Practical guidelines for connecting critical states, strengths and dilatancies of scalped and natural soils

Soil laboratory testing often requires the removal of oversized particles to satisfy specimen-size limitations, resulting in a modified particle size distribution (PSD) that can significantly influence the measured shear strength and volume-change response. This study presents a physically based framework, grounded in fractal theory, for relating the critical state line (CSL) of a scalped soil to that of the original field material. The approach quantifies the vertical shift of the CSL in the ln e – ln p ′ space induced by PSD truncation, while preserving the intrinsic critical state parameters M and λ . This provides a practical tool for estimating the CSL of field-scale materials from laboratory-scaled specimens. Validation against multiple published datasets demonstrates that the predicted CSLs closely match experimental trends, and remain consistent with the observed volume-change behaviour and peak shear strength measurements. The findings show that conventional laboratory results on scalped specimens may substantially misrepresent the behaviour of the in-situ material unless properly corrected. The proposed framework therefore enables more reliable interpretation of strength and state-parameter-dependent behaviour in coarse granular soils where full-scale testing is not feasible.