Biochar-polyacrylamide-straw fiber composite soil stabilizer, its application in cold region forest highway subgrade and corresponding subgrade structure
By using a biochar-polyacrylamide-straw fiber composite soil stabilizer, the freeze-thaw stability and engineering performance of the roadbed for forest highways in cold regions have been solved. This has achieved the eco-friendliness and adaptability of a highly efficient stabilizer, and improved the mechanical properties and water stability of the roadbed.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIJING UNIV
- Filing Date
- 2026-02-10
- Publication Date
- 2026-06-12
AI Technical Summary
The subgrade soil of forest highways in cold regions has poor engineering performance and low freeze-thaw stability. Existing inorganic stabilizers have problems such as high energy consumption, large carbon emissions, poor freeze-thaw resistance and ecological damage. Traditional organic amendments are not adaptable enough to cold regions and cannot balance engineering stability and ecological protection.
A composite soil stabilizer consisting of biochar, polyacrylamide, and straw fiber is used to improve the subgrade soil of forest highways in cold regions through a triple synergistic mechanism of filling, cementing, and reinforcement. Biochar filling increases compaction, polyacrylamide forms a cementing layer, and straw fiber constructs a reinforcing network, forming a high-strength and high-integrity soil structure, which synergistically improves mechanical properties and water stability.
It significantly enhances the compressive strength and shear resistance of the roadbed, improves water stability, reduces frost heave and crack propagation, and balances ecological friendliness and economy, adapting to complex climatic conditions in cold regions.
Smart Images
Figure CN122188665A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of road engineering materials technology, and relates to roadbed stabilizers, specifically to a biochar-polyacrylamide-straw fiber composite soil stabilizer, its application in the roadbed of forest highways in cold regions, and the corresponding roadbed structure. Background Technology
[0002] In the construction of forest highways in cold regions, the core problems of roadbed soil generally include poor engineering performance and low freeze-thaw stability. Specifically, the soil has insufficient compressive strength and weak shear strength. After freeze-thaw cycles, the strength loss rate is high, which can easily lead to roadbed frost heave cracking, slope collapse and other diseases, which seriously affect the service life of the road and traffic safety.
[0003] Current traditional technologies for roadbed stabilization mainly rely on inorganic stabilizers such as cement and lime. Although they can improve soil strength in the short term, they have significant drawbacks: First, the production process of these materials is energy-intensive and has a large carbon emission, which is contrary to the concept of "green infrastructure" and can easily lead to soil compaction and damage the surrounding forest ecosystem. Second, their freeze-thaw resistance is poor. Under repeated freeze-thaw conditions in cold regions, the soil is prone to secondary cracking, requiring frequent maintenance and increasing engineering costs.
[0004] Among existing soil conditioner research, polyacrylamide (PAM) has received widespread attention as a commonly used organic conditioner. For example, foreign studies have demonstrated that PAM can increase the contact area between soil particles, improve cohesion, and enhance shear strength by adding PAM to a vetiver system to improve unsaturated soil. In China, Gao Feng, using purple soil from the Three Gorges Reservoir area as a research subject, found that the amount of PAM applied and the soil separation capacity showed a "decreasing then increasing" relationship. However, the use of PAM alone has obvious limitations: under the complex climate and topography conditions of cold regions, its improvement effect lacks persistence and adaptability, and long-term application may have potential impacts on the local microenvironment; moreover, the high viscosity of PAM easily leads to uneven distribution in the soil, with the improvement effect concentrated in the surface layer, and the improvement of deep soil strength is not significant, which cannot meet the overall stability requirements of roadbeds in cold regions.
[0005] Furthermore, existing improvement technologies often focus on enhancing a single performance aspect (such as compressive strength or erosion resistance), lacking a comprehensive consideration of "mechanical properties, freeze-thaw resistance, and ecological compatibility." Forest highways in cold regions have dual requirements for "engineering stability" and "ecological protection." Traditional technologies struggle to balance soil reinforcement with the maintenance of vegetation growth environments, necessitating the development of a composite improvement technology that combines high efficiency, stability, environmental friendliness, and ecological adaptability. Summary of the Invention
[0006] The purpose of this invention is to provide a biochar-polyacrylamide-straw fiber composite soil stabilizer, its application in the subgrade of forest highways in cold regions, and the corresponding subgrade structure. The subgrade soil of forest highways in cold regions improved by using the biochar-polyacrylamide-straw fiber composite soil stabilizer of this invention has significantly improved mechanical properties, freeze-thaw resistance and water stability. It is environmentally friendly and ecologically compatible, and has low cost and high applicability.
