A construction technology for CFG pile composite foundation reinforcement in weak soil

Abstract

This invention relates to the field of foundation treatment technology and discloses a construction process for reinforcing weak foundations using CFG piles. The process includes two separately packaged components, A and B. Component A comprises crushed stone, medium sand, ordinary silicate cement, fly ash, and a water-reducing agent. Component B is an acidic solution with a pH between 3.0 and 4.0, containing citric acid, aluminum sulfate octadecade, and cationic polyacrylamide. During construction, a long spiral drilling rig is used to drill a hole. The main pump is started to inject component A into the central pipeline of the drilling rig, and the pressure drop gradient is calculated in real time. Based on the changes in the pressure drop gradient, the metering pump is dynamically adjusted to quantitatively inject component B into the area above the drill bit outlet to implement dual-liquid grouting, while the drill is simultaneously and uniformly lifted. When a sudden drop in the pressure drop gradient is detected, the injection ratio of component B is sharply increased. This invention utilizes acid-base coagulation reaction and polymer flocculation bridging to achieve adaptive sealing of formation defects, effectively preventing groundwater erosion and grout loss.

Description

Technical Field

[0001] This invention relates to the field of foundation treatment technology, specifically to a construction process for reinforcing soft foundations with CFG pile composite foundations. Background Technology

[0002] CFG piles are a common treatment method in composite foundation reinforcement projects. They are usually constructed by drilling holes with a long spiral drilling rig and pumping the mixture in the center of the pipe.

[0003] Existing construction techniques have revealed several shortcomings in practical applications when dealing with soft foundations such as silty soils and strata rich in groundwater. Due to the poor self-stabilizing capacity of soft soil layers, the soft soil surrounding the borehole wall is easily squeezed into the borehole during drill string extraction, causing the pile diameter to shrink. Furthermore, conventionally proportioned CFG (cumulative silt grain) mixtures have low cohesion and weak resistance to water erosion in their unset state. When groundwater flows through the borehole, the cement and fly ash particles in the mixture are easily diluted and carried away by the water flow, leaving coarse aggregates and causing material segregation. These factors can lead to localized mud inclusions, uneven strength, and even pile breakage, preventing the composite foundation from meeting the designed bearing capacity requirements.

[0004] In engineering construction, the consistency and erosion resistance of the grout are usually increased by adding early-strength agents, quick-setting agents, or increasing the cement content. However, when pumping such quick-setting mixtures over long distances in the central pipeline of a long spiral drill pipe, the material is prone to local hardening before exiting the pipe, leading to serious pipe blockage and interrupting the construction process. On the other hand, the distribution of pores, fissures, and groundwater scour zones within soft strata is concealed and random. Existing pumping processes mostly use a fixed-ratio mixture for uniform and continuous pouring, lacking the ability to sense and adjust to abnormal geological conditions within the borehole. When the drill bit suddenly enters a severely leaking stratum, conventional construction methods cannot promptly change the grout state to block water and seal the blockage. This not only exacerbates the risk of pile breakage but also causes a large amount of leakage and waste of pumped materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a construction process for reinforcing CFG pile composite foundations in soft soil, which solves the problems of easy compression of borehole diameter by soft soil on the borehole wall, slurry segregation and loss caused by groundwater erosion, and the resulting pile breakage and insufficient bearing capacity during the construction of CFG piles in soft soil.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a construction process for reinforcing weak foundations with CFG piles, comprising independently packaged components A and B, and including the following steps: A long spiral drilling rig was used to drill through the soft soil layer to the designed bearing layer elevation to complete the hole formation; Start the main pump to inject component A into the central pipeline of the drilling rig, and calculate the pressure drop gradient of the pipeline in real time; The metering pump is dynamically adjusted according to the change of the pressure drop gradient to inject the B component quantitatively into the area above the drill bit outlet, so that the B component and the A component are combined to implement dual-liquid grouting, and the drill is simultaneously and uniformly lifted to the pile top elevation to complete the pile pouring. By weight, component A is prepared by mixing raw materials comprising the following components: 1000.0 to 1200.0 parts crushed stone, 600.0 to 800.0 parts medium sand, 300.0 to 400.0 parts ordinary Portland cement, 80.0 to 120.0 parts fly ash, 3.04 to 7.80 parts polycarboxylate superplasticizer, 0.114 to 0.416 parts sodium gluconate, and 171.0 to 286.0 parts mixing water; By weight, component B is prepared from a mixture of raw materials comprising: 566.5 to 871.1 parts deionized water, 38.9 to 158.5 parts citric acid, 75.0 to 250.0 parts aluminum sulfate octadechydrate, and 15.0 to 25.0 parts cationic polyacrylamide; wherein the cationic polyacrylamide has a weight-average molecular weight of 8,000,000 to 12,000,000 Da; and the pH value of component B is between 3.0 and 4.0.

[0007] By adopting the above technical solution, and utilizing a dynamic pressure drop feedback mechanism combined with dual-liquid grouting at the pipe ends of components A and B, a foundation reinforcement effect that resists groundwater erosion and adapts to abnormal geological conditions within the borehole is achieved. Specifically, sodium gluconate added to component A acts as a retarder, adsorbing onto the surface of cement particles to hinder early hydration and ensuring the fluidity of component A during long-distance pumping in a single pipe. This synergizes with the pipe-end setting-promoting mechanism of component B in both time and space. The specific reaction mechanism and innovative points are explained in the following steps: Step 1: Acid-base neutralization and coagulation reaction. Component B is an acidic solution with a pH of 3.0 to 4.0 and contains dissolved aluminum ions. Component A contains ordinary silicate cement and is therefore strongly alkaline. An acid-base neutralization reaction occurs when the two components meet in the pipeline above the drill bit outlet. In the alkaline environment, aluminum ions rapidly undergo hydration reactions with calcium ions, sulfate ions, and hydroxide ions released from the cement to form ettringite. This reaction consumes free water in the system within a short time, promoting the formation of an early crystallization framework structure in the mixed slurry. This effectively reduces the initial fluidity of the slurry and increases its consistency, giving it the yield stress to resist lateral compression from the soft soil in the borehole wall at the moment of drill string removal, thus preventing pile diameter reduction.

[0008] Step two: electrostatic charge neutralization and macromolecular bridging flocculation. In the early stages of cement hydration, the particle surfaces carry a negative charge. The cationic polyacrylamide in component B carries a positive charge. When the two components are mixed, polymer segments adsorb onto the negatively charged cement and fly ash particles, resulting in electrostatic neutralization. Simultaneously, the long polymer chains with a weight-average molecular weight of 8,000,000 to 12,000,000 Da act as bridges, connecting the independent cementitious material particles and aggregates into a continuous network. This reaction can trap water within the network structure, increasing the cohesiveness of the mixture and preventing scouring and separation by water flow, as well as dilution by weak sludge on the pore walls.

