The interaction characteristics of geosynthetics with fill materials are the key factors for geosynthetic reinforcement projects; hence

it is essential to study interaction characteristics by pull out tests. The comprehensive investigation into the interaction characteristics of 5 kinds of domestic geosynthetics with sand and lime fly ash was presented by pull out tests. Experimental results show: (1) Lime fly ash is light in unit weight

high in shear strength and its pull out coefficient (Cpo); therefore

it is ideal fill material; (2) Geosynthetics are arranged in Cpo from high to low: polyester (PET)warp knitting geogrids

uniaxial/biaxial oriented geogrids

geonets and geotextiles; (3) The variation of Cpo for various geosynthetics and fill materials is larger

hence Cpo should be determined through pull out tests for concrete projects. These conclusions can be used to guide choosing geosynthetic type and to make research on geosynthetic reinforcement mechanism.