A method for preparing bubble mixed light soil raw material by crushing and screening dredged soil in situ

Abstract

The present application belongs to the technical field of dredged sludge resource processing and light building material preparation, and particularly relates to a method for preparing bubble mixed light soil raw material by in-situ crushing and screening of dredged soil, which adopts an amphibious mobile integrated in-situ treatment unit and a dredging ship, and the amphibious mobile integrated in-situ treatment unit comprises a flexible crushing unit, a three-stage gradient screening unit, an in-situ conditioning mixing unit, an online moisture content monitoring and regulating unit, and a coarse residue pressure filtration solidification unit, and specifically comprises the following steps: S1: continuously taking soil in-situ, excavating underwater dredged soil layer in-situ for a river channel or a port area, and directly conveying the excavated dredged soil to the amphibious mobile integrated in-situ treatment unit on the shore through a closed sludge conveying pipeline; the present application can realize integrated in-situ continuous operation of dredging, crushing, gradient screening, sludge modification and conditioning, and online moisture content regulation, and in-situ output of special raw material for bubble mixed light soil which is stable in performance and can be directly pumped and mixed.

Description

Technical Field

[0001] This invention belongs to the field of dredged sludge resource utilization and lightweight building material preparation technology, specifically involving a method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil. Background Technology

[0002] Waterways, ports, and lakes generate tens of millions of cubic meters of dredged soil every year. Traditional disposal methods are divided into three categories: dumping at sea, stockpiling on land, and off-site recycling. Dumping at sea damages the aquatic ecosystem; stockpiling on land occupies a large amount of arable land, and leachate from the silt can easily pollute the soil and groundwater; off-site recycling requires dredging vessels to excavate silt, barges to transfer it, and dewatering, drying, crushing, and screening pretreatment at the stockpile. These multiple transfer processes generate dust and secondary pollution from mud leakage, resulting in high overall disposal costs and long construction periods.

[0003] Foamed lightweight soil (foamed lightweight soil) is widely used in soft soil foundation embankments, bridge abutment backfilling, and foundation pit load reduction backfilling projects due to its advantages of light weight, good fluidity, self-compacting, and convenient construction. The existing preparation process requires that the raw material silt have uniform particle size and be free of large-diameter shells, gravel, and lumpy clay. Otherwise, the air bubbles are easily punctured by sharp impurities, resulting in voids, strength dispersion, and excessive bulk density in the lightweight soil.

[0004] Patent search revealed that the bubble-mixed lightweight soil with application number CN03113371.1 is prepared by using dredged soil and silt as raw materials, and clearly requires crushing, screening to remove impurities and control particle size of the soil material. However, all pretreatment processes are completed off-site at the onshore storage yard. The silt is dredged, transported, stored, dried, and then crushed and screened. The multi-stage transportation increases energy consumption and pollution. The drying cycle of heavy dredged soil is as long as 15 to 30 days, making construction impossible during the flood season. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil. This method can realize the integrated in-situ continuous operation of dredging, crushing, gradient screening, sludge modification and conditioning, and online moisture content control. It eliminates the need for sludge transfer and storage for drying, and produces a special raw material for bubble-mixed lightweight soil with stable performance that can be directly pumped and mixed.

[0006] The specific technical solution adopted by this invention is as follows: A method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil, employing an amphibious mobile integrated in-situ processing unit and a dredging vessel, wherein the amphibious mobile integrated in-situ processing unit includes a flexible crushing unit, a three-stage gradient screening unit, an in-situ conditioning and mixing unit, an online moisture content monitoring and control unit, and a coarse slag pressure filtration and solidification unit, specifically including the following steps: S1: Continuous in-situ soil extraction during dredging, excavating underwater soil layers in rivers and port areas in situ, and directly transporting the excavated dredged soil to the shore-side amphibious mobile integrated in-situ treatment unit through a closed mud conveying pipeline. Dredging and continuous in-situ soil extraction are carried out using cutter suction or bucket wheel dredging vessels.

