Identification Method of Soil Liquefaction Based on Thixotropic-Induced Excess Pore Pressure Fluid Model

Based on the thixotropic fluid theory, this paper presents a method for identifying soil liquefaction under earthquake with consideration of pore pressure thixotropy. By introducing the concept of “thixotropic-induced excess pore pressure”, the process of pore water pressure accumulation and structural state evolution of saturated sand under cyclic loading is described as a thixotropy behavior with the characteristics of internal structure destruction and reconstruction, and a soil vibration pore water pressure growth model based on thixotropic-induced excess pore pressure is established. The physical meaning of the model parameters is discussed, and the method to determine the parameters is given. The proposed method achieves an overall success rate of 83.6% when applied to a global database of 335 well-documented seismic case histories. Specifically, it correctly identifies 86% of the liquefied sites and 77% of the non-liquefied sites. In a direct quantitative comparison with the conventional NCEER simplified method on the same database, the TEPP model yields a higher area under the ROC curve (AUC: 0.793 vs. 0.759) and a higher overall accuracy (83.6% vs. 79.1%). The improvement in accuracy is statistically significant (McNemar test, p= 0.048). A systematic liquefaction discrimination process is proposed, which provides a new theoretical basis and practical tool for seismic liquefaction assessment.