CALIBRATION CHAMBER STUDIES OF PIEZOCONE TEST IN COHESIVE SOILS

Results of miniature piezocone penetration tests (PCPT) on cohesive so il specimens in a calibration chamber system are presented. The influe nce of soil type, stress history, penetration boundary conditions, and fitter locations on PCPT data are investigated. An increase in the st rength of the soil around the cone penetrometer is observed when penet ration is resumed after a dissipation test. The penetration depth requ ired to attain a steady excess pore pressure value at the tip of the c one is influenced by the overconsolidation ratio and the lateral stres s coefficient. The empirical values of the cone factor and the pore pr essure factor are found to be strongly influenced by the lateral stres s and the plasticity index. The tip resistance measured during the min iature quasi-static friction cone penetration tests (QCPT) are consist ently lower than the values obtained from the PCPT. Interpretation of the dissipation results to evaluate the radial coefficient of consolid ation should be based on the initial dissipation values of the excess pore pressure, and not the penetration pore pressure.