HR: 0800h
AN: V41A-1361    [Abstracts]
TI: A Hand-made Gas Permeameter for Permeability Measurement of Small Samples of Natural and Experimental Volcanic Materials.
AU: * Takeuchi, S
EM: takeuchi@geo.titech.ac.jp
AF: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo, 152-8551 Japan
AU: Nakashima, S
EM: satoru@geo.titech.ac.jp
AF: Interactive Research Center of Science, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-ku, Tokyo, 152-8551 Japan
AB: Gas permeability in vesiculating magma, in which connected bubble network is developing, is an essential physical property controlling behavior of volcanic eruptions, since the gas permeability varies drastically in vesiculating processes during magma ascent. Although there are several studies on gas permeability of vesiculating magma, they have been limited in permeability measurements of natural samples, and their numerical simulations. For further understanding of gas permeability development in vesiculating magma, the permeability measurement on experimental products produced by vesiculating experiments is an effective approach. However, since the size of experimental run products is generally from 1 mm to 1 cm scale, they are too small to be measured by using commercial gas permeameter. In this study, we constructed a hand-made gas permeameter to measure permeability of small samples such as experimental run products. The hand-made permeameter can measure permeability in the wide range from 10$^{-17}$ to 10$^{-10}$ m $^{2}$ within the precision of one order for mm scale samples. Nitrogen gas is used as a working gas in this measurement system. The permeability is calculated by steady gas flow rate at fixed pressure difference up to 15000 Pa (ca. 0.15 atm). The pressure difference is measured with accuracy of 10 Pa by a water column manometer. Gas flow rate is converted to water flow rate in an acrylic container and the water flow seeping from the tube into a beaker is monitored by an electric balance. We confirmed the accuracy in permeability values by measuring gas flow in stainless capillary tube (15 mm in length and 100 mm in inner diameter). We carried out flow measurement at 1.8\times10$^{2}$-1.4\times10$^{4}$ Pa in pressure difference and 3.0\times10$^{-10}$-3.6\times10$^{-8}$ m$^{3}$/s in flow rate. For this flow rate, Reynolds number of the gas flow is estimated to be 10$^{-2}$-10$^{0}$. Therefore, the gas flow can be assumed to be Poiseuille flow. Although the difference between the measured and calculated flow rates increases with decreasing flow rate, the discrepancy is about 40 % at the maximum for the flow rate more than 10$^{-10}$ m$^{3}$/s. Therefore, measurement of the pressure difference and gas flow rate in this measurement system is precise enough to determine the permeability within 0.4 log unit. Using this measurement system, permeabilities of four air-fall pumice and scoria were measured. The results are in good agreement with a trend obtained from permeability measurement of pyroclastic materials by Klug and Cashman (1996). This consistency also supports the validity of this permeameter. This permeability measurement system can be constructed easily at a very low cost, and is expected to be a useful tool to measure permeability of small volcanic materials and experimental run products.
DE: 8414 Eruption mechanisms
DE: 5114 Permeability and porosity
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting