- Subsidence, Elevation before and after the earthquakes. In centimeters.
- Lateral spreading quantified in direction and centimeters
- Changes in Groundwater. Due to changes in groundwater some land has lost the bearing capacity. Original foundations are designed for a particular land strength and wet sand versus dry sand can loose up to 50% of bearing capacity. This generates subsidence risk and increased Liquefaction vulnerability that has to be recognized and communicated.
- Liquefaction vulnerability. This is what caused most of the damage in canterbury. Information about vulnerability before and after the earthquake should be made available to the public.
- Flood risk before and after the earthquakes.
- 1/100 year Mike Flood map produced by DHI for EQC and Council should be made available to the public. (This is not private information for EQC)
The soils in the Christchurch CBD, being highly variable both horizontally and vertically across short distances, pose challenges for the design of structures and their foundations to withstand the potential impact of future large earthquakes. The Royal Commission considers that there must be greater focus on geotechnical investigations to reduce the risk of unsatisfactory foundation performance.
Tonkin and Taylor, for the Christchurch City Council (CCC), evaluated the nature and variability of subsurface conditions in the Christchurch CBD and adjacent commercial areas to the south and north-east. This will be held in a database available to the public. This information will be of assistance in assessing the potential need for land improvement, in the selection of appropriate foundation types, and in the planning of detailed investigation of foundation soils.
We make detailed recommendations in respect of site investigations, ground improvement and foundations design. Some recommendations are of particular relevance in the Christchurch CBD but many are of wider application.
– See more at: http://canterbury.royalcommission.govt.nz/Final-Report—Summary-and-Recommendations#sthash.43x9gQIi.dpuf”