Regenerated low-strength neutral solidified soil based on river and lake sludge in-situ preparation and method

Abstract

The invention belongs to the field of engineering solid waste resource reutilization and environmental sustainable development, and discloses a method for in-situ preparation of regenerated low-strength neutral solidified soil based on river and lake sludge, which realizes preparation of regenerated plant soil by dredging river and lake sludge through drying and desertification, disinfection and sterilization, conditioning and fertility increasing, neutral solidification and oxygenation and water retention. The preparation method comprises the steps of drying and desertification, and doping of the stone powder, the building powder, the paper pulp waste residues and the coffee grounds. Disinfecting and sterilizing, and doping calcium superphosphate, active attapulgite, a ferrous sulfate water solution and a sulfur water suspension; hardening, tempering and fertility increasing are conducted, and wood flour, leaf powder and vinasse which are fermented and mixed are mixed; neutral solidification: doping a curing agent to prepare neutral solidified soil; and adding calcium peroxide particles and high-molecular water-absorbent resin. According to the preparation method, a large amount of dredging river and lake sludge can be effectively recycled, and the problems of high treatment cost and low environmental benefits of a large amount of dredging river and lake sludge at present are effectively solved, so that the preparation method has good economic benefits and environmental benefits.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of engineering solid waste resource recycling and environmental sustainable development, and particularly relates to a method for preparing regenerated low-strength neutral solidified soil based on in-situ river and lake sludge. BACKGROUND

[0002] The pollutants in the river and lake sludge can cause significant changes in the physical and chemical properties of water quality and geology, and the water body function is basically lost. The sludge can emit toxic substances, affecting the living environment and health of the surrounding residents and the ecological environment safety. Therefore, effective treatment and repair of river sludge pollution is very important.

[0003] The existing sludge treatment method mainly has high cost, is not environmentally friendly, and the treated sludge cannot be directly used as plant soil. For example, the application number CN202310430664.0 discloses a sludge solidification method, specifically discloses the components and weight percentages of the adsorption modified material: 20-80 parts of regenerated mechanism sand dust collection powder, 10-50 parts of decoration waste powder grinding material, and 10-60 parts of regenerated brick aggregate; the components and weight percentages of the solidification enhancing material: 75-90 parts of ordinary cement, 5-25 parts of aluminate cement, 0.5-5 parts of early strength agent, and 0.03-1 parts of setting retarder. The patent adds the adsorption modified material but does not solve the problem of high water content of the sludge, which is too thin to mix. At the same time, the use of cement in the solidification component not only has high cost, but also causes serious pollution and energy consumption to the environment.

[0004] The application number CN202211058464.9 discloses a river and lake sludge conditioning solidifier and a conditioning method, specifically discloses that the solidifier includes slag powder, fly ash, gypsum, acrylic modified carbide slag, conditioning agent, and construction waste aggregate. The patent can only adjust the pH of the water after the sludge is dewatered, and the sludge is still alkaline, which cannot be used as plant soil.

[0005] The application number CN202410337290.2 discloses a dredged sludge solidification method, specifically discloses that the raw materials of the composite solidifier include quicklime, cement, salt activator, and coagulant aid, and the quicklime, cement, salt activator, and coagulant aid are mixed and stirred uniformly to obtain the composite solidifier. The patent does not disinfect and sterilize the sludge, and uses quicklime, cement, salt activator, and coagulant aid as the solidifier, which aggravates the salinity and alkalinity of the sludge and is not environmentally friendly.

[0006] The present application provides a regenerated plant soil with low cost and high environmental friendliness to meet the needs of production and life. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application aims to provide a method for preparing regenerated low-strength neutral solidified soil based on river and lake sludge in situ, which uses paper pulp waste residue and coffee residue to reduce the water content of the sludge, uses phosphogypsum, slag powder and red mud as the neutral solidifying agent, and uses calcium superphosphate, ferrous sulfate aqueous solution and sulfur water suspension to disinfect and sterilize, thereby preparing a low-strength, low-cost and high-environmental-friendliness regenerated planting soil for dredged river and lake sludge. The method effectively solves the problems of high disposal cost and low environmental benefit of a large amount of dredged river and lake sludge, is suitable for the solidification and regeneration of dredged river and lake sludge, and can effectively reuse the sludge, reduce environmental pollution and improve economic benefits.

