Enter Nblows/15 in sequence relative to the working depth. The program performs the necessary processing automatically, while the definition of the depth of the layers and the choice of the lithology type (cohesive or cohesionless) is left to the user.
If is not selected the option "Automatic unit weight estimate" the unit weight value must be entered by the user, otherwise, choosing the type of lithology, will be estimated automatically by the program.
The existing correlations in the literature were initially developed for standard open-ended SPT tests and not for closed-ended ones.
Furthermore, the AGI 1977 standards state that the sampler can be replaced by a closed tip in the case of granular soils where the particles have a diameter larger than that of the sampler tube (approximately 4 cm). The conical tip has dimensions and an angle defined by the standards.
For operational reasons, the standard open-ended sampler must often be replaced with the conical tip in coarse-grained soils; in principle, the results obtainable with the standard open-ended sampler in terms of blow count/30 cm may not be entirely comparable with those achieved using the conical tip. Therefore, the latter might not be directly usable for interpretation using the empirical literature correlations developed for the SPT test with a standard open-ended sampler. In any case, interpretations of SPT tests with a conical tip are generally performed assuming that, overall, a good correspondence exists between the results of closed-tip tests and those of standard open-ended sampler tests.
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