Construction process of electrolytic manganese residue embankment

Abstract

The invention discloses a construction process of an electrolytic manganese residue embankment, and belongs to the technical field of resource utilization of industrial waste residues. The process comprises the following steps: firstly, mixing original electrolytic manganese slag with a stable curing material, an auxiliary material and water in a plant according to a ratio to form a harmless manganese slag mixture; then transporting the mixture to a site for paving, leveling and rolling to form an embankment main body; and finally, edge covering protection slopes are arranged on the two sides of the embankment, an isolation layer is arranged at the bottom, a capping layer is arranged at the top, and a drainage system is matched. According to the method, soluble manganese and ammonia nitrogen in the manganese slag are effectively cured through a specific stable curing material ratio and a normative construction process, so that the leaching toxicity meets the environmental protection standard, and meanwhile, the manganese slag embankment has the excellent engineering performance that the compaction degree is larger than or equal to 98.6%, the rebound modulus reaches 76 MPa, and the post-construction settlement is smaller than 2 mm. According to the process, large-scale resource utilization of the electrolytic manganese residues is achieved, and both environmental benefits and economic benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of industrial waste resource utilization technology, specifically to a construction process for an electrolytic manganese slag embankment. Background Technology

[0002] Electrolytic manganese slag is a large-scale industrial solid waste generated during the electrolytic manganese production process. With the increasing depletion of manganese ore resources, electrolytic manganese enterprises currently generally use low-grade manganese ore (grade below 10%) as raw material, resulting in the generation of more than 10 tons of manganese slag for every 1000 kg of metallic manganese produced. Statistics show that the total amount of manganese slag stored in the open in my country currently exceeds 100 million tons, and continues to grow at a rate of more than 10 million tons per year. Open storage of manganese slag not only occupies a large amount of land resources but also poses a serious threat to the surrounding environment. In the early stages of the manganese industry's development, most production enterprises lacked sufficient awareness of the environmental impact of manganese slag storage, and slag storage facilities generally lacked effective seepage prevention measures. Under the action of rainwater runoff, heavy metal ions and toxic salts in the manganese slag enter the soil and groundwater systems with leachate, and even flow into surrounding rivers and lakes, causing irreversible damage to the ecological environment. The long-term release of pollutants from manganese slag has brought serious environmental pollution and safety hazards.

[0003] With increasingly stringent national environmental protection requirements, finding economical and effective manganese slag disposal technologies has become a key and challenging area of ​​research in the industry. The main disposal methods are currently listed in the table below:

[0004] Although various treatment methods have been proposed, each of these methods has its own advantages and disadvantages, and lacks large-scale industrial or engineering verification, resulting in limited practical application effects.

[0005] According to the test results of the "Leaching Toxicity Method for Solid Waste - Horizontal Oscillation Method" (HJ557-2010), the concentrations of manganese and ammonia nitrogen in the leachate of electrolytic manganese slag reached 1097.713 mg / L and 595 mg / L, respectively, exceeding the limits of the "Integrated Wastewater Discharge Standard" (GB8978-1996) by 548 times and 24 times, respectively, classifying it as Class II industrial solid waste. Soluble manganese and ammonia nitrogen have become the main obstacles to the resource utilization of manganese slag. The soluble manganese in manganese slag mainly comes from about 15% of the unelectrolyzed manganese elements during the electrolysis process, while ammonia nitrogen comes from the ammonia water added during the solution preparation stage to adjust the pH value (6.5~7.0), ultimately remaining in the manganese slag in the form of NH4+.

[0006] In the application of industrial waste slag in roadbed construction, existing technologies, such as prior art document CN101343852B, disclose a method for constructing highway roadbeds using waste steel slag. This method includes using waste steel slag to fill the roadbed, controlling the filling rate to ensure stability, determining compaction parameters through experiments, and designing a reasonable embankment cross-sectional structure, including a top sealing layer, a bottom sealing layer, slope protection, and a drainage system. Although this method provides a useful reference for the resource utilization of industrial waste slag, it still has limitations. It lacks a comprehensive quality control system for electrolytic manganese slag roadbeds, including technical specifications for raw material control, production process monitoring, and construction quality inspection, and cannot ensure the long-term environmental safety and structural stability of the roadbed project.

