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Journal Articles

Numerical evaluation of a multiple soil barrier system preventing water infiltration

Takayama, Yusuke*; Ikuta, Yuki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Taki, Tomihiro; Sakao, Ryota; Ichikawa, Yasuaki*

Unsaturated Soils; Research & Applications, p.659 - 665, 2014/06

In this paper, a multiple unsaturated soil barrier consisting of gravel, sand and bentonite-mixed soil layers is considered as a hardly permeable covering to prevent rainwater from infiltrating into waste deposits. Not only the quite low permeability of bentonite-mixed soil layer but also a function of capillary barrier between granular layers having different water-retention capabilities is expected to prevent water infiltration. A series of numerical simulation is carried out to evaluate performance of the multiple soil barrier using saturated/unsaturated soil/water coupled FE computation technique. The multiple unsaturated soil barrier system considered here is 10m long and 1.5 m thick consisting of sandy soil surface, sand filter, gravel layer, sand filter and bentonite-mixed clayey layer. And the soil barrier system is assumed to be placed as a covering with a 5% inclination on the waste deposit. The performance of the multiple soil barrier system is shown as a management chart to maintain impermeable ability associated with possible rainfall intensity. Particularly, in this paper, actual rainfall record in Okayama area is employed to determine the rainfall intensity which is imposed as a boundary condition in the computation. According to the simulation results, it is found that the capillary barrier is a key issue in evaluating the long term performance of the barrier system. And, it is confirmed that the barrier system considered in this paper can work well against the maximum intensity of the rainfall in the past record.

Oral presentation

Evaluation of drainage capability and settlement due to installation of multi-layered capping

Ikuta, Yuki*; Takayama, Yusuke*; Tsurumi, Shuhei*; Ichikawa, Yasuaki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Taki, Tomihiro; Sakao, Ryota

no journal, , 

As a part of remediation of closed uranium mine, "Yotsugi Mill Tailings Pond" has been remediated in Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency. The aim of remediation is to take measures to reduce the load of water treatment and the radon exposure to humans in future, and to prevent the occurrence of relevant environmental contamination. So far, the upstream of the Pond has been covered by the multi-layered capping in which layers are set to use gravel, sand and decomposed granite soil to drain penetrated rainwater to the neighboring river. This capping system needs to be monitored on a long-term basis and to be evaluated to work as expected in advance, therefore seepage analysis and settlement analysis has carried out. As a result, Settlement of analysis was well accorded with measured value and marked change of saturation accompanied by rain was not observed in the seepage analysis.

Oral presentation

Evalution of settlement at the upstream of the Mill Tailings Pond, Ningyo-toge Uranium Mine

Sasaki, Yosuke*; Takayama, Yusuke*; Ikuta, Yuki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Sakao, Ryota; Taki, Tomihiro

no journal, , 

As part of environmental remediation of Ningyo-toge Uranium Mine, multi-layered capping is constructed to reduce rainwater infiltration at the upstream of the Mill Tailings Pond. Settlement is expected due to consolidation characteristics of mill tailings and clayish sediments which exist below capping. Numerical simulation is carried out to expect the settlement amount during and after the capping construction. Settlement amount has been measured periodically, and the simulation result and measurement data are compared to evaluate the simulation method.

Oral presentation

Assessment of drainage capacity of cover soil

Okada, Mariko*; Ikuta, Yuki*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Sakao, Ryota; Ohara, Yoshiyuki

no journal, , 

no abstracts in English

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