The long term design strength of a geogrid used for slope or wall reinforcement may be controlled
by the magnitude of tensile creep rupture strength or tensile creep strain at the end of the design life. Creep rupture
strength affects the margin of safety against attaining an ultimate limit state of collapse while creep strain is required to comply with prescribed serviceability limits. To determine long term strength and creep modulus it is necessary
to extrapolate test data u,v to 106 hours. Examples of extrapolation models for tensile creep rupture. strength are given and test data for tiniaxially oriented HOPE geogrids are analyzed to demonstrate the numerical range of
extrapolated results obtained for different assumptions.