[0007] The "Manganese Triangle" region, encompassing Guizhou, Hunan, and Chongqing, is not only a concentration area for the electrolytic manganese industry but also a region experiencing rapid infrastructure development. These areas have complex terrain, large-scale roadbed excavation and filling, and an urgent need for filler materials. Large-scale application of electrolytic manganese slag in highway subgrades could solve the environmental problems caused by manganese slag storage and reduce highway construction costs, yielding significant environmental and economic benefits. However, achieving this goal requires overcoming the following technical bottlenecks: 1) developing a stabilization material system for the synergistic solidification of manganese and ammonia nitrogen; 2) establishing comprehensive quality control standards for manganese slag subgrade construction; 3) verifying the long-term environmental safety and engineering performance of manganese slag subgrades; and 4) developing systematic technical specifications for the design and construction of manganese slag subgrades.

[0008] Against this backdrop, through systematic technical breakthroughs, this invention proposes a complete construction process for electrolytic manganese slag embankments, providing an effective technical approach for the resource utilization of electrolytic manganese slag. Summary of the Invention

[0009] The purpose of this invention is to effectively solidify soluble manganese and ammonia nitrogen in manganese slag through a specific stable solidification material ratio and standardized construction process, ensuring that the leaching toxicity meets environmental standards. Simultaneously, it enables manganese slag embankments to possess excellent engineering performance: compaction degree ≥98.6%, resilient modulus up to 76 MPa, and post-construction settlement less than 2 mm. This process realizes the large-scale resource utilization of electrolytic manganese slag, achieving both environmental and economic benefits.

[0010] The technical solution of this invention: a construction process for an electrolytic manganese slag embankment, comprising the following steps: Step 1: Mix the original electrolytic manganese slag with stabilizing and solidifying materials, auxiliary materials and water in a predetermined ratio to form a harmless manganese slag mixture that meets environmental protection and road performance indicators. Step 2: Transport the harmless manganese slag mixture to the construction site, spread, level and compact it to form the main body of the embankment; Step 3: Set up earthen edging slopes on both sides of the main body of the embankment, set up an isolation layer at the bottom, set up a sealing layer at the top, and provide a drainage system; wherein, the width of the earthen edging slopes shall not be less than 2 meters, and the clay shall be clay with a plasticity index of not less than 7; the isolation layer shall be natural sand and gravel, crushed stone or environmentally friendly industrial waste, with a maximum particle size of not more than 8 cm, a fine material content of less than 5 mm of ≤30%, and a mud content of <5%; the sealing layer shall be dense clay or dense integral material, with a thickness of not less than 25 cm.

[0011] Furthermore, the stabilizing and curing materials include quicklime, cement, fly ash, and trisodium phosphate, which solidify soluble manganese and ammonia nitrogen in manganese slag through the synergistic effect of chemical stabilization and physical encapsulation.

[0012] Furthermore, the quicklime is calcareous quicklime with a calcium oxide content ≥90% and an activity ≥80%; the trisodium phosphate has an effective content ≥98%; the fly ash meets the technical requirements for Grade II fly ash in GB 1596-91; and the cement meets the requirements of GB 175-2007.

[0013] Furthermore, the auxiliary material is coarse crushed stone rolled from hard or medium-hard rock or coarse-grained mountain stone with a mud content of <5%, with a maximum aggregate size of <100mm and the portion with a particle size of less than 4.75mm screened out, and its addition amount accounts for 10%-30% of the total mass of the harmless manganese slag mixture.

[0014] Furthermore, the production of the harmless manganese slag mixture adopts a special intermittent mixing equipment. The mixed mixture needs to be left to stand for more than 24 hours to allow the ammonia gas to escape fully, and the moisture content of the mixture at the outlet is controlled to be 2%-3% higher than the optimum moisture content.

[0015] Furthermore, the paving adopts a horizontal layered filling method, with a loose paving coefficient of 1.2~1.3 and a compaction thickness not exceeding 30cm.

[0016] Furthermore, the forming and compaction process meets the following requirements: a 20-30 ton vibratory roller is used for compaction; the number of compaction passes is no less than 4; the compaction path follows the principle of compacting from the sides to the middle, and for curved sections, compaction proceeds from the inside to the outside; adjacent wheel tracks overlap by 1 / 3 of the wheel width; the compaction speed is controlled at 35-40 m / min; for local areas that the roller cannot effectively compact, a small vibratory tamper is used for supplementary compaction. The compaction uses a 20-30 ton vibratory roller, and the number of compaction passes is no less than 4.

[0017] Furthermore, the transportation of the harmless manganese slag mixture shall meet the following requirements: a vehicle with a single transport capacity of not less than 20 tons and an intact cargo box shall be used for transportation, and the cargo box shall be sealed with a rainproof cloth that can cover all materials, prevent rain and prevent ammonia gas from escaping throughout the journey; any remaining mixture transported to the site shall be returned to the treatment plant and shall not be disposed of at will.

