Controllable low-strength backfill material using construction waste and modified shield muck and preparation method thereof

Abstract

The application discloses a controllable low-strength backfill material using construction waste and modified shield muck, and a preparation method thereof, and belongs to the technical field of resource utilization of construction engineering waste.The shield muck is used as a main raw material, and a certain amount of shield muck is replaced by construction waste to optimize the working performance of the controllable low-strength material.After the ratio of the shield muck and the construction waste is determined, the dosages of industrial waste residue, cement, water and solid water glass are determined;by controlling the addition amount of the industrial waste residue and the solid water glass, the synergistic effect among the materials is achieved, and the synergistic improvement of the mechanical properties and the synergistic optimization of the working performance of the controllable low-strength backfill material are realized.

Description

Technical Field

[0001] This invention belongs to the field of resource utilization technology of construction waste, and in particular relates to a controllable low-strength backfill material and its preparation method that utilizes construction waste in conjunction with the modification of shield tunnel slag. Background Technology

[0002] Currently, the technology level and scale of the industry for handling construction waste and tunnel boring machine excavation are relatively low. Most waste is disposed of through stockpiling and landfilling, with only a small portion being screened and used as grouting material for concrete. This massive stockpiling wastes urban development space and poses a significant challenge to environmental protection. How to effectively treat and utilize this waste is an urgent problem that needs to be solved, and it is of great significance for promoting resource reuse and sustainable development.

[0003] Controllable low-strength materials are cement-based low-strength backfill materials that can replace traditional backfill materials. These materials possess high fluidity and, under their own weight, can self-fill with minimal or no vibration, forming a self-compacting structure. Traditional controllable low-strength materials typically consist of cement, fine aggregates such as sand, coarse aggregates such as gravel, water-reducing agents, admixtures, and water, resulting in poor economic and environmental benefits. The extensive use of cement has adverse environmental impacts. Tunnel boring machine (TBM) slag can replace fine aggregates such as sand, construction waste can replace coarse aggregates such as gravel, and industrial waste further effectively reduces cement usage.

[0004] Currently, there is research on controllable low-strength backfill materials in the industry. However, the preparation process relies solely on shield tunneling slurry, leading to problems such as high bleeding rates and insufficient strength, failing to meet construction requirements. Construction waste itself has good water absorption properties. Adding an appropriate amount of construction waste during the preparation of controllable low-strength backfill materials can significantly reduce the bleeding rate and effectively improve the strength of the material. It also plays a positive role in solving the problem of excessively long setting time. However, existing technologies have not explored how to control the proportions of shield tunneling slag and construction waste with other components to obtain controllable low-strength backfill materials with excellent mechanical properties. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a controllable low-strength backfill material and its preparation method that utilizes construction waste in conjunction with the modification of tunnel boring machine slag.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a controllable low-strength backfill material that utilizes construction waste in conjunction with the modification of tunnel boring machine (TBM) slag. The raw materials include construction waste, TBM slag, industrial waste, cement, water, and a modified water glass solution. The mass fractions of each component are related as follows:

[0008] Construction waste (χ parts);

[0009] Shield tunneling excavation soil (1-2.38) × χ parts;

[0010] 0.3 × {(1~2.38) × χ + χ} parts of industrial waste residue;

[0011] 0.03 × {(1~2.38) × χ + χ} parts of cement;

[0012] Water 0.35 × {1.33 × (1~2.38) × χ + χ} parts;

[0013] The modified water glass solution contains 0.0125 × {(1~2.38) × χ + χ} parts of solid water glass.

[0014] Technical Principle: This invention uses tunnel boring machine (TBM) slag as the main raw material, while replacing a certain amount of TBM slag with construction waste to optimize the performance of controllable low-strength materials. After determining the ratio of TBM slag and construction waste, the amounts of industrial waste, cement, water, and solid water glass are then determined. By controlling the addition of industrial waste and solid water glass, a synergistic effect among the materials is achieved, resulting in a synergistic improvement in the mechanical properties and a synergistic optimization in the performance of the controllable low-strength backfill material.

[0015] Furthermore, the industrial waste residue is composed of mineral powder and fly ash; the mass ratio of the mineral powder to fly ash is 9:(5-12).

[0016] Furthermore, the modulus of the modified water glass solution is 0.8 to 1.4.

