Puncture resistance of geotextiles and evaluation of the g-rating classification system

The puncture resistance of geotextiles in Australia is measured in terms of the G-Rating,\ud which is the product of CBR and drop cone puncture test results.\ud CBR and drop cone puncture tests were conducted on 24 geotextiles to provide up-to-\ud date results, and to evaluate the G-Rating. CBR puncture tests using modified\ud plungers were also conducted to assess the accuracy of shape factors quoted in the\ud literature- 3.0 for angular aggregate and 0.8 for rounded aggregate. Wide strip\ud tensile tests were also conducted to compare with CBR puncture test results.\ud The results of the testing program show no relationship between wide strip tensile\ud test results and CBR puncture test results. The modified plunger CBR puncture test\ud results show that shape factors are not only shape dependent, but are fabric\ud dependent as well, with the results somewhat different from those commonly\ud quoted. The exponent used to calculate the G-Rating varies for the same fabric\ud tested at different drop heights in the drop cone puncture test. Also, the restriction\ud of elongation in CBR puncture tests to 80 per cent by the G-Rating classification\ud system, was found unnecessary for all the geotextiles tested, as elongation at failure\ud in all cases did not exceed 80 per cent.\ud A Rupture Index classification is proposed, being the product of failure load and\ud vertical plunger displacement at failure in a CBR puncture test. It is considered to\ud be simpler than the G-Rating as it relies on the results of only one test. The\ud Rupture Index calculated for a given fabric will not vary by more than the inherent\ud variability of the specimens tested. However, G-Rating values were shown to vary\ud considerably for the same fabric tested at different drop heights in the drop cone\ud puncture test