Undrained cyclic failure mechanisms and resistance of saturated sand-gravel mixtures

There are conflicting versions of influences of different factors on cyclic resistance of sand-gravel mixtures. Considering four main factors, gravel content, effective lateral confining stress, relative density and consolidation stress ratio, a series of cyclic triaxial tests were performed on the sand-gravel mixtures with 10 groups of gravel contents. The test results and findings are summarized as follows: (1) There are two failure mechanisms of the sand-gravel mixtures under different test conditions, i.e., cyclic liquefaction and cyclic failure; (2) The excess pore pressure of a 100% and the accumulated axial strain of a 5% are adopted as the criterion for the cyclic liquefaction and the cyclic failure of the specimens, respectively; (3) An index of the sand-gravel skeleton void ratio () is employed to represent the packing condition of skeleton particles and filler particles in the sand-gravel mixtures; (4) The mean correlation representing the exponential relationship between the cyclic resistance ratio (CRR) causing cyclic liquefaction or cyclic failure at the presupposed number of cycles and the of sand-gravel mixtures is derived.