Prediction of Excess Pore Water Pressure Generation in Sand–Silt Mixtures During Cyclic Loading: A Dissipated Energy-Based Model

This study investigates the effect of non-plastic fines content of sand–silt mixtures on excess pore water pressure generation using an energy-based approach. For this purpose, an experimental program was designed and conducted on mixtures of Firoozkuh sand No. 161 and Firoozkuh silt. A total of 35 undrained strain-controlled cyclic triaxial tests were performed on the reconstituted specimens of sand–silt mixtures, with a wide range of effective parameters such as relative density, effective confining stress, and fines content. Also, to present a more generalized and precise model, 37 undrained cyclic tests were collected from previous studies. Then, using nonlinear regression analysis and the results of these 72 tests, a model, relating residual excess pore water pressure ratio ( \({r}_{u}\) $r_u$ ) to the ratio of dissipated energy to capacity energy ( \(W/{W}_{liq}\) $W/W_{\mathit{liq}}$ ), is proposed. The results indicated that initial effective confining stress has a negligible effect on the \(r_{u} - W/W_{liq}\) $r_u-W/W_{\mathit{liq}}$ trend and so, the calibration parameter of the model only depends on the relative density and fines content. Convincingly, the accuracy of the proposed model was verified using the results of a series of centrifuge tests, reported by others, and the recorded data of wildlife downhole array site during the Superstition Hills 1987 earthquake. The proposed model is practical, applicable to various sands and sand–silt mixtures with nonplastic fines contents, and able to be calibrated using convenient parameters (i.e., relative density and fines content). Finally, the model can be easily implemented in site response analysis for energy-based liquefaction potential evaluation.