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

Abstract

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 (KDR), and an evaluation of proposed predictor variables for KDR. 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 KDR 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 (Gmax/qc); the adjusted Gmax/qc (KG); and the ratio of measured to estimated adjusted Gmax/qc (MEKG). It is shown that MEVR, Gmax/qc, KG and MEKG are all ratios of measured to estimated or reference shear wave velocity. MEVR and Gmax/qc are slightly more robust predictors (i.e., regression equations with higher coefficient of regression and lower root mean square error) of KDR than KG and MEKG. Time is the least robust predictor of KDR.