[0008] To solve the problems of the prior art, the technical scheme adopted by the present application is as follows: A method for preparing regenerated low-strength neutral solidified soil based on river and lake sludge in situ, comprising the following steps: S1, sludge drying and sanding; the drying step is: taking the sludge in situ, mixing paper pulp waste residue and coffee residue into the sludge, and mixing uniformly; absorbing water to reduce the water content in the sludge to below 20%; the sanding step is: mixing stone powder and building powder, and mixing uniformly; sanding the sludge to reduce the viscosity of the sludge and make it easy to mix.

[0009] S2, sterilization and disinfection; the disinfection step is: mixing calcium superphosphate and active attapulgite, and mixing uniformly; ion exchange and adsorption of heavy metals are achieved; The sterilization step is: mixing ferrous sulfate aqueous solution and sulfur water suspension, and mixing uniformly; pathogenic microorganisms are eliminated. The effects of precipitating heavy metals and eliminating pathogenic microorganisms are achieved.

[0010] S3, fertilization and conditioning; wood chip powder, leaf powder and vinasse after fermentation are mixed and then mixed into the soil to adjust the soil quality.

[0011] S4, neutral solidification; a solidifying agent is mixed uniformly, and the pH is adjusted to neutral; the raw materials of the solidifying agent are phosphogypsum, slag powder, red mud and straw.

[0012] S5, oxygenation and water retention; calcium peroxide particles and high-molecular-weight water-absorbing resin are mixed to obtain sludge regeneration solidified soil.

[0013] It should be noted that all the relative dry soil weights in the present application are sludge dry soil with a relative water content of 0%.

[0014] Preferably, in the step S1, the mixing amount of the paper pulp waste residue and coffee residue is 10-20% of the relative dry soil weight, and the weight ratio of the paper pulp waste residue and coffee residue is 0.8-1.2:1; the mixing amount of the stone powder and building powder is 20-30% of the relative dry soil weight, and the weight ratio of the stone powder and building powder is 1.2-2.3:1.

[0015] Preferably, in step S2, 1-2% of superphosphate and 1-2% of activated attapulgite relative to the dry soil weight are added; 0.5-1% ferrous sulfate aqueous solution and 0.5-1% sulfur aqueous suspension are added, mixed evenly, covered with film and stacked for 12-24 hours.

[0016] Preferably, the concentration of the ferrous sulfate aqueous solution is 3-7%wt, and the sulfur aqueous suspension is 45-50%wt sulfur and 1-2.5%wt water glass.

[0017] Preferably, in step S3, the conditioning and fertilization step involves adding 15-30% of fermented and mixed sawdust, leaf powder, and distiller's grains, and mixing them evenly. This continuously provides nutrients for plant growth, with the sawdust, leaf powder, and distiller's grains in a weight ratio of 1:10-15:6-8.

[0018] Preferably, the amount of the curing agent is 6-10% of the relative dry soil weight; the weight ratio of the raw materials of the curing agent, phosphogypsum, slag powder, red mud, and straw is 35-55: 20-28: 25-36: 0.25-0.75, and an appropriate amount of water is added to maintain the weight ratio of water to the prepared neutral cured soil at 0.45-0.65:1.

[0019] Preferably, the straw is 6-12 mm in length.

[0020] Preferably, in step S5, the oxygenation step involves adding 2-4% calcium peroxide granules relative to the dry soil weight; the water retention step involves adding 0.1-0.5% superabsorbent polymer. Before pumping, the mixture is prepared on-site to continuously provide the necessary oxygen and water for plant growth.