[0018] Furthermore, asphalt is applied to the contact area between the embankment and the bridge / culvert structure for corrosion protection.

[0019] Furthermore, the following quality control procedures will be implemented during construction: 1) Conduct raw material quality inspections on the incoming quicklime, fly ash, auxiliary materials, cement, and trisodium phosphate according to the predetermined inspection items and frequencies; 2) For each batch of harmless manganese slag mixture, sampling shall be conducted at the frequency specified in the "Technical Specification for Sampling and Sample Preparation of Industrial Solid Waste" (HJ / T 20-1998), and the concentrations of manganese and ammonia nitrogen in its leachate shall be tested to ensure that the limit requirements of the "Integrated Wastewater Discharge Standard" (GB 8978) are met. 3) After the construction of each compacted layer is completed, compaction degree test shall be carried out at a frequency of 2 points per 200 meters of each compacted layer to ensure that the value meets the requirements of the highway subgrade design specifications for the corresponding filling parts; 4) After the embankment is constructed to the design elevation, the deflection, longitudinal elevation, centerline deviation, width, flatness, cross slope and side slope of the embankment shall be inspected and accepted for final quality.

[0020] The beneficial effects of this invention are: 1. This invention has excellent engineering performance and good compaction performance: the compaction degree can reach 98.6% after 4 passes of rolling, resulting in high construction efficiency; strong bearing capacity: the rebound modulus reaches 76MPa, which is superior to conventional roadbed materials; reliable stability: the post-construction settlement is small (maximum 1.94mm), and it is basically stable within 60 days.

[0021] 2. This invention has significant economic benefits, saves engineering costs, greatly reduces construction costs, reduces manganese slag disposal costs, improves efficiency through standardized construction, and reduces potential quality risks.

[0022] 3. This invention features significant technological innovation, forming a complete system of harmless treatment and standardized construction technology, establishing full-process quality control standards, ensuring environmental protection and safety, and providing a successful example for the resource utilization of industrial solid waste.

[0023] 4. This invention has significant social value, promotes the development of a circular economy, turns waste into treasure, and is particularly suitable for promotion and application in the manganese triangle region, promoting the integration of environmental protection industry and infrastructure construction. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the construction process of manganese slag embankment; Figure 2 This is a schematic diagram of the mixing and process flow of manganese slag embankment mixture; Figure 3 This is a schematic diagram of the relationship between compaction degree and number of compaction passes; Figure 4 This is a schematic diagram of the pL curve from the load-bearing plate experiment; Figure 5 This is a schematic diagram of the pL curve from the load-bearing plate experiment; Figure 6 This is a schematic diagram showing the change in the amplitude of the vibrating wire of the lateral stress pressure box at the No. 1 detection section; Figure 7 This is a schematic diagram showing the change in the amplitude of the vibrating wire of the vertical stress pressure box at the No. 1 detection section; Figure 8 This is a schematic diagram showing the change in the amplitude of the vibrating wire of the lateral stress pressure box at the No. 2 detection section; Figure 9 This is a schematic diagram showing the change in the amplitude of the vibrating wire of the vertical stress pressure box at the No. 2 detection section. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0027] Example 1: Raw materials and construction equipment for manganese slag embankments. The raw materials include the following materials. Harmless manganese slag mixture: The manganese slag mixture obtained after harmless treatment using stabilization and solidification technology is mainly composed of original manganese slag, externally added stabilizing and solidifying materials, auxiliary materials, and water.

[0028] Raw manganese slag: Raw manganese slag can be newly produced manganese slag from electrolytic manganese plants or manganese slag stored in stockpiles. The moisture content of the raw manganese slag should be tested before use, as this will serve as the basis for adjusting the proportion of admixtures and the operating parameters of the harmless treatment equipment.

[0029] Stabilizing and curing materials: Stabilizing and curing materials include alkali-activated materials and stabilizing materials, and their technical performance should meet the corresponding index requirements. Fly ash: Meets the technical index requirements for Grade II fly ash in GB 1596-91. Cement: Silicate cement, ordinary Silicate cement, slag Silicate cement, etc., can all be used. Technical performance should meet the requirements of "General Silicate Cement" (GB 175-2007). Quicklime: Calcium quicklime should be used, with a minimum calcium oxide content of 90% and an activity of not less than 80%. Trisodium phosphate: Effective component not less than 98%. Water: The harmless manganese slag mixture should be potable water, free from harmful soluble salts, substances that may cause chemical reactions, and other pollutants.

