Experimental procedure for checking the saturation degree of piezocone tips

A correct measurement of the water pore pressure is essential to obtain reliable CPT results. Although this has always been a major concern, it still remains a possible relevant source of error in common engineering practice. In addition to usual reasons, such as malfunctioning of the equipment, its poor calibration and/or maintenance, a lack of complete saturation of the piezocone tip can play a major role. In fact, a correct and timely pore pressure measurement relies entirely on the full saturation of the pore pressure system. The variety of saturation fluids and methods that is encountered in practice is a clear evidence of the still existing uncertainties on the most suitable procedure. Furthermore, unless the saturation process is explicitly detailed, its choice is typically left to the contractor and the measurement quality can only be established a posteriori, after the test has been completed. This paper describes a novel experimental equipment that enables quantifying the degree of saturation of the piezocone tip prior to testing. The methodology proposed is inspired to the B-value check, which is routinely used in geotechnical laboratory testing to assess the degree of saturation, e.g. prior to triaxial testing. In addition, it could also be applied after a test, so that it would be possible to assess whether saturation was retained while testing. This promising approach, when extended to different saturation procedures and validated by engineering practice, has the potential to become a relevant benchmark for reliable CPT testing.