Combined Effect of Biopolymer and Fiber Inclusions on Unconfined Compressive Strength of Soft Soil.

Chunhui Chen,Xianyao Dai,Kai Wei,Jiayu Gu,Xiaoyang Huang,Qingbing Liu

doi:10.3390/polym14040787

Abstract

The utilizing of traditional chemical stabilizers could improve soil engineering properties but also results in brittle behavior and causes environmental problems. This study investigates the feasibility of the combined utilization of an ecofriendly biopolymer and fiber inclusions as an alternative to traditional cement for reinforcing soft soil. A series of unconfined compression tests were conducted to examine the combined effect of the biopolymer and fibers on the stress–strain characteristics, strength improvement, failure pattern, and reinforcement mechanism of soft soil. The results show that the biopolymer associated with fibers has an unconfined compressive strength similar to that of fiber-reinforced soil. However, it then increases with different curing times and conditions, which can be up to 1.5 MPa–2.5 MPa. The combined effect of fibers and the biopolymer is not simply equivalent to the sum of the effects of each individual material. The fiber shows its role instantly after being mixed into soil, whereas the effect of biopolymer gradually appears with sample curing time. The biopolymer plays a dominant role in increasing the peak unconfined compressive strength and brittleness of soil, while the amount of fiber is crucial for reducing soil brittleness and increasing ductility. It is shown that the biopolymer not only contributes to the particle bonding force but also facilitates the reinforcement efficiency of fibers in the soil. The fibers in return assist in reducing the soil brittleness arising from biopolymer cementation and provide residual resistance after post-peak failure.

Highlights

In geotechnical engineering practice, untreated soft soil with low strength, large deformation or poor stability may lead to slope instability, road pavement deformation and building leaning [1,2]
The results indicate that a higher biopolymer content did not guarantee high soil strength
The employed soft soil is a silty clay collected in the vicinity of a road construction site along the Yangtze River in Wuhan, China

Summary

Introduction

In geotechnical engineering practice, untreated soft soil with low strength, large deformation or poor stability may lead to slope instability, road pavement deformation and building leaning [1,2]. Soil reinforcement is a technique to improve soil geotechnical properties including shear strength, compressibility, and bearing capacity. The commonly used soil reinforcement techniques are physical and chemical soil stabilization [3,4,5]. Chemical compounds are mixed with soil particles to modify the soil geotechnical properties in the chemical stabilization method. When cement is mixed with water and other additives in the soil, chemical reactions occur between these compounds [7]. The hydrated cement increases the soil particle interaction and improves the micropore structure, changing the soil properties. Cement is competitive in soil stabilization due to its high strength, long-term durability, and low cost. Cement manufacture has led to a continuous increase in the emission of carbon dioxide, nitrogen oxides, dust, and solid waste, which has caused severe environmental concerns [8,9]

Methods

Findings

Discussion

Conclusion