Pile foundation muck flocculation and solidification combined reagent and pile foundation muck flocculation and solidification and in-situ recycling construction method

Abstract

The invention provides a pile foundation muck flocculation and solidification combined reagent which comprises a composite flocculant and a ternary curing agent, the composite flocculant comprises polyacrylamide and a bentonite modifier, and the mass ratio of the polyacrylamide to the bentonite modifier is 8: (2-14); the ternary curing agent comprises cement, desulfurized gypsum and metakaolin, the desulfurized gypsum accounts for 8%-12% of the mass of the cement, and the metakaolin accounts for 5%-8% of the mass of the cement. The invention further provides a pile foundation muck flocculation curing and in-situ recycling construction method, the pile foundation muck flocculation curing combined reagent is adopted, and the pile foundation muck flocculation curing and in-situ recycling construction method is suitable for pile foundations with the empty pile depth being 2-4 m and the empty pile diameter being 0.8-2.0 m. According to the pile foundation muck flocculation solidification and in-situ recycling construction method, the pile foundation muck flocculation solidification combined reagent is adopted, pile foundation muck can be subjected to flocculation solidification, then empty pile backfilling is conducted, and therefore the resource utilization rate of the pile foundation muck is increased, outward transportation is avoided, the use amount of purchased sand and gravel materials is reduced, and the construction cost is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of pile foundation construction technology, and particularly to the field of soil and waste reuse technology generated during pile foundation construction. Specifically, it relates to a combination reagent for flocculation and solidification of pile foundation soil and waste, as well as a construction method for flocculation, solidification, and in-situ reuse of pile foundation soil and waste. Background Technology

[0002] The pile foundation waste generated during pile foundation construction is a composite waste of foundation soil and mud, which is unique to the early stages of building construction. Its core characteristics are the mixture of foundation soil and residual wall mud. The foundation soil includes various types of soil such as miscellaneous fill, silty clay, and sandy soil, and is often in a heterogeneous mixed state. The wall mud contains chemical additives such as bentonite and CMC, which results in the pile foundation waste having both a high water content (up to 60%) and high fluidity, as well as the special characteristics of the interaction between soil particles and chemical additives.

[0003] The current conventional disposal method involves stockpiling pile foundation excavated soil on-site for 2-3 days to allow it to air dry naturally before transporting it off-site. This method has three major drawbacks: First, there is a high risk of mud overflow during the rainy season, and the cost of transporting the pile foundation excavated soil off-site is higher than that of ordinary dry soil because it still contains residual wall-protecting mud after air drying. Second, when the pile foundation is constructed in stages, the pile foundation excavated soil accumulates and occupies the area around the borehole, interfering with the construction organization of core processes such as steel cage hoisting and concrete pouring. Finally, the traditional disposal method is not designed to address the composite characteristics of the foundation soil and wall-protecting mud in the pile foundation excavated soil, resulting in low resource utilization and difficulty in meeting the backfilling needs of pile foundation-related parts such as empty piles and trenches.

[0004] Therefore, it is desirable to provide a construction method for flocculation solidification and in-situ reuse of pile foundation spoil, which can flocculate and solidify the pile foundation spoil and then use it for backfilling empty piles, thereby improving the resource utilization rate of pile foundation spoil, avoiding external transportation, reducing the amount of purchased sand and gravel, and greatly reducing construction costs. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, one object of the present invention is to provide a flocculation and solidification combination reagent for pile foundation slag, which can flocculate and solidify pile foundation slag, thereby enabling it to be used for backfilling empty piles, improving the resource utilization rate of pile foundation slag, avoiding external transportation, reducing the amount of purchased sand and gravel, greatly reducing construction costs, and making it suitable for large-scale promotion and application.

[0006] Another objective of this invention is to provide a construction method for flocculation, solidification, and in-situ reuse of pile foundation slag, which can flocculate and solidify pile foundation slag and then use it for backfilling empty piles, thereby improving the resource utilization rate of pile foundation slag, avoiding external transportation, reducing the amount of purchased sand and gravel, greatly reducing construction costs, and making it suitable for large-scale promotion and application.

[0007] To achieve the above objectives, in a first aspect of the present invention, a composite flocculant and solidification agent for pile foundation slag is provided, characterized in that it comprises a composite flocculant and a ternary solidification agent, wherein:

[0008] The composite flocculant includes polyacrylamide and bentonite modifier, with a mass ratio of polyacrylamide to bentonite modifier of 8:2~14.

[0009] The ternary curing agent consists of cement, desulfurized gypsum, and metakaolin. The desulfurized gypsum accounts for 8% to 12% of the mass of cement, and the metakaolin accounts for 5% to 8% of the mass of cement.

[0010] Preferably, the bentonite modifier is sodium-based bentonite with a cationic quaternary ammonium salt surface modified.

[0011] More preferably, the cationic quaternary ammonium salt is octadecyltrimethylammonium chloride.

[0012] Preferably, the cement is ordinary Portland cement.

[0013] In a second aspect of the present invention, a method for flocculation solidification and in-situ reuse of pile foundation slag is provided, applicable to pile foundations with an empty pile depth of 2m to 4m and an empty pile diameter of 0.8m to 2.0m. The method is characterized in that it employs the aforementioned pile foundation slag flocculation solidification combination reagent and includes the following steps:

[0014] (1) Pre-treat and screen the pile foundation slag to control the maximum particle size of coarse particles to not exceed 40 mm, and crush or remove the excess particles.

[0015] (2) Test the sand content of the pile foundation slag and control the sand content of the pile foundation slag to 12%~22%:

[0016] (21) If the sand content of the pile foundation slag is between 12% and 22%, proceed to step (3).

[0017] (22) If the sand content of the pile foundation slag is >22%, fine-grained soil is added, wherein the proportion of particles with a diameter ≥0.075mm in the fine-grained soil is <5%, and the sand content of the fine-grained soil is <5%, so that the sand content of the pile foundation slag is between 12% and 22%, and then step (3) is carried out.

[0018] (23) If the sand content of the pile foundation slag is <12%, clean sand is added, and the mud content of the clean sand is <3%, so that the sand content of the pile foundation slag is between 12% and 22%, and then step (3) is carried out.