[0017] This invention also provides a method for preparing a controllable low-strength backfill material using construction waste and shield tunneling slag modification as described in the above technical solution, comprising the following steps:

[0018] (1) The raw materials used to prepare controllable low-strength backfill material are pre-proportioned in terms of mass; the average specific surface area of ​​construction waste and shield tunnel slag is measured respectively, the specific surface area coefficient is obtained based on the average specific surface area of ​​construction waste and shield tunnel slag, the catalytic influence coefficient is determined based on the specific surface area coefficient, and the mass proportion of construction waste and shield tunnel slag is adjusted once based on the catalytic influence coefficient to determine the basic aggregate proportion; the basic aggregate is construction waste and shield tunnel slag;

[0019] (2) Based on the basic aggregate ratio and the preset mass ratio of other raw materials besides the basic aggregate in step (1), prepare controllable low-strength backfill material; test the fluidity change rate of the prepared controllable low-strength backfill material, determine the fluidity characteristic influence coefficient based on the fluidity change rate, and adjust the mass ratio of construction waste and shield tunnel slag based on the fluidity characteristic influence coefficient to determine the final basic aggregate ratio;

[0020] (3) Determine the amount of industrial waste, cement and water based on the amount of construction waste, the mass ratio of industrial waste to basic aggregate, the mass ratio of cement to industrial waste, and the water-solid ratio; wherein, the amount of industrial waste is the total amount of mineral powder and fly ash.

[0021] The chemical composition of the shield tunnel slag, mineral powder and fly ash used was determined. Based on the preset mass ratio of mineral powder and fly ash, the silica ratio and calcium oxide ratio of the controllable low-strength backfill material were calculated. Based on the obtained silica ratio and calcium oxide ratio, the ratio of mineral powder and fly ash was determined.

[0022] Determine the amount of solid water glass to be used, and adjust the modulus of the solid water glass using NaOH to obtain a modified water glass solution;

[0023] (4) Weigh each raw material according to the amount of raw materials determined in step (3). First, mix the construction waste, shield tunnel slag, industrial waste and cement and then pre-stir. Then add water for basic stirring. After stirring for 10-15 minutes, add modified water glass solution and continue stirring for 5-10 minutes. After curing, the controllable low-strength backfill material modified by construction waste and shield tunnel slag is obtained.

[0024] Furthermore, in step (1), before determining the average specific surface area of ​​the construction waste, the steps of removing impurities, crushing, grinding, and sieving the construction waste are also included. This invention removes plastics and other lightweight organic materials from the construction waste through impurity removal. By crushing, grinding, and sieving the construction waste, under mechanical force, its specific surface area and particle morphology exhibit a high degree of consistency, and the particle size distribution has good gradation characteristics. This produces usable fine aggregate, which can more effectively control the setting time, flowability, compressive strength, and other mechanical and workability properties of controllable low-strength backfill materials.

[0025] Furthermore, the crushing equipment is one of a jaw crusher, a cone crusher, or a hammer crusher; the grinding equipment is one of a Raymond mill, a ball mill, or a cone ball mill; and the particle size of the construction waste after screening is ≤4.5mm.

[0026] Furthermore, in step (1), before determining the average specific surface area of ​​the shield tunneling slag, the shield tunneling slag is subjected to a water-drying treatment and sieving.

[0027] Furthermore, the moisture content of the shield tunneling slag after the dewatering and drying treatment is <10%, and the particle size of the shield tunneling slag after screening is ≤9.5mm.

[0028] Furthermore, in step (1), specific surface area refers to the total area per unit mass of material, which affects the catalytic efficiency of the alkali activator. Specific surface area can be measured by a specific surface area meter, and each raw material needs to be measured at least three times and the average value is taken.

[0029] Further, in step (1), the formula for calculating the specific surface area coefficient is: R s =0.05×S cw / S sr Among them, R s S represents the specific surface area coefficient. cw S represents the average specific surface area of ​​construction waste. sr This represents the average specific surface area of ​​the tunnel boring machine excavation soil.

[0030] Furthermore, based on extensive practical experience, S sr <S cw .

[0031] Further, in step (1), determining the catalytic influence coefficient based on the specific surface area coefficient specifically means: if the specific surface area coefficient R s ≤Preset mass ratio Right now Then the catalytic effect coefficient α = 1; if the specific surface area coefficient R s >Preset mass ratio Right now Therefore, the catalytic effect coefficient is 1.05≤α≤1.15.

[0032] Furthermore, the preset mass ratio value The calculation formula is: Among them, QC cw This indicates the pre-set quality of construction waste, or QC. sr This indicates the preset mass of the tunnel boring machine excavation.

[0033] Furthermore, the preset mass ratio value The value is

[0034] Furthermore, in step (1), the basic aggregate proportioning... The calculation formula is: Where α represents the catalytic effect coefficient, This indicates the preset mass ratio.

