An entry from Deb Robertson's blog for 17 July 2016 entitled, "If Cabin pressure is lost, put your own oxygen mask on first...."The entry was downloaded on 3 November 2016.
Well-validated liquefaction constitutive models are increasingly important as non-linear time history analyses become relatively more common in industry for key projects. Previous validation efforts of PM4Sand, a plasticity model specifically for liquefaction, have generally focused on centrifuge tests; however, pore pressure transducers installed at several free-field sites during the Canterbury Earthquake Sequence (CES) in Christchurch, New Zealand provide a relatively unique dataset to validate against. This study presents effective stress site response analyses performed in the finite difference software FLAC to examine the capability of PM4Sand to capture the generation of excess pore pressures during earthquakes. The characterization of the subsurface is primarily based on extensive cone penetration tests (CPT) carried out in Christchurch. Correlations based on penetration resistances are used to estimate soil parameters, such as relative density and shear wave velocity, which affect liquefaction behaviour. The resulting free-field FLAC model is used to estimate time histories of excess pore pressure, which are compared with records during several earthquakes in the CES to assess the suitability of PM4Sand.
Photograph captioned by BeckerFraserPhotos, "It's not easy to spot, but look at the floor level in this picture. By the bar, it's about half a metre higher than in the foreground. Pressure under the floor pushed the whole floor up".
A sewage pumping station on Avonside Drive has been lifted out of the ground by liquefaction. In the background, the damaged Snell Place footbridge over the Avon River is closed off with cordon fencing. The photographer comments, "A Sunday afternoon ride to New Brighton, then back via Aranui, Wainoni, Dallington, and Richmond. Not a cheerful experience. Dallington footbridge. The two pieces of this foot bridge have moved towards each other, so the bridge has developed quite a peak. The sewage pumping station has been heaved out of the ground by hydraulic pressure during quakes".
Results from a series of 1D seismic effective stress analyses of natural soil deposits from Christchurch are summarized. The analysed soil columns include sites whose performance during the 2010-2011 Canterbury earthquakes varied significantly, from no liquefaction manifestation at the ground surface to very severe liquefaction, in which case a large area of the site was covered by thick soil ejecta. Key soil profile characteristics and response mechanisms affecting the severity of surface liquefaction manifestation and subsequent damage are explored. The influence of shaking intensity on the triggering and contribution of these mechanisms is also discussed. Careful examination of the results highlights the importance of considering the deposit as a whole, i.e. a system of layers, including interactions between layers in the dynamic response and through pore water pressure redistribution and water flow.
A video of a presentation by Dr Duncan Webb, Partner at Lane Neave, during the third plenary of the 2016 People in Disasters Conference. The presentation is titled, "Loss of Trust and other Earthquake Damage".The abstract for this presentation reads as follows: It was predictable that the earthquakes which hit the Canterbury region in 2010 and 2011 caused trauma. However, it was assumed that recovery would be significantly assisted by governmental agencies and private insurers. The expectation was that these organisations would relieve the financial pressures and associated anxiety caused by damage to property. Some initiatives did exactly that. However, there are many instances where difficulties with insurance and related issues have exacerbated the adverse effects of the earthquakes on people's wellness. In some cases, stresses around property issues have become and independent source of extreme anxiety and have had significant impacts on the quality of people's lives. Underlying this problem is a breakdown in trust between citizen and state, and insurer and insured. This has led to a pervading concern that entitlements are being denied. While such concerns are sometimes well founded, an approach which is premised on mistrust is frequently highly conflicted, costly, and often leads to worse outcomes. Professor Webb will discuss the nature and causes of these difficulties including: the complexity of insurance and repair issues, the organisational ethos of the relevant agencies, the hopes of homeowners and the practical gap which commonly arises between homeowner expectation and agency response. Observations will be offered on how the adverse effects of these issues can be overcome in dealing with claimants, and how such matters can be managed in a way which promotes the wellness of individuals.
A video of a presentation by David Meates, Chief Executive of the Christchurch District Health Board and the West Coast District Health Board, during the first plenary of the 2016 People in Disasters Conference. The presentation is titled, "Local System Perspective".The abstract for this presentation reads as follows: The devastating Canterbury earthquakes of 2010 and 2011 have resulted in challenges for the people of Canterbury and have altered the population's health needs. In the wake of New Zealand's largest natural disaster, the health system needed to respond rapidly to changing needs and damaged infrastructure in the short-term in the context of developing sustainable long-term solutions. Canterbury was undergoing system transformation prior to the quakes, however the horizon of transformation was brought forward post-quake: 'Vision 2020' became the vision for now. Innovation was enabled as people working across the system addressed new constraints such as the loss of 106 acute hospital beds, 635 aged residential care beds, the loss of general practices and pharmacies as well as damaged non-government organisation sector. A number of new integration initiatives (e.g. a shared electronic health record system, community rehabilitation for older people, community falls prevention) and expansion of existing programs (e.g. acute demand management) were focused on supporting people to stay well in their homes and communities. The system working together in an integrated way has resulted in significant reductions in acute health service utilisation in Canterbury. Acute admission rates have not increased and remain significantly below national rates and the number of acute and rehabilitation bed days have fallen since the quakes, with these trends most evident among older people. However, health needs frequently reported in post-disaster literature have created greater pressures on the system. In particular, an escalating number of people facing mental health problems and coping with acute needs of the migrant rebuild population provide new challenges for a workforce also affected by the quakes. The recovery journey for Canterbury is not over.