[0009] Step 3: Controlled release of complex structure. Citric acid in component B acts as a complexing agent, forming a complex with aluminum ions under initial acidic conditions. As the mixture transitions to an alkaline environment, citric acid gradually releases free aluminum ions with the change in pH. This controlled release mechanism controls the instantaneous rate of the coagulation reaction, ensuring sufficient time for fluid to drain from the pipe and preventing rapid hardening and consolidation of the mixture within the pipe, which could lead to blockage.

[0010] Preferably, the raw materials of component B also include hydrochloric acid solution or sodium hydroxide solution for adjusting pH.

[0011] By adopting the above technical solution, the initial hydrogen ion concentration of the B component system is adjusted to maintain the relative solubility equilibrium of aluminum ions and citric acid complex.

[0012] Preferably, the crushed stone is continuously graded crushed stone with a particle size of 5 to 20 mm; the fineness modulus of the medium sand is 2.3 to 3.0.

[0013] By adopting the above technical solutions, a particle skeleton structure is constructed inside the mixture system, thereby improving the compressive physical strength after pile consolidation.

[0014] Preferably, the ordinary Portland cement is P.O42.5 grade ordinary Portland cement; and the fly ash is Class F II fly ash.

[0015] By adopting the above technical solution, silicate minerals and volcanic ash active materials necessary for the hydration reaction are provided, ensuring the long-term mechanical properties of the pile body.

[0016] Preferably, the cationic polyacrylamide is a polymer formed by copolymerization of acrylamide monomer and acryloyloxyethyltrimethylammonium chloride monomer; the molar percentage of acryloyloxyethyltrimethylammonium chloride monomer in the copolymer monomer is 30% to 40%.

[0017] By adopting the above technical solution, the distribution density of cationic groups on the polymer molecular chain segments is set so that its electrostatic attraction ability matches the amount of negative charge on the surface of cement particles, thereby achieving effective surface flocculation and adsorption.

[0018] Preferably, the cationic polyacrylamide is prepared via a process comprising the following steps: Deionized water, the acrylamide monomer, and the acryloyloxyethyltrimethylammonium chloride monomer are mixed and stirred to dissolve, thereby obtaining a mixture with a total monomer mass concentration of 20% to 25%. High-purity nitrogen gas is introduced into the mixture to remove oxygen, and the temperature of the mixture is adjusted to a constant temperature of 40 to 45°C. Then, an initiator system of ammonium persulfate and sodium bisulfite is added. The mixture is sealed and reacted at a constant temperature for 4 to 6 hours to form an elastic block. Then, it is mechanically granulated to obtain particles. The particles are washed with anhydrous ethanol, vacuum dried, crushed and sieved.

[0019] By adopting the above technical solution, using a redox initiation system in conjunction with an oxygen-free isothermal environment, the chain growth rate during the free radical copolymerization process is controlled to obtain long-chain polymer materials with linear structures.

[0020] Preferably, in the step of injecting component A into the central pipeline of the drilling rig, the pumping pressure is maintained at 5.0 to 8.0 MPa, and the volumetric flow rate of component A is 30 to 50 m³ / s. 3 / h; the drilling speed is controlled between 1.2 and 1.8 m / min.

[0021] By adopting the above technical solution, the material filling requirements in the lifting space of the auger bit are matched, the continuous pumping positive pressure state at the bottom of the hole and inside the drill rod is maintained, and the mud and water on the outside of the hole wall are prevented from seeping back into the central pipeline.

[0022] Preferably, a diaphragm pressure transmitter on the pipeline is used to calculate the pressure drop gradient in real time; When the pressure drop gradient is detected to be within the range of -0.05 to +0.05 MPa / s, the B component is injected as a base at 0.3% to 0.8% of the volumetric flow rate of the A component; When the pressure drop gradient is detected to be below -0.1 MPa / s and the duration is not less than 0.5 seconds, the injection amount of component B is increased sharply to 2.0% to 3.5% of the volumetric flow rate of component A within 100 ms.

[0023] By adopting the above technical solution, a feedback control process is established between the internal fluid pressure loss and changes in the formation environment. A stable pressure drop gradient indicates that the formation where the drill bit is located is intact and there is no grout leakage. At this time, basic injection can improve the overall material's anti-scouring ability. A pressure drop gradient of not less than 0.1 MPa / s indicates that the drill bit has encountered a weak hole or groundwater scour zone, causing grout leakage. At this time, the metering pump increases the delivery ratio of component B, generating a coagulation and flocculation reaction in the drill bit area, causing the leaked material to rapidly thicken at the defects in the borehole wall and achieve local sealing, thereby blocking the grout leakage path.

[0024] Preferably, in the drilling step, the long auger drill is driven down at a drilling speed of 1.0 to 1.5 m / min; in the step of injecting component B, the injection point of component B is located 1.0 to 1.5 m above the drill bit outlet.

[0025] By adopting the above technical solution, the position of the junction of the reactants in the pipeline is set, and the movement time of the two-liquid mixture to the end of the drill bit is controlled to ensure that the mixed slurry forms a thickened flocculation state when it is discharged.

[0026] Preferably, component B is prepared in advance through the following steps: Start stirring in the storage tank, add the deionized water, the citric acid and the aluminum sulfate octadeca, and stir until fully dissolved; The pH of the dissolved mixture was adjusted to 3.0 to 4.0 by adding an acid-base adjustment solution dropwise. The cationic polyacrylamide was slowly added under continuous low-shear stirring and aged at room temperature for 2 to 4 hours to form component B.

[0027] By adopting the above technical solution, the pH adjustment and the polymer dissolution process are combined in an orderly manner to unfold the molecular chain structure of cationic polyacrylamide and obtain a liquid additive solution with uniform component distribution.

[0028] This invention provides a construction process for reinforcing weak foundations using CFG piles. It offers the following advantages: 1. This invention combines component A, which contains ordinary silicate cement, with component B, which contains aluminum ions and citric acid, above the drill bit outlet. By utilizing the acid-base neutralization and the reaction that generates ettringite, the consistency of the slurry is increased during the discharge stage. At the same time, the initial setting rate is controlled by the synergistic slow-release mechanism of citric acid on aluminum ions, so that the mixture maintains suitable fluidity in the central pipeline of the drill pipe. This not only prevents the slurry from diffusing and losing in soft soil strata, but also avoids the pipeline blockage problem caused by the consolidation of the two liquids.