[0019] (3) The content of wall slurry in pile foundation slag is detected by burning method: Take an appropriate amount of pile foundation slag sample, first dry it at 105℃ to a constant mass, and weigh it to obtain the dry weight m1; then burn the dried product at 550℃ for 2 hours, and after cooling, weigh it to obtain the mass of the residue m2. The wall slurry content of pile foundation slag = (m1- m2) / m1x100%. If the wall slurry content of pile foundation slag is ≤8%, the dosage of polyacrylamide is 0.4‰ of the dry soil mass of pile foundation slag, the dosage of bentonite modifier is 0.1‰ of the dry soil mass of pile foundation slag, and the dosage of cement is 3%~5% of the dry soil mass of pile foundation slag. If the wall slurry content of pile foundation slag is >8%, then for every 1% increase in the wall slurry content of pile foundation slag, the dosage of bentonite modifier increases by 0.05‰ of the dry soil mass of pile foundation slag.

[0020] (4) Reagent preparation:

[0021] (41) Preparation of composite flocculant solution: Prepare 12 hours in advance by sealing and stirring polyacrylamide, bentonite modifier and water, then filtering to obtain the composite flocculant solution, wherein the total mass concentration of polyacrylamide and bentonite modifier is 0.2%;

[0022] (42) The ternary curing agent is prepared by a step-by-step mixing process: cement and metakaolin are mixed for the first time, and then desulfurized gypsum is added for the second mixing to obtain the ternary curing agent;

[0023] (5) Flocculation and solidification:

[0024] (51) Composite flocculation and one-time mixing: The pile foundation slag and composite flocculation solution are mixed once;

[0025] (52) Gradient curing and secondary stirring: Add ternary curing agent to the stirred product, stir at low speed first, then stir at high speed to obtain the cured product;

[0026] (6) Pretreatment and backfilling of empty pile walls:

[0027] (61) Pretreatment of pile wall: a permeable casing is used. Multiple permeable holes are opened in the casing wall of the permeable casing. The multiple permeable holes are set at intervals. The burial depth of the permeable casing is 1 / 3 of the depth of the empty pile. An air compressor is used to blow the remaining pile wall of the empty pile to remove the loose soil layer. The water accumulated at the bottom of the empty pile is pumped out by a submersible pump.

[0028] (62) Layered backfilling: Backfill in layers according to the depth of the empty pile. After each layer is poured, compaction is carried out. After compaction, the compaction degree and surface flatness are tested. If they are qualified, the next layer can be constructed. If the diameter of the empty pile is ≥1.5m, a vibrator is inserted when pouring each layer to avoid voids in the middle.

[0029] (7) Maintenance:

[0030] After pouring to the top surface of the empty pile, cover it with geotextile and plastic film for temperature and humidity control within 2 hours.

[0031] Preferably, in step (22), the fine-grained soil is silty clay or silt; in step (23), the clean sand is river sand or manufactured sand.

[0032] Preferably, in step (3), drying is carried out in a constant temperature oven and calcination is carried out in a muffle furnace.

[0033] Preferably, in step (41), the closed stirring is carried out in a closed stirring tank, the temperature of the closed stirring is 20℃~25℃, the speed of the closed stirring is 300r / min, the time of the closed stirring is 90 minutes, and the filtration is carried out using a 100-mesh filter screen; in step (42), the speed of the first stirring is 100r / min, and the time of the first stirring is 30 minutes; the speed of the second stirring is 80r / min, and the time of the second stirring is 30 minutes.

[0034] Preferably, in step (51), the mixing is carried out using a forced mixer, the mixing speed is 50 r / min to 80 r / min, and the mixing time is 3 minutes; in step (52), the low speed is 40 r / min and the low speed time is 1 minute; the high speed is 100 r / min and the high speed time is 2 minutes.

[0035] Preferably, in step (61), the permeable casing is a permeable steel casing, the diameter of the permeable holes is 10mm, the spacing between the permeable holes is 15cm, and several permeable holes are arranged in a quincunx pattern; in step (62), the thickness of each layer is 35cm~45cm, and the number of compaction passes is 3; or,

[0036] In step (7), when the ambient temperature is below 12°C, an electric heating blanket is placed over the outside of the plastic film for heating, and when the ambient temperature is above 28°C, the spray system is turned on for spraying; the curing time is no less than 5 days.

[0037] The main beneficial effects of this invention are:

[0038] 1. The pile foundation slag flocculation and solidification combination reagent of the present invention includes a composite flocculant and a ternary solidifying agent, wherein: the composite flocculant includes polyacrylamide and bentonite modifier, and the mass ratio of polyacrylamide and bentonite modifier is 8:2~14; the ternary solidifying agent includes cement, desulfurized gypsum and metakaolin, wherein the desulfurized gypsum accounts for 8%~12% of the mass of cement and the metakaolin accounts for 5%~8% of the mass of cement. It can flocculate and solidify pile foundation slag, thereby it can be used for backfilling empty piles, improve the resource utilization rate of pile foundation slag, avoid external transportation, reduce the amount of purchased sand and gravel, greatly reduce construction costs, and is suitable for large-scale promotion and application.

[0039] 2. The construction method for flocculation solidification and in-situ reuse of pile foundation slag in this invention is applicable to pile foundations with an empty pile depth of 2m~4m and an empty pile diameter of 0.8m~2.0m. It adopts the above-mentioned pile foundation slag flocculation solidification combination reagent and includes the following steps: (1) pre-treating and screening the pile foundation slag to control the maximum particle size of coarse particles to not exceed 40 mm; (2) detecting the sand content of the pile foundation slag and controlling it to be 12%~22%; (3) using the burning method to detect the wall slurry content of the pile foundation slag, and determining the amount of polyacrylamide and swelling agent based on the wall slurry content of the pile foundation slag. The dosage of soil modifier and cement; (4) reagent preparation; (41) preparation of composite flocculation solution; (42) preparation of ternary curing agent using stepwise mixing process; (5) flocculation and curing; (51) composite flocculation and one-time stirring; (52) gradient curing and two-time stirring; (6) pretreatment of empty pile wall and backfilling; (7) curing. Therefore, it can flocculate and solidify the pile foundation slag and then use it for empty pile backfilling, thereby improving the resource utilization rate of pile foundation slag, avoiding external transportation, reducing the amount of purchased sand and gravel, greatly reducing construction costs, and is suitable for large-scale promotion and application.

[0040] These and other objects, features and advantages of the present invention will be fully apparent from the following detailed description and can be achieved by the means, devices and combinations thereof specifically pointed out in the summary of the invention. Detailed Implementation

[0041] To improve the resource utilization rate of pile foundation spoil, meet the backfilling needs of empty piles, avoid external transportation, reduce the amount of purchased sand and gravel, and significantly reduce construction costs, the inventors have specifically designed a composite agent for the foundation soil-wall slurry of pile foundation spoil. This agent can flocculate and solidify pile foundation spoil, making it suitable for backfilling empty piles. Furthermore, the inventors have developed a construction method for flocculating, solidifying, and reusing pile foundation spoil in situ, thereby improving the resource utilization rate of pile foundation spoil, avoiding external transportation, reducing the amount of purchased sand and gravel, and significantly reducing construction costs.