[0021] This invention also discloses a recycled low-strength neutral solidified soil prepared by the above preparation method, wherein the components are expressed in parts by mass. 100 portions of silt; 10-20 parts of pulp waste and coffee grounds, wherein the weight ratio of pulp waste to coffee grounds is 0.8-1.2:1; The mixture contains 20-30 parts of stone powder and building powder, wherein the weight ratio of stone powder to building powder is 1.2-2.3:1. 1-2 parts of superphosphate; 1-2 parts of activated attapulgite; 0.5-1 part of ferrous sulfate aqueous solution; 0.5-1 part of sulfur aqueous suspension; 15-30 parts of fermented and mixed sawdust, leaf powder and distiller's grains, wherein the weight ratio of fermented and mixed sawdust, leaf powder and distiller's grains is 1:10-15:6-8; 6-10 parts of curing agent, wherein the weight ratio of the raw materials of the curing agent, phosphogypsum, slag powder, red mud, and straw is 35-55: 20-28: 25-36: 0.25-0.75; and add an appropriate amount of water to maintain the weight ratio of water to the prepared neutral solidified soil at 0.45-0.65:1; 2-4 parts of calcium peroxide granules; 0.1-0.5 parts of superabsorbent polymer. Beneficial effects

[0022] Compared with existing technologies, this invention provides a method for in-situ preparation of recycled low-strength neutral solidified soil based on river and lake silt. The resulting recycled soil is a low-strength, neutral recycled soil from dredged river and lake silt. Paper pulp waste and coffee grounds are used to reduce the water content of the silt. These materials are waste materials, resulting in low cost and resource conservation. Since silty soil contains heavy metals and pathogenic microorganisms, a composite disinfection and sterilization solution of superphosphate, attapulgite, ferrous sulfate aqueous solution, and sulfur suspension is used to effectively remove harmful substances from the silty soil. Furthermore, the materials used are more environmentally friendly. A neutral solidifying agent composed of phosphogypsum, slag powder, and red mud is used. The slag powder and red mud provide aluminum and silicon ions for the solidification of phosphogypsum, improving its strength. Furthermore, the use of industrial solid waste saves costs and resources. Phosphogypsum is acidic (pH 5-6), while slag powder and red mud are alkaline (pH 9-12). By adjusting the proportions, neutral solidification of the sludge is achieved without the need for pH adjusters. After solidification, the solidified soil has low strength, meeting the requirements for both the attachment slope and plant growth, thus improving germination rates and offering good economic and environmental benefits. The prepared recycled soil has a certain strength, is sterilized, nutrient-rich, and has large pores to retain moisture, making it suitable for direct planting. Attached Figure Description

[0023] Figure 1 This is a flowchart of the preparation process of the present invention.

[0024] Figure 2 This is a diagram illustrating the planting effect of an embodiment of the present invention.

[0025] Figure 3 This is a comparative illustration of the planting effect of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0028] Example 1 Preparation of fermentation mixture: 10g sawdust powder, 150g leaf powder, and 80g distiller's grains were mixed for fermentation. The moisture content was 55%, the ambient temperature was around 15℃, and the fermentation time was 30 days. Fermentation component A was obtained.

[0029] Example 2 Preparation of fermentation mixture: 100g sawdust powder, 60g leaf powder, and 80g distiller's grains were mixed and fermented. The moisture content during fermentation was 65%, the ambient temperature was around 25℃, and the fermentation time was 60 days. Fermentation component B was obtained.

[0030] Example 3 Preparation of the fermentation mixture: 50g sawdust powder, 90g leaf powder, and 80g distiller's grains were mixed for fermentation. The moisture content during fermentation was 60%, the ambient temperature was around 20℃, and the fermentation time was 45 days. Fermentation component C was obtained.

[0031] Example 4 The following are the test data for the silt sampled in situ and the silty soil used:

[0032] like Figure 1 As shown, a method for in-situ preparation of recycled low-strength neutral solidified soil based on river and lake silt includes the following steps: S1. First, add river and lake silt to the mixer, then add 10-20% of paper pulp waste and coffee grounds by relative dry weight, and add 20-30% of stone powder and building powder by relative dry weight. Mix at a mixer speed of 50 r / min (the mixer speed can be 50-500 r / min, and 50 r / min is selected in this embodiment) for 5 minutes (the mixing time can be 5-100 minutes, and 5 minutes is selected in this embodiment) to reduce the silt moisture content to below 20%. S2. Add 1-2% of superphosphate and 1-2% of activated attapulgite relative to the dry weight of the soil to the mixer. Mix at 50 r / min for 10 min. While mixing, add 0.5-1% of ferrous sulfate aqueous solution and 0.5-1% of sulfur aqueous suspension relative to the dry weight of the soil. After mixing, cover with a film and pile at room temperature for 12-24 h. S3. Add 15-30% of the fermented mixture of sawdust, leaf powder and distiller's grains by relative dry soil weight to the mixer. Mix at 50 rpm for 15 minutes, then mix at 50 rpm for 5 minutes.

