Expansive soil treatment method

Abstract

The invention relates to the technical field of expansive soil treatment, in particular to an expansive soil treatment method which comprises the following steps: (1) arranging a plurality of drill holes in a to-be-treated expansive soil layer; (2) preparing a liquid curing agent; each part of the liquid curing agent is prepared from the following raw materials: 2.5 to 10ml of potassium phosphate solution, 0.02 to 0.12 g of surfactant and 2 to 8L of water; (3) the liquid curing agent obtained in the step (2) is injected into the expansive soil layer to be treated from the hole bottom upwards in a segmented mode; and (4) maintenance is conducted after grouting is completed. The method can remarkably reduce the expansibility of the soil body and improve the strength of the soil body, has the advantages of being high in adaptability, high in construction efficiency, stable in modification effect and the like, and is suitable for expansive soil treatment in various foundation projects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of swelling soil treatment, in particular to a swelling soil treatment method. BACKGROUND

[0002] Swelling soil is a special soil with significant swelling-shrinking characteristics due to high content of hydrophilic clay minerals such as montmorillonite and illite, which is widely distributed in the central and western regions and southern regions of China. The volume of swelling soil will swell or shrink dramatically with dry-wet cycles or changes in stress state. The swelling-shrinking characteristics of swelling soil have significant hazards to engineering construction: when the environmental humidity increases, the swelling of the soil body will cause the structure of roadbed, house foundation, etc. to rise or deform unevenly; when the environment is dry, the soil body will shrink and cracks will occur, and long-term repeated dry-wet cycles will exacerbate the internal structure damage of the soil body, eventually leading to engineering diseases such as road surface dislocation, bridge pile foundation cracking, house wall tilting, and even overall collapse.

[0003] In view of the hazards of swelling soil, the traditional treatment methods mainly include replacement, pre-wetting compaction and chemical solidification: the replacement method replaces the swelling soil with non-swelling soil such as sand, gravel and lime soil by excavating and replacing, which requires large-scale excavation, transportation and backfilling, has a long construction period, and the single-kilometer roadbed replacement period often lasts for several months, and has high cost, in addition, it is difficult to implement in deep swelling soil distribution areas such as 5m below the roadbed or large-area sites; the pre-wetting compaction method makes the swelling soil fully swell by adding water in advance, and then compacts to reduce the potential of swelling and shrinking in the later period, but due to the high content of clay minerals in the swelling soil, the water permeability is poor, and the water is difficult to penetrate uniformly to the deep layer, generally only affecting the surface layer of 0.5-1m, and the water addition amount is difficult to control accurately on site, resulting in limited treatment depth and effect; the chemical solidification method injects solidifying agents such as cement and lime into the swelling soil, generates cementitious materials by reaction of the solidifying agent with active minerals in the soil, improves the strength of the soil body and inhibits swelling and shrinking, but the traditional process mainly uses surface spraying or shallow drilling injection, and the injection depth is usually not more than 2m, which cannot effectively cover the deep swelling soil such as 3m below the surface, and the reaction of the solidifying agent with the deep soil is not sufficient, and it is difficult to achieve overall modification.

[0004] In recent years, liquid solidifying agents such as modified cement paste and organic polymer solidifying agents have shown potential advantages over traditional solidifying materials in ground treatment due to their good fluidity and reactivity. However, due to the limitations of the penetration ability of existing construction equipment, such as ordinary grouting pipes that can only penetrate shallow soil layers, and process limitations, such as the upward return of solidifying agents caused by the self-weight extrusion of soil, it is still difficult to effectively and uniformly deliver liquid solidifying agents to deep expansive soil, such as 5m below, by simply spraying or shallow injection, resulting in insufficient modification of deep expansive soil, which may still cause swelling and shrinking deformation due to environmental dry-wet cycles or load changes, ultimately affecting the overall stability of the project. Therefore, it is urgent to develop a new technology that can efficiently and uniformly inject liquid solidifying agents into 3-6m deep expansive soil to achieve long-term inhibition of the overall swelling and shrinking properties of expansive soil and long-term stability of the engineering structure. SUMMARY

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide an expansive soil treatment method to solve the problem of poor treatment effect of expansive soil due to the difficulty of efficiently and uniformly injecting liquid solidifying agents into 3-6m deep expansive soil.

