Method for preparing flow-state solidified soil from high-liquid-limit mucky shield muck

Abstract

The invention discloses a method for preparing flow-state solidified soil by utilizing high-liquid-limit mucky shield muck, which comprises the following steps: firstly, preparing a composite curing agent by adjusting the formula proportion of industrial byproducts including carbide slag, slag, fly ash and phosphogypsum as well as calcium formate and sodium hexametaphosphate; secondly, the shield muck is pretreated, and pretreated slurry meeting the requirement is obtained; and finally, a composite curing agent is added into the pretreated slurry, the water content of the mixed slurry is controlled to be 130-160%, all components in the composite curing agent and the pretreated slurry are subjected to full contact reaction through stirring, and therefore the fluid-state solidified soil meeting the backfilling requirement is obtained. Calcium formate and sodium hexametaphosphate are introduced into a traditional industrial by-product curing agent formula, the rheological property of the slurry is dynamically regulated and controlled, and harmless treatment and resource utilization of the waste resource high-liquid-limit mucky shield muck are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of civil engineering materials and solid waste resource utilization, and particularly relates to a method for preparing fluidized solidified soil by utilizing high liquid limit muddy shield slag. Background Art

[0002] Shield excavation refers to the earth, rock, and waste generated by the cutting, crushing, and excavation operations at the bottom of the shield machine during shield construction. With the rapid development of urbanization and urban underground rail transit in my country, as well as the continuous improvement of urban underground pipeline networks, the output of shield excavation is becoming increasingly large. Traditional landfill or disposal methods not only cause environmental pollution, waste resources, and pose safety hazards, but also, as suburban landfill sites become saturated or overloaded, the cost and difficulty of excavation are increasing. How to harmlessly dispose of this shield excavation and recycle it as a resource remains a difficult problem that needs to be solved.

[0003] Fluidized solidified soil is a new type of geotechnical engineering material. It is obtained by mixing soil from the site with a curing agent and other additives, creating a fluid mixture. After pouring or filling and curing, it solidifies into a new engineering material with a certain strength, water stability, low permeability, and long-term stability. However, the curing agent is mostly cement, a high-carbon emission material that is not conducive to environmental protection.

[0004] Therefore, how to provide a method for preparing fluidized solidified soil using high liquid limit muddy shield slag, design a composite curing agent using industrial by-products such as calcium carbide slag and slag, and apply it to the preparation of fluidized solidified soil in shield slag to meet the backfill construction of construction foundation pits is a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing fluidized solidified soil using high liquid limit muddy shield slag, so as to solve at least one of the above-mentioned technical problems.

[0006] To achieve the above-mentioned objectives, the first aspect of the present invention provides a method for preparing fluidized solidified soil using high liquid limit muddy shield slag, the method comprising: preparing a composite curing agent, the composite curing agent comprising the following components in parts by weight: 10-25 parts of carbide slag, 30-40 parts of slag, 10-20 parts of fly ash, 10-20 parts of phosphogypsum, 3-5 parts of calcium formate and 1-3 parts of sodium hexametaphosphate; pretreating the shield slag to obtain a pretreated slurry; adding the composite curing agent to the pretreated slurry, controlling the moisture content to 130-160%, stirring for 5-10 minutes, and obtaining fluidized solidified soil; wherein the amount of the composite curing agent added is 15-30% of the dry soil mass of the shield slag; the fluidized solidified soil has a flow value of 160-200 mm and a 28d unconfined compressive strength ≥2.5 MPa.

[0007] In the first aspect, the shield slag is pretreated to obtain pretreated slag, including: when the shield slag is shield mud cake, using a wire cutting machine to crush it to a particle size of less than 0.5 cm to obtain a pretreated slurry; when the shield slag is shield mud, adding calcium carbide slag to the shield mud, the amount of calcium carbide slag added is 2-8% of the mass of the shield mud, stirring evenly, standing for 30 minutes, removing the upper clear liquid, and obtaining a pretreated slurry.

