Volume 33, Issue 2 (March 2010)
Interpretation of Resistivity Piezocone Tests in a Contaminated Municipal Solid Waste Disposal Site
A resistivity piezocone (RCPTU–resistivity cone penetration test with pore pressure measurement) and groundwater and soil samplers were used to detect contamination from a landfill for urban solid waste located in the state of São Paulo in southeastern Brazil. Background resistivity values were obtained in the laboratory using undisturbed soil samples. The strong influence of clay minerals common in tropical soils made it difficult to interpret the tests and to differentiate potentially contaminated zones from changes in soil type. A local correlation between fines content and the soil behavior index (Ic) of the various collected soils allowed the RCPTU tests to be interpreted to identify the contaminated regions of the aquifer. These results showed excellent repeatability and allowed for a detailed stratigraphic analysis of the highly heterogeneous profiles. Electrical resistivity measurements have proven to be an interesting resource to help detect contaminated soils, thus improving the quality and efficiency of geoenvironmental site investigations using integrated direct and indirect techniques. The interpretation of resistivity piezocone tests for the study site is not straightforward as it is in sedimentary sands since soil genesis affects soil behavior and soil and water sampling is required to support interpretation.