Composite solidifying agent for reinforcing silt soil, preparation method and application thereof

Abstract

The application belongs to the technical field of soil solidification, and particularly relates to a composite solidifying agent for reinforcing mucky soil, a preparation method and application; the composite solidifying agent comprises cement, an activator, a hydration reaction accelerator and a soil binder; the hydration reaction accelerator promotes the hydration reaction of the cement solidifying agent; the soil binder clogs and blocks the soil particles in the mucky soft soil, thereby reducing water penetration in the mucky soil; meanwhile, the polyacrylamide, magnesium oxide expanding agent and polycarboxylic acid superplasticizer in the activator can improve the early strength or late strength of the solidified mucky soil, and through compounding, the early strength and late strength of the solidified mucky soil are simultaneously improved, so that the bearing capacity of the mucky soft soil is improved, and the occurrence of subsidence is reduced, thereby solving the technical problems that the soil solidifying agent in the prior art has poor reinforcing effect on mucky soil, and the drilling channel is prone to displacement deviation, deformation of a hole wall and settlement in the horizontal directional drilling construction process.

Description

Technical Field

[0001] This application belongs to the field of soil consolidation technology, and particularly relates to a composite solidifying agent for reinforcing silty soil, its preparation method, and its application. Background Technology

[0002] Traditional construction methods often require excavation from above the construction area and then backfilling, which is time-consuming and labor-intensive. In contrast, horizontal directional drilling involves laying pipelines from below the construction area, reducing the amount of construction work and having less impact on surrounding buildings. However, horizontal directional drilling has certain requirements on the bearing capacity and other properties of the soil.

[0003] For example, silty soil, characterized by a high proportion of fine particles, presents significant challenges for horizontal directional drilling (WDD). Silt typically exhibits low bearing capacity, high moisture content, high plasticity, and a tendency to subside. During the guiding and reaming processes of WDD, the weight of the drill bit and reamer, combined with the weak bearing capacity of silty soil, can cause displacement of the borehole channel, affecting the drilling results. Furthermore, the excavation, cutting, and movement of the soil during drilling can lead to soil shifting and reduction. Silty soil itself has poor support capacity; careless excavation can cause collapse and settlement of underground structures. After borehole formation, the inherent properties of silty soil can lead to deformation and settlement of the borehole wall, further impacting surface stability and bearing capacity. Furthermore, according to Article 5.3.3 of the China Engineering Construction Association standard "Technical Specification for Pipeline Crossing Engineering by Horizontal Directional Drilling" (CECS382:2014), after the completion of pipeline laying through the ground by horizontal directional drilling, the overlying soil layer at the pipeline entry and exit ends is relatively thin, and the upper soil may experience settlement and collapse. Corresponding technical measures should be taken to prevent and deal with this.

[0004] Currently, soil stabilizers include inorganic stabilizers such as cement and fly ash, organic stabilizers such as epoxy resins and polymer materials, and less common bio-enzyme stabilizers. These stabilizers generally have low curing strength and are not effective in reinforcing silty soils. This makes the borehole channel prone to displacement during horizontal directional drilling, causing borehole wall deformation and settlement, which in turn affects the stability and bearing capacity of the ground surface. Furthermore, the overlying soil layer at the pipeline entry and exit points is relatively thin, which may lead to settlement and collapse of the upper soil layer. Summary of the Invention

[0005] In view of this, this application provides a composite solidifying agent for reinforcing silty soil, its preparation method, and its application, to solve the technical problem that existing soil solidifying agents have poor reinforcement effects on silty soil, making it easy for the borehole channel to experience displacement deviation, borehole wall deformation, and settlement during horizontal directional drilling.

[0006] The first aspect of this application provides a composite solidifying agent for reinforcing silty soil, comprising: cement, activator, water, calcium-containing hydration reaction promoter, and soil binder;

[0007] The activator includes at least one of polyacrylamide, magnesium oxide expanding agent, and polycarboxylate superplasticizer.

