Some Factors Affecting In Situ Measurement Using the Cambridge Self-Boring Pressuremeter

Research presented in this paper was conducted to assess the influence of environmental and physical factors on measurements made with the self-boring pressuremeter (SBPM). It was found that temperature changes during deployment and long-term instrument calibration drift can result in misinterpretation of in situ soil properties. It was also observed that neglecting to consider the sequential order of strain arm lift-off and radial confinement in both membrane calibration and data reduction can have an effect on interpretation of horizontal stresses, particularly in soft clays. Control experiments were conducted to quantify the effect of these factors. Based on the results of these experiments, a method for assessing excess pore pressure at the beginning of a test using the standard Cambridge SBPM transducers was developed. This method incorporates findings from temperature behavior tests. In addition, a modified method of membrane stiffness correction is proposed which includes consideration of sequential order of lift-off and confinement effects