GNH Intersection Seal Design – Hope Downs

Ground Civil was recently (September 2025) engaged by Q H M Birt Pty Ltd to deliver seal design and readiness verification for the Great Northern Highway (GNH) intersection works at the Hope Downs 1 Sustaining Project.

Our role encompassed site inspections, field testing, and technical review to ensure the project met the highest standards of pavement durability and safety. The works included:

 

• • Detailed field texture measurements using the Sand Patch method in line with AGPT-T250, targeting both newly widened shoulders and existing carriageway wheel paths. Texture depths ranged from 1.8 mm to 3.6 mm, confirming the need for careful binder rate adjustments and pre-seal surface treatment.

• • Assessment of basecourse via Ball Embedment tests (MRWA WA312.1) across multiple chainages, with average embedment values confirming compaction and readiness for sealing.

• • Comprehensive laboratory analysis of sealing aggregates for both 10 mm and 16 mm grades per AS 1141 series, with Average Least Dimension (ALD) values in the 6.4–6.6 mm (10 mm aggregate) and 11.4–11.5 mm (16 mm aggregate) ranges, supporting robust seal design in accordance with Austroads using SR45 PMB binder specifications.

Pre-treatment recommendations were developed for high-texture sections and areas of surface non-uniformity, ensuring the final double/double seal will deliver long-term, low-maintenance performance—even in demanding Pilbara conditions.

This project demonstrates Ground Civil’s expertise in pavement investigations, technical compliance, and innovative seal design for large-scale regional infrastructure.

For more on our road and highway solutions, or to see further project details, contact our engineering team.