[0030] Auxiliary materials: The auxiliary materials required for the harmless manganese slag mixture can be coarse crushed stone made from hard or medium-hard rock (uniaxial saturated compressive strength ≥30MPa) or coarse-grained granite with a mud content <5%, with a maximum aggregate size <100mm and the portion smaller than 4.75mm screened out. Its main functions are to assist in the uniform mixing of the original manganese slag with the externally added stabilizing and solidifying materials; to give the harmless manganese slag mixture good workability for transportation, paving, leveling, and compaction during the construction phase; and to adjust the moisture content of the mixture. Its strength, stability, and other technical properties must meet the requirements for roadbed filling quality in the "Technical Specification for Highway Subgrade Construction" (JTG / T-3610-2019).

[0031] Design of the composition of harmless manganese slag mixture: The stabilizing and solidifying materials added to the harmless manganese slag mixture include quicklime, cement, fly ash, trisodium phosphate, etc. The amount of each added material must ensure that the mixture meets the relevant index requirements of the "Technical Specification for Pollution Control of Manganese Slag" (HJ 1241—2022), "Integrated Wastewater Discharge Standard" (GB 8978), "Specifications for Design of Highway Subgrade" (JTGD30-2015), and "Technical Specifications for Construction of Highway Subgrade" (JTG T3610-2019).

[0032] The equipment for the harmless treatment of manganese slag is as follows: the production equipment for the harmless treatment plant of manganese slag is shown in Table 1, and the equipment for the embankment filling of harmless manganese slag is shown in Table 2.

[0033] Table 1

[0034] Table 2

[0035] Before the formal construction begins, all construction machinery and auxiliary tools should be prepared and kept in good working order.

[0036] Example 2: Pre-construction preparations, including foundation condition investigation and treatment and construction of the test section. A survey of the topography, geomorphology, geology, and hydrogeology of the proposed construction section should be conducted to develop a scientifically sound filling plan. The original ground surface should be treated according to the relevant requirements of the "Technical Specifications for Highway Subgrade Construction" (JTG T3610-2019). The moisture content of the untreated manganese slag used in construction should be checked to determine the amount of auxiliary materials to be added. The quality and quantity of the externally added stabilizing and solidifying materials should meet the aforementioned requirements. The construction site for the manganese slag embankment should preferably be enclosed. If enclosed operation is not possible, traffic control should be implemented, and safety guides, indicator signs, speed limit signs, and traffic restriction signs should be set up.

[0037] Construction of the test section: Before the large-scale formal construction of the manganese slag embankment, a test section with a length of not less than 200m should be paved. The purpose of paving the test section is to achieve the following: verify the applicability and coordination of the paving and leveling equipment and compaction equipment used in the formal construction; verify the process parameters such as the tonnage of the compaction equipment, compaction thickness and loose paving coefficient, number of compaction passes, and compaction speed that meet the compaction quality requirements; determine the appropriate length of each working surface; determine the joint treatment plan; and establish the standard construction method for harmless manganese slag embankment.

[0038] The raw materials, construction machinery, construction methods, and all testing items of the test section all meet the regulations. After the supervisor confirms that the test section is qualified through random inspection, a "Test Section Construction Summary" can be prepared based on the above content. After preliminary review by the resident office and approval by the chief supervisor's office, large-scale construction can begin.