[0008] Preferably, the calcium-containing hydration reaction promoter is selected from calcium chloride.

[0009] Preferably, the soil adhesive is selected from at least one of polyacrylate emulsion, polyvinyl alcohol, or water glass.

[0010] Preferably, the activator includes polyacrylamide, and the mass ratio of cement to polyacrylamide is 18:0.3 to 0.6.

[0011] Preferably, the activator includes a magnesium oxide expansive agent, and the mass ratio of the cement to the magnesium oxide expansive agent is 18:0.2 to 0.8.

[0012] Preferably, the activator includes a polycarboxylate superplasticizer, and the mass ratio of the cement to the polycarboxylate superplasticizer is 18:0.1 to 0.5.

[0013] Preferably, the activator includes polyacrylamide, magnesium oxide expanding agent, and polycarboxylate superplasticizer, wherein the mass ratio of polyacrylamide, magnesium oxide expanding agent, and polycarboxylate superplasticizer is 9:4:3.

[0014] Preferably, the composite curing agent for reinforcing silty soil, calculated by weight, comprises: 10-15 parts by weight of cement, 0.4-0.8 parts by weight of activator, 0.2-0.6 parts by weight of calcium chloride, 5-7 parts by weight of water, 1-3 parts by weight of polyacrylate emulsion, 0.1-0.3 parts by weight of polyvinyl alcohol, and 3-5 parts by weight of water glass.

[0015] The second aspect of this application provides a composite curing agent for reinforcing silty soil, which can be prepared by the composite curing agent for reinforcing silty soil described in the first aspect. The preparation method includes the steps of dissolving cement, activator, calcium chloride, polyacrylate emulsion, polyvinyl alcohol, and water glass in an aqueous solvent to obtain the composite curing agent for reinforcing silty soil.

[0016] The third aspect of this application provides the application of a composite solidifying agent for reinforcing silty soil in the field of horizontal directional drilling.

[0017] In summary, this application provides a composite solidifying agent for reinforcing silty soil, its preparation method, and its application. The composite solidifying agent comprises cement, an activator, water, a soil binder, and a calcium-containing hydration reaction promoter. Cement, as a traditional soil solidifying agent, forms a hardened gel through hydration, increasing the strength and stability of silty soft soil. The hydration reaction promoter accelerates the hydration reaction, enabling the gel to solidify the silty soft soil more quickly and effectively. Furthermore, the soil binder promotes particle aggregation and adhesion, forming a water-resistant layer between silty soft soil particles, reducing water erosion between them. This improves the bearing capacity of the silty soft soil, making it less prone to subsidence. This solves the technical problem in existing technologies where soil solidifying agents are ineffective in reinforcing silty soil, leading to displacement deviations, borehole wall deformation, and settlement during horizontal directional drilling. Detailed Implementation

[0018] This application provides a composite solidifying agent for reinforcing silty soil, its preparation method, and its application, which solves the technical problem that existing soil solidifying agents have poor reinforcement effects on silty soil, making the borehole channel prone to displacement deviation, borehole wall deformation, and settlement during horizontal directional drilling.

[0019] The technical solutions of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, those skilled in the art will not make any mistakes.

[0020] All other embodiments obtained through creative labor are within the scope of protection of this application.