[0042] This invention first provides a composite flocculant and solidification agent for pile foundation slag, comprising a composite flocculant and a ternary solidification agent, wherein:

[0043] The composite flocculant includes polyacrylamide and bentonite modifier, with a mass ratio of polyacrylamide (PAM) to bentonite modifier of 8:2~14.

[0044] The ternary curing agent consists of cement, desulfurized gypsum, and metakaolin. The desulfurized gypsum accounts for 8% to 12% of the mass of cement, and the metakaolin accounts for 5% to 8% of the mass of cement.

[0045] The bentonite modifier can be any suitable bentonite modifier. Preferably, the bentonite modifier is a sodium-based bentonite with a cationic quaternary ammonium salt surface modified, whose interlayer spacing shows an increasing trend as analyzed by X-ray diffraction (XRD), specific surface area (determined by BET method) in the range of 30-45 m² / g, and cation exchange capacity (CEC) greater than 90 mmol / 100g. Its main mechanism of action is to efficiently adsorb and passivate negatively charged carboxymethyl cellulose (CMC) in the wall-protecting mud through its increased specific surface area and enhanced cation exchange capacity, thereby eliminating the inhibitory effect of CMC on soil particle dispersion and flocculation.

[0046] The cationic quaternary ammonium salt can be any suitable cationic quaternary ammonium salt, more preferably, the cationic quaternary ammonium salt is octadecyltrimethylammonium chloride.

[0047] The cement can be any suitable cement, preferably ordinary Portland cement (OPC).

[0048] This invention also provides a construction method for flocculation solidification and in-situ reuse of pile foundation slag, applicable to pile foundations with an empty pile depth of 2m~4m and an empty pile diameter of 0.8m~2.0m. The construction method for flocculation solidification and in-situ reuse of pile foundation slag uses the above-mentioned pile foundation slag flocculation solidification combination reagent and includes the following steps:

[0049] (1) Pre-treat and screen the pile foundation slag to control the maximum particle size of coarse particles to not exceed 40 mm, and crush or remove the excess particles.

[0050] (2) Test the sand content of the pile foundation slag and control the sand content of the pile foundation slag to 12%~22%:

[0051] (21) If the sand content of the pile foundation slag is between 12% and 22%, proceed to step (3).

[0052] (22) If the sand content of the pile foundation slag is >22%, fine-grained soil is added, wherein the proportion of particles with a diameter ≥0.075mm in the fine-grained soil is <5%, and the sand content of the fine-grained soil is <5%, so that the sand content of the pile foundation slag is between 12% and 22%, and then step (3) is carried out.

[0053] (23) If the sand content of the pile foundation slag is <12%, clean sand is added, and the mud content of the clean sand is <3%, so that the sand content of the pile foundation slag is between 12% and 22%, and then step (3) is carried out.

[0054] (3) The content of wall slurry in pile foundation slag is detected by burning method: Take an appropriate amount of pile foundation slag sample, first dry it at 105℃ to a constant mass, and weigh it to obtain the dry weight m1; then burn the dried product at 550℃ for 2 hours, and after cooling, weigh it to obtain the mass of the residue m2. The wall slurry content of pile foundation slag = (m1- m2) / m1x100%. If the wall slurry content of pile foundation slag is ≤8%, the dosage of polyacrylamide is 0.4‰ of the dry soil mass of pile foundation slag, the dosage of bentonite modifier is 0.1‰ of the dry soil mass of pile foundation slag, and the dosage of cement is 3%~5% of the dry soil mass of pile foundation slag. If the wall slurry content of pile foundation slag is >8%, then for every 1% increase in the wall slurry content of pile foundation slag, the dosage of bentonite modifier increases by 0.05‰ of the dry soil mass of pile foundation slag.

[0055] In specific construction, after determining the above proportion, in order to verify whether the above proportion meets the construction requirements, the following steps (4) and (5) can be used to prepare samples. The particle size distribution and moisture content of the flocculated mixture are tested by indoor test to ensure that the proportion of particles with a particle size ≥1mm in the flocculated mixture is ≥80%, the moisture content is below 40%, and there is no obvious floating slurry on the surface. At the same time, the unconfined compressive strength test is carried out on the cured product after curing to ensure that the compressive strength reaches ≥0.3 MPa after 24 hours, which meets the requirements of anti-disturbance in the early stage of backfilling. In addition, the slump test is carried out on the cured product after curing. The slump value is required to be controlled at 130 mm ± 10 mm, the expansion is controlled at 350 mm ± 10 mm, and the slump loss rate should be less than 10% per hour to meet the pouring requirements of different empty pile diameters.

[0056] (4) Reagent preparation:

[0057] (41) Preparation of composite flocculant solution: Prepare 12 hours in advance by sealing and stirring polyacrylamide, bentonite modifier and water, then filtering to obtain the composite flocculant solution, wherein the total mass concentration of polyacrylamide and bentonite modifier is 0.2%;

[0058] (42) The ternary curing agent is prepared by a step-by-step mixing process: cement and metakaolin are mixed for the first time, and then desulfurized gypsum is added for the second mixing to obtain the ternary curing agent;

[0059] (5) Flocculation and solidification:

[0060] (51) Composite flocculation and one-time mixing: The pile foundation slag and composite flocculation solution are mixed once;

[0061] During the mixing process, polyacrylamide (PAM), through its long polymer chains, acts as a bridging and sweeping agent, efficiently agglomerating dispersed soil particles and bentonite modifier particles adsorbed with CMC. The bentonite modifier continuously passivates residual CMC through ion exchange and surface adsorption. The mixed product exhibits good flocculation and preliminary dehydration. This composite flocculation system can increase the particle size of fine particles in the slag agglomerates from the traditional 0.1 mm to 0.5 mm range of single PAM flocculation to 1 mm to 2 mm, significantly promoting the precipitation of free water. The pH value of the precipitated water is stable between 6.5 and 7.5, meeting the neutral water quality standard, and can be directly used for on-site dust suppression or equipment cleaning, avoiding secondary pollution.

[0062] (52) Gradient curing and secondary stirring: Add ternary curing agent to the stirring product, stir at low speed first to ensure that the ternary curing agent uniformly wets the surface of the aggregates of the stirring product, and then stir at high speed to make the ternary curing agent and the aggregates of the stirring product fully and uniformly mixed, start the curing reaction, and obtain the cured product. The cured product can be sealed and stored, and the sealed storage time should not exceed 12 hours.

