Cement improved tailing roadbed construction method

Abstract

The invention belongs to the technical field of roadbed construction methods, and particularly relates to a cement improved tailing roadbed construction method. The method comprises the following steps: S1, determining the water content and particle composition of the tailings; s2, calculating the average particle size of the tailings in each grade of particle size range; s3, calculating the thickness of a water film on the surface of the centrifuged tailings; s4, determining the cement dosage and the water-cement ratio in the cement-improved tailing roadbed material according to experience, and determining the water content control value of the cement-improved tailing roadbed material in the construction process; and S5, the tailings are evenly arranged on the roadbed, the water content of the tailings reaches the water content control value + / -1%, then cement is evenly spread, the cement and the tailings are mixed, leveling is conducted through a land leveler, and finally rolling forming is conducted through a heavy road roller. According to the method, when the use amount of the tailing raw material, the cement and the like changes, the field construction water content control value is calculated in real time, it is ensured that the performance of the cement-improved tailing roadbed material is optimal, and the engineering quality is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of roadbed construction methods, and in particular relates to a cement-improved tailings roadbed construction method. Background Art

[0002] Tailings are solid waste discharged by mineral processing plants after extracting useful components from ore. Currently, the main way to reuse tailings is to prepare sintered bricks and steam bricks, and to backfill mined-out areas. However, these methods cannot completely absorb the tailings. A large amount of tailings that have not been comprehensively utilized are still mainly treated by stacking. This not only forces companies to build tailings ponds and bear high infrastructure costs, but also occupies valuable land resources.

[0003] With the rapid development of highways, the demand for road construction materials is increasing day by day. The shortage of road construction materials has seriously restricted the development of highway industry, especially in plain areas. Due to the limitation of basic farmland, it is very difficult to obtain soil in the surrounding areas. The fill height of roads in plain areas is generally between 3 and 5 meters. The demand for roadbed fillers on expressways exceeds 300,000 tons / km. The geometric shape and chemical composition of tailings are similar to those of natural aggregates and soil, and can be used as their substitutes. Preparing tailings into roadbed fillers can not only provide a better way for large-scale disposal of tailings, but also solve the problem of roadbed filler supply. It is a win-win approach.

[0004] Tailings themselves have no sticky components, and their plasticity index is less than 5, making them unable to form good cohesion. Cement, as a commonly used solidifying binder, is generally used to consolidate materials without cohesion, such as silt and gravel. Using cement to improve tailings can give them higher strength and stability, thereby preparing fillers that meet the requirements of roadbed use. Cement-improved tailings usually involve drying the tailings and then determining the optimal moisture content through indoor compaction tests. The existing interaction effect between tailings and cement and moisture content control rely entirely on indoor tests, making it difficult to achieve optimal performance. In addition, the tailings in the laboratory need to be completely dried, and the added water can react with the cement. However, in actual construction sites, the tailings cannot be completely dried, and the tailings contain free water and bound water. The free water will participate in the cement mixing reaction process. Therefore, if the construction site is controlled according to the optimal moisture content obtained in the laboratory, the effect achieved is often inconsistent with the laboratory effect.

[0005] Therefore, a cement-improved tailings roadbed construction method is badly needed to solve the above problems. Summary of the Invention

[0006] To overcome the above-mentioned shortcomings of the prior art, the present invention provides a method for constructing a cement-modified tailings roadbed. The method utilizes cement for improvement, combines the characteristics of the tailings raw material, and precisely controls the moisture content on site, thereby enabling sufficient interaction between the tailings, water, and cement, thereby improving the overall structural strength and stability of the roadbed.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A cement-improved tailings roadbed construction method, the specific steps are as follows: S1. Determine the moisture content and particle composition of the tailings; S2. Obtain the chord length and arc length of the tailings particles by SEM scanning technology, and calculate the average particle size of the tailings within each particle size range; S3. Calculate the thickness of the water film on the surface of the tailings after centrifugation based on the specific surface area of ​​the tailings and the mass of water adsorbed on the surface of the tailings after centrifugation; S4. Determine the cement dosage and water-cement ratio of the cement-improved tailings roadbed material based on experience, and determine the moisture content control value of the cement-improved tailings roadbed material during the construction process; S5. Evenly arrange the tailings on the roadbed so that its moisture content reaches the moisture content control value ±1%, then evenly spread cement, mix the cement and tailings using on-site mixing, use a grader to level it, and finally use a heavy roller to compact it into shape.

[0008] Preferably, in step S1, the tailings are dried to determine their moisture content, and a screening test is performed to determine the particle composition of the tailings.

