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)
5 Generalised subsurface profile (Section 1) Lenses liquefiable in SLS event, Liquefiable in ULS eventLenses liquefiable in ULS eventLenses liquefiable in ULS event
6 What 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.
7 Less over the soil layers Seismic PerformanceJet GroutPilesLiquefaction in ULS eventLess over the soil layersMore in each soil layerLateral spreadingApprox. 50mm75 to 150mmDifferential settlementTotal100mm30mmDifferential75mm
8 Jet Grout columns with thick concrete raft slab CellularSource: WAM (Aug 2013) Christchurch Town Hall – CCC Workshop Final Report (Rev A)
9 Jet Grout columns with thick concrete raft slab CellularSource: 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 themeg San Francisco Museum of Modern Art ($365 Million upgrade project)Add examples from ReLevel and VSL if receive these in time…