Model for predicting evolution of microstructural void ratio in compacted clayey soils

Penghai Yin,Sai K Vanapalli

doi:10.1139/cgj-2021-0057

Abstract

The hydromechanical behavior of compacted clayey soils is significantly influenced by its microstructure. The microstructural void ratio is a key parameter that is strongly associated with the microstructural state. The objective of this study is to provide a practical and reliable estimation approach for predicting the evolution of the microstructural void ratio of compacted clay soils subjected to wetting and drying paths. In this paper, the microstructural evolution of 12 clayey soils was investigated quantitatively using the mercury intrusion porosimetry (MIP) results. Based on this study, a comprehensive criterion has been developed for identifying different pore populations of compacted clayey soils for interpreting the MIP results. The “as-compacted state line” was proposed to estimate the initial microstructural void ratio of clayey soils at the as-compacted state. An incremental linear constitutive model was proposed for correlating the microstructural void ratio to the “microstructural average skeleton stress” in compacted clayey soils following monotonic wetting and drying paths. The developed approach is validated by providing comparisons between the predicted and interpreted microstructural void ratios for all the examined soils. The proposed approach can be extended in constitutive modeling of the hydromechanical behavior of compacted clayey soils by incorporating explicitly the microstructural information.

Highlights

It is widely recognized in the literature that the soil microstructure significantly influences the hydraulic and mechanical properties of compacted clayey soils
This study provides a comprehensive criterion for identifying different pore populations in compacted clayey soils when interpreting the microstructural data using the mercury intrusion porosimetry (MIP) results
The evolution of microstructural void ratio of compacted clayey soils upon wetting and drying paths is investigated by interpreting the MIP results of 12 soils, which include four high-plasticity clays and eight low-plasticity clays

Summary

Introduction

It is widely recognized in the literature that the soil microstructure significantly influences the hydraulic and mechanical properties of compacted clayey soils. During the last 25 years, information on soil fabric and pore-size distribution was available using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), respectively, from direct observations. Both the SEM and MIP serve as tools to provide insight into the microstructural evolution of compacted clayey soils due to mechanical loading/unloading or wetting/drying processes (e.g., Al-Mukhtar et al 1996; Delage et al 1996; Cuisinier and Laloui 2004; Monroy et al 2010; Burton et al 2015; Li et al 2020). Remarkable advancements have been achieved in modeling the behavior of compacted clayey soils incorporating explicitly the microstructural evolution, such as the soil–water characteristic curve (e.g., Romero et al 2011; Hu et al 2013; Della Vecchia et al 2015), hydraulic conductivity (e.g., Romero 2013; Wang et al 2013; Azizi et al 2020), mechanical constitutive behavior (e.g., Gens 2010; Alonso et al 2013; Qiao et al 2019), and shear strength and tensile strength properties (e.g., Alonso et al 2010; Trabelsi et al 2018)

Objectives

Findings

Discussion

Conclusion