Cone penetration tests under simulated field conditions

Abstract

Cone penetration tests (CPT) performed in a conventional cavity-wall calibration chamber are inevitably affected by boundary conditions. The authors have developed an axisymmetric field simulator whereby CPT calibration tests can be conducted under substantially reduced boundary effects. The simulator consists of a cylindrical, physical sand specimen and a stack of expandable rings to simulate the soil from beyond the physical boundary. A series of CPT calibration tests has been performed in a clean, uniformly graded quartz sand using this simulator system. For a given relative density, the cone tip resistance (q(c)) was found to be most closely related to mean normal stress. The horizontal stress at the physical boundary increased during CPT under simulated field conditions. This increased horizontal stress had a much more significant and consistent effect on q(c) than the initial horizontal stress existing in the soil prior to CPT. The paper describes the results of CPT in the simulator, and discusses implications for the performance of CPT in a chamber and their interpretation.