[0009] Preferably, in step S2, the method for obtaining the chord length and arc length of the tailings particles is: take 10 to 15 g of tailings samples within each particle size range after drying, place them on a workbench, and use SEM scanning technology to collect tailings distribution images within each particle size range on the workbench, filter and histogram equalize the images, and then extract the chord length and arc length of the tailings particles in the image.

[0010] Preferably, in step S2, the calculation formula for the average particle size of the tailings within each particle size range is: ; ; ; ; Where: r a - tailings particle size at a central angle θ of 2π in the image, mm; s a - the arc length of the tailings particle with a central angle θ of 2π in the image, mm; cb - Chord length of tailings particles with a central angle θ of 0<θ≤π in the image, mm; r b - The tailings particle size in the image with a central angle θ of 0<θ≤π, mm; s b -The arc length of the tailings particles with a central angle θ of 0<θ≤π in the image, mm; c c - Chord length of tailings particles with a central angle θ of π<θ<2π in the image, mm; r c - The tailings particle size when the central angle θ in the image is π<θ<2π, mm; s c -The arc length of the tailings particle with the central angle θ of π<θ<2π in the image, mm; r k -The average particle size of tailings in the kth particle size range, mm; n - the number of tailings in the image with a central angle θ of 2π; i - the number of tailings with a central angle θ of 0<θ≤π in the image; j - the number of tailings with a central angle θ of π<θ<2π in the image.

[0011] Preferably, in step S3, 50 to 100 g of natural undried tailings with a particle size of 0.6 mm to 1.18 mm are taken, the tailings are placed in a closed container and centrifuged for 2 to 3 minutes, and absorbent paper is placed at the bottom of the container; then the mass of the tailings after centrifugation is weighed, the tailings are dried, and the mass after drying is weighed to obtain the specific surface area of ​​the tailings and the mass of water adsorbed on the surface of the tailings after centrifugation.

[0012] Preferably, the calculation formula for the water film thickness on the tailings surface after centrifugation is: ; ; Where: SA 0.6~1.18 -Specific surface area of ​​tailings with particle size of 0.6mm~1.18mm, m 2 / kg; r w -Density of tailings, g / cm 3 ; r 0.6~1.18 - Average particle size of tailings with particle size of 0.6mm to 1.18mm, mm; μ - thickness of water film on the tailings surface after centrifugation, um; m l - Mass of tailings with particle size of 0.6mm to 1.18mm after centrifugation, g; mh - Mass of the tailings with a particle size of 0.6mm to 1.18mm after drying, g; r s -Density of water, g / cm 3 .

[0013] Preferably, the calculation formula of the moisture content control value is: ; Where: w-Control value of moisture content in the construction of cement-improved tailings roadbed, %; P s - Cement usage in cement-improved tailings roadbed materials, %; - Water-cement ratio of cement-improved tailings roadbed materials; μ - thickness of water film on the tailings surface after centrifugation, um; k - the number of particle size fractions for tailings; P k -The proportion of particle size in the kth level in the tailings, %; r w -Density of tailings, g / cm 3 ; r k -The average particle size of tailings in the kth particle size range, mm; r s -Density of water, g / cm 3 .

[0014] Preferably, the cement content in the cement-improved tailings roadbed material is 3.0-4.0%; and the water-cement ratio is 0.45-0.55.

[0015] Preferably, the particle size of the tailings is ≤1.18 mm; the content of tailings with a particle size less than 0.075 mm is ≤70%; and the moisture content of the tailings in a natural state is ≤14%.

[0016] Preferably, in step S5, after the tailings are evenly arranged on the roadbed, their moisture content is measured. If the moisture content is higher than the moisture content control value ±1%, the tailings are aired; if the moisture content is lower than the moisture content control value ±1%, watering is carried out; the filler of the cement-improved tailings roadbed is spread in layers with a thickness of 30 to 40 cm, and the minimum compacted thickness of the last layer filled to the top of the roadbed is ≥10 cm.

[0017] The advantages of the present invention are: (1) The present invention adopts cement to improve tailings. In combination with the raw material characteristics of tailings, the present invention precisely controls the moisture content on site, so that the tailings, water and cement fully interact with each other to improve the overall structural strength and stability of the roadbed. The present invention is used to scientifically calculate the moisture content control value during the construction process, so that the interaction between cement and tailings can achieve the best effect, thereby ensuring good construction quality.

