The Resistivity Piezocone (RCPTu) as a Tool of High Resolution Site Assessment and Hydrostratigraph Profile
The development of the conceptual site model (CSM) is a key step in studies of contaminated lands.
In Brazilian studies, all the investigation is based on the traditional approach: monitoring wells installation and direct push soil samples. More than this, the drilling for monitoring wells installation is the only way to establish the stratigraphic profile and develop the CSM.
The modern approach to establish a CSM with an appropriate degree of uncertainty is the investigation of high resolution (Quinam 2012, Ahlers 2012, St. Germain 2012, Singer & Fiacco 2010). One of the tools available to develop the hydrostratigraphy profile is cone penetration test (CPTU) (Kilembeck 2012; Welty 2012). It is possible to attach several sensors in this equipment, including an electrical conductivity sensor. This set name "Resistivity piezocone test" (RCPTu).
The use of this additional sensor can provide greater accuracy in determining the profile stratigraphic when correlating the results obtained by the other CPTU sensors: stress tip (qc), side friction (fs) and pore pressure (u) (Schulmeister et al 2003, De Mio 2004).
In the presented study, in Bauru-SP/Brazil, the CSM was developed using Direct Push Soil Samples (DPT), RCPTu tests and monitoring wells installation. The results showed that the correlation between various methods of CSMs development is very good and that the resistivity sensor improves the profile interpretation, when this additional information (electric resistivity) was evaluated in conjunction with other measurements performed in the test CPTU.
The RCPTU can be a useful and powerful tool for the development of the conceptual model and can be part of a high resolution investigation, because it has greater precision than DPT, it is independent of the operator, can obtain information in regions where the DPT cannot, as much below water level, and is much faster than DPT.