[0063] This gradient solidification and strengthening mechanism relies on the hydration products of ordinary Portland cement (OPC), primarily calcium silicate hydrate gel (CSH), to provide the basic bond strength. Simultaneously, desulfurized gypsum undergoes a pozzolanic reaction and a sulfate reaction with metakaolin in an alkaline environment, generating composite crystals such as ettringite (chemical formula 3CaO·Al₂O₃·3CaSO₄·32H₂O) and calcium aluminosilicate hydrate (CASH). These composite crystals grow interwoven within the solidified body, significantly reducing the porosity of the solidified soil through a compaction effect and forming a dense microstructure. More importantly, the composite crystals effectively encapsulate and physically consolidate residual wall-protecting slurry additives (such as incompletely passivated CMC and bentonite), preventing their interference with the cement hydration process, thereby ensuring rapid early-stage strength development and long-term strength stability of the solidified body. Immediately after mixing, a slump test is conducted using a standard slump cone (200 mm in diameter, 300 mm in height). The slump value should be controlled within 130 mm ± 10 mm, the spread within 350 mm ± 10 mm, and the slump loss rate should be less than 10% per hour. Precise control of these flowability indicators ensures that the solidified soil can adapt to empty piles of different diameters, achieving self-leveling and uniform filling, and avoiding voids and segregation.

[0064] (6) Pretreatment and backfilling of empty pile walls:

[0065] (61) Pretreatment of pile wall: A permeable casing is used. Multiple permeable holes are opened in the casing wall. The multiple permeable holes are set at intervals. The burial depth of the permeable casing is 1 / 3 of the depth of the empty pile (i.e., it is located at the upper 1 / 3 position of the empty pile). An air compressor is used to blow and sweep the remaining pile wall of the empty pile to remove the loose soil layer. The water accumulated at the bottom of the empty pile is pumped out by a submersible pump.

[0066] (62) Layered backfilling: Backfill in layers according to the depth of the empty pile. After each layer is poured, compaction is carried out. After compaction, the compaction degree and surface flatness are tested. If they are qualified, the next layer can be constructed. If the diameter of the empty pile is ≥1.5m, a vibrator is inserted when pouring each layer to avoid voids in the middle.

[0067] (7) Maintenance:

[0068] After pouring to the top surface of the empty pile, cover it with geotextile and plastic film for temperature and humidity control within 2 hours.

[0069] In step (22), the fine-grained soil can be any suitable fine-grained soil, preferably, in step (32), the fine-grained soil is silty clay or mud.

[0070] In step (23), the clean sand can be any suitable clean sand, preferably, in step (33), the clean sand is river sand or manufactured sand.

[0071] In step (3), drying and calcination can be carried out using any suitable equipment. Preferably, in step (2), drying is carried out using a constant temperature oven and calcination is carried out using a muffle furnace.

[0072] In step (41), the closed stirring can be carried out using any suitable equipment. The temperature, speed and time of the closed stirring can be determined as needed. The filtration can be carried out using any suitable filter screen. Preferably, in step (41), the closed stirring is carried out using a closed stirring tank. The temperature of the closed stirring is 20℃~25℃ to avoid insufficient dissolution of PAM due to low temperature. The speed of the closed stirring is 300r / min. The time of the closed stirring is 90 minutes. The filtration is carried out using a 100-mesh filter screen to remove undissolved particles.

[0073] In step (42), the speed and time of the first stirring and the speed and time of the second stirring can be determined as needed. Preferably, in step (42), the speed of the first stirring is 100 r / min and the time of the first stirring is 30 minutes; the speed of the second stirring is 80 r / min and the time of the second stirring is 30 minutes.

[0074] In step (51), the mixing can be carried out using any suitable equipment. The speed and time of the mixing can be determined as needed. Preferably, in step (51), the mixing is carried out using a forced mixer. The speed of the mixing is 50 r / min to 80 r / min, and the time of the mixing is 3 minutes.

[0075] In step (52), the speed and time of the low speed and the speed and time of the high speed can be determined as needed. Preferably, in step (52), the speed of the low speed is 40 r / min and the time of the low speed is 1 minute; the speed of the high speed is 100 r / min and the time of the high speed is 2 minutes.

[0076] In step (61), the permeable casing can be made of any suitable material. The diameter of the permeable holes and the spacing between the permeable holes can be determined as needed. The permeable holes can be arranged in any suitable shape. Preferably, in step (61), the permeable casing is a permeable steel casing, the diameter of the permeable holes is 10mm, the spacing between the permeable holes is 15cm, and the permeable holes are arranged in a plum blossom pattern.

[0077] In step (62), the thickness of each layer and the number of rolling passes can be determined as needed. Preferably, in step (62), the thickness of each layer is 35cm to 45cm, which is more suitable for the particle size of agglomerates than the 30cm of the prior art, and the number of rolling passes is 3.

[0078] In step (7), temperature and humidity control can be carried out in any suitable manner, and the curing time can be determined as needed. Preferably, in step (7), when the ambient temperature is below 12°C, an electric heating blanket is covered on the outside of the plastic film for heating, and when the ambient temperature is above 28°C, the spray system is turned on for spraying; the curing time is not less than 5 days.

[0079] To provide a clearer understanding of the technical content of this invention, the following embodiments are provided for detailed description. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Unless otherwise stated, the instruments, pharmaceuticals, reagents, etc., used in the following embodiments can all be obtained through conventional commercial means. In each embodiment, the following are involved:

[0080] For sand content testing, refer to the sieve method in the "Standard for Geotechnical Testing Methods" (GB / T50123-2019): Take 1000g of sandy soil sample, sieve it through a 0.075mm sieve, weigh the mass of the sieve residue (sand particles with a diameter ≥0.075mm), and calculate the actual sand content according to the formula: sand content = (mass of sand particles / total mass of sample) × 100%. The testing frequency is once per 100m³ of pile foundation soil to ensure the accuracy of sand content data for each batch of pile foundation soil.

[0081] The particle size distribution of agglomerates was determined using a laser particle size analyzer, in accordance with ISO 13320-1:2009 "Particle size analysis - Laser diffraction method".

[0082] Moisture content was tested using the drying method, in accordance with GB / T50123-2019.

[0083] Unconfined compressive strength test shall be conducted in accordance with GB / T50123-2019.

[0084] The slump test was conducted in accordance with GB / T 50080-2016 Standard for Test Methods of Performance of Ordinary Concrete.

