Construction method for blow-filling superfine-grained soil foundation by synergistically utilizing and treating multi-element solid waste

Abstract

The invention belongs to the technical field of foundation construction, and particularly relates to a construction method for hydraulic reclamation of a superfine-grained soil foundation by synergistically utilizing and treating multi-element solid waste, which comprises the following steps: in an early-stage preparation stage, accurately preparing materials, mixing, adding and stirring all the materials to form a precipitation mixture, paving a foundation bottom layer on the precipitation mixture, and arranging a PVC precipitation well wrapping anti-blocking material at the same time; a water suction pump is installed in the dewatering well and used for draining water from the foundation; all the materials are mixed and added into gypsum slurry to prepare a softer first-stage consolidation material, all the materials are mixed and added into gypsum slurry to prepare a harder second-stage consolidation material, the first-stage consolidation material is laid on a foundation in a layered mode and maintained for 3 days, then the second-stage consolidation material is laid on a first-stage consolidation layer, and consolidation is completed when the pore water pressure dissipation rate is larger than or equal to 85% through maintenance; the method is high in precipitation efficiency, good in solidification effect, high in solid waste utilization rate and low in cost.

Description

Technical Field

[0001] This invention belongs to the field of basic construction technology, specifically relating to a method for constructing a hydraulically filled ultrafine-grained soil foundation by co-utilizing multiple solid wastes. Background Technology

[0002] Hydraulic fill ultrafine-grained soil foundations (particle size mostly less than 0.005mm) are widely used in port terminals, land reclamation, and other projects. These foundations are characterized by high water content (often exceeding the liquid limit by 2-3 times, generally reaching 50%-80%), large porosity (usually >1.5), and extremely poor permeability (permeability coefficient mostly between 10⁻⁻⁶). 8 -10⁻ 6 The characteristic of (cm / s) leads to the following problems: I. Low Dewatering Efficiency. Traditional dewatering methods, such as lightweight wellpoint dewatering and pipe well dewatering, are prone to filter pipe blockage due to the fine particles and narrow pores of the ultrafine-grained soil used for filling. The dewatering rate is only 0.1-0.3 m / d, and the dewatering depth is limited (usually ≤3m), making it difficult to meet the requirements of subsequent construction for the foundation moisture content (which needs to be reduced to 30%-40%). Some projects use vacuum preloading-assisted dewatering, but this requires laying a large number of drainage boards and sealing membranes, resulting in high costs (over 50 yuan per square meter), and the vacuum level is easily lost due to membrane damage, leading to unstable dewatering effects.

[0003] Second, the consolidation effect is poor and the cycle is long. The interparticle bonding force of ultrafine soil foundations is weak. Traditional consolidation methods (such as cement mixing piles and crushed stone piles) require a large amount of high-quality building materials such as cement and crushed stone, which is not only costly, but also has problems such as "uneven bonding" and "delayed consolidation". For example, after cement mixing pile treatment, the foundation consolidation cycle often takes 6-12 months, and cracks are prone to occur in the later stage due to cement hydration shrinkage. At the same time, the annual discharge of industrial solid wastes such as red mud, fly ash, desulfurized gypsum, and slag exceeds 1 billion tons. Long-term stockpiling not only occupies land resources (about 1.5 acres of land are needed for every 10,000 tons of solid waste), but may also cause environmental problems such as heavy metal leakage and dust pollution. Although there are attempts to use single solid wastes for foundation treatment in existing technologies, the synergistic effect of multiple solid wastes has not been fully utilized, and it is impossible to solve the problems of precipitation and consolidation at the same time.

[0004] In summary, there is an urgent need for a construction method that can efficiently achieve dewatering and rapid consolidation of ultrafine-grained soil foundations through hydraulic filling, and can also dispose of diverse industrial solid wastes, so as to balance engineering benefits, economic benefits and environmental benefits. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of low precipitation efficiency, long consolidation period and low solid waste utilization rate of traditional methods, and to achieve the dual goals of rapid treatment of ultrafine soil foundation and resource utilization of industrial solid waste.

