Freeze-thaw resistant solidified silt, method for its production and use

Abstract

This invention belongs to the field of silt solidification technology, specifically relating to a freeze-thaw resistant solidified silt, its preparation method, and its application. The freeze-thaw resistant solidified silt is made from the following raw materials in parts by weight: 84.4 to 90.8 parts silt, 0.2 to 0.6 parts fiber material, and 9 to 15 parts industrial solid waste. The total amount of silt, fiber material, and industrial solid waste is 100 parts. The silt has a plasticity index of 10 to 27 and a particle size of less than 2 mm. The fiber material is selected from any one of basalt fiber, alkali-resistant glass fiber, polypropylene fiber, and polyester fiber. The industrial solid waste is selected from any one of fly ash, blast furnace slag powder, and coal gangue powder. With increasing freeze-thaw cycles, the deviatoric stress of the solidified silt gradually weakens, and the decrease in peak deviatoric stress tends to level off, becoming gradual after 7 freeze-thaw cycles.

Description

Technical Field

[0001] This invention belongs to the field of solidified silt technology, specifically relating to a freeze-thaw resistant solidified silt, its preparation method, and its application. Background Technology

[0002] Silt is a common low-plasticity soil with unique engineering properties, frequently found in roadbeds in Northeast China. Under the coupled effects of vehicle dynamic loads and freeze-thaw cycles, silt is highly susceptible to frost heave and frost heave. In dry weather, silt easily generates dust, and after being soaked by rainwater, it is prone to liquefaction. In areas with deep seasonal freezing and permafrost, frost heave and thaw settlement damage are particularly significant in engineering projects, making silt unsuitable for direct roadbed filling.

[0003] Existing methods for solidifying silty soil include inorganic solidification using cement and lime, composite solidification using cement and active minerals, and alkali-activated solidification. Among these, cement-lime solidified silty soil exhibits significant drying and thermal shrinkage, is prone to micro-cracks, and shows a marked decrease in strength after long-term freeze-thaw cycles. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a freeze-thaw resistant solidified silt, its preparation method, and its application.

[0005] The first objective of this invention is to provide a freeze-thaw resistant solidified silt, made from the following raw materials in parts by weight: 84.4 to 90.8 parts silt, 0.2 to 0.6 parts fiber material, and 9 to 15 parts industrial solid waste.

[0006] The total amount of the silt, fiber materials and industrial solid waste is 100 parts.

[0007] The silt has a plasticity index of 10-27 and a particle size of less than 2 mm, and is obtained by crushing natural silt lumps. When the plasticity index of the silt is 10-17, the silt content is greater than 60% and the clay content is less than 30%. When the plasticity index of the silt is 17-27, the clay content is less than 40%.

[0008] The fiber material is selected from any one of basalt fiber, alkali-resistant glass fiber, polypropylene fiber, and polyester fiber.

[0009] The industrial solid waste is selected from any one of fly ash, blast furnace slag powder, and coal gangue powder.

[0010] Preferably, the silt consists of 87.6 parts, the fiber material consists of 0.4 parts, and the industrial solid waste consists of 12 parts.

[0011] Preferably, the fiber material has a diameter of 20μm to 25μm, a length of 6mm to 12mm, a tensile strength of 3000MPa to 3800MPa, and an elastic modulus of 90GPa to 110GPa.

[0012] Preferably, the diameter of the fiber material is 20.33 μm.

[0013] Preferably, the fly ash is Grade I fly ash with SiO2 content ≥50% and loss on ignition ≤3%.

[0014] The second objective of this invention is to provide a method for preparing freeze-thaw resistant solidified silt, comprising the following steps: mixing 84.4 to 90.8 parts of silt, 0.2 to 0.6 parts of fiber material and 9 to 15 parts of industrial solid waste evenly to obtain freeze-thaw resistant solidified silt.

[0015] A third objective of this invention is to provide an application of freeze-thaw resistant solidified silt, comprising at least one of the following: (1) Freeze-thaw resistant solidified silt is used for roadbed construction projects in seasonally frozen areas.

[0016] (2) Freeze-thaw resistant solidified silt is used for site paving and low plasticity soil filling projects in seasonally frozen areas.

[0017] (3) Freeze-thaw resistant solidified silt is used as backfill material for slope protection projects in seasonally frozen areas.

[0018] (4) Freeze-thaw resistant solidified silt is used for slope seepage prevention and backfilling projects of water conservancy channels in seasonally frozen areas.