[0035] Furthermore, in step (2), the specific change rate of the flowability of the prepared controllable low-strength backfill material is as follows:

[0036] According to the preset mass ratio of each raw material determined in step (1), controllable low-strength backfill material is prepared to obtain slurry one;

[0037] According to the basic aggregate ratio obtained in step (1) and the preset mass ratio of other raw materials, controllable low-strength backfill material is prepared to obtain slurry II;

[0038] The flowability of slurry one and slurry two at time 0 and time t were measured respectively, and the flowability change rate was obtained based on the flowability of slurry one and slurry two.

[0039] Furthermore, the flowability testing steps include:

[0040] Prepare the testing equipment: a clean and slightly damp plastic cylinder and a plastic plate. Place the plastic cylinder in the center of the plastic plate.

[0041] Pour the prepared slurry into the plastic cylinder, gently tap the container to eliminate gaps between the slurries, and use a scraper to smooth out any overflowing slurry, ensuring that the slurry fills the entire plastic cylinder.

[0042] Slowly raise the plastic cylinder to allow the slurry to spread evenly on the plastic plate. Use a steel ruler to measure the diameter of the spread circle twice in the vertical direction and take the average of the two measurements as the flowability f.

[0043] Furthermore, the formula for calculating the flowability change rate V is: Where f0 represents the fluidity of the slurry at time 0, f t This indicates the fluidity of the slurry at time t, which is usually taken as 10 to 20 minutes.

[0044] Further, in step (2), the determination of the flow characteristic influence coefficient based on the fluidity change rate is specifically as follows: if the fluidity change rate V2 of slurry 2 is greater than the fluidity change rate V1 of slurry 1, that is, V2 > V1, then the flow characteristic influence coefficient β = 1; if the fluidity change rate V2 of slurry 2 is less than the fluidity change rate V1 of slurry 1, that is, V2 < V1, then the flow characteristic influence coefficient 1.1 ≤ β ≤ 1.2.

[0045] Furthermore, in step (2), the final proportion of the basic aggregate is... The calculation formula is: Where β represents the flow characteristic influence coefficient. This indicates the basic aggregate mix ratio.

[0046] Further, in step (3), the determination of the chemical composition of the shield tunnel slag, mineral powder, and fly ash used specifically involves determining the total mass fraction of SiO2, Al2O3, Fe2O3, and CaO in the shield tunnel slag, mineral powder, and fly ash used. W CaO .

[0047] Further, in step (3), the formula for calculating the silica ratio SR is:

[0048] Further, in step (3), the formula for calculating the calcium oxide ratio LR is:

[0049] Further, in step (3), the determination of the ratio of mineral powder and fly ash based on the obtained silica ratio and calcium oxide ratio is specifically as follows: if the silica ratio SR and the calcium oxide ratio LR satisfy 2.97≤SR≤3.65 and 0.21≤LR≤0.33, then there is no need to adjust the mass ratio of mineral powder and fly ash; if the above value range is not met, then the mass ratio of mineral powder and fly ash needs to be further adjusted so that the alkali activator can play an effective role.

[0050] Furthermore, if the calculated SR is too large, reduce the amount of fly ash; if it is too small, increase the amount of fly ash. If the calculated LR is too large, reduce the amount of mineral powder; if it is too small, increase the amount of mineral powder. If both the calculated SR and LR are too large, reduce the amount of fly ash; if both are too small, increase the amount of fly ash.

[0051] Further, in step (3), the preparation method of the modified water glass solution is as follows: solid water glass and hot water are mixed at a mass ratio of 1:2 to fully dissolve the solid water glass, and solid NaOH is added after cooling to adjust the modulus; the solid water glass is a solid white powder with a modulus of 3.4.

[0052] Furthermore, the chemical formula of the solid water glass is Na2O·mSiO2·nH2O, where m represents the modulus of the water glass.

[0053] Furthermore, the formula for calculating the modulus m of the modified water glass solution is:

[0054] Furthermore, the solid NaOH is analytical grade, with a purity ≥96%, and is a white solid granular form.

[0055] Furthermore, in step (3), the mass ratio of industrial waste residue to basic aggregate is 0.3:1; the mass ratio of cement to industrial waste residue is 0.1:1; the water-to-solid ratio is 0.35; and the mass ratio of solid water glass to basic aggregate is 0.0125:1.

[0056] Furthermore, in step (4), the curing temperature is 21-25℃, the relative humidity is >95%, and the time is 24-72h.

[0057] Compared with the prior art, the present invention has the following advantages and technical effects:

[0058] (1) This invention utilizes construction waste to prepare fine aggregates and uses industrial waste such as mineral powder and fly ash as alkali catalysts, which greatly reduces the amount of cement used and realizes the reuse of waste resources. It is of great significance to promote resource reuse and sustainable development, and has great environmental value and economic benefits.

