Effect of Particle Size and Constraint Conditions on Single Particle Strength of Carbonate Sand.

Yong He,Lei Gao,Huan He,Guojun Cai

doi:10.3390/s22030765

Abstract

Carbonate sand is often encountered and utilized as construction material in offshore engineering projects. Carbonate sand particles, which are porous and angular, are found to be highly crushable under high stress conditions, whereas the mechanisms and controlling factors for the crushing of carbonate sand particles are not well developed. The crushability and particle strength of around 400 particles from three fractions (5–10 mm, 2–5 mm, and 1–2 mm) of carbonate sand from the South China Sea were investigated via grain-scale single particle crushing tests. Special emphasis was placed on the effect of external constraint conditions (i.e., coordination number) and intrinsic particle morphology characteristics on the particle strength of carbonate soil. The particle strength of carbonate sand was found to be around half of quartz sand in terms of characteristic stress. Negative correlations, which could be depicted by an exponential equation, were found between the particle size and particle strength. Due to elongated particle shape and tensile stress concentration, a higher coordination number may lower the particle strength, which contradicts what was reported for quartz sands. A series of seven fundamental particle dimensions and five particle shape descriptors was characterized, and the aspect ratio was found to be one of the more influential shape descriptors for particle strength. The results enriched the database for the analysis of highly irregular geomaterial and provided insights into controlling factors of particle strength and crushing mechanisms of the carbonate sand.

Highlights

IntroductionMany studies in the literature emphasized that carbonate sand particles can be crushable in comparison with regular quartz sands, and the crushing of particles under high stress can alter mechanical and physical properties notably, such as changes in grading, high magnitude of compressibility and volume change, unique shearing behavior, low permeability, and high thermal conductivity [4,11,12,13,14,15,16,17]
Typical scanning electron microscope (SEM) images of a particle from 2 to 5 mm fraction are provided in Figure 1a, where it can be observed that sand particles are irregular in shape with internal pours covering the majority of the surface area
The particle strength of three uniform fractions (5–10 mm, 2–5 mm, and 1–2 mm) of carbonate sand from the South China Sea was tested under three constraint conditions

Summary

Introduction

Many studies in the literature emphasized that carbonate sand particles can be crushable in comparison with regular quartz sands, and the crushing of particles under high stress can alter mechanical and physical properties notably, such as changes in grading, high magnitude of compressibility and volume change, unique shearing behavior, low permeability, and high thermal conductivity [4,11,12,13,14,15,16,17]. High stress conditions can be common in projects such as driven piles or foundations of gravity hydraulic structures; particle crushing characteristics, especially for crushable sand, are important for investigation

Methods

Results

Conclusion