Experimental Investigation of Mechanical, Permeability, and Microstructural Properties of PVA-Improved Sand Under Dry-Wet Cycling Conditions

Zhongyao Li,Haiping Shi,Peiqing Wang,Wenwei Li,Zhewei Zhao,Baotian Wang

doi:10.3389/fphy.2021.761754

Abstract

To improve the stability of sand slopes in Southeast Tibet, the wet–dry cycle test, immersion test, and permeability test were carried out using polyvinyl alcohol (PVA) as the improving material. The improvement effect was evaluated by considering the unconfined compressive strength. The results have revealed that the unconfined compressive strength of the improved soil significantly increased with the PVA content, while the degradation of the improved soil by wet–dry cycling and water immersion weakened. However, the permeability of the improved soil slightly decreased compared with that of unmodified soil. Through scanning electron microscopy (SEM), it was found that PVA only forms an elastic network structure in the sand to wind and connect the soil particles, but pores remain in the sand. This indicates that the addition of PVA does not affect the permeability to a great extent but greatly increases the strength. The findings of this study provide a useful reference for the practical application of PVA.

Highlights

The engineering characteristics of sandy soil are poor, which increases the likelihood of various engineering geological problems
The unconfined compressive strength of the stabilized sand increased with the polyvinyl alcohol (PVA) content
After 10 wet–dry cycles, the unconfined compressive strength of the improved soil with 12% PVA content decreased from 1038.96 kPa to 875.99 kPa and was still much higher than the unconfined compressive strength of the non-stabilized soil samples cured for 7 days (10.19 kPa)

Summary

INTRODUCTION

The engineering characteristics of sandy soil are poor, which increases the likelihood of various engineering geological problems. Traditional chemical modifiers, including cement, lime, and fly ash, can fill the pores between the soil particles and exert a bonding effect on the soil particles, which greatly improves the strength of the soil Such modified materials have a drastic reaction process and high alkalinity and change the mineral composition of the soil, which is harmful to the environment because the soil ecology is significantly affected. The film formed by polyvinyl alcohol (PVA) has good tensile strength and the polymers are uniformly distributed in the soil, which limits the soil particles to a certain position, increases the strength of the soil, and improves the soil’s durability [14, 15]. The organic polymer PVA-20-99H was used as an improving material because it is capable of coating sand particles, increasing the interaction force between the particles, and changing the engineering characteristics of sand.

RESULTS

CONCLUSION

DATA AVAILABILITY STATEMENT