Strain gauging geotextiles using external gauge attachment method

Abstract

Measurement of geotextile deformation allows an in-depth understanding of the behaviour of geotextiles. However, attaching strain gauges to geotextiles poses a challenge as geotextiles are soft and have a fibrous surface. A properly installed strain gauge must not only adhere firmly to the geotextile, but also the method of strain gauge attachment must not change the surface properties of the geotextile significantly. Two common methods of geotextile strain measurement are attaching strain gauges directly to the geotextile with an adhesive agent and mounting electronic sensors by means of two end plates fixed to the geotextiles. The first method will inherently stiffen the localized area of the geotextile due to the introduction of the adhesive agent. In the second method, the electronic sensors are generally large, bulky and expensive. Therefore, a new strain gauging method is proposed which is intended to minimize or eliminate the limitations of the present strain measurement methods. This new method makes use of the idea of attaching gauges "externally" to a thin plastic strip whose ends are connected to the geotextile via two end plates. Hence, the geotextile region where the strain is measured remains virtually unaffected. Because of the relatively low modulus of the plastic strip, its strain is nearly the same as that of the geotextile. The results show that the proposed method is able to measure the true global strain developed in the geotextile with a correction factor of about 1.1. This method allows registration of strains up to about 10% and has very little stiffening effect on the geotextile.