[0033] S4. Add 6-10% of the solidifying agent relative to the dry weight of the soil. Add an appropriate amount of water according to the moisture content of the silt in the mixer to achieve a water-to-soil ratio of 0.45-0.65:1, and adjust the pH to neutral. Mix at 50 rpm for 10 minutes, and let stand for 24-48 hours.

[0034] S5. Before pumping, mix in 2-4% calcium peroxide granules relative to the dry weight of the soil, and continue to add 0.1-0.5% superabsorbent polymer relative to the dry weight of the soil. Mix thoroughly for 5 minutes at a mixer speed of 50 r / min. After pumping, cure at a temperature of 20℃ until the soil solidifies.

[0035] In this invention, the water content of the sludge is reduced by adding pulp waste and coffee grounds, thus drying the sludge; stone powder and building powder are added to sandify the sludge. This drying and sandification process makes the sludge easier to mix.

[0036] The sludge is disinfected by adding superphosphate and activated attapulgite, which exchange and physically adsorb heavy metal ions in the soil; and by adding ferrous sulfate solution and sulfur suspension to eliminate pathogenic microorganisms and sterilize the sludge. Disinfection and sterilization reduce harmful substances in the sludge that affect plant growth.

[0037] By adding fermented sawdust, leaves, and distiller's grains, the organic matter content of the silt is increased, thus improving soil quality. This conditioning and fertilization process ensures the silt contains the necessary environment and nutrients for plant growth.

[0038] By adding phosphogypsum, slag powder, red mud, and straw, the silt gains a certain strength and can be used for spraying and planting soil.

[0039] Adding superabsorbent polymers before construction and pumping provides high water storage capacity and maintains soil moisture; adding calcium peroxide granules before construction and pumping allows them to react slowly with water to provide the oxygen needed for plant growth.

[0040] Example 5 A low-strength neutral-stabilized soil based on in-situ preparation of river and lake silt was prepared using the method of Example 4, wherein the component ratios were as follows: 500g of dried silt and raw soil; Pulp waste, 22.2g; Coffee grounds, 27.8g; Stone powder, 54.55g Building powder, 45.45g; Superphosphate, 5g; Activated attapulgite, 5g; Ferrous sulfate aqueous solution (3-7%wt), 2.5g; Sulfur aqueous suspension (45-50% wt sulfur and 1-2.5% wt water glass), 2.5g; Fermentation component A of Example 1, 75g; 30g of curing agent, including 13.08g of phosphogypsum, 7.48g of slag powder, 9.35g of red mud, 0.093g of straw (6mm in length), and 225g of water; Superabsorbent polymer, 0.5g; Calcium peroxide granules, 10g.

[0041] The prepared stabilized soil was subjected to pH, compressive strength, and workability tests. A planting experiment was conducted by placing 30 *Hedysarum heterotropoides* seeds 0.5 cm below the surface of the stabilized soil in flowerpots and watering with 200 ml of water daily. The experimental data are as follows: pH 7-day compressive strength / kPa Spread / mm Viscosity / mPas 3-day germination rate 7.1 0.26 61 6200 93% Example 6

[0042] A low-strength neutral-stabilized soil based on in-situ preparation of river and lake silt was prepared using the method in Example 4, with the following component proportions: 500g of dried silt and raw soil; Pulp waste, 54.55g; Coffee grounds, 45.45g; Stone powder, 104.55g; Building powder, 45.45g; Superphosphate, 10g; Activated attapulgite, 10g; Ferrous sulfate aqueous solution (3-7%wt), 5g; Sulfur aqueous suspension (45-50%wt sulfur and 1-2.5%wt water glass), 5g; Fermentation component B of Example 2, 150g; 50g of curing agent, including 22.96g of phosphogypsum, 11.69g of slag powder, 15.03g of red mud, 0.31g of straw (12mm in length), and 325g of water; Superabsorbent polymer, 2.5g; Calcium peroxide granules, 20g.