[0029] 2. This invention introduces cationic polyacrylamide with a weight-average molecular weight of 8,000,000 to 12,000,000 Da into the B component formulation. Through electrostatic neutralization of positive and negative charges and the bridging and flocculation effect of the long polymer chains, cement particles, aggregates and water are combined into a continuous network structure. This improves the overall cohesion of the mixture, enabling it to resist the scouring and separation by groundwater flow and the dilution by the weak silt on the borehole wall, thus ensuring the material uniformity and consolidation strength of the CFG pile in water-rich strata.

[0030] 3. This invention uses a pressure transmitter to calculate the pressure drop gradient of the pipeline in real time and dynamically adjusts the injection ratio of component B based on the pressure drop data. In normal formations, the basic injection volume is maintained. When the pressure drop gradient is detected to be lower than the set limit and lasts for a certain period of time, indicating grout leakage or hole defects in the indicator hole, the metering pump is controlled to increase the injection volume of component B sharply in a short period of time. This feedback mechanism instantly enhances the thickening and flocculation reaction in the local area of ​​the drill bit, realizes adaptive sealing of formation defects, reduces material leakage and lowers the risk of pile breakage. Attached Figure Description

[0031] Figure 1 This is a graph showing the change in apparent viscosity of components in an embodiment of the present invention; Figure 2 This is a comparison diagram of the apparent viscosity of embodiments and comparative examples of the present invention; Figure 3 This is a graph showing the change of the energy storage modulus of each component of the present invention over time. Figure 4 This is a graph showing the dynamic yield stress of each component of the present invention over time. Figure 5 This is a bar chart comparing the breakthrough pressures of the present invention. Figure 6 This is a bar chart comparing the permeability after sealing according to the present invention; Figure 7 This is a graph showing the change in leakage rate of each component of the present invention with flushing time; Figure 8 This is a bar chart comparing the residual breakthrough pressures of each test component in this invention. Figure 9 A comparison diagram of injection pressure for cracks of different widths in this invention; Figure 10 This is a comparison diagram of the breakthrough pressure of cracks of different widths according to the present invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a cationic polyacrylamide (CPAM-1), including the following steps: Step 1: In a 1L glass reactor equipped with a mechanical stirrer and a nitrogen gas inlet, add 800.0g of deionized water. Then add 92.3g of acrylamide monomer and 107.7g of acryloyloxyethyltrimethylammonium chloride monomer, and stir until fully dissolved. At this point, the total mass concentration of monomers is 20%, and the molar percentage of acryloyloxyethyltrimethylammonium chloride monomer is 30%.

[0034] Step 2: Continuously purge high-purity nitrogen gas into the reactor at a flow rate of 0.5 L / min for 30 minutes to remove oxygen. Maintain a constant water bath temperature of 40°C. Then, add 0.10 g of ammonium persulfate and 0.05 g of sodium bisulfite to the system as initiators.

[0035] Step 3: Stop the nitrogen supply and seal the reactor, maintaining a constant temperature of 40°C for 4 hours. Once a high-viscosity elastic block has formed, stop heating and stirring. Remove the block and mechanically granulate it. Wash the granules twice with anhydrous ethanol, then dry them in a vacuum drying oven at 60°C for 24 hours. The dried material is then pulverized and passed through an 80-mesh sieve to obtain CPAM-1 dry powder. Its weight-average molecular weight is approximately 8,000,000 Da.

[0036] Preparation Example 2: This preparation example provides a cationic polyacrylamide (CPAM-2), including the following steps: Step 1: In a 1L glass reactor equipped with a mechanical stirrer and a nitrogen gas inlet, add 775.0g of deionized water. Then add 91.2g of acrylamide monomer and 133.8g of acryloyloxyethyltrimethylammonium chloride monomer, and stir until fully dissolved. At this point, the total mass concentration of the monomers is 22.5%, and the molar percentage of acryloyloxyethyltrimethylammonium chloride monomer is 35%.

[0037] Step 2: Continuously purge high-purity nitrogen gas into the reactor at a flow rate of 0.5 L / min for 30 minutes to remove oxygen. Maintain a constant water bath temperature of 42°C. Then, add 0.113 g of ammonium persulfate and 0.056 g of sodium bisulfite as initiators.

[0038] Step 3: Stop the nitrogen supply and seal the reactor, maintaining a constant temperature of 42℃ for 5 hours. Once a high-viscosity elastic block has formed, stop heating and stirring. Remove the block and mechanically granulate it. Soak and wash the granules twice in anhydrous ethanol, then dry them in a vacuum drying oven at 60℃ for 24 hours. The dried material is then pulverized and passed through an 80-mesh sieve to obtain CPAM-2 dry powder. Its weight-average molecular weight is approximately 10,000,000 Da.

[0039] Preparation Example 3: This preparation example provides a cationic polyacrylamide (CPAM-3), including the following steps: Step 1: In a 1L glass reactor equipped with a mechanical stirrer and a nitrogen gas inlet, add 750.0g of deionized water. Then add 88.8g of acrylamide monomer and 161.2g of acryloyloxyethyltrimethylammonium chloride monomer, and stir until fully dissolved. At this point, the total mass concentration of monomers is 25%, and the molar percentage of acryloyloxyethyltrimethylammonium chloride monomer is 40%.

[0040] Step 2: Continuously purge high-purity nitrogen gas into the reactor at a flow rate of 0.5 L / min for 30 minutes to remove oxygen. Maintain a constant water bath temperature of 45°C. Then, add 0.125 g of ammonium persulfate and 0.063 g of sodium bisulfite as initiators.

[0041] Step 3: Stop the nitrogen flow and seal the reactor, maintaining a constant temperature of 45°C for 6 hours. Once a high-viscosity elastic block has formed, stop heating and stirring. Remove the block and mechanically granulate it. Wash the granules twice in anhydrous ethanol, then dry them in a vacuum drying oven at 60°C for 24 hours. The dried material is then pulverized and passed through an 80-mesh sieve to obtain CPAM-3 dry powder. Its weight-average molecular weight is approximately 12,000,000 Da.

[0042] Examples 1-3: Example 1: This embodiment provides a construction process for reinforcing soft soil foundations using CFG pile composite foundations, including the following steps: Step 1, Preparation of Component A: According to 1m 3For the mixture, add 1000.0 kg of crushed stone (continuous gradation 5 to 20 mm) and 600.0 kg of medium sand (fineness modulus 2.3 to 3.0) to the forced concrete mixer in sequence, and dry mix for 30 seconds; then add 300.0 kg of ordinary Portland cement (P.O4 2.5 grade) and 80.0 kg of fly ash (F class II grade), and continue to dry mix for 30 seconds; dissolve 3.04 kg of polycarboxylate superplasticizer and 0.114 kg of sodium gluconate in 171.0 kg of mixing water, add to the mixer and wet mix for 120 seconds, then load into the concrete mixer truck for later use.

