Mixed roadbed filler prepared by compounding and cooperating multi-source solid waste material with shield muck

Abstract

The invention discloses a mixed roadbed filler prepared by compounding and cooperating multi-source solid waste materials with shield muck. The mixed roadbed filler is prepared from the following raw materials in parts by mass: 100 parts of shield muck, 3 parts of carbide slag / lime, 0-3 parts of fly ash, 0-3 parts of alkaline residues and 0-3 parts of desulfurized gypsum, according to the mixed roadbed filler, lime / carbide slag is used as a curing agent, fly ash, alkaline residues and desulfurized gypsum are used as additives, and a mixture with good strength and durability is formed after uniform stirring and compaction. The mixed filler is applied to roadbed backfilling, so that the shield muck and bulk solid wastes are recycled, and the mixed filler has important social and economic significance in reducing occupation of scarce land resources caused by industrial waste accumulation, reducing environmental pollution hazards and saving construction cost, and is simple in preparation engineering, easy in raw material obtaining and suitable for large-scale popularization and application. And popularization in engineering practice is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a mixed roadbed filler prepared by compositely combining multi-source solid waste materials with shield slag. Background Art

[0002] With the advancement of urbanization, urban traffic pressure continues to increase. Traditional surface transportation can no longer meet demand, prompting city builders to turn their attention to underground transportation, driving the rapid development of subways. By the end of 2024, 58 cities in my country had subways operating, totaling 12,168.77 kilometers of lines, of which subways accounted for over 76%. Subway construction has effectively alleviated urban traffic pressure and injected momentum into sustainable development. Shield tunneling, as the primary construction method, offers advantages such as high mechanization, safe and reliable construction, and minimal impact, making it widely used in subway tunnel projects. However, this also generates large amounts of waste soil. Traditional methods of external transportation increase project costs and waste soil resources. Especially with the expansion of underground projects, waste soil disposal has become increasingly serious, becoming a pressing urban construction challenge that needs to be addressed.

[0003] Carbide slag is the waste residue produced during the hydrolysis of calcium carbide to produce acetylene. The production of one ton of polyvinyl chloride (PVC) generates approximately 1.5 to 1.9 tons of carbide slag. Currently, carbide slag is primarily disposed of through landfill or stockpiling, with a utilization rate of approximately 40%. Carbide slag is typically gray or white, highly alkaline, and contains certain harmful components. Because its primary components include unreacted calcium carbide, lime, and a small amount of silica, and because it exhibits excellent particle dispersion, large specific surface area, rich pore structure, and rapid dissolution, it offers potential for resource utilization.

[0004] Desulfurization gypsum and fly ash are solid wastes generated during the coal-fired power plant combustion process. Desulfurization gypsum is a byproduct produced by the wet desulfurization process, removing sulfur dioxide from flue gas. Its main component is calcium sulfate. During the pozzolanic reaction, needle-shaped ettringite is produced, which forms a spatial network structure with the cementitious products, improving the strength of the solidified soil. Fly ash is a fine-particle solid waste produced after coal combustion. Its main components are silica, bauxite, etc. Its fine particles have good adsorption and reactivity, which can enhance the material's pozzolanic reactivity.

[0005] Therefore, if an appropriate curing agent ratio can be optimized so that the cured shield excavation soil can meet the requirements of roadbed backfill while also being economically efficient, this would not only achieve the disposal of shield excavation soil, but also realize the resource utilization of large amounts of solid waste. Research on the application of cured shield excavation soil for roadbed backfill has important technical value in reducing environmental pollution, shortening construction costs and project duration, and is of great significance to the healthy development of the economy and society. Summary of the Invention

[0006] This invention addresses the technical deficiencies of existing shield excavation waste disposal problems and the high economic costs required for foundation pit backfill. It provides a roadbed filler made from a composite of multiple solid waste materials and shield excavation waste, addressing the disposal of shield excavation waste and the comprehensive resource utilization of large-scale solid waste. Using the solidified excavation waste as roadbed filler eliminates the cost of transporting the waste and the need for storage space. Furthermore, the solidified excavation waste provides a new avenue for the resource utilization of large-scale solid waste.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A mixed roadbed filler prepared by combining multi-source solid waste materials with shield slag. The raw materials of the mixed roadbed filler prepared by combining multi-source solid waste materials with shield slag are as follows in parts by mass: shield slag, 100 parts; carbide slag / lime, 3 parts; fly ash, 0-3 parts; alkali slag, 0-3 parts; and desulfurization gypsum, 0-3 parts.