[0007] S2: Flexible graded crushing, using differentiated crushing of clumps in dredged soil; Specifically, it includes the following: The flexible crushing unit includes a double-helix crushing roller and a hydraulic impact nozzle, wherein the double-helix crushing roller is covered with a rubber layer; S21: Dredged soil is first fed into the flexible crushing unit. The shells, gravel, and hard soil blocks contained in the dredged soil are then subjected to flexible extrusion crushing after passing through the double spiral crushing rollers, forming debris with a particle size ≤5mm. S22: High-viscosity clay clumps are broken up by high-pressure water jet through a hydraulic impact nozzle, without the need for pre-drying and dehydration, forming a mixture. The water pressure of the hydraulic impact nozzle is 1.8 to 2.5 MPa.

[0008] S23: The mixture then enters the three-stage gradient screening unit.

[0009] S3: Three-stage gradient in-situ screening is used to separate and divert materials to obtain fine silt base material; Furthermore, the three-stage gradient screening unit is configured with a coarse screen layer, a medium screen layer, and a fine screen layer from top to bottom; Specifically, it includes the following: S31: The coarse screen layer is used to intercept large stones, intact shells, and plant roots and stems. The intercepted coarse slag is directly transported to the coarse slag pressure filter solidification unit, and a small amount of solidifying agent is added to compact it on-site into roadbed crushed stone filler, which does not need to be transported and disposed of. S32: The sieve holes of the middle sieve layer are used to intercept sharp-edged gravel and thick shell fragments after crushing, and return them to the flexible crushing unit for secondary crushing until the particle size is less than 5mm. S33: The sieve holes of the fine sieve layer are used to screen out fine silt base material that meets the particle size requirements of lightweight air-bubbly soil, which is directly introduced into the in-situ conditioning and mixing unit; a small amount of coarse sand on the sieve is collected separately for backfilling riverbed shoals.

[0010] The coarse sieve layer has a sieve aperture of 10 mm, the medium sieve layer has a sieve aperture of 5 mm, and the fine sieve layer has a sieve aperture of 2 mm.

[0011] S4: In-situ synchronous conditioning and modification of fine silt base material to meet the requirements of bubble-mixed lightweight soil slurry preparation and obtain lightweight soil bricks. Specifically, it includes the following: S41: The fine silt base material is fed into the in-situ conditioning and mixing unit, and the composite modifier is added online; The composite modifier comprises, by weight, 12-18 parts fly ash, 3-5 parts bentonite, 0.2-0.5 parts lignin sulfonate dispersant, and 2-4 parts silica fume.

[0012] The composite modifier is continuously added in small amounts with the fine silt slurry, and the amount added is 4% to 7% of the dry weight of the fine silt.

[0013] S42: The in-situ conditioning and mixing unit mixes the fine silt base material with the composite modifier at a stirring speed of 60-80 r / min for 3-5 min to complete the modification and obtain lightweight soil material.

[0014] S5: Adjust the moisture content of lightweight clay bricks to obtain standardized bubble-mixed lightweight clay raw materials.

[0015] Specifically, it includes the following: The moisture content of lightweight clay bricks is detected in real time by an infrared moisture sensor and adjusted according to the standard moisture content threshold of bubble-mixed lightweight clay. If the slurry moisture content is higher than 50%, the vacuum microfiltration dewatering module inside the unit is turned on to extract the excess free water. The filtered water is returned to the front end of the dredging and soil extraction for recycling. After the free water is discharged, the slurry is evenly mixed with the raw material mixing equipment to obtain standardized bubble-mixed lightweight soil raw material.

