Liquefaction characteristics of gap-graded gravelly soils in K0 condition

• A stack-ring-reinforced membrane is used to perform K0-CDSS tests.
• The skeleton void ratio is a better packing index than the void ratio for gap-graded gravelly soils.
• The gravel content has only slight effect on CRRs of gravelly sands under a given esk.
• Gravel content correction should be used to evaluate CRRs of gravelly sands.
• A different CRR–Vs1 curve should be used to evaluate the CRRs of sandy gravels.

A series of undrained cyclic direct simple shear tests, which used a soil container with a membrane reinforced with stack rings to maintain the K0 condition and integrated bender elements for shear wave velocity measurement, were performed to study the liquefaction characteristics of gap-graded gravelly soils with no fines content. The intergrain state concept was employed to categorize gap-graded sand–gravel mixtures as sand-like, gravel-like, and in-transition soils, which show different liquefaction characteristics. The testing results reveal that a linear relationship exists between the shear wave velocity and the minor fraction content for sand–gravel mixtures at a given skeleton void ratio of the major fraction particles. For gap-graded gravelly sand, the gravel content has a small effect on the liquefaction resistance, and the cyclic resistance ratio (CRR) of gap-graded gravelly sands can be evaluated using current techniques for sands with gravel content corrections. In addition, the results indicate that the current shear wave velocity (Vs) based correlation underestimates the liquefaction resistance for Vs values less than 160 m/s, and different correlations should be proposed for sand-like and gravel-like gravelly soils. Preliminary modifications to the correlations used in current evaluations of liquefaction resistance have thus been proposed.