[0008] In the first aspect, the liquid limit of the shield mud cake is 50-70%, and the organic matter content is ≤5%.

[0009] In the first aspect, the water content of the shield slurry is 300-400%.

[0010] In the first aspect, the content of Ca(OH)2 in the carbide slag is ≥90%, and the fineness is ≤0.075mm.

[0011] In the first aspect, the slag is granulated blast furnace slag with a specific surface area of ​​≥400m 2 / kg, vitreous content ≥90%.

[0012] In the first aspect, the fly ash is Grade II or above, with a loss on ignition of ≤8% and a total content of SiO2 and Al2O3 of ≥75%.

[0013] In the first aspect, the content of CaSO4·2H2O in the phosphogypsum is ≥85%, and the content of soluble P2O5 is ≤1.5%.

[0014] In the first aspect, the purity of the calcium formate is ≥98% and the particle size is ≤30 μm.

[0015] In the first aspect, the purity of the sodium hexametaphosphate is ≥95%, and the degree of polymerization is 6-8.

[0016] Beneficial effects: The present invention provides a method for preparing fluidized solidified soil using high-liquid-limit muddy shield slag. First, a composite curing agent is prepared by adjusting the formula ratio between industrial by-products such as carbide slag, slag, fly ash, and phosphogypsum, as well as calcium formate and sodium hexametaphosphate; then, the shield slag is pretreated to obtain a pretreated slurry that meets the requirements; finally, the composite curing agent is added to the pretreated slurry, and the moisture content of the mixed slurry is controlled to 130-160%. By stirring, each component in the composite curing agent is fully contacted and reacted with the pretreated slurry, thereby obtaining fluidized solidified soil that meets the backfill requirements. The present invention dynamically regulates the rheological properties of the slurry by introducing calcium formate and sodium hexametaphosphate into the traditional industrial by-product curing agent formula, thereby achieving harmless treatment and resource utilization of waste resource high-liquid-limit muddy shield slag.

[0017] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific embodiments and examples are for illustrating the present invention, rather than for limiting the present invention.

[0019] Throughout this specification, unless otherwise specified, the terms used herein should be understood as having the same meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In the event of any conflict, the present specification shall take precedence.

[0020] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or obtained through existing methods.

[0021] The present invention uses shield slag (shield mud or shield mud cake) as raw material, and adds a composite curing agent with an optimized formula to the shield slag slurry to achieve rapid stabilization and fluidization of the slurry, thereby preparing fluidized solidified soil for use in backfill construction of working areas such as urban integrated pipeline corridors and building foundation pits; wherein the composite curing agent includes the following components in parts by weight: 10-25 parts of calcium carbide slag, 30-40 parts of slag, 10-20 parts of fly ash, 10-20 parts of phosphogypsum, 3-5 parts of calcium formate and 1-3 parts of sodium hexametaphosphate.

[0022] In the present invention, when the shield slag is shield mud, due to its high water content, it is necessary to first add carbide slag to the shield mud for rapid dehydration to remove excess water, so that the composite curing agent added later can be quantified. In a specific embodiment, the Ca dissolved and released in the carbide slag 2+ Neutralize the negative charge on the surface of shield mud particles, destroy the colloid stability through double layer compression, form flocculent structure, and combine OH - Promote colloid coagulation, accelerate the release of free water, and achieve rapid dehydration of shield mud. When the shield slag is in the form of shield mud cake, its water content is relatively low and the particles are large. To facilitate subsequent mixing, the shield mud cake is crushed to reduce the particle size of the shield mud cake, increase the reaction contact area with the composite curing agent, and the water removed during shield mud dehydration can be added during the reaction and stirring process, realizing multi-level utilization of water resources.

