Report No. : GEO Report No. 19

Report Title : A Review of the Phenomenon of Stress Rupture in HDPE Geogrids (1993), 68 p. (Reprinted, 1995)

Author : G.D. Small & J.H. Greenwood

Abstract

This report presents the results of an in-depth literature review of the phenomenon of stress rupture in HDPE geogrids. It covers the failure mehnisms of unoriented polyethylene and a review of relevant reaserach works undertakin by the gas supply industry.

The failure process on a molecular level is introduced and discussed in the context of drawn and oriented polyethylene materials. It is concluded that where there is scope for further change in the molecular structure in a polyethylene product there must also be the possibility of a change in failure mechanism. Tensar grids are intermediate in structure between unoriented material and highly drawn films and fibres.

Existing data for Tensar SR2, SR55, SR80 and SR110 geogrids are compiled and reviewed. The contributory factors to the material partial safety factor are also reviewed.

The possibility of a change in failure mechanism, leading to a reduction in extrapolated lifetime, is discussed. It is concluded that on existing evidence this is unlikely for Tensar geogrids.

Stress-rupture testing is required to substantiate the conclusions.

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