[0085] Example 1

[0086] The depth of the empty piles is 4.05m and the diameter of the empty piles is 1.0m.

[0087] Composite flocculants include polyacrylamide and bentonite modifier (BP-183 organic bentonite rheology modifier from Guangzhou Yifeng Chemical Technology Co., Ltd.).

[0088] The ternary curing agent consists of cement, desulfurized gypsum, and metakaolin. The desulfurized gypsum accounts for 12% of the mass of the cement, and the metakaolin accounts for 5% of the mass of the cement. The cement is ordinary Portland cement.

[0089] The construction method for flocculation solidification and in-situ reuse of pile foundation slag includes the following steps:

[0090] (1) The pile foundation slag (Longgang District, Shenzhen, Guangdong Province) was pretreated and screened to control the maximum particle size of coarse particles to not exceed 40 mm (in order to match the diameter of the duct pipe for empty pile casting, the maximum particle size of coarse particles should not exceed 4 cm), and the excess part was crushed.

[0091] (2) Test the sand content of the pile foundation slag. The sand content of the pile foundation slag should be controlled between 12% and 22%. The sand content of the pile foundation slag was tested to be 15%.

[0092] (3) The content of wall slurry in pile foundation slag was detected by burning method: Take an appropriate amount of pile foundation slag sample, first dry it to a constant mass in a constant temperature oven at 105℃, and weigh it to obtain the dry weight m1; then burn the dried product in a muffle furnace at 550℃ for 2 hours, and weigh it after cooling to obtain the mass of the residue m2. The wall slurry content of pile foundation slag = (m1- m2) / m1x100%. The detection frequency was set to once every 100 cubic meters of pile foundation slag. The wall slurry content of pile foundation slag was found to be 8%. The dosage of polyacrylamide was 0.4‰ of the dry soil mass of pile foundation slag, the dosage of bentonite modifier was 0.1‰ of the dry soil mass of pile foundation slag, and the dosage of cement was 3% of the dry soil mass of pile foundation slag.

[0093] Sample preparation was carried out using the following steps (4) and (5). The particle size distribution and moisture content of the agglomerates after flocculation were tested in the laboratory. The agglomerates of the agglomerates after flocculation had a particle size ≥1mm accounting for 80%, the moisture content was 37%, and there was no obvious floating slurry on the surface. At the same time, the unconfined compressive strength test and slump test were carried out on the cured product after curing. The compressive strength reached 1 MPa after 24 hours, the slump value was 140 mm, the spread was 350 mm, and the slump loss rate was less than 6% per hour.

[0094] (4) Reagent preparation:

[0095] (41) Preparation of composite flocculant solution: Prepare 12 hours in advance by mixing polyacrylamide, bentonite modifier and water in a closed mixing tank (temperature 20℃, speed 300r / min, time 90 minutes) and then filtering with a 100-mesh filter to obtain composite flocculant solution, wherein the total mass concentration of polyacrylamide and bentonite modifier is 0.2%;

[0096] (42) The ternary curing agent is prepared by a step-by-step mixing process: cement and metakaolin are mixed for the first time at a speed of 100 r / min for 30 minutes, and then desulfurized gypsum is added for the second time at a speed of 80 r / min for 30 minutes to obtain the ternary curing agent.

[0097] (5) Flocculation and solidification:

[0098] (51) Composite flocculation one-time mixing: The pile foundation slag and composite flocculation solution are mixed once using a JS750 forced mixer at a speed of 50r / min for 3 minutes;

[0099] (52) Gradient curing and secondary stirring: Add ternary curing agent to the stirring product, stir at low speed for 1 minute at 40 r / min, then stir at high speed for 2 minutes at 100 r / min to obtain the cured product;

[0100] (6) Pretreatment and backfilling of empty pile walls:

[0101] (61) Pretreatment of pile wall: A permeable steel casing is used. Multiple permeable holes are opened on the wall of the permeable steel casing. The permeable holes are spaced apart from each other. The diameter of the permeable holes is 10mm and the spacing between the permeable holes is 15cm. Several permeable holes are arranged in a plum blossom pattern. The burial depth of the permeable casing is 1 / 3 of the depth of the empty pile. An air compressor is used to blow and sweep the remaining pile wall of the empty pile to remove the loose soil layer. The water accumulated at the bottom of the empty pile is pumped out by a submersible pump.

[0102] (62) Layered backfilling: Backfilling is carried out in 9 layers according to the depth of the empty pile. The thickness of each layer is 45cm. After each layer is poured, it is compacted 3 times. After compaction, the compaction degree and surface flatness are tested. The next layer is carried out after passing the test.

[0103] (7) Maintenance:

[0104] After pouring to the top surface of the empty pile, cover it with geotextile and plastic film for temperature and humidity control within 2 hours. The geotextile is tightly attached to the solidified soil, and the plastic film is covered on the outside. Temperature and humidity sensors are installed, one for every 200m², to monitor the curing environment in real time. When the ambient temperature is below 12℃, cover the outside of the plastic film with an electric heating blanket. When the ambient temperature is above 28℃, turn on the sprinkler system. The curing time is 7 days.

[0105] Example 2

[0106] The depth of the empty piles in the pile foundation is 2m and the diameter of the empty piles is 0.8m.

[0107] The composite flocculant includes polyacrylamide and bentonite modifier (same as in Example 1).

[0108] The ternary curing agent consists of cement, desulfurized gypsum, and metakaolin. The desulfurized gypsum accounts for 8% of the mass of the cement, the metakaolin accounts for 8% of the mass of the cement, and the cement is ordinary Portland cement.

[0109] The construction method for flocculation solidification and in-situ reuse of pile foundation slag includes the following steps:

[0110] (1) The pile foundation slag (Lujia Town, Jianyang City, Chengdu, Sichuan Province) was pretreated and screened to control the maximum particle size of coarse particles to not exceed 40 mm (in order to match the diameter of the duct pipe for empty pile casting, the maximum particle size of coarse particles should not exceed 4 cm), and the excess part was removed.

[0111] (2) Test the sand content of the pile foundation slag. Control the sand content of the pile foundation slag to 12%~22%. If the sand content of the pile foundation slag is 10%, then clean sand, which is river sand, is added. The mud content of the clean sand is <3%, so that the sand content of the pile foundation slag is 12%.