[0019] Preferably, the roadbed is a road roadbed or a railway roadbed.

[0020] Preferably, the application in the roadbed construction project in the seasonally frozen zone includes the following steps: Mix the solidified silt with water at a mass ratio of 10~12:60~65, and cure at 20℃~25℃ for 24 hours. Compact the mixture in layers to the maximum dry density, with a thickness of 20cm~30cm, and compact each layer ≥8 times.

[0021] Preferably, the mass ratio of the solidified silt to water is 11:63.

[0022] Preferably, the maximum dry density is 1.59 g / cm³. 3 .

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The freeze-thaw resistant solidified silt of the present invention is made from the following raw materials in parts by weight: 84.4 to 90.8 parts silt, 0.2 to 0.6 parts fiber material, and 9 to 15 parts industrial solid waste. The total amount of the silt, fiber material, and fly ash is 100 parts. The silt has a plasticity index of 10 to 27 and a particle size of less than 2 mm. When the plasticity index of the silt is 10 to 17, the content of medium-density silt particles is greater than 60%, and the content of clay particles is less than 30%. When the plasticity index of the silt is 17 to 27, the content of clay particles is less than 40%. The fiber material is selected from any one of basalt fiber, alkali-resistant glass fiber, polypropylene fiber, and polyester fiber. The industrial solid waste is selected from any one of fly ash, blast furnace slag powder, and coal gangue powder. The fiber material in the freeze-thaw resistant solidified silt of this invention disperses stress concentration caused by freeze-thaw cycles through bridging, inhibiting the propagation of microcracks. Its high toughness alleviates brittle damage to the cemented structure and prevents rapid crack penetration during freeze-thaw cycles. Industrial solid waste can generate CSH and CAH cementing products through volcanic ash reaction, filling the pores between silt particles and significantly reducing free water content. Therefore, the freeze-thaw resistant solidified silt of this invention, through the synergistic effect of silt, industrial solid waste, and fiber material, reduces water heave during frost and improves the crack resistance of the structure, thereby effectively resisting freeze-thaw damage. It has excellent freeze-thaw resistance characteristics, and its physical properties tend to stabilize after seven consecutive freeze-thaw cycles, making it suitable for use in seasonally frozen areas.

[0024] The industrial solid waste of this invention weakens the driving force of "ice expansion and thawing contraction" in freeze-thaw cycles at its source. On the other hand, the cementitious products generated by the industrial solid waste can improve the bonding strength between particles and enhance the initial stability of the soil skeleton. In silt, the synergistic effect of industrial solid waste and fiber materials reduces frost heave water and improves the crack resistance of the structure, thus effectively resisting freeze-thaw damage. Excessive industrial solid waste content leads to excessive cementitious products, increasing the brittleness of the solidified silt and making it more prone to cracking under freeze-thaw stress. Insufficient content results in insufficient bonding, high porosity, and high free water content, significantly increasing the risk of frost heave; therefore, the industrial solid waste content should be controlled at 9 to 15 parts. Insufficient fiber material content results in insufficient reinforcement and inability to effectively prevent cracking. Excessive content causes fiber agglomeration, forming weak areas in the structure and reducing the overall stability of the solidified silt. Therefore, the fiber material content should be controlled at 0.2 to 0.6 parts. Only when the amount of industrial solid waste is 9 to 15 parts and the amount of fiber material is 0.2 to 0.6 parts can the synergistic effect of "cementation filling - fiber crack resistance" be achieved, maximizing the freeze-thaw resistance of solidified silt.

[0025] 2. This invention prepares solidified silt using silt, basalt fiber, and fly ash as materials. Experimental results show that as the content of fiber and fly ash increases, the unconfined compressive strength of the solidified silt initially increases and then decreases. The highest unconfined compressive strength is achieved when the basalt fiber content is 0.4% and the fly ash content is 12%, representing a 993% increase compared to silt alone. This is a 610% increase compared to basalt fiber-solidified silt and a 92% increase compared to fly ash-solidified silt. With increasing freeze-thaw cycles, the deviatoric stress of the solidified silt gradually weakens, and the decrease in peak deviatoric stress becomes more gradual. The stress-strain curve of the solidified silt exhibits a strain-hardening type. Microscopic analysis reveals that fly ash fills the pores within the silt through cementation, while the addition of basalt fiber compensates for the silt's brittleness; both synergistically improve soil density. Freeze-thaw cycles damage the soil structure, and the damage intensity increases with the number of freeze-thaw cycles, gradually leveling off after seven cycles. Attached Figure Description

[0026] Figure 1 The diagram shows the unconfined compressive strength of the solidified silt prepared in Examples 1 to 9 and Comparative Examples 1 to 21 of the present invention.