[0021] Given that horizontal directional drilling in silty soft soil is prone to problems such as borehole displacement and collapse due to the soil's high bearing capacity, high moisture content, strong plasticity, and susceptibility to subsidence, this application provides a composite solidifying agent for reinforcing silty soil. The agent comprises cement, an activator, water, a calcium-containing hydration reaction accelerator, and a soil binder. Cement is the primary solidifying agent; the gel formed by the hydration reaction of cement and water significantly enhances the soil's strength and stability. The activator further strengthens the cement's solidification effect and generates additional cementitious substances with the silt, further enhancing the soil's strength and stability. More importantly, the solidifying agent also incorporates a hydration reaction accelerator, whose calcium ions promote the cement hydration reaction. The process reduces the amount of gel material generated in a shorter time, improves the early strength of cement curing, and, because the curing agent provided in this application contains soil binder, the soil binder can promote the mutual attraction between particles and cause adhesion. After the soil particles in the silty soft soil adhere and block water infiltration, it can reduce the dilution of cement and other curing agents by water infiltration on the one hand, and reduce the subsidence of silty soft soil caused by water infiltration on the other hand, and improve the load-bearing capacity of silty soft soil for heavy construction equipment of horizontal directional drilling. Therefore, this application, through the combination of traditional cement curing agent and new activator, as well as calcium-containing hydration reaction promoter and soil binder, greatly improves the strength of silty soil, thereby overcoming the defect that the current soil curing agent has a poor reinforcement effect on silty soil, which makes the borehole channel prone to displacement deviation during horizontal directional drilling.

[0022] Preferably, the calcium-containing hydration reaction promoter in this application is selected from calcium chloride, and the soil binder is selected from one, two or three of polyacrylate emulsion, polyvinyl alcohol or water glass. The curing effect of adding three soil binders is stronger than that of one or two soil binders.

[0023] Example 1

[0024] Example 1 of this application provides a method for preparing a composite curing agent for reinforcing silty soil. The preparation method includes: preparing a soil adhesive composite component and preparing a composite curing agent.

[0025] The preparation of the soil adhesive composite component includes: placing polyacrylate emulsion, polyvinyl alcohol and water glass into a mixing container, turning on the stirrer and stirring at medium speed for 3 minutes to fully mix these substances, thus obtaining the soil adhesive composite component.

[0026] The preparation of the composite curing agent includes: first, adding calcium chloride powder to the soil adhesive composite components and stirring at a low speed for 2 minutes to completely dissolve it; then, slowly adding cement to the mixture from the previous step, increasing the stirring speed, and continuing to stir for 5 minutes; next, slowly adding water and activator, stirring at a medium speed for 10 minutes until the slurry is uniform, forming a uniform composite curing agent, and then sealing it.

[0027] In this embodiment, the amounts of each component of the composite curing agent are as follows: 3g polyacrylate emulsion, 0.1g polyvinyl alcohol, 10g cement, 5g water, 4g water glass, 0.4g activator, and 0.2g calcium chloride. The activator is composed of 0.25g polyacrylamide, 0.1g magnesium oxide expanding agent, and 0.05g polycarboxylate superplasticizer.

[0028] Example 2

[0029] Example 2 of this application provides a method for preparing a composite curing agent for reinforcing silty soil. The difference between the preparation method and Example 1 is that the proportion of each component in the composite curing agent is as follows: 2g polyacrylate emulsion, 0.2g polyvinyl alcohol, 12g cement, 7.2g water, 3g water glass, 0.6g activator, and 0.4g calcium chloride. The activator is composed of 0.35g polyacrylamide, 0.15g magnesium oxide expanding agent, and 0.1g polycarboxylate superplasticizer.

[0030] Example 3

[0031] Example 3 of this application provides a method for preparing a composite curing agent for reinforcing silty soil. The difference between the preparation method and Example 1 is that the proportion of each component in the composite curing agent is as follows: 1g polyacrylate emulsion, 0.2g polyvinyl alcohol, 15g cement, 9g water, 5g water glass, 0.8g activator, and 0.6g calcium chloride. The activator is composed of 0.45g polyacrylamide, 0.2g magnesium oxide expanding agent, and 0.15g polycarboxylate superplasticizer.

[0032] Example 4

[0033] Example 4 of this application provides a method for preparing a curing agent for reinforcing silty soil. In comparison, the preparation method differs from that of Example 1 in that the ratio of each component of the curing agent is: 18g silicate cement and 9g water.

[0034] Example 5

[0035] Example 5 of this application provides a method for preparing a solidifying agent for reinforcing silty soil. In comparison, the preparation method differs from that of Example 1 in that it uses 18g of silicate cement, 8g of fly ash, 9g of water, and 1g of calcium chloride.

