The mining industry's leach pads are some of the largest polyethylene geomembrane lined projects in the world. PE geomembranes have proven to be resistant to chemical attack, UV degradation and have demonstrated the ability to limit mechanical damage during over-liner placement. This paper is about the physical and mechanical properties that provide the liner with the ability to survive under the harsh conditions of bulldozers and other heavy equipment spreading the drainage layer, the stackers spreading the ore, and in some cases the huge loads caused by the many lifts of ore. As Engineers, our approach in the world of the civil works is through the concept of small strains, where the resistance of the materials to the stress is the key in almost every design. The world of the geomembrane under extreme loads, as is the case of the leach pads, is radically different; here "stress" is subordinated to "strain", transferring any structural function to the subgrade. This work has focused specifically in polyethylene ge-omembranes: High Density Polyethylene and Linear Low Density Polyethylene. The tests were carried out following the ASTM D 5514 standard, Procedure B, preparing a bed of coarse gravel embedded in a large epoxy plate (Rock Pizza). The maximum pressure applied to the geomembrane was 100 psi (690 kPa). The results of this research and the forensic analysis of the samples provide a very interesting insight; not just flexibility, but the stress relief condition provided by the yielding and creeping under stress, suggest that LLDPE geomembranes have the ability to deliver outstanding performance under similar conditions for long term applications such deep water reservoirs.