[0006] The technical solution adopted by the present invention to solve the aforementioned problem is as follows: A method for co-utilizing multiple solid wastes to treat dredged ultrafine soil foundations includes the following steps: The first step is the preliminary preparation stage. Step 1.1, Site Investigation: A geological drilling rig was used to drill holes in a 5m×5m grid, penetrating the fill layer to the underlying stable layer. A soil sample was taken every 1m to determine its moisture content, void ratio, and permeability coefficient. At the same time, a static cone penetrometer was used to determine the bearing capacity of the foundation and to divide the foundation into high moisture content zone, medium moisture content zone, and low moisture content zone. Step 1.2, Solid Waste Pretreatment: Red mud: It is dried to a moisture content of 10%-15% using a drum dryer, and then crushed to a particle size of ≤2mm using an impact crusher to remove large impurities; Fly ash: Pass through an 80-mesh vibrating screen to remove impurities and ensure that the SiO2+Al2O3 content is ≥70%; Desulfurized gypsum: crushed to a particle size ≤3mm by a jaw crusher, then mixed with water at a mass ratio of 1:2 to form a gypsum slurry for later use; Slag: Grind using a ball mill to a specific surface area of ​​350m²-400m² / kg, ensuring an activity index ≥75%; The second step, the solid waste-assisted precipitation stage, targets areas with high and medium moisture content: Step 2.1, Preparation of precipitation materials: Mix red mud 25%-30%, fly ash 35%-40%, slag 20%-25%, and desulfurized gypsum 5%-10% by mass, add water accounting for 8%-12% of the total mass of the mixed materials, and mix with a forced mixer to prepare precipitation mixture; Step 2.2, Construction of the dewatering structure: In areas with high water content, dewatering wells are arranged in a quincunx pattern with a well spacing of 2m×2m and a well depth of 1.2 times the thickness of the backfill layer; the dewatering wells use Φ150mm PVC pipes with holes drilled in the pipe walls, and are wrapped with two layers of geotextile and one layer of wire mesh to prevent the filter holes from clogging. Fill the dewatering mixture into the dewatering well, with the filling height level with the well opening. At the same time, install a water pump at the well opening and lay a 5cm-8cm thick dewatering mixture cushion layer within a 2m radius around the well. Step 2.3, Precipitation Process Control: Start the water pumps, initially controlling the pumping rate at 2m³-3m³ / h, and monitor the precipitation depth and sediment content of the pumped water every 2 hours; when the precipitation depth reaches 2m, gradually increase the pumping rate to 4m³-5m³ / h, and the sediment content must be ≤0.5%; when the foundation moisture content drops to 35%-40%, stop the precipitation. The third step is the stage of graded consolidation of multi-component solid waste. Step 3.1, First-stage consolidation: Consolidation material ratio: by mass ratio, red mud 20%-25%, slag 30%-35%, fly ash 25%-30%, desulfurized gypsum 10%-15%, add gypsum slurry accounting for 15%-20% of the total mass of materials, stir for 4min-6min to make primary consolidation material, the slump of primary consolidation material is 120mm-150mm; Construction process: The first-level consolidation material is laid in layers using a paver, with each layer being 10cm-12cm thick. After laying, it is compacted 2-3 times with a vibratory roller. The compaction degree after rolling is ≥93%. Three sets of samples are taken for testing every 1000㎡ using the ring cutter method. Areas that fail to meet the requirements are compacted once. Step-by-step 3.2, secondary consolidation: Consolidation material ratio: by mass ratio, red mud 15%-20%, slag 20%-25%, fly ash 35%-40%, desulfurized gypsum 15%-20%, add gypsum slurry accounting for 12%-15% of the total mass of materials, stir for 3 min-5 min to prepare secondary consolidation material; the slump of the secondary consolidation material is 100mm-120mm; Construction process: After curing the primary consolidation layer for 3 days, lay the secondary consolidation material, using the same paving and compaction process as the primary consolidation layer, with a compaction degree ≥92%. After compaction, cover with two layers of geotextile and one layer of plastic film for moisture retention and curing. The curing temperature is controlled at 20℃-25℃, and the curing time is 7-10 days. During this period, monitor the pore water pressure every two days. When the pore water pressure dissipation rate is ≥85%, consolidation is complete.

