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Soil–Bentonite Cutoff Walls for Geoenvironmental Containment
Abstract Cutoff walls used for prevention of the migration of mobile contaminants in the aquifer must maintain high barrier performance for a long period. Soil–bentonite (SB), which is a mixture of in situ soil and bentonite, has many advantages as a barrier material such as appropriate deformability, homogeneity, and material stability because the SB consists only of inorganic soils. To ensure the long-term durability of the SB cutoff walls, various aspects such as performance of constructed barriers and post-construction maintenance need to be clarified. For a decade or more, the authors have studied factors affecting hydraulic conductivity (k) of SB, self-recovery in the k values against occurrence of hydraulic fractures, the feasibility of on-site quality assessment using the piezocone test, and the role of chemical diffusion in transport of mobile substances through SB cutoff walls. These approaches revealed that the k of the SB is affected by chemicals in groundwater and the content of bentonite powder. The piezocone test seems to be a suitable tool for detection of a lean-mix part in the cutoff walls and for measurement of on-site k values. The effect of chemical diffusion on transport of mobile substances is not negligible because the relative concentration of a chemical substance attained 0.26 after 50 years only by the chemical diffusion when not considering adsorption onto soil particles.
Soil–Bentonite Cutoff Walls for Geoenvironmental Containment
Abstract Cutoff walls used for prevention of the migration of mobile contaminants in the aquifer must maintain high barrier performance for a long period. Soil–bentonite (SB), which is a mixture of in situ soil and bentonite, has many advantages as a barrier material such as appropriate deformability, homogeneity, and material stability because the SB consists only of inorganic soils. To ensure the long-term durability of the SB cutoff walls, various aspects such as performance of constructed barriers and post-construction maintenance need to be clarified. For a decade or more, the authors have studied factors affecting hydraulic conductivity (k) of SB, self-recovery in the k values against occurrence of hydraulic fractures, the feasibility of on-site quality assessment using the piezocone test, and the role of chemical diffusion in transport of mobile substances through SB cutoff walls. These approaches revealed that the k of the SB is affected by chemicals in groundwater and the content of bentonite powder. The piezocone test seems to be a suitable tool for detection of a lean-mix part in the cutoff walls and for measurement of on-site k values. The effect of chemical diffusion on transport of mobile substances is not negligible because the relative concentration of a chemical substance attained 0.26 after 50 years only by the chemical diffusion when not considering adsorption onto soil particles.
Soil–Bentonite Cutoff Walls for Geoenvironmental Containment
Katsumi, Takeshi (author) / Takai, Atsushi (author) / Inui, Toru (author)
2018-01-01
17 pages
Article/Chapter (Book)
Electronic Resource
English
Soil-Bentonite Cutoff Walls for Geoenvironmental Containment
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