Expansive soil improver and improvement method

Abstract

An expansive soil improver and improvement method, the expansive soil improver comprising a polycarbonate resin-based suspension, a polyurethane adhesive, and a hydrophobic magnetic ionic liquid. The expansive soil improver comprises polypropylene fiber, bagasse ash, and a hydrophobic magnetic ionic liquid. The expansive soil improvement method comprises classifying the swelling and shrinkage grades according to the actual conditions of the expansive soil, and then determining the improvement method. The improvement methods include (a) spraying the expansive soil improver; (b) laying a surface improvement layer; and (c) laying a surface improvement layer in combination with deep spraying of the expansive soil improver. The present invention can permanently and significantly inhibit the swelling and shrinkage of the expansive soil and improve the shear strength; the raw materials used are recycled materials, achieving waste reuse and causing minimal environmental pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering, in particular to an expansive soil improver and an improvement method. Background Art

[0002] Expansive soils are clay particles in soil, primarily composed of hydrophilic minerals. They exhibit significant deformation characteristics, both swelling upon water absorption and shrinking upon loss of water. These characteristics include swelling upon water absorption, shrinking upon loss of water, repeated swelling and shrinkage, decreased bearing capacity upon immersion, and the development of shrinkage cracks due to drying, making them extremely unstable. Therefore, a method to improve expansive soils is needed to reduce their expansiveness.

[0003] Currently, there are two main methods for improving expansive soil: physical improvement and chemical improvement. One of the physical improvement methods is to coat the surface of the expansive soil with a hydrophobic material so that moisture in the atmosphere cannot easily enter the interior of the expansive soil. However, the existing hydrophobic materials are relatively simple and have a short service life in harsh environments. One of the chemical improvement methods is to use chemical reagents to exchange ions with the expansive soil, thereby permanently changing the crystal structure of the expansive soil. However, its disadvantage is that the use of chemical reagents will cause certain pollution to the environment, and its effect time is relatively slow. Another chemical improvement method is to use polymers to improve expansive soil. The polymer improves the connection between soil particles through wrapping and mechanical teeth, thereby reducing the expansibility of the expansive soil and increasing the strength of the expansive soil, but its improvement effect is limited.

[0004] Therefore, the field needs to urgently develop an expansive soil improvement method that flexibly uses expansive soil improvement methods, has good improvement effects, and is environmentally friendly. Summary of the Invention

[0005] The object of the present invention is to provide an expansive soil modifier and an improvement method, which can flexibly use the expansive soil improvement method, have good improvement effect, and are ecologically friendly.

[0006] The technical solution of the present invention is to provide an expansive soil improver and an improvement method, wherein the expansive soil improver comprises:

[0007] (a) polycarbonate resin-based suspension;

[0008] (b) hydrophobic magnetic ionic liquid;

[0009] The structural formula of the hydrophobic magnetic ionic liquid is shown in the following formula (I):

[0010]

[0011] (c) polyurethane adhesives;

[0012] An expansive soil improver is prepared by weight: 100 parts of polycarbonate resin-based suspension, 2-5 parts of polyurethane adhesive, and 20-30 parts of hydrophobic magnetic ionic liquid.

[0013] The structural formula of the hydrophobic magnetic ionic liquid is shown in the following formula (I):

[0014]

[0015] The expansive soil modifier has the functions of physical water repellency, polymer network wrapping, and chemical ion exchange modification of the expansive soil with a hydrophobic magnetic ionic liquid. The polyurethane adhesive is used to enhance the compatibility between the polycarbonate resin-based suspension and the expansive soil, while stabilizing the internal structure of the expansive soil.

[0016] The expansive soil improvement method comprises: (1) firstly determining the free expansion and contraction rate δ of the expansive soil according to the free expansion and contraction rate δ of the expansive soil; ef Classify the swelling and shrinkage of expansive soil, (2) and then select different improvement methods according to the swelling and shrinkage grades;

[0017] The swelling and shrinkage grades of expansive soil are divided into:

[0018] (a) If 40% ≤ δ ef If the expansion and contraction rate is ≤60%, the expansion and contraction grade is Grade III, and the improvement method of spraying expansive soil improver is selected;

[0019] (b) If 60% ≤ δ ef If the expansion and contraction level is ≤75%, the expansion and contraction level is Class II, and the improvement method of laying the surface improvement layer is selected;

[0020] (c) If 75% ≤ δ ef If the expansion and contraction rate is ≤90%, the expansion and contraction grade is Grade I. Then the improvement method of laying a surface improvement layer combined with deep spraying of expansive soil improver is selected.