[0027] Figure 2 The image shows the stress-strain curves of the solidified silt sample prepared in Example 1 of this invention under freeze-thaw cycles. Where A is 100 kPa, B is 200 kPa, C is 300 kPa, and D is 500 kPa.

[0028] Figure 3 This is a graph showing the elastic modulus of the solidified silt sample prepared in Example 1 of the present invention under freeze-thaw cycles. Wherein, A is 100 kPa, B is 200 kPa, C is 300 kPa, and D is 500 kPa.

[0029] Figure 4 Scanning electron microscope (SEM) images of the solidified silt sample prepared in Example 1 and Comparative Example 1, respectively. In this diagram, A represents Comparative Example 1, and B represents Example 1.

[0030] Figure 5 SEM images of the solidified silt sample prepared in Example 1 and the solidified silt sample prepared in Comparative Example 1 are shown. In this image, A represents Comparative Example 1, and B represents Example 1.

[0031] Figure 6 This is a diagram showing the fiber distribution morphology in the solidified silt sample prepared in Example 1 of the present invention.

[0032] Figure 7 SEM images of the solidified silt sample prepared in Example 1 of this invention after freeze-thaw cycles. In the images, A represents 0 freeze-thaw cycles, B represents 1 freeze-thaw cycle, C represents 3 freeze-thaw cycles, D represents 5 freeze-thaw cycles, and E represents 7 freeze-thaw cycles. Detailed Implementation

[0033] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the following detailed description, in conjunction with preferred embodiments and accompanying drawings, provides a clear and complete account of the technical solutions of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0035] The materials used in the embodiments and comparative examples of this invention were sourced as follows: Natural silt blocks, collected from Pingfang District, Harbin City, Heilongjiang Province, at latitude and longitude N45°36'14", E126°38'13", with physical parameters shown in Table 1. Industrial solid waste was fly ash, batch number 59205, grade I fly ash, grayish-brown in color, purchased from Yanxi Mineral Products Processing Plant, with composition shown in Table 2. Basalt fiber, metallic in color, was purchased from Jiangsu Nongchaoer Composite Materials Co., Ltd., with specifications shown in Table 3.

[0036] Table 1 Physical parameters of natural silt blocks If these natural silt blocks are used directly in roadbed and other engineering projects in Northeast China, problems such as frost heave and thaw settlement will occur.

[0037] Table 2 Composition of fly ash Table 3 Performance Indicators of Basalt Fiber The experimental method of this invention is as follows: 1. Unconfined compressive strength test Unconfined compressive strength tests were conducted on solidified silt samples using a WDW-100E microcomputer-controlled electronic universal testing machine at a test rate of 1 mm / min. During the test loading process, the test was stopped when the compressive strength dropped to 80% after exceeding the peak value. If no peak value was observed, the test was stopped when the axial strain reached 20%.

[0038] 2. Triaxial shear test This experiment used the British GDS advanced dynamic and static triaxial testing system for frozen soil, and conducted consolidation undrained tests according to the "Standard for Geotechnical Testing Methods" (GB / T 50123-2019). The solidified silt samples prepared in Example 1 were frozen in an industrial freezer at -20°C for 12 hours and thawed in a water bath at 20°C for 12 hours, constituting one freeze-thaw cycle, denoted as FT. The samples underwent 0, 1, 3, 5, 7, 10, and 15 freeze-thaw cycles. σ3 was tested using four confining pressures: 100 kPa, 200 kPa, 300 kPa, and 500 kPa. A total of 28 tests were conducted with different numbers of freeze-thaw cycles and different confining pressures, as shown in Table 4. Before the test, the samples after freeze-thaw cycles were vacuum saturated. After vacuum saturation, triaxial back pressure saturation was performed to ensure a saturation value of 90% before entering the consolidation stage. Isotropic consolidation was used during the consolidation process. Shear tests were conducted after the volume did not change within 5 minutes following 16 hours of consolidation.

[0039] Table 4 Test Conditions Example 1 The application of a freeze-thaw resistant solidified silt includes the following steps: According to the testing requirements of GB / T 50123-2019 "Standard for Geotechnical Testing Methods", the collected natural silt blocks were first dried for 24 hours, crushed, and passed through a sieve with a 2mm aperture to obtain silt. 87.6 kg of silt, 12 kg of fly ash, and 0.4 kg of basalt fiber were thoroughly dry-mixed and evenly dispersed to obtain solidified silt.