[0043] Step 2, Preparation of Component B: Prepare 1000 kg of aqueous solution of Component B in a storage tank equipped with a paddle stirrer. Add deionized water, start stirring, add 38.9 kg of citric acid (C6H8O7) and 75.0 kg of aluminum sulfate octahydrate (Al2(SO4)3·18H2O) and stir until fully dissolved; adjust the pH of the system to 3.0 using a 10% hydrochloric acid solution; under continuous low-shear stirring, slowly sprinkle in 15.0 kg of CPAM dry powder prepared in Preparation Example 1, and mature at room temperature for 2 hours to form Component B solution for later use.

[0044] Step 3, Drilling: The long spiral drilling rig is aligned with the pile position and drills down at a drilling speed of 1.0 m / min to penetrate the soft soil and silt layer to the designed bearing layer elevation.

[0045] Step 4, Dual-liquid grouting at the pipe end and pile forming: Start the main concrete pump and pump component A in 30m... 3 A flow rate of / h is injected into the central pipeline of the drilling rig, maintaining a pumping pressure of 5.0MPa. The pressure drop gradient (dP / dt) is calculated in real time using a diaphragm pressure transmitter on the pipeline. The B-component metering pump is started (injection point located 1.0m above the drill bit outlet): when dP / dt is detected to be within the range of -0.05 to +0.05MPa / s, B-component is injected at 0.3% of the A-component volumetric flow rate; when dP / dt is detected to be below -0.1MPa / s for more than 0.5 seconds, the metering pump rapidly increases the B-component injection rate to 2.0% of the A-component volumetric flow rate within 100ms. During the grouting process, the drilling rig is raised at a constant speed of 1.2m / min to the pile top elevation, completing the pile casting.

[0046] Example 2: This embodiment provides a construction process for reinforcing soft soil foundations using CFG pile composite foundations, including the following steps: Step 1, Preparation of Component A: According to 1m 3For the mixture, 1100.0 kg of crushed stone and 700.0 kg of medium sand were added sequentially to the forced concrete mixer and dry-mixed for 45 seconds; then 350.0 kg of ordinary Portland cement and 100.0 kg of fly ash were added and dry-mixed for another 45 seconds; 5.175 kg of polycarboxylate superplasticizer and 0.2475 kg of sodium gluconate were dissolved in 225.0 kg of mixing water, added to the mixer and wet-mixed for 150 seconds, and then loaded into a concrete mixer truck for later use.

[0047] Step 2, Preparation of Component B: Prepare 1000 kg of aqueous solution of Component B in a storage tank equipped with a paddle stirrer. Add deionized water, start stirring, add 86.5 kg of citric acid (C6H8O7) and 150.0 kg of aluminum sulfate octahydrate (Al2(SO4)3·18H2O) and stir until fully dissolved; adjust the pH of the system to 3.5 using a 10% hydrochloric acid solution; under continuous low-shear stirring, slowly sprinkle in 20.0 kg of CPAM dry powder prepared in Preparation Example 2, and mature at room temperature for 3 hours to form Component B solution for later use.

[0048] Step 3, Drilling: The long spiral drilling rig is aligned with the pile position and drills down at a drilling speed of 1.25m / min to penetrate the soft soil and silt layer to the designed bearing layer elevation.

[0049] Step 4, Dual-liquid grouting at the pipe end and pile forming: Start the main concrete pump and pump component A in 40m... 3 A flow rate of / h is injected into the central pipeline of the drilling rig, maintaining a pumping pressure of 6.5MPa. The pressure drop gradient (dP / dt) is calculated in real time using a diaphragm pressure transmitter on the pipeline. The B-component metering pump is started (injection point located 1.2m above the drill bit outlet): when dP / dt is detected to be within the range of -0.05 to +0.05MPa / s, B-component is injected into the foundation at 0.55% of the A-component volumetric flow rate; when dP / dt is detected to be below -0.1MPa / s and remains below for more than 0.5 seconds, the metering pump rapidly increases the B-component injection rate to 2.75% of the A-component volumetric flow rate within 100ms. During the grouting process, the drilling rig is raised at a uniform speed of 1.5m / min to the pile top elevation, completing the pile casting.

[0050] Example 3: This embodiment provides a construction process for reinforcing soft soil foundations using CFG pile composite foundations, including the following steps: Step 1, Preparation of Component A: According to 1m 3For the mixture, 1200.0 kg of crushed stone and 800.0 kg of medium sand were added sequentially to the forced concrete mixer and dry-mixed for 60 seconds; then 400.0 kg of ordinary Portland cement and 120.0 kg of fly ash were added and dry-mixed for another 60 seconds; 7.80 kg of polycarboxylate superplasticizer and 0.416 kg of sodium gluconate were dissolved in 286.0 kg of mixing water, added to the mixer and wet-mixed for 180 seconds, and then loaded into a concrete mixer truck for later use.

[0051] Step 2, Preparation of Component B: Prepare 1000 kg of aqueous solution of Component B in a storage tank equipped with a paddle stirrer. Add deionized water, start stirring, add 158.5 kg of citric acid (C6H8O7) and 250.0 kg of aluminum sulfate octahydrate (Al2(SO4)3·18H2O), and stir until fully dissolved; adjust the pH of the system to 4.0 using a 10% sodium hydroxide solution or hydrochloric acid solution; under continuous low-shear stirring, slowly sprinkle in 25.0 kg of CPAM dry powder prepared in Preparation Example 3, and mature at room temperature for 4 hours to form Component B solution for later use.

[0052] Step 3, Drilling: The long spiral drilling rig is aligned with the pile position and drills down at a drilling speed of 1.5m / min to penetrate the soft soil and silt layer to the designed bearing layer elevation.

[0053] Step 4, Dual-liquid grouting at the pipe end and pile forming: Start the main concrete pump and pump component A in 50m... 3 A flow rate of / h is injected into the central pipeline of the drilling rig, maintaining a pumping pressure of 8.0MPa. The pressure drop gradient (dP / dt) is calculated in real time using a diaphragm pressure transmitter on the pipeline. The B-component metering pump is started (injection point located 1.5m above the drill bit outlet): when dP / dt is detected to be within the range of -0.05 to +0.05MPa / s, B-component is injected at 0.8% of the A-component volumetric flow rate; when dP / dt is detected to be below -0.1MPa / s for more than 0.5 seconds, the metering pump rapidly increases the B-component injection rate to 3.5% of the A-component volumetric flow rate within 100ms. During the grouting process, the drilling rig is raised at a uniform speed of 1.8m / min to the pile top elevation, completing the pile pouring.

[0054] Comparative Examples 1-2: Comparative Example 1: Compared with Example 2, the difference is that citric acid is not added in the preparation of component B, and aluminum sulfate octahydrate and CPAM are directly mixed under acidic conditions, while the rest are the same.

