State of the art in the assessment of aging effects on soil liquefaction

摘要

A review of the current state of the art in the assessment of aging effects on soil liquefaction is presented in this paper. The review includes a summary of several field case histories indicating greater resistance to liquefaction in aged soils than in young uncemented soils during earthquakes, a discussion of the mechanisms that increase liquefaction resistance with time, an evaluation of proposed methods for quantifying the influence of aging processes (or diagenesis) on liquefaction resistance (K-DR), and an evaluation of proposed predictor variables for K-DR. The published literature indicates physical diagenetic processes tend to dominate the nature of interactions at the grain-to-grain contacts of sand deposits in the absence of sufficient cementing agents, while chemical processes tend to dominate where sufficient cementing agents are present. Variables proposed for predicting K-DR include: the time since deposition or last critical disturbance; the ratio of measured to estimated small-strain shear wave velocity (MEVR); the ratio of small-strain shear modulus to cone tip resistance (G(max)/q(c)); the adjusted G(max)/q(c) (K-G); and the ratio of measured to estimated adjusted G(max)/q(c) (MEKG). It is shown that MEVR, G(max)/q(c) K-G and MEKG are all ratios of measured to estimated or reference shear wave velocity. MEVR and G(max)/q(c) are slightly more robust predictors (i.e., regression equations with higher coefficient of regression and lower root mean square error) of K-DR than K-G and MEKG. Time is the least robust predictor of K-DR.