Rockfall Protection Structures on a Critical Lifeline in Christchurch

Following the 2010/11 Canterbury Earthquake Sequence in Christchurch, significant rockfall, cliff collapse and mass movement features occurred around the Port Hills. The Sumner-Lyttelton Corridor is a critical link between Lyttelton Port and Christchurch CBD for transportation of oversized and hazardous goods and suffered extensive rockfall and slope failures from the earthquakes. Sections of the Sumner-Lyttelton Corridor have been kept operational through the use of temporary rockfall protection measures in the form of ballasted shipping containers. The Wakefield Avenue section of the Sumner-Lyttelton Corridor had three areas affected by rockfall and cliff collapse, which were temporarily protected by ballasted shipping containers. This paper focuses on the design of the permanent rockfall protection structures at two sites along Wakefield Avenue which will allow the removal of the shipping containers and mitigate the rockfall and cliff collapse geo-hazards in the long term. The project involved carrying out geotechnical investigations, identifying the rockfall sources, mapping existing rockfall, modelling rockfall trajectories, ground truthing modelling outputs, design of rockfall protection structures and providing assistance to the client during consenting and construction. It is concluded that important considerations for the design and construction of rock fall protection structures include detailed topographic surveys, stormwater management, service clashes and safe construction methodology.