[0006] To achieve the above-mentioned purposes and other related purposes, the present application is obtained by the following technical solutions.

[0007] The first aspect of the present application is to provide an expansive soil improver, wherein each part of the improver includes the following raw materials: 2.5-10ml of potassium phosphate solution, 0.02-0.12g of surfactant, and 2-8L of water.

[0008] The second aspect of the present application is to provide an expansive soil treatment method, comprising the following steps:

[0009] (1) arranging multiple drill holes in the expansive soil layer to be treated;

[0010] (2) configuring a liquid solidifying agent;

[0011] (3) segmentally pouring the liquid solidifying agent obtained in step (2) from the bottom of the hole upward into the expansive soil layer to be treated;

[0012] (4) curing after grouting is completed.

[0013] The third aspect of the present application is to provide the application of the expansive soil treatment method as described in the present application in the treatment of high plastic expansive soil, saline expansive soil, and high water content expansive soil.

[0014] As described above, the expansive soil treatment method of the present application has the following beneficial effects:

[0015] (1) The present invention uses a high-pressure deep grouting method to uniformly inject liquid curing agent into the interior of the expansive soil layer, thereby significantly improving the modification depth and uniformity of the expansive soil, which facilitates the improvement of foundation stability and bearing capacity, and improves the deformation of the expansive soil.

[0016] (2) In the expansive soil conditioner of the present invention, the K ions are replaced by the Al ions in the soil, thereby reducing the soil's expansive properties. The replaced Al ions react chemically with the phosphate ions in the expansive soil to form a gelling product, which effectively inhibits the expansiveness of the expansive soil.

[0017] (3) The expansive soil improvement method of the present invention can be used for the treatment of high plasticity expansive soil, saline expansive soil and high water content expansive soil. High pressure grouting reduces construction time and is suitable for large-area projects. Attached Figure Description

[0018] Figure 1 The diagram shows a flow chart of the expansive soil treatment method of the present invention.

[0019] Figure 2 The diagram shown is a structural schematic of the system used in the expansive soil treatment method of the present invention.

[0020] Figure 3 The diagram shows the structure of the grouting pipe in the system used in the expansive soil treatment method of the present invention.

[0021] Figure 4 The images shown are SEM images of the expansive soil before and after treatment in Example 1 of this invention.

[0022] Component designation explanation

[0023] 1. Grout storage tank; 2. Grouting equipment; 3. High-pressure hose; 4. Ground; 5. Grouting pipe. Detailed Implementation

[0024] To make the inventive objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. Those skilled in the art can easily understand other advantages and effects of this invention from the content disclosed in this specification.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0027] In this invention, the terms "preferredly," "more preferably," "better," and "even better" refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention. That is, in this invention, "preferredly," "more preferably," "better," and "even better" are merely descriptions of more effective implementations or examples, but do not constitute a limitation on the scope of protection of the invention.

[0028] In this invention, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0029] In this invention, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this invention, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0030] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0031] Unless otherwise specified, all steps of this invention may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0032] Unless otherwise stated, a singular term may include a plural term and should not be understood as having a quantity of one.

[0033] In this invention, "above" or "below" both include the number itself. For example, "below 1" includes 1.

[0034] In this invention, room temperature refers to 0~40°C, including but not limited to 10~40°C, or further to 20~30°C.

[0035] Traditional solidification methods (such as lime and cement) suffer from slow reaction times, poor durability, and high material consumption. Existing chemical solidifying agents (such as salts and polymers) often have shortcomings such as poor permeability and weak environmental adaptability. Therefore, there is a need to develop a liquid solidifying agent that can quickly penetrate the soil and undergo ion exchange and dissolution-precipitation reactions with active minerals in expansive soil to generate stable cementitious products, improving the soil's mechanical and durability properties. During the research process of liquid solidifying agents, it was also found that the solidifying agent's permeability was insufficient and could not act uniformly on the soil. Therefore, a high-pressure injection process was adopted to enhance penetration and diffusion. Advantages compared to existing technologies:

[0036] Convenient construction: It can be directly injected through high-pressure grouting equipment without extensive mixing, making it suitable for deep reinforcement.