[0059] (2) This invention determines the basic aggregate ratio based on the specific surface area of ​​shield tunneling slag, the specific surface area of ​​construction waste, and the rate of change in fluidity. It calculates the silica ratio and calcium oxide ratio by measuring the chemical composition of shield tunneling slag and industrial waste, thereby determining the mass ratio of mineral powder and fly ash. Based on the differences in the components during each preparation and the varying requirements of the construction site, the mix proportions are systematically adjusted to meet the required mechanical and workability properties. This ensures that the controllable low-strength backfill material fully utilizes the performance advantages of each material and meets the requirements of on-site construction. Attached Figure Description

[0060] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0061] Figure 1 This is a process flow diagram of the preparation method of controllable low-strength backfill material using construction waste and shield tunnel slag modification in Embodiments 1-3 of the present invention;

[0062] Figure 2 This is a process flow diagram of step (2) in embodiments 1-3 of the present invention;

[0063] Figure 3 This is a process flow diagram of step (3) in Embodiments 1-3 of the present invention;

[0064] Figure 4 This is a process flow diagram of determining the ratio of mineral powder and fly ash in step (4) of embodiment 1-3 of the present invention. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] In this embodiment of the invention, room temperature refers to "23±2℃".

[0068] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0069] Example 1

[0070] A method for preparing a controllable low-strength backfill material utilizing construction waste and shield tunneling slag modification, comprising the following steps:

[0071] (1) Remove impurities from existing construction waste materials, such as plastics and other organic lightweight materials, crush them with a jaw crusher, grind them with a Raymond mill, and then screen them to obtain construction waste materials with a particle size ≤ 4.5 mm; dry the existing shield tunnel slag with water until the moisture content is less than 10%, and then screen it to obtain shield tunnel slag with a particle size ≤ 9.5 mm.

[0072] (2) The raw materials used to prepare controllable low-strength backfill material are pre-proportioned: construction waste x parts, shield tunnel slag x parts, industrial waste 0.6 x parts, cement 0.06 x parts, water 0.8155 x parts, solid water glass in modified water glass solution 0.025 x parts, the mass ratio of mineral powder and fly ash in industrial waste slag is 9:8.06, and the modulus of modified water glass solution is 1.2; the average specific surface area S of construction waste in step (1) is determined. cw 374m 2 / kg, determine the average specific surface area S of the shield tunneling debris in step (1). sr It is 19.4m 2 / kg, R is obtained according to the formula for calculating the specific surface area coefficient. s =0.05×S cw / S sr =0.964;

[0073] Based on the pre-set quality control of construction waste cw Preset quality QC for tunnel excavation sr The ratio value is used to obtain the preset mass ratio value. Specific surface area coefficient R s <Preset mass ratio value The catalytic effect coefficient α is determined to be 1;

[0074] The basic aggregate mix ratio is determined by adjusting the mass ratio of construction waste and tunnel boring machine slag based on the catalytic effect coefficient α. according to Calculated

[0075] (3) Prepare controllable low-strength backfill material according to the preset mass ratio of each raw material determined in step (2) to obtain slurry one; measure the flowability f0 of slurry one at 0 min as 137 mm, and the flowability f at 10 min as... t It is 173mm, according to The fluidity change rate of slurry one was calculated to be V1 = 3.6 mm / min; controllable low-strength backfill material was prepared according to the basic aggregate ratio and the preset mass ratio of other raw materials obtained in step (2), resulting in slurry two; the fluidity f0 of slurry two at 0 min was measured to be 150 mm, and the fluidity f at 10 min was measured to be... t It is 200mm, according to The flowability change rate of slurry 2 was calculated to be V2 = 5 mm / min, V2 > V1, and the flow characteristic influence coefficient β = 1 was determined.

[0076] The mass ratio of construction waste and tunnel boring machine excavation was adjusted a second time based on the flow characteristic influence coefficient β to determine the final basic aggregate ratio. according to Calculated

[0077] (4) Determine the amounts of industrial waste, cement, and water based on the amount of construction waste, the mass ratio of industrial waste to basic aggregate, the mass ratio of cement to industrial waste, and the water-to-solid ratio; wherein, the amount of industrial waste is the total amount of mineral powder and fly ash, the amount of construction waste is x parts, the mass ratio of industrial waste to basic aggregate is 0.3:1, the mass ratio of cement to industrial waste is 0.1:1, and the water-to-solid ratio is 0.35;

[0078] The total mass fractions of SiO2, Al2O3, Fe2O3, and CaO in the shield tunnel slag, mineral powder, and fly ash used were measured as follows: 0.87χ parts 0.256 x parts 0.0355χ parts, W CaO It is 0.275χ parts; according to The calculated silica ratio SR is 2.98, based on... The calculated calcium oxide ratio LR is 0.244, and the silica ratio SR and calcium oxide ratio LR satisfy 2.97≤SR≤3.65 and 0.21≤LR≤0.33, respectively. Therefore, there is no need to adjust the mass ratio of mineral powder and fly ash.