[0039] Example 3: Overall construction process of manganese slag embankment, referring to Figure 1 The following steps are included Step 1: Construction surveying. Use a total station to re-measure the traverse points, set roadbed side stakes at 20m intervals, measure the original ground elevation, and draw a cross-section diagram. Step 2: Original ground treatment, remove the top 30cm of cultivated soil, weeds, tree roots and other organic matter, level the site, control the slope at 2%-4%, and compact it 4-6 times with an 18-21t smooth drum roller. The foundation bearing capacity test requirement is ≥100kPa. Step 3: Mixing of manganese slag mixture, using MBW-600 manganese slag special mixer, mixing capacity: 600t / h, mixing time ≥90s, uniformity control of mixture: coefficient of variation ≤10%, discharge temperature: ambient temperature + (5-10)℃; Step 4: Mixture transportation and paving. Transportation vehicles: dump trucks of 20t or more, equipped with GPS positioning. Paving equipment: ABG-8620 paver or equivalent equipment. Paving speed: 2-4m / min, uniform and continuous paving. Loose paving thickness control: 36±2cm (compacted thickness 30cm). Step 5: Leveling and compaction, and moisture content testing. Grade the road surface with a grader to achieve a flatness of ≤20mm / 3m. Use a light roller (12-15t) to compact the surface 1-2 times. Use a rapid moisture meter to test the moisture content at 3 points per 1000㎡. Moisture content control range: optimum moisture content ±2%. Step 6: Replenish water or dry. If the moisture content is too low: use a water truck to atomize water and replenish it in 2-3 times. If the moisture content is too high: use a rotary tiller to loosen and dry the soil. The loosening depth should be ≥20cm. After adjustment, retest the moisture content. Only after it is qualified can the next process be carried out. Step 7: Shaping, using a grader for precise shaping; road camber cross slope control: 2%-4%, elevation control and width control; Step 8: Compaction and compaction degree testing. Compaction equipment combination: light roller (12-15t), vibratory roller (20-30t), and small vibratory rammer. Rolling process parameters: Static rolling 1 pass: speed 25-30m / min; Weak vibration 2 passes: frequency 28-32Hz, amplitude 0.8-1.2mm; Strong vibration 2-3 passes: frequency 32-35Hz, amplitude 1.5-2.0mm; Static rolling finishing 1 pass: speed 25-30m / min. Compaction degree test: Test frequency: 4 tests per 200m of compacted layer; Test method: Sand cone method, sampling depth through the entire compacted layer; Acceptance standard: Compaction degree ≥93%; Step 9: Traffic Control Step 10: Lay the next layer. Interlayer interval: ≥24 hours. Interlayer treatment: Remove loose material from the surface and moisten with water. Elevation control: Re-measure the elevation after each layer is constructed. Continuous monitoring: Set a settlement observation point every 50m.

[0040] Special working conditions: During the rainy season, prepare rainproof tarpaulins, cover the soil promptly, and set up temporary drainage ditches with a slope of ≥3%. After rain, test the moisture content and dry the soil if necessary; during low-temperature construction, cover the soil immediately after compaction for insulation.

[0041] Figure 2 The following is the mixing process for manganese slag embankment mixture. During the overall construction, the following process steps also require attention: 1. Mix proportion design of the mixture Manganese slag mixtures used in highway subgrade engineering should simultaneously meet the environmental protection indicators specified in the "Technical Specification for Pollution Control of Manganese Slag" (HJ1241—2022) and the "Integrated Wastewater Discharge Standard" (GB 8978), as well as the relevant technical requirements of the "Specification for Design of Highway Subgrade" (JTGD30-2015) and the "Technical Specification for Construction of Highway Subgrade" (JTG T3610-2019).

[0042] The target mix design for the mixture should be carried out in accordance with the above-mentioned specifications and standards to determine the maximum dry density and optimum moisture content of the mixture. Before formal mixing, the construction mix proportion should be determined based on the properties of each raw material, serving as the basis for determining the operating parameters of each piece of equipment in the production system and for quality control.

[0043] 2. Mixing the ingredients The manganese slag mixture for roadbeds should be produced using the aforementioned specialized equipment. A trial mix should be conducted before formal mixing to determine the operating parameters of each piece of equipment and ensure that the mixing quality meets environmental protection and road performance requirements. Each raw material should be accurately measured according to the proportions before entering the mixing plant, and traceable original records for each batch should be maintained. When adding raw materials to each batch, the order should be: first the auxiliary materials, then the manganese slag and the stabilized and solidified material mixture.

[0044] Harmless manganese slag mixtures should be produced according to the project size and schedule. Batches of mixtures should be stacked sequentially according to production date, with the first batch produced being shipped first. Newly produced mixtures should be allowed to stand for at least 24 hours after production to allow residual ammonia to fully dissipate. When preparing the mixtures, the moisture content should be increased by 2%–3% above the optimum moisture content, taking into account transportation distance, temperature, and construction delays, so that the moisture content is optimal during compaction. Samples should be taken and sent for testing promptly according to the testing frequency specified in the "Technical Specification for Sampling and Sample Preparation of Industrial Solid Waste" (HJ / T20-1998), based on the production volume of each batch of mixtures.

[0045] 3. Transportation of harmless manganese slag from mixed materials Vehicles used for transporting manganese slag mixtures must have a single carrying capacity of no less than 20 tons, with intact cargo boxes to ensure no leakage or spillage during transport. Each vehicle must have a complete tarpaulin with sufficient area to cover the entire cargo box, providing protection against rain and ammonia gas leakage, and securely fastened. Unauthorized removal of the tarpaulin covering during transport is prohibited. The transport of the mixture will be organized according to the quantity required for each stage of roadbed construction, using a centralized loading and delivery method to the construction site.

