Pore Pressure Build-Up in Aggregate-Clay Mixtures under Cyclic Loading

Undrained behavior of aggregate-clay mixtures in its natural or compacted state, which is used as the core of embankment dams or liner of waste disposal systems, has great importance for geotechnical engineers. Previous studies have shown that excess pore water pressure plays an important role when dealing with cyclic/dynamic behavior of aggregate-clay mixtures. An extensive testing program was conducted on compacted sand-clay mixtures to investigate effects of aggregates on the cyclic behavior of the mixtures under strain- and stress-controlled cyclic loads utilizing triaxial and torsional shear equipment. Clay content was varied from 100 to 40% by volume in tested specimens. Isotropically and anisotropically consolidated specimens were tested under vertical effective stresses of 100 and500 kPa. The aim of the various loading conditions and numerous experiments was to investigate cyclic pore pressure build-up in the mixtures, and developing a pore pressure model based on dissipated energy. The main advantage of the model is that it can capture opposite trend of pore pressure build-up with aggregate content in strain-, and stress-controlled loading. The model is then verified with cyclic triaxial tests on ceramic beads-clay mixtures.