Developments in gravelly soil liquefaction and dynamic behavior

This paper presents a critical look at gravelly soil liquefaction and dynamic behavior from the laboratory perspective: (1) Undrained cyclic triaxial testing may reliably predict cyclic behavior if membrane compliance is eliminated. Membrane compliance mitigation procedures are briefly described. (2) Loose, uniformly-graded gravel may have similar cyclic strength as sand. Differences in stress-strain behavior, axial strain, and pore pressure ratio are illustrated for soils with different gravel contents. Scalping may be effective but also may lead to underestimating liquefaction potential. (3) Shear moduli and damping ratios are presented for gravelly soils. Shear modulus, normalized shear modulus, and damping curves are developed to define their variation with shear strain from a compilation of studies. (4) Finally, preliminary results from large-scale pressure chamber tests on gravel are discussed. Data will be available from SPT tests, shear wave velocity measurements, and cone penetration tests performed on gravel specimens in the pressure chamber.