[0079] The amount of solid water glass was determined, and the modulus of the solid water glass was adjusted using NaOH to obtain a modified water glass solution. The mass ratio of solid water glass to basic aggregate was 0.0125:1. The modified water glass solution was prepared by mixing solid water glass and hot water at a mass ratio of 1:2 to fully dissolve the solid water glass. After cooling, solid NaOH was added to adjust the modulus, resulting in the modified water glass solution. The solid water glass was a solid white powder with a modulus of 3.4.

[0080] The mass proportions of each raw material in the final controllable low-strength backfill material are shown in Table 1, based on mass parts.

[0081] Table 1. Composition of Controllable Low-Strength Backfill Material in Example 1

[0082]

[0083] (5) Weigh each raw material according to the amount of raw materials determined in step (4) (Table 1). First, put the construction waste, shield tunnel slag, industrial waste, and cement into a large container and pre-stir to ensure that all dry components are fully and evenly mixed. Then, slowly add the weighed water to start basic stirring. After stirring for 10 minutes, add the modified water glass solution and continue stirring for 10 minutes to ensure that all components are thoroughly and evenly mixed to obtain slurry. Inject the obtained slurry into a 70.7mm×70.7mm×70.7mm triple mold for curing. The curing temperature is 23℃, the relative humidity is 97%, and the curing time is 48h to obtain a controllable low-strength backfill material modified by combining construction waste with shield tunnel slag.

[0084] The flowability, bleeding rate, setting time, and compressive strength of the controllable low-strength backfill material prepared in Example 1 were determined, and the results are shown in Table 2. The flowability test was conducted according to the test methods in ASTM D-6103 (Test Method for Flow Consistency of Controlled Low Strength Material), the bleeding rate was tested according to the "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" (GB / T50080-2016), and the setting time and compressive strength were tested according to the "Standard for Test Methods of Basic Performance of Building Mortar" (JGJ / T70-2009).

[0085] Table 2. Performance test results of Example 1

[0086]

[0087] Example 2

[0088] A method for preparing a controllable low-strength backfill material utilizing construction waste and shield tunneling slag modification, comprising the following steps:

[0089] (1) Remove impurities from existing construction waste materials, such as plastics and other organic lightweight materials, crush them with a jaw crusher, grind them with a Raymond mill, and then screen them to obtain construction waste materials with a particle size ≤ 4.5 mm; dry the existing shield tunnel slag with water until the moisture content is less than 10%, and then screen it to obtain shield tunnel slag with a particle size ≤ 9.5 mm.

[0090] (2) The raw materials used to prepare controllable low-strength backfill material are pre-proportioned in terms of mass ratio; construction waste x parts, shield tunnel slag 1.4 x parts, industrial waste 0.72 x parts, cement 0.072 x parts, water 1.0017 x parts, solid water glass in modified water glass solution 0.03 x parts, the mass ratio of mineral powder and fly ash in industrial waste 9:8.06, and the modulus of modified water glass solution is 1.2; the average specific surface area S of construction waste in step (1) is measured. cw 498m 2 / kg, determine the average specific surface area S of the shield tunneling debris in step (1). sr It is 14.3m 2 / kg, R is obtained according to the formula for calculating the specific surface area coefficient. s =0.05×S cw / S sr =1.74;

[0091] Based on the pre-set quality control of construction waste cw Preset quality QC for tunnel excavation sr The ratio value is used to obtain the preset mass ratio value. Compare specific surface area coefficients R s >Preset mass ratio The catalytic effect coefficient was determined to be α = 1.13;

[0092] The basic aggregate mix ratio is determined by adjusting the mass ratio of construction waste and tunnel boring machine slag based on the catalytic effect coefficient α. according to Calculated

[0093] (3) Prepare controllable low-strength backfill material according to the preset mass ratio of each raw material determined in step (2) to obtain slurry one; measure the flowability f0 of slurry one at 0 min as 114 mm, and the flowability f at 15 min as... tIt is 189mm, according to The fluidity change rate of slurry one was calculated to be V1 = 5 mm / min; controllable low-strength backfill material was prepared according to the basic aggregate ratio and the preset mass ratio of other raw materials obtained in step (2), resulting in slurry two; the fluidity f0 of slurry two at 0 min was measured to be 159 mm, and the fluidity f0 at 15 min was measured to be... t It is 220mm, according to The calculated fluidity change rate of slurry 2 is V2 = 4.07 mm / min, V2 < V1, and the influence coefficient of flow characteristics is determined to be β = 1.12;

