Role of the coefficient of uniformity on the California bearing ratio, penetration resistance, and small strain stiffness of coarse arctic soils

For seasonally frozen-thawed Arctic soils, soil properties are significantly affected by the particle size distribution. The objective of this study is to study the role of the coefficient of uniformity (C-u) on the California bearing ratio (CBR), strength, and stiffness. Six poorly-graded sand (SP) samples with various C-u are collected from a depth from 20 cm to 120 cm in the active layer. The amounts of the organic matter range from 0.22% to 2.11%. Specimens are prepared with each natural water content into a CBR mold, and the CBR, mini-cone tip resistance (q(u)), and shear wave velocity (V-s) are measured. Field tests using an instrumented dynamic cone penetrometer (IDCP), which can gather force and acceleration signals at the cone tip, are performed. The IDCP index (IDCPI), energy-corrected DCPI (EDCPI), and dynamic cone resistance (q(d)) are estimated during penetration. Test results show that the CBR,q(c,) q(d) ,V-s, and maximum shear modulus (G(max)) decrease with increasing C-u value. The IDCPI and EDCPI increase according to the C-u value. Thus, CBR is inversely proportional to the DCPI, and linearly proportional to the q(d) and G(max). This study demonstrates that the CBR, strength, and stiffness of Arctic soils are affected by the particle size distribution because the main skeleton comprised of large particles can be disrupted by small particles.