[0040] Water was sprayed onto the solidified silt to obtain a solidified slurry. The mass ratio of solidified silt to water was 11:63. The solidified slurry was stirred evenly, sealed, and cured at 24℃ for 24 hours. The cured slurry was then poured into a mold with a diameter of 39.1 mm and a height of 80 mm and compacted to a density of 1.59 g / cm³. 3 The unconfined compressive strength specimens were demolded and obtained. These specimens were then cured at 24℃ and 98% relative humidity for 7 days to obtain solidified silt specimens. The unconfined compressive strength of the obtained solidified silt specimens was 1287 kPa.

[0041] Example 2 The application of a freeze-thaw resistant solidified silt includes the following steps: According to the test requirements of GB / T 50123-2019 "Standard for Geotechnical Testing Methods", the collected natural silt blocks were first dried for 24 hours, crushed, and passed through a sieve with a 2mm aperture to obtain silt. 90.8 kg of silt, 9 kg of fly ash, and 0.2 kg of basalt fiber were thoroughly dry-mixed and evenly dispersed to obtain solidified silt.

[0042] Water was sprayed onto the solidified silt to obtain a solidified slurry. The mass ratio of solidified silt to water was 10:60. The solidified slurry was stirred evenly, sealed, and cured at 20℃ for 24 hours. The cured slurry was then poured into a mold with a diameter of 39.1 mm and a height of 80 mm and compacted to a density of 1.59 g / cm³. 3 The unconfined compressive strength specimens were obtained by demolding. These specimens were then cured at 20℃ and 98% relative humidity for 7 days to obtain solidified silt specimens. The unconfined compressive strength of the obtained solidified silt specimens was 774 kPa.

[0043] Example 3 The application of a freeze-thaw resistant solidified silt includes the following steps: According to the testing requirements of GB / T 50123-2019 "Standard for Geotechnical Testing Methods", the collected natural silt blocks were first dried for 24 hours, crushed, and passed through a sieve with a 2mm aperture to obtain silt. 84.4 kg of silt, 15 kg of fly ash, and 0.6 kg of basalt fiber were thoroughly dry-mixed and evenly dispersed to obtain solidified silt.

[0044] Water was sprayed onto the solidified silt to obtain a solidified slurry. The mass ratio of solidified silt to water was 12:65. The solidified slurry was stirred evenly, sealed, and cured at 25℃ for 24 hours. The cured slurry was then poured into a mold with a diameter of 39.1 mm and a height of 80 mm and compacted to a density of 1.59 g / cm³. 3 The sample was demolded to obtain an unconfined compressive strength specimen. The unconfined compressive strength specimen was cured for 7 days at 25℃ and 98% relative humidity to obtain a solidified silt specimen. The unconfined compressive strength of the obtained solidified silt specimen was 742 kPa.

[0045] Example 4 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 90.6 kg, fly ash to 9 kg, and basalt fiber to 0.4 kg, while all other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 1073 kPa.

[0046] Example 5 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 90.4 kg, fly ash to 9 kg, and basalt fiber to 0.6 kg, while maintaining the same conditions as in Example 1. Solidified silt and solidified silt samples were then prepared. The unconfined compressive strength of the obtained solidified silt sample was 812 kPa.

[0047] Example 6 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 87.8 kg, fly ash to 12 kg, and basalt fiber to 0.2 kg, while maintaining the same conditions as in Example 1. Solidified silt and solidified silt samples were then prepared. The unconfined compressive strength of the obtained solidified silt sample was 943 kPa.

[0048] Example 7 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 87.4 kg, fly ash to 12 kg, and basalt fiber to 0.6 kg, while maintaining the same conditions as in Example 1. Solidified silt and solidified silt samples were then prepared. The unconfined compressive strength of the obtained solidified silt sample was 992 kPa.

[0049] Example 8 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 84.8 kg, fly ash to 15 kg, and basalt fiber to 0.2 kg, while maintaining the same conditions as in Example 1. Solidified silt and solidified silt samples were then prepared. The unconfined compressive strength of the obtained solidified silt sample was 813 kPa.

[0050] Example 9 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 84.6 kg, fly ash to 15 kg, and basalt fiber to 0.4 kg, while maintaining the same conditions as in Example 1. Solidified silt and solidified silt samples were then prepared. The unconfined compressive strength of the obtained solidified silt sample was 911 kPa.