[0055] Comparative Example 2: Compared with Example 2, the difference is that the cationic polyacrylamide (CPAM) in component B is replaced with an equal amount of conventional anionic polyacrylamide (APAM), while the rest are the same.

[0056] Test Examples 1-5: Test Example 1: Static Storage Stability Test of Component B This test example is used to determine the rheological stability of component B under acidic storage conditions.

[0057] Experimental steps: Step 1: Take 500 mL of each of the B component solutions prepared in Examples 1 to 3 and Comparative Example 1, put them into a polyethylene sealed reagent container, remove the air from the top, and tighten the sealing cap.

[0058] Step 2: Place the reagent container in a constant temperature chamber at 25±1℃ and let it stand.

[0059] Step 3: Samples were taken from the container on days 1, 15, 30, and 60 of storage. The apparent viscosity of each solution was measured using an NDJ-8S digital rotational viscometer. Rotor No. 2 was selected, and the rotation speed was set to 30 r / min. Data was recorded after the reading stabilized for 30 seconds. After each test, the sample was resealed and stored in a constant temperature incubator.

[0060] Experimental data: Table 1. Apparent viscosity data of each component solution under different storage periods (unit: mPa·s) in conclusion: Based on the data in Table 1 and the graph showing the change in apparent viscosity of the component solutions over storage time, the rheological parameters of different test components during 60 days of constant temperature and sealed storage are presented, consisting of two graphs. Figure 1 The graph shows the apparent viscosity of Examples 1, 2, and 3 over time, with the vertical axis using a linear scale. This graph reflects that the apparent viscosity of the B component solutions in the three examples remained at an extremely low level throughout the entire 60-day static isothermal storage test period, without any significant increase or continuous thickening trend. The solutions maintained a low-viscosity fluid state, indicating that the components of each example possess long-term rheological stability.

[0061] Figure 2 The graph shows a line graph comparing the apparent viscosity of Examples 1 to 3 with that of Comparative Example 1. Considering the large viscosity range of Comparative Example 1 in the later stages, the vertical axis of the graph uses a logarithmic scale. The graph visually shows the contrast between the stability of the components in the examples and the deterioration process of Comparative Example 1: The viscosity of component B solution in Comparative Example 1 was normal in the early stage of storage, but the apparent viscosity increased exponentially from day 15, reaching 3425.1 mPa·s on day 30, and the fluidity decreased. Finally, it lost its fluidity and gelled on day 60.

[0062] Test results show that the coordination effect of citric acid and the repulsion mechanism of like charges in the system prevent premature cross-linking. In the system with a pH of 3.0 to 4.0, the citric acid added in the examples coordinated with aluminum ions, reducing the concentration of free aluminum ions. The remaining free aluminum ions are positively charged and electrostatically repel the quaternary ammonium cation groups on the cationic polyacrylamide molecular chain. The like charge repulsion keeps the polymer segments in an extended conformation, avoiding intermolecular entanglement and coordination. In Comparative Example 1, no citric acid was added, and the system lacked coordination binding of aluminum ions; the free aluminum ions gradually cross-linked and solidified with the polymer segments over time. Test data confirm that the components of the examples are suitable for long-term storage and low-resistance pumping.

[0063] Test Example 2: Transient Rheological Step Test in a Strongly Alkaline High-Calcium Environment This test example is used to determine the transient rheological changes of component B after it comes into contact with a strongly alkaline, high-calcium liquid phase environment.

[0064] Experimental steps: Step 1: Add calcium hydroxide powder to deionized water and stir until suspended. Allow to stand and filter to obtain the supernatant. Add sodium hydroxide solution to the extracted supernatant to adjust the pH of the system to 13.0 and prepare a simulated cement hydration solution for later use.

[0065] Step 2: Using a rotational rheometer equipped with a parallel plate measuring fixture, set the test plate spacing to 1.0 mm and the temperature control system temperature to 25°C. Set the instrument's running time scanning mode, with a fixed strain amplitude of 1% and a test frequency of 1 Hz.

[0066] Step 3: Add 2.0 mL of simulated cement hydration liquid to a flat plate under the rheometer and start the time-scan program. At the 2nd second, use a pipette to inject 0.5 mL of the tested component B (Examples 1 to 3, and Comparative Example 2) into the hydration liquid. Close the instrument to the set interval and record the storage modulus and dynamic yield stress data at each time point within the test cycle. Repeat the test three times for each sample and take the arithmetic mean.

[0067] Experimental data: Table 2. Data on storage modulus and dynamic yield stress of each component mixture over time. in conclusion: Based on the data in Table 2 and the graph showing the relationship between the rheological parameters of each component mixture and the test time, the transient rheological parameter changes of different test components after contact with a strongly alkaline, high-calcium environment are presented, consisting of two graphs. (Attached is a diagram.) Figure 3 This is a line graph showing the change of energy storage modulus of each component over time. To accommodate data that varies across orders of magnitude, the vertical axis uses a logarithmic scale. (See attached image.) Figure 3The results show that after the injection of the strongly alkaline high-calcium hydration solution in Examples 1 to 3 at the 2nd second, the storage modulus of component B rapidly increases and remains high, and the dynamic yield stress increases by orders of magnitude at the 3rd second, continuing to rise throughout the test period. The increase in rheological parameters indicates a transformation from a liquid to a gel state, signifying a structural change in the system. (Appendix) Figure 4 The graph shows the dynamic yield stress of each component over time, with the vertical axis also using a logarithmic scale. This graph reflects the order-of-magnitude increase in dynamic yield stress during the test period for Examples 1 to 3. In Comparative Example 2, after the B component was injected into the hydration solution, neither the storage modulus nor the dynamic yield stress increased; its storage modulus showed a gradual decrease without any increase in value, while the dynamic yield stress decreased slightly and remained at a low level. Overall, the values ​​decreased due to system dilution and environmental changes, and the solution remained in a fluid state without cross-linking. Both graphs together confirm that the components of the examples possess the characteristic of triggering cross-linking under a strongly alkaline, high-calcium environment.

[0068] The test results confirmed the precipitation displacement and electrostatic crosslinking mechanism of the system under pH abrupt changes and high-calcium environments. In the example, when the components came into contact with a strongly alkaline hydrate, a high concentration of calcium and hydroxide ions was present in the liquid phase. Calcium ions combined with citrate ions in component B to form calcium citrate precipitate with a small solubility product, thus releasing the coordination bond of citrate to aluminum ions. The released aluminum ions were converted into negatively charged aluminate anionic complexes under strongly alkaline conditions. These aluminate anionic complexes generated electrostatic attraction with the positively charged quaternary ammonium groups on the cationic polyacrylamide molecular chains, promoting polymer chain crosslinking and forming a spatial network structure, resulting in an increase in storage modulus and dynamic yield stress. Comparative Example 2 used anionic polyacrylamide, whose molecular chains carried a negative charge in an alkaline environment, generating electrostatic repulsion with aluminate ions and blocking the crosslinking pathway; increased environmental salinity caused conformational contraction of the molecular chains, resulting in a decrease in rheological parameters. The test data confirmed that the example scheme could undergo in-situ crosslinking after contact with a strongly alkaline, high-calcium environment.