[0037] Fast and efficient: The liquid form can directly penetrate the soil, with a fast reaction speed and significantly shortened curing time.

[0038] The first aspect of the present invention is to provide an expansive soil conditioner, wherein each part of the conditioner comprises the following raw materials: 2.5-10 ml of potassium phosphate solution, 0.02-0.12 g of surfactant, and 2-8 L of water.

[0039] This invention provides an expansive soil conditioner, in which potassium phosphate solution dissolves to produce K + and H2PO4 - / HPO4 2- Ions, K + Na can interact with the clay layers + / Ca 2+ Ion exchange occurs, altering the interlayer structure and reducing the expansion potential; H2PO4 - / HPO4 2- With Al in the soil 3+ The reaction produces insoluble AlPO4, which precipitates fill pores and cement particles, thereby enhancing soil strength and stability. In other words, the core source of swelling in expansive soils lies in the expansive crystalline structure of their clay minerals (such as montmorillonite). These crystalline layers typically adsorb cations with small hydration radii (such as Na+).+ Ca 2+ In some cases, it also includes Al. 3+ These molecules adsorb a large number of water molecules, leading to an increase in interlayer spacing (d-spacing), which macroscopically manifests as soil swelling.

[0040] The active component in the modifier of this invention can provide a large amount of potassium ions (K). + K + It possesses suitable hydration energy and hydration radius. When K... + It enters the interlayer of clay minerals through ion exchange, displacing the original interlayer cations (including aluminum ions (Al2+) adsorbed by the clay minerals). 3+ When K) + Due to its properties, the hydration film formed is relatively thin and can be more tightly embedded in the hexagonal cavities of the silicon-oxygen tetrahedron, thereby significantly reducing the interlayer spacing and suppressing its hydration expansion capacity. Through this cation replacement process, the present invention fundamentally stabilizes the crystal structure of clay minerals and reduces the initial expansion potential energy of the soil.

[0041] Aluminum ions (Al) displaced from the clay interlayer 3+ ), and other forms of aluminum that may be present in the expansive soil system, provide key reactants for this invention.

[0042] Another active component in the modifier of this invention may provide phosphate ions (PO4) in expansive soil environments. 3- The replaced Al 3+ With PO4 3- A series of dissolution-precipitation chemical reactions occur in the soil environment, generating a series of water-insoluble aluminum phosphate compounds with cementing properties. These compounds may include amorphous aluminum phosphate gel, aluminum phosphate (AlPO4•2H2O), and other products in different forms.

[0043] The gelling product further enhances the improvement effect in the following ways:

[0044] Cementing and filling effect: The generated aluminum phosphate gel effectively encapsulates and cements clay particles, forming strong bonds between soil particles and significantly improving the structural strength of the soil.

[0045] Pore ​​blocking effect: These insoluble reaction products fill the pores and fissures in the soil, effectively blocking the channels for water migration, reducing water permeability, and making it difficult for external water to quickly penetrate into the soil and trigger expansion.

[0046] Synergistic enhancement: This gelling product and K-type gelling agent... + The stabilized clay skeleton combined with the structure forms a composite stable structure that is both strong and water-resistant.

[0047] In some embodiments of the present invention, the concentration of the potassium phosphate solution is 8-10%. The potassium phosphate solution is a mixed solution of potassium phosphate and phosphoric acid, wherein the content of potassium phosphate in the potassium phosphate solution is less than that of phosphoric acid, and wherein the potassium phosphate is selected from one or more of KH₂PO₄, K₂HPO₄, and K₃PO₄. The solvent is phosphoric acid, the solute is potassium phosphate, and the concentration of potassium phosphate in the potassium phosphate solution is 8-10%.

[0048] In some embodiments of the present invention, the surfactant is a phosphate surfactant, preferably selected from one or more of hydroxyethylidene diphosphonic acid, hydroxyethylidene diphosphonic acid, and hydroxyethylidene diphosphonic acid.

