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Oda, Yoshihiro; Takasu, Tamio*; Sato, Hisashi; Sawada, Atsushi; Watahiki, Takanori*
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 67(2), p.186 - 197, 2011/04
Because of the density difference between fresh groundwater and saline groundwater, the groundwater behaves complicated flow. It is well known that the expected barrier functions such as candidate buffer materials and others for high level radioactive waste geological isolation are inhibited by the saline water. The simulations have been required to evaluate the groundwater flow, because the available data by in-situ investigation of the saline and fresh ground water flows is very limited. In the simulation, the complex coupled process of advection-dispersion, seepage flow and density drive flow should be implemented in the simulation codes. The extensive verification studies have been done for modeling and simulation codes until now, but those results were compared only with qualitative experimental data. For the quantitative evaluations, we developed the quantitative measurement technique by optical method for saltwater intrusion, especially for the saltwater concentration distribution in transition zone, on laboratory experiment. We have obtained the quantitative data of the shape of saltwater wedge and saltwater concentration distribution at both transient and steady states.
Sato, Hisashi; Takasu, Tamio*; Sawada, Atsushi
JAEA-Research 2008-105, 24 Pages, 2009/03
JAEA-Research-2008-105.pdf:1.89MB
In coastal area, the density difference between seawater and freshwater causes seawater intrusion under the freshwater. The methodology to evaluate saltwater distribution due to density driven flow might be crucial for bringing forward the radioactive waste disposal project. Although the extensive verification studies of the model for the salt water wedge have been reported, verification issue is still under the discussion. The saline concentration distribution in transition zone of salt water and fresh water was not evaluated, quantitatively. In order to obtain verification data of a numerical code that consider saltwater density distribution, we developed the quantitative measurement method by optical method for Mini-MACRO. And, quantitative concentration distribution data of saltwater wedge could be obtained. As a result, we showed that the width of the transition zone was narrower than the Henry's semi analytical result by quantitative data.
Takasu, Tamio*; Maekawa, Keisuke; Sawada, Atsushi
JAEA-Research 2008-030, 45 Pages, 2008/03
JAEA-Research-2008-030.pdf:2.29MB
It is important to evaluate relevant processes in geosphere, such as groundwater flow, based on the actual conditions of geological environment. At the coastal area, it is needed to understand groundwater flow under the saltwater and freshwater mixing conditions. We conducted a set of laboratory experiments using mass transport visualization system with flow chamber representing homogeneous sedimentary rock filled with uniform glass beads and double layer filled with different size of glass beads, in order to observe saltwater intrusion process into fresh water and saltwater-freshwater interface behavior. From the horizontal intrusion length of saltwater, the result might not depend on the size of glass beads and might be categorized by the combination of hydraulic gradient and saline concentration. In case of low hydraulic gradient case, the saltwater intrusion length tends to be larger due to saline concentration increase.
Takasu, Tamio*; Maekawa, Keisuke
JAEA-Technology 2006-061, 34 Pages, 2007/02
JAEA-Technology-2006-061.pdf:14.0MB
It is necessary for safety assessment of high-level radioactive waste geologic disposal to understand groundwater flow in deep underground accurately. Groundwater flow in the coastal area especially considered to be quite complex that involves density and hydraulic gradient driven flow of freshwater and seawater. Furthermore, bentonite, which is one of the favored engineered barrier materials, may not swell very well in seawater as it does in freshwater, and therefore may not provide a reliable seal if salinity is high enough. Therefore it is important to understand saltwater behavior in deep underground. In order to understand the behavior of seawater intrusion into freshwater in deep underground, we constructed a laboratory equipment "Mini-MACRO" named after the original large scale MACRO (MAss transport Characterization in host ROck) and aimed to increase a precision and efficiency of experiment. In this report we summarize the procedures of the equipment construction and the results of preliminary tests of saltwater intrusion into a freshwater body.
Maekawa, Keisuke; Karasaki, Kenji*; Takasu, Tamio*
no journal, ,
no abstracts in English
Maekawa, Keisuke; Karasaki, Kenji*; Takasu, Tamio*
no journal, ,
It is important for safety assessment of high-level radioactive waste geologic disposal to understand groundwater flow in deep underground accurately. In order to understand the behavior of seawater intrusion into freshwater in deep underground, we constructed a laboratory equipment, "Mini-MACRO" (MAss transport Characterization in host ROck). We created several cases of experimental conditions to observe the seawater intrusion behavior into two-layered stratum against various hydraulic gradients and densities of saltwater. We confirmed that the results using this equipment match numerical results under simple heterogeneous condition.
Sato, Hisashi; Sawada, Atsushi; Takasu, Tamio*
no journal, ,
no abstracts in English
Oda, Yoshihiro; Takasu, Tamio*; Sawada, Atsushi; Sato, Hisashi; Watahiki, Takanori*
no journal, ,
no abstracts in English