[0007] Compared with the prior art, the present invention employing the above structure has the following advantages: 1. High precipitation efficiency: Through the coordinated design of "fly ash diversion channel and red mud anti-clogging", the precipitation rate reaches 0.8-1.2m / d, which is 2-4 times higher than the traditional method, and the precipitation depth can reach 4-6m, which meets the construction moisture content requirements; 2. Excellent consolidation effect: The graded consolidation material, through the synergistic effect of chemical cement (ettringite, CSH gel) and physical filler (red mud, slag), increases the bearing capacity of the foundation by 2-3 times after consolidation (from 50-80kPa to 150-200kPa), and shortens the consolidation period to 15-20 days, which is significantly reduced compared to traditional methods (6-12 months). 3. High solid waste utilization rate: The amount of solid waste in a single project accounts for more than 90% of the total mass of the treated materials. Every 10,000 square meters of site can dispose of 800-1200 tons of solid waste such as red mud, fly ash, desulfurization gypsum, and slag, reducing solid waste storage pollution. 4. Low cost: The cost of solid waste materials is only 1 / 3 to 1 / 2 of that of cement, and there is no need for a large number of drainage boards and sealing membranes. The overall construction cost is reduced by 30% to 40% compared with the vacuum preloading method. Detailed Implementation

[0008] The present invention will be further described below with reference to embodiments, which are intended only to provide a better understanding of the invention. Therefore, the examples given do not limit the scope of protection of the present invention.

[0009] The invention provides a method for the co-utilization of multiple solid wastes in the construction of dredged ultrafine-grained soil foundations. The innovative concept is to use red mud, fly ash, desulfurized gypsum, and slag as core materials, and through optimized material ratios and construction processes, simultaneously achieve foundation dewatering and foundation consolidation. Specifically, it includes the following steps: The first step is the preliminary preparation stage. Step 1.1, Site Investigation: Using an XY-150 geological drilling rig, boreholes are drilled in a 5m×5m grid, penetrating the fill layer to the underlying stable layer; optionally, the borehole depth is ≥2m; a soil sample is taken every 1m to determine the moisture content, void ratio, and permeability coefficient; at the same time, a static cone penetrometer is used to determine the bearing capacity of the foundation, and the area is divided into high moisture content zone (moisture content > 60%), medium moisture content zone (moisture content 40%-60%), and low moisture content zone (moisture content < 40%).

[0010] Step 1.2, Solid Waste Pretreatment: Red mud: It is dried to a moisture content of 10%-15% using an HG-800 type drum dryer, and then crushed to a particle size of ≤2mm using an HC-600 type impact crusher to remove large impurities (such as sodium aluminate crystals).

[0011] Fly ash: Pass through an 80-mesh vibrating screen (screen aperture 0.18mm) to remove impurities such as carbon particles and stones, ensuring that the SiO2+Al2O3 content is ≥70%.

[0012] Desulfurized gypsum: It is crushed to a particle size of ≤3mm by a PE-200×300 jaw crusher, and then mixed with water at a mass ratio of 1:2 to make gypsum slurry (activator) for later use.

[0013] Slag: Grind it to a specific surface area of ​​350m²-400m² / kg using an MQW-1200 ball mill to ensure an activity index (7d) ≥75%.

[0014] The second step is the solid waste co-precipitation stage (for areas with high and medium moisture content). Step 2.1, Preparation of Precipitation Material: Mix 25%-30% red mud, 35%-40% fly ash, 20%-25% slag, and 5%-10% desulfurized gypsum by mass ratio, add water accounting for 8%-12% of the total mass of the mixture, and stir for 3-5 minutes using a JS500 forced mixer to prepare precipitation mixture; the moisture content of precipitation mixture is 18%-22%, reaching the state where it can be formed into a ball by hand but crumbles when dropped; among them, the spherical particles of fly ash (particle size 0.5-30μm) form guiding channels, the ultrafine particles of red mud (0.001-0.01mm) fill the pores and prevent the channels from being blocked, and the slag and desulfurized gypsum react initially to form micro-cementitious bodies, improving the structural stability of the mixture.

[0015] Step 2.2, Construction of the dewatering structure: In areas with high moisture content, dewatering wells are arranged in a quincunx pattern with a well spacing of 2m x 2m and a well depth of 1.2 times the thickness of the backfill layer (e.g., if the backfill layer is 5m thick, the well depth is 6m). The dewatering wells use Φ150mm PVC pipes with holes drilled in the pipe wall (8mm diameter, 100mm hole spacing, spiral distribution). The pipes are wrapped with two layers of geotextile (200g / ㎡) and one layer of wire mesh (2mm diameter) to prevent the filter holes from clogging.

[0016] The rainwater mixture is filled into the rainwater well to the same height as the wellhead. At the same time, a small water pump (head ≥10m, flow rate ≥5m³ / h) is installed at the wellhead. A 5cm-8cm thick rainwater mixture cushion layer is laid within 2m around the well to form a "well and cushion layer" coordinated rainwater system.