[0018] (2) The present invention addresses the defects existing in the on-site construction process of cement-modified tailings. Based on the characteristics of tailings materials, the present invention fully considers the interaction between tailings, water and cement during the construction process, combines the thickness of the water film on the tailings surface, and fully reacts with cement. When the tailings raw materials, cement dosage, etc. change, the on-site construction moisture content control value is calculated in real time, thereby ensuring that the performance of the cement-modified tailings roadbed material reaches the optimal level and improving the quality of the project.

[0019] (3) The present invention adopts microscopic image recognition technology to analyze the composition of tailings particles and calculates the average particle size of tailings in each particle size range. Based on this, and in combination with relevant experimental methods, the water film thickness on the surface of the tailings after centrifugation and the mass of water adsorbed on the surface of the tailings are accurately calculated, and the interaction between free water and cement is taken into account to obtain the on-site construction moisture content control value. This method takes into account the influence of tailings of different particle sizes, greatly improves the accuracy of the results, and provides a scientific and accurate calculation method for the on-site construction moisture content control value of cement-modified tailings.

[0020] (4) The present invention calculates the moisture content control value of cement-modified tailings on-site construction based on relevant parameters such as on-site tailings raw materials and cement usage, which greatly reduces the test volume and improves work efficiency; and industrial waste tailings are used as roadbed fillers, realizing waste utilization and saving resources. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] Example 1 S1. Take the copper tailings and dry them. The water content is 13.8%. The particle composition of the copper tailings is determined by sieving test. The density of water is 1g / cm 3 , the density of dried copper tailings r w 2.81g / cm 3 , the copper tailings after drying were screened, and the results are shown in Table 1 below: Table 1 Copper tailings screening results ; S2. Take 11g of dried copper tailings samples within each particle size range and place them on a workbench. Use SEM scanning technology to collect distribution images of copper tailings within each particle size range on the workbench. Perform filtering and histogram equalization on the images to extract the chord length and arc length of the copper tailings particles in the images. The results are shown in Table 2 below: Table 2 Parameter values ​​for copper tailings image extraction in various particle size ranges ; S3. Calculate the average particle size of copper tailings within each particle size range according to the following formula. The results are shown in Table 3 below: ; ; ; ; Table 3 Average particle size of copper tailings in each range ; S4. Take 65 g of natural undried copper tailings with a particle size of 0.6 mm to 1.18 mm, place the copper tailings in a closed container and centrifuge for 2 minutes, with absorbent paper placed at the bottom of the container; weigh 61.1 g of the copper tailings after centrifugation, dry the copper tailings, and weigh 55.5 g of the dried mass. Based on the specific surface area of ​​the copper tailings and the mass of water adsorbed on the surface of the copper tailings after centrifugation, calculate the water film thickness on the surface of the copper tailings after centrifugation. The calculation formula is as follows: = 2.26m 2 / kg; = 4.5um; S5. Based on relevant engineering experience, the cement content in the cement-improved tailings roadbed material is determined to be 3.5% and the water-cement ratio is 0.50; S6. Based on the cement dosage and water-cement ratio, the moisture content control value of the cement-improved tailings roadbed material during construction is calculated as 12.1% according to the following formula; ; S7. Evenly arrange the copper tailings on the roadbed with a layered paving thickness of 35 cm and a loose paving coefficient of 1.2. Then determine that the loose paving thickness of the copper tailings is 42 cm, and measure its moisture content to be 13.8%, which is 1.7% higher than the moisture content control value of 12.1%. Dry the copper tailings to make its moisture content reach the moisture content control value of 12.1±1%, and then evenly spread 3.5% cement. Use on-site mixing method, use a BMW machine to mix evenly, use a grader to level, and finally use a heavy roller to compact and shape.

[0023] The copper tailings were dried and compaction tests were carried out on the 3.5% cement-amended copper tailings according to the method specified in the geotechnical test regulations to determine their optimum moisture content and CBR value.

[0024] The cement-amended copper tailings mixed on site were sampled and the cement dosage, moisture content and CBR performance of the cement-amended copper tailings were verified using compaction tests and CBR tests. The results are shown in Table 4 below: Table 4 ; As shown in Table 4, the CBR value of the field sampling test is higher than the CBR value of the indoor test, indicating that the roadbed implemented by the present invention has better stability and higher strength.