[0023] In the present invention, the main component of carbide slag in the composite curing agent is Ca(OH)2, which can be used as an alkaline activator and flocculant; the active SiO2 and Al2O3 in the slag are dissolved, diffused, and polymerized under alkaline conditions, and in the presence of high concentrations of Ca 2+ Under alkaline conditions, calcium aluminosilicate hydrate (CASH) gel is formed to cement the slurry particles. The high content of active SiO2 and Al2O3 and high specific surface area in fly ash give it a microaggregate effect and react with the pozzolanic ash in the later stage. Its unique spherical shape can reduce the interfacial friction between the mixture and promote the fluidity of the slurry. The main component of phosphogypsum is CaSO4·2H2O. Under alkaline conditions, it reacts with CASH gel to form ettringite, a hydration product with high bound water, which consumes Ca(OH)2 and Al2O3 to promote slag dissolution and improve the early strength of the slurry. Calcium formate and sodium hexametaphosphate synergistically regulate the rheological properties of the slurry to achieve a reaction equilibrium with the composite curing agent.

[0024] In the present invention, the reaction mechanism of the composite curing agent and the shield slurry is as follows: OH released by dissolution in carbide slag - It can activate the amorphous glass in slag and fly ash, dissociating it into silicon-oxygen tetrahedron [SiO4] 4- and aluminum oxide tetrahedron [AlO4] 5- , and in Ca 2+ Under supersaturated conditions, calcium silicate hydrate (CSH) and calcium silicate aluminate hydrate (CASH) gels are generated to cement slurry particles and fill pores, forming a dense structure and providing mechanical strength for fluidized solidified soil. In addition, phosphogypsum generates ettringite with active alumina in an alkaline environment, consuming Ca(OH)2 and Al 3+ , and promote the continuous dissolution of slag, forming a positive feedback loop, promoting each other and stimulating the potential activity of slag and fly ash.

[0025] Calcium formate plays a multi-level synergistic strengthening role in the curing system: at the solid-liquid interface, the Ca released after the dissolution of calcium formate 2+ The negative charge on the surface of the slurry particles is neutralized by electrostatic action, and the stability of the sludge colloid is effectively destroyed by double-layer compression. At the same time, its weak alkalinity (pH≈8-9) buffers the strong alkaline environment of the carbide slag (pH>12), avoiding OH - The mineral structure dissociation caused by excessive concentration; at the gelation reaction level, the soluble Ca provided by calcium formate 2+ Selective dissolution occurs at the interface with the active SiO2 and Al2O3 in the slag, promoting the nucleation and growth of CASH gel through the “dissolution-diffusion-precipitation” mechanism, while SO4 2- The presence of HCOO induces the directional crystallization of ettringite in the gel pores, forming a needle-rod structure. It is particularly noteworthy that the formate ion (HCOO - ) regulates Ca through coordination 2+ The release kinetics of the CASH gel are optimized, achieving a dynamic balance between the interfacial reaction rate and product transport, thus avoiding microstructural defects caused by localized, excessively rapid gel deposition. This multi-scale regulation ultimately forms a composite gelling system with CASH gel as the continuous phase, ettringite as the reinforcing phase, and unreacted particles as the skeleton. This reduces porosity and the thickness of the interfacial transition zone, significantly improving mechanical properties and durability.

[0026] Sodium hexametaphosphate (SHMP) significantly improves the performance of fluidized soil through the synergistic effect of multi-scale interface regulation and gelation reaction: From the perspective of interface chemistry, the long-chain polyphosphate ([NaPO3]6 6- ) is wrapped around the surface of slurry particles and cementitious materials through strong electrostatic adsorption, and its high negative charge density can effectively inhibit the Ca 2+ At the same time, the steric hindrance effect inhibits the aggregation of particles and significantly improves the rheological properties of the slurry. At the gelling reaction level, the chelation effect of SHMP preferentially reacts with the Ca2+ released by the dissolution of phosphogypsum. 2+ Formation of [Ca(PO3)6] 4- This "calcium buffer effect" not only delays the explosive generation of ettringite, but also ensures the continuous supply of Ca required for the dissolution of slag / fly ash. 2+ , so that the generation rate of CSH gel and the crystallization of ettringite reach a kinetic equilibrium.

