Behavior of Fiber-Reinforced and Lime-Stabilized Clayey Soil in Triaxial Tests

Abstract

The beneficial role of combining fiber reinforcement with lime stabilization in altering soil behavior has been established in the literature. However, the coupling effect of their combination still remains unclear in terms of its magnitude and microscopic mechanism, especially for natural fibers with special microstructures. The objective of this study was to investigate the coupling effect of wheat straw fiber reinforcement and lime stabilization on the mechanical behavior of Hefei clayey soil. To achieve this, an experimental program including unconsolidated–undrained (UU) triaxial tests and SEM analysis was implemented. Static compaction test samples were prepared on untreated soil, fiber-reinforced soil, lime-stabilized soil, and lime-stabilized/fiber-reinforced soil at optimum moisture content with determining of the maximum dry density of the untreated soil. The lime was added in three different contents of 2%, 4%, and 6%, and 13 mm long wheat straw fiber slices with a cross section one-quarter that of the intact ones were mixed in at 0.2%, 0.4%, and 0.6% by dry weight of soil. Analysis of the derived results indicated that the addition of a small amount of wheat straw fibers into lime-stabilized soil improved the intensity of the strain-softening behavior associated with mere lime stabilization. The observed evidence that the shear strength increase brought by a combination of 0.4% fiber reinforcement and 4% lime stabilization was smaller than the summation of the shear strength increases brought by their presence alone in a sample demonstrated a coupling effect between fiber reinforcement and lime stabilization. This coupling effect was also detected in the comparisons of the secant modulus and failure pattern between the combined treatment and the individual treatments. These manifestations of the coupling effect were explained by a microscopic mechanism wherein the fiber reinforcing effect was made more effective by the ways in which lime chemically stabilized the soil and lime stabilization development was quickened by the water channels passing through the surfaces and honeycomb pores of the wheat straw fibers.

Effect of Cyclic Freezing-Thawing on the Shear Mechanical Characteristics of Nonpersistent Joints

“…Due to the difficulty and high cost of prefabricating joints on real geotechnical materials [36][37][38][39][40][41], many scholars have chosen the method of testing a similar material model to investigate the effect of joints on the mechanical strength characteristics of the rock. In this paper, the rock-like material cement mortar was selected to produce the specimen.…”

Characterization of Short-Term Strength Properties of Fiber/Cement-Modified Slurry

“…where a 1 � (σ max ω 21 /2); a 2 � (2ω 11 /ε max ); a 3 � b 11 − ω 11 ; a 4 � (σ max ω 22 /2); a 5 � (2ω 12 /ε max ); a 6 � b 12 − ω 12 ; and a 7 � (σ max /2)(b 2 + 1). ω 11 , ω 12 , b 11 , b 12 , ω 21 , ω 22 , and b 2 are the calculation parameters of the BP neural network. e specific meanings of these parameters are shown in Figure 10.…”

“…Various studies have been conducted to investigate the influences of fiber on the property of cemented soil through unconfined compression test or splitting strength testing [9][10][11]. Several scholars also performed triaxial test [12], direct shear test [13], bending test [14], isotropic compression test [15], and cyclic shear test [16] on fiber-admixed cemented soil. e studies showed that adding fiber into cemented sandy soil or clay with constant low cement content (less than 10%) could enhance its compressive strength, residual strength, and ductility.…”

Deformation Analysis of Granular Soils under Dynamic Compaction Based on Stochastic Medium Theory

“…Compacting the soil that will be under a foundation is an essential procedure to ensure the stability of the structure. Improving the soil beneath the foundation can be accomplished by a number of different methods including static or dynamic rollers and fiber reinforcement [1][2][3]. However, static or dynamic rollers are limited and can only compact the soil to a relatively shallow depth (0.2-1.0 m) [4] and fiber reinforcement is expensive and not environment-friendly for large construction projects [5].…”

“…However, static or dynamic rollers are limited and can only compact the soil to a relatively shallow depth (0.2-1.0 m) [4] and fiber reinforcement is expensive and not environment-friendly for large construction projects [5]. Compared with the above methods, dynamic compaction (DC) is a suitable method with the following advantages: (1) high density compaction to a considerable depth; (2) wide applicability in soils with different soil properties and different water contents; (3) simplicity of operation using widely available and simple equipment; (4) low cost. Menard [6] first introduced DC for construction and conducted systematically research on the method.…”