title: Geotechnical properties of liquefied pumiceous layers in lakes

authors: Chaneva, Jordanka

subjects: geotechnical properties

abstract: Earthquake failures in volcanic-ash soils are relatively common, considering their physical nature and the fact that such deposits tend to occur in areas with high seismicity in which the volcanism, responsible for their emplacement, shares some tectonic-related origin. However, experimental and empirical data related to geotechnical properties and mechanical behavior of volcanic-ash soils are still quite limited compared to those for hard-grained soils. Moreover, the limited data largely focus on pumiceous sands, whereas pumiceous silts have not been significantly investigated to date. This study summarizes relevant geotechnical properties of volcanic-ash layers preserved in lake sediments in the Hamilton lowlands in North Island, New Zealand. These highly pumiceous layers are hypothesized to have liquefied within the past 20,000 years, based on paleo-liquefaction features observed in some of the lakes. The layers that are liquefaction susceptible were identified. Additionally, the pumiceous layers were characterized by means of specific gravity, fines content, and pumice content. Finally, the characteristic void ratios (i.e., 𝑒min, 𝑒max) of five samples were analyzed. Pumiceous silts exhibit higher characteristic void ratios than those for hard-grained soils.

text: Geotechnical properties of liquefied pumiceous layers in lakes Earthquake failures in volcanic-ash soils are relatively common, considering their physical nature and the fact that such deposits tend to occur in areas with high seismicity in which the volcanism, responsible for their emplacement, shares some tectonic-related origin. However, experimental and empirical data related to geotechnical properties and mechanical behavior of volcanic-ash soils are still quite limited compared to those for hard-grained soils. Moreover, the limited data largely focus on pumiceous sands, whereas pumiceous silts have not been significantly investigated to date. This study summarizes relevant geotechnical properties of volcanic-ash layers preserved in lake sediments in the Hamilton lowlands in North Island, New Zealand. These highly pumiceous layers are hypothesized to have liquefied within the past 20,000 years, based on paleo-liquefaction features observed in some of the lakes. The layers that are liquefaction susceptible were identified. Additionally, the pumiceous layers were characterized by means of specific gravity, fines content, and pumice content. Finally, the characteristic void ratios (i.e., 𝑒min, 𝑒max) of five samples were analyzed. Pumiceous silts exhibit higher characteristic void ratios than those for hard-grained soils.

year: 2022-04-29

title: Instability of a plane conducting free surface submitted to an alternating magnetic field

authors: Fautrelle, Y.

abstract: This paper considers the stability of a horizontal liquid-metal free surface in the presence of a horizontal alternating magnetic field. A weak formulation is used to derive a generalized Mathieu–Hill equation for the evolution of surface perturbations. Previous studies which rely on time-averaging the electromagnetic force over one field cycle have predicted a generally weak instability, but we find much larger growth rates near the resonances, where the surface wave frequency is an integral multiple of the field frequency. The method can be extended to include viscous and ohmic damping; the former has little effect, while the latter damps all waves except those whose frequency is close to the field frequency. Growth rates can be closely approximated by simple algebraic formulae, as can the critical magnetic field strength for the onset of instability.

text: Instability of a plane conducting free surface submitted to an alternating magnetic field This paper considers the stability of a horizontal liquid-metal free surface in the presence of a horizontal alternating magnetic field. A weak formulation is used to derive a generalized Mathieu–Hill equation for the evolution of surface perturbations. Previous studies which rely on time-averaging the electromagnetic force over one field cycle have predicted a generally weak instability, but we find much larger growth rates near the resonances, where the surface wave frequency is an integral multiple of the field frequency. The method can be extended to include viscous and ohmic damping; the former has little effect, while the latter damps all waves except those whose frequency is close to the field frequency. Growth rates can be closely approximated by simple algebraic formulae, as can the critical magnetic field strength for the onset of instability.

year: 1998

title: An evaluation of Te Rau Puawai workforce 100: Perspectives of Te Rau Puawai bursars

authors: Nikora, Linda Waimarie

subjects: Maori students

abstract: The Te Rau Puawai programme is an attempt to change the nature of the Maori
mental health workforce. To do this, Maori with aspirations to work, or to continue to
work in the mental health workforce, are supported, financially and academically, to
complete a tertiary qualification relevant to the field.
To evaluate the Te Rau Puawai programme, the Ministry of Health commissioned the
Maori and Psychology Research Unit of the University of Waikato in July 2001. The
overall aim of the evaluation was to provide the Ministry with a clearer understanding
of the programme including: the perceived critical success factors, the barriers if any
regarding Te Rau Puawai, the impact of the programme, the extent to which the
programme may be transferable, gaps in the programme, and suggested
improvements.
The evaluation team set out to gather the experiences and perspectives of recipients of
Te Rau Puawai services by asking all bursars to complete a questionnaire and
volunteer for follow up interviews or focus groups. Sixty two bursars responded to
our questionnaire, and we complete focus group or individual follow up interviews
with 19 bursars.

text: An evaluation of Te Rau Puawai workforce 100: Perspectives of Te Rau Puawai bursars The Te Rau Puawai programme is an attempt to change the nature of the Maori
mental health workforce. To do this, Maori with aspirations to work, or to continue to
work in the mental health workforce, are supported, financially and academically, to
complete a tertiary qualification relevant to the field.
To evaluate the Te Rau Puawai programme, the Ministry of Health commissioned the
Maori and Psychology Research Unit of the University of Waikato in July 2001. The
overall aim of the evaluation was to provide the Ministry with a clearer understanding
of the programme including: the perceived critical success factors, the barriers if any
regarding Te Rau Puawai, the impact of the programme, the extent to which the
programme may be transferable, gaps in the programme, and suggested
improvements.
The evaluation team set out to gather the experiences and perspectives of recipients of
Te Rau Puawai services by asking all bursars to complete a questionnaire and
volunteer for follow up interviews or focus groups. Sixty two bursars responded to
our questionnaire, and we complete focus group or individual follow up interviews
with 19 bursars.

year: 2002-05-01