[0027] The performance of the fluidized solidified soil prepared in the present invention was tested in the following manner: 1. Flow value test method: The flow value test device consists of a plexiglass plate and a plexiglass cylinder with a height of 80 mm and a diameter of 80 mm. During the test, the inner wall of the plexiglass cylinder and the surface of the plexiglass plate are both wetted. The fluidized solidified soil is loaded into the plexiglass cylinder. During the loading process, it is continuously vibrated to ensure that the sample is dense. After it is full, the surface is scraped flat with a scraper, and the sample spilled on the outer cylinder wall and the plate is wiped off with a rag. After the sample is loaded, the plexiglass cylinder is gently lifted vertically upward. After 30 seconds, the maximum and minimum diameters of the mixture after spreading are measured with a steel ruler, and the average of the two is taken as the flow value. To ensure the reliability of the test, each group of samples needs to be tested in parallel 2-3 times, and the average value is used as the final flow value.

[0028] 2. Unconfined compressive strength test: The unconfined compressive strength test is carried out in accordance with the "Standard for Geotechnical Experimental Methods" (GB / T50123-1999); the instrument used in the test is the WDW-100 strain-controlled unconfined pressure instrument produced by Jinan Zhongzheng Co., Ltd., with a loading rate of 1 mm / min; in order to ensure the reliability of the test, each group of specimens is subject to 2-3 parallel tests, and the average value is used as the final unconfined compressive strength.

[0029] Example 1 In this embodiment, shield slurry with a moisture content of 350% is used as the shield slag raw material. The specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 20 parts of carbide slag, 30 parts of slag, 20 parts of fly ash, 20 parts of phosphogypsum, 4 parts of calcium formate and 2 parts of sodium hexametaphosphate; (2) Add 6% of the mass of the shield mud to the shield mud, stir for 5 minutes, let it stand for 30 minutes, and remove the supernatant to obtain the pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 20% of the dry soil mass of the shield mud. The moisture content of the mixed slurry is controlled between 130-160%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0030] After testing, the flow value of the fluidized solidified soil is 180mm, the 7d unconfined compressive strength is 0.8MPa, and the 28d unconfined compressive strength is 2.9MPa, which meets the backfill requirements of urban integrated pipeline corridors, building foundation pits and other work areas.

[0031] Example 2 In this embodiment, shield slurry with a moisture content of 300% is used as the shield slag raw material. The specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 20 parts of carbide slag, 40 parts of slag, 20 parts of fly ash, 15 parts of phosphogypsum, 3 parts of calcium formate and 3 parts of sodium hexametaphosphate; (2) Add 4% of the mass of carbide slag to the shield mud, stir for 5 minutes, let it stand for 30 minutes, and remove the supernatant to obtain the pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 30% of the dry soil mass of the shield mud. The moisture content of the mixed slurry is controlled between 130-160%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0032] After testing, the flow value of the fluidized solidified soil is 160mm, the 7d unconfined compressive strength is 1.6MPa, and the 28d unconfined compressive strength is 3.15MPa, which meets the backfill requirements of work areas such as urban integrated pipeline corridors and building foundation pits.

[0033] Example 3 In this embodiment, shield mud cake with a liquid limit of 55% is used as shield slag raw material. The specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 15 parts of carbide slag, 40 parts of slag, 15 parts of fly ash, 20 parts of phosphogypsum, 5 parts of calcium formate and 2 parts of sodium hexametaphosphate; (2) Using a wire cutting machine to crush the shield mud cake to a particle size of 0.25 cm to obtain pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 20% of the dry mass of shield mud. Water is added to control the moisture content of the mixed slurry to 154%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0034] After testing, the flow value of the fluidized solidified soil is 190mm, the 7d unconfined compressive strength is 0.76MPa, and the 28d unconfined compressive strength is 2.61MPa, which meets the backfill requirements of urban integrated pipeline corridors, building foundation pits and other work areas.

