Seismic response in liquefiable soils

Sponsors: Rutherford Discovery Fellowship (RSNZ), Marsden Fund (RSNZ), NZ Earthquake Commission (EQC), Natural Hazards Research Platform (NHRP)

Collaborators: Misko Cubrinovski (UC), Chris McGann (UC), Russell Green (Virginia Tech)

Postgraduate researchers: Saumya Das, Kelly Robinson, Merrick Taylor, Brett Maurer (Virgina Tech)

Seismic response analysis of the Fitzgerald Avenue twin bridges illustrating the build up of excess pore water pressure and eventual liquefaction (Bradley et al. 2010).

The occurrence of liquefaction, as a result of earthquake-induced ground motions, can have significant impacts on the

functioning of urban areas. Damage and disruption as a result of liquefaction in the Christchurch earthquakes was particularly pervasive. Ground failure, as a result of liquefaction, is the principal cause of approximately 7000 residential houses in Christchurch being abandoned. This work is focused on the further development of robust analysis methods for assessing the seismic response of engineered structures which are founded on liquefiable soils. Particular attention is given to:

(i) simplified pseudo-static analysis methods for pile foundations in liquefiable soils (e.g. Cubrinovski and Bradley, 2009, Bradley et al. 2011, Haskell et al. (2012)); and

(ii) rigorous seismic effective stress analysis of soil-foundation-structure systems, incorporating uncertainties incident ground motions and system modelling (e.g. Cubrinovski and Bradley, 2009, Bradley et al. 2010).

Seismic effective stress analysis is also utilized in order to examine the improvements in seismic performance which are possible via ground improvement methods, as well as the consequent changes in the surface ground motions which will affect overlying structures (Bradley et al. 2011). This work is to be extended to examine if cost-effective ground improvement methods can be developed for application in residental construction (in comparison to past emphasis on commerical construction in which such costs were not as prohibitive).