[0036] Example 6

[0037] Example 6 of this application provides a method for preparing a solidifying agent for reinforcing silty soil. In comparison, the preparation method differs from that of Example 1 in that it uses 18g of silicate cement, 9g of water, 10g of polyacrylate emulsion, and 1g of calcium chloride.

[0038] Example 7

[0039] Example 7 of this application provides a method for preparing a solidifying agent for reinforcing silty soil. In comparison, the preparation method differs from that of Example 1 in that it uses 18g of silicate cement, 9g of water, 12g of water glass, and 1g of calcium chloride.

[0040] Example 8

[0041] Example 8 of this application provides a method for preparing a solidifying agent for reinforcing silty soil. In comparison, the preparation method differs from that of Example 1 in that it uses 18g of silicate cement, 9g of water, 2g of polyvinyl alcohol, and 1g of calcium chloride.

[0042] Experimental Example 1

[0043] Experimental Example 1 of this application tests the performance of the curing agent provided in Examples 1-8, and tests the curing agent's effect on improving the compressive strength of silty soil.

[0044] The testing and sampling process included: analyzing the silty silt collected from the Xiaolan River in Xiaolan Town, Zhongshan City, Guangdong Province. The analysis results are shown in Table 1.

[0045] Moisture content % Liquid limit / % Plastic Limit / % <![CDATA[Plasticity index I p > <![CDATA[Liquidity index I L > proportion void ratio 60 48.6 28.3 20.3 1.67 2.66 1.686

[0046] Table 1

[0047] The testing process included: first, drying the collected soil samples at 105℃ and passing them through a 0.5cm sieve; then, preparing the dried soil into a wet soil with a 60% moisture content, and mixing it thoroughly using a mixer; adding the curing agent described in Examples 1-7 to every 100g of wet soil. The mixture was then poured into molds, cured underwater for 1 day, and then demolded. The demolded samples were placed in a constant temperature and humidity curing chamber and cured under conditions of 90-100% humidity and 20±2℃. After curing to the required age, the unconfined compressive strength was measured at 7 days and 28 days.

[0048] The test results and compressive strength are shown in Table 2. Table 2 shows that, compared to the curing agents provided in Examples 4 and 6-8, the curing agents provided in Examples 1-3 of this application have a better curing effect on silty soil, and the samples exhibit higher compressive strength. This indicates that, in addition to the curing effect of cement, the composite curing agents provided in Examples 1-3 of this application, due to the effects of hydration reaction promoters, activators, and soil binders, can reduce the subsidence of silty soft soil caused by water infiltration, improve the bearing capacity of silty soft soil for heavy horizontal directional drilling equipment, and enhance soil compressive strength. This overcomes the shortcomings of current soil curing agents in reinforcing silty soil. When the drill bit and reamer are heavy, the cured silty soil exhibits improved bearing capacity, avoiding displacement deviation of the borehole channel, deformation of the borehole wall, and settlement, thus improving the construction effect of horizontal directional drilling. The curing agent provided in Example 5 has a better curing effect, which is due to the addition of fly ash, a commonly used soil reinforcement component.

[0049] Furthermore, comparing Examples 6-8, it can be seen that a large amount of soil binders such as polyacrylate emulsion, water glass, and polyvinyl alcohol were added separately in Examples 6-8, and the amount added was higher than the total amount of polyacrylate emulsion, water glass, and polyvinyl alcohol after compounding provided in Examples 1-3. However, the solidification effect obtained was lower than that in Examples 1-3. This is because after polyacrylate emulsion, water glass, and polyvinyl alcohol are compounded, they can utilize different reinforcement mechanisms, thereby achieving a better reinforcement effect on silty soil.