[0016] The technical effects achieved by this invention are as follows: The present invention discloses a method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil. This method adopts in-situ continuous operation, and lightweight soil raw material is produced simultaneously with dredging. It can be used for foaming construction on the same day as dredging, eliminating the need for land acquisition for stockpiling, short-distance transportation vehicles, and drying equipment investment, thus reducing the overall disposal cost. In addition, the mobile unit can be used to operate in narrow banks, shallow waters, and areas without stockpiling, and is equipped with a vacuum microfiltration dewatering module, allowing for continuous construction in rainy weather and low winter temperatures. Attached Figure Description

[0017] Figure 1 This is a flowchart of the present invention; Detailed Implementation

[0018] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0019] like Figure 1As shown, a method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil is adopted. The method uses an amphibious mobile integrated in-situ processing unit and a dredging dredger. The amphibious mobile integrated in-situ processing unit includes a flexible crushing unit, a three-stage gradient screening unit, an in-situ conditioning and mixing unit, an online moisture content monitoring and control unit, and a coarse slag pressure filtration and solidification unit. Furthermore, the amphibious mobile integrated in-situ treatment unit can also be equipped with a vehicle-mounted chassis and a floating buoyancy module. It can travel on wheels in hardened areas on the shore and switch to floating buoyancy support in shallow water tidal flats and riverbanks, making it suitable for various complex construction sites such as those without storage yards, narrow riverbanks, and temporary dredging.

[0020] Specifically, the following steps are included: S1: Continuous in-situ soil extraction during dredging. The dredged soil is excavated in-situ in the river channel and port area. The excavated dredged soil is directly transported to the shore-side amphibious mobile integrated in-situ treatment unit through a closed mud conveying pipeline, eliminating leakage and pollution along the way. Dredging and continuous in-situ soil extraction are carried out using cutter suction or bucket wheel dredging vessels.

[0021] Traditional methods of transporting sludge by barges and trucks are prone to mud leakage, dust pollution along the way, and leachate from the storage site, which can pollute the soil and water. This invention features a fully enclosed pipeline transportation system and in-situ closed-loop treatment. Coarse sludge is solidified and utilized on-site, and wastewater is internally recycled. There is no external transportation of sludge or discharge of sewage. It is suitable for dredging projects in ecologically sensitive lakes and drinking water source rivers, and meets stringent environmental protection control requirements.

[0022] S2: Flexible graded crushing, using differentiated crushing of clumps in dredged soil; Specifically, it includes the following: The flexible crushing unit includes a twin-helix crushing roller and a hydraulic impact nozzle, with the twin-helix crushing roller covered with a rubber layer; S21: Dredged soil is first fed into the flexible crushing unit. The shells, gravel, and hard soil blocks contained in the dredged soil are then subjected to flexible extrusion crushing after passing through the double spiral crushing rollers, forming debris with a particle size ≤5mm. S22: High-viscosity clay clumps are broken up by high-pressure water jet through a hydraulic impact nozzle, without the need for pre-drying and dehydration, forming a mixture. The water pressure of the hydraulic impact nozzle is 1.8 to 2.5 MPa, which only disintegrates clay clumps and does not cause excessive scouring that leads to the loss of fine silt particles.

[0023] S23: The mixture then enters the three-stage gradient screening unit.

[0024] S3: Three-stage gradient in-situ screening is used to separate and divert materials to obtain fine silt base material; Furthermore, the three-stage gradient screening unit is configured with a coarse screen layer, a medium screen layer, and a fine screen layer from top to bottom; Specifically, it includes the following: S31: The coarse screen layer is used to intercept large stones, intact shells, and plant roots and stems. The intercepted coarse slag is directly transported to the coarse slag pressure filter solidification unit, and a small amount of solidifying agent is added to compact it on-site into roadbed crushed stone filler, which does not need to be transported and disposed of. S32: The sieve holes of the middle sieve layer are used to intercept sharp-edged gravel and thick shell fragments after crushing, and return them to the flexible crushing unit for secondary crushing until the particle size is less than 5mm. S33: The sieve holes of the fine sieve layer are used to screen out fine silt base material that meets the particle size requirements of lightweight air-bubbly soil, which is directly introduced into the in-situ conditioning and mixing unit; a small amount of coarse sand on the sieve is collected separately for backfilling riverbed shoals.

