title: Potassium acetate treatment as a potential means for stabilising extra sensitive, halloysite-rich soils in the Bay of Plenty, New Zealand — A novel approach to an old issue

authors: Robertson, Thomas Paul

subjects: Landslides

abstract: Landslides are a rapid, destructive natural hazard that pose a significant risk to human life and infrastructure. Globally and in New Zealand, landslides are among the most significant hazards. Within New Zealand, it is estimated that the annual costs associated with landslides are between NZ$250300 million, with over 600 fatalities recorded. While the types of landslides in New Zealand vary due to changeable geology and triggering conditions, one area that is particularly heavily affected is the Western Bay of Plenty region, specifically the Ōmokoroa peninsula, where numerous landslides have occurred. A key contributor to this instability is the presence of a series of weathered primary and reworked rhyolitic tephra deposits dominated by halloysite, known as the Pahoia Tephra, that exhibit a sensitive response. Based on successful tests undertaken in the Northern Hemisphere using potassium chloride salt wells, as well as a pilot study conducted on the same halloysitic materials, the research reported here aimed to treat a halloysite-rich sensitive soil with potassium acetate to determine if the soil could be regarded as strengthened. 
Atterberg limit testing of the soil showed the untreated Pahoia Tephra to have a liquid limit higher than the natural moisture content (61%), meeting the requirements for an extra-sensitive soil, as was determined by field shear vane tests. Treatment with the potassium acetate increased the liquid limit (58%65%) and reduced the liquidity index to below 1 (2.1 untreated, 0.57 treated). Treatment of the soil did produce a drastic increase in shear strength within the soil, with effective cohesion increasing from 4.2 kPa to 40.9 kPa following 12 months of treatment, while effective friction angle was slightly reduced from 29.8o to 25.3o. Stress paths of the soil show a large shift in behaviour, with samples no longer dilating during the pre-failure stage. 
To explain these changes, various mineralogical and chemical analyses were undertaken. X-ray diffraction analysis showed no expansion of the clay and lack of intercalation (all halloysite showing 10.1 Å). The Fourier transform infrared testing yielded a similar result, with no notable shifts observed in the 3600 cm-1 wavenumber peaks. With this said, new peaks corresponding to an interaction between potassium acetate and the silica sheet present within halloysite were noted. Scanning electron microscope analyses showed, following 12 months of treatment of the soil, a shrinking of the clay spheroids over the duration of treatment. 
From these findings, it was theorised that, while the potassium acetate did not intercalate into the halloysite spheroids themselves, the potassium acetate interacted with the external silica sheet so that it curled and rolled, resulting in a smaller spheroid, with acetate entering into the ditrigonal space within the silica sheet and displacing the H2O (‘water’) present. This resulted in a twofold action, with the second action leading to the creation of stronger short-chain van der Waals forces between clay spheroids, thereby increasing cohesion within the soil.
While the initial aim of this research was achieved, a large number of avenues have been opened that certainly warrant further investigation.

