The Israeli Experience with the Regular and Extended Dynamic Cone Penetrometer for Pavement and Subsoil-Strength Evaluation

摘要

One of the Israeli modification in the dynamic cone penetrometer (DCP) apparatus is the extension of the length of the standard penetrating rod to a total of about 2.0 meters by screwing on an additional 1.0-meter rod after the original rod has completely penetrated the pavement or subgrade. Such a procedure is required when the strength profile is significant at depths exceeding 1.0 meter or when the total thickness of the pavement layers, including the relevant subgrade layers, exceeds the length of the standard penetrating rod. Through comparative in-situ testing, it was found that a 20% deduction should be applied for this testing procedure to the CBR values calculated from the in-situ DCP results, both for clayey and for granular subsoils, when the standard CBR-DCP equation is used. Similarly, a 10% reduction should be applied to the 1.5-meter penetration rod results. These findings were also qualitatively verified by examining the change in the dynamic efficiency factor for the two penetrating rods. Additionally, a corrective equation is suggested when the penetration is not performed vertically in order to isolate the skin friction that develops along the penetrating rod and that has significant effects on the DCP values. Finally, the standard CBR-DCP relationship is validated again for both CH and CL clays, thus eliminating the need for specific additional relationships for these materials.