Scale-Corrected Cone Resistance in Bimodal Sands across Chamber Boundary Conditions

Abstract

Cone penetration testing is a fundamental in-situ geotechnical investigation method used extensively for site characterization and the determination of soil engineering properties. The interpretation of cone penetration resistance in granular materials is traditionally based on empirical correlations developed from large-scale calibration chamber tests. However, standard interpretations often fail to account for the complex mechanical behavior of bimodal sands, which possess distinct particle size distributions that fundamentally alter stress transmission and shear zone development. Furthermore, calibration chamber size and boundary conditions impose artificial physical constraints that cause measured cone resistance to deviate significantly from true field conditions. This paper presents a comprehensive investigation into the scale-corrected cone resistance of bimodal sands under various chamber boundary conditions. A rigorous experimental program utilizing a custom-designed macro-calibration chamber was executed alongside advanced analytical modeling to decouple the influences of bimodal particle interlocking and boundary proximity. We derived a novel scale-correction framework that mathematically integrates boundary stress-strain constraints with the specific micromechanical attributes of gap-graded granular assemblies. The results demonstrate that bimodal sands exhibit an amplified sensitivity to boundary rigidity, necessitating a non-linear scale correction protocol. The proposed analytical framework bridges the gap between laboratory calibration and field performance, offering a robust tool for practicing geotechnical engineers.