A century later: a bearing-capacity framework to extract Mohr-Coulomb parameters from penetration tests

This study reformulates classical bearing-capacity theory into a depth-resolved framework for extracting apparent Mohr–Coulomb parameters from quasi-static flat-punch penetration tests. The measured force–depth response is converted to the mean contact stress q (z) and analysed as a function of depth, with cohesive, surcharge, and unit-weight contributions. Under homogeneous, axisymmetric conditions, the internal friction angle and cohesion c are obtained from the slope and intercept of the quasi-steady q (z) relation. Applied to an inert montmorillonite–glycerin reference material, the method yielded reproducible results across punch diameters D=20 – 40~mm, giving ₏₄₍ ₄. ₈^ and c₏₄₍ ₀. ₈₅~₊₏₀. Independent vane tests gave cₕ₀₍₄ 0. 70~kPa, and direct shear box tests yielded ₃ₒ₁ 4. 45^ and c₃ₒ₁ 1. 16~kPa. The friction angles from penetration and DSB testing were consistent, while the cohesion values differed in the ordering expected from their respective interface and deformation conditions. Within the quasi-static, low-stress regime examined here, the penetration-based approach provides an efficient method for quantifying apparent Mohr–Coulomb parameters of soft cohesive–frictional materials.