A Non-Destructive Monitoring System for QA/QC of Cement-Bentonite Cut-off Walls-Paper

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The study evaluates electrical resistivity monitoring as a non-destructive quality assurance method for cement–bentonite (CB) cut-off walls. Conventional coring tests strength and permeability only at set curing ages, often around 91 days, delaying identification of potential problems.<br /><br />Researchers installed two-electrode resistivity sensors in a 0.8 m-wide laboratory model and at two sections of a field wall. Measurements were taken at multiple depths over approximately 100 days. Field core samples were also tested for unconfined compressive strength (UCS) and permeability after 91 days.<br /><br />Laboratory and field measurements showed similar patterns: resistivity initially decreased or remained low, then increased after about one day of curing. Field readings were initially fairly uniform with depth, but later varied, particularly near the ground surface and water table, where drying and rewetting may affect moisture content. Resistivity generally stabilized after roughly 35–47 days, potentially indicating that much of the CB’s microstructural development had occurred.<br /><br />Field results showed preliminary positive associations between resistivity and UCS, and a possible association between resistivity and permeability. However, the available data—especially permeability results—are insufficient for reliable predictive relationships, and UCS values varied considerably at similar resistivity levels.<br /><br />The findings support the feasibility of continuous, in-situ resistivity monitoring as an early indicator of CB wall development and a potential complement to destructive coring. More data are needed to establish dependable correlations and predictions of long-term strength and permeability.

Keywords

electrical resistivity monitoring

cement-bentonite cut-off walls

non-destructive quality assurance

continuous in-situ monitoring

unconfined compressive strength

permeability testing

laboratory model

field wall measurements

microstructural development

quality control