[0009] Preferably, the lime is produced by a chemical plant, has the appearance of white powder, and has a CaO content of 93.2%.

[0010] Preferably, the carbide slag is a white powdery material obtained by crushing blocky air-dried carbide slag in a carbide slag yard, and the CaO content is close to 90%.

[0011] Preferably, the fly ash is a by-product of coal combustion in a thermal power plant, and is a gray-black powder. SiO2, Al2O3 and Fe2O3 in the fly ash account for 40.2%, 22.7% and 14.7% respectively.

[0012] Preferably, the desulfurization gypsum is a by-product of the flue gas desulfurization process of a thermal power plant, is a light yellow powder, and has a CaSO4·2H2O content of more than 90%.

[0013] The above-mentioned method for preparing roadbed filler by combining multi-source solid waste materials with shield slag specifically comprises the following steps:

[0014] The first step: prepare materials, including shield slag and the lime / carbide slag, desulfurization gypsum and fly ash curing agent raw materials used. The shield slag is drained and the moisture content of the drained shield slag is determined by drying method; the original carbide slag in the yard is air-dried and crushed with a pulverizer, and passed through a 2mm sieve to obtain carbide slag powder; prepare desulfurization gypsum and fly ash materials of the same specifications as above.

[0015] Step 2: Calculate the mass of water required to be added based on the optimal moisture content obtained from the indoor compaction test and the moisture content of the shield slag.

[0016] Step 3: According to the mass ratio of raw materials in the mixed roadbed filler prepared by the multi-source solid waste and shield slag, weigh 100 parts of shield slag; 3 parts of carbide slag / lime; 0-3 parts of fly ash; 0-3 parts of alkali slag; 0-3 parts of desulfurization gypsum, and then add the required water and mix evenly; the amount of carbide slag, desulfurization gypsum and fly ash can be appropriately adjusted according to the requirements of different highway grades and solid waste storage conditions.

[0017] Step 4: Backfill, compaction, and curing. The resulting mixture is transported to the roadbed construction section for backfilling, rolled until the compaction meets the design specifications, and then cured to obtain the mixed roadbed filler prepared by combining multi-source solid waste with shield slag.

[0018] The present invention uses lime / carbide slag as a curing agent, fly ash, alkali residue and desulfurization gypsum as additives, and forms a mixture with good strength and durability after uniform stirring and compaction; the composition of the mixture is based on the composition properties of the soil, the strength requirements of the finished product and the solid waste storage conditions at the construction site, and the mass proportions of each component material are as follows: soil, 100 parts; carbide slag / lime, 3 parts; fly ash, 0-3 parts; alkali residue, 0-3 parts; desulfurization gypsum, 0-3 parts.

[0019] The principle of the above-mentioned method of preparing roadbed filler using multi-source solid waste and shield muck is:

[0020] The CaO component in carbide slag is similar to lime, and reacts with water in shield tunneling slag to produce Ca(OH)2. Simultaneously, the active SiO2 and Al2O3 in the clay particles react with Ca(OH)2 in a pozzolanic reaction to produce cementitious materials such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH), which in turn cement the soil particles and enhance soil strength. During the reaction, desulfurized gypsum generates needle-rod-shaped calcium aluminoferrite, which forms a spatial network structure with the pozzolanic reaction products and clay particles, further enhancing the strength of the solidified soil. Fly ash provides additional active SiO2 and Al2O3, providing raw materials for the pozzolanic reaction. These cementitious materials are hydraulically hardened and can harden in a water environment, reducing soil permeability, forming a dense structure, and enhancing soil strength and stability.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The mixed roadbed filler prepared by combining multi-source solid waste with shield slag reduces the land resources occupied by the stacking of shield slag and the cost of transportation. At the same time, the improved shield slag backfill replaces the traditional backfill materials (sand, gravel), reducing the consumption of natural resources and having important social value and economic benefits.

[0023] 2. The mixed roadbed filler prepared by the collaborative shield slag of multi-source solid waste comprehensively utilizes carbide slag, desulfurization gypsum and fly ash waste, and solidifies the harmful components that may exist therein by physical adsorption and chemical reaction to solidify metal ions. At the same time, by adding carbide slag, desulfurization gypsum and fly ash, the use of traditional lime is reduced, which has both economic and environmental benefits.