[0094] The mass ratio of construction waste and tunnel boring machine excavation was adjusted a second time based on the flow characteristic influence coefficient β to determine the final basic aggregate ratio. according to Calculated

[0095] (4) Determine the amounts of industrial waste, cement, and water based on the amount of construction waste, the mass ratio of industrial waste to basic aggregate, the mass ratio of cement to industrial waste, and the water-solid ratio; wherein the amount of industrial waste is the total amount of mineral powder and fly ash, the mass ratio of industrial waste to basic aggregate is 0.3:1, the mass ratio of cement to industrial waste is 0.1:1, and the water-solid ratio is 0.35;

[0096] The total mass fractions of SiO2, Al2O3, Fe2O3, and CaO in the shield tunnel slag, mineral powder, and fly ash used were measured as follows: 1.48 x parts 0.376 x parts 0.0543χ parts, W CaO It is 0.448χ parts; according to The calculated silica ratio SR is 3.44, based on... The calculated calcium oxide ratio LR is 0.24, and the silica ratio SR and calcium oxide ratio LR satisfy 2.97≤SR≤3.65 and 0.21≤LR≤0.33, therefore there is no need to adjust the mass ratio of mineral powder and fly ash.

[0097] The amount of solid water glass was determined, and the modulus of the solid water glass was adjusted using NaOH to obtain a modified water glass solution. The mass ratio of solid water glass to basic aggregate was 0.0125:1. The modified water glass solution was prepared by mixing solid water glass and hot water at a mass ratio of 1:2 to fully dissolve the solid water glass. After cooling, solid NaOH was added to adjust the modulus, resulting in the modified water glass solution. The solid water glass was a solid white powder with a modulus of 3.4.

[0098] The mass ratio of each raw material in the final controllable low-strength backfill material is shown in Table 3, based on mass parts.

[0099] Table 3. Composition of Controllable Low-Strength Backfill Material in Example 2

[0100]

[0101] (5) Weigh each raw material according to the amount of raw materials determined in step (4) (Table 3). First, put the construction waste, shield tunnel slag, industrial waste, and cement into a large container and pre-stir to ensure that all dry components are fully mixed. Then, slowly add the weighed water to start basic stirring. After stirring for 10 minutes, add the modified water glass solution and continue stirring for 10 minutes to ensure that all components are thoroughly mixed to obtain slurry. Inject the obtained slurry into a 70.7mm×70.7mm×70.7mm triple mold for curing. The curing temperature is 23℃, the relative humidity is 97%, and the curing time is 48h to obtain a controllable low-strength backfill material modified by combining construction waste with shield tunnel slag.

[0102] The flowability, bleeding rate, setting time, and compressive strength of the controllable low-strength backfill material prepared in Example 2 were measured, and the results are shown in Table 4.

[0103] Table 4. Performance test results of Example 2

[0104]

[0105] Example 3

[0106] A method for preparing a controllable low-strength backfill material utilizing construction waste and shield tunneling slag modification, comprising the following steps:

[0107] (1) Remove impurities from existing construction waste materials, such as plastics and other organic lightweight materials, crush them with a jaw crusher, grind them with a Raymond mill, and then screen them to obtain construction waste materials with a particle size ≤ 4.5 mm; dry the existing shield tunnel slag with water until the moisture content is less than 10%, and then screen it to obtain shield tunnel slag with a particle size ≤ 9.5 mm.

[0108] (2) The raw materials used to prepare controllable low-strength backfill material are pre-proportioned: construction waste x parts, shield tunnel slag x parts, industrial waste 0.6 x parts, cement 0.06 x parts, water 0.8155 x parts, solid water glass in modified water glass solution 0.025 x parts, the mass ratio of mineral powder and fly ash in industrial waste slag is 9:6.44, and the modulus of modified water glass solution is 1.2; the average specific surface area S of construction waste in step (1) is determined. cw 439m 2 / kg, determine the average specific surface area S of the shield tunneling debris in step (1). sr 23.2m 2 / kg, R is obtained according to the formula for calculating the specific surface area coefficient. s =0.05×S cw / S sr =0.946;

[0109] Based on the pre-set quality control of construction waste cw Preset quality QC for tunnel excavation sr The preset mass ratio obtained by the ratio of Specific surface area coefficient < preset mass ratio The catalytic effect coefficient α is determined to be 1;

[0110] The basic aggregate mix ratio is determined by adjusting the mass ratio of construction waste and tunnel boring machine slag based on the catalytic effect coefficient α. according to Calculated