[0025] The coarse sieve layer has a sieve aperture of 10mm, the medium sieve layer has a sieve aperture of 5mm, and the fine sieve layer has a sieve aperture of 2mm.

[0026] Modification effect: Reduces the viscosity of dredged soil slurry, weakens the ability of clay particles to adsorb air bubbles, significantly reduces the probability of air bubble breakage during the slurry preparation process, and optimizes the particle size distribution of slurry, thereby improving the overall uniformity and later compressive strength of the air bubble lightweight soil.

[0027] S4: In-situ synchronous conditioning and modification of fine silt base material to meet the requirements of bubble-mixed lightweight soil slurry preparation and obtain lightweight soil bricks. Specifically, it includes the following: S41: The fine silt base material is fed into the in-situ conditioning and mixing unit, and the composite modifier is added online; The composite modifier comprises, by weight, 12-18 parts fly ash, 3-5 parts bentonite, 0.2-0.5 parts lignin sulfonate dispersant, and 2-4 parts silica fume.

[0028] The composite modifier is continuously added in small amounts with the fine silt slurry, at a dosage of 4% to 7% of the dry silt mass, without changing the core properties of the lightweight and low-density aerated soil.

[0029] S42: The in-situ conditioning and mixing unit mixes the fine silt base material with the composite modifier at a stirring speed of 60-80 r / min for 3-5 min to complete the modification and obtain lightweight soil material.

[0030] The in-situ conditioning and mixing unit is equipped with an insulation interlayer. Hot water is introduced for insulation during low-temperature winter construction to ensure the fluidity of the slurry and prevent the low-temperature clay from flocculating and agglomerating, which would affect the foaming effect.

[0031] S5: Adjust the moisture content of lightweight clay bricks to obtain standardized bubble-mixed lightweight clay raw materials.

[0032] Specifically, it includes the following: The moisture content of lightweight clay bricks is detected in real time by an infrared moisture sensor and adjusted according to the standard moisture content threshold of bubble-mixed lightweight clay. If the slurry moisture content is higher than 50%, the vacuum microfiltration dewatering module inside the unit is turned on to extract the excess free water. The filtered water is returned to the front end of the dredging and soil extraction for recycling. After the free water is discharged, the slurry is evenly mixed with the raw material mixing equipment to obtain standardized bubble-mixed lightweight soil raw material.

[0033] S6: Closed-loop disposal of waste materials, zero waste soil in situ; The coarse slag produced by screening is solidified by pressure filtration and used on-site. The dewatered filtrate is recycled and reused. A small amount of screened coarse sand is backfilled into the river channel in situ. The entire process involves no off-site transportation of dredged soil and no off-site transportation of silt and soil, realizing a closed-loop in-situ treatment of dredging and raw material preparation.

[0034] Traditional processes screen coarse slag and large pieces of shells and gravel, which are mostly transported off-site as solid waste and landfilled, occupying landfill capacity. This invention uses coarse slag for in-situ pressure filtration and solidification to be used as roadbed filler, fine silt to prepare lightweight backfill material, and coarse sand to backfill river channels. All dredged excavated soil is utilized on-site, solving the problem of dredging waste disposal.