[0024] 3. The preparation process of the multi-source solid waste cooperative shield slag roadbed filler of the present invention is simple and will not increase the technical difficulty of on-site construction.

[0025] 4. The mixed roadbed filler prepared by the present invention using multi-source solid waste and shield slag can achieve a CBR of 66.6%-148.7% under standard maintenance, which fully meets the CBR requirements of roadbed filling; at the same time, the water stability coefficient of the 7d and 28d samples was analyzed through unconfined compressive strength tests, and it was shown that the mixed roadbed filler using multi-source solid waste and solidified shield slag has good water resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The mechanical strength properties of the mixed roadbed filler prepared by combining multi-source solid waste with shield slag in the examples.

[0027] Figure 2 This is the water stability of the mixed roadbed filler prepared by combining multi-source solid waste with shield tunneling debris in the examples. DETAILED DESCRIPTION

[0028] In order to make the technical problems, embodiments and advantages of the present invention clearer, the following will be described in detail with reference to specific examples. It should be noted that the examples are only preferred embodiments of the present invention and do not limit the scope of protection of the present invention. Without departing from the principles of the present invention, improvements and optimizations can be made, and these improvements and optimizations are also included in the scope of protection of the present invention.

[0029] The raw materials used in the examples, unless otherwise specified, are common building materials available on the market.

[0030] Example 1

[0031] A mixed roadbed filler prepared by combining multi-source solid waste materials with shield slag. The components of the mixed roadbed filler prepared by combining multi-source solid waste materials with shield slag are proportioned as follows by mass: shield slag, 100 parts; carbide slag / lime, 3 parts; fly ash, 0-3 parts; alkali slag, 0-3 parts; and desulfurization gypsum, 0-3 parts.

[0032] The engineering slag soil excavated from a foundation pit of a project in Nanjing Southern New City has a liquid limit of 44.8% and a plastic limit of 21.4%, which is classified as clay. The maximum dry density obtained through indoor compaction tests is 1.72g / cm3 , the optimal moisture content is 16.88%.

[0033] Preferably, the lime is produced by a chemical plant, has the appearance of white powder, and has a CaO content of 93.2%.

[0034] Preferably, the carbide slag is a white powdery material obtained by crushing blocky air-dried carbide slag in a carbide slag yard, and the CaO content is close to 90%.

[0035] Preferably, the fly ash is a by-product of coal combustion in a thermal power plant, and is a gray-black powder. SiO2, Al2O3 and Fe2O3 in the fly ash account for 40.2%, 22.7% and 14.7% respectively.

[0036] Preferably, the desulfurization gypsum is a by-product of the flue gas desulfurization process of a thermal power plant, is a light yellow powder, and has a CaSO4·2H2O content of more than 90%.

[0037] This example analyzes the mechanical strength properties of the mixed roadbed filler prepared by multi-source solid waste and shield slag through a bearing ratio (CBR) test, and tests and analyzes the water stability of the mixed roadbed filler prepared by multi-source solid waste and shield slag through the change in the unconfined compressive strength of the samples before and after immersion in water.

[0038] The method for preparing roadbed filler using multi-source solid waste and shield slag specifically comprises the following steps:

[0039] The first step: prepare materials, including shield slag and the lime / carbide slag, desulfurization gypsum and fly ash curing agent raw materials used. The shield slag is drained and the moisture content of the shield slag after drying is determined by drying method; the original carbide slag in the yard is air-dried and crushed with a pulverizer, and passed through a 2mm sieve to obtain carbide slag powder; prepare desulfurization gypsum and fly ash materials of the same specifications as above.

[0040] Step 2: Calculate the mass of water required to be added based on the optimal moisture content obtained from the indoor compaction test and the moisture content of the slag.

[0041] Step 3: According to the mass proportion of the raw materials in the mixed roadbed filler prepared by combining multi-source solid waste with shield slag, weigh 100 parts of shield slag, 3 parts of lime, and 3 parts of fly ash. Then add the required water and mix well.

[0042] Step 4: Backfill, compaction, and curing. The resulting mixture is transported to the roadbed construction section for backfilling, rolled until the compaction meets the design specifications, and then cured to obtain the multi-source solid waste synergistically solidified shield slag mixed roadbed filling material.