[0112] (3) The content of wall slurry in pile foundation slag was detected by burning method: Take an appropriate amount of pile foundation slag sample, first dry it to a constant mass in a constant temperature oven at 105℃, and weigh it to obtain the dry weight m1; then burn the dried product in a muffle furnace at 550℃ for 2 hours, and after cooling, weigh it to obtain the mass of the residue m2. The wall slurry content of pile foundation slag = (m1- m2) / m1x100%. The detection frequency was set to once every 100 cubic meters of pile foundation slag. The wall slurry content of pile foundation slag was measured to be 20%. The dosage of polyacrylamide was 0.4‰ of the dry soil mass of pile foundation slag, the dosage of bentonite modifier was 0.7‰ of the dry soil mass of pile foundation slag, and the dosage of cement was 4% of the dry soil mass of pile foundation slag.

[0113] Sample preparation was carried out using the following steps (4) and (5). The particle size distribution and moisture content of the agglomerates after flocculation were tested in the laboratory to ensure that the proportion of particles with a particle size ≥1mm in the agglomerates of the agglomerates after flocculation was 83%, the moisture content was 40%, and there was no obvious slurry on the surface. At the same time, the unconfined compressive strength test and slump test were carried out on the cured product after curing. The compressive strength reached 0.6 MPa after 24 hours, the slump value was 120 mm, the spread was 340 mm, and the slump loss rate was less than 8% per hour.

[0114] (4) Reagent preparation:

[0115] (41) Preparation of composite flocculant solution: Prepare 12 hours in advance by mixing polyacrylamide, bentonite modifier and water in a closed mixing tank with temperature control function, or by inserting a thermometer. Mix in a closed tank (temperature 25℃, speed 300r / min, time 90 minutes) and then filter with a 100-mesh filter to obtain composite flocculant solution, wherein the total mass concentration of polyacrylamide and bentonite modifier is 0.2%;

[0116] (42) The ternary curing agent is prepared by a step-by-step mixing process: cement and metakaolin are mixed for the first time at a speed of 100 r / min for 30 minutes, and then desulfurized gypsum is added for the second time at a speed of 80 r / min for 30 minutes to obtain the ternary curing agent.

[0117] (5) Flocculation and solidification:

[0118] (51) Composite flocculation one-time mixing: The pile foundation slag and composite flocculation solution are mixed once using a JS500 forced mixer at a speed of 70r / min for 3 minutes;

[0119] (52) Gradient curing and secondary stirring: Add ternary curing agent to the stirring product, stir at low speed for 1 minute at 40 r / min, then stir at high speed for 2 minutes at 100 r / min to obtain the cured product;

[0120] (6) Pretreatment and backfilling of empty pile walls:

[0121] (61) Pretreatment of pile wall: A permeable steel casing is used. Multiple permeable holes are opened on the wall of the permeable steel casing. The permeable holes are spaced apart from each other. The diameter of the permeable holes is 10mm and the spacing between the permeable holes is 15cm. Several permeable holes are arranged in a plum blossom pattern. The burial depth of the permeable casing is 1 / 3 of the depth of the empty pile. An air compressor is used to blow and sweep the remaining pile wall of the empty pile to remove the loose soil layer. The water accumulated at the bottom of the empty pile is pumped out by a submersible pump.

[0122] (62) Layered backfilling: Backfill in 5 layers according to the depth of empty piles, with each layer being 40cm thick. After each layer is poured, it is compacted 3 times. After compaction, the compaction degree and surface flatness are tested. Only after passing the test can the next layer be constructed.

[0123] (7) Maintenance:

[0124] After pouring to the top surface of the empty pile, cover it with geotextile and plastic film for temperature and humidity control within 2 hours. The geotextile is tightly attached to the solidified soil, and the plastic film is covered on the outside. Temperature and humidity sensors are installed, one for every 200m², to monitor the curing environment in real time. When the ambient temperature is below 12℃, cover the outside of the plastic film with an electric heating blanket. When the ambient temperature is above 28℃, turn on the sprinkler system. The curing time is 5 days.

[0125] Example 3

[0126] The depth of the empty piles is 2.8m and the diameter of the empty piles is 2.0m.

[0127] The composite flocculant includes polyacrylamide and bentonite modifier (same as in Example 1).

[0128] The ternary curing agent consists of cement, desulfurized gypsum, and metakaolin. The desulfurized gypsum accounts for 10% of the mass of the cement, and the metakaolin accounts for 6% of the mass of the cement. The cement is ordinary Portland cement.

[0129] The construction method for flocculation solidification and in-situ reuse of pile foundation slag includes the following steps:

[0130] (1) The pile foundation slag (Dabanqiao Town, Guandu District, eastern Kunming City) was pretreated and screened to control the maximum particle size of coarse particles to not exceed 40 mm (to match the diameter of the duct pipe for empty pile casting, the maximum particle size of coarse particles should not exceed 4 cm), and the excess part was crushed.

[0131] (2) Test the sand content of the pile foundation slag. Control the sand content of the pile foundation slag between 12% and 22%. If the sand content of the pile foundation slag is 25%, then fine-grained soil is added. The fine-grained soil is silty clay, in which the proportion of particles with a particle size ≥ 0.075 mm is < 5%, and the sand content of the fine-grained soil is < 5%, so that the sand content of the pile foundation slag is 22%.

[0132] (3) The content of wall slurry in pile foundation slag was detected by burning method: Take an appropriate amount of pile foundation slag sample, first dry it to a constant mass in a constant temperature oven at 105℃, and weigh it to obtain the dry weight m1; then burn the dried product in a muffle furnace at 550℃ for 2 hours, and weigh it after cooling to obtain the mass of the residue m2. The wall slurry content of pile foundation slag = (m1- m2) / m1x100%. The detection frequency was set to once every 100 cubic meters of pile foundation slag. The wall slurry content of pile foundation slag was 4%. The dosage of polyacrylamide was 0.4‰ of the dry soil mass of pile foundation slag, the dosage of bentonite modifier was 0.1‰ of the dry soil mass of pile foundation slag, and the dosage of cement was 5% of the dry soil mass of pile foundation slag.

[0133] Sample preparation was carried out using the following steps (4) and (5). The particle size distribution and moisture content of the agglomerates after flocculation were tested in the laboratory to ensure that the agglomerates of the agglomerates after flocculation had a particle size ≥1mm accounted for 85%, the moisture content was 35%, and there was no obvious floating slurry on the surface. At the same time, the unconfined compressive strength test and slump test were carried out on the solidified product after solidification. The compressive strength reached 0.3 MPa after 24 hours, the slump value was 130 mm, the spread was 360 mm, and the slump loss rate was less than 10% per hour.

