Shear strength and deformation characteristics of corn husk fiber-reinforced loess

Abstract

The use of corn husks to reinforce loess can turn discarded corn husks into a valuable resource and save the cost of loess reinforcement. This study measured and analyzed the shear strength and deformation of corn husk fiber (CHF)-reinforced loesses with five reinforcement ratios, five compaction degrees, and four normal stresses. For the reinforced loess, the shear stress-shear displacement curve changes from strain softening to strain hardening with the increasing normal stress. Compared with the friction angle, the addition of CHFs has a greater effect on increasing the cohesion. The optimal reinforcement ratio is typically 0.3%. However, the optimal reinforcement ratio will increase under high compaction degree and high normal stress. Generally, as the shear displacement increases, the vertical displacement first increases in one direction (positive or negative) and then tends to stabilize. However, for the reinforced loess at 100% compaction degree under the normal stress of 300 kPa, the vertical displacement first increases along the negative direction and then increases along the positive direction to a positive value, indicating that the loess first undergoes shear contraction and then shear expansion. As the compaction degree of reinforced loess increases, the shear expansion phenomenon becomes more significant, or the shear contraction phenomenon becomes less significant. The shear expansion or shear contraction phenomenon becomes less significant as the reinforcement ratio increases, indicating that increasing the reinforcement ratio within the effective range can suppress the deformation of loess. This study provides theoretical support for the use of corn husk to reinforce loess.

Introduction

Loess is widely distributed around the world. Taking China as an example, the total area of loess regions is about 630,000 square kilometers¹. As more and more infrastructures are built in loess regions, loess geohazards, including debris flow^2,3 landslides^4,5 collapse^6,7 subgrade subsidence^8,9 and earth fissures^10,11 have become frequent. These loess geohazards are closely related to the low strength of loess¹. Improving and reinforcing the loess in the construction area is an important measure to reduce loess geological disasters.

Chemical and physical methods are currently the main methods of loess (or other soils requiring reinforcement) improvement. The chemical method mainly involves the incorporation of chemical stabilizing agents¹². The agents can react chemically with soil minerals to increase the bond strength and contact area between soil particles, thus improving the strength of the soil. The chemical stabilizing agents mainly include fly ash^13,14 cement^15–17 lime^18,19 epoxy resin^20,21 alkaline activator²² etc. Physical methods include sand blending²³ the dynamic compaction method^24,25 pile support²⁶ and the addition of reinforcement materials^27,28. These methods mainly improve the pore characteristics, increase the compactness of the soil, and enhance the shear strength and tensile strength from a physical point of view.

Currently, the commonly used reinforcement materials for loess improvement are geogrids, polypropylene fibers, and other man-made reinforcement materials^28–30. The processing of these man-made reinforcement materials consumes a large amount of resources. Corn husk from the by-product of maize is a natural material with high shear strength and tension strength. It is reported that the tension strength of corn husk is as high as about 160 MPa, which is higher than that of glass fiber³¹. Its tension strength can be increased to a maximum of about 365 MPa after specific chemical treatments^31,32. Corn husks have been tried out to reinforce other materials. For example, Duong, et al.³³ explored the potential of corn husk fibers (CHFs) for reinforcing cemented soils with high water content. Youssef, et al.³⁴ investigated the influence of corn husk addition on low-density polyethylene composite and found that the addition of CHFs improves the mechanical properties of the composite.

Mature corn is used as food, industrial consumption, animal feed, etc. However, a large number of corn husks are burned as waste material. The burning of corn husks produces a large amount of smoke that pollutes the air environment. The corn husk is light, cheap, and available abundantly³¹. The use of corn husks to reinforce loess can turn discarded corn husks into a valuable resource and save the cost of loess reinforcement. This initiative not only reduces the use of energy-consuming man-made reinforcement materials but also plays a positive role in the protection of the ecological environment.

This study aimed to investigate shear strength and deformation characteristics of CHF-reinforced loess with five reinforcement ratios, five compaction degrees, and four normal stresses. Shear stress-shear displacement curves and vertical displacement-shear displacement curves of CHF-reinforced loess were first measured and analyzed. Then, the effect of compaction degree and reinforcement ratio on the shear strength of CHF-reinforced loess was explored. Finally, the effect of compaction degree and reinforcement ratio on the vertical displacement of CHF-reinforced loess was revealed.