[0043] Sample preparation: According to the method specified in the Highway Geotechnical Test Code (JTG 3430-2020), a sample with an inner diameter of 152 mm, a height of 170 mm, and a volume of 2177 cm 3 The compaction cylinder was used and specimens were prepared using the heavy-duty II-2 compaction test method, with three replicates prepared for each group. After installing the porous plate, filter paper, spacer, and base plate, the specimen was placed in a water tank and fitted with a dial indicator. The initial reading was recorded. Water was slowly added until the water level was approximately 25 mm above the top of the compaction cylinder. After soaking for four days and nights, the dial indicator reading was read again. The CBR value of the specimen was then measured through a penetration test. Water stability was assessed using unconfined compressive strength tests before and after immersion. 5 cm × 5 cm specimens were prepared using a casting mold at a compaction degree of 96%. After demolding, they were placed in ziplock bags and cured in a standard curing room (20°C ± 2°C, humidity ≥ 95%). The specimens were removed from the water one day before the age and immersed for 24 hours before being subjected to unconfined compressive tests against unimmersed specimens. The unconfined compressive strength values of the solidified soil were measured before and after immersion, with a loading rate of 1 mm / min.

[0044] Table 1 Experimental data of mixed roadbed filler prepared by multi-source solid waste and shield slag in Example 1

[0045]

[0046] Example 2

[0047] A mixed roadbed filler prepared by compositely combining multi-source solid waste materials and shield slag is prepared by a method substantially the same as that in Example 1, except that the raw materials are proportioned as follows by mass: shield slag, 100 parts; lime, 3 parts; and alkali residue, 3 parts.

[0048] Table 2 Experimental data of mixed roadbed filler prepared by multi-source solid waste and shield slag in Example 2

[0049]

[0050] Example 3

[0051] A mixed roadbed filler prepared by compositely combining multi-source solid waste materials and shield slag has a preparation method substantially the same as that in Example 1, except that the raw materials are proportioned as follows by mass: shield slag, 100 parts; lime, 3 parts; desulfurized gypsum, 3 parts.

[0052] Table 3 Experimental data of mixed roadbed filler prepared by multi-source solid waste and shield slag in Example 3

[0053]

[0054] Example 4

[0055] A mixed roadbed filler prepared by compositely combining multi-source solid waste materials and shield slag, the preparation method of which is roughly the same as that of Example 1, except that the raw materials are proportioned in parts by mass as follows: shield slag, 100 parts; carbide slag, 3 parts; alkali slag, 3 parts; desulfurization gypsum, 3 parts.

[0056] Table 4 Experimental data of mixed roadbed filler prepared by multi-source solid waste and shield slag in Example 4

[0057]

[0058] Comparative Example 1

[0059] A mixed roadbed filler prepared by compositely combining multi-source solid waste materials and shield slag is prepared by a method substantially the same as that in Example 1, except that the raw materials are proportioned as follows by mass: shield slag, 100 parts; lime, 3 parts.

[0060] Table 5 Comparative Example 1 Test data of mixed roadbed filler prepared by multi-source solid waste and shield slag

[0061]

[0062] Comparative Example 2

[0063] A mixed roadbed filler prepared by combining multi-source solid waste materials with shield slag has a preparation method that is roughly the same as that in Example 1, except that the raw materials are proportioned in parts by mass as follows: shield slag, 100 parts; carbide slag, 3 parts; fly ash, 3 parts.

[0064] Table 6 Comparative Example 2 Test data of mixed roadbed filler prepared by multi-source solid waste and shield slag

[0065]

[0066] Comparative Example 3

[0067] A mixed roadbed filler prepared by compositely combining multi-source solid waste materials and shield slag has a preparation method that is roughly the same as that in Example 1, except that the raw materials are proportioned in parts by mass as follows: shield slag, 100 parts; lime, 3 parts; alkali slag, 3 parts; and desulfurized gypsum, 3 parts.

[0068] Table 7 Comparative Example 3 Test data of mixed roadbed filler prepared by multi-source solid waste and shield slag

[0069]

