Effects of Cyclic Freezing–Thawing on Dynamic Properties of Loess Reinforced with Polypropylene Fiber and Fly Ash

Shufeng Chen,Tao Luo,Yao Zhang,Gang Li

doi:10.3390/w14030317

Abstract

Periodic freezing–thawing is recognized as a real threat to the mechanical properties of reinforced loess, which has been used in the recent construction of high-speed railways in northwest China; however, the performance of these materials under periodic freezing–thawing and dynamic loading has rarely been investigated. In this work, dynamic triaxial tests were conducted on fly ash- and polypropylene fiber-reinforced loess with different blend ratios and freeze–thaw cycles. The dynamic shear modulus and damping ratio were investigated. The results revealed that cyclic freezing–thawing had a remarkable effect on the dynamic shear modulus and damping ratio, which demonstrated considerable reductions and increases, respectively, after cyclic freezing–thawing. Additionally, the dynamic shear modulus increased notably with the fly ash content and confining pressure and decreased with the water content. Meanwhile, the damping ratio increased with the fiber content and water content and decreased with the fly ash content and confining pressure. Comparatively, the effects of polypropylene fiber on dynamic behavior were found to be not significant. Furthermore, novel models were established to predict the dynamic shear modulus and damping ratio for reinforced loess. The results provide more information towards infrastructure design in seasonal frozen regions.

Highlights

Loess is widespread soil that stretches from seasonal frozen areas to permafrost areas in Northern China
Due to a lack of coarse-grained materials, it is often selected as a filling material for highways, railways, and high-speed railways (HSR) despite its unfavorable engineering characteristics such as its large pores and high sensitivity to water and temperature [1,2,3]
There are few studies on Fly ash (FA)-reinforced loess, and fewer have promoted a combination of FA and synthetic fibers to reinforce loess soils [16]

Summary

Introduction

Loess is widespread soil that stretches from seasonal frozen areas to permafrost areas in Northern China. An effective method to mitigate these deficiencies and to improve the fill is to reinforce the soil with cementitious additives and reinforcing materials [4]. The freezing–thawing weathering process and dynamic traffic loads could strongly influence the long-term dynamic behaviors of the modified loess substructure and could threaten the operational safety of infrastructures [5,6,7]. Loess-reinforcing techniques to create better pavements based on conventional stabilizers, such as cement and lime, have become more mature due to long-term progress and practices [8,9,10]. In the context of energy-saving and sustainable development policies, many experimental research studies have been focused on FA-based reinforcing techniques for different types of soils. There are few studies on FA-reinforced loess, and fewer have promoted a combination of FA and synthetic fibers to reinforce loess soils [16]

Methods

Results

Conclusion