Materials and methods

Test materials

The loess used in the tests was taken from a roadbed soil in Xi’an City, Shaanxi Province, China. Impurities in the roadbed soil were removed. The color of the soil was yellowish brown. The basic physical parameters of the loess are shown in Table 1. In Table 1, the specific gravity was determined by the specific gravity bottle method. The liquid-plastic limit was determined by the joint liquid-plastic limit tester produced by Nanjing Soil Instrument Factory. The compaction test was carried out by a lightweight compactor produced by Nanjing Soil Instrument Factory, with a hammer weight of 2.5 kg, a diameter of 51 mm at the bottom of the hammer, and a drop height of 305 mm. The compaction curve is shown in Fig. 1. The particle gradation was determined by the sieving method and densitometer method. The grading curve is shown in Fig. 2. The implementation steps of the above tests strictly followed the Chinese standard “Test methods of soils for highway engineering” (JTG E40-2007).

Table 1.

The basic physical parameters of the loess.

Specific gravity	Liquid limit	Plastic limit	Plasticity index	Maximum dry density	Optimum moisture content
2.72	31.3%	19.7%	11.6	11.6 g/cm3	18.9%

Fig. 1.

The compaction curve of the loess.

Fig. 2.

The grading curve of the loess.

The corn husks used in the tests were taken from a rural area in Weinan City, Shaanxi Province. Corn husks were first dried naturally, as shown in Fig. 3. They were then cut into fibers and used to reinforce loess. The length, width, and length-to-width ratio of the fibers are approximately 3 cm, 2 mm, and 15, respectively. The average density of the corn husk was 0.294 g/cm³ by the drainage method. The average tensile strength of the corn husk was 12.067 MPa by a universal testing machine.

Fig. 3.

Dried corn husks before being cut into fibers.

Test methods and process

Reinforcement cases

To investigate the effects of different CHF reinforcement ratios and loess compaction degrees on CHF-reinforced loess, five reinforcement ratios (0.15%, 0.2%, 0.25%, 0.3%, and 0.35%), five compaction degrees (92%, 94%, 96%, 98%, and 100%) were used. The moisture content of the loess was formulated to be the optimum moisture content of 18.9% for all reinforcement cases.

The reinforcement ratios and compaction degrees adopted in this study were determined based on the results of preliminary tests. Preliminary test results indicated that when the reinforcement ratio was too low, the shear strength of the reinforced loess was very close to that of the unreinforced loess, indicating that the reinforcement effect was weak. When the reinforcement ratio was too high, mixing became extremely difficult. In such cases, fibers tended to be unevenly distributed and clumped together, potentially resulting in a decrease rather than an increase in the shear strength. Accordingly, this study selected the moderate reinforcement ratios (0.15–0.35%).

Preliminary test results indicate that when the compaction degree was too low, there were insufficient contact points between the fibers and soil particles, and the contact force was weak, resulting in poor reinforcement effects. Additionally, when the compaction degree of loess is too low, the arrangement of soil particles is loose, and the porosity ratio is high, resulting in low shear strength. To ensure good reinforcement effects, high compaction degrees are also maintained during on-site construction. Based on the above reasons, this study used high compaction degrees between 92% and 100%.

Sample preparation process

The sample preparation process followed the Chinese standard “Test methods of soils for highway engineering” (JTG E40-2007). The preparation of unreinforced loess samples was carried out in a cutting ring by the hydrostatic molding method. The height, inner diameter, and volume of the cutting ring were 20.00 mm, 61.80 mm, and 59.99 cm³respectively. During sample preparation, the loess was weighed according to the pre-calculated mass of the sample and then pressed into the cutting ring. The mass of the sample is calculated according to Eq. (1).

1

where m, ρ_dmax, k, w_s, and V are the mass, maximum dry density, compaction degree, moisture content of the sample, and the volume of the cutting ring, respectively.

Similar to the preparation of unreinforced loess samples, reinforced loess samples were also prepared using a cutting ring by the hydrostatic molding method. This study defines the ratio of the mass of the reinforcement material to the dry mass of the soil as the reinforcement ratio J, similar to previous studies. The specified mass of CHFs was first mixed evenly with the loess (adjusted to the optimum moisture content). Subsequently, the reinforced loess poured into the cutting ring was compacted. The mass of CHFs required for a loess sample is calculated according to Eq. (2).

2

where m_J and J are the mass of CHFs and the reinforcement ratio, respectively.

