Modular rockfall wall
Case study .
Who you gonna call when you need test a Rockfall Wall?
A magnitude 7.8 earthquake in 2016 caused over 50 landslides along State Highway 1 north and south of Kaikoura, New Zealand. Damaging both road and railway infrastructure, it brought this key South Island route to a standstill.
After the quake, teams worked feverishly to restore State Highway 1 (SH1) and the Main North Line railway. The rockfall risk was a huge concern for both human safety, and damage to new infrastructure. A team was assembled to research, design, build and test an innovative solution.
The design and build of the Modular Rockfall Protection Wall (MRPW) was a team effort by the North Canterbury Transport Infrastructure Recovery Alliance (NCTIR); including Fulton Hogan, Stahlton Engineered Concrete and Geofabrics NZ Ltd.
The main challenges were space and time. They needed a rockfall protection solution to fit within the narrow coastal corridor and they needed it quickly. The team developed a practical solution using materials available on site – a key element being concrete blocks; a modified version of >7,000 concrete block used to build a new sea wall along parts of the corridor. After researching rockfall protection walls, they developed a new configuration that they thought would meet the project scope – but they needed to prove it worked.
Rockfall’s dynamic nature means it’s not easy to predict the performance of the wall with mathematical equations or computer models, so they needed to test the wall under real impact loading conditions. Fortunately for the NCTIR Alliance, the best team to help was on their doorstep.
Holmes Solutions design, develop and test complex, life‑safety products; including full scale, dynamic impact testing of roadside hardware products such as road safety barriers and anti-terrorism bollards. Our experience in high energy, dynamic testing was integral to completing this project. With not much test data available, we did a full review of national and international standards to find the right benchmark for product validation. We then developed a test programme to assess the impact of a full scale install with 750 kilojoules (kJ) of energy (ie. approx. 25% more energy than a 36,000 kg truck and trailer travelling at 80 km/hr impacting a safety barrier). With the test sample installed at our impact test facility, we began testing.
Watch this video to see what happened:
The results speak for themselves. After multiple impact tests, the Modular Rockfall Protection Wall met the test requirements. Special thanks to Eliot Sinclair who captured the tests using Leica P40 with 3D Reshaper software and drone. To learn more about the wider transport recovery effort click here.