Abstract: In view of the difference of tensile properties between in-soil and in-air geosynthetics, a tensile testing device for geosynthetics in soil was developed. Movable sleeve was adopted in the device to keep the geosynthetics in soil, which addressed the interference problem caused by the friction between the filling and the fixture; the friction of soil against the sleeve was also considered. Sliding track of double smooth rod was designed to ensure the low-friction directional movement of the fixture sleeve, and also avoided the eccentric stress of geosynthetic material in the tensile process. The upper and lower air pressure bags kept the geosynthetics in close contact with the soil and withstand confining pressure. The device could accomplish tensile test of geosynthetics both in soil and in air, as well as confined tensile test, creep test and in-soil pullout test. The device was applied to the in-air tensile test, in-soil tensile test and confined tensile test for five different types of geosynthetics. Results suggest that tensile strength was slightly affected by the friction between geosynthetics and soil; while confining pressure is the major cause of the huge difference between in-soil and in-air tensile strength. The quantitative relationship between the in-air and in-soil tensile strength or the confined tensile strength was obtained for engineering reference. The in-soil tensile strength or confined tensile strength can be deduced through the in-air tensile strength.

Key words: geosynthetics, tensile strength, in-soil tensile, in-air tensile, quantitative relationship, confined lateral tensile