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CPT, SPT and DP test Interpretation
The INSITU program interprets statical and dynamical geotechnical in situ tests.
In order to interpret the SPT tests, the program utilises the main correlations that are normally used to determine the geotechnical parameters of a soil.
One should enter the geometrical and geotechnical parameters pertaining to the stratigraphy surveyed trough drilling and the number of blows relative to each test; some corrective parameters can be entered that enable one to limit the perturbations in the interpretation of the data caused by the way the test is performed and the type of instrument that is used.
Based on this simple information, the program determines the relative density, the friction angle, the effective vertical and total stress, the confined modulus, Young's modulus, the upper limits of the settlement/admissible load ratio, the point resistance, the dynamic shear modulus and the cyclical stress of the terrain traversed, when possible using different calculation methods to permit comparison of the results.
When interpreting the CPT test results, the program divides, as normal practise, granular terrains with a prevalence of sand from cohesive terrains made up mostly of clay.
For granular terrains, it is able to determine (from the data that has been entered) the friction angle, the drained compressibility and the relative density, while for cohesive terrains it evaluates the shear resistance in undrained conditions, compressibility, sensitivity and the degree of over-consolidation.
For the interpretation of this test the data required are, yet again, extremely simple: the classification of the terrain that has to be used, the measured test values and any correction factors that prove necessary to limit perturbations in the interpretation of the data.
With the DP test interpretation, which is mainly used in granular terrains and to localise resistant strata, the program supplies all the information previously mentioned for the SPT test.
The INSITU program can be adapted to any measurement instrument.