[0134] (4) Reagent preparation:

[0135] (41) Preparation of composite flocculant solution: Prepare 12 hours in advance by mixing polyacrylamide, bentonite modifier and water in a closed mixing tank (temperature 22℃, speed 300r / min, time 90 minutes) and then filtering with a 100-mesh filter to obtain composite flocculant solution, wherein the total mass concentration of polyacrylamide and bentonite modifier is 0.2%;

[0136] (42) The ternary curing agent is prepared by a step-by-step mixing process: cement and metakaolin are mixed for the first time at a speed of 100 r / min for 30 minutes, and then desulfurized gypsum is added for the second time at a speed of 80 r / min for 30 minutes to obtain the ternary curing agent.

[0137] (5) Flocculation and solidification:

[0138] (51) Composite flocculation one-time mixing: The pile foundation slag and composite flocculation solution are mixed once using a JS1000 type forced mixer at a speed of 80r / min for 3 minutes;

[0139] (52) Gradient curing and secondary stirring: Add ternary curing agent to the stirring product, stir at low speed for 1 minute at 40 r / min, then stir at high speed for 2 minutes at 100 r / min to obtain the cured product;

[0140] (6) Pretreatment and backfilling of empty pile walls:

[0141] (61) Pretreatment of pile wall: A permeable steel casing is used. Multiple permeable holes are opened on the wall of the permeable steel casing. The permeable holes are spaced apart from each other. The diameter of the permeable holes is 10mm and the spacing between the permeable holes is 15cm. Several permeable holes are arranged in a plum blossom pattern. The burial depth of the permeable casing is 1 / 3 of the depth of the empty pile. An air compressor is used to blow and sweep the remaining pile wall of the empty pile to remove the loose soil layer. The water accumulated at the bottom of the empty pile is pumped out by a submersible pump.

[0142] (62) Layered backfilling: Backfill in 8 layers according to the depth of the empty pile, with each layer being 35cm thick. After each layer is poured, it is compacted 3 times. After compaction, the compaction degree and surface flatness are tested. If it is qualified, the next layer is constructed. Because the diameter of the empty pile is ≥1.5m, a vibrator is inserted when pouring each layer to avoid voids in the middle.

[0143] (7) Maintenance:

[0144] After pouring to the top surface of the empty pile, cover it with geotextile and plastic film for temperature and humidity control within 2 hours. The geotextile is tightly attached to the solidified soil, and the plastic film is placed on the outside. Temperature and humidity sensors are installed, one for every 200m², to monitor the curing environment in real time. When the ambient temperature is below 12℃, cover the outside of the plastic film with an electric heating blanket. When the ambient temperature is above 28℃, turn on the sprinkler system. The curing time is 6 days.

[0145] Therefore, the construction method for flocculation solidification and in-situ reuse of pile foundation slag in this invention adopts:

[0146] 1. Composite flocculation technology: Abandoning single PAM flocculation, a PAM-bentonite modifier composite flocculation system is adopted. The bentonite modifier eliminates the inhibitory effect of CMC additives in the wall protection mud on particle agglomeration by adsorbing them; PAM plays a sweeping and netting role. The two substances work together to increase the particle size of fine particle agglomerates from the traditional 0.1-0.5mm to 1-2mm. The free water precipitation rate can also be improved, and the pH value of the precipitated water can be stabilized at around 7, which can be directly used for on-site dust suppression and avoid secondary pollution.

[0147] 2. Gradient curing enhancement mechanism: An innovative ternary curing system of cement-desulfurized gypsum-metakaolin is used. Ordinary Portland cement OPC is used as cement, which hydrates to generate CSH gel to achieve basic bonding. Desulfurized gypsum reacts with metakaolin in an alkaline environment to generate ettringite-hydrated calcium aluminosilicate composite crystals. These composite crystals not only reduce porosity through compaction effect, but also encapsulate residual wall-protecting mud additives, preventing them from affecting the improvement of the cured body strength. The compressive strength stabilizes at about 1 MPa after 7 days, and the strength standard deviation is low, which can solve the problem of large strength fluctuations in traditional curing.

[0148] 3. In-situ adaptability design: To address the differences in the diameter of empty piles, the mixing and backfilling process is integrated, allowing the three processes of flocculation mixing, solidification mixing, and layered backfilling to be completed within 5m of the borehole opening without the need for transportation. At the same time, permeable casings are used for support according to the depth of the empty piles. The burial depth of the permeable casing is 1 / 3 of the borehole depth, and the casing wall has permeable holes to prevent water accumulation in the empty pile from affecting solidification. Permeable casings of different heights are suitable for different pile foundation scenarios.

[0149] The present invention can achieve the following:

[0150] 1. To meet the composite needs of foundation soil-wall slurry-empty piles, three major adaptations are achieved: adapting to the site and process requirements of phased pile foundation construction, adapting to the uniform backfilling requirements of empty piles with different diameters and depths, and adapting to the characteristics of wall slurry, eliminating the interference of CMC and other additives on solidification, and improving resource utilization rate.

[0151] 2. The amount of composite flocculant used is reduced compared to the traditional single PAM, and the amount of cement in the ternary solidification system is reduced compared to the traditional technology. In-situ treatment avoids the transportation of slag and soil, and the solidified body can be directly used for backfilling empty piles, reducing the amount of purchased sand and gravel and greatly reducing costs.

[0152] 3. The water released from the composite flocculation can be recycled, the pH value of the solidified body is stable, avoiding alkaline pollution caused by traditional solidifying agents; and it reduces the occupation of spoil heaps, which meets the green construction evaluation standards for pile foundation engineering.

[0153] In summary, the pile foundation slag flocculation solidification and in-situ reuse construction method of the present invention uses a pile foundation slag flocculation solidification combination reagent, which can flocculate and solidify the pile foundation slag, and then use it for backfilling empty piles, thereby improving the resource utilization rate of pile foundation slag, avoiding external transportation, reducing the amount of purchased sand and gravel, greatly reducing construction costs, and is suitable for large-scale promotion and application.

[0154] Therefore, it is evident that the objective of this invention has been fully and effectively achieved. The function and structural principles of this invention have been demonstrated and explained in the embodiments. Any modifications can be made to the implementation methods without departing from these principles. Therefore, this invention includes all modified embodiments based on the spirit and scope of the claims.

Claims

1. A composite reagent for flocculating and solidifying slag in pile foundations, characterized in that, Includes composite flocculants and ternary curing agents, wherein: The composite flocculant includes polyacrylamide and bentonite modifier, with a mass ratio of polyacrylamide to bentonite modifier of 8:2~14. The ternary curing agent consists of cement, desulfurized gypsum, and metakaolin. The desulfurized gypsum accounts for 8% to 12% of the mass of cement, and the metakaolin accounts for 5% to 8% of the mass of cement.

