Applicability of soil‐type index for shear wave velocity‐based liquefaction assessment

Abstract

The current simplified liquefaction assessment method based on the shear‐wave velocity, Vs has uncertainties about how the fine contents change the Vs‐based liquefaction resistance. According to the simplified method, for a given Vs, the cyclic resistance ratio (CRR) increases with an increase in fine contents. However, field investigations recently revealed that for various silty sands, the correlation between CRR and Vs is soil‐type index dependent and not specific for all sand‐silt mixtures with the same fine contents. Therefore, a detailed experimental research program is performed in this study to clarify the effect of the soil‐type index on the shear wave velocity and CRR correlation. In the first part of the present study, the cyclic resistance of sand mixed with non‐plastic (NP) fines (dry weight of 0%, 5%, 15%, and 35%) was investigated using cyclic direct simple shear (CDSS) tests. Seismic cone penetration (SCPT) tests were performed inside the large‐scale box to facilitate normalized cone penetration resistance (qc1N) and shear wave velocity measurements on the soils used in the CDSS tests. A new correlation was proposed between the qc1N and normalized shear wave velocity (Vs1) using the soil‐type index Ic representing the behavior of soil. Then, CRR‐Vs1 correlation was obtained experimentally for four distinct ranges of soil‐type index. Finally, the results of this study and the proposed CRR‐Vs1 trends in other investigations were used to discuss the soil‐type dependent Vs‐based liquefaction susceptibility zones.

Revisiting the effect of relative density on cyclic liquefaction of clean and silty sands: the crossing effect

“…silty sand has greater liquefaction resistance than the clean sand at a given V s1 > 170 m/s), whereas the opposite trend was observed for V s1 < 170 m/s (i.e. silty sand has smaller liquefaction resistance than the clean sand at a given V s1 < 170 m/s) (Ecemis et al 2024).…”

“…In fact, a very recent study of the first author, involving Seismic Cone Penetration Tests (SCPT) on Silica sand-silt mixtures deposited in a rigid aluminum box, also revealed that Cyclic Resistance Ratio (CRR 7.5 ) vs. normalized shear wave velocity (V s1 ) curves could also show a trend similar to the "crossing effect" introduced in this paper. In that study, CRR 7.5 − V s1 curves for the sand-silt mixtures having different soil type indices (I c ) were shown to cross each other at around V s1 = 170 m/s (Ecemis et al 2024). Liquefaction resistance of silty sand with 10% FC becomes greater than that of the silty sand with 5% FC More specifically, for V s1 > 170 m/s, liquefaction resistance of the tested sand-silt mixtures was shown to increase with increasing I c (i.e.…”