[0046] Vehicles involved in transporting the asphalt mixture must undergo a vehicle condition inspection to ensure they are in good working order. Transportation must be strictly organized according to the pre-planned transportation route. Random parking outside the construction site is prohibited during transportation. Each batch of asphalt mixture must arrive at the roadbed construction site simultaneously and be unloaded at designated locations under the direction of on-site construction personnel; unloading at undesignated locations is strictly prohibited. If a breakdown occurs during transportation, prolonged parking in densely populated areas along the route is prohibited.

[0047] The quantity of mixed material transported to the site should be strictly controlled according to the amount of work. Any excess material from each batch of mixed material must not be dumped outside the roadbed construction area. The excess material must be transported back to the manganese slag harmless treatment plant (station).

[0048] 4. Spreading, leveling, and compacting the mixture The horizontal layered filling method is adopted. Before paving, loose-lay thickness control marks should be set to ensure consistent paving thickness, with a loose-lay coefficient of 1.2~1.3. A bulldozer can be used for initial leveling of the mixture, followed by a grader for final leveling. If available, a stabilized soil paver can be used for paving. The loose-lay thickness (compacted thickness not exceeding 30cm) should be strictly controlled according to the standard construction methods summarized from the test section, ensuring that the compaction degree of the rolled layer meets the specifications throughout its full thickness. After leveling, a medium-light roller should be used for 1~2 passes of compaction, with the rolling speed controlled at 25~35m / min.

[0049] 5. Molding and compaction After the working surface is stabilized, a grader is used to precisely shape the construction layer. Then, a 20-30 ton vibratory roller is used, following the principle of "light to heavy, low to high," compacting from the sides to the middle (from the inside to the outside on curved sections) in a slow-to-fast manner. Adjacent wheel tracks should overlap by 1 / 3 of the wheel width to ensure uniform compaction until the compaction degree meets the specifications. The compaction speed is controlled at around 35-40 m / min, and the roller should avoid turning back on the same cross section each time.

[0050] Areas that cannot be compacted by a localized road roller should be compacted using a small vibratory tamper. After the construction layer is compacted, the compaction degree should be tested at the specified frequency. If it does not meet the requirements, additional compaction is required.

[0051] When the slope protection soil and fly ash are filled in layers, the slope protection soil should be filled and compacted first, and then the fly ash should be filled in, ensuring that the top surface of the fly ash is higher than the slope protection soil to form a transverse drainage slope to prevent water accumulation.

[0052] Environmental restrictions: The construction temperature must be above 0℃, and construction should not be carried out on rainy days to prevent the roadbed materials from getting damp.

[0053] 6. Health preservation and traffic control If the next working layer cannot be constructed continuously, the surface of the working layer that has been compacted should be appropriately sprayed with water for wet curing. The standard is that the surface of the working layer is moist but does not form runoff. High water pressure and high flow rate are prohibited from eroding the surface of the working layer.

[0054] Vehicles are prohibited from traveling at high speeds on compacted work surfaces. Tracked equipment is prohibited from operating on work surfaces where manganese slag mixture is laid. Construction mobile equipment is prohibited from sudden stops, starts, turns, or U-turns on work surfaces.

[0055] Example 4: Construction Quality Control During construction, raw material inspections and tests, arrival tests, and process inspections are conducted on all materials used at any time. Specific inspection items are shown in Table 3. Table 3

[0056] Sampling and testing should be conducted according to the testing frequency and methods specified in the "Technical Specification for Sampling and Sample Preparation of Industrial Solid Waste" (HJ / T20-1998) based on the output of each batch of mixed material. The testing frequency is shown in Table 4, and the testing indicators refer to the "Integrated Wastewater Discharge Standard" (GB 8978) to ensure that the environmental quality of the mixed material meets the standards.

[0057] Table 4

[0058] During the construction of manganese slag embankments, the compaction quality should be tested layer by layer according to Table 5.

[0059] Table 5

[0060] After the manganese slag subgrade construction reaches the design elevation, a final quality inspection and acceptance should be conducted according to the indicators listed in Table 6. Only if the quality meets the requirements can the remaining construction work proceed.

[0061] Table 6

[0062] After stabilization and solidification treatment, the engineering performance of electrolytic manganese slag fully meets the technical requirements of highway embankments. It exhibits excellent performance in terms of compaction characteristics, bearing capacity, settlement control, and stress distribution, and its technical feasibility has been fully verified, as detailed below: 1. Compaction degree and number of rolling passes of manganese slag mixture Through on-site compaction experiments, the relationship curves between the number of compaction passes and the degree of compaction obtained by a 20-ton vibratory roller are shown in Table 7. Figure 3 As shown in the figure. Experimental results indicate that four passes of compaction are sufficient to meet the required compaction degree.

