Abstract: Geogrids have been widely used in soil reinforcement projects. In the current reinforced-soil design standards in China, the tensile strength of geogrids is generally used as the only index in the control. But there are many other factors affecting the effect of soil reinforcement in addition to tensile strength, such as, goegrid production technology, mesh shape, grid size and rib shape etc. In order to study the bearing and deformation behavior of geogrid-reinforced soils, five series of in-situ plate load tests were performed on one non-reinforced and four different types of geogrids reinforced soils. The experimental results showed that the bearing ratio of goegrid-reinforced foundation can be improved to 1.19~1.43, and the measured settlement can be reduced more than 50% at least. And it is important that the reinforcement effect is not proportional to the tensile strength of geogrids, rather, it is more related to the geogrids type, grid size and structural integrity. The best reinforcement effect by the products was ranked as Tensar TriAx, biaxial oriented geogrids, welded biaxial geogrids, and knitted biaxial geogrid. Because of its special triangular mesh structure and size, the interaction effect between the TriAx geogrids and the sand soil is more obvious, so the characteristic value of the bearing capacity can be increased by 43%, the settlement can be reduced 63%, and the settlement mainly occurs in the upper gravelly soil cushion. Too small or too large grid dimension and peeling features of welding or knitting nodes have an adverse effect to the overall reinforcement effect. Therefore, for the design of the reinforced-soil structure and reinforcement selection, the engineers should not simply take the tensile strength as the only design index, but should pay attention to the physical structure characteristics and mesh size.

Key words: geogrids-reinforced soils, triaxial geogrids, mesh structure, bearing ratio, load tests