[0007] This invention is achieved through the following technical solution: A biochar-polyacrylamide-straw fiber composite soil stabilizer, the raw materials of which include 75%-85% biochar, 5%-10% polyacrylamide and 5%-15% straw fiber by mass.
[0008] The present invention also has the following technical features: Preferably, the polyacrylamide has an average molecular weight of 12 million.
[0009] Preferably, the straw fiber is wheat straw fiber, with a length of 18-22 mm, a width of 2-3 mm, and a thickness of 0.5-0.7 mm.
[0010] This invention also protects the application of the biochar-polyacrylamide-straw fiber composite soil stabilizer as described above in the subgrade construction of forest highways in cold regions, wherein the biochar-polyacrylamide-straw fiber composite soil stabilizer is added at a ratio of 2%-4% of the quality of the soil to be improved.
[0011] Preferred methods for stabilizing soil in the subgrade construction of forest highways in cold regions include the following steps: Step 1: Cut soil samples along the vertical profile at the roadbed sampling point, keeping the original soil structure intact. Crush, air dry, and then pass through a 2mm sieve. Dry the soil for later use. Step 2: Weigh out biochar, polyacrylamide and dry soil sample according to the mass ratio, mix them evenly, add distilled water to adjust to the optimal moisture content of 20%, and finally add straw fiber and stir for 3-5 minutes. Step 3: Fill the mixture into a mold with a height of 10-120cm in layers, and compact each layer to the target dry density of 1.50-1.55 g / cm³. 3 Each layer is roughened after compaction to ensure tight bonding between layers; Step 4: Seal the compacted sample and cure it in a constant temperature and humidity environment of 20℃ and 95% for 28 days until the cementation reaction is fully completed and a stable subgrade soil structure is formed.
[0012] The present invention also protects a subgrade structure for a forest highway in cold regions, comprising, from top to bottom, a surface layer with a thickness of 10-30cm, a middle layer with a thickness of 30-80cm, and a bottom subgrade soil structure with a thickness of 80-120cm. The surface, middle, and bottom subgrade soil structures are prepared according to the method described in claim 5 or 6.
[0013] Preferably, the amount of straw fiber added to the surface subgrade soil structure is greater than 0.3%; The biochar added to the underlying subgrade soil structure is greater than 3% by weight.
[0014] Compared with the prior art, the present invention has the following advantages: The biochar-polyacrylamide-straw fiber (BPS) composite stabilizer of this invention addresses the core pain points of loess roadbeds in cold-region forest highways—namely, weak mechanical bearing capacity, easy disintegration upon contact with water, and easy failure due to freeze-thaw cycles—through a triple synergistic mechanism of "filling-cementing-reinforcing." It achieves a synergistic improvement in mechanical properties, water stability, and freeze-thaw resistance, while also taking into account eco-friendliness and economy. It meets the multiple requirements of cold-region forest highways—namely, "engineering stability, ecological protection, and cost control"—and has the potential for large-scale promotion. On the one hand, biochar fills the gaps in the soil, reducing porosity and increasing density; polyacrylamide forms a stable cementing layer with the hydroxyl groups of soil particles through long-chain molecules, enhancing particle adhesion; straw fiber constructs a three-dimensional reinforcing network to resist soil shear deformation. The three work synergistically to form a high-strength, high-integrity soil structure of "density-bonding-shear resistance". Under the conditions of 3% admixture and 28 days of curing, the unconfined compressive strength (UCS) of the improved soil reaches 565.42 kPa, which is 3.36 times that of the untreated soil, and the deformation modulus increases to 17.24 MPa, which is 6.05 times that of the untreated soil. It can effectively resist the compressive deformation caused by vehicle load and roadbed self-weight. After 14 days of curing, the internal friction angle increases from 21.65° of the original soil to 31.06°, and the cohesion increases from 13.07 kPa to 23.25 kPa, which significantly enhances the shear resistance of the roadbed and avoids diseases such as slope collapse and roadbed sliding. On the other hand, the porous structure of biochar forms a "micro-water storage-slow release" system, reducing rapid water infiltration and softening; the polyacrylamide cementing layer resists particle stripping caused by water, preventing soil dispersion; the three-dimensional network of straw fibers blocks soil particle loss, inhibits the expansion of scour cracks, and at the same time improves the soil permeability coefficient and enhances water retention capacity, achieving a balance between "water blocking and foundation stabilization" and "water conservation and soil protection". In response to the problem of roadbed water damage caused by "rainy summers and snow melting in spring" in cold regions, the water stability is improved through the synergistic effect of "water blocking-bonding-erosion resistance". Meanwhile, the pores of biochar can buffer the volumetric stress generated by the expansion of water during freezing, reducing the damage of ice crystals to the soil structure; the polyacrylamide cementing layer reduces the fluctuation of soil moisture content and inhibits frost heave caused by water migration; the straw fiber reinforcement effect blocks the expansion of freeze-thaw microcracks, preventing crack penetration and overall instability, forming a "freeze-crack-stabilized structure" protection system. Attached Figure Description
[0015] Figure 1 Photographs of soil lining and maintenance after adding biochar-polyacrylamide-straw fiber composite soil stabilizer for the invention; Figure 2 Comparison of simulated rainfall erosion test results between untreated loess slopes and improved loess slopes in Examples 6-8 and Comparative Example 1; Figure 3 The graph shows a comparison of the moisture content of untreated soil with that of the improved soil in Examples 6-8 and Comparative Example 1. Detailed Implementation
[0016] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.