[0021] The expansive soil improvement method comprises the following steps:

[0022] 1) If the swelling and shrinkage grade of the expansive soil is Grade III, the steps for improving the expansive soil by spraying the expansive soil improver are as follows:

[0023] (a) mixing a polycarbonate resin-based suspension, a hydrophobic magnetic ionic liquid, and a polyurethane adhesive in a desired ratio to obtain an expansive soil modifier;

[0024] (b) evenly spraying the expansive soil improver obtained in step (a) on the soil surface to be improved;

[0025] 2) If the swelling and shrinkage grade of the expansive soil is Class II, the steps for improving the expansive soil by laying the surface improvement layer are as follows:

[0026] (a) Excavating part of the expansive soil to be improved from the surface of the expansive soil structure to be improved;

[0027] (b) Determine the optimum moisture content of expansive soil based on compaction tests;

[0028] (c) uniformly mixing (a) polypropylene fiber; (b) bagasse ash; and (c) hydrophobic magnetic ionic liquid in a desired ratio to obtain an expansive soil conditioner slurry;

[0029] (d) uniformly mixing the expansive soil conditioner slurry prepared in step (c) with the expansive soil to be improved, wherein the mixing ratio of the expansive soil conditioner slurry to the dry expansive soil to be improved is 1 / 8-1 / 7 by weight;

[0030] (e) adding water to the uniformly mixed expansive soil modifier slurry and the expansive soil to be improved obtained in step (d) according to the optimal moisture content obtained in step (b), and stirring to obtain the improved expansive soil.

[0031] (f) laying a 30 cm to 50 cm surface improvement layer of the improved expansive soil obtained in step (e) on the construction surface, and then keeping it under natural conditions for 3-4 days.

[0032] 3) If the swelling and shrinkage grade of the expansive soil is Grade I, the expansive soil improvement steps of laying a surface improvement layer combined with deep spraying of expansive soil improver are as follows:

[0033] (a) Excavating part of the expansive soil to be improved from the surface of the expansive soil structure to be improved;

[0034] (b) Determine the optimum moisture content of expansive soil based on compaction tests;

[0035] (c) mixing a polycarbonate resin-based suspension, a hydrophobic magnetic ionic liquid, and a polyurethane adhesive in a desired ratio to obtain an expansive soil modifier;

[0036] (d) spraying the expansive soil conditioner obtained in step (c) evenly on the surface of the structure from which the surface soil has been removed;

[0037] (e) repeating step (d) 3-5 times to make the total amount of the expansive soil modifier sprayed be 1.2-1.6 kg / m2 expansive soil;

[0038] (f) uniformly mixing the polypropylene fiber, bagasse ash, and hydrophobic magnetic ionic liquid in a desired ratio to obtain an expansive soil conditioner slurry;

[0039] (g) uniformly mixing the expansive soil conditioner slurry prepared in step (f) with the expansive soil to be improved, wherein the mixing ratio of the expansive soil conditioner slurry to the dry expansive soil to be improved is 1 / 8-1 / 7 by weight;

[0040] (h) adding water to the uniformly mixed expansive soil modifier slurry and the expansive soil to be improved obtained in step (g) according to the optimal moisture content obtained in step (b), and stirring to obtain the improved expansive soil.

[0041] (i) laying a 30-50 cm surface improvement layer of the improved expansive soil obtained in step (h) on a construction surface, and then maintaining it under natural conditions for 3-4 days.

