RESISTIVITY CONE PENETRATION TEST TECHNIQUE AND DATA INTERPRETATION

As a new kind of in-situ testing techniquet,he resistivity cone penetration test(RCPT),which widely has been used in the foreign countries because of its advantages,can measure tip resistance,casing friction,pore pressure and soil resistivity simultaneously in the field.Soil resistivity can represent its geotechnical properties well,such as characteristics of soil contamination and ground liquefaction potential.Therefore,the RCPT technique has been extensively used in both the environmental and geotechnical fields,especially in contaminant site investigations.Firstly,a review on the theory of soil resistivity and factors affecting resistivity is presented in brief.Measuring equipment and operation principle of the Vertek-Hogentogler RCPT system are introduced.Based on some literatures and field test results with the RCPT at two different sites in China,the relationships between resistivity measured from RCPT and soil lithology,cone bearing,and other characteristic indexes are analyzed.The presented test data show that the resistivity measurement can be indicative of soil lithology and groundwater regimes.The results of two RCPT testing sites illustrate that there is a better relationship between friction ratio and resistivity.The peaks or increases in friction ratio are generally matched with troughs or decreases in the resistivity.The test data indicate that the electrical resistivity decreases with increasing liquid limit and plasticity index;and the Atterberg limits of clay tend to be a correlative function of the electrical resistivity,with the electrical resistivity being a slightly better indicator of liquid limit than that of plasticity index.Although there are few data relating electrical resistivity to specific geotechnical parameters,the presented testing results show that the RCPT is a practical tool for evaluating engineering behaviors and predicting geotechnical properties of soils due to their speed,economy,and reliability.Finallyt,he problems and the applied prospects of RCPT in site investigations are discussed.