[0035] Furthermore, this invention makes a comparison between this solution and existing technologies: 1. Application number: CN 03113371.1 discloses the preparation of bubble-mixed lightweight soil using dredged soil and silt as raw materials. It is clear that the soil needs to be crushed, screened, and impurities removed to control particle size. However, all pretreatment processes are completed off-site in the onshore storage yard. The silt is dredged, transported, stored, dried, and then crushed and screened. The multi-stage transportation increases energy consumption and pollution. The drying cycle of heavy dredged soil is as long as 15 to 30 days, making construction impossible during the flood season. 2. Application No. CN215855723U discloses a mobile in-situ crushing and screening device for dredged sediment, which can separate coarse sludge and fine sludge on the dredging site and achieve in-situ graded purification. However, this device only separates sludge impurities and does not have a matching modification and conditioning process. The moisture content and clay content of the fine sludge after screening fluctuate greatly. It is not specifically adapted to the requirements for the preparation of foamed lightweight soil. The screened sludge can only be transported out in general for resource utilization and cannot be directly used as a special raw material for foamed lightweight soil. 3. Application number: CN109853310A, discloses a construction method for composite solidified lightweight soil and roadbed layered filling of dredged sludge and industrial waste residue. It uses dredged sludge and industrial waste residue to prepare foamed lightweight soil. The pretreatment process relies entirely on off-site crushing and screening in the factory yard. It depends on large fixed crushing and screening equipment, which cannot be adapted to the scenarios of narrow river channels, no yard on the bank, and temporary dredging projects.

[0036] The difference between this and the previous solution is: Integrated in-situ, end-to-end coupled innovation: In contrast to the off-site crushing and screening modes in comparison documents 1 and 3, this invention integrates dredging and soil extraction, flexible crushing, three-stage gradient screening, sludge conditioning, and online moisture content control into a mobile unit, which can continuously and synchronously complete all pretreatment processes on the dredging site, completely eliminating the need for sludge transfer, drying in the stockyard, and secondary handling. Flexible crushing combined with three-stage gradient closed-loop screening: Comparative document 2 only involves simple in-situ screening without differentiated crushing and material recirculation secondary crushing mechanisms; this invention adopts flexible anti-edge crushing, combined with three-layer gradient screening, to solidify and utilize ultra-large coarse slag in situ, recirculate and re-crush medium and coarse particles, and use fine slurry as a lightweight soil raw material, thereby achieving closed-loop treatment of material separation and diversion. In-situ matching special modification and conditioning process: Existing in-situ screening devices only separate impurities and do not have a modification step suitable for bubble-filled lightweight soil; this invention adds a composite dispersant modifier in-situ after screening to specifically reduce the viscosity of slurry, thus solving the industry pain point of sharp impurities and high-viscosity slurry puncturing bubbles from the source. Online closed-loop adaptive moisture content control: Existing off-site processes rely on long-term sun drying to regulate moisture content, while in-situ screening equipment lacks dehydration and water adjustment functions. This invention is equipped with a real-time moisture content detection combined with a dual-control module for vacuum microfiltration dehydration / in-situ water replenishment, allowing for the recycling of filtered water. It is not affected by rainy weather and produces stable, compliant foaming raw materials around the clock. Dual-mode mobile generator unit adapts to complex operating conditions: Existing in-situ screening equipment is mostly single vehicle-mounted, which cannot be used in shallow riverbeds. This invention can be used on both land and shallow water tidal flats, and is suitable for small-scale dredging projects in inland rivers and lakes without storage yards.

[0037] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil, characterized in that: The method employs an amphibious mobile integrated in-situ treatment unit and a dredging vessel. The amphibious mobile integrated in-situ treatment unit includes a flexible crushing unit, a three-stage gradient screening unit, an in-situ conditioning and mixing unit, an online moisture content monitoring and control unit, and a coarse slag pressure filtration and solidification unit. Specifically, it includes the following steps: S1: Continuous in-situ soil extraction during dredging, excavating underwater soil layers in rivers and port areas in situ, and directly transporting the excavated dredged soil to the shore-side amphibious mobile integrated in-situ treatment unit through a closed mud conveying pipeline. S2: Flexible graded crushing, using differentiated crushing of clumps in dredged soil; S3: Three-stage gradient in-situ screening is used to separate and divert materials to obtain fine silt base material; Furthermore, the three-stage gradient screening unit is configured with a coarse screen layer, a medium screen layer, and a fine screen layer from top to bottom; S4: In-situ synchronous conditioning and modification of fine silt base material to meet the requirements of bubble-mixed lightweight soil slurry preparation and obtain lightweight soil bricks. S5: Adjust the moisture content of lightweight clay bricks to obtain standardized bubble-mixed lightweight clay raw materials.

