Fortescue Metals Group (FMG) is one the world’s largest producers of iron ore, operating multiple hubs in Western Australia. The wing walls of the primary ore crushing hub at its Solomon location needed protection from cyclonic rain and wind events, which are on the rise in its region.
PYRAMAT® 75 High Performance Turf Reinforcement Mat (HPTRM) was selected to protect the 60° batters because it is engineered to decrease sedimentation and retain soil during flood events. Additionally, it provides superior shear and tensile strength in addition to high UV resistance. Specialized Tek screws were utilized to fasten the PYRAMAT to the batter due to the extremely hard, cohesive nature of the Pindan fill material after compaction.
Performance criteria for slope protection materials have traditionally focused on hydraulic parameters like shear stress and flow velocity, but field performance is also highly dependent on UV resistance and tensile strength. This is especially true for arid environments like Pilbara where extreme heat during the dry seasons would normally preclude the use of polymer based soft armor solutions.
UV degradation is one of the most common failure mechanisms of permanent vegetated armoring systems, often lead by insufficient UV resistance and tensile strength (Koerner et al. 2005, Li and Khanna 2008). UV Resistance is reported as a percent of tensile strength retained of a HPTRM after a certain period of accelerated UV exposure when compared to the original tensile strength of the HPTRM. Per ASTM D-4355, PYRAMAT 75 HPTRM has 90% retention at 3,000 hours and 6,000 hours. This is six times greater than the UV protection provided by conventional turf reinforcement mats, making it ideal for arid environments.
Tensile strength is the primary property that determines the initial and long-term performance of the HPTRM, especially when non-hydraulic stresses are encountered. Non-hydraulic stresses can consist of loads from vehicular traffic during installation and maintenance. When the tensile strength is not adequate to account for non-hydraulic stresses incurred during the life of the project, material failure can occur. These types of failures can include ripping or tearing of the lining, lessening if not eliminating the improved hydraulic performance provided by the HPTRM. PYRAMAT 75 provides 58.4 x 43.8 kN/m of tensile strength to meet the durability, longevity and hydraulic design to ensure long-term performance.
The use of PYRAMAT 75 for slope protection is a cost effective and environmentally friendly solution that will provide up to 100 years of stabilization. PYRAMAT delivers the highest specification requirements for erosion protection of slopes and is the only HPTRM to have a verified carbon footprint by an independent third-party. The wing walls at the Solomon location continue to provide protection from flooding and show no signs of erosion.
