Mechanical Properties of Fiber-Reinforced Soil under Triaxial Compression and Parameter Determination Based on the Duncan-Chang Model

Yingying Zhao,Xianzhang Ling,Peng Li,Guoyu Li,Lina Wang,Weigong Gong

doi:10.3390/app10249043

Abstract

To study the mechanical properties of Y-shaped polypropylene fiber-reinforced subgrade fill, the strength characteristics of fiber-reinforced soil with different fiber contents, fiber lengths, and confining pressures were investigated through triaxial compression tests. The test results showed that fiber reinforcement significantly improved the strength and cohesion of the subgrade fill but had a limited impact on the internal friction angle. The fiber-reinforced soil specimens exhibited a failure pattern of bulging deformation, showing plastic failure characteristics. As the fiber content and length increased, the strength of the fiber-reinforced soil increased and then decreased. The optimal fiber content was 0.2%, and the optimal fiber length was between 12 and 18 mm in all test conditions. The strength of the fiber-reinforced soil increased with increasing confining pressure. An empirical model for predicting the failure strength of fiber-reinforced soil was established by analyzing the relationships between the failure strength of the fiber-reinforced soil and the fiber content, fiber length, and confining pressure. The stress-strain relationship of the fiber-reinforced soil exhibited strain-hardening characteristics and could be approximated by a hyperbolic curve. The Duncan-Chang model could be used to describe the stress-strain relationship of this fiber-reinforced soil. A calculation method to determine the model parameters (initial tangent modulus and ultimate deviator stress) was proposed.

Highlights

A widely used method for subgrade reinforcement is horizontal fiber reinforcement.The reinforcement direction and spacing can cause weak interfaces, such that only the lateral deformation of the subgrade can be controlled, and the problem of subgrade settlement deformation cannot be controlled
To compare the reinforcement effects under same conditions before and after fiber reinforcement, the moisture content of the fiber reinforced soil was adjusted to the water content of 8.5%
In order to guarantee the uniformity of fibers within the sample distribution and the homogeneity of material, the moist tamping technique, widely used to prepare non-cohesive fiber reinforced soil, was used to prepare fiber soil samples, which can well mix fibers and soil, and its effectiveness has been verified by a large number of experiments conducted by Michalowski and Russell [16], Wood et al [17], Ibraim et al [18,19], and Diambra et al [20]

Summary

Introduction

A widely used method for subgrade reinforcement is horizontal fiber reinforcement. The reinforcement direction and spacing can cause weak interfaces, such that only the lateral deformation of the subgrade can be controlled, and the problem of subgrade settlement deformation cannot be controlled. Three-dimensional (3D) fiber reinforcement for subgrade projects has been. This kind of fiber reinforcement is a geotechnical composite technology that mixes short fibers or continuous fibers randomly and discretely into the soil [1] to improve the mechanical properties of the soil through the friction between the fiber and soil and between the fibers in the 3D reticulated fiber system [2,3], and has been popularized and applied in reinforcement projects such as subgrades, side slopes, and retaining walls

Methods

Results

Conclusion