Creep rupture behaviour of elastomeric bituminous geomembrane seams

The short-term and long-term performance of bituminous geomembrane (BGM) seams are examined using both small-scale and large-scale tests. Different BGM products, different sustained tensile loads, different weld qualities, and different overburden stresses are examined. The BGM seams are shown to be very susceptible to creep rupture under sustained tensile loads. Time to rupture and strain at rupture for acceptable welds are both exponentially correlated with the sustained load, for the different BGM products examined. With the increasing tensile load from 5%, 10%, 20%, 30%, 40% of sheet maximum tensile strength, the time to rupture decreased from 30-50 days (5%), 5 days (10%), 0.8 day (20%), 0.2 day (30%), to 0.03 day (40%) and, the strain at rupture increased from 5%, 7%, 13%, 17%, to 20-30%. In large-scale tests simulating field conditions, the BGM seam creep ruptured within 24 days when the overburden stress was 20 kPa, and within <= 0.2 day when the overburden stress reached 50 kPa. The consequences of liquids or gases readily permeating through failed seam should be evaluated before using BGMs in an environment where tensile stresses can develop (e.g. due to differential settlement, subgrade irregularity, or downdrag).