[0111] (3) Prepare controllable low-strength backfill material according to the preset mass ratio of each raw material determined in step (2) to obtain slurry one; measure the flowability f0 of slurry one at 0 min as 117 mm, and the flowability f at 10 min as... t It is 174mm, according to The fluidity change rate of slurry one was calculated to be V1 = 5.7 mm / min; controllable low-strength backfill material was prepared according to the basic aggregate ratio and the preset mass ratio of other raw materials obtained in step (2), resulting in slurry two; the fluidity f0 of slurry two at 0 min was measured to be 128 mm, and the fluidity f0 at 10 min was measured to be... t It is 190mm, according to The calculated fluidity change rate of slurry 2 is V2 = 6.2 mm / min, V2 > V1, and the influence coefficient of flow characteristics is determined to be β = 1;

[0112] The mass ratio of construction waste and tunnel boring machine excavation was adjusted a second time based on the flow characteristic influence coefficient β to determine the final basic aggregate ratio. according to Calculated

[0113] (4) Determine the amounts of industrial waste, cement, and water based on the amount of construction waste, the mass ratio of industrial waste to basic aggregate, the mass ratio of cement to industrial waste, and the water-solid ratio; wherein the amount of industrial waste is the total amount of mineral powder and fly ash, the mass ratio of industrial waste to basic aggregate is 0.3:1, the mass ratio of cement to industrial waste is 0.1:1, and the water-solid ratio is 0.35;

[0114] The total mass fractions of SiO2, Al2O3, Fe2O3, and CaO in the shield tunnel slag, mineral powder, and fly ash used were measured as follows: 1.228 x parts 0.331χ parts 0.0484 x parts, W CaO It is 0.353χ parts; according to The calculated silica ratio SR is 3.24, based on... The calculated calcium oxide ratio LR is 0.226, and the silica ratio SR and calcium oxide ratio LR satisfy 2.97≤SR≤3.65 and 0.21≤LR≤0.33, therefore there is no need to adjust the mass ratio of mineral powder and fly ash.

[0115] The amount of solid water glass was determined, and the modulus of the solid water glass was adjusted using NaOH to obtain a modified water glass solution. The mass ratio of solid water glass to basic aggregate was 0.0125:1. The modified water glass solution was prepared by mixing solid water glass and hot water at a mass ratio of 1:2 to fully dissolve the solid water glass. After cooling, solid NaOH was added to adjust the modulus, resulting in the modified water glass solution. The solid water glass was a solid white powder with a modulus of 3.4.

[0116] The mass proportions of each raw material in the final controllable low-strength backfill material are shown in Table 5, based on mass parts.

[0117] Table 5. Composition of Controllable Low-Strength Backfill Material in Example 3

[0118]

[0119] (5) Weigh each raw material according to the amount of raw materials determined in step (4) (Table 5). First, put the construction waste, shield tunnel slag, industrial waste, and cement into a large container and pre-stir to ensure that all dry components are fully and evenly mixed. Then, slowly add the weighed water to start basic stirring. After stirring for 10 minutes, add the modified water glass solution and continue stirring for 10 minutes to ensure that all components are thoroughly and evenly mixed to obtain slurry. Inject the obtained slurry into a 70.7mm×70.7mm×70.7mm triple mold for curing. The curing temperature is 23℃, the relative humidity is 97%, and the curing time is 72h to obtain a controllable low-strength backfill material modified by combining construction waste with shield tunnel slag.

[0120] The flowability, bleeding rate, setting time, and compressive strength of the controllable low-strength backfill material prepared in Example 3 were measured, and the results are shown in Table 6.

[0121] Table 6. Performance test results of Example 3

[0122]

[0123] The fluidity test demonstrates the material's flowability; the bleeding rate assesses the material's stability; and the setting time provides an important basis for comprehensive consideration of on-site construction scheduling.

[0124] In Examples 1-3, the following patterns can be observed: As the proportion of construction waste increases, the material's fluidity and bleeding rate decrease, the initial and final setting times shorten significantly, and the compressive strength increases. A decrease in the water glass modulus leads to a reduction in the material's fluidity, bleeding rate, setting time, and compressive strength. Increased mineral powder content decreases the material's fluidity and bleeding rate, shortens the setting time, and increases the compressive strength. Decreased fly ash content increases the material's fluidity and bleeding rate, prolongs the setting time, and decreases the compressive strength.