[0017] The biochar used in the following examples was wheat straw biochar, with a pH of 7.9 and a specific gravity of 1.82 g / cm³. 3 Bulk density 0.5 g / cm³ 3 Intergranular porosity is 49.1%.
[0018] The polyacrylamide used has an average molecular weight of 12 million.
[0019] The straw fiber used is wheat straw fiber, with a length of 18-22mm, a width of 2-3mm, and a thickness of 0.5-0.7mm.
[0020] Example 1 This embodiment provides a biochar-polyacrylamide-straw fiber composite soil stabilizer, the raw materials of which include 75% biochar, 10% polyacrylamide and 15% straw fiber by mass.
[0021] Example 2 This embodiment provides a biochar-polyacrylamide-straw fiber composite soil stabilizer, the raw materials of which include 85% biochar, 5% polyacrylamide and 10% straw fiber by mass.
[0022] Example 3 This embodiment provides a biochar-polyacrylamide-straw fiber composite soil stabilizer, the raw materials of which include 82% biochar, 10% polyacrylamide and 8% straw fiber by mass.
[0023] Example 4 This embodiment provides a biochar-polyacrylamide-straw fiber composite soil stabilizer, the raw materials of which include 80% biochar, 8% polyacrylamide and 12% straw fiber by mass.
[0024] Example 5 This embodiment provides a biochar-polyacrylamide-straw fiber composite soil stabilizer, the raw materials of which include 85% biochar, 10% polyacrylamide and 5% straw fiber by mass.
[0025] Example 6 This embodiment provides a method for stabilizing soil in the subgrade construction of forest highways in cold regions. The method involves adding the biochar-polyacrylamide-straw fiber composite soil stabilizer, as described in Example 1, at a ratio of 2% of the soil mass to be improved. The method includes the following steps: Step 1: Cut soil samples along the vertical profile at the roadbed sampling point, keeping the original soil structure intact. Crush, air dry, and then pass through a 2mm sieve. Dry the soil for later use. Step 2: Weigh out biochar, polyacrylamide and dried soil sample according to the mass ratio, mix them evenly, add distilled water to adjust to the optimal moisture content of 20%, and finally add straw fiber and stir for 3 minutes. Step 3: Fill the mixture into a mold with a height of 120cm in layers, and compact each layer until the target dry density of 1.55 g / cm³ is reached. 3 Each layer is roughened after compaction to ensure tight bonding between layers; Step 4: Seal the compacted sample and cure it in a constant temperature and humidity environment of 20℃ and 95% for 28 days until the cementation reaction is fully completed and a stable subgrade soil structure is formed.
[0026] Example 7 This embodiment provides a method for stabilizing soil in the subgrade construction of forest highways in cold regions. The method involves adding the biochar-polyacrylamide-straw fiber composite soil stabilizer, as described in Example 2, at a ratio of 4% of the soil mass to be improved. The method includes the following steps: Step 1: Cut soil samples along the vertical profile at the roadbed sampling point, keeping the original soil structure intact. Crush, air dry, and then pass through a 2mm sieve. Dry the soil for later use. Step 2: Weigh out biochar, polyacrylamide and dry soil sample according to the mass ratio, mix them evenly, add distilled water to adjust to the optimal moisture content of 20%, and finally add straw fiber and stir for 5 minutes. Step 3: Fill the mixture into a mold with a height of 10cm in layers, and compact each layer until the target dry density of 1.50 g / cm³ is reached. 3 Each layer is roughened after compaction to ensure tight bonding between layers; Step 4: Seal the compacted sample and cure it in a constant temperature and humidity environment of 20℃ and 95% for 28 days until the cementation reaction is fully completed and a stable subgrade soil structure is formed.
