Abstract

AbstractThis paper reviews eight geoacoustic models applied to frozen soils: crystal growth models (grain cementing, grain coating, matrix supporting, and pore filling), the weighted equation (WE) model, Zimmerman and King's model (KT), the Biot‐Gassmann theory modified by Lee (BGTL), and a two‐end member model. We verify the capacity of these models to estimate unfrozen water content (UWC) based on “reference” UWC results and joint P and S wave velocities for different soil types. The satisfactory UWC estimates of saline unconsolidated sand and overconsolidated clay based on Vp data prove that the KT, BGTL, and two‐end member models are capable of modeling “smooth” transitions in the ice crystal growth mode, while they may provide less accurate UWC values when abrupt change of crystallization mode occurs. None of the tested soil types show a single crystallization mode throughout the freezing process, as assumed by individual crystal growth models. Vs‐based UWC estimates are less accurate due to significant but difficult‐to‐estimate influence of effective stress and soil initial cementation. All models, except pore filling and matrix supporting, can match Vs versus Vp measurement results for sands and silts but gradually provide inconsistent estimates with increasing clay content. We conclude that model validation by independent UWC measurements is necessary and that consistency between UWC values estimated from Vs and Vp is insufficient to ensure proper model validation.

Highlights

  • Saturated frozen soil is a multiphase porous material that consists of unfrozen water, ice, and solid particles

  • This paper reviews eight geoacoustic models applied to frozen soils: crystal growth models, the weighted equation (WE) model, Zimmerman and King's model (KT), the Biot‐Gassmann theory modified by Lee (BGTL), and a two‐end member model

  • More details regarding the physical limitations are presented here: 1. The KT model is capable of estimating velocity for a narrow range of porosities between 30% to 50% and low unfrozen water saturation (UWS) below 60%, because it assumes a dilute concentration of the water inclusions, in other words, a discontinuous water phase in the frozen soils

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Summary

Introduction

Saturated frozen soil is a multiphase porous material that consists of unfrozen water, ice, and solid (soil) particles. Several models are available, such as the weighted equation (WE) (Lee et al, 1996), the effective medium theories (Dou et al, 2017; Zimmerman & King, 1986), and the extended three‐phase Biot theory (Leclaire et al, 1994) These geoacoustic models have not been consistently validated against more accurate laboratory methods such as NMR and TDR. This paper reviews available parametric studies of soil type, temperature, and salinity effects on acoustic P and S wave velocities of frozen soil and revisits their physical mechanisms (sections 2.1–2.3). The original contribution of the paper consists of the intercomparison of those geoacoustic models to consistent data sets of acoustic velocities as function of UWC (as measured by NMR or TDR) from published studies (section 4.3) and discussion of their performance with clear physical explanations (section 5)

Acoustic Velocities Versus Soil Type and Temperature
Acoustic Velocity Versus Salinity
Acoustic Velocity Versus Freezing Thawing
Review of Geoacoustic Models for UWC Estimates
Selection of Geoacoustic Models and Data for Comparison Study
Data Selection and Analysis
Model Comparison
Discussions
Conclusions
Findings
Data Availability Statement
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