[0050]

[0051] Table 2

[0052] In Table 2, the compressive strength is obtained through an unconfined compression test, a special case of triaxial testing where the specimen is placed under conditions without lateral restraint. In this test, the minimum principal stress is 0, and the limit value of the maximum principal stress is the unconfined compressive strength. The stress state of the specimen in the triaxial compression test when it is in limit equilibrium is as follows:

[0053]

[0054] In the unconfined compressive strength test, because σ3 is always kept at 0, that is, when in the limit equilibrium state, σ 3f =0, substituting into the above formula, we get:

[0055]

[0056] Use q u Representing the unconfined compressive strength of cohesive soil, we can obtain:

[0057]

[0058] The curing effect was assessed by measuring the unconfined compressive strength at 7 days and 28 days. The unconfined compressive strength specimens were cubes with dimensions of 70.7 mm (length, width, and height). The experimental silty soil was thoroughly mixed with the curing agent, and then poured into the cubes to prepare the specimens. After preparation, the demolded specimens were placed in a constant temperature and humidity curing chamber and cured under conditions of 90–100% humidity and 20 ± 2℃. After the curing period, the unconfined compressive strength was tested. The specimen was placed in the center of the pressure plate of a pressure testing machine, aligned with the upper and lower pressure plates. The machine was started to ensure close contact between the specimen's end face and the upper and lower pressure plates, and a load was applied at a rate of 0.7 mm / min until failure.

[0059] Experimental Example 2

[0060] Experimental Example 2 of this application tested the performance of the activator in the curing agent provided in Examples 1-3. The performance test involved compounding the cement and the components in the activator and comparing the changes in the cured silt samples. The changes in performance after compounding the cement and the polyacrylamide component, magnesium oxide expansion agent component, and polycarboxylate superplasticizer component in the activator and curing 100g of silt sample are shown in Table 3.

[0061] Compound components 3d 28d Cement (18g) 18g water 0.33 0.86 Cement (18g) 18g water + 0.3g polyacrylamide 0.35 0.73 Cement (18g) 18g water + 0.45g polyacrylamide 0.37 0.67 Cement (18g) 18g water + 0.6g polyacrylamide 0.30 0.65 Cement (18g) 18g water + 0.2g magnesium oxide expanding agent 0.31 0.98 Cement (18g) 18g water + 0.5g magnesium oxide expanding agent 0.27 0.89 Cement (18g) 18g water + 0.8g magnesium oxide expanding agent 0.27 0.89 Cement (18g) 18g water + 0.1g polycarboxylate superplasticizer 0.28 0.93 Cement (18g) 18g water + 0.15g polycarboxylate superplasticizer 0.35 1.05 Cement (18g) 18g water + 0.5g polycarboxylate superplasticizer 0.31 0.97

[0062] Table 3

[0063] As shown in Table 3, the curing effect can be improved by compounding any of the components in cement and activator, including polyacrylamide, magnesium oxide expansion agent, and polycarboxylate superplasticizer. For example, the polyacrylamide component can improve the early curing effect. This is because polyacrylamide undergoes chain expansion after absorbing water. The polyacrylamide molecular chains are adsorbed onto the surface of sludge particles through electrostatic interactions, hydrogen bonds, etc., forming a gel structure that effectively binds the sludge particles together. This expansion process helps to form a cross-linked structure, that is, cross-linking between polyacrylamide molecules, which improves the overall strength of the sludge. However, as a water-soluble polymer, the molecular chains of polyacrylamide are prone to dissolution in the later stage, resulting in a decrease in curing strength.

[0064] The addition of magnesium oxide expanding agent and polycarboxylate superplasticizer significantly improves the later strength. This is because the magnesium oxide expanding agent utilizes the hydration reaction of magnesium oxide to release oxygen when exposed to moisture or heat, causing the soil volume to expand. This expansion helps fill soil pores, compensates for the shrinkage deformation of cement-cured concrete, and improves the crack resistance and density of cement-cured concrete, thereby enhancing the curing effect of cement. At the same time, after the magnesium oxide expanding agent expands and fills the soil pores, it can improve the soil's water resistance, enabling it to maintain stability under water or humid conditions, thus making it suitable for the curing of silty soil with high water content. However, the magnesium oxide expanding agent is prone to damaging cementitious materials in the early stages of expansion, therefore, the curing effect is lower in the early stages of curing.

