Excess pore pressure generation in sand under non-uniform cyclic strain triaxial testing

Two sets of strain-controlled cyclic triaxial tests were conducted to investigate soil liquefaction of clean sands. The first set involved conventional uniform strain amplitude cyclic tests, while the second set examined non-uniform strain amplitude cyclic tests. Comparisons were made between the two sets of results with respect to the generation of excess pore pressure and relationship between strain amplitude and stress path. In the case of uniform strain-controlled cyclic tests, larger strain amplitude produced more rapid generation of excess pore pressure. Conversely, for non-uniform strain-controlled tests, larger strain amplitudes may generate lower excess pore pressure instead. Such counter-intuitive phenomenon has design implications if irregular earthquake loadings in the field are incorrectly represented as equivalent uniform loading in the laboratory. Details are described in this paper.