[0051] Comparative Example 1 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt weight was adjusted to 100 kg, and fly ash and basalt fiber were omitted, while all other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 182 kPa.

[0052] Comparative Example 2 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the amount of silt was adjusted to 99.8 kg and the amount of basalt fiber was adjusted to 0.2 kg. Fly ash was not used, and all other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 163 kPa.

[0053] Comparative Example 3 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the amount of silt was adjusted to 99.6 kg and the amount of basalt fiber was adjusted to 0.4 kg. Fly ash was not used, and all other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 171 kPa.

[0054] Comparative Example 4 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the amount of silt was adjusted to 99.4 kg and the amount of basalt fiber was adjusted to 0.6 kg. Fly ash was not used, and all other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 152 kPa.

[0055] Comparative Example 5 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the amount of silt was adjusted to 99.2 kg and the amount of basalt fiber was adjusted to 0.8 kg. Fly ash was not used, and all other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 121 kPa.

[0056] Comparative Example 6 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 97 kg and the fly ash to 3 kg, and basalt fiber was omitted, while all other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 236 kPa.

[0057] Comparative Example 7 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 96.8 kg, fly ash to 3 kg, and basalt fiber to 0.2 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were then prepared. The unconfined compressive strength of the obtained solidified silt sample was 394 kPa.

[0058] Comparative Example 8 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 96.6 kg, fly ash to 3 kg, and basalt fiber to 0.4 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 488 kPa.

[0059] Comparative Example 9 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 96.4 kg, fly ash to 3 kg, and basalt fiber to 0.6 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were then prepared. The unconfined compressive strength of the obtained solidified silt sample was 812 kPa.

[0060] Comparative Example 10 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 96.2 kg, fly ash to 3 kg, and basalt fiber to 0.8 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 289 kPa.

[0061] Comparative Example 11 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 94 kg and the fly ash to 6 kg, and basalt fiber was omitted, while all other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 337 kPa.

[0062] Comparative Example 12 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 93.8 kg, fly ash to 6 kg, and basalt fiber to 0.2 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 673 kPa.

[0063] Comparative Example 13 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 93.6 kg, fly ash to 6 kg, and basalt fiber to 0.4 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 862 kPa.

[0064] Comparative Example 14 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 93.4 kg, fly ash to 6 kg, and basalt fiber to 0.6 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 593 kPa.

[0065] Comparative Example 15 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 93.2 kg, fly ash to 6 kg, and basalt fiber to 0.8 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 508 kPa.

[0066] Comparative Example 16 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 91 kg and the fly ash to 9 kg, and basalt fiber was not used. All other conditions remained the same as in Example 1, resulting in solidified silt and solidified silt samples. The unconfined compressive strength of the obtained solidified silt sample was 506 kPa.

[0067] Comparative Example 17 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 90.2 kg, fly ash to 9 kg, and basalt fiber to 0.8 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 668 kPa.

[0068] Comparative Example 18 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 88 kg and the fly ash to 12 kg, and basalt fiber was omitted, while all other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 664 kPa.

[0069] Comparative Example 19 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 87.2 kg, fly ash to 12 kg, and basalt fiber to 0.8 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were then prepared. The unconfined compressive strength of the obtained solidified silt sample was 733 kPa.

[0070] Comparative Example 20 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 85 kg and the fly ash to 15 kg, and basalt fiber was not used. All other conditions remained the same as in Example 1, resulting in solidified silt and solidified silt samples. The unconfined compressive strength of the obtained solidified silt sample was 553 kPa.

[0071] Comparative Example 21 The application of a freeze-thaw resistant solidified silt includes the following steps: In Example 1, the silt was adjusted to 84.2 kg, fly ash to 15 kg, and basalt fiber to 0.8 kg, while the other conditions remained the same as in Example 1. Solidified silt and solidified silt samples were prepared. The unconfined compressive strength of the obtained solidified silt sample was 612 kPa.