Methods for measuring shear strength and deformation of reinforced loess

The shear strength of the reinforced loess was determined through the direct shear test. A strain-controlled direct shear apparatus manufactured by Nanjing Soil Instrument Factory was used. The range and scale interval of the dial gauge on the force gauge were 10 mm and 0.01 mm, respectively. The calibration coefficient of the force gauge was 1.587 kPa. The test was conducted at a shear rate of 0.8 mm/min. The test procedure strictly followed the Chinese standard “Test methods of soils for highway engineering” (JTG E40-2007).

To measure the vertical deformation of the sample during the shear process, a dial gauge was connected directly above the center of the direct shear box to measure the vertical displacement, as shown in Fig. 4. The dial gauge had a range of 10 mm and a graduation value of 0.01 mm. During the shear process, the sample exhibited shear expansion or shear contraction. Clockwise rotation of the dial gauge pointer indicated positive displacement, i.e., shear expansion, while counterclockwise rotation indicated negative displacement, i.e., shear contraction.

Fig. 4.

Schematic diagram of the test method.

Test results

Shear stress-shear displacement curves of unreinforced loess

Figure 5 shows shear stress-shear displacement curves for unreinforced loesses under four normal stresses (50, 100, 200, 300 kPa) at five compaction degrees. Under normal stress of 50 kPa, the shear stress of samples at all five compaction degrees first increases with increasing shear displacement. After reaching a peak, the shear stress decreases with further increases in shear displacement, indicating that the shear stress-shear displacement curve exhibits strain-softening behavior. Under normal stresses of 100, 200, and 300 kPa, the shear stress of samples at all five compaction degrees increases rapidly with increasing shear displacement. Once the shear stress reaches a certain level, the rate of increase in shear stress slows down. No peak point appears, indicating that the shear stress-shear displacement curve exhibits strain-hardening behavior.

Fig. 5.

Shear stress-shear displacement curves for unreinforced loesses under four normal stresses (50, 100, 200, 300 kPa) at five compaction degrees: (a) 92% compaction degree; (b) 94% compaction degree; (c) 96% compaction degree; (d) 98% compaction degree; and (e) 100% compaction degree.

When the shear stress-shear displacement curve has a peak point, the peak point is determined to be the shear strength. When the shear stress-shear displacement curve does not have a peak point, the shear stress corresponding to a shear displacement of 4 mm is determined to be the shear strength. Shear strength versus normal stress for unreinforced loess at five compaction degrees is shown in Fig. 6. The data points for each compaction degree in Fig. 6 are fitted using a linear equation. The fitting results are satisfactory. The cohesion and friction angle can be obtained using the fitted linear equation and Coulomb’s formula.

Fig. 6.

Shear strength versus normal stress for unreinforced loess at five compaction degrees.

Shear stress-shear displacement curves of reinforced loess

For five different compaction degrees, the shear stress-shear displacement curves of reinforced loesses show generally consistent patterns. Therefore, the shear stress-shear displacement curves for 92% compaction degree are presented as representative, as shown in Fig. 7. Under a normal stress of 50 kPa, the shear stress first increases with increasing shear displacement. After reaching a peak, the shear stress decreases with further increases in shear displacement, indicating that the shear stress-shear displacement curve exhibits strain-softening behavior. Under normal stresses of 100 kPa, 200 kPa, and 300 kPa, the shear stress first increases rapidly with increasing shear displacement. Once the shear stress reaches a certain level, the rate of increase in shear stress slows down. The absence of a peak indicates that the shear stress-shear displacement curve exhibits strain-hardening behavior. As shown in Fig. 7, under the same normal stress, the increase rate of shear stress in the early growth segment of the curve increases as the reinforcement ratio increases.

Fig. 7.

Shear stress-shear displacement curves for five reinforced loesses under four normal stresses (50, 100, 200, 300 kPa) at 92% compaction degree: (a) 0.15% reinforcement ratio; (b) 0.2% reinforcement ratio; (c) 0.25% reinforcement ratio; (d) 0.3% reinforcement ratio; and (e) 0.35% reinforcement ratio.

Figure 8 shows shear strength versus normal shear for reinforced loesses at five compaction degrees. The data points for each compaction degree and each reinforcement ratio in Fig. 8 are fitted using a linear line. The fitting results are satisfactory. At each compaction degree, the fitting lines for the shear strength of reinforced loess are located above the fitting line for unreinforced loess. This indicates that CHFs, as a natural reinforcing material, have the effect of improving loess properties.

Fig. 8.

Shear strength versus normal stress for reinforced loesses at five compaction degrees: (a) 92% compaction degree; (b) 94% compaction degree; (c) 96% compaction degree; (d) 98% compaction degree; and (e) 100% compaction degree.

