A Comparrative Study on Strength Characteristics of Some Geogrids in Japan

Abstract

Five major geogrids currently in extensive use in Japan were tested for their engineering properties approximately under the same conditions for; 1) tensile strength characteristics, 2) creep characterstics, 3) friction between geagrids and sand determined by pulll-out tests and other characterstics.
Since each brand has several types having different tensile strengths, the properties of the five different geogrids having approximately the same nominal strength of the order of 50KN/m were compared. While all the results showed ultimate tensile strengths exceeding the nominal strength, the strains at failure varied widely between roughly 2 and 15%, each brand exhibiting a consistent rigidity.
Creep tests were conducted for specimens consisting of two or more strands which were subjected to a constant load ranging from 10 to 90% of the nominal load for a period up to more than 1000 hours. The creep strength is a function of the load applied and the resulting strain which appears to have a unique correlation with the short-term tensile test result.
The pull-out test results indicated that the apparent friction angle between the geogrids and sand ranged from about 15 to 30 degrees being considerably smaller than the angle of internal friction of the sand.