Investigation of installation damage of some geogrids using laboratory tests

A series of laboratory tests simulating installation damage was carried out on four types of woven geogrid. Relationships between index properties of the geogrids and the loss in ultimate tensile strength, strain at failure and tensile stiffness of the geogrids are presented. For the geogrids investigated, the ratio of volume of coating material to the mass of yarn (V-M ratio) plays a major role in evaluating the loss of ultimate tensile strength: that is, the amount of ultimate strength loss decreases with an increase in V-M ratio. The V-M ratio also plays a part in the stress-strain characteristics of the damaged geogrids: for a regularly coated geogrid (PET yarn + PVC coating with a relatively low V-M ratio), similar amounts of ultimate strength and strain losses were found; for a similar geogrid with a relatively high V-M ratio, the amount of ultimate strain loss was only about 50% of the ultimate strength loss. The experimental results also indicate that the losses of tensile stiffness at 2% and 5% strains seem to be governed by the types of yarn and coating material, regardless of their V-M ratio.