Critical Shear Stress for Erosion of Sand-Mud Mixtures and Pure Mud

Dake Chen,Jinhai Zheng,Yigang Wang,Yuan Li,Dawei Guan,Chi Zhang

doi:10.3389/fmars.2021.713039

Abstract

The erosion threshold of sand-mud mixtures is investigated by analyzing the momentum balance of a sand particle or a mud parcel in the mixture bed surface, and a formula for the critical shear stress of sand-mud mixtures is developed, which also applies for pure sand and mud. The developed formula suggests that the variation of the critical shear stress of sand-mud mixtures over mud content is mainly caused by the varying dry bulk density of the mud component in the mixture. The developed formula reproduces well the variation of the critical shear stress of sand-mud mixtures over mud content and can predict the critical shear stress of both sand-mud mixtures and pure mud in the process of consolidation. The developed formula promises to be convenient for application by relating the critical shear stress to mud content and the dry bulk density of sediment.

Highlights

The erosion of sediment is one of the controlling processes of sediment dynamics in aquatic systems
The present study aims to develop a formula for the critical shear stress of sand-mud mixtures
Equation (23) is the formula we develop for predicting the critical shear stress of sand-mud mixtures

Summary

INTRODUCTION

The erosion of sediment is one of the controlling processes of sediment dynamics in aquatic systems. Wu et al (2017) developed a formula for the critical shear stress of sand-mud mixtures by analyzing the force balance on a sediment parcel beginning to erode from the bed surface: τcr = τcrL + (τcrmc − τcrL) exp −α ps pm βw (3). Chen et al (2018) developed a formula for the critical shear stress of sand-mud mixtures based on the analysis of the balance of forces on a single particle of the mixture: θcr0. Prior to mixing with sand, each mud was slurried with freshwater, and the slurry density was maintained at a density of FIGURE 6 | The calculated vs measured critical shear stresses in the case of Jacobs et al (2011): (A,C) sand-silt-kaolinite mixtures, (B,D) sand-silt-bentonite mixtures; (A,B) Eq (23) and (C,D) the formula of Chen et al (2018). Eq (23) gives reasonable estimates of the critical shear stress in all the cases, demonstrating the capacity of the developed formula in pure mud

Findings

DISCUSSION

CONCLUSION