[0063] Table 7 Relationship between compaction degree and number of compaction passes

[0064] 2. Resilient modulus of the top surface of manganese slag roadbed The resilient modulus of the subgrade top surface represents the stiffness and strength of the subgrade; a higher resilient modulus indicates better bearing capacity. It is an important parameter for the design of the pavement structure when manganese slag is used as the subgrade filler. The resilient modulus of the formed manganese slag embankment was tested in-situ using a bearing plate test according to the "Specifications for Field Testing of Highway Subgrade and Pavement" (JTG 3450-2019). The results of the bearing plate test are shown in Table 8. Figure 4 As shown.

[0065] Table 8 Calculation Table of On-site Load-bearing Plate Test Record

[0066] According to the table, the total elastic deformation at the measuring point is 78.5 (1 / 100mm), and the calculated resilient modulus E0 of the manganese slag subgrade is 76MPa.

[0067] 3. Post-construction settlement monitoring of manganese slag subgrade: Post-construction settlement monitoring began immediately after the final compaction of the manganese slag subgrade. The settlement monitoring results at the two monitoring points after completion are shown in Table 9 and... Figure 5 As shown in the figure. Although the observation period was short, the results still showed that the manganese slag roadbed had small post-construction settlement and fast convergence, completing settlement in a short time.

[0068] Table 9 Post-construction settlement observation records of manganese slag subgrade

[0069] 4. Stress observation To investigate the vertical and lateral stress variation patterns of the manganese slag embankment, four sets of vibrating wire pressure cells were installed across two cross-sections according to the stress monitoring design scheme. Data was transmitted remotely in real time. The amplitude (effective portion) of the vibrating wire stress variation of each pressure cell after completion is shown in Tables 10 and 11. Figures 6-9 As shown in the figure, the larger the absolute value of the amplitude change in the table, the greater the stress increase.

[0070] The results show that the vertical and lateral stresses of the manganese slag embankment are basically consistent with those of conventional soil subgrades, with vertical stress increasing with depth and lateral stress decreasing with depth. The subgrade stability of the experimental road meets expectations. During the observation period, the stress values ​​changed significantly within 1-2 days after completion, while the climate remained relatively stable.

[0071] Table 10 Record of Monitoring Data (Vibrating Wire Amplitude) for Pressure Cell at Section 1#

[0072] Table 11 Record of Monitoring Data (Vibrating Wire Amplitude) for Pressure Cell at Section 2#

[0073] In summary, manganese slag mixtures exhibit excellent compaction properties, meeting specifications only after four passes of compaction. The compaction effect is significant; when using a 20-ton vibratory roller, the degree of compaction increases rapidly with the number of passes. The optimal number of passes (four) was determined, avoiding material damage caused by over-compaction. This improves construction efficiency, reduces machinery operating costs, and provides a scientific basis for standardized construction.

[0074] This invention exhibits excellent mechanical properties and outstanding load-bearing capacity. The resilient modulus of the manganese slag subgrade reaches 76 MPa, demonstrating superior load-bearing capacity. It ensures sufficient stiffness and strength of the subgrade, which is beneficial for reducing the thickness of the pavement structural layer, thereby improving road service life and durability, and providing technical support for the application of high-grade highways.

[0075] This invention demonstrates stable post-construction settlement and reliable long-term performance. The manganese slag subgrade exhibits minimal post-construction settlement, rapid convergence, and excellent stability. The post-construction settlement is significantly less than the allowable value specified in the standards, shortening the natural settlement period of the subgrade. This facilitates faster subsequent pavement construction and reduces later maintenance costs.

[0076] The present invention has a reasonable stress distribution, good structural stability, and the stress distribution of the manganese slag embankment is normal and consistent with that of traditional soil roadbed.

[0077] The construction process of an electrolytic manganese slag embankment provided by this invention has been described in detail above. Specific examples have been used to illustrate the structure and working principle of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A construction process of an electrolytic manganese residue embankment, characterized in that, The method comprises the following steps: Step 1: mixing raw-state electrolytic manganese residue with stabilizing solidification material, auxiliary material and water in a predetermined ratio in a factory to form a harmless manganese residue mixture meeting environmental protection indexes and road performance indexes; Step 2: transporting the harmless manganese residue mixture to a construction site to perform paving, leveling and rolling to form a main body of the embankment; Step 3: arranging a soil edge protection slope on both sides of the main body of the embankment, arranging an isolation layer at the bottom and arranging a capping layer at the top, and arranging a drainage system in cooperation; wherein the width of the soil edge protection slope is not less than 2 meters, and plastic clay with a plasticity index not less than 7 is used; the isolation layer is made of natural gravel, broken block stone or environment-friendly industrial waste residue, the maximum particle size is not more than 8 cm, the content of fine material below 5 mm is ≤30%, and the content of mud is <5%; the capping layer is made of dense clay or dense integral material, and the thickness is not less than 25 cm.