[0035] Example 4 In this embodiment, shield mud cake with a liquid limit of 50% is used as shield slag raw material. The specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 15 parts of carbide slag, 40 parts of slag, 10 parts of fly ash, 20 parts of phosphogypsum, 3 parts of calcium formate and 1 part of sodium hexametaphosphate; (2) Using a wire cutting machine to crush the shield mud cake to a particle size of 0.3 cm to obtain pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 30% of the dry soil mass of the shield mud. Water is added to control the moisture content of the mixed slurry to 150%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0036] After testing, the flow value of the fluidized solidified soil is 185mm, the 7d unconfined compressive strength is 0.96MPa, and the 28d unconfined compressive strength is 3.52MPa, which meets the backfill requirements of urban integrated pipeline corridors, building foundation pits and other work areas.

[0037] Comparative Example 1 In this comparative example, shield mud with a moisture content of 350% is used as the shield slag raw material, and the specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 50 parts of carbide slag, 10 parts of slag, 30 parts of fly ash, 6 parts of phosphogypsum and 1 part of sodium hexametaphosphate; (2) Add 4% of the mass of carbide slag to the shield mud, stir for 5 minutes, let it stand for 30 minutes, and remove the supernatant to obtain the pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 30% of the dry soil mass of the shield mud. The moisture content of the mixed slurry is controlled between 130-160%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0038] After testing, the flow value of the fluidized solidified soil is 150mm, the 7d unconfined compressive strength is 0.14MPa, and the 28d unconfined compressive strength is 0.27MPa, which cannot meet the backfill requirements of work areas such as urban integrated pipeline corridors and building foundation pits.

[0039] Comparative Example 2 In this comparative example, shield mud with a moisture content of 300% is used as the shield slag raw material, and the specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 20 parts of carbide slag, 40 parts of slag, 10 parts of fly ash, 20 parts of phosphogypsum, 0.5 parts of calcium formate and 1 part of sodium hexametaphosphate; (2) Add composite curing agent to the shield mud. The amount of composite curing agent added is 20% of the dry soil mass of the shield mud. The water content of the mixed slurry is controlled between 150-180%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0040] After testing, the flow value of the fluidized solidified soil is 220mm, the 7d unconfined compressive strength is 0.15MPa, and the 28d unconfined compressive strength is 0.28MPa, which cannot meet the backfill requirements of work areas such as urban integrated pipeline corridors and building foundation pits.

[0041] Comparative Example 3 In this comparative example, shield mud with a moisture content of 300% is used as the shield slag raw material, and the specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 20 parts of carbide slag, 40 parts of slag, 15 parts of fly ash, 15 parts of phosphogypsum and 3 parts of sodium hexametaphosphate; (2) Add 6% of the mass of the shield mud to the shield mud, stir for 5 minutes, let it stand for 30 minutes, and remove the supernatant to obtain the pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 20% of the dry soil mass of the shield mud. The moisture content of the mixed slurry is controlled between 130-160%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0042] After testing, the flow value of the fluidized solidified soil is 200mm, the 7d unconfined compressive strength is 0.3MPa, and the 28d unconfined compressive strength is 1.28MPa, which cannot meet the backfill requirements of work areas such as urban integrated pipeline corridors and building foundation pits.

[0043] Comparative Example 4 In this comparative example, shield mud with a moisture content of 300% is used as the shield slag raw material, and the specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 20 parts of carbide slag, 40 parts of slag, 20 parts of fly ash, and 20 parts of phosphogypsum; (2) Add 6% of the mass of the shield mud to the shield mud, stir for 5 minutes, let it stand for 30 minutes, and remove the supernatant to obtain the pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 20% of the dry soil mass of the shield mud. The moisture content of the mixed slurry is controlled between 130-160%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0044] After testing, the flow value of the fluidized solidified soil is 152mm, the 7d unconfined compressive strength is 0.6MPa, and the 28d unconfined compressive strength is 2.0MPa, which cannot meet the backfill requirements of work areas such as urban integrated pipeline corridors and building foundation pits.

