Grading model for fine soil classification using cone penetration testing

The grading of fine-grained soils is one of fundamental properties, and studying how to obtain this information using in situ methods is essential. However, existing cone penetration tests (CPT) lack a direct approach for measuring particle size and its content. To address that issue, the relationship between cone tip resistance ( q c ) and sleeve friction resistance ( f s ) with these curve parameters (CPs) was established using in situ CPT. Finally, an expression for the grading curves based on the results obtained from the CPT was presented. The main conclusions are as follows: (1) An exponential relationship exists between fine content and the variation pattern of fitting parameters used to characterize the grading curve, depending on the soil layer type. (2) The depth-corrected CPs are related to the q c and f s by a power function, revealing a link between the CPT and grading curve; (3) by utilizing global CPT and soil layer data, the boundaries of CPs were precisely defined, and the content of different particle sizes across various soil layers was predicted. The applicability of the fitting results was then analyzed for both homogeneous fine-grained soils and complex soil type.