Thackeray Place, Christchurch

Problem: Due to earthquakes, the large building (five, two-storey units and five garages), needed re-levelling. The weight of the building when floating on the Hydraulic Jacks, was approximately 618 tonne. 

Solution: The front four units and west wall of the fifth unit, were re-levelled using ‘Jack and Pack’ for the perimeter foundations and walls. The reinforced concrete ground floor slabs were re-levelled using steel trusses, and threaded steel rods were temporarily set into the floors.

Prior to re-levelling, the Geotechnical Report showed the floors had a Level difference of over 100mm, and Grades in excess of 1.6%.

The floors were re-levelled to within 7mm within the units (±10mm within the garages). Evidence before re-levelling showed the floor levels varied considerably prior to the earthquakes, so the ground floor after re-levelling was considered to be more level than it ever was.

After the floors were re-levelled, grout was pumped through holes in the floors to fill cavities below, and the filling checked by GPR: ground-penetrating radar, to ensure there were no cavities left unfilled below.