[0069] Test Example 3: Simulated Cement Crack Sealing Pressure Test This test example is used to test the in-situ consolidation and sealing performance of the component B solution in a cracked environment of a cement-based material.

[0070] Experimental steps: Step 1: Mix ordinary Portland cement and standard sand at a mass ratio of 1:3, setting the water-cement ratio to 0.5, and pour the mixture into standard cylindrical specimens. After curing for 28 days, split the specimen axially to create through cracks. Insert 1.5mm thick metal shims into the crack gaps and fix them externally using heat-shrink tubing to prepare simulated cracked core samples.

[0071] Step 2: The simulated core with cracks is loaded into the core holder of the core displacement device, and a circumferential pressure of 3.0 MPa is applied to the outside of the core. Under normal temperature conditions, deionized water is injected from the core inlet at a constant flow rate. After the pressure and flow rate stabilize, the initial water permeability of each core is calculated.

[0072] Step 3: Switch the instrument injection line and inject the B component solutions prepared in Examples 1 to 3 and Comparative Example 2 into the core at a flow rate of 1.0 mL per minute. Stop pumping when continuous flow of working fluid is observed at the outlet. Close the inlet and outlet valves of the displacement device and allow the system to stand for 24 hours.

[0073] Step 4: After settling, open the inlet and outlet valves. Inject deionized water into the core sample inlet, increasing the fluid injection pressure at a rate of 0.1 MPa per minute. Record the critical pressure value at which continuous water flow appears at the outlet face and the injection pressure suddenly drops; this value is the breakthrough pressure. Record the stable fluid flow rate after the pressure breakthrough and calculate the permeability after plugging. Repeat the test three times for each group of samples and take the arithmetic mean.

[0074] Experimental data: Table 3. Simulated fracture core sealing pressure test data in conclusion: Based on the data in Table 3 and the comparison chart of simulated fracture core plugging test parameters, the key pressure-bearing and impermeability parameters of different working fluid components in the simulated fracture core plugging experiment are presented, consisting of two charts. Figure 5 The bar chart shows the breakthrough pressure comparison of each test component, with the vertical axis using a linear scale. The data in the chart shows that after the B component solution from Examples 1 to 3 was injected into the fractured core and allowed to stand for 24 hours, the system withstood breakthrough pressures ranging from 2.65 to 4.72 MPa. The breakthrough pressure values ​​of the treated cores are high, indicating their ability to withstand external fluid displacement. This chart reflects that the components of the examples formed a solidified body with mechanical strength within the fracture channel. Figure 6 A bar chart comparing the permeability of each test component after plugging is presented. Because the data in Comparative Example 2 spans several orders of magnitude with the examples, the vertical axis of this chart uses a logarithmic scale. The chart visually shows that the permeability of the core samples from Examples 1 to 3 decreased to below 5 millidarcy after plugging and remained at an extremely low value, with a plugging rate exceeding 99.9%. In Comparative Example 2, after treatment with component B solution, the breakthrough pressure was 0.12 MPa, which is low and did not form effective pressure resistance. The permeability after plugging was 16350.4 millidarcy, maintaining a high level of conductivity. The fracture remained conductive and did not exhibit plugging pressure resistance. The test results of both charts jointly verify that the example scheme possesses practical engineering effectiveness for sealing cement cracks.

[0075] Test results show that the system undergoes an environmentally responsive crosslinking reaction within the cement cracks. In the example, after the solution enters the crack, it comes into contact with the highly alkaline pore fluid seeping from the cement matrix surface. At the liquid-solid boundary, citrate ions within the system combine with calcium ions diffused from the liquid interface to precipitate calcium citrate, releasing free aluminum ions. The locally strong alkaline conditions convert the aluminum ions into negatively charged aluminate anionic complexes, which electrostatically crosslink with the quaternary ammonium salt groups on the cationic polyacrylamide segments. This reaction propagates from the crack wall into the fluid interior, forming a mechanically strong network gel within the crack channel. The crosslinked gel adheres to the crack wall, providing resistance to fluid displacement and pressure resistance. In Comparative Example 2, the anionic polyacrylamide segments exhibit electrostatic repulsion with aluminate ions in an alkaline environment, failing to form a crosslinked network. The liquid system was lost with the water flow during the water injection pressure test, without hindering fluid penetration into the crack. The test data indicate that the example solution meets the impermeability and pressure resistance requirements for cement crack sealing.

[0076] Test Example 4: Dynamic scouring durability test under high temperature and high salinity environment This test example is used to determine the stability and plugging status of cross-linked solids under high temperature, high salt and fluid shear displacement conditions.

[0077] Experimental steps: Step 1: Prepare a cement-simulated core containing through-cracks according to the method in Test Example 3. Inject the B component solutions prepared in Examples 1 to 3 and Comparative Example 2 into the crack channels of different cores. Seal both ends of the cores and place them in a constant temperature aging chamber at 90°C for 48 hours to induce cross-linking and consolidation of the solution at the high temperature environment and the high-calcium cement interface.

[0078] Step 2: Remove the aged core samples and load them into the test chamber of the core dynamic displacement device. Prepare simulated formation water with a sodium chloride concentration of 25000 mg / L and a calcium chloride concentration of 2000 mg / L.

[0079] Step 3: Set the temperature of the displacement device's temperature control system to 90℃ and apply a circumferential pressure of 5.0 MPa to the core. Start the injection pump and continuously inject simulated formation water from the core inlet at a constant displacement pressure of 2.0 MPa to perform a dynamic scour test.

[0080] Step 4: On days 5, 15, and 30 of the flushing operation, measure and record the fluid leakage rate at the core outlet. After the 30-day test cycle, stop fluid injection and determine the residual breakthrough pressure of each core according to the pressure increment procedure used in Test Example 3. The test data are taken as the arithmetic mean of three repeated experiments.