[0043] The prepared solidified soil was subjected to pH, compressive strength, and workability tests. A planting experiment was conducted by placing 30 *Hedysarum heterotropoides* seeds 0.5 cm below the surface of the solidified soil in flowerpots and watering with 200 ml of water daily. The experimental data are as follows: pH 7-day compressive strength / kPa Spread / mm Viscosity / mPas 3-day germination rate 7.3 0.43 73 5500 97% Example 7

[0044] A low-strength neutral-stabilized soil based on in-situ preparation of river and lake silt was prepared using the method of Example 4. The component ratios were as follows: 500g of dried silt and raw soil; Pulp waste, 37.5g; Coffee grounds, 37.5g; Stone powder, 80.36g Building powder, 44.64g; Superphosphate, 7.5g; Activated attapulgite, 7.5g; Ferrous sulfate aqueous solution (3-7%wt), 3.75g; Sulfur aqueous suspension (45-50%wt sulfur and 1-2.5%wt water glass), 3.75g; Fermentation component C of Example 3, 112.5 g; 40g of curing agent, including 18.09g of phosphogypsum, 9.64g of slag powder, 12.06g of red mud, 0.2g of straw (straw length 9mm), and 275g of water; Superabsorbent polymer, 1.5g; Calcium peroxide granules, 15g.

[0045] The prepared solidified soil was subjected to pH, compressive strength, and workability tests. A planting experiment was conducted by placing 30 *Hedysarum heterotropoides* seeds 0.5 cm below the surface of the solidified soil in flowerpots and watering with 200 ml of water daily. The experimental data are as follows: pH 7-day compressive strength / kPa Spread / mm Viscosity / mPas 3-day germination rate 7.1 0.39 68 5900 90% Example 8

[0046] A low-strength neutral-stabilized soil based on in-situ preparation of river and lake silt was prepared using the method of Example 4. The component ratios were as follows: 500g of dried silt and raw soil; Pulp waste, 28g; Coffee grounds, 32g; Stone powder, 78g Building powder, 42g; Superphosphate, 6g; Activated attapulgite, 6g; Ferrous sulfate aqueous solution (3-7%wt), 3g; Sulfur aqueous suspension (45-50%wt sulfur and 1-2.5%wt water glass), 3g; Fermentation component C of Example 3, 90g; 35g of curing agent, including 15.49g of phosphogypsum, 8.52g of slag powder, 10.84g of red mud, 0.13g of straw (7mm in length), and 260g of water; Superabsorbent polymer, 1g; Calcium peroxide granules, 12.5g.

[0047] The prepared solidified soil was subjected to pH, compressive strength, and workability tests. A planting experiment was conducted by placing 30 *Hedysarum heterotropoides* seeds 0.5 cm below the surface of the solidified soil in flowerpots and watering with 200 ml of water daily. The experimental data are as follows: pH 7-day compressive strength / kPa Spread / mm Viscosity / mPas 3-day germination rate 7 0.33 66 6000 90% Example 9

[0048] A low-strength neutral-stabilized soil based on in-situ preparation of river and lake silt was prepared using the method of Example 4. The component ratios were as follows: 500g of dried silt and raw soil; Pulp waste, 46g; Coffee grounds, 44g; Stone powder, 80g Building powder, 50g; Superphosphate, 8g; Activated attapulgite, 8g; Ferrous sulfate aqueous solution (3-7%wt), 2.7g; Sulfur aqueous suspension (45-50%wt sulfur and 1-2.5%wt water glass), 2.7g; Fermentation component C of Example 3, 100g; The curing agent contains 37.5g, including 16.5g phosphogypsum, 9.43g slag powder, 11.39g red mud, 0.15g straw (straw length 8mm), and 300g water. Superabsorbent polymer, 1.25g; Calcium peroxide granules, 12.5g.

