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Images, eqnz.chch.2010

Cleaning up the silt and sand from Hoon Hay properties. Here Laura, Robbie, and Ronny are part of the clean-up crew on Wyn Street.

Research papers, The University of Auckland Library

Soil-structure interaction (SSI) has been widely studied during the last decades. The influence of the properties of the ground motion, the structure and the soil have been addressed. However, most of the studies in this field consider a stand-alone structure. This assumption is rarely justifiable in dense urban areas where structures are built close to one another. The dynamic interaction between adjacent structures has been studied since the early 1970s, mainly using numerical and analytical models. Even though the early works in this field have significantly contributed to understanding this problem, they commonly consider important simplifications such as assuming a linear behaviour of the structure and the soil. Some experimental works addressing adjacent structures have recently been conducted using geotechnical centrifuges and 1g shake tables. However, further research is needed to enhance the understanding of this complex phenomenon. A particular case of SSI is that of structures founded in fine loose saturated sandy soil. An iconic example was the devastating effects of liquefaction in Christchurch, New Zealand, during the Canterbury earthquake in 2011. In the case of adjacent structures on liquefiable soil, the experimental evidence is even scarcer. The present work addresses the dynamic interaction between adjacent structures by performing multiple experimental studies. The work starts with two-adjacent structures on a small soil container to expose the basics of the problem. Later, results from tests considering a more significant number of structures on a big laminar box filled with sand are presented. Finally, the response of adjacent structures on saturated sandy soil is addressed using a geotechnical centrifuge and a large 1g shake table. This research shows that the acceleration, lateral displacement, foundation rocking, damping ratio, and fundamental frequency of the structure of focus are considerably affected by the presence of neighbouring buildings. In general, adjacent buildings reduced the dynamic response of the structure of focus on dry sand. However, the acceleration was amplified when the structures had a similar fundamental frequency. In the case of structures on saturated sand, the presence of adjacent structures reduced the liquefaction potential. Neighbouring structures on saturated sand also presented larger rotation of the footing and lateral displacement of the top mass than that of the stand-alone case.

Research papers, University of Canterbury Library

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.

Images, UC QuakeStudies

People walking amongst silt in Hagley Park shortly after the 22 February 2011 earthquake. These silt deposits were caused by the soil liquefying during the 22 February 2011 earthquake. The water flowed out, bringing sand with it.

Images, UC QuakeStudies

A pile of liquefaction silt on Medway Street is cordoned off with road cones. The photographer comments, "Piles of sand and subsiding roads at the intersection of Medway St with Woodchester Ave and Flesher Ave, 10 days after the February quake".

Images, UC QuakeStudies

People walking amongst silt in Hagley Park shortly after the 22 February 2011 earthquake. These silt deposits were caused by the soil liquefying during the 22 February 2011 earthquake. The water flowed out, bringing sand with it.

Images, UC QuakeStudies

A photograph of contractor Tony Fisher of Fisher Agricultural Ltd. inspecting a dug-out soil pit on a farm near River Road in Lincoln. There is a thick layer of saturated sand between the topsoil and the subsoil where the grass roots end.

Videos, UC QuakeStudies

A video of a tractor on a farm near River Road in Lincoln. The tractor is making a several passes over a sand volcano with a rotary hoe. This was one of several soil-remediation techniques tested on farms affected by the 4 September 2010 earthquake.

Videos, UC QuakeStudies

A video of a tractor on a farm near River Road in Lincoln. The tractor is passing over a large sand volcano with a power harrow. This was one of several soil-remediation techniques tested on farms affected by the 4 September 2010 earthquake.

Videos, UC QuakeStudies

A video of a dug-out soil pit on a farm near River Road in Lincoln. There is a thick layer of saturated sand between the topsoil and the subsoil where the grass roots end. The saturated soil is collapsing as a result of contractor Tony Fisher, of Fisher Agriculture Ltd, jumping lightly up and down on the edge of the pit.