[0081] Experimental data: Table 4. High-Temperature and High-Salt Dynamic Erosion Test Data Group Leakage rate on day 5 (mL / min) Leakage rate on day 15 (mL / min) Leakage rate on day 30 (mL / min) Residual breakout pressure on day 30 (MPa) Example 1 0.014 0.022 0.029 2.18 Example 2 0.009 0.016 0.021 2.86 Example 3 0.006 0.011 0.015 4.15 Comparative Example 2 12.53 27.68 49.32 0.04 in conclusion: Based on the data in Table 4 and the comparison chart of parameter changes in long-term high-temperature and high-salt dynamic scouring test, the plugging durability and structural stability parameters of different working fluid components under simulated long-term high-temperature dynamic scouring conditions of formation water are shown in two charts. Figure 7 The graph shows the variation of leakage rates of each component with flushing time. Because the data spans four orders of magnitude, the vertical axis uses a logarithmic scale. The graph shows that during a 30-day high-temperature, high-salt flushing cycle, after the B component solutions of Examples 1 to 3 were injected into the core and cross-linked, and subjected to 30 days of flushing at 90℃ and simulated formation water, the leakage rate at the outlet remained between 0.006 and 0.029 mL / min, consistently at an extremely low level, indicating that the cross-linked solidified structure was stable and no significant damage or loss occurred. In contrast, the core treated with the B component solution in Comparative Example 2 showed a leakage rate of 12.53 mL / min on day 5, which increased to 49.32 mL / min by day 30, exhibiting a rapid increase across orders of magnitude with prolonged flushing time, reflecting the complete failure of its sealing structure. Figure 8 This is a comparison of the residual breakthrough pressure of each test component after 30 days of flushing. The vertical axis uses a linear scale. The graph visually shows that after the flushing period, Examples 1 to 3 still retained high pressure resistance, maintaining an effective mechanical sealing barrier, with residual breakthrough pressures of 2.18 to 4.15 MPa on day 30; while the residual breakthrough pressure of Comparative Example 2 dropped to almost zero, with a test result of 0.04 MPa. The two graphs together confirm that the electrostatic cross-linked network constructed by the components of the examples can resist high-temperature thermal motion and shear displacement by high-salt fluids, and possesses long-term engineering durability.

[0082] The above data indicate that the electrostatic crosslinking network composed of aluminate and quaternary ammonium groups maintained structural stability under high temperature and high salinity fluid shearing. Examples 1 to 3 showed in-situ crosslinking reactions within cement cracks, forming a three-dimensional network gel that adhered to the crack walls. The electrostatic interaction between the positive charge centers on the polymer molecular chains and the negative charge centers of the aluminate groups resisted the intensified thermal motion caused by high temperature. Simultaneously, no electrostatic shielding failure occurred in the high-salt liquid environment containing sodium and calcium ions, ensuring the bonding strength at the crosslinking nodes. The calcium citrate precipitate generated in situ during the reaction was distributed within the crosslinking network structure, increasing the density of the gel solid and mitigating the physical wear of the matrix caused by long-term fluid shearing. Comparative Example 2 used anionic polyacrylamide; due to the repulsive force of like charges hindering the crosslinking reaction, the polymer maintained a linear chain conformation. Under the continuous physical scouring action of high temperature and high salinity fluid, the uncrosslinked polymer chains desorbed from the core crack walls and were discharged with the fluid, resulting in an increase in the leakage rate over time and a decrease in the breakthrough pressure value. Based on the comprehensive experimental data, it can be seen that the components provided in the examples, after undergoing responsive cross-linking, have a blocking effect that can withstand high temperature and high salt and long-term fluid displacement.

[0083] Test Example 5: Injection and Sealing Pressure Test of Cement Cracks of Different Widths This test example is used to determine the flow injection capability of the working fluid in micro-slits of different widths, and the difference in in-situ consolidation strength of the crosslinking system under different slit width conditions.

[0084] Step 1: Cement-simulated rock cores with different through-crack widths were prepared using a cutting and shim assembly method. The crack widths were set to 0.1 mm, 0.5 mm, and 1.0 mm, respectively. The rock cores were sealed with heat-shrink tubing, loaded into a core holder, and a confining pressure of 3.0 MPa was applied to the outside.

[0085] Step 2: Under normal temperature conditions, the component B solutions from Examples 1 to 3 are introduced into an intermediate container. The injection pump is started, and the solution is injected into the core fracture at a rate of 0.5 mL per minute. A pressure sensor is used to record the steady injection pressure when the fluid fills the fracture.

[0086] Step 3: Stop pumping when liquid continuously flows out of the core outlet and close the inlet and outlet valves of the displacement device. Let the system stand at room temperature for 48 hours to allow the fluid to cross-link and solidify within the cement cracks.

[0087] Step 4: After settling, open the inlet and outlet valves and inject deionized water at a constant rate from the core inlet. Record the peak pressure value when a large amount of water is released before the pressure drop as the breakthrough pressure. Repeat the test three times for each group and take the arithmetic mean.

[0088] Table 5. Pressure test data for injection and sealing of cement cracks of different widths. Group Crack width (mm) Injection pressure (MPa) Breakthrough pressure (MPa) Example 1 0.1 1.12 5.43 Example 2 0.1 1.35 6.12 Example 3 0.1 1.58 7.04 Example 1 0.5 0.41 3.25 Example 2 0.5 0.53 4.18 Example 3 0.5 0.67 5.21 Example 1 1 0.11 1.84 Example 2 1 0.16 2.53 Example 3 1 0.19 3.66 in conclusion: Based on the data in Table 5 and the comparison chart of pressure-bearing tests for injection and sealing of cement cracks of different widths, the distribution law of the initial flow resistance and cross-linked pressure-bearing strength of the working fluid in the embodiment in micro-cracks of different scales is shown, consisting of two figures. Figure 9 This figure compares the injection pressure of each component in cracks of different widths. The grouped bar chart visually presents the pressure distribution when the uncrosslinked solutions of Examples 1 to 3 enter the cracks. The injection pressure and breakthrough pressure of the solutions from Examples 1 to 3 vary in cement cracks with a width of 0.1 mm to 1.0 mm. In a 0.1 mm crack, the injection pressure of the solutions ranges from 1.12 to 1.58 MPa. As the crack width increases from 0.1 mm to 1.0 mm, the injection pressure of each component shows a significant decreasing trend overall, decreasing to 0.11 to 0.19 MPa when the crack width reaches 1.0 mm. This figure reflects the ability of the solutions from Examples 1 to penetrate deep into pores of different microscales in their initial low viscosity state.

[0089] Figure 10 This chart compares the breakthrough pressures of each component in fractures of different widths. The figures show that after 48 hours of cross-linking and consolidation of the working fluid within the cement fractures, the compressive strength of each core sample was significantly improved. Specifically, in 0.1 mm micro-fractures, the breakthrough pressure after cross-linking ranged from 5.43 to 7.04 MPa, with the consolidated system exhibiting the highest breakthrough pressure. As the fracture width increased, the overall breakthrough pressure decreased; when the fracture width increased to 1.0 mm, the breakthrough pressure ranged from 1.84 to 3.66 MPa, but the basic resistance to fluid breakthrough was still maintained at a width of 1.0 mm. The data changes in both charts jointly confirm that the solution flow properties and the degree of cross-linking and consolidation are synergistically influenced by the pore space scale and the liquid-solid interface contact area.