Vertical displacement-shear displacement curves of unreinforced loess

Figure 9 shows vertical displacement-shear displacement curves for unreinforced loesses under four normal stresses at three compaction degrees. As the shear displacement increases, the vertical displacement first increases in one direction (positive or negative) and then tends to stabilize. For a 92% compaction degree, the vertical displacement of unreinforced loess under normal stress of 50 or 100 kPa is positive, indicating that the loess undergoes shear expansion. In contrast, the vertical displacement under normal stress of 200 or 300 kPa is negative, indicating that the loess undergoes shear contraction. Loess with a 96% compaction degree exhibits similar patterns. These results indicate that unreinforced loess gradually changes from shear expansion to shear contraction as the normal stress increases. As shown in Fig. 9, for the same normal stress of 200 kPa, the vertical displacement at the compaction degree of 92% or 96% is negative, while the vertical displacement at the compaction degree of 100% is positive. This phenomenon indicates that loess with a high compaction degree tends to exhibit shear expansion.

Fig. 9.

Vertical displacement-shear displacement curves for unreinforced loesses under four normal stresses (50, 100, 200, 300 kPa) at three compaction degrees: (a) 92% compaction degree; (b) 96% compaction degree; and (c) 100% compaction degree.

Vertical displacement-shear displacement curves of reinforced loess

Figures 10, 11 and 12 show vertical displacement-shear displacement curves for five reinforced loesses under four normal stresses (50, 100, 200, 300 kPa) at three compaction degrees. For the compaction degrees of 92% and 96% (Figs. 10 and 11), the curves of the five reinforced loesses with different reinforcement ratios show consistent patterns. As the shear displacement increases, the vertical displacement first increases in one direction (positive or negative) and then tends to stabilize. The vertical displacement under normal stress of 50 or 100 kPa is positive, indicating that the loess undergoes shear expansion. In contrast, the vertical displacement under normal stress of 200 or 300 kPa is negative, indicating that the loess undergoes shear contraction.

Fig. 10.

Vertical displacement-shear displacement curves for five reinforced loesses under four normal stresses (50, 100, 200, 300 kPa) at 92% compaction degree: (a) 0.15% reinforcement ratio; (b) 0.2% reinforcement ratio; (c) 0.25% reinforcement ratio; (d) 0.3% reinforcement ratio; and (e) 0.35% reinforcement ratio.

Fig. 11.

Vertical displacement-shear displacement curves for five reinforced loesses under four normal stresses (50, 100, 200, 300 kPa) at 96% compaction degree: (a) 0.15% reinforcement ratio; (b) 0.2% reinforcement ratio; (c) 0.25% reinforcement ratio; (d) 0.3% reinforcement ratio; and (e) 0.35% reinforcement ratio.

Fig. 12.

Vertical displacement-shear displacement curves for five reinforced loesses under four normal stresses (50, 100, 200, 300 kPa) at 100% compaction degree: (a) 0.15% reinforcement ratio; (b) 0.2% reinforcement ratio; (c) 0.25% reinforcement ratio; (d) 0.3% reinforcement ratio; and (e) 0.35% reinforcement ratio.

For the compaction degree of 100% (Fig. 12), the curves of the five reinforced loesses with different reinforcement ratios show consistent patterns. For the normal stress of 50 or 100 kPa, as the shear displacement increases, the vertical displacement along the positive direction first increases and then tends to stabilize, indicating that the loess undergoes shear expansion. For the normal stress of 300 kPa, as the shear displacement increases, the vertical displacement along the negative direction first increases and then tends to stabilize, indicating that the loess undergoes shear contraction. For the normal stress of 200 kPa, as the shear displacement increases, the vertical displacement first increases along the negative direction and then increases along the positive direction to a positive value, indicating that the loess first undergoes shear contraction and then shear expansion.

Shear strength analysis of reinforced loess

Effect of compaction degree on the shear strength of unreinforced loess

Figure 13 shows shear strength versus compaction degree for unreinforced loess under four normal stresses (50, 100, 200, 300 kPa). All four curves in Fig. 13 show that the shear strength of loess generally increases with increasing compaction degree under the same normal stress. When the normal stress is 50 kPa, the shear strength increases from 51.578 to 57.449 kPa as the compaction degree increases from 92 to 100%. When the normal stress is 300 kPa, the shear strength increases from 152.073 to 173.806 kPa as the compaction degree increases from 92 to 100%. This occurs because the increase in compaction degree reduces the pores in the soil mass. The contact between soil particles becomes more compact, thus increasing the shear strength of the soil mass. As shown in Fig. 13, it is expected that the shear strength of the soil increases as the normal stress increases for the same compaction degree.