[0070] According to the given test data, the performance of the mixed roadbed fillers prepared by the cooperation of multi-source solid waste and shield slag in different embodiments and comparison groups was analyzed, and the comparison and analysis were mainly carried out from the aspects of bearing ratio, unconfined compressive strength and water stability coefficient. The bearing ratio (CBR value) is an important indicator to measure the strength of roadbed fillers. It can be concluded from Table 1-4 that the bearing ratios of Examples 1-4 range from 66.6% to 137.4%. The bearing ratios of the mixed roadbed fillers prepared by the cooperation of multi-source solid waste and shield slag can fully meet the 8% requirement of the highway roadbed. Compared with Comparative Example 1, after the addition of fly ash, alkali slag and desulfurization gypsum, especially the addition of alkali slag and desulfurization gypsum, Examples 1-3 significantly improved the bearing ratio, all of which increased by more than 20%. This is because in the early stage of curing, the high alkalinity of the alkali residue prompts the reaction to proceed rapidly. Under the action of lime hydration and alkali residue, the soil aggregates to form a skeleton, adsorbing the surrounding small particles to form a larger gel group, which plays the role of a skeleton. Although the increase in water stability is small, it can effectively improve the strength; and the desulfurization gypsum contains a large amount of calcium sulfate. In the early stage of the reaction, a large amount of calcium sulfate quickly combines with the volcanic ash reaction product to form calcium aluminate, filling the gaps between soil particles, improving the strength of the soil and significantly increasing the water stability. With the increase of age, the reaction gradually stabilizes, and the later strength increase of the two is small. The addition of fly ash in Example 1 significantly improves the later strength through the action of activated alumina and silica.

[0071] Compared with Comparative Example 2, carbide slag can improve the reactivity of volcanic ash in the early reaction, so that the unconfined compressive strength at the age of 7 days develops faster and is not much different from the lime group in Example 1, but the water stability of the solidified soil is slightly weaker. At the same time, due to the difference between carbide slag and lime in overall active ingredients, this group is not as good as the lime group in the later 28-day strength, and the increase in bearing ratio is also lower than that in Example 1. For Example 3 and Comparative Example 1, after replacing lime with carbide slag, although the bearing ratio of the solidified soil decreased, under the joint action of alkali slag and desulfurization gypsum, the early and late unconfined compressive strength and water stability of the sample are not much different. This shows that the components in the mixed roadbed filler prepared by multi-source solid waste and shield slag have good compatibility, good synergy, give full play to their respective characteristics, and have a theoretical basis for practical application.

[0072] The mixed roadbed filler prepared by combining multi-source solid waste with shield slag and the preparation method thereof provided by the above-mentioned embodiment of the present invention is characterized in that it has significant advantages in material selection and proportion design. Calcium carbide slag has the potential to replace lime as a solidified roadbed, and through reasonable proportion selection, especially after adding industrial solid wastes such as desulfurization gypsum and alkali slag, it can significantly improve the mechanical properties and water stability of shield slag. This not only provides a new idea for the resource utilization of shield slag, but also provides an efficient and environmentally friendly filler option for roadbed construction, and the requirements for the solid waste used are not high, and it is entirely possible to select solid waste with a large local stockpile according to local conditions.

[0073] The above description is only for the purpose of illustrating preferred embodiments of the present invention and is not intended to limit the scope of the present invention. Those skilled in the art may make various changes, modifications or substitutions based on the principles of the present invention, which should all be included in the scope of protection of the present invention.

Claims

1. A mixed roadbed filler prepared by combining multi-source solid waste materials with shield slag, characterized in that: The raw materials include, by mass: 100 parts of shield slag, 3 parts of carbide slag / lime, 0-3 parts of fly ash, 0-3 parts of alkali slag, and 0-3 parts of desulfurization gypsum.

2. The mixed roadbed filler according to claim 1, characterized in that: The CaO content in the carbide slag and lime is not less than 90%.

3. The mixed roadbed filler according to claim 1, characterized in that The proportions of SiO2, Al2O3 and Fe2O3 in the fly ash are 38-42%, 20-24% and 12-16% respectively.

4. The mixed roadbed filler according to claim 1, characterized in that: The content of CaSO4•2H2O in the desulfurization gypsum is above 90%.

5. The method for preparing the mixed roadbed filler according to any one of claims 1 to 4, characterized in that: The following steps are involved: The first step is to drain the shield slag and determine the moisture content of the shield slag after drying by a drying method; the original carbide slag in the yard is air-dried and then crushed by a pulverizer, and passed through a 2mm sieve to obtain carbide slag powder; Step 2: Calculate the mass of water to be added based on the optimal moisture content obtained from the compaction test and the moisture content of the shield muck; Step 3: Weigh the raw materials according to mass and mix them evenly; Step 4: Transport the obtained mixture to the roadbed construction section for backfilling, and then roll it until the compaction degree meets the design specifications and then carry out maintenance.

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