3Engineers 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)
5Generalised subsurface profile (Section 1) Lenses liquefiable in SLS event, Liquefiable in ULS eventLenses liquefiable in ULS eventLenses liquefiable in ULS event
6What can we do to repair the building foundations?? Narrowed down to two proposed options:Preferred optionJet grout columns with a thick concrete raft slab; or,Alternative optionLarge 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.
7Less over the soil layers Seismic PerformanceJet GroutPilesLiquefaction in ULS eventLess over the soil layersMore in each soil layerLateral spreadingApprox. 50mm75 to 150mmDifferential settlementTotal100mm30mmDifferential75mm
8Jet Grout columns with thick concrete raft slab CellularSource: WAM (Aug 2013) Christchurch Town Hall – CCC Workshop Final Report (Rev A)
9Jet Grout columns with thick concrete raft slab CellularSource: WAM (Aug 2013) Christchurch Town Hall – CCC Workshop Final Report (Rev A)
10Jet 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 themeg San Francisco Museum of Modern Art ($365 Million upgrade project)Add examples from ReLevel and VSL if receive these in time…