1. Christchurch Town Hall for Performing Arts
Post earthquake and foundation repair assessment
August 2013

2. 22 February 2011 – what happened??

3. Engineers are expected to design structures for two main states:
Design approach…
Engineers are expected to design structures for two main states:
Serviceability Limit State (SLS) - buildings are designed so that they suffer very little or no damage;
Ultimate Limit State (ULS) – buildings remain standing; people are able to safely leave the building. The building may be seriously damaged.
100% NBS = 100% of New Building Standard (Code)

4. Geotechnical investigation location plan

5. Generalised subsurface profile (Section 1)
Lenses liquefiable in SLS event, Liquefiable in ULS event
Lenses liquefiable in ULS event
Lenses liquefiable in ULS event

6. What can we do to repair the building foundations??
Narrowed down to two proposed options:
Preferred option
Jet grout columns with a thick concrete raft slab; or,
Alternative option
Large diameter bored piles around the perimeter of the buildings with small diameter micropiles beneath the complex.
An experienced specialist sub-contractor to the main contractor is required.

7. Less over the soil layers
Seismic Performance
Jet Grout
Piles
Liquefaction in ULS event
Less over the soil layers
More in each soil layer
Lateral spreading
Approx. 50mm
75 to 150mm
Differential settlement
Total
100mm
30mm
Differential
75mm

8. Jet Grout columns with thick concrete raft slab
Cellular
Source: WAM (Aug 2013) Christchurch Town Hall – CCC Workshop Final Report (Rev A)

9. Jet Grout columns with thick concrete raft slab
Cellular
Source: WAM (Aug 2013) Christchurch Town Hall – CCC Workshop Final Report (Rev A)

10. Jet Grout columns with thick concrete raft slab
NZ experience:
Jet grout operations beneath a several buildings in Christchurch has been undertaken. Details are not available due to insurance/ building owners preference.
Worldwide experience:
A number of existing buildings, gas and oil tank facilities have had jet grout columns installed underneath them
eg San Francisco Museum of Modern Art ($365 Million upgrade project)
Add examples from ReLevel and VSL if receive these in time…

11. END