[0042] Step 2) The surface improvement layer is formed by paving improved expansive soil, wherein the improved expansive soil comprises: (a) expansive soil improver slurry; (b) expansive soil to be improved,

[0043] The expansive soil improver slurry is prepared according to the following ingredients and their weight parts:

[0044] (a) polypropylene fiber; 0.5-1 part of polypropylene fiber,

[0045] (b) hydrophobic magnetic ionic liquid; 9-14 parts of hydrophobic magnetic ionic liquid,

[0046] (c) Bagasse ash: 85-90.5 parts of bagasse ash.

[0047] The polypropylene fiber is sourced from discarded medical masks. The polypropylene fiber is prepared by disinfecting, melting, cooling, and crushing the discarded masks to produce a fiber-based liquid. This liquid is then passed through a spinning box to form fiber tows, which are then shaped and dried to obtain the polypropylene fiber. This method, which converts discarded masks into recycled polypropylene fiber, not only reuses medical waste but also reduces the expansion rate of expansive soil and improves its shear strength.

[0048] The main component of bagasse ash is SiO2. The improvement mechanism of bagasse ash on expansive soil mainly includes ion exchange, cementation, filling and adsorption on the surface of bagasse ash. Combined with the reinforcement effect of polypropylene fiber and the ion exchange and hydrophobic effect of hydrophobic magnetic ionic liquid, it can permanently reduce the expansion rate of expansive soil and improve the shear strength of expansive soil.

[0049] Bagasse is a waste material in the sugar production chain, and its combustion products contain a high content of SiO2. This invention combines bagasse ash with expansive soil, not only reusing agricultural waste resources, but also permanently reducing the expansion rate of the expansive soil and improving its shear strength.

[0050] The bagasse ash is a combustion product of waste bagasse with a particle size of 60-110 meshes.

[0051] The polypropylene fiber is a regenerated fiber with a diameter of 1 mm and a length of 10-20 mm prepared from discarded medical masks.

[0052] The expansive soil improvement method is applied in slope engineering.

[0053] The preparation method of improved expansive soil comprises the following steps:

[0054] (1) uniformly mixing (a) polypropylene fiber; (b) bagasse ash; and (c) a hydrophobic magnetic ionic liquid in a desired proportion to obtain an expansive soil conditioner slurry;

[0055] (2) uniformly mixing the expansive soil improver slurry prepared in step (1) with the expansive soil to be improved, wherein the mixing ratio of the expansive soil improver slurry to the dry expansive soil to be improved is 1 / 8-1 / 7 by weight;

[0056] (3) adding water to the uniformly mixed expansive soil improver slurry obtained in step (2) and the expansive soil to be improved according to the optimal moisture content of the original expansive soil, and stirring them uniformly to obtain the improved expansive soil.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) Different improvement methods can be selected according to the different swelling and shrinkage levels of expansive soil, which can simultaneously meet the needs of expansive soil improvement and maximize economic benefits;

[0059] (2) The expansive soil improver has the effects of physical water repellency, polymer network wrapping, and chemical ion exchange improvement of the expansive soil with a hydrophobic magnetic ionic liquid. Among them, polyurethane is used as an adhesive to enhance the compatibility between the polycarbonate resin-based suspension and the expansive soil, stabilize the internal structure of the expansive soil, reduce the expansion rate of the expansive soil, and improve the shear strength of the expansive soil;

[0060] (3) In the improved expansive soil, the expansion rate of the expansive soil is permanently reduced and the shear strength of the expansive soil is improved through the filling effect of bagasse ash, the reinforcement effect of polypropylene fiber, and the ion exchange effect between the hydrophobic magnetic ionic liquid and the expansive soil;

[0061] (4) The preparation and improvement methods are simple, and the raw materials used are environmentally friendly, achieving waste recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a cross-sectional view of the expansive soil slope structure after improvement by laying a surface improvement layer combined with deep spraying of an expansive soil improver in an embodiment of the present invention.

[0063] Marked in the figure are: slope expansive soil layer 1, sprayed improver improvement layer 2, and surface improvement layer 3. DETAILED DESCRIPTION

[0064] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0065] The raw materials and components used in the examples were purchased from commercial sources.