Fig. 13.

Shear strength versus compaction degree for unreinforced loesses under four normal stresses (50, 100, 200, 300 kPa).

Cohesion and friction angle versus compaction degree for unreinforced loess are shown in Fig. 14. As the compaction degree increases from 92 to 100%, the cohesion increases from 32.852 to 36.475 kPa, with an increase of about 11.03%. As the compaction degree increases from 92 to 100%, the friction angle increases from 21.9º to 24.74º, with an increase of about 12.97%. These occur because the increase in compaction degree reduces the pore space in the soil mass, thus causing closer contact of the soil particles. The occlusion and association between the soil particles become stronger, so the cohesion and friction angle increase.

Fig. 14.

Cohesion and friction angle versus compaction degree for unreinforced loesses.

Effect of compaction degree on the shear strength of reinforced loess

For five different reinforcement ratios, the shear strength-compaction degree curves of reinforced loesses show generally consistent patterns. Therefore, the shear strength-compaction degree curves for 0.3% reinforcement ratio are presented as representative, as shown in Fig. 15. The pattern of the effect of compaction degree on the shear strength of reinforced loess is similar to that of unreinforced loess. All four curves in Fig. 15 show that the shear strength of loess generally increases with increasing compaction degree under the same normal stress. This occurs because CHFs are in closer contact with the soil particles as a result of the increase in compaction degree. In addition, the higher compaction degree requires more compaction work to be applied when making samples. The more compaction work can increase the friction surface between the CHFs and soil particles, thus increasing the shear strength of reinforced soils.

Fig. 15.

Shear strength versus compaction degree for reinforced loesses (0.3% reinforcement ratio) under four normal stresses (50, 100, 200, 300 kPa).

Cohesion and friction angle versus compaction degree for reinforced loess are shown in Fig. 16. The effect of compaction degree on the cohesion of reinforced loess is significant. The cohesion of the reinforced loess increases from 44.621 kPa to 55.890 kPa with an increase in compaction degree from 92 to 100%, which is an increase of about 25.25%. As shown in Fig. 16, compared with the effect of the compaction degree on the cohesion, the compaction degree has a smaller effect on the friction angle of reinforced loess. Specifically, the difference between the maximum and minimum friction angles for different compaction degrees is only 1.5°.

Fig. 16.

Cohesion and friction angle versus compaction degree for reinforced loesses.

Effect of reinforcement ratio on the shear strength of reinforced loess

Figure 17 shows the shear strength versus reinforcement ratio for reinforced loesses at five compaction degrees. As the reinforcement ratio increases, the shear strength of loess generally increases first and then decreases. The peak point of shear strength generally corresponds to a reinforcement ratio of 0.3%, indicating that the optimal reinforcement ratio is 0.3%. However, the shear strength-reinforcement ratio curves at 98% compaction degree (200 kPa and 300 kPa normal stresses) and 100% compaction degree (300 kPa normal stress) are exceptions. The shear strength of these three curves generally continues to increase, indicating that the optimal reinforcement ratio will increase under high compaction degree and high normal stress. This result may be because high compaction and high normal stress can optimize the spatial distribution of fibers. Another possible reason is that high compaction energy can increase the contact area between fibers and loess. This experimental finding indicates that increasing the compaction degree of CHF-reinforced loess is conducive to the reinforcing effect of CHFs.

Fig. 17.

Shear strength versus reinforcement ratio for reinforced loesses at five compaction degrees: (a) 92% compaction degree; (b) 94% compaction degree; (c) 96% compaction degree; (d) 98% compaction degree; and (e) 100% compaction degree.

Shear strength parameters versus reinforcement ratio for reinforced loess at five compaction degrees are shown in Fig. 18. As the reinforcement ratio increases, the cohesion of loess generally increases first and then decreases. The peak point of shear strength generally corresponds to a reinforcement ratio of 0.3%. In general, the cohesion of the reinforced loess is much higher than that of the unreinforced loess, even for the lowest reinforcement ratio of 0.15%. In contrast, for highly compacted loess (98% and 100% compaction degrees), CHF reinforcement does not significantly increase the friction angle. For low-compacted loess (92% and 94% compaction degrees), a small amount of reinforcement (0.15% reinforcement ratio) can significantly increase the friction angle. However, further increasing the reinforcement ratio does not significantly increase the friction angle. This occurs because the friction angle between soil particles and CHFs may not be significantly greater than that between soil particles themselves.