[0027] Example 8 This embodiment provides a method for stabilizing soil in the subgrade construction of forest highways in cold regions. The method involves adding the biochar-polyacrylamide-straw fiber composite soil stabilizer, as described in Example 3, at a ratio of 3% of the soil mass to be improved. The method includes the following steps: Step 1: Cut soil samples along the vertical profile at the roadbed sampling point, keeping the original soil structure intact. Crush, air dry, and then pass through a 2mm sieve. Dry the soil for later use. Step 2: Weigh out biochar, polyacrylamide and dried soil sample according to the mass ratio, mix them evenly, add distilled water to adjust to the optimal moisture content of 20%, and finally add straw fiber and stir for 4 minutes. Step 3: Fill the mixture into a mold with a height of 80cm in layers, and compact each layer to the target dry density of 1.52 g / cm³. 3 Each layer is roughened after compaction to ensure tight bonding between layers; Step 4: Seal the compacted sample and cure it in a constant temperature and humidity environment of 20℃ and 95% for 28 days until the cementation reaction is fully completed and a stable subgrade soil structure is formed.
[0028] The pressing and curing process is as follows Figure 1 As shown.
[0029] Example 9 This embodiment provides a subgrade structure for a forest highway in cold regions, which includes a 10cm thick surface layer, an 80cm thick middle layer, and a 120cm thick bottom subgrade soil structure from top to bottom. The surface subgrade soil structure was prepared according to the method in Example 7.
[0030] The intermediate subgrade soil structure was prepared according to the method in Example 6.
[0031] The subgrade soil structure was prepared according to the method in Example 7.
[0032] Example 10 This embodiment provides a subgrade structure for a forest highway in cold regions, which includes a 30cm thick surface layer, a 30cm thick middle layer, and an 80cm thick bottom subgrade soil structure from top to bottom. The surface subgrade soil structure was prepared according to the method in Example 7.
[0033] The intermediate subgrade soil structure was prepared according to the method in Example 6.
[0034] The subgrade soil structure was prepared according to the method in Example 7.
[0035] Example 11 This embodiment provides a subgrade structure for a forest highway in cold regions, which includes a 20cm thick surface layer, a 60cm thick middle layer, and a 100cm thick bottom subgrade soil structure from top to bottom. The surface subgrade soil structure was prepared according to the method in Example 7.
[0036] The intermediate subgrade soil structure was prepared according to the method in Example 8.
[0037] The subgrade soil structure was prepared according to the method in Example 6.
[0038] Comparative Example 1 This embodiment provides a method for stabilizing soil in the subgrade construction of forest highways in cold regions. The method involves adding the biochar-polyacrylamide-straw fiber composite soil stabilizer, as described in Example 3, at a ratio of 5% of the soil mass to be improved. The method includes the following steps: Step 1: Cut soil samples along the vertical profile at the roadbed sampling point, keeping the original soil structure intact. Crush, air dry, and then pass through a 2mm sieve. Dry the soil for later use. Step 2: Weigh out biochar, polyacrylamide and dry soil sample according to the mass ratio, mix them evenly, add distilled water to adjust to the optimal moisture content of 20%, and finally add straw fiber and stir for 3-5 minutes. Step 3: Fill the mixture into a mold with a height of 80cm in layers, and compact each layer to the target dry density of 1.52 g / cm³. 3 Each layer is roughened after compaction to ensure tight bonding between layers; Step 4: Seal the compacted sample and cure it in a constant temperature and humidity environment of 20℃ and 95% for 28 days until the cementation reaction is fully completed and a stable subgrade soil structure is formed.
[0039] Through simulated rainfall slope erosion tests, the phenomena of untreated plain loess slopes and material-modified loess slopes in Examples 6-8 and Comparative Example 1 were compared and observed. When subjected to 100 L / h of artificial rainfall for 40 minutes, the modified slopes did not exhibit soil erosion in the initial stage. Figure 2 As shown; in fact, after approximately 25 minutes, small erosion grooves only began to appear on the improved loess slopes in Examples 6-8, and these erosion grooves contained a relatively small number of loose soil particles. Compared with the untreated plain loess slopes, the surface erosion of the loess slopes treated with the improved materials was significantly reduced.
