intervals. Geogrid strain was derived from DSA displacement and a linear response between phase angle and strain has been observed. The findings of this study indicate that the sensor is sensitive to strain and resistant to adverse environmental conditions without modification to the geogrid structure. This is significant as it means that the sensor can be used for instrumentation in field-based applications, particularly where the geogrid is used for soil stabilisation.