[0066] The hydrophobic magnetic ionic liquid was prepared according to Example 1 of Chinese invention patent application 202210259349.1. The preparation method is as follows: 1,1,1,3-tetramethylguanidine and 1-bromo-3-phenylpropane are used as raw materials, and in the presence of tetrabutylammonium bromide and K2CO3, a synthesis reaction is carried out to obtain [TMDPG] + Br - ; said [TMDPG] + Br - A replacement reaction is carried out with KPF6J to obtain a hydrophobic ionic liquid; the hydrophobic ionic liquid is combined with nickel chloride to obtain the hydrophobic magnetic ionic liquid.

[0067] The source of polypropylene fiber is discarded medical masks. The preparation method of polypropylene fiber is: the discarded masks are disinfected, melted, cooled, and crushed to make a fiber base liquid, which is then passed through a spinning box to make fiber bundles, and finally shaped and dried to obtain polypropylene fiber.

[0068] The bagasse ash used may include powder having a particle size of 60-110 meshes, and its main component is silicon dioxide.

[0069] Examples 1-4

[0070] The following embodiments are four embodiments of the expansive soil improvement method of the present invention, comprising the following steps:

[0071] Free expansion rate determination

[0072] According to the Standard for Geotechnical Test Methods (GB / T 50123-2019), the free expansion rate of the original expansive soil sample was measured to be 54.3%. The free expansion rate of the modified expansive soil after complete curing was also determined using a similar method.

[0073] Compaction test

[0074] According to the "Standard for Geotechnical Test Methods" (GB / T 50123-2019), the optimal moisture content of undisturbed expansive soil was measured to be 15.7% through compaction test.

[0075] Shear strength measurement

[0076] According to the "Standard for Geotechnical Test Methods" (GB / T 50123-2019), the shear stress of the original expansive soil was measured under vertical pressures of 30, 50, 70, and 90 kPa. Analysis of the data revealed that the shear strength of the original expansive soil was c (cohesion) = 190.1 and Φ (internal friction angle) = 34.5. Similar tests were also conducted on the modified expansive soil to determine its shear strength.

[0077] If the swelling and shrinkage grade of the expansive soil is grade III, the expansive soil improver should be sprayed. According to the formula shown in Table 1, the expansive soil improver is prepared by fully stirring the raw material components. Then the obtained expansive soil improver is sprayed on the surface of the expansive soil.

[0078] Table 1. Formula of the expansive soil improver of Examples 1-4 expressed in weight fraction

[0079]

[0080] Table 2. Performance indexes of expansive soil improved by the expansive soil improver of Examples 1-4 and the improved expansive soil

[0081]

[0082] From the experimental results in Table 2, it can be seen that the free expansion rate of the expansive soil after being improved by the spraying expansive soil modifier of the present invention is 22.8%-28.2%, which is 48%-58% lower than the free expansion rate of the original expansive soil, meeting the construction requirement of a free expansion rate of no more than 40%, and at the same time significantly improving the shear strength of the expansive soil.

[0083] Examples 5-8

[0084] The following embodiments are four other embodiments of the expansive soil improvement method of the present invention, comprising the following steps:

[0085] If the expansive soil's expansion and contraction grade is Class II, a surface modification layer is used. Prepare an expansive soil modification slurry by thoroughly mixing the raw materials according to the formulation shown in Table 3 below. This slurry is then uniformly mixed with the expansive soil to be modified to produce modified expansive soil. The surface modification layer is then applied.

[0086] Table 3. Formula of the modified expansive soil of Examples 5-8 expressed in weight fraction

[0087] Example Example 5 Example 6 Example 7 Example 8 polypropylene fiber 0.5 1 0.5 1.0 Bagasse ash 85.5 90 90.5 85 Hydrophobic magnetic ionic liquids 14 9 9 14

[0088] Table 4. Performance indexes of expansive soil improved by the modifiers of Examples 5-8 and the improved expansive soil

[0089]

[0090] From the experimental results in Table 4, it can be seen that the free expansion rate of the expansive soil improved by the improvement method of laying the surface improvement layer of the present invention is 28.1%-33.%, which is 39%-58% lower than the free expansion rate of the original expansive soil, meeting the construction requirement of a free expansion rate of no more than 40%, while significantly improving the shear strength of the expansive soil.