[0017] Step 2.3, Precipitation Process Control: Start the water pumps, initially controlling the pumping rate at 2-3 m³ / h, monitoring the precipitation depth and sediment content of the pumped water every 2 hours; once the precipitation depth reaches 2 m, gradually increase the pumping rate to 4-5 m³ / h, ensuring the sediment content is ≤0.5% (if exceeding this limit, reduce the pumping rate and inspect the filter tube wrapping); stop precipitation when the foundation moisture content drops to 35%-40%. The precipitation rate at this stage can reach 0.8-1.2 m / d, 2-4 times higher than traditional methods.

[0018] The third step is the stage of graded consolidation of multi-component solid waste. Step 3.1, Primary consolidation (i.e., bottom layer consolidation, thickness 20-25cm): Consolidation material ratio: By mass ratio, 20%-25% red mud, 30%-35% slag, 25%-30% fly ash, and 10%-15% desulfurized gypsum are added, along with 15%-20% of gypsum slurry (prepared in the early stage) and stirred for 4-6 minutes to prepare the primary consolidation material. The slump of the primary consolidation material is 120mm-150mm. Among them, desulfurized gypsum provides Ca²⁺ to activate the activity of slag and fly ash, generating ettringite and CSH gel, while red mud fills the micropores and improves the structural density.

[0019] Construction process: A TL-1800 paver is used to lay the primary consolidation material in layers, with each layer being 10cm-12cm thick. After laying, a YZC20 vibratory roller is used to compact the material 2-3 times (frequency 30Hz, amplitude 1mm, pressure 150kPa-180kPa). The compaction degree after rolling is ≥93%. Three sets of samples are taken per 1000㎡ for testing using the ring cutter method. Areas that fail to meet the requirements are compacted again.

[0020] Step 3.2, Secondary consolidation (i.e., upper layer consolidation, thickness 15-20cm): Consolidation material ratio: by mass ratio, 15%-20% red mud, 20%-25% slag, 35%-40% fly ash, and 15%-20% desulfurized gypsum are added to 12%-15% of the total mass of the materials, and stirred for 3-5 minutes to prepare a secondary consolidation material; the slump of this secondary consolidation material is 100mm-120mm, and the fly ash content is increased to optimize permeability and enhance the subsequent drainage consolidation effect.

[0021] Construction process: After curing the primary consolidation layer for 3 days (covered with geotextile during curing, and watered twice a day to keep the surface moist), lay the secondary consolidation material, using the same spreading and compaction process as the primary consolidation, with a compaction degree ≥92%; after compaction, cover with two layers of geotextile and one layer of plastic film for moisture retention and curing, with the curing temperature controlled at 20-25℃, and the curing time 7-10 days. During this period, monitor the pore water pressure every two days. When the pore water pressure dissipation rate is ≥85%, consolidation is complete.

[0022] The construction method of the present invention will be described in detail below with reference to specific engineering examples.

[0023] The project involves the reclamation of 15,000 square meters of ultrafine-grained soil for a coastal land reclamation project. The soil layer is 4-6 meters thick, with an average moisture content of 65%, a void ratio of 1.8, and a permeability coefficient of 1.2 × 10⁻⁻⁻⁶. 7 cm / s, foundation bearing capacity 70kPa, bearing capacity after treatment ≥180kPa, moisture content ≤40%, construction period 30 days.

[0024] According to the above construction design, the steps are as follows: S1. Preliminary Preparations S11) Site investigation: 450 boreholes were drilled, and it was found that the 0-3m range was a high moisture content zone (62%-70%), the 3m-6m range was a medium moisture content zone (50%-62%), and the underlying layer was silty clay with a bearing capacity of 200kPa.

[0025] S12) Solid waste pretreatment: Red mud is dried to a moisture content of 12% and crushed to a particle size of 1.8 mm; fly ash is passed through an 80-mesh sieve with a SiO2+Al2O3 content of 72%; desulfurized gypsum is crushed to 2.5 mm and made into gypsum slurry; slag is ground to a specific surface area of ​​380 m² / kg and an activity index of 78%.

[0026] S2. Solid waste co-precipitation S21) Precipitation mixture ratio: 28% red mud, 38% fly ash, 24% slag, 10% desulfurized gypsum, plus 10% water to make a mixture with a moisture content of 20%.