[0049] A second aspect of the present invention is to provide a method for treating expansive soil, comprising the following steps:

[0050] (1) Multiple boreholes are laid out in the expansive soil layer to be treated;

[0051] (2) Prepare the liquid curing agent;

[0052] (3) The liquid curing agent obtained in step (2) is injected into the expansive soil layer to be treated in sections from the bottom of the hole upwards;

[0053] (4) Curing is carried out after grouting is completed.

[0054] In some embodiments of the present invention, the drilling depth in step (1) is 2-6m, specifically 2-4m, 4-5m, or 5-6m; the borehole is conical in shape; the diameter of the borehole is 30mm-60mm, and the taper is 30-45 degrees. A drilling machine is used for drilling. Then, a grouting pipe is lowered, and the space between the grouting pipe and the borehole wall is filled with sand. The distribution of the boreholes is determined and marked using pre-designed drawings.

[0055] In some embodiments of the present invention, the drilling depth in step (1) is equal to the thickness of the expansive soil layer.

[0056] In some embodiments of the present invention, the liquid curing agent in step (2) is not specifically limited, and any liquid curing agent commonly used by those skilled in the art can be used. Specifically, the liquid curing agent in step (2) is the expansive soil conditioner described in the present invention. The liquid curing agent is stored in a high-pressure storage tank with pressure resistance.

[0057] In some embodiments of the present invention, the distance between adjacent boreholes in step (1) is 1.5-3m. Specifically, it can be 1.5-2.5m or 2.5-3m. The swelling rate of the expansive soil to be treated in step (1) is 5-8%.

[0058] In some embodiments of the present invention, in step (3), a liquid curing agent is injected into the current borehole at a constant rate. The injection process continues until liquid curing agent overflows from an adjacent borehole that has previously undergone injection, serving as an observation point. This overflow indicates that the liquid curing agent has sufficiently filled the pore network of the soil between the current borehole and the adjacent observation hole, forming a continuous permeation path. Based on this, it is determined that the soil in this area has reached engineering saturation, at which point the injection into this borehole is terminated.

[0059] In some embodiments of the present invention, the grouting pressure in step (3) is 0.5-1 MPa; the grouting length of each segment is 0.5-1 m; the grouting time of each segment is ≥5 min; and the grouting flow rate is 10-30 L / min. Specifically, a high-pressure grouting pump with a grouting pressure range of 0.5-1.5 MPa is used. The prepared liquid curing agent is injected into the expansion layer in segments from bottom to top through a multi-hole nozzle. The grouting length of each segment is 0.5-1.0 m, and the grouting time is at least 5 minutes, so that the liquid curing agent can penetrate and diffuse in the soil. After each segment is completed, it is left to stand for 5 minutes to ensure that the curing agent reacts evenly.

[0060] In some embodiments of the present invention, each segment is left to stand after infusion, preferably for ≥5 minutes.

[0061] In some embodiments of the present invention, the curing time in step (4) is 3-10 days.

[0062] In some embodiments of the present invention, the grouting equipment is either a high-pressure pump or a grouting device.

[0063] In some embodiments of the present invention, a system for treating expansive soil is provided, comprising a grouting device 2 for injecting a liquid curing agent and a grouting pipe 5 for injecting the liquid curing agent into the expansive soil layer. One end of the grouting pipe 5 is connected to the grouting device 2 via a high-pressure hose 3, and the other end extends into the expansive soil layer. Multiple discharge holes are provided on the side of the grouting pipe 5 away from the grouting device 2. The end of the grouting pipe 5 away from the grouting device 2 is connected via a pipe to a storage tank 1 for holding the liquid curing agent. Here, the storage tank 1 is a liquid curing agent container. The grouting device 2 is a high-pressure pump, the discharge port of which is connected to the high-pressure hose 3, and the inlet of which is connected to the storage tank 1. The grouting pipe 5 can be configured as one or multiple. When multiple grouting pipes 5 are configured, a liquid distribution pipe is provided between the grouting pipe 5 and the high-pressure hose 3. The liquid distribution pipe is provided with at least one outlet. The liquid curing agent flowing through the high-pressure hose 3 is transmitted to the grouting pipe 5 through the outlet of the liquid distribution pipe for grouting. The outlet of the liquid distribution pipe corresponds one-to-one with the grouting pipe 5. Multiple grouting pipes 5 are evenly spaced and arranged laterally and connected by crossbeams. Multiple crossbeams are provided and distributed along the height direction on the grouting pipes 5 to fix the multiple grouting pipes 5. During grouting, the end of the grouting pipe 5 away from the high-pressure hose 3 is passed through the ground 5, and the grouting operation is carried out from bottom to top.