text: Potassium acetate treatment as a potential means for stabilising extra sensitive, halloysite-rich soils in the Bay of Plenty, New Zealand — A novel approach to an old issue Landslides are a rapid, destructive natural hazard that pose a significant risk to human life and infrastructure. Globally and in New Zealand, landslides are among the most significant hazards. Within New Zealand, it is estimated that the annual costs associated with landslides are between NZ$250300 million, with over 600 fatalities recorded. While the types of landslides in New Zealand vary due to changeable geology and triggering conditions, one area that is particularly heavily affected is the Western Bay of Plenty region, specifically the Ōmokoroa peninsula, where numerous landslides have occurred. A key contributor to this instability is the presence of a series of weathered primary and reworked rhyolitic tephra deposits dominated by halloysite, known as the Pahoia Tephra, that exhibit a sensitive response. Based on successful tests undertaken in the Northern Hemisphere using potassium chloride salt wells, as well as a pilot study conducted on the same halloysitic materials, the research reported here aimed to treat a halloysite-rich sensitive soil with potassium acetate to determine if the soil could be regarded as strengthened. 
Atterberg limit testing of the soil showed the untreated Pahoia Tephra to have a liquid limit higher than the natural moisture content (61%), meeting the requirements for an extra-sensitive soil, as was determined by field shear vane tests. Treatment with the potassium acetate increased the liquid limit (58%65%) and reduced the liquidity index to below 1 (2.1 untreated, 0.57 treated). Treatment of the soil did produce a drastic increase in shear strength within the soil, with effective cohesion increasing from 4.2 kPa to 40.9 kPa following 12 months of treatment, while effective friction angle was slightly reduced from 29.8o to 25.3o. Stress paths of the soil show a large shift in behaviour, with samples no longer dilating during the pre-failure stage. 
To explain these changes, various mineralogical and chemical analyses were undertaken. X-ray diffraction analysis showed no expansion of the clay and lack of intercalation (all halloysite showing 10.1 Å). The Fourier transform infrared testing yielded a similar result, with no notable shifts observed in the 3600 cm-1 wavenumber peaks. With this said, new peaks corresponding to an interaction between potassium acetate and the silica sheet present within halloysite were noted. Scanning electron microscope analyses showed, following 12 months of treatment of the soil, a shrinking of the clay spheroids over the duration of treatment. 
From these findings, it was theorised that, while the potassium acetate did not intercalate into the halloysite spheroids themselves, the potassium acetate interacted with the external silica sheet so that it curled and rolled, resulting in a smaller spheroid, with acetate entering into the ditrigonal space within the silica sheet and displacing the H2O (‘water’) present. This resulted in a twofold action, with the second action leading to the creation of stronger short-chain van der Waals forces between clay spheroids, thereby increasing cohesion within the soil.
While the initial aim of this research was achieved, a large number of avenues have been opened that certainly warrant further investigation.

year: 2025

title: Evolving web-based test automation into agile business specifications

authors: Mugridge, Rick

subjects: web test automation

abstract: Usually, test automation scripts for a web application directly mirror the actions that the tester carries out in the browser, but they tend to be verbose and repetitive, making them expensive to maintain and ineffective in an agile setting. Our research has focussed on providing tool-support for business-level, example-based specifications that are mapped to the browser level for automatic verification. We provide refactoring support for the evolution of existing browser-level tests into business-level specifications. As resulting business rule tables may be incomplete, redundant or contradictory, our tool provides feedback on coverage.

text: Evolving web-based test automation into agile business specifications Usually, test automation scripts for a web application directly mirror the actions that the tester carries out in the browser, but they tend to be verbose and repetitive, making them expensive to maintain and ineffective in an agile setting. Our research has focussed on providing tool-support for business-level, example-based specifications that are mapped to the browser level for automatic verification. We provide refactoring support for the evolution of existing browser-level tests into business-level specifications. As resulting business rule tables may be incomplete, redundant or contradictory, our tool provides feedback on coverage.

year: 2011

title: Quantifying relationships between kōura  (Paranephrops planifrons) abundance and micro-habitat features in Waikato hill-country streams

