Keywords

1 Introduction

Enhancing the durability and efficiency of the sub-grade soil is attainable through the stabilization process. This has been proven to be a highly successful approach in achieving this goal. Given the unfavorable characteristics of soils, geotechnical engineers are constantly researching various methods that are cost-effective and meet the bearing capacity to stabilize such soils. Two methods, mainly mechanical and chemical, are usually adopted by geotechnical engineers to improve the stability of the soil. Relevant research on fibers and improved stability of soils include the following: Shao et al. [1] investigated the cement soil’s strength properties in saliferous and acidic-alkalescent environments and achieved precise outcomes. Liu et al. [2] experimented with the effects of corrosion on cemented soil's mechanical properties.. Chen et al. [3] examined the impact of sodium sulfate solution on the shear strength of cemented soil. Zhang and Li [4] researched the effects of salt lake solution on the strength of expansive soils. Hui et al. [5] experimented to study the compressive strength of basalt Clay soil reinforced with fiber. Chen et al. [6] analyzed the influence of fiber length and content on the durability of granite residual soil when reinforced with glass fiber and basalt fiber. Through my research, I have analyzed the influence of fiber length and content on the durability of granite residual soil when reinforced with glass fiber and basalt fiber. Lee et al. [7] examined the Macroscopic Bonding Principles and Microscopic Bonding Methods of Glass Fiber-Modified Loess. Ding et al. [8] conducted research on how the mechanical properties of cement-stabilized clay and polypropylene fiber are affected by freeze–thaw cycles.. In all the above-mentioned papers, it is shown that fibers increase the strength of soil significantly.

Using cement and lime to stabilize soil is a standard method that dramatically improves soil properties rapidly and significantly by reducing plasticity and eliminating swelling in soil [9, 10]. Because of their economic benefits, some researchers have used recycled basanite and coal ash as binders to stabilize expansive soil. However, the use of such materials is questionable due to their sustainability. Pore solution concentration, ion type, and pH value highly affect shrink-swell soil strength. Changes in pore solution result in macroscopic and mechanical properties. Soil strength improvement has been shown to combat these changes effectively. The mechanism of the effects of the type of solute and concentration in the pore water of expansive soil on the physical and mechanical properties of soil [11]. Therefore, it requires urgent investigation, considering potential geotechnical engineering issues such as geological hazards and soil slope stability.

This study investigated how saline solution and hydrochloric acid (HCL) affected the engineering characteristics of fiber-reinforced cement soil. To achieve this objective, cemented soil with basalt fiber and without fiber were soaked in different concentrations of salt and HCL solution (0.1, 0.3, and 0.5 mol/L) under different soaking times. An analysis was conducted on the impact of soaking time, fiber, solution type, and concentrations on the compressive strength of soil blocks.

2 Materials and Method

2.1 Materials

For this project, the soil that was tested had been gathered from a construction site located in Jilin Province's Changchun City, which is situated in China. The liquid and plastic-limited water content of the soil is 41% and 25%, respectively. Basalt fiber is used to reinforce the soil samples. The cement utilized is Ordinary Portland Cement with a rating of P.O. 42.5.

2.2 Preparation of Specimen

A cube test block measuring 70.7 mm × 70.7 mm × 70.7 mm was prepared according to the specifications of the ‘Cement Soil Mix Design Specification’ (JGJ/T 233–201). The block was mixed manually, loaded into a mold, and vibrated before being cured naturally for 1 day. It was then watered and covered with plastic film for 3 days before mold removal. The specimens were submerged in room temperature water for 28 days, as depicted in Fig. 1.

Fig. 1
A photo of the specimen.

Specimens cured in water

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2.3 Test Design

Na2SO4 and HCl solutions with 0.1, 0.3 and 0.5 mol/L concentrations were prepared, respectively. The prepared test blocks were put into the prepared solution and soaked for 1, 8, 19, 39, 54, and 60 days, respectively. The unconfined compressive strength of cemented soil was then tested. The test scheme is shown in Table 1.

Table 1 Test scheme
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3 Results and Discussion

3.1 The Effect of Soaking Time on Compressive Strength.

Figure 2 displays the results of measuring the compressive strength of soil that was soaked in distilled water. Two types of soil were tested: one with fiber and one without.

Fig. 2
A line graph plots the U C S in megapascals versus soaking time in days for 1 Water and 0 Water. 1 water, starts at (0, 1.9) and passes through (20, 2.55), (40, 2.85), to (60, 3.1). 0 Water, starts at (0, 2.1) and passes through (20, 2.4), (40, 2.7), to (60, 3.1). All values are approximate.