2. The process for constructing an electrolytic manganese residue embankment according to claim 1, characterized in that, The stabilizing solidification material comprises quicklime, cement, fly ash and trisodium phosphate, and the soluble manganese and ammonia nitrogen in the manganese residue are solidified through the synergistic effect of chemical stabilization and physical wrapping.

3. The construction process of the electrolytic manganese residue embankment according to claim 2, characterized in that, The quicklime is calcareous quicklime, the content of calcium oxide is ≥90%, and the activity degree is ≥80%; the effective ingredient of the trisodium phosphate is ≥98%; the fly ash meets the technical index requirements of grade II fly ash in GB1596-91; and the cement meets the requirements of GB 175-2007.

4. The process for constructing an electrolytic manganese residue embankment according to claim 1, characterized in that, The auxiliary material is coarse crushed stone rolled from hard or medium-hard rock or coarse-grained coverstone with a mud content <5%, the maximum particle size of the aggregate is <100 mm, and the part of the aggregate with a particle size less than 4.75 mm is screened out, and the addition amount of the auxiliary material accounts for 10%-30% of the total mass of the harmless manganese residue mixture.

5. The process for constructing an electrolytic manganese residue embankment according to claim 1, characterized in that, The production of the harmless manganese residue mixture uses a special gap type mixing device, and the mixed material needs to be placed for more than 24 hours after mixing to make ammonia gas fully escape, and the water content of the mixed material when leaving the factory is controlled to be 2%-3% higher than the optimal water content.

6. The process for constructing an electrolytic manganese residue embankment according to claim 1, characterized in that, The paving uses horizontal layered filling method, the loose paving coefficient is 1.2-1.3, and the compaction thickness is not more than 30 cm.

7. The process as claimed in claim 1, wherein the electrolytic manganese residue embankment is constructed by the steps of: The forming and compaction process meets the following requirements: a vibration roller with a weight of 20-30 tons is used for rolling; the rolling times are not less than 4; the rolling path follows the principle of rolling the two sides first and then the middle; for curved sections, rolling is performed from the inside to the outside; adjacent wheel traces overlap by 1 / 3 of the wheel width; the rolling speed is controlled to be 35-40 m / min; for local areas that cannot be effectively rolled by the roller, a small vibration tamper is used for supplementary compaction. The rolling uses a vibration roller with a weight of 20-30 tons, and the rolling times are not less than 4.

8. The process for construction of electrolytic manganese residue embankment as claimed in claim 1 wherein, The transportation of the harmless manganese residue mixture meets the following requirements: a vehicle with a single vehicle carrying capacity not less than 20 tons and a complete carriage is used for transportation, a rainproof cloth that can cover all the materials, prevent rain and prevent ammonia gas from escaping is used for sealing and covering the carriage throughout the whole process; the remaining material transported to the site must be transported back to the treatment station, and random dumping is prohibited.

9. The process for construction of electrolytic manganese residue embankment as claimed in claim 1 wherein, At the contact position of the embankment and the bridge and culvert structure, asphalt is brushed for corrosion prevention treatment.

10. The process for construction of electrolytic manganese residue embankment as claimed in claim 1 wherein, The following quality control procedures are performed during the construction process: 1) raw material quality inspection is performed on the incoming quicklime, fly ash, auxiliary material, cement and trisodium phosphate according to predetermined inspection items and frequency; 2) For each production batch of harmless manganese slag mixture, sampling is carried out according to the frequency specified in the "Industrial Solid Waste Sampling and Sample Preparation Technical Specification" (HJ / T 20-1998), and the concentrations of manganese and ammonia nitrogen in the leachate are detected to ensure that the limit requirements of the "Integrated Wastewater Discharge Standard" (GB 8978) are met; 3) After the completion of each compacted layer construction, compaction degree detection is carried out at a frequency of 2 points per 200 meters per compacted layer to ensure that the value meets the requirements of the Highway Subgrade Design Specification for the corresponding filling site; 4) After the embankment construction reaches the design elevation, the deflection, longitudinal elevation, centerline deviation, width, flatness, transverse slope, and slope gradient of the embankment are inspected and accepted for the completion quality.

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