[0064] A third aspect of the present invention is to provide the application of the expansive soil treatment method as described herein in the treatment of high-plasticity expansive soil, saline expansive soil, and high-moisture-content expansive soil.

[0065] In some embodiments of the present invention, high-plasticity expansive soil typically refers to clay with a liquid limit greater than 50 and a plasticity index greater than 20. This type of soil is common in the western United States, such as Texas, Colorado, New Mexico, and parts of California, due to its high montmorillonite content in arid and semi-arid climates. The expansive soil remediation sites designed in both embodiments of the present invention are located in Texas. According to the US Geological Survey Map, the sites in both embodiments belong to the Eagle Shale (a well-known shale oil and gas formation in Texas), which is also a typical high-expansive soil region.

[0066] The depth of high-pressure grouting is typically determined by the potential vertical rise (PVR). PVR is a crucial parameter in the design of roadbeds or foundations for expansive soils, as it predicts the potential degree of soil heave, helping engineers mitigate or avoid engineering damage through structural design or site treatment methods. The Texas Department of Transportation provides the Tex-24-E Potential Vetical Rise (PVR) Excel Workbook to assist engineers in calculating PVR. By entering the soil's liquid limit, plastic limit, and moisture content (considering seasonal temperature variations, the moisture content is typically taken as the lowest historical summer soil moisture content), the PVR value is obtained.

[0067] The present invention will be further illustrated by the following examples, but these examples do not limit the scope of the invention.

[0068] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, equipment, and materials similar to or equivalent to those described, used, and materials in the embodiments of this invention may be used to implement this invention.

[0069] Example

[0070] Example 1

[0071] This embodiment provides a method for treating expansive soil, such as... Figure 1 As shown, it includes the following steps:

[0072] (1) Multiple boreholes are laid out in the expansive soil layer to be treated; wherein, the expansive soil layer to be treated is high plasticity expansive soil with a free expansion rate of 7.5%, and the expansive soil comes from an expansive soil site remediation project in Carrollton, USA; according to the local soil expansion rate, the borehole spacing is set at 2 meters, the borehole depth is 6 meters, and the borehole diameter is 50 mm; the shape of the borehole is conical.

[0073] (2) Prepare a liquid curing agent, stir it evenly, and then inject it into the high-pressure slurry storage tank 1; the liquid curing agent is an expansive soil conditioner, and the conditioner is based on the number of parts, each part of the conditioner includes the following raw materials: 5 ml of potassium phosphate solution, 0.057 g of surfactant and 3.78 L of water; wherein, the surfactant is hydroxyethylidene diphosphonic acid; the concentration of potassium phosphate solution is 10%, the potassium phosphate solution includes phosphoric acid and potassium phosphate, and the potassium phosphate is KH2PO4; the solvent in the potassium phosphate solution is phosphoric acid, the solute is potassium phosphate, and the concentration of potassium phosphate in the potassium phosphate solution is 10%; the manufacturer of potassium phosphate solution is Prochemical Soil Stabilization;

[0074] (3) The liquid curing agent obtained in step (2) is extracted from the storage tank 1 by the high-pressure pump 2 and injected into the expansive soil layer to be treated in sections from the bottom of the hole upward through the high-pressure hose 3 and the grouting pipe 5 at a pressure of 1 MPa. Each section is 0.5 m high and the injection time is at least 5 min. The grouting flow rate is adjusted according to the soil type, as shown in Table 1. After the injection is completed, let it stand for 5 min before lifting. The liquid curing agent is injected until the expansive soil to be treated reaches saturation.