2. The method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil according to claim 1, characterized in that: In S1, in-situ continuous soil extraction is carried out using a cutter suction dredger or a bucket wheel dredger.

3. The method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil according to claim 1, characterized in that: Specifically, S2 includes the following: The flexible crushing unit includes a double-helix crushing roller and a hydraulic impact nozzle, wherein the double-helix crushing roller is covered with a rubber layer; S21: Dredged soil is first fed into the flexible crushing unit. The shells, gravel, and hard soil blocks contained in the dredged soil are then subjected to flexible extrusion crushing after passing through the double spiral crushing rollers, forming debris with a particle size ≤5mm. S22: High-viscosity clay clumps are broken up by high-pressure water jet through a hydraulic impact nozzle, without the need for pre-drying and dehydration, forming a mixture. S23: The mixture then enters the three-stage gradient screening unit.

4. The method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil according to claim 3, characterized in that: The water pressure of the hydraulic impact nozzle is 1.8 to 2.5 MPa.

5. The method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil according to claim 1, characterized in that: Specifically, S3 includes the following: S31: The coarse screen layer is used to intercept large stones, intact shells, and plant roots and stems. The intercepted coarse slag is directly transported to the coarse slag pressure filter solidification unit, and a small amount of solidifying agent is added to compact it on-site into roadbed crushed stone filler, which does not need to be transported and disposed of. S32: The sieve holes of the middle sieve layer are used to intercept sharp-edged gravel and thick shell fragments after crushing, and return them to the flexible crushing unit for secondary crushing until the particle size is less than 5mm. S33: The sieve holes of the fine sieve layer are used to screen out fine silt base material that meets the particle size requirements of lightweight air-bubbly soil, which is directly introduced into the in-situ conditioning and mixing unit; a small amount of coarse sand on the sieve is collected separately for backfilling riverbed shoals.

6. The method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil according to claim 5, characterized in that: The coarse sieve layer has a sieve aperture of 10 mm, the medium sieve layer has a sieve aperture of 5 mm, and the fine sieve layer has a sieve aperture of 2 mm.

7. The method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil according to claim 1, characterized in that: Specifically, S4 includes the following: S41: The fine silt base material is fed into the in-situ conditioning and mixing unit, and the composite modifier is added online; S42: The in-situ conditioning and mixing unit mixes the fine silt base material with the composite modifier at a stirring speed of 60-80 r / min for 3-5 min to complete the modification and obtain lightweight soil material.

8. The method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil according to claim 7, characterized in that: In S41, the composite modifier comprises, by weight, 12-18 parts fly ash, 3-5 parts bentonite, 0.2-0.5 parts lignin sulfonate dispersant, and 2-4 parts silica fume.

9. The method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil according to claim 8, characterized in that: The composite modifier is continuously added in small amounts with the fine silt slurry, and the amount added is 4% to 7% of the dry weight of the fine silt.

10. The method for preparing bubble-mixed lightweight soil raw material by in-situ crushing and screening of dredged soil according to claim 1, characterized in that: Specifically, S5 includes the following: The moisture content of lightweight clay bricks is detected in real time by an infrared moisture sensor and adjusted according to the standard moisture content threshold of bubble-mixed lightweight clay. If the slurry moisture content is higher than 78%, the vacuum microfiltration dewatering module in the unit will be turned on to extract excess free water. The filtered water will be returned to the front end of the dredging and soil extraction for recycling, and there will be no wastewater discharge. If the slurry moisture content is less than 65%, the system automatically extracts fresh water from the riverbed and adds it to the mixing unit to uniformly adjust the slurry and obtain standardized bubble-mixed lightweight soil raw materials.

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