To quantify the influence of basic physical properties and cyclic loading conditions on the liquefaction properties of sandy soils, this study uses a combination of physical experiments and numerical simulations to investigate the liquefaction behavior of saturated sandy soils under undrained conditions and their relationship to physical property parameters and external loads. A numerical model with discrete elements was created based on cyclic triaxial tests. A numerical study and predictive analysis of liquefaction of common bulk samples were carried out in conjunction with a PSO-BP neural network prediction model. Using a multivariate analysis of variance and a random forest model, the complexity of the influence of physical parameters and external loads on soil liquefaction was investigated. Quantitative results indicate that particle size distribution, external loads and effective internal friction angle have a significant influence on the liquefaction of saturated sandy soils. In summary, the results of this study provide new insights into understanding the liquefaction behavior of sandy soils.

Accurate prediction of excess pore water pressure (EPWP) generation in saturated sandy soils remains one of the most challenging issues in sandy site responses to strong earthquakes and extreme marine environments. This paper presents experimental results of undrained and drained multidirectional cyclic hollow cylinder (MCHC) tests on saturated coral sandy soils under various cyclic loadings. The results show that threshold generalized shear strain gamma ga,th, below which EPWP and volumetric strain can be neglected, is an inherent property depending only on the soil type and initial state. Furthermore, there exists a virtually unique form of relationships between the generalized shear strain amplitude (gamma ga) and the cumulative dissipated energy per unit volume of soil (Wc) at different relative density (Dr), irrespective of drainage conditions and cyclic loading conditions. These findings highlight the fundamental mechanism for cyclic deformation behavior and the uniqueness of correlations among rup (peak EPWP ratio), epsilon vp (peak volumetric strain), and gamma ga of saturated sandy soil at the similar Dr, regardless of cyclic loading conditions. Based on these findings, a novel unified model of gamma ga-based cyclic shear-volume coupling and EPWP generation is established, which is independent of cyclic loading conditions over a wide loading frequency range. Then the applicability of the proposed model is validated by the experimental data of the same tested coral sandy soil and siliceous Ottawa sand, as well as the data of siliceous fine sands in previous work. It is found that the proposed model surpasses the existing strain- and stress-based models in accurately predicting EPWP generation under complex cyclic loadings, which can offer new insights into the mechanisms of the EPWP generation in saturated sandy soils.