[0049] The prepared solidified soil was subjected to pH, compressive strength, and workability tests. A planting experiment was conducted by placing 30 *Hedysarum heterotropoides* seeds 0.5 cm below the surface of the solidified soil in flowerpots and watering with 200 ml of water daily. The experimental data are as follows: pH 7-day compressive strength / kPa Spread / mm Viscosity / mPas 3-day germination rate 7.1 0.34 70 5700 97% Comparative Example 1 Compared to Example 4, the drying and sandification step is missing. A low-strength, neutral-stabilized soil based on in-situ preparation of river and lake silt was prepared using the method of Example 4, with the following component ratios: 500g of dried silt and raw soil; Superphosphate, 7.5g; Activated attapulgite, 7.5g; Ferrous sulfate aqueous solution (3-7%wt), 3.75g; Sulfur aqueous suspension (45-50%wt sulfur and 1-2.5%wt water glass), 3.75g; Fermentation component C, 112.5g; 40g of curing agent, including 18.09g of phosphogypsum, 9.64g of slag powder, 12.06g of red mud, 0.2g of straw (straw length 9mm), and 275g of water; Superabsorbent polymer, 1.5g; Calcium peroxide granules, 15g.

[0050] The prepared solidified soil was subjected to pH, compressive strength, and workability tests. A planting experiment was conducted by placing 20 *Hedysarum heterotropoides* seeds at a depth of 0.5 cm in flowerpots and watering with 200 ml of water daily. The experimental data are as follows: pH 7-day compressive strength / kPa Spread / mm Viscosity / mPas 3-day germination rate 6.8 0.38 44 11000 10% Without undergoing drying and sandification processes, the solidified soil has poor fluidity, does not meet the requirements for hydroseeding, and makes seed germination difficult.

[0051] Comparative Example 2 Compared to Example 4, the difference lies in the curing agent dosage being 15%, and the use of commercially available silicate cement. A low-strength neutral solidified soil based on in-situ preparation of river and lake silt was prepared using the method of Example 4, with the following component ratios: 500g of dried silt and raw soil; Pulp waste, 37.5g; Coffee grounds, 37.5g; Stone powder, 80.36g Building powder, 44.64g; Superphosphate, 7.5g; Activated attapulgite, 7.5g; Ferrous sulfate aqueous solution (3-7%wt), 3.75g; Sulfur aqueous suspension (45-50%wt sulfur and 1-2.5%wt water glass), 3.75g; Fermentation component C, 112.5g; 75g of PO32.5 silicate cement curing agent; Superabsorbent polymer, 1.5g; Calcium peroxide granules, 15g.

[0052] The prepared solidified soil was subjected to pH, compressive strength, and workability tests. A planting experiment was conducted by placing 20 *Hedysarum heterotropoides* seeds at a depth of 0.5 cm in flowerpots and watering with 200 ml of water daily. The experimental data are as follows: pH 7-day compressive strength / kPa Spread / mm Viscosity / mPas 3-day germination rate 10.8 1.5 81 4600 0% The commonly used cement hardener has an excessively high pH and strength, making it unsuitable for plant growth.

[0053] like pH As shown in the figure, A represents the germination and growth status of the bok choy in Example 5 after 3 days, with a germination rate of 93%; B represents the germination and growth status of the bok choy in Example 6 after 3 days, with a germination rate of 97%; C represents the germination and growth status of the bok choy in Example 7 after 3 days, with a germination rate of 90%; D represents the germination and growth status of the bok choy in Example 8 after 3 days, with a germination rate of 90%; and E represents the germination and growth status of the bok choy in Example 9 after 3 days, with a germination rate of 97%. 7-day compressive strength / kPa Spread / mm Viscosity / mPas 3-day germination rate Figure 2 Figure 3 As shown in the figure, F represents the germination and growth status of *Chicken Feather Cabbage* in Comparative Example 1 after 3 days, with a germination rate of 10%. G represents the germination and growth status of *Chicken Feather Cabbage* in Comparative Example 2 after 3 days, with a germination rate of 0%. It can be seen that the pH of the solidified soil is neutral between 6.5 and 7.5, meeting the needs of plant growth. Its low strength, while ensuring the slope does not collapse, is suitable for plant germination. It has good spreadability and viscosity, facilitating hydroseeding. However, excessive spread (less than 50 mm) and excessive viscosity (greater than 7000 mPas) will prevent the fluid soil from being sprayed. The high seed germination rate makes it suitable as planting soil.

