Britomart Tunnel – Load Transfer

Auckland, New Zealand


Meccanico played a crucial role in widening the Britomart tunnel for an upgraded Metro Line below Auckland City. Tasked with engineering the project, we designed temporary structural steel to support the demolition and devised the methodology for technically jacking the existing 400mm thick tunnel wall, which bore the load of a fifteen-storey building.

Simultaneously, we constructed a new wall in advance and closely monitored data on wall and tunnel soffit displacement every fifteen minutes during the construction phase. After completing the new wall, we strategically installed double acting 250-tonne locking jacks into the existing wall’s slots, using a synchronized system for systematic jacking based on target loads. Upon achieving our target loads, the jacks were mechanically locked, allowing us to cut the existing wall with the structure fully supported on the jacks. Subsequently, we activated a controlled lowering cycle, closely monitoring loads to ensure a slow and correct transfer onto the bearings and the new wall.


The challenges for this project were managing the sequence of technical tasks involved in the jacking process and the significant weight of the load being transferred from the old tunnel wall to the new tunnel wall. This had to be done incrementally by controlling the load in a negative cycle. During this phase of calculations we carefully lowered the jacks into decompression.


Meccanico designed the engineered, temporary works plan as well as the engineered methodology. This included calculations of what specific equipment could be used to achieve the best outcome for the lift and lowering process. We purchased twenty, 250 tonne, locking jacks from our partner, Holmatro and flew back to Amsterdam for further training. This was to ensure the project would be executed accurately and efficiently for Martinus Rail , NZTA and Kiwi Rail.


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