[0027] S22) Construction of dewatering wells: A total of 3750 dewatering wells were set up (well spacing 2m×2m, well depth 7m), filled with dewatering mixture, and pumped. A 6cm thick mixture cushion layer was laid around the wells, and the pumps were started. The initial pumping rate was 2.5m³ / h. After 5 days, the dewatering depth reached 2.5m, and the pumping rate was increased to 4.5m³ / h. On the 10th day, the soil moisture content dropped to 38%, and dewatering was stopped. The average dewatering rate was 1.0m / d, and there was no filter pipe blockage.

[0028] S3. Staged consolidation of multi-component solid waste S31) Primary consolidation: Material ratio: 22% red mud, 32% slag, 28% fly ash, 18% desulfurized gypsum, plus 18% gypsum slurry to make a primary binder (slump 135mm).

[0029] Construction: Lay in two layers (12cm each), compact with a vibratory roller 3 times to achieve a compaction degree of 94%; cure for 3 days, during which water is sprayed twice a day to maintain a surface moisture content of ≥80%.

[0030] S32) Secondary consolidation: Material proportions: By mass ratio, red mud 18%, slag 22%, fly ash 38%, desulfurized gypsum 22%, plus gypsum slurry 14%, to make a secondary consolidation material with a slump of 110mm.

[0031] Construction: Lay an 18cm thick layer, vibrate and compact twice, achieving a compaction degree of 93%; cover with geotextile and plastic film for 8 days of curing, with pore water pressure dissipation rate reaching 88% on the 8th day, indicating consolidation is complete.

[0032] The construction benefits of this project after construction using the method of this invention are as follows: 1. Performance indicators: After treatment, the average moisture content of the foundation is 36%, the bearing capacity is 210 kPa, and the permeability coefficient is increased to 2.5 × 10⁻ 5 cm / s, meeting design requirements.

[0033] 2. Construction period and cost: The total construction period is 28 days (completed 2 days ahead of schedule), and the amount of solid waste disposed of is 13,500 tons (3,240 tons of red mud, 4,860 tons of fly ash, 2,430 tons of desulfurized gypsum, and 3,000 tons of slag). The overall construction cost is 35% lower than that of the vacuum preloading method.

[0034] Environmental benefits: Reduces the land occupied by solid waste storage by 20 mu, reduces cement usage by 800 tons (reduces carbon emissions by about 1,000 tons), and eliminates secondary pollution.

[0035] Comparative verification: Compared with the traditional vacuum preloading method (with a 1000㎡ comparison area selected in the same site), the method of the present invention has significant advantages in terms of precipitation rate (1.0m / d vs 0.2m / d), consolidation period (28 days vs 180 days), solid waste utilization rate (90% vs 0), and overall cost (65 yuan / ㎡ vs 100 yuan / ㎡). Moreover, the foundation bearing capacity is higher and the stability is better after treatment.

[0036] This invention uses red mud, fly ash, desulfurized gypsum, and slag as core materials. Different proportions of these materials are mixed with appropriate amounts of water to create a rainwater mixture. A slightly larger amount of gypsum slurry is added to create a softer primary consolidating material, and a slightly larger amount of gypsum slurry is added to create a harder secondary consolidating material. The rainwater mixture is laid as the lower layer of the foundation, and rainwater wells and pumps are installed to drain the foundation. Then, the primary consolidating material is laid in layers on the surface of the rainwater mixture, and after curing, the secondary consolidating material is laid.

[0037] The beneficial effects of this invention are: 1. High precipitation efficiency: Through the coordinated design of "fly ash diversion channel + red mud anti-clogging", the precipitation rate reaches 0.8-1.2m / d, which is 2-4 times higher than the traditional method, and the precipitation depth can reach 4-6m, which meets the construction moisture content requirements.

[0038] 2. Excellent consolidation effect: The graded consolidation material, through the synergistic effect of chemical cement (ettringite, CSH gel) and physical filler (red mud, slag), increases the bearing capacity of the foundation by 2-3 times after consolidation (from 50-80kPa to 150-200kPa), and shortens the consolidation period to 15-20 days, which is significantly reduced compared to the traditional method (6-12 months).

[0039] 3. High solid waste utilization rate: The amount of solid waste in a single project accounts for more than 90% of the total mass of the treated materials. Every 10,000 square meters of site can dispose of 800-1200 tons of solid waste such as red mud, fly ash, desulfurization gypsum, and slag, reducing solid waste storage pollution.