[0065] Polycarboxylate superplasticizer, as a water-reducing agent, can reduce the viscosity of concrete, improve the fluidity of soft soil curing agent, making it easier for it to penetrate and distribute in soft soil. It can also reduce the amount of water required in soft soil curing agent, reduce the ratio of curing agent to cement, and improve the strength and durability of concrete. However, the addition of polycarboxylate superplasticizer will result in a lower curing effect in the early stage of curing.

[0066] As can be seen from Experimental Example 2 of this application, the curing agent provided in this application, based on the curing of silty soil by components such as cement, hydration reaction accelerator and soil binder, further adds polyacrylamide component, magnesium oxide expansion agent component and polycarboxylate high-efficiency water-reducing agent component for compounding. The performance of the resulting curing agent is significantly higher than that of conventional cement, fly ash and other curing agents. Moreover, the high water content in silty soil is suitable for polyacrylamide to form molecular chains in water to cement the soil and improve the early curing strength, and the magnesium oxide expansion agent absorbs water and expands to improve the later curing strength.

[0067] Furthermore, when the mass ratios of polyacrylamide, magnesium oxide expanding agent, and polycarboxylate superplasticizer in the compounded curing agent are 0.45g, 0.2g, and 0.15g respectively, that is, when the mass ratio is 9:4:3, both good early curing effect and good late curing effect can be achieved.

[0068] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. Use of a composite type solidifying agent for reinforcing argillaceous soil in the field of horizontal directional drilling, characterized in that, The application relates to a composite curing agent for reinforcing silt soil. The excitation agent comprises polyacrylamide, magnesium oxide expanding agent and polycarboxylic acid superplasticizer; the mass ratio of the polyacrylamide, the magnesium oxide expanding agent and the polycarboxylic acid superplasticizer in the excitation agent to cement is 0.3-0.6:0.2-0.8:0.1-0.5:

18. The soil adhesive is selected from polyacrylate emulsion, polyvinyl alcohol and water glass. The composite curing agent for reinforcing silt soil comprises 10-15 parts by mass of cement, 0.4-0.8 parts by mass of excitation agent, 0.2-0.6 parts by mass of calcium-containing hydration reaction accelerator, 5-7 parts by mass of water, 1-3 parts by mass of polyacrylate emulsion, 0.1-0.3 parts by mass of polyvinyl alcohol and 3-5 parts by mass of water glass. The application of the composite curing agent for reinforcing silt soil in the field of horizontal directional drilling comprises that the composite curing agent is used for simultaneously improving the early and late unconfined compressive strengths of silt soil in horizontal directional drilling construction. The excitation agent comprises polyacrylamide, magnesium oxide expanding agent and polycarboxylic acid superplasticizer, and the mass ratio of the polyacrylamide, the magnesium oxide expanding agent and the polycarboxylic acid superplasticizer in the excitation agent is 9:4:

3.

2. Use of a composite type solidifying agent for reinforcing sludge soil according to claim 1 in the field of horizontal directional drilling, characterized in that, The calcium-containing hydration reaction accelerator is selected from calcium chloride.

3. Use of a composite type solidifying agent for reinforcing sludge soil according to claim 1 in the field of horizontal directional drilling, characterized in that, The preparation method of the composite curing agent for reinforcing silt soil comprises the following steps: dissolving cement, excitation agent, calcium chloride, polyacrylate emulsion, polyvinyl alcohol and water glass in a water solvent to obtain the composite curing agent for reinforcing silt soil.

4. Use of a composite solidifying agent for reinforcing soft soil according to any one of claims 1 to 3 in the field of horizontal directional drilling, characterized in that, ​

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