Fig. 18.

Shear strength parameters versus reinforcement ratio for reinforced loess at five compaction degrees: (a) cohesion versus reinforcement ratio and (b) friction angle versus reinforcement ratio.

Deformation analysis of reinforced loess

Effect of compaction degree on the vertical displacement of reinforced loess

The vertical displacement at sample failure (VDASF) is selected as the object of analysis. The point of sample failure corresponds to a shear displacement of 4 mm. The VDASF of reinforced loesses under three compaction degrees is compared, as shown in Fig. 19. For the normal stress of 50 or 100 kPa, the positive VDASF increases with increasing compaction degree when the reinforcement ratio is the same. For the normal stress of 200 kPa, the VDASF changes from negative to positive as the compaction degree increases. For the normal stress of 300 kPa, the absolute value of the negative VDASF decreases as the compaction degree increases. These results indicate that as the compaction degree increases, the shear expansion phenomenon becomes more significant, or the shear contraction phenomenon becomes less significant. This occurs because highly compacted reinforced loess is more prone to volume expansion when subjected to shear disturbance.

Fig. 19.

The VDASF for five reinforced loesses under four normal stresses (50, 100, 200, 300 kPa) at three compaction degrees. In the legend, k and J represent compaction degree and reinforcement ratio, respectively.

Effect of reinforcement ratio on the vertical displacement of reinforced loess

For the normal stress of 50 or 100 kPa, the positive VDASF decreases with increasing reinforcement ratio when the compaction degree is the same, as shown in Fig. 19. For the normal stress of 200 kPa, the absolute value of positive or negative VDASF decreases with increasing reinforcement ratio when the compaction degree is the same. For the normal stress of 300 kPa, the absolute value of negative VDASF decreases with increasing reinforcement ratio. In general, the shear expansion or shear contraction phenomenon becomes less significant as the reinforcement ratio increases. These results indicate that increasing the reinforcement ratio within the effective range can suppress the deformation of loess. An increase in the reinforcement ratio not only increases the contact area between the soil and CHF but also enhances the interlocking force and friction between soil particles, making it more difficult for relative displacement to occur between soil particles.

Conclusions

This study measured and analyzed the shear strength and deformation of CHF-reinforced loesses with five reinforcement ratios, five compaction degrees, and four normal stresses. This study provides theoretical support for the use of corn husk to reinforce loess. The main findings were as follows:

1. For the reinforced loess, the shear stress-shear displacement curve changes from strain softening to strain hardening with the increasing normal stress. The cohesion of reinforced loess increases from 44.621 kPa to 55.890 kPa with an increase in compaction degree from 92 to 100%. Compared with the effect of the compaction degree on the cohesion, the compaction degree has a smaller effect on the friction angle of reinforced loess.

2. The cohesion of the reinforced loess is much higher than that of the unreinforced loess, even for the lowest reinforcement ratio of 0.15%. In contrast, CHF reinforcement does not significantly increase the friction angle. The optimal reinforcement ratio is typically 0.3%. However, the optimal reinforcement ratio will increase under high compaction degree and high normal stress.

3. Generally, as the shear displacement increases, the vertical displacement first increases in one direction (positive or negative) and then tends to stabilize. However, for the reinforced loess at 100% compaction degree under the normal stress of 300 kPa, as the shear displacement increases, the vertical displacement first increases along the negative direction and then increases along the positive direction to a positive value, indicating that the loess first undergoes shear contraction and then shear expansion.

4. As the compaction degree of reinforced loess increases, the shear expansion phenomenon becomes more significant, or the shear contraction phenomenon becomes less significant. The shear expansion or shear contraction phenomenon becomes less significant as the reinforcement ratio increases, indicating that increasing the reinforcement ratio within the effective range can suppress the deformation of loess.

Author contributions

Yujiao Kang: Writing–original draft, Methodology, Investigation, Resources. Yi Yang: Funding acquisition, Visualization, Validation. Huailin Chen: Writing–Review & Editing, Visualization, Formal analysis. Zhe Zhang: Validation, Formal analysis.

Funding

This work was supported by the Talent Research Initiation Fund Program of China Three Gorges University (2024RCKJ100) and Major Special Project of Metallurgical Corporation of China Ltd. (CMST [2023] No. 5 − 4).

Data availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.