2. The pile foundation slag flocculation and solidification combined reagent as described in claim 1, characterized in that, The bentonite modifier is sodium-based bentonite with a cationic quaternary ammonium salt surface modified.

3. The pile foundation slag flocculation and solidification combined reagent as described in claim 2, characterized in that, The cationic quaternary ammonium salt is octadecyltrimethylammonium chloride.

4. The pile foundation slag flocculation and solidification combined reagent as described in claim 1, characterized in that, The cement is ordinary Portland cement.

5. A construction method for flocculation solidification and in-situ reuse of pile foundation slag, applicable to pile foundations with an empty pile depth of 2m~4m and an empty pile diameter of 0.8m~2.0m, characterized in that, The construction method for flocculation solidification and in-situ reuse of pile foundation slag adopts the pile foundation slag flocculation solidification combination reagent as described in any one of claims 1 to 4 and includes the following steps: (1) Pre-treat and screen the pile foundation slag to control the maximum particle size of coarse particles to not exceed 40 mm, and crush or remove the excess particles. (2) Test the sand content of the pile foundation slag and control the sand content of the pile foundation slag to 12%~22%: (21) If the sand content of the pile foundation slag is between 12% and 22%, proceed to step (3). (22) If the sand content of the pile foundation slag is >22%, fine-grained soil is added, wherein the proportion of particles with a diameter ≥0.075mm in the fine-grained soil is <5%, and the sand content of the fine-grained soil is <5%, so that the sand content of the pile foundation slag is between 12% and 22%, and then step (3) is carried out. (23) If the sand content of the pile foundation slag is <12%, clean sand is added, and the mud content of the clean sand is <3%, so that the sand content of the pile foundation slag is between 12% and 22%, and then step (3) is carried out. (3) The content of wall slurry in pile foundation slag is detected by burning method: Take an appropriate amount of pile foundation slag sample, first dry it at 105℃ to a constant mass, and weigh it to obtain the dry weight m1; then burn the dried product at 550℃ for 2 hours, and after cooling, weigh it to obtain the mass of the residue m2. The wall slurry content of pile foundation slag = (m1- m2) / m1x100%. If the wall slurry content of pile foundation slag is ≤8%, the dosage of polyacrylamide is 0.4‰ of the dry soil mass of pile foundation slag, the dosage of bentonite modifier is 0.1‰ of the dry soil mass of pile foundation slag, and the dosage of cement is 3%~5% of the dry soil mass of pile foundation slag. If the wall slurry content of pile foundation slag is >8%, then for every 1% increase in the wall slurry content of pile foundation slag, the dosage of bentonite modifier increases by 0.05‰ of the dry soil mass of pile foundation slag. (4) Reagent preparation: (41) Preparation of composite flocculant solution: Prepare 12 hours in advance by sealing and stirring polyacrylamide, bentonite modifier and water, then filtering to obtain the composite flocculant solution, wherein the total mass concentration of polyacrylamide and bentonite modifier is 0.2%; (42) The ternary curing agent is prepared by a step-by-step mixing process: cement and metakaolin are mixed for the first time, and then desulfurized gypsum is added for the second mixing to obtain the ternary curing agent; (5) Flocculation and solidification: (51) Composite flocculation one-time mixing: The pile foundation slag and composite flocculation solution are mixed once, so that the proportion of aggregates with a particle size ≥1mm in the mixing product is ≥80%, the moisture content is below 40%, and there is no obvious slurry on the surface. (52) Gradient curing and secondary stirring: Add ternary curing agent to the stirring product, stir at low speed first, then stir at high speed to obtain the cured product, and conduct an unconfined compressive strength test on the cured product to ensure that the compressive strength reaches more than 0.3 MPa after 24 hours. (6) Pretreatment and backfilling of empty pile walls: (61) Pretreatment of pile wall: a permeable casing is used. Multiple permeable holes are opened in the casing wall of the permeable casing. The multiple permeable holes are set at intervals. The burial depth of the permeable casing is 1 / 3 of the depth of the empty pile. An air compressor is used to blow the remaining pile wall of the empty pile to remove the loose soil layer. The water accumulated at the bottom of the empty pile is pumped out by a submersible pump. (62) Layered backfilling: Backfill in layers according to the depth of the empty pile. After each layer is poured, compaction is carried out. After compaction, the compaction degree and surface flatness are tested. If they are qualified, the next layer can be constructed. If the diameter of the empty pile is ≥1.5m, a vibrator is inserted when pouring each layer to avoid voids in the middle. (7) Maintenance: After pouring to the top surface of the empty pile, cover it with geotextile and plastic film for temperature and humidity control within 2 hours.

6. The construction method for flocculation solidification and in-situ reuse of pile foundation slag as described in claim 5, characterized in that, In step (22), the fine-grained soil is silty clay or silt; in step (23), the clean sand is river sand or manufactured sand.

7. The construction method for flocculation solidification and in-situ reuse of pile foundation slag as described in claim 5, characterized in that, In step (3), drying is carried out in a constant temperature oven and calcination is carried out in a muffle furnace.

8. The construction method for flocculation solidification and in-situ reuse of pile foundation slag as described in claim 5, characterized in that, In step (41), the closed stirring is carried out in a closed stirring tank, the temperature of the closed stirring is 20℃~25℃, the speed of the closed stirring is 300r / min, the time of the closed stirring is 90 minutes, and the filtration is carried out using a 100-mesh filter screen; in step (42), the speed of the first stirring is 100r / min, and the time of the first stirring is 30 minutes; the speed of the second stirring is 80r / min, and the time of the second stirring is 30 minutes.

9. The construction method for flocculation solidification and in-situ reuse of pile foundation slag as described in claim 5, characterized in that, In step (51), a forced mixer is used for one stirring, the stirring speed is 50 r / min to 80 r / min, and the stirring time is 3 minutes; in step (52), the low speed is 40 r / min and the low speed time is 1 minute; the high speed is 100 r / min and the high speed time is 2 minutes.

10. The construction method for flocculation solidification and in-situ reuse of pile foundation slag as described in claim 5, characterized in that, In step (61), the permeable casing is a permeable steel casing with permeable holes of 10mm in diameter and 15cm in spacing, arranged in a quincunx pattern; in step (62), the thickness of each layer is 35cm~45cm, and the compaction is performed 3 times; or, In step (7), when the ambient temperature is below 12°C, an electric heating blanket is placed over the outside of the plastic film for heating, and when the ambient temperature is above 28°C, the spray system is turned on for spraying; the curing time is no less than 5 days.