[0125] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a controllable low-strength backfill material that utilizes construction waste in conjunction with the modification of shield tunneling excavation soil, characterized in that, Includes the following steps: (1) The raw materials used to prepare controllable low-strength backfill material are pre-proportioned in terms of mass ratio. Specifically, the mass parts of each raw material are related as follows: construction waste x parts; shield tunnel slag (1~2.38)×x parts; industrial waste 0.3×{(1~2.38)×x+x} parts; cement 0.03×{(1~2.38)×x+x} parts; water 0.35×{1.33×(1~2.38)×x+x} parts; solid water glass in modified water glass solution 0.0125×{(1~2.38)×x+x} parts; The average specific surface area of ​​construction waste and tunnel boring machine (TBM) slag was measured separately, and the specific surface area coefficient was obtained based on the ratio of their average specific surface areas. Specifically ,in, This represents the average specific surface area of ​​construction waste. This represents the average specific surface area of ​​the tunnel boring machine excavation soil. Based on specific surface area coefficient Determine the catalytic effect coefficient Specifically, if the specific surface area coefficient ≤Preset mass ratio ,but If the specific surface area coefficient >Preset mass ratio ,but Among them, the preset mass ratio value The calculation formula is: , Indicates the pre-set mass of construction waste. Indicates the preset mass of tunnel boring machine excavation; Based on the catalytic effect coefficient The mass ratio of construction waste and tunnel boring machine excavation soil was adjusted to determine the basic aggregate mix ratio. , The calculation formula is: The basic aggregates are construction waste and tunnel boring machine excavation soil. (2) Prepare controllable low-strength backfill material according to the preset mass ratio of each raw material determined in step (1) to obtain slurry one; prepare controllable low-strength backfill material according to the basic aggregate ratio and the preset mass ratio of other raw materials obtained in step (1) to obtain slurry two; measure the flowability of slurry one and slurry two at time 0 and time t respectively, and obtain the flowability change rate based on the flowability of slurry one and slurry two. , The calculation formula is: ,in, This indicates the fluidity of the slurry at time 0. This indicates the fluidity of the slurry at time t. For 10-20 minutes; The flow characteristic influence coefficient is determined based on the flowability change rate. Specifically, if the rate of change of fluidity of slurry two is... The rate of change in fluidity of slurry one is greater than that of slurry one. ,but If the fluidity change rate of slurry two The change rate of fluidity of slurry one is less than that of slurry one. ,but ; Based on the influence coefficient of flow characteristics The mass ratio of construction waste and tunnel boring machine excavation materials was adjusted a second time to determine the final basic aggregate ratio. , The calculation formula is: ; (3) Determine the amount of industrial waste, cement and water based on the amount of construction waste, the mass ratio of industrial waste to basic aggregate, the mass ratio of cement to industrial waste, and the water-solid ratio; wherein, the amount of industrial waste is the total amount of mineral powder and fly ash. The determination of the content of shield tunnel slag, mineral powder and fly ash used in the test , , and Total mass fraction , , , Based on the preset mass ratio of mineral powder and fly ash, the silica ratio of controllable low-strength backfill material was calculated. The ratio of calcium oxide to calcium oxide , The calculation formula is: , The calculation formula is: Based on the obtained silica ratio The ratio of calcium oxide to calcium oxide Determine the ratio of mineral powder and fly ash, specifically: if the silica ratio... Ratio to calcium oxide satisfy and If the above values ​​are not met, then there is no need to adjust the mass ratio of mineral powder to fly ash; if the above values ​​are not met, then the mass ratio of mineral powder to fly ash needs to be further adjusted. Determine the amount of solid water glass to be used, and adjust the modulus of the solid water glass using NaOH to obtain a modified water glass solution; (4) Weigh each raw material according to the amount of raw materials determined in step (3). First, mix the construction waste, shield tunnel slag, industrial waste and cement and then pre-stir. Then add water for basic stirring. After stirring for 10-15 minutes, add modified water glass solution and continue stirring for 5-10 minutes. After curing, the controllable low-strength backfill material modified by construction waste and shield tunnel slag is obtained.

2. The preparation method according to claim 1, characterized in that, In step (1), before determining the average specific surface area of ​​the construction waste, the steps of removing impurities, crushing, grinding and screening the construction waste are also included.

3. The preparation method according to claim 2, characterized in that, The crushing equipment is one of a jaw crusher, a cone crusher, or a hammer crusher; the grinding equipment is one of a Raymond mill, a ball mill, or a cone ball mill; the particle size of the construction waste after screening is ≤4.5mm.

4. The preparation method according to claim 1, characterized in that, In step (1), before determining the average specific surface area of ​​the shield tunneling slag, the shield tunneling slag is also subjected to a water-drying treatment and sieving.

5. The preparation method according to claim 4, characterized in that, The moisture content of the shield tunneling slag after the dewatering and drying treatment is <10%, and the particle size of the shield tunneling slag after screening is ≤9.5mm.

6. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of industrial waste residue to basic aggregate is 0.3:1; the mass ratio of cement to industrial waste residue is 0.1:1; the water-to-solid ratio is 0.35; and the mass ratio of solid water glass to basic aggregate is 0.0125:

1.

7. The preparation method according to claim 1, characterized in that, In step (4), the curing temperature is 21-25℃, the relative humidity is >95%, and the time is 24-72h.

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