[0091] Example 9

[0092] The following embodiment is another embodiment of the expansive soil improvement method of the present invention, comprising the following steps:

[0093] If the swelling and shrinkage grade of the expansive soil is Grade I, the improvement method is to lay a surface improvement layer combined with deep spraying of the expansive soil improver.

[0094] Based on 100 parts by weight of a polycarbonate resin-based suspension, the expansive soil conditioner comprises the following components: 2 parts by weight of a polyurethane adhesive and 30 parts by weight of a hydrophobic magnetic ionic liquid. The expansive soil conditioner is prepared by thoroughly mixing the raw materials and then sprayed onto the surface of the expansive soil structure to be improved, after a portion of the soil has been excavated. The improved expansive soil comprises an expansive soil conditioner slurry and the expansive soil to be improved. The expansive soil conditioner slurry comprises the following components, by weight percentage: (a) 0.5 parts by weight of polypropylene fiber; (b) 90.5 parts by weight of bagasse ash; and (c) 9 parts by weight of a hydrophobic magnetic ionic liquid. The raw materials are thoroughly mixed to prepare the expansive soil conditioner slurry. The expansive soil conditioner slurry and the expansive soil to be improved are then evenly mixed in a ratio of 1 / 8 to 1 / 7 of the dry weight of the expansive soil conditioner slurry to the expansive soil to be improved, resulting in the improved expansive soil. A 40 cm thick surface improvement layer is then laid.

[0095] Table 6. Performance indexes of expansive soil improved by the modifier of Example 9 and the improved expansive soil

[0096]

[0097]

[0098] As can be seen from the experimental results in Table 6, the expansive soil improved by the improvement method of spraying the expansive soil modifier of the present invention in combination with laying the improved expansive soil layer has a free expansion rate of 27.1%, which is 72.9% lower than the free expansion rate of the original expansive soil, meeting the construction requirement of not more than 40% free expansion rate, and significantly improving the shear strength of the expansive soil.

[0099] The above embodiments are described to facilitate understanding and application of the present invention by those skilled in the art. It will be apparent to those skilled in the art that various modifications to these embodiments can be readily made and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and improvements and modifications made by those skilled in the art based on the disclosure without departing from the scope and spirit of the present invention are within the scope of the present invention.

Claims

1. An expansive soil conditioner, characterized in that: The expansive soil improver comprises: (a) polycarbonate resin-based suspension; (b) hydrophobic magnetic ionic liquid; The structural formula of the hydrophobic magnetic ionic liquid is shown in the following formula (I): (c) polyurethane adhesives; The expansive soil improver is prepared by weight: 100 parts of polycarbonate resin-based suspension, 2-5 parts of polyurethane adhesive, and 20-30 parts of hydrophobic magnetic ionic liquid.

2. An expansive soil conditioner, characterized in that: Prepared by weight: 0.5-1 parts of polypropylene fiber, 85-90.5 parts of bagasse ash, 9-14 parts of hydrophobic magnetic ionic liquid, The structural formula of the hydrophobic magnetic ionic liquid is shown in the following formula (I):

3. The improvement method using the expansive soil conditioner according to claim 1, characterized in that: (1) First, according to the free expansion and contraction rate δ of expansive soil ef Divide the swelling and shrinkage grades of expansive soil; (2) Select different improvement methods according to the swelling and shrinkage grades. The swelling and shrinkage grades of expansive soil are divided into: (a) If 40% ≤ δ ef If the expansion and contraction rate is ≤60%, the expansion and contraction grade is Grade III, and the improvement method of spraying expansive soil improver is selected; (b) If 60% ≤ δ ef If the expansion and contraction rate is ≤75%, the expansion and contraction level is Class II, and the improvement method of laying the surface improvement layer is selected; (c) If 75% ≤ δ ef If the expansion and contraction level is ≤90%, the expansion and contraction grade is Grade I, and the improvement method of laying a surface improvement layer combined with deep spraying of expansive soil improver should be selected.