[0045] Comparative Example 5 In this comparative example, shield mud cake with a liquid limit of 55% is used as the shield slag raw material. The specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 30 parts of carbide slag, 30 parts of slag, 40 parts of fly ash, 0.3 parts of calcium formate and 0.8 parts of sodium hexametaphosphate; (2) Using a wire cutting machine to crush the shield mud cake to a particle size of 0.25 cm to obtain pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 20% of the dry mass of shield mud. Water is added to control the moisture content of the mixed slurry to 140%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0046] After testing, the flow value of the fluidized solidified soil is 130mm, the 7d unconfined compressive strength is 0.17MPa, and the 28d unconfined compressive strength is 0.24MPa, which cannot meet the backfill requirements of work areas such as urban integrated pipeline corridors and building foundation pits.

[0047] Comparative Example 6 In this comparative example, shield mud cake with a liquid limit of 50% is used as the shield slag raw material, and the specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 30 parts of carbide slag, 25 parts of slag, 45 parts of phosphogypsum, 0.3 parts of calcium formate and 1 part of sodium hexametaphosphate; (2) Using a wire cutting machine to crush the shield mud cake to a particle size of 0.3 cm to obtain pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 30% of the dry soil mass of the shield mud. Water is added to control the moisture content of the mixed slurry to 150%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0048] After testing, the flow value of the fluidized solidified soil is 145mm, the 7d unconfined compressive strength is 0.05MPa, and the 28d unconfined compressive strength is 0.19MPa, which cannot meet the backfill requirements of work areas such as urban integrated pipeline corridors and building foundation pits.

[0049] Comparative Example 7 In this comparative example, shield mud cake with a liquid limit of 50% is used as the shield slag raw material, and the specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 35 parts of carbide slag, 30 parts of slag, 20 parts of fly ash, 15 parts of phosphogypsum and 1 part of sodium hexametaphosphate; (2) Using a wire cutting machine to crush the shield mud cake to a particle size of 0.3 cm to obtain pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 30% of the dry soil mass of the shield mud. Water is added to control the moisture content of the mixed slurry to 150%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0050] After testing, the flow value of the fluidized solidified soil is 155mm, the 7d unconfined compressive strength is 0.45MPa, and the 28d unconfined compressive strength is 1.22MPa, which cannot meet the backfill requirements of work areas such as urban integrated pipeline corridors and building foundation pits.

[0051] Comparative Example 8 In this comparative example, shield mud cake with a liquid limit of 50% is used as the shield slag raw material, and the specific steps for preparing fluidized solidified soil are as follows: (1) preparing a composite curing agent, the composite curing agent consisting of 15 parts of carbide slag, 65 parts of slag, 12 parts of fly ash, and 8 parts of phosphogypsum; (2) Using a wire cutting machine to crush the shield mud cake to a particle size of 0.3 cm to obtain pretreated slurry; (3) Add composite curing agent to the pretreated slurry. The amount of composite curing agent added is 30% of the dry soil mass of the shield mud. Water is added to control the moisture content of the mixed slurry to 150%. After stirring for 5 minutes, fluidized solidified soil is obtained.

[0052] After testing, the flow value of the fluidized solidified soil is 140mm, the 7d unconfined compressive strength is 0.52MPa, and the 28d unconfined compressive strength is 1.75MPa, which cannot meet the backfill requirements of work areas such as urban integrated pipeline corridors and building foundation pits.

[0053] In summary, compared with the prior art, the method provided by the present invention for preparing fluidized solidified soil using high liquid limit muddy shield tunneling soil has the following advantages: (1) The present invention adopts the method of adding carbide slag in advance to shield tunneling mud with a high water content to achieve rapid dehydration, thereby providing a dense matrix for the subsequent solidification reaction.