[0075] Table 1 Grouting Flow Rate

[0076]

[0077] (4) After grouting, cure for 8 days. Scanning electron microscope images of the expansive soil layer before and after improvement are shown below. Figure 4 As shown, the treated soils exhibited significant differences in microstructure; clay particles identifiable in the untreated soil were no longer visible in the treated soil, indicating possible reorganization or cementation between particles. Furthermore, the formation of numerous plate-like reaction products and molten clay particles, as well as the effective bonding between clay particles, are likely important reasons for the significant increase in strength and stiffness.

[0078] Example 2

[0079] This embodiment provides a method for treating expansive soil, such as... Figure 1 As shown, the difference from Example 1 is that the expansive soil layer to be treated is high-plasticity expansive soil with a free expansion rate of 5.3%. The expansive soil comes from an expansive soil site remediation project in Dallas, USA. Based on the local soil expansion rate, the hole spacing is set to 2 meters, the hole depth to 5 meters, and the hole diameter to 50 mm. The shape of the hole is conical with a taper of 40°. Everything else is exactly the same as in Example 1.

[0080] Performance testing

[0081] The free expansion rate was tested according to ASTM D 4546. The test results are shown in Table 2.

[0082] Unconfined compressive strength was tested according to ASTM D7012. The test results are shown in Table 2.

[0083] According to ASTM D698, the optimum moisture content and maximum dry density of the compaction test were tested, and the test results are shown in Table 2.

[0084] Table 2. Test results of expansive soil improvement performance in Examples 1-2

[0085]

[0086] Based on Examples 1-2 and the data in Table 2, it can be seen that by using the liquid curing agent and the injection method of the liquid curing agent of this application, the free expansion rate of the expansive soil treated in this way is reduced, the unconfined compressive strength is significantly improved, and the improvement effect is better.

[0087] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An expansive soil conditioner, characterized in that, The modifier is based on parts, and each part of the modifier includes the following raw materials: 2.5-10 ml of potassium phosphate solution, 0.02-0.12 g of surfactant, and 2-8 L of water.

2. The modifier according to claim 1, characterized in that: The potassium phosphate solution comprises phosphoric acid and potassium phosphate; and / or the concentration of the potassium phosphate solution is 8-10%; and / or the pH of the potassium phosphate solution is 3-3.5; and / or the surfactant is a phosphate surfactant, preferably selected from one or more of hydroxyethylidene diphosphonic acid or hydroxyethylidene diphosphonic acid.

3. A method for treating expansive soil, characterized in that, Includes the following steps: (1) Multiple boreholes are laid out in the expansive soil layer to be treated; (2) Prepare the liquid curing agent; (3) The liquid curing agent obtained in step (2) is injected into the expansive soil layer to be treated in sections from the bottom of the hole upwards; (4) Curing is carried out after grouting is completed.

4. The method for treating expansive soil according to claim 3, characterized in that: In step (1), the drilling depth is 2-6m, and the shape of the drilling hole is conical; the diameter of the drilling hole is 30mm-60mm, and the taper is 30-45 degrees; and / or, the drilling depth in step (1) is the thickness of the expansive soil layer; and / or, the liquid solidifying agent in step (2) is the expansive soil conditioner according to any one of claims 1-2.

5. The method for treating expansive soil according to claim 3, characterized in that: In step (1), the distance between adjacent boreholes is 1.5-3m; and / or, the swelling rate of the expansive soil to be treated in step (1) is 5-8%.

6. The method for treating expansive soil according to claim 3, characterized in that: The grouting equipment in step (3) is selected from either a high-pressure pump or a grouting equipment.

7. The method for treating expansive soil according to claim 3, characterized in that: The injection pressure in step (3) is 0.5-1 MPa; the injection length of each segment is 0.5-1 m; the injection time of each segment is ≥5 min; and the injection slurry flow rate is 10~30 L / min.

8. The method for treating expansive soil according to claim 7, characterized in that: After each infusion, the infusion is allowed to stand for at least 5 minutes.

9. The method for treating expansive soil according to claim 3, characterized in that: The maintenance time in step (4) is 3-10 days.

10. The application of the expansive soil treatment method as described in any one of claims 3-9 in the treatment of high-plasticity expansive soil, saline expansive soil, and high-moisture-content expansive soil.

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