Experimental Studies on Hydraulic Barrier Performance and Quality Control of SBM Cut-Off Wall: Applicability of Piezocone Test

Abstract

In-situ containment technique using soil-bentonite mixture (SBM) cut-off walls is a valid method against contaminants in subsurface soil and/or groundwater. Since the contaminants must be completely contained to prevent their migration into the aquifer, cut-off walls must be constructed with both low hydraulic conductivity and high homogeneity. However, since SBM maintains its softness even after its construction, it is technically and economically difficult to collect high-quality solid core samples to assess the homogeneity of constructed SBM cut-off walls. Therefore, it is important to develop in-situ quality control (QC) and quality assurance (QA) methods for SBM cutoff walls. In this research, consolidation tests and hydraulic conductivity tests were conducted to assess the hydraulic conductivity values of SBM with various bentonite powder contents. A piezocone penetration test (CPTU) using a large-scale soil tank was conducted to evaluate the applicability of CPTU to detect heterogeneities in SBM wall. Hydraulic conductivity values were found to have a clear relationship with bentonite contents of SBM in hydraulic conductivity tests; and physical property values obtained from CPTU changed according to the SBM composition, meaning that CPTU may be applied as a QC/QA method of constructed SBM cut-off walls.