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Evaluating soil and landscape models to predict liquefaction susceptibility in the Hinuera Formation, Hamilton Basin

The Hinuera Formation, being an extensive alluvial deposit throughout the Hamilton Basin plains, has been identified by Kleyburg (2015) as being susceptible to liquefaction. As much of the infrastructure of the Hamilton Basin is based on the Hinuera Formation, liquefaction thus poses a risk to the population of the area. This research project aims to develop a susceptibility model for liquefaction within the Hinuera Formation. Cone Penetration Test (CPT) data collected during investigation for the Hamilton Section of the Waikato Expressway were acquired from the NZ Geotechnical Database. CLiqᵀᴹ software was used to analyse these data and determine the liquefaction potential index (LPI) of each CPT site. Soil map information (S-Map) was provided by Waikato Regional Council with the permission of Landcare Research, and Digital Elevation Data (DEM) by Waikato Regional Council. Parameters of slope, elevation, soil family and sibling number as well as the LPI derived from CLiqᵀᴹ were input into STATISTICAᵀᴹ and analysed using I-Tree analysis to determine the most influential factor to liquefaction. ArcGIS was then implemented to create landscape/soil models based on CLiqᵀᴹ data as well as calculations identified by statistical analysis. The Hinuera Formation was found to have an overall susceptibility to liquefaction, ranging from low to high LPI dependant on depth. At a depth of 10 m, liquefaction potential on average was high, when compared to 3 and 5 m depths that showed a low to moderate LPI. At 3 m depth, which is most likely to show surface manifestation, liquefaction potential was low to moderate with the majority being considered as having a low LPI. Soil textures ranged from coarse sand, to silt, to clay with few organics. When LPI was related to soil behaviour index (Ic) soil that had a ‘mixed’ texture of silty sand/sandy silt were most susceptible to liquefaction (~1.8-2.4 Ic). Much of the calculated liquefaction occurrence within CLiqᵀᴹ directly correlated to these sand/silt soil textures. Soil that was nearer to granular (coarse sand) or clay–like in behaviour were shown to likely inhibit liquefaction occurrence. Soil family, a pedological map (and taxonomic) class, was shown to provide a good initial indication of the physical conditions of the underlying liquefiable soil, and therefore in turn liquefaction potential of land on the plains within the Hamilton Basin. A correlation between soil family and topography was identified using statistical analysis showing Utuhinaf and Kaipakif as most susceptible. Both Utuhinaf and Kaipakif soil families are of an organic texture (associated with peat formation). This observation led to the conclusion that areas of peat formation are likely correlated to the underlying soils having a relatively high susceptibility to liquefaction. This correlation is based on the knowledge that for peat formation to occur the land must have little relief (flat to a slight depression) and a high water table, both of which are prerequisites for liquefaction. Elevation was also shown as a good initial indicator of liquefaction potential where a range between 38–39 m showed the highest liquefaction potential. When compared to a Digital Elevation Model (DEM) it was found that liquefaction potential was higher within interfluve and floodplain zones and lower in topography with a greater relief such as within the many paleo channels or low ridges of the Hamilton Basin. This is likely a result of the soil textures being finer with a higher silt component within the interfluve and floodplains due to the low energy depositional environment that is associated with these topographic features. Based on the observations of soil family and topography being correlated to liquefaction susceptibility, two liquefaction susceptibility maps were developed to provide a preliminary assessment map.
Type of thesis
McKay, A. M. (2017). Evaluating soil and landscape models to predict liquefaction susceptibility in the Hinuera Formation, Hamilton Basin (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/11635
The University of Waikato
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