[0040] Disintegration tests showed that the addition of BPS effectively improved the water stability of loess, enhancing its water retention capacity and erosion resistance. At a dosage of 3%, the improved loess exhibited stronger stability under water erosion conditions, with a significantly reduced disintegration rate and a more stable soil structure. Slope erosion tests revealed significant erosion on the slope without BPS, leading to large-scale collapse at the end of the test. In contrast, the BPS-modified slope showed better erosion performance, particularly the slope with a 3% dosage exhibiting higher slope integrity after erosion. Analysis of sediment yield at different dosages showed that the optimal dosage of 3% reduced sediment yield by 53.7% compared to the unmodified slope, demonstrating that BPS effectively enhances the erosion resistance of loess slopes.
[0041] Figure 3 This is a comparison chart of the moisture content of untreated soil and the improved soil in Examples 6-8 and Comparative Example 1. Figure 3 It can be seen that when the capillary pores of loess with 0% BPS are filled with water, its moisture content is 39.26%. After evaporation at a constant temperature of 60℃ for 24 hours, the moisture content decreases to 3.06%. The moisture content of loess with added BPS changes from 42.40%~42.47% to 8.51%~10.58%, respectively. It can be seen that the addition of BPS effectively slows down the rate of water evaporation. During the evaporation process, the moisture evaporation rate of loess with 0% BPS is relatively fast, while the moisture evaporation rate of loess with added BPS is significantly slowed down, especially in the early stage of evaporation. The moisture content change curve of loess with added BPS decreases in parallel, indicating that the soil moisture loss rate is similar. However, after 7 hours of evaporation, the moisture content of loess with 0% BPS is 21.21%, while the moisture content of loess with added BPS remains between 24.05% and 30.14%. This shows that the application of BPS can effectively inhibit soil moisture evaporation during the evaporation process and prolong the soil water retention time. Further analysis showed that the 2% BPS and 3% BPS treatments were effective, maintaining moisture contents of 30.14% and 29.49% respectively, demonstrating significant water retention. This approach achieves a balance between "water-blocking and foundation stabilization" and "water retention and soil protection," addressing the problem of roadbed water damage caused by "heavy summers and snowmelt in spring" in cold regions by synergistically improving water stability through "water blocking, bonding, and erosion resistance."
Claims
1. A biochar-polyacrylamide-straw fiber composite soil stabilizer, characterized in that, The raw materials include 75%-85% biochar, 5%-10% polyacrylamide, and 5%-15% straw fiber by weight.
2. The biochar-polyacrylamide-straw fiber composite soil stabilizer according to claim 1, characterized in that, The polyacrylamide has an average molecular weight of 12 million.
3. The biochar-polyacrylamide-straw fiber composite soil stabilizer according to claim 1, characterized in that, The straw fiber is wheat straw fiber, with a length of 18-22mm, a width of 2-3mm, and a thickness of 0.5-0.7mm.
4. The application of a biochar-polyacrylamide-straw fiber composite soil stabilizer as described in any one of claims 1 to 4 in the subgrade construction of forest highways in cold regions, characterized in that, Add biochar-polyacrylamide-straw fiber composite soil stabilizer at a ratio of 2%-4% of the soil quality to be improved.
5. The application of the biochar-polyacrylamide-straw fiber composite soil stabilizer according to claim 4, characterized in that, The methods for stabilizing the soil in the subgrade construction of forest highways in cold regions include the following steps: Step 1: Cut soil samples along the vertical profile at the roadbed sampling point, keeping the original soil structure intact. Crush, air dry, and then pass through a 2mm sieve. Dry the soil for later use. Step 2: Weigh out biochar, polyacrylamide and dry soil sample according to the mass ratio, mix them evenly, add distilled water to adjust to the optimal moisture content of 20%, and finally add straw fiber and stir for 3-5 minutes. Step 3: Fill the mixture into a mold with a height of 10-120cm in layers, and compact each layer to the target dry density of 1.50-1.55g / cm³. 3 Each layer is roughened after compaction to ensure tight bonding between layers; Step 4: Seal the compacted sample and cure it in a constant temperature and humidity environment of 20℃ and 95% for 28 days until the cementation reaction is fully completed and a stable subgrade soil structure is formed.
6. A roadbed structure for a cold-region forest highway, characterized in that, From top to bottom, it includes a surface layer of 10-30cm thickness, a middle layer of 30-80cm thickness, and a bottom layer of 80-120cm thickness for the subgrade soil structure. The aforementioned surface, middle, and bottom subgrade soil structures Prepared according to the method described in claim 4 or 5.
7. The subgrade structure of the cold-region forest highway according to claim 6, characterized in that, The amount of straw fiber added to the surface subgrade soil structure is greater than 0.3%; The biochar added to the underlying subgrade soil structure is greater than 3% by weight.