[0054] (2) The present invention provides a novel composite curing agent, which introduces calcium formate and sodium hexametaphosphate into industrial by-products such as carbide slag, slag, fly ash and phosphogypsum, and combines flocculation dehydration with chemical curing mechanisms to achieve multi-stage regulation of the gelling reaction of shield slurry, thereby improving the treatment efficiency of high liquid limit silty shield slag.

[0055] (3) The present invention realizes resource utilization and harmless treatment of shield tunneling slag by pre-treating the shield tunneling slag and optimizing the formula ratio of the composite curing agent, and has the advantages of low cost, strong environmental protection, and good construction adaptability.

[0056] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0057] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0058] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing fluidized solidified soil using high liquid limit muddy shield slag, characterized in that: The method comprises: Prepare a composite curing agent, which comprises the following components in parts by weight: 10-25 parts of carbide slag, 30-40 parts of slag, 10-20 parts of fly ash, 10-20 parts of phosphogypsum, 3-5 parts of calcium formate and 1-3 parts of sodium hexametaphosphate; Pre-treating shield slag to obtain pre-treated slurry; Add the composite curing agent to the pretreated slurry, control the moisture content to 130-160%, and stir for 5-10 minutes to obtain fluidized solidified soil; The addition amount of the composite curing agent is 15-30% of the dry soil mass of the shield slag; the flow value of the fluidized solidified soil is 160-200 mm, and the 28d unconfined compressive strength is ≥2.5 MPa.

2. The method for preparing fluidized solidified soil using high liquid limit muddy shield slag according to claim 1, characterized in that: The pre-processing of shield slag to obtain pre-processed slag includes: When the shield slag is shield mud cake, it is crushed to a particle size of less than 0.5 cm using a wire cutting machine to obtain pre-treated slurry; When the shield slag is shield mud, carbide slag is added to the shield mud, and the amount of carbide slag added is 2-8% of the mass of the shield mud. After stirring evenly, it is allowed to stand for 30 minutes, and the supernatant is removed to obtain a pretreated slurry.

3. The method for preparing fluidized solidified soil using high liquid limit muddy shield tunneling soil according to claim 2, characterized in that: The liquid limit of the shield mud cake is 50-70%, and the organic matter content is ≤5%.

4. The method for preparing fluidized solidified soil using high liquid limit muddy shield tunneling soil according to claim 2, characterized in that: The water content of the shield slurry is 300-400%.

5. The method for preparing fluidized solidified soil using high liquid limit muddy shield slag according to claim 1, characterized in that: The content of Ca(OH)2 in the carbide slag is ≥90%, and the fineness is ≤0.075mm.

6. The method for preparing fluidized solidified soil using high liquid limit muddy shield tunneling soil according to claim 1, characterized in that: The slag is granulated blast furnace slag with a specific surface area of ​​≥400m 2 / kg, vitreous content ≥90%.

7. The method for preparing fluidized solidified soil using high liquid limit muddy shield tunneling debris according to claim 1, characterized in that: The fly ash is Grade II or above, with a loss on ignition of ≤8% and a total content of SiO2 and Al2O3 of ≥75%.

8. The method for preparing fluidized solidified soil using high liquid limit muddy shield tunneling debris according to claim 1, characterized in that: The content of CaSO4·2H2O in the phosphogypsum is ≥85%, and the content of soluble P2O5 is ≤1.5%.

9. The method for preparing fluidized solidified soil using high liquid limit muddy shield tunneling debris according to claim 1, characterized in that: The purity of the calcium formate is ≥98%, and the particle size is ≤30 μm.

10. The method for preparing fluidized solidified soil using high liquid limit muddy shield tunneling soil according to claim 1, characterized in that: The purity of the sodium hexametaphosphate is ≥95%, and the degree of polymerization is 6-8.