Instrumented Dynamic Cone Penetrometer Corrected with Transferred Energy into a Cone Tip: A Laboratory Study

Abstract

For the site investigation of stiff soils, dynamic penetration testing, such as standard penetration testing (SPT) and dynamic cone penetration testing (DCP), has been performed. The dynamic cone tip responses, however, have not yet been evaluated. The objective of this study is the development and application of an instrumented dynamic cone penetrometer (IDCP) to evaluate the dynamic cone tip responses by considering the energy transferred into the cone tip. As the preliminary study on the development of the IDCP, the energy losses caused by the rod connection are experimentally estimated and numerically analyzed by considering the transmission and reflection coefficients. Strain gauges and accelerometers are installed in the cone tip and rod head of the IDCP to detect dynamic responses during penetration. Design concerns include the shape of the IDCP, the installation of strain gauges and accelerometers, and the mechanical resistance calibration. The developed IDCP was driven into compacted weathered soils in the chamber to measure the dynamic responses at the rod head and cone tip. From the measured responses, the energy transferred into the rod head and the cone tip was calculated. The experimental and numerical energy loss studies show that the energy loss increases with an increase in the number of rod connections. The penetration-test results show that the energy transferred into the cone tip is significantly smaller than that transferred into the rod head. Furthermore, the energy corrected dynamic responses at the cone tip clearly detected soil layers. This study suggests that energy losses caused by rod connections should be considered and that the IDCP may be a useful tool for the characterization of stiff soils.