[0040] 4. Low cost: The cost of solid waste materials is only 1 / 3 to 1 / 2 of that of cement, and there is no need for a large number of drainage boards and sealing membranes. The overall construction cost is reduced by 30% to 40% compared with the vacuum preloading method.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes made based on the content of this specification are included within the scope of the present invention.

Claims

1. A method for constructing a multi-component solid waste co-utilization treatment method for hydraulically filled ultrafine-grained soil foundation, characterized in that, Includes the following steps: The first step is the preliminary preparation stage. Step 1.1, Site Investigation: A geological drilling rig was used to drill holes in a 5m×5m grid, penetrating the fill layer to the underlying stable layer. A soil sample was taken every 1m to determine its moisture content, void ratio, and permeability coefficient. At the same time, a static cone penetrometer was used to determine the bearing capacity of the foundation and to divide the foundation into high moisture content zone, medium moisture content zone, and low moisture content zone. Step 1.2, Solid Waste Pretreatment: Red mud: It is dried to a moisture content of 10%-15% using a drum dryer, and then crushed to a particle size of ≤2mm using an impact crusher to remove large impurities; Fly ash: Pass through an 80-mesh vibrating screen to remove impurities and ensure that the SiO2+Al2O3 content is ≥70%; Desulfurized gypsum: crushed to a particle size ≤3mm by a jaw crusher, then mixed with water at a mass ratio of 1:2 to form a gypsum slurry for later use; Slag: Grind using a ball mill to a specific surface area of ​​350m²-400m² / kg, ensuring an activity index ≥75%; The second step, the solid waste-assisted precipitation stage, targets areas with high and medium moisture content: Step 2.1, Preparation of precipitation materials: Mix red mud 25%-30%, fly ash 35%-40%, slag 20%-25%, and desulfurized gypsum 5%-10% by mass, add water accounting for 8%-12% of the total mass of the mixed materials, and mix with a forced mixer to prepare precipitation mixture; Step 2.2, Construction of the dewatering structure: In areas with high water content, dewatering wells are arranged in a quincunx pattern with a well spacing of 2m×2m and a well depth of 1.2 times the thickness of the backfill layer; the dewatering wells use Φ150mm PVC pipes with holes drilled in the pipe walls, and are wrapped with two layers of geotextile and one layer of wire mesh to prevent the filter holes from clogging. Fill the dewatering mixture into the dewatering well, with the filling height level with the well opening. At the same time, install a water pump at the well opening and lay a 5cm-8cm thick dewatering mixture cushion layer within a 2m radius around the well. Step 2.3, Precipitation Process Control: Start the water pumps, initially controlling the pumping rate at 2m³-3m³ / h, and monitor the precipitation depth and sediment content of the pumped water every 2 hours; when the precipitation depth reaches 2m, gradually increase the pumping rate to 4m³-5m³ / h, and the sediment content must be ≤0.5%; when the foundation moisture content drops to 35%-40%, stop the precipitation. The third step is the stage of graded consolidation of multi-component solid waste. Step 3.1, First-stage consolidation: Consolidation material ratio: by mass ratio, red mud 20%-25%, slag 30%-35%, fly ash 25%-30%, desulfurized gypsum 10%-15%, add gypsum slurry accounting for 15%-20% of the total mass of materials, stir for 4min-6min to make primary consolidation material, the slump of primary consolidation material is 120mm-150mm; Construction process: The first-level consolidation material is laid in layers using a paver, with each layer being 10cm-12cm thick. After laying, it is compacted 2-3 times with a vibratory roller. The compaction degree after rolling is ≥93%. Three sets of samples are taken for testing every 1000㎡ using the ring cutter method. Areas that fail to meet the requirements are compacted once. Step-by-step 3.2, secondary consolidation: Consolidation material ratio: by mass ratio, red mud 15%-20%, slag 20%-25%, fly ash 35%-40%, desulfurized gypsum 15%-20%, add gypsum slurry accounting for 12%-15% of the total mass of materials, stir for 3 min-5 min to prepare secondary consolidation material; the slump of the secondary consolidation material is 100mm-120mm; Construction process: After curing the primary consolidation layer for 3 days, lay the secondary consolidation material, using the same paving and compaction process as the primary consolidation layer, with a compaction degree ≥92%; After compaction, cover with two layers of geotextile and one layer of plastic film for moisture retention and curing. The curing temperature is controlled at 20℃-25℃, and the curing time is 7-10 days. During this period, the pore water pressure is monitored every two days. When the pore water pressure dissipation rate is ≥85%, the consolidation is complete.