Development and Testing of a Modular Rockfall Protection Wall To Mitigate Earthquake-Induced Slope Hazards

Rori Green, Cédric Lambert, Charlie Watts, Daniel Kennett and Emerson Ryder

The November 2016 M7.8 Kaikoura earthquake resulted in excess of 40 landslides that directly impacted the key road and rail corridor on New Zealand’s South Island. Within two months, the New Zealand Government formed the North Canterbury Transport Infrastructure Recovery (NCTIR) alliance, a team of more than 1700 workers who were tasked with restoring road and rail service by the end of 2017.

The work has involved a wide variety of landslide hazard mitigation measures that have included source treatment, installation of passive rockfall protection measures and relocation of sections of road further away from the base of the slope onto new seawalls. One of many challenges facing the geotechnical design team is space limitations along the narrow coastal corridor.

A modular rockfall protection wall has been developed to add to the suite of permanent rockfall protection structures in use on the project. The wall comprises interconnected concrete blocks with an upslope energy-absorbing layer of sand- filled and rock-filled gabions. The key advantages of the wall are a narrow footprint and a relatively fast installation time.

It was necessary to demonstrate the performance and capacity of the wall before it could be approved for use on site. Full-scale physical testing was performed at a vehicle impact testing facility. Six tests were undertaken to investigate sliding and overturning failure modes; impact energies were 250 and 750 kJ. Data collected during testing includes multiple high-speed videos and pre- and post-test laser scans.

The wall performed successfully, and it has been approved for use on site. The first installation is anticipated by mid-to- late 2018.