[0072] I. Experimental Results 1. The relationship between the dosage of basalt fiber and fly ash and the unconfined compressive strength of solidified silt. The unconfined compressive strength of the solidified silt samples prepared in Examples 1-9 and Comparative Examples 1-21 of this invention is as follows: Figure 1As shown in the figure, the unconfined compressive strength gradually increases with the increase of fly ash content. When the fly ash content increases to 12%, the unconfined compressive strength reaches its peak value. When the fly ash content continues to increase, the unconfined compressive strength gradually decreases. This indicates that fly ash can increase the compressive strength of silty soil. The compressive strength reaches its maximum value when the fly ash content is 12%. When the fly ash content is the same, the unconfined compressive strength of the sample gradually increases with the increase of basalt fiber content. This is because basalt fiber, as an admixture, can form a network structure in the soil, making the soil more tightly connected and improving the compressive strength. When the basalt fiber content increases to 0.4%, the compressive strength reaches its peak value. However, when the basalt fiber content continues to increase, the unconfined strength gradually decreases. This is because when the fiber content exceeds the optimal admixture, the fibers inside the soil intertwine and form clumps, resulting in poor dispersibility and thus reducing the unconfined compressive strength of the solidified silty soil. When the basalt fiber content is 0.4% and the fly ash content is 12%, the unconfined compressive strength of the solidified silt is the highest, reaching 1282.1 kPa, which is about 993% higher than the compressive strength of the plain soil (117.3 kPa).

[0073] 2. Stress-strain curve analysis of solidified silt under freeze-thaw cycles The stress-strain curve of the solidified silt sample prepared in Example 1 is shown below. Figure 2As shown in the figure, the results indicate that the deviatoric stress of basalt fiber and fly ash-solidified silt increases with increasing axial strain. When the axial strain increases to 6%, the deviatoric stress stops increasing and even shows a decreasing trend due to strain hardening of the soil. In the initial stage when the axial strain is less than 3%, the deviatoric stress and axial strain have an approximately linear relationship. As the strain increases, the deviatoric stress increases rapidly. When the axial strain exceeds 3%, the deviatoric stress curve gradually approaches its peak value. After that, the deviatoric stress difference begins to decrease with increasing strain, and the stress-strain relationship exhibits strain hardening. When the number of freeze-thaw cycles remains constant, increasing the confining pressure can increase the peak deviatoric stress of the solidified silt. Under the same confining pressure, the peak deviatoric stress gradually decreases with increasing number of freeze-thaw cycles. After 7 freeze-thaw cycles, the stress-strain curve gradually stabilizes. This is because the contact between soil particles changes during the freeze-thaw cycle, which reduces the interlocking effect between particles and thus reduces the strength of the soil. With the increase of the number of freeze-thaw cycles and the confining pressure, the soil is subjected to external compression, leading to a decrease in the internal net force of the soil. Therefore, the soil's ability to resist external loads gradually decreases. During this process, the interaction and friction between soil particles induce strain hardening, resulting in an initial increase in soil strength. However, as internal damage accumulates, the final bearing capacity still tends to decrease. These results clearly demonstrate that the effects of freeze-thaw cycles and confining pressure must be carefully considered when ensuring soil stability. While the increase in initial soil strength is positive, the long-term stability of the treated soil remains a key concern.

[0074] 3. The effect of freeze-thaw cycles on the elastic modulus of solidified silt The elastic modulus of the solidified silt sample prepared in Example 1 is as follows: Figure 3As shown in the figure, the results indicate that the elastic modulus of both soil samples subjected to multiple freeze-thaw cycles and control samples not subjected to freeze-thaw cycles showed a continuous decreasing trend with increasing strain. However, due to the soil structural damage effect induced by freeze-thaw cycles, the initial values ​​and decay rates of the elastic modulus of the two samples differed significantly. The initial elastic modulus of the samples subjected to freeze-thaw cycles was significantly lower than that of the samples not subjected to freeze-thaw cycles, and under the same strain, the more freeze-thaw cycles, the greater the decrease in elastic modulus. The elastic modulus of soil is negatively correlated with the number of freeze-thaw cycles. As the number of freeze-thaw cycles increases from 0 to 15, the degree of decrease in elastic modulus with increasing strain intensifies, and the higher the stress level, the greater the decrease in the initial elastic modulus. This is because freeze-thaw cycles have a cumulative damage effect on the soil structure; the more cycles, the more significant the loss of soil strength. In terms of the mechanism of action, freeze-thaw cycles destroy the structural bonds within the soil through alternating freezing and thawing, weakening the cementing effect between the curing agent and soil particles, leading to a gradual decrease in the soil's resistance to deformation. This causes the soil to weaken more rapidly during deformation, resulting in a significant deterioration of its overall mechanical properties. Therefore, freeze-thaw cycles not only directly reduce the elastic modulus of the soil but also exacerbate the decline in mechanical properties by damaging the soil structure.