The relationship between compressive strength and soaking time of blocks in water

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The gradual increase of maintenance days is observed to have a positive impact on the unconfined compressive strength of test blocks soaked in clear water, as illustrated in Fig. 2. This is in line with the typical development law of cemented soil strength. The presence or absence of fiber in the cemented soil does not seem to have much effect on its strength.

3.2 The Impact of HCL on the Strength of Materials Under Unconfined Compression.

Figure 3 shows the strength curves of test blocks soaked in HCl solution at concentrations of 0.1, 0.3, and 0.5 mol/L for 1 day, 8 days, 19 days, 39 days, 54 days and 60 days, respectively.

Fig. 3
A multi-line graph compares the U C S in megapascals versus soaking time in days for 1 water, 1 H C l 0.1, 1 H C l 0.3, 1 H C l 0.5, 0 Water, 0 H C l 0.1, 0 H C l 0.3, and 0 H C l 0.5. 1 water and 0 water have the highest U C S with around 3 each and 1 H C l 0.5 has the lowest around 0.7 megapascals at 60 days.

The correlation between the compressive strength of cemented soil and the number of days it is soaked in an acidic environment (HCI)

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The compressive strength of test blocks soaked in acid is significantly lower than that of clear water. The strength of the samples submerged in an acidic environment declined as the duration of submersion increased. In the same concentration of the solution, the strength of cemented soil with fiber added is slightly higher than that without fiber, indicating that fiber plays a specific role in the resistance of cemented soil to acid solution erosion. Figure 4 shows the relationship between the stress and strain of cemented soil in HCL solutions.

Fig. 4
Six multi-line graphs plot the U C S versus strain percentage for 0 H C l 0.1, 1 H C l 0.1, 0 H C l 0.3, 1 H C l 0.3, 0 H C l 0.5, and, 1 H C l 0.5 at 1, 8, 19, 39, and 54 soaking days. All lines exhibit an initial increasing then a gradually decreasing trend.

Stress–strain curve

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3.3 Influence of Salt on the Compressive Strength

The concentration of Na2SO4 solution is depicted in the strength curves of the samples shown in Fig. 5. 0.1, 0.3, and 0.5 mol/L for 1 d, 8 d, 19 d, 39 d, 54 d, and 60 d, respectively. With the increase in soaking days, the strength of the samples showed a downward trend. With the increase of salt concentration, the unconfined compressive strength of basalt fiber cemented soil gradually decreases, especially at the concentration of 0.5 mol/L, the cemented soil with fiber added experienced 39 days, while the soil–cement without fiber added experienced only 19 days, and the failure occurred, as illustrated in Fig. 6.

Fig. 5
A multi-line graph compares the U C S versus soaking time for 1 Y 0.1, 1 Y 0.3, 1 Y 0.5, 0 Y 0.1, 0 Y 0.3, and 0 Y 0.5. 1 Y 0.1 has the highest U C S with 3.1 megapascals at 60 days, and 1 Y 0.5 has the lowest with 1.1 megapascals at 10 days. All values are approximate.

Relationship between unconfined compressive strength of basalt fiber reinforced cemented soil and soaking days in saline environment

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Fig. 6
A photo of a test block.

Test block after soaking

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4 Conclusion

Different soaking time cycles and unconfined compression tests were performed on basalt fiber-stabilized cemented clayey soil, and the effects of different soaking times on stress–strain behaviors and unconfined compressive strength were analyzed and discussed. The main findings of this study can be summarized as follows:

  1. (1)

    It can be concluded that samples soaked in water retained most of their properties and strength, the longer the samples were soaked, the weaker they became.

  2. (2)

    The unconfined compressive strength of the test blocks soaked in acidic environment gradually decreases with the increase of soaking time, and the strength of cemented soil with fiber is slightly higher than that without fiber in the same concentration of the solution, indicating that fiber plays a specific role in the resistance of cemented soil to acid solution erosion.

  3. (3)

    With the increase of salt concentration, the strength of basalt when subjected to compression without confinement. Fiber-reinforced cemented soil gradually decreases, especially at the concentration of 0.5 mol/L, the fiber-reinforced cemented soil experienced 39 days, while the reinforced cemented soil experienced only 19 days.

  4. (4)

    The incorporation of basalt fiber in clay soil has been found to be a highly effective method of enhancing the compressive strength of the soil. (UCS).