Experimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion

In Japan, as in other countries, bentonite-based buffer materials are expected to play roles in reducing stress from rock masses and mitigating nuclide migration in the geological disposal of high-level radioactive waste. These roles are achieved by ensuring buffer density and thickness based on the...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	Tomoko ISHII, Masahiro KAWAKUBO, Ichizo KOBAYASHI, Yuichi NIIBORI
Formato:	article
Lenguaje:	EN
Publicado:	The Japan Society of Mechanical Engineers 2020
Materias:	engineered barrier buffer material bentonite piping erosion scale effect Mechanical engineering and machinery TJ1-1570
Acceso en línea:	https://doaj.org/article/fd13181984c34704aacbe025234dcc40
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:fd13181984c34704aacbe025234dcc40
record_format	dspace
spelling	oai:doaj.org-article:fd13181984c34704aacbe025234dcc402021-11-29T05:56:30ZExperimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion2187-974510.1299/mej.19-00469https://doaj.org/article/fd13181984c34704aacbe025234dcc402020-04-01T00:00:00Zhttps://www.jstage.jst.go.jp/article/mej/7/3/7_19-00469/_pdf/-char/enhttps://doaj.org/toc/2187-9745In Japan, as in other countries, bentonite-based buffer materials are expected to play roles in reducing stress from rock masses and mitigating nuclide migration in the geological disposal of high-level radioactive waste. These roles are achieved by ensuring buffer density and thickness based on the swelling characteristics of clay. However, in practical construction, we should also consider bentonite buffer piping erosion, a phenomenon in which the buffer surface is destroyed by groundwater flowing between the buffer and rock. Such piping erosion may be a serious issue for maintaining an engineered barrier for radioactive waste in the geological system. In this study, the dynamic behaviors of piping erosion were experimentally investigated. In the experiments, 500 mm φ × 600 mm height compacted bentonite specimens were placed in a cylindrical acrylic cell and distilled water was continuously injected at a flow rate of 0.1 L/min from the bottom and the side of the cell. The amount of bentonite that flowed out of the cell was measured by turbidity of the suspended clay in the drainage water. In the results, while the bentonite specimen swelled between about 10 and 20 days and attached to the inside wall of the cell, a dominant flow channel (piping) was observed between the swelled bentonite specimen and the inside wall of the cell. In addition, the relationship between the accumulated amounts of injected water and eroded bentonite showed a constant slope on double logarithmic plots. Such behaviors indicate that the shear stress due to water flow locally exceeded the swelled bentonite’s shear strength. Furthermore, the slopes were similar to those already reported from a test using a smaller size cell. These results suggest that piping erosion proceeds with a simple regularity and that piping erosion in actual-scale bentonite buffers can be predicted using small-scale data.Tomoko ISHIIMasahiro KAWAKUBOIchizo KOBAYASHIYuichi NIIBORIThe Japan Society of Mechanical Engineersarticleengineered barrierbuffer materialbentonitepipingerosionscale effectMechanical engineering and machineryTJ1-1570ENMechanical Engineering Journal, Vol 7, Iss 3, Pp 19-00469-19-00469 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	engineered barrier buffer material bentonite piping erosion scale effect Mechanical engineering and machinery TJ1-1570
spellingShingle	engineered barrier buffer material bentonite piping erosion scale effect Mechanical engineering and machinery TJ1-1570 Tomoko ISHII Masahiro KAWAKUBO Ichizo KOBAYASHI Yuichi NIIBORI Experimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion
description	In Japan, as in other countries, bentonite-based buffer materials are expected to play roles in reducing stress from rock masses and mitigating nuclide migration in the geological disposal of high-level radioactive waste. These roles are achieved by ensuring buffer density and thickness based on the swelling characteristics of clay. However, in practical construction, we should also consider bentonite buffer piping erosion, a phenomenon in which the buffer surface is destroyed by groundwater flowing between the buffer and rock. Such piping erosion may be a serious issue for maintaining an engineered barrier for radioactive waste in the geological system. In this study, the dynamic behaviors of piping erosion were experimentally investigated. In the experiments, 500 mm φ × 600 mm height compacted bentonite specimens were placed in a cylindrical acrylic cell and distilled water was continuously injected at a flow rate of 0.1 L/min from the bottom and the side of the cell. The amount of bentonite that flowed out of the cell was measured by turbidity of the suspended clay in the drainage water. In the results, while the bentonite specimen swelled between about 10 and 20 days and attached to the inside wall of the cell, a dominant flow channel (piping) was observed between the swelled bentonite specimen and the inside wall of the cell. In addition, the relationship between the accumulated amounts of injected water and eroded bentonite showed a constant slope on double logarithmic plots. Such behaviors indicate that the shear stress due to water flow locally exceeded the swelled bentonite’s shear strength. Furthermore, the slopes were similar to those already reported from a test using a smaller size cell. These results suggest that piping erosion proceeds with a simple regularity and that piping erosion in actual-scale bentonite buffers can be predicted using small-scale data.
format	article
author	Tomoko ISHII Masahiro KAWAKUBO Ichizo KOBAYASHI Yuichi NIIBORI
author_facet	Tomoko ISHII Masahiro KAWAKUBO Ichizo KOBAYASHI Yuichi NIIBORI
author_sort	Tomoko ISHII
title	Experimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion
title_short	Experimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion
title_full	Experimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion
title_fullStr	Experimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion
title_full_unstemmed	Experimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion
title_sort	experimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion
publisher	The Japan Society of Mechanical Engineers
publishDate	2020
url	https://doaj.org/article/fd13181984c34704aacbe025234dcc40
work_keys_str_mv	AT tomokoishii experimentalapproachforunderstandingthedynamicbehaviorsofbentonitebufferpipingerosion AT masahirokawakubo experimentalapproachforunderstandingthedynamicbehaviorsofbentonitebufferpipingerosion AT ichizokobayashi experimentalapproachforunderstandingthedynamicbehaviorsofbentonitebufferpipingerosion AT yuichiniibori experimentalapproachforunderstandingthedynamicbehaviorsofbentonitebufferpipingerosion
_version_	1718407625011363840

Experimental approach for understanding the dynamic behaviors of bentonite buffer piping erosion

Ejemplares similares