[0054] The above are merely preferred embodiments of the present invention. It should be noted that, for those skilled in the art, the specific exemplary technical solutions of the embodiments of the present invention are intended to illustrate and demonstrate, so that those skilled in the art can implement and utilize different embodiments of the present invention without departing from the technical principles of the present invention, and can also make several improvements and modifications.

Claims

1. A method for in-situ preparation of recycled low-strength neutral solidified soil based on river and lake silt, characterized in that, The method includes the following steps: S1, Drying and Sandification; The drying step is: mixing paper pulp waste and coffee grounds into the silt and mixing evenly; The sandification step is: mixing stone powder and building powder into the silt and mixing evenly. S2, sterilization and disinfection; the disinfection step is: adding superphosphate and activated attapulgite clay, mixing evenly; the sterilization step is: adding ferrous sulfate aqueous solution and sulfur aqueous suspension, mixing evenly. S3, for fertilization and conditioning; mix in fermented sawdust, leaf powder and distiller's grains until well combined; S4, neutral curing; add curing agent and mix evenly, the raw materials of the curing agent are phosphogypsum, slag powder, red mud and straw; S5, oxygenation and water retention, yields silt regenerated and solidified soil.

2. The method according to claim 1, characterized in that, In S1, The amount of pulp waste and coffee grounds added is 10-20% of the relative dry weight, and the weight ratio of pulp waste to coffee grounds is 0.8-1.2:1; The amount of stone powder and building powder added is 20-30% of the relative dry soil weight, and the weight ratio of stone powder to building powder is 1.2-2.3:

1.

3. The method according to claim 1, characterized in that, In the S2 mixture, 1-2% of superphosphate and 1-2% of activated attapulgite relative to the dry soil weight are added; 0.5-1% of ferrous sulfate aqueous solution and 0.5-1% of sulfur aqueous suspension relative to the dry soil weight are added, mixed evenly, covered with film and piled for 12-24 hours.

4. The method according to claim 3, characterized in that, The concentration of the ferrous sulfate aqueous solution is 3-7%wt, and the sulfur aqueous suspension is 45-50%wt sulfur and 1-2.5%wt water glass.

5. The method according to claim 1, characterized in that, In step S3, the conditioning and fertilization step is as follows: 15-30% of the relative dry soil weight of fermented and mixed sawdust, leaf powder and distiller's grains are added and mixed evenly; wherein the weight ratio of sawdust, leaf powder and distiller's grains is 1:10-15:6-8.

6. The method according to claim 1, characterized in that, In step S4, the amount of the curing agent is 6-10 parts relative to the dry soil weight, and the pH is adjusted to neutral. The weight ratio of the raw materials of the curing agent, phosphogypsum, slag powder, red mud, and straw, is 35-55: 20-28: 25-36: 0.25-0.75, and an appropriate amount of water is added to maintain the weight ratio of water to the neutral cured soil after preparation at 0.45-0.65:

1.

7. The method according to claim 1, characterized in that, In S5, The oxygenation step is as follows: 2-4% of calcium peroxide particles relative to the dry soil weight are added. The water-retaining step is as follows: 0.1-0.5% of a superabsorbent polymer relative to the dry soil weight is added.

8. A type of recycled low-strength neutral solidified soil, characterized in that, Each component is calculated in parts by mass. 100 portions of silt; 10-20 parts of pulp waste and coffee grounds, wherein the weight ratio of pulp waste to coffee grounds is 0.8-1.2:1; The mixture contains 20-30 parts of stone powder and building powder, wherein the weight ratio of stone powder to building powder is 1.2-2.3:

1. 1-2 parts of superphosphate; 1-2 parts of activated attapulgite; 0.5-1 part of ferrous sulfate aqueous solution; 0.5-1 part of sulfur aqueous suspension; 15-30 parts of fermented and mixed sawdust, leaf powder and distiller's grains, wherein the weight ratio of fermented and mixed sawdust, leaf powder and distiller's grains is 1:10-15:6-8; The curing agent consists of 6-10 parts, wherein the weight ratio of the raw materials for the curing agent—phosphogypsum, slag powder, red mud, and straw—is 35-55: 20-28: 25-36: 0.25-0.

75. 2-4 parts of calcium peroxide granules; 0.1-0.5 parts of superabsorbent polymer.

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