Correlation between liquefaction resistance and shear wave velocity of granular soils: a micromechanical perspective

Abstract

The shear wave velocity method has become an increasingly popular means to evaluate the liquefaction potential of granular soils. Understanding the fundamental mechanism underlying existing empirical or semi-empirical relationships is important for better assessing their reliability. This paper presents a particle-scale study of the correlation between cyclic resistance ratio (CRR) and the shear wave velocity corrected for overburden stress (V s1). The discrete-element method was used to simulate a series of undrained stress-controlled cyclic triaxial tests together with shear wave velocity (V s) measurements. Discrete-element method modelling with various relative densities, confining pressures and micro-parameters was performed under various cyclic stress ratios (CSRs), and the onset of liquefaction was illustrated through both macroscopic and microscopic responses, for example, inferred excess pore-water pressure, mechanical coordination number and redundancy index. The inter-particle friction was identified as the key micro-parameter that governs the liquefaction resistance of granular soils. A micro-scale CRR-V s1 correlation considering two independent micro-parameters, inter-particle friction and particle shear modulus, was then obtained and further validated with the outcomes from three dynamic centrifuge model tests performed on silica sand no. 8. This study demonstrates that the CRR-V s1 correlation is particle specific, thus soil specific, and the particle mechanical properties should be included in the V s-based method for future liquefaction evaluation of granular soils.

Effect of particle size distribution on the correlation between liquefaction resistance and shear wave velocity of granular soils

“…The author developed codes based on PFC3Dv3.10, which can parallel-process assemblies and shearing tests. 1.17 28,335 Table 1 shows the particles numbers inside samples of PSD curves in this study (C2&C4), as well as previous study [4]. The limit of one single processor is of the order of 100,000 particles in three dimensions, in terms of the computation speed [12].…”

“…Shear wave velocity corrected for overburden stress (Vs1, s for shear and 1 for principal direction of overburden stress) is widely considered as a promising alternative to assess the liquefaction resistance of granular soils. Previous researchers [1][2][3] performed numbers of cyclic tri-axial and dynamic centrifuge tests, whose work verified the reliability and suggested the CRR-Vs1 correlation could be affected by soil types because the shear modulus (Gg) and the inter-particle friction parameter (μg) of soil particles play vital roles [4], as shown by equation (1).…”

“…By numerical tests, calibrated them for Silico Sand no.8. The value of φg obtained is 39.9 , and Gg is 6.649GPa [4,5]. Using these two calibrated parameters, they produced a prediction curve which achieved 92% accuracy in separating liquefied and non-liquefied cases of centrifuge tests.…”

“…Particles' shear modulus could be calibrated by comparing numerical and laboratory shearing wave tests, based on the assumption that the real sand follows the same Vs-Gg power law [4]. PSD of samples could affect the outcome of Gg because a sample of lower void ratio tends to have a higher shear wave velocity inside [11], and a better graded assembly would achieve higher initial bulk density at any relative density level.…”

“…The objective of this paper is to show how and why PSDs affect calibrations for Silico sand no.8, in terms of the inter-particle friction and the shear modulus, and eventually the prediction curve for liquefaction resistance, in that the previous calibration [4] employed only one single uniform PSD curve. This paper conducted an integrated analysis on what PSD effects are.…”