L'abbiamo già scritto tempo fa ma forse è deifficiel ritrovarlo.
Alcuni ricercatori della Svizzera Italiana hanno svolto delle analisi comparative tra sondaggio e prove, DPSH, CPT e DPL.
Experimental In Situ Test SitesGianni ToglianiSenior Geologist ConsultantGiorgio BeatrizottiSenior Geologist, IST-SUPSI (Institute of Earth Science – University of Applied Science of Southern Switzerland)
Keywords: CPTU, CPT, DMT, DPL/M, DPSH.
ABSTRACT: The IST-SUPSI has promoted the construction of two experimental test sites in the southern part of Switzerland in order to compare the results of the most commonly used in situ tests. The Gordola site is characterized by alluvial and deltaic deposits while the Stabio site presents alternating fluvial and lacustrine deposits, both recent and of glacial origin. Even though the program is still in its initial phases and the results obtained remain to be confirmed and eventually adapted to the various regional situations, the developments of the DPSH with casing seem promising, especially for lithological and geotechnical interpretation of the soils encountered. Hopefully this will encourage greater use. Similar considerations can be made for a proposed non-conventional SPT.
...............
6 CONCLUSIONS
The results obtained at Gordola and Stabio sites confirm the necessity to execute in situ test as CPTU and DMT, if one wants to obtain a reliable stratigraphic and geotechnical characterization of the fine grained soils.
The most important lesson learned however, is the capacity of DPSH with cased rods to provide, elaborating the dynamic penetration resistance of both, qc and fs equivalent values comparable with that measured by CPTU.
This means that everywhere we have coarse soils with variable amount of gravel, able to obstruct or prevent the execution of CPTU and DMT, DPSH with casings become the recommended equipment (compared to CPT also has a much more extensive application field).
Assuming that each investigation requires at least a borehole with continuous core recovery not only to obtain undisturbed samples or to place a piezometer, but especially to have an interpretation key for all in situ tests, the use in coarse soils of the non-traditional proposed SPT, once more allow to obtain in a simple, rapid and inexpensive manner, elaborated reliable values of qc, exploitable for a corrected geotechnical characterization.
Concerning the DPL/M we suggest using them (better with casings), only in cases of impossible access for others equipment and when the investigation does not exceed depths of 10-12 m.
Finally, the common habit of passing from DPL/M to DPSH by the application of a simple correlation coefficient is unadvisable even modifying it with the soil characteristics encountered.