authors: Parata, Riki Neihana

subjects: kōura

abstract: Kōura (Paranephrops planifrons) is considered a taonga species by Māori and was once an abundant traditional fishery harvested throughout New Zealand. Kōura populations are under pressure in Waikato hill-country streams due to a range of factors including habitat loss and water quality degradation. Now that stakeholders have been engaging in collaborative decision-making and practices to restore/enhance biodiversity and ecosystem health within the Waikato catchment, there is opportunity to implement measures specifically targeted at kōura. Information on kōura habitat requirements to assist with the development of habitat enhancement work is therefore timely.
This research comprised two discrete studies which, in combination, provide important insights into daytime habitat use by kōura in Waikato hill-country streams. The first study was a field survey that examined in-stream habitat characteristics affecting kōura density and size, with a focus on juveniles ≤ 8 mm orbital carapace length (OCL), across a range of scales ranging from habitat patches to streams with contrasting catchment and riparian vegetation treatments – pasture, early or late riparian planting, and native forest. Micro-habitat variables related to kōura density included water depth and velocity, substrate size, and the area of bank undercuts and organic cover types, with root mat area significantly and positively related to juvenile densities across all scales. Although there was no significant effect of treatment type, there were strong associations between kōura and ponga logs, root systems, and coarse particulate organic matter (CPOM) across scales within and between streams.
The second study was a habitat manipulation experiment conducted to investigate whether kōura abundances, in particular juveniles, could be enhanced by additions of organic habitat consisting of 0.5 m² coconut fibre matting to simulate ponga (Cyathea dealbata) root systems that occur on the stream bank, and 1 m² ponga frond bundles to simulate the natural habitat structures formed in native forested areas. These two artificial habitats were compared with natural in-stream cobble habitats. Kōura and toi toi (Gobiomorphus spp.), both showed a preference for ponga frond habitats which were predicted to provide submerged habitat for more than 200 days. Although the coconut fibre matting was predicted to outlast ponga frond bundles by up to 107 days, it was more susceptible to sedimentation and did not provide adequate habitat for kōura due to its dense structure.
This study highlighted the influence of riparian treatments, hydrological processes, and inorganic and organic habitats on kōura populations. Information from this study can provide restoration managers with guidance on how to enhance in-stream and stream edge habitat suitability for kōura and can be used with existing mātauranga Māori, and western and community science, to determine suitable vegetation for riparian planting, assess what factors and drivers contribute to in-stream habitat availability and sustainability, and identify important habitat features that relate to kōura when conducting habitat restoration.

text: Quantifying relationships between kōura  (Paranephrops planifrons) abundance and micro-habitat features in Waikato hill-country streams Kōura (Paranephrops planifrons) is considered a taonga species by Māori and was once an abundant traditional fishery harvested throughout New Zealand. Kōura populations are under pressure in Waikato hill-country streams due to a range of factors including habitat loss and water quality degradation. Now that stakeholders have been engaging in collaborative decision-making and practices to restore/enhance biodiversity and ecosystem health within the Waikato catchment, there is opportunity to implement measures specifically targeted at kōura. Information on kōura habitat requirements to assist with the development of habitat enhancement work is therefore timely.
This research comprised two discrete studies which, in combination, provide important insights into daytime habitat use by kōura in Waikato hill-country streams. The first study was a field survey that examined in-stream habitat characteristics affecting kōura density and size, with a focus on juveniles ≤ 8 mm orbital carapace length (OCL), across a range of scales ranging from habitat patches to streams with contrasting catchment and riparian vegetation treatments – pasture, early or late riparian planting, and native forest. Micro-habitat variables related to kōura density included water depth and velocity, substrate size, and the area of bank undercuts and organic cover types, with root mat area significantly and positively related to juvenile densities across all scales. Although there was no significant effect of treatment type, there were strong associations between kōura and ponga logs, root systems, and coarse particulate organic matter (CPOM) across scales within and between streams.
The second study was a habitat manipulation experiment conducted to investigate whether kōura abundances, in particular juveniles, could be enhanced by additions of organic habitat consisting of 0.5 m² coconut fibre matting to simulate ponga (Cyathea dealbata) root systems that occur on the stream bank, and 1 m² ponga frond bundles to simulate the natural habitat structures formed in native forested areas. These two artificial habitats were compared with natural in-stream cobble habitats. Kōura and toi toi (Gobiomorphus spp.), both showed a preference for ponga frond habitats which were predicted to provide submerged habitat for more than 200 days. Although the coconut fibre matting was predicted to outlast ponga frond bundles by up to 107 days, it was more susceptible to sedimentation and did not provide adequate habitat for kōura due to its dense structure.
This study highlighted the influence of riparian treatments, hydrological processes, and inorganic and organic habitats on kōura populations. Information from this study can provide restoration managers with guidance on how to enhance in-stream and stream edge habitat suitability for kōura and can be used with existing mātauranga Māori, and western and community science, to determine suitable vegetation for riparian planting, assess what factors and drivers contribute to in-stream habitat availability and sustainability, and identify important habitat features that relate to kōura when conducting habitat restoration.

year: 2019