[0075] 4. Microstructure analysis To better study the macroscopic properties of solidified silt, such as plasticity index, compaction strength, and unconfined compressive strength, the microstructure of the soil was observed. The microstructure reveals the internal structure of the soil and the formation of hydration products and aggregates within it, and is also an important property for determining the physical and mechanical properties of solidified silt. Images of the solidified silt samples prepared in Example 1 and Comparative Example 1, obtained through scanning electron microscopy, are shown below. Figure 4 As shown in the figure. The results show that the soil particles in the solidified silt sample prepared in Comparative Example 1 have uneven shapes, the soil surface is filled with alternating pores and cracks, and the soil particles inside the pores are not cemented, resulting in low soil structural strength and easy failure and deformation under external loads. The solidified silt sample prepared in Example 1 has more cementing material binding the soil particles together, and the pores between particles are smaller. SEM images of the unsolidified silt and solidified silt samples prepared in Example 1 after 3 freeze-thaw cycles are shown in the figure. Figure 5As shown in the figure. The results show that after freeze-thaw cycles, the unsolidified silt produced more pores, which were densely distributed and had irregular morphology, mostly large-area interconnectedness, resulting in a relatively loose soil structure and weak interparticle connectivity. Solidified silt produced fewer pores, which were relatively sparsely distributed, mostly small-area dispersedness, resulting in a relatively dense structure, tighter interparticle connectivity, and more obvious agglomeration or cementation characteristics. The structure also experienced less freeze-thaw damage. This is because fly ash reduces soil porosity through cementation, and the filling of pores makes the connection between silt particles tighter. Basalt fibers further contribute to the formation of a more complex spatial network structure. The fiber distribution morphology of the solidified silt sample prepared in Example 1 is shown in the figure. Figure 6 As shown in the figure. The results show that basalt fibers compensate for the "brittle defects" of cemented soil, making the soil skeleton and fiber skeleton a dense whole that can jointly bear external loads. After frost heave deformation, although soil particles and fibers undergo relative deformation, the rough layered structure on the fiber surface will form interfacial friction with the surrounding soil particles, which will continuously inhibit the pore expansion caused by frost heave.

[0076] To further analyze the solidification of basalt fiber-fly ash silt under freeze-thaw cycles from a microscopic contact perspective, the solidified silt samples prepared in Example 1 were subjected to 0, 1, 3, 5, and 7 freeze-thaw cycles, followed by scanning electron microscopy (SEM) tests. The results are as follows: Figure 7 As shown in the figure. The results indicate that, compared with solidified silt that has not undergone freeze-thaw cycles, after one freeze-thaw cycle, the surface is more compact with fewer pores. With the increase of the number of freeze-thaw cycles, the surface pores of the soil become more developed, the pore expansion caused by frost heave is severe, the structure tends to be loose, and the mechanical properties continue to degrade. After seven freeze-thaw cycles, the colloid of solidified silt shows cracks, the soil cohesion decreases, and the number of flocculent polymers filling the pores decreases. In the early stage of freeze-thaw, soil particles undergo significant rearrangement due to freeze-thaw action, and the internal friction angle decreases. In the later stage of freeze-thaw, the rearrangement of soil particles weakens, and the change in the internal friction angle tends to stabilize.

[0077] II. Discussion of Results This invention investigated the unconfined compressive strength and triaxial shear test under freeze-thaw cycles of basalt fiber-fly ash solidified silt at different dosages. The effects of the dosage of the two solidifying agents on the mechanical properties of silt in Northeast China were studied. Furthermore, scanning electron microscopy (SEM) tests were conducted on solidified silt at specific dosages. The conclusions are as follows: (1) Both basalt fiber and fly ash can effectively improve the unconfined compressive strength of silt. The strength of solidified silt is higher than that of soil with single fiber admixture and soil with single fly ash admixture under the same admixture amount. The unconfined compressive strength of solidified silt increases with the increase of strain. After the compressive strength reaches the peak value, it slowly decreases with the increase of strain. The optimal admixture ratio of the two is 0.4% basalt admixture and 12% fly ash admixture.

[0078] (2) Triaxial shear tests under different confining pressure loads show that the deviatoric stress increases with the increase of axial strain, and the stress-strain relationship of solidified silt is strain hardening type. Freeze-thaw will weaken the mechanical properties of solidified silt. The more freeze-thaw cycles, the worse its properties are. After 7 freeze-thaw cycles, its mechanical properties gradually stabilize.

