A New Method to Determine Hydraulic Conductivity and Storage Coefficient through Simultaneous Measurements of Fluid Pressure and Strains

The concept of storage coefficient was discussed based on the theory of poroelasticity. Several different storage coefficients can be defined by different mechanical boundary conditions and assumptions on the physical properties of constitutive materials. The specific storage, which is usually used in the field of hydrogeology, is shown to be defined when the representative elementary volume is maintained in a state of zero lateral strain and constant stress perpendicular to that plane. This means that the specific storage is not measured in most laboratory pore pressure tests because the boundary condition of zero lateral strain is not satisfied. Instead, we measure a three-dimensional storage coefficient. In the latter sections of this paper, we present a new method to determine both the hydraulic conductivity and the storage coefficient through simultaneous measurements of fluid pressure and strains. In this study, a new endplug with a built-in valve was developed to accurately measure the poroelastic parameters. Our experimental assembly significantly reduces the extra volume of the system and is readily adapted to the various pore-fluid boundary conditions. The three-dimensional storage coefficient was calculated from the volumetric poroelastic parameters obtained from quasi-static strain data, and the hydraulic conductivity from the transient pore pressure diffusion data. Transient strain behavior during the pore pressure diffusion stage was used to self-check the accuracy of the parameters obtained. This technique does not require complicated inversion calculations and can be used easily for parameter identification

Distribution of atmospheric SF6 around urban area in Japanhttp : Impact for groundwater dating using SF6

To understand distribution of the atmospheric SF6 mixing ratio is vital for groundwater dating using SF6. Monitoring of the atmospheric SF6 ratios were conducted at three major metropolitan areas and one rural area, to clarify spatial distribution of the atmospheric SF6 in and around urban area in Japan. All the measured values exceeded Nor thern Hemisphere clean air levels. The average excess ratioswere 102% in Tokyo, 53% in Osaka, 30% in Nagoya and 15% in Chubu mountainous area. These excess causes an underestimate from 3 to 17 years in apparent SF6 age, suggesting that adjustment of the input air cur ve is necessar y when the SF6 method is applied to the groundwater dating in Japan.大気濃度の分布を理解することは，SF6による地下水年代推定の生命線である。日本国内の大気SF6濃度の空間分布を明らかにするために，東京・名古屋・大阪の三大都市と都市域から離れた中部地方の山岳地域において大気濃度の観測を実施した。すべての観測地点の濃度は北半球の清浄大気の濃度を超過していた。東京・大阪・名古屋・中部地方の山岳地域の平均超過率はそれぞれ103％，52％，30％および15％であった。これらの超過は3～17年の見掛けSF6年代の過小見積もりを生じさせるため，日本でSF6による地下水年代推定を実施するためには大気濃度の補正が必要である

流体圧力と歪を用いた透水係数と貯留係数の新しい測定法

The concept of storage coefficient was discussed based on the theory of poroelasticity. Several different storage coefficients can be defined by different mechanical boundary conditions and assumptions on the physical properties of constitutive materials. The specific storage, which is usually used in the field of hydrogeology, is shown to be defined when the representative elementary volume is maintained in a state of zero lateral strain and constant stress perpendicular to that plane. This means that the specific storage is not measured in most laboratory pore pressure tests because the boundary condition of zero lateral strain is not satisfied. Instead, we measure a three-dimensional storage coefficient. In the latter sections of this paper, we present a new method to determine both the hydraulic conductivity and the storage coefficient through simultaneous measurements of fluid pressure and strains. In this study, a new endplug with a built-in valve was developed to accurately measure the poroelastic parameters. Our experimental assembly significantly reduces the extra volume of the system and is readily adapted to the various pore-fluid boundary conditions. The three-dimensional storage coefficient was calculated from the volumetric poroelastic parameters obtained from quasi-static strain data, and the hydraulic conductivity from the transient pore pressure diffusion data. Transient strain behavior during the pore pressure diffusion stage was used to self-check the accuracy of the parameters obtained. This technique does not require complicated inversion calculations and can be used easily for parameter identification

Surface environment of Phobos and Phobos simulant UTPS

International audienceThe Martian Moons eXploration (MMX) mission will study the Martian moons Phobos and Deimos, Mars, and their environments. The mission scenario includes both landing on the surface of Phobos to collect samples and deploying a small rover for in situ observations. Engineering safeties and scientific planning for these operations require appropriate evaluations of the surface environment of Phobos. Thus, the mission team organized the Landing Operation Working Team (LOWT) and Surface Science and Geology Sub-Science Team (SSG-SST), whose view of the Phobos environment is summarized in this paper. While orbital and large-scale characteristics of Phobos are relatively well known, characteristics of the surface regolith, including the particle size-distributions, the packing density, and the mechanical properties, are difficult to constrain. Therefore, we developed several types of simulated soil materials (simulant), such as UTPS-TB (University of Tokyo Phobos Simulant, Tagish Lake based), UTPS-IB (Impact-hypothesis based), and UTPS-S (Simpler version) for engineering and scientific evaluation experiments