On the issue of using foreign soil classification charts according to CPTU data

The main data on piezostatic soil sensing (“Piezocone Penetration Testing — CPTU”), which allows, in addition to the soil resistance to probing, to determine the pore pressure in the soil adjacent to the probe, are considered. Focus is done on the pore pressure measured between the cone and the friction coupling u2. The normalized probing parameters (qt, Qt, Bq, Fr) implicitly account the pore pressure u2 are given, Foreign experts often use these parameters when drawing up map-diagrams to identify soil varieties (“qt–Bq”, “qt–Fr”, “Qt–Fr”, “Qt–Bq”, “Qt(1–Bq)–Fr”, etc.). Recently, many of the foreign map-diagrams, starts to be used in Russian geotechnical practice, including compiling computer programs for processing sensing data without conducting comparative studies. The article presents the experimental results to verify possibility of using foreign “qt–Rf” and “qt–Bq” card schemes proposed by P.K. Robertson et. al. The comparative experimental studies shown impossibility to use these foreign maps-schemes for soil varieties identification and determination on the territory of Russia during engineering and geological surveys due to their unreliability.