[0079] (3) Microscopic observation shows that basalt fiber-fly ash effectively slows down the deterioration of the mechanical properties of solidified silt. Scanning electron microscopy images show that fly ash fills the pores through cementation, and the basalt fiber network compensates for the "brittle defects" of the soil and enhances the soil integrity. Freeze-thaw cycles damage this structure, and the more cycles there are, the more the pores expand. After freeze-thaw cycles, the soil structure will not be destroyed indefinitely, but will tend to stabilize.

[0080] Fly ash, a waste product from coal combustion, is widely used in infrastructure construction such as highways and railways due to its advantages of low price, stable structure, and easy availability. The emergence of fiber reinforcement technology has provided a new approach to silty soil improvement. Basalt fiber, an inorganic fiber made from natural basalt fiber ore through high-temperature melting, drawing, and cooling, possesses excellent properties such as high tensile strength, high elastic modulus, corrosion resistance, and good chemical stability, and is widely used in civil engineering as a green industrial material. Existing technology has studied the failure morphology of basalt fiber-reinforced loess under wet-dry cycling conditions through triaxial tests. Existing technology shows that basalt fiber reinforcement significantly improves the cohesion of silty clay while having a relatively small impact on its friction angle, and all samples exhibit bulging plastic failure. Existing technology, through indoor experimental research, shows that adding basalt fiber to expansive soil subgrades can significantly enhance the strength parameters of the subgrade and improve its shrinkage performance. Based on environmental protection considerations, this invention selects basalt fiber and fly ash as improving materials. Through unconfined compressive strength tests and triaxial shear tests under freeze-thaw cycles, the reinforcement effects and influence laws of different dosages of the two materials on silty soil are compared and analyzed. Furthermore, scanning electron microscopy is used to compare and analyze the microscopic characteristics of solidified silty soil under different freeze-thaw cycles. The aim is to provide a theoretical basis for the application of basalt fiber and fly ash in silty soil subgrades.

[0081] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the inventive concept of this invention, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0082] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If such modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A freeze-thaw resistant, solidified silt, characterized in that, The solidified soil is made of the following raw materials by weight: silt 84.4-90.8 parts, fiber material 0.2-0.6 parts, and industrial solid waste 9-15 parts. The total amount of the silt, the fiber material, and the industrial solid waste is 100 parts. The silt has a plasticity index of 10-27 and a particle size of less than 2 mm, and is obtained by crushing natural silt blocks. The fiber material is selected from any one of basalt fiber, alkali-resistant glass fiber, polypropylene fiber, and polyester fiber. The industrial solid waste is selected from any one of fly ash, blast furnace slag powder, and coal gangue powder.

2. The freeze-thaw resistant, solidified silt of claim 1, wherein, The silt is 87.6 parts, the fiber material is 0.4 parts, and the industrial solid waste is 12 parts.

3. The freeze-thaw resistant, solidified silt of claim 1, wherein, The fiber material has a diameter of 20-25 μm, a length of 6-12 mm, a tensile strength of 3000-3800 MPa, and an elastic modulus of 90-110 GPa.

4. The method of claim 1, wherein the freeze-thaw resistant, solidified silt is prepared by, The method comprises the following steps: uniformly mixing 84.4-90.8 parts of silt, 0.2-0.6 parts of fiber material, and 9-15 parts of industrial solid waste to obtain solidified silt.

5. The use of the freeze-thaw resistant, solidified silt according to claim 1, characterized in that The method comprises at least one of the following: (1) the freeze-thaw resistant solidified silt is used for roadbed construction engineering in a seasonal freezing area; (2) the freeze-thaw resistant solidified silt is used for field yard and low plasticity soil filling engineering in a seasonal freezing area; (3) the freeze-thaw resistant solidified silt is used as backfill material for slope protection engineering in a seasonal freezing area; (4) the freeze-thaw resistant solidified silt is used for slope seepage prevention backfill engineering of water conservancy channels in a seasonal freezing area.

6. Use of the freeze-thaw resistant, solidified silt according to claim 5, characterized in that The roadbed is a roadbed or a railway roadbed.

7. Use of freeze-thaw resistant, solidified silt according to claim 6, characterized in that The method for the application comprises the following steps: The solidified silt and water are uniformly mixed at a mass ratio of 10-12:60-65, arranged at a target position, and cured at 20-25℃ for 24 h; and the solidified silt is layered and compacted to the maximum dry density, and the compaction times of each layer are ≥8 times.

8. Use of the freeze-thaw resistant, solidified silt according to claim 9, characterized in that The mass ratio of the solidified silt to water is 11:63.

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