[0090] Test data show that the solution flow properties and the degree of cross-linking consolidation are affected by the pore space scale. During the injection stage, no cross-linking reaction occurred, the molecular chains did not form a network entanglement, and the liquid viscosity was low, allowing it to enter a 0.1 mm wide crack under low pressure. After the solution filled the crack, the degree of in-situ cross-linking was affected by the ratio of the liquid-solid interface contact area to the fluid volume. With a 0.1 mm crack width, the cement-based surface provided a large specific surface area, allowing calcium and hydroxide ions in the pore fluid to diffuse into the internal fluid. Mass exchange caused the system to release free aluminum ions, which were converted into aluminate anions, forming an electrostatic cross-linking network with the quaternary ammonium salt groups of the polyacrylamide segments. The precipitated calcium citrate particles filled the network gel, improving the mechanical strength and compressive strength of the consolidated body. With a 1.0 mm crack width, the fluid center region was far from the cement wall, and calcium ions diffused inward, forming a concentration gradient. The cross-linking network density decreased from the crack wall to the fluid center, resulting in a decrease in the overall compressive strength. The near-wall region retains the electrostatic cross-linking structure and interfacial physical interlocking, enabling the solidified body within the wide crack to maintain its resistance to fluid penetration. Experiments have confirmed that the solution in this embodiment possesses micro-crack injection capability and establishes a sealing structure in cement cracks of varying widths through interfacial response, demonstrating that this solution can meet the sealing needs of cracks at multiple scales.

Claims

1. A construction process for reinforcing soft soil foundations using CFG pile composite foundations, characterized in that, Including separately packaged components A and B, the process includes the following steps: A long spiral drilling rig was used to drill through the soft soil layer to the designed bearing layer elevation to complete the hole formation; The main pump is started to pressurize component A into the central pipeline of the drilling rig, and the pressure drop gradient of the pipeline is calculated in real time. The metering pump is dynamically adjusted according to the change of the pressure drop gradient to inject the B component quantitatively into the area above the drill bit outlet, so that the B component and the A component are combined to implement dual-liquid grouting, and the drill is simultaneously and uniformly lifted to the pile top elevation to complete the pile pouring. By weight, component A is prepared by mixing raw materials comprising the following components: 1000.0 to 1200.0 parts crushed stone, 600.0 to 800.0 parts medium sand, 300.0 to 400.0 parts ordinary Portland cement, 80.0 to 120.0 parts fly ash, 3.04 to 7.80 parts polycarboxylate superplasticizer, 0.114 to 0.416 parts sodium gluconate, and 171.0 to 286.0 parts mixing water; By weight, component B is prepared by mixing raw materials comprising the following components: 566.5 to 871.1 parts of deionized water, 38.9 to 158.5 parts of citric acid, 75.0 to 250.0 parts of aluminum sulfate octadecahydrate, and 15.0 to 25.0 parts of cationic polyacrylamide; The cationic polyacrylamide has a weight-average molecular weight of 8,000,000 to 12,000,000 Da; The pH value of component B is between 3.0 and 4.

0.

2. The construction technology for reinforcing soft soil foundations using CFG piles according to claim 1, characterized in that, The raw materials for component B also include hydrochloric acid solution or sodium hydroxide solution for adjusting pH.

3. The construction technology for reinforcing soft soil foundations using CFG piles according to claim 1, characterized in that, The crushed stone is continuously graded crushed stone with a particle size of 5 to 20 mm; the fineness modulus of the medium sand is 2.3 to 3.

0.

4. The construction technology for reinforcing soft soil foundations using CFG piles according to claim 1, characterized in that, The ordinary silicate cement is P.O42.5 grade ordinary silicate cement; the fly ash is F-class II fly ash.

5. The construction technology for reinforcing soft soil foundations using CFG piles according to claim 1, characterized in that, The cationic polyacrylamide is a polymer formed by copolymerizing acrylamide monomer and acryloyloxyethyltrimethylammonium chloride monomer; the molar percentage of acryloyloxyethyltrimethylammonium chloride monomer in the copolymer monomer is 30% to 40%.

6. The construction technology for reinforcing soft soil foundations using CFG piles according to claim 5, characterized in that, The cationic polyacrylamide is prepared via a process including the following steps: Deionized water, the acrylamide monomer, and the acryloyloxyethyltrimethylammonium chloride monomer are mixed and stirred to dissolve, thereby obtaining a mixed solution with a total monomer mass concentration of 20% to 25%. High-purity nitrogen gas is introduced into the mixture to remove oxygen, and the temperature of the mixture is adjusted to a constant temperature of 40 to 45°C. Then, an initiator system of ammonium persulfate and sodium bisulfite is added. The mixture is sealed and reacted at a constant temperature for 4 to 6 hours to form an elastic block. Then, it is mechanically granulated to obtain particles. The particles are washed with anhydrous ethanol, vacuum dried, and pulverized and sieved.

7. The construction technology for reinforcing soft soil foundations using CFG piles according to claim 1, characterized in that, During the step of injecting component A into the central pipeline of the drilling rig, the pumping pressure is maintained at 5.0 to 8.0 MPa, and the volumetric flow rate of component A is 30 to 50 m³ / s. 3 / h; the drilling speed is controlled between 1.2 and 1.8 m / min.

8. The construction technology for reinforcing soft soil foundations using CFG piles according to claim 1, characterized in that, The pressure drop gradient is calculated in real time using a diaphragm pressure transmitter on the pipeline; When the pressure drop gradient is detected to be within the range of -0.05 to +0.05 MPa / s, the B component is injected as a base at 0.3% to 0.8% of the volumetric flow rate of the A component; When the pressure drop gradient is detected to be below -0.1 MPa / s and the duration is not less than 0.5 seconds, the injection amount of component B is increased sharply to 2.0% to 3.5% of the volumetric flow rate of component A within 100 ms.

9. The construction technology for reinforcing weak foundations with CFG piles according to claim 1, characterized in that, During the drilling step, the long auger drill is driven down at a drilling speed of 1.0 to 1.5 m / min; during the injection step of component B, the injection point of component B is located 1.0 to 1.5 m above the drill bit outlet.

10. The construction technology for reinforcing soft soil foundations using CFG piles according to claim 1, characterized in that, Component B is prepared in advance through the following steps: Start stirring in the storage tank, add the deionized water, the citric acid and the aluminum sulfate octadeca, and stir until fully dissolved; The pH of the dissolved mixture was adjusted to 3.0 to 4.0 by adding an acid-base adjustment solution dropwise. The cationic polyacrylamide was slowly added under continuous low-shear stirring and aged at room temperature for 2 to 4 hours to form component B.

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