The CPT and CPTu tests are both static tests; however, they differ in the type of equipment used and the accuracy of the data obtained.
CPT:
CPT or CPTm tests are performed by pushing a static penetrometer, which allows for the measurement of Qc and Fs values using a load cell during the insertion of the Begemann cone into the ground. The depth is determined by the operator. Although this data, it has a significant issue related to the friction generated by the inner rods if these are not regularly cleaned and lubricated.
CPTu:
CPTu tests are characterized by the use of electronic instrumentation, which is significantly more precise and reliable.
The test is always performed by pushing a static penetrometer, but the sensor readings are taken directly inside the piezocone, thus reducing the margin of error. In addition, this is the only test that allows for the continuous and simultaneous measurement of all values along the entire vertical starting from the ground surface.
Unlike piezocone also allows for the measurement of pore pressure (U), inclination (Tilt°), and temperature (°C), in addition to the values of Qc and Fs.
The depth is determined using an encoder, with a resolution of 1 cm.
All data are then recorded with high precision by a data logger, without the need to use a computer or paper to note the readings taken.
In summary, both tests are extremely valid; however, thanks to modern technologies, the results of CPTu tests are clearly superior in terms of both repeatability and reliability compared to mechanical static tests.