4. The expansive soil improvement method according to claim 3, characterized in that: 1) If the swelling and shrinkage grade of the expansive soil is Grade III, the steps for improving the expansive soil by spraying the expansive soil improver are as follows: (a) mixing a polycarbonate resin-based suspension, a hydrophobic magnetic ionic liquid, and a polyurethane adhesive in a desired ratio to obtain an expansive soil modifier; (b) evenly spraying the expansive soil improver obtained in step (a) on the soil surface to be improved; 2) If the swelling and shrinkage grade of the expansive soil is Class II, the steps for improving the expansive soil by laying the surface improvement layer are as follows: (a) Excavating part of the expansive soil to be improved from the surface of the expansive soil structure to be improved; (b) Determine the optimum moisture content of expansive soil based on compaction tests; (c) uniformly mixing (a) polypropylene fiber; (b) bagasse ash; and (c) hydrophobic magnetic ionic liquid in a desired ratio to obtain an expansive soil conditioner slurry; (d) mixing the expansive soil conditioner slurry prepared in step (c) with the expansive soil to be improved, wherein the mixing ratio of the expansive soil conditioner slurry to the dry expansive soil to be improved is 1 / 8-1 / 7 by weight; (e) adding water to the uniformly mixed expansive soil modifier slurry obtained in step (d) and the expansive soil to be improved according to the optimum moisture content obtained in step (b), and stirring to obtain the improved expansive soil; (f) laying a 30 cm to 50 cm surface improvement layer of the improved expansive soil obtained in step (e) on a construction surface, and then keeping it under natural conditions for 3-4 days; 3) If the swelling and shrinkage grade of the expansive soil is Grade I, the expansive soil improvement steps of laying a surface improvement layer combined with deep spraying of expansive soil improver are as follows: (a) Excavating part of the expansive soil to be improved from the surface of the expansive soil structure to be improved; (b) Determine the optimum moisture content of expansive soil based on compaction tests; (c) mixing a polycarbonate resin-based suspension, a hydrophobic magnetic ionic liquid, and a polyurethane adhesive in a desired ratio to obtain an expansive soil modifier; (d) spraying the expansive soil conditioner obtained in step (c) evenly on the surface of the structure from which the surface soil has been removed; (e) repeating step (d) 3-5 times to make the total amount of the expansive soil modifier sprayed be 1.2-1.6 kg / m2 expansive soil; (f) uniformly mixing the polypropylene fiber, bagasse ash, and hydrophobic magnetic ionic liquid in a desired ratio to obtain an expansive soil conditioner slurry; (g) uniformly mixing the expansive soil conditioner slurry prepared in step (f) with the expansive soil to be improved, wherein the mixing ratio of the expansive soil conditioner slurry to the dry expansive soil to be improved is 1 / 8-1 / 7 by weight; (h) adding water to the uniformly mixed expansive soil modifier slurry obtained in step (g) and the expansive soil to be improved according to the optimal moisture content obtained in step (b), and stirring to obtain the improved expansive soil; (i) laying a 30-50 cm surface improvement layer of the improved expansive soil obtained in step (h) on a construction surface, and then maintaining it under natural conditions for 3-4 days.

5. The expansive soil improvement method according to claim 4, characterized in that: Step 2) The surface improvement layer is paved with improved expansive soil, wherein the improved expansive soil comprises: (a) an expansive soil improver slurry; and (b) the expansive soil to be improved, wherein the expansive soil improver slurry is prepared according to the following components and their weight parts: (a) polypropylene fiber; 0.5-1 part of polypropylene fiber, (b) hydrophobic magnetic ionic liquid; 9-14 parts of hydrophobic magnetic ionic liquid, (c) Bagasse ash: 85-90.5 parts of bagasse ash.

6. The expansive soil improvement method according to claim 4, characterized in that: The bagasse ash is a combustion product of waste bagasse with a particle size of 60-110 meshes.

7. The expansive soil improvement method according to claim 4, characterized in that: The polypropylene fiber is made from discarded medical masks that are disinfected, melted, cooled, and crushed to form a fiber base liquid, which is then passed through a spinning box to form fiber bundles. Finally, the fiber is shaped and dried to obtain the polypropylene fiber. The polypropylene fiber is a regenerated fiber with a diameter of 1 mm and a length of 10-20 mm.

8. Use of the expansive soil improver or the improvement method according to any one of claims 1 to 7 in slope engineering.

Images