Systems for evaluating the correlation between soil cone penetrometer resistance and shear strength

The aim of this research is to study possible correlations between soil compaction (and related soil cone penetrometer resistance measurements) and shear strength normal to the field plane, required to cut the soil with a subsoiler. A measurement system for sensing the soil cone penetrometer resistance was built mounting, on a frame fixed to the front part of a tractor, a rod and a penetration cone with a load cell. A load cell, mounted on the tractor drawbar, pulling a subsoiler, allowed to measure the shear strength normal to the field plane, required to cut the soil. Both load cells were connected, through a display, to a portable computer, where a software was used for acquiring the data of both parameters. The measured data was geo-referenced by using a DGPS mobile receiver, mounted on the tractor. After several reliability laboratory tests, the two systems were experimented on a field of inland Sicily. The results did not show any correlation between the two studied parameters. Therefore, further tests with different soil types and conditions need to be carried out, in order to find out if the total lack of correlation was due to the particular soil conditions encountered during the tests.