[0025] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cement-improved tailings roadbed construction method, characterized in that: The specific steps are as follows: S1. Determine the moisture content and particle composition of the tailings; S2. Obtain the chord length and arc length of the tailings particles by SEM scanning technology, and calculate the average particle size of the tailings within each particle size range; S3. Calculate the thickness of the water film on the surface of the tailings after centrifugation based on the specific surface area of ​​the tailings and the mass of water adsorbed on the surface of the tailings after centrifugation; S4. Determine the cement dosage and water-cement ratio of the cement-improved tailings roadbed material based on experience, and determine the moisture content control value of the cement-improved tailings roadbed material during the construction process; S5. Evenly arrange the tailings on the roadbed so that its moisture content reaches the moisture content control value ±1%, then evenly spread cement, mix the cement with the tailings, use a grader to level it, and finally use a heavy roller to compact it into shape.

2. A cement-improved tailings roadbed construction method according to claim 1, characterized in that: In step S1, the tailings are dried to determine their moisture content, and a screening test is performed to determine the particle composition of the tailings.

3. A cement-improved tailings roadbed construction method according to claim 1, characterized in that: In step S2, the method for obtaining the chord length and arc length of the tailings particles is as follows: 10 to 15 g of tailings samples within each particle size range after drying are taken and placed on a workbench. The tailings distribution image within each particle size range on the workbench is collected using SEM scanning technology, the image is filtered and histogram equalized, and then the chord length and arc length of the tailings particles in the image are extracted.

4. A cement-improved tailings roadbed construction method according to claim 1, characterized in that: In step S2, the calculation formula for the average particle size of the tailings within each particle size range is: ； ； ； ； Where: r a - tailings particle size at a central angle θ of 2π in the image, mm; s a - the arc length of the tailings particle with a central angle θ of 2π in the image, mm; c b - Chord length of tailings particles with a central angle θ of 0<θ≤π in the image, mm; r b - The tailings particle size in the image with a central angle θ of 0<θ≤π, mm; s b -The arc length of the tailings particles with a central angle θ of 0<θ≤π in the image, mm; c c - Chord length of tailings particles with a central angle θ of π<θ<2π in the image, mm; r c - The tailings particle size when the central angle θ in the image is π<θ<2π, mm; s c -The arc length of the tailings particle with the central angle θ of π<θ<2π in the image, mm; r k -The average particle size of tailings in the kth particle size range, mm; n - the number of tailings in the image with a central angle θ of 2π; i - the number of tailings with a central angle θ of 0<θ≤π in the image; j - the number of tailings with a central angle θ of π<θ<2π in the image.

5. The method for constructing a cement-improved tailings roadbed according to claim 1, wherein: In step S3, 50 to 100 g of natural undried tailings with a particle size of 0.6 mm to 1.18 mm are taken, and the tailings are placed in a closed container and centrifuged for 2 to 3 minutes, with absorbent paper placed at the bottom of the container; then the mass of the tailings after centrifugation is weighed, the tailings are dried, and the mass after drying is weighed to obtain the specific surface area of ​​the tailings and the mass of water adsorbed on the surface of the tailings after centrifugation.

6. A cement-improved tailings roadbed construction method according to claim 1 or 5, characterized in that: The calculation formula for the water film thickness on the tailings surface after centrifugation is: ； ； Where: SA 0.6~1.18 -Specific surface area of ​​tailings with particle size of 0.6mm~1.18mm, m 2 / kg; ρ w -Density of tailings, g / cm 3 ; r 0.6~1.18 - Average particle size of tailings with particle size of 0.6mm to 1.18mm, mm; μ - thickness of water film on the tailings surface after centrifugation, um; m l - Mass of tailings with particle size of 0.6mm to 1.18mm after centrifugation, g; m h - Mass of the tailings with a particle size of 0.6mm to 1.18mm after drying, g; ρ s -Density of water, g / cm 3 .

7. The method for constructing a cement-improved tailings roadbed according to claim 1, wherein: The calculation formula for the moisture content control value is: ； Where: w-Control value of moisture content in the construction of cement-improved tailings roadbed, %; P s - Cement usage in cement-improved tailings roadbed materials, %; - Water-cement ratio of cement-improved tailings roadbed materials; μ - thickness of water film on the tailings surface after centrifugation, um; k - the number of particle size fractions for tailings; P k -The proportion of particle size in the kth level in the tailings, %; ρ w -Density of tailings, g / cm 3 ; r k -The average particle size of tailings in the kth particle size range, mm; ρ s -Density of water, g / cm 3 .

8. A cement-improved tailings roadbed construction method according to claim 1 or 7, characterized in that: The amount of cement used in the cement-improved tailings roadbed material is 3.0-4.0%; the water-cement ratio is 0.45-0.

55.

9. The method for constructing a cement-improved tailings roadbed according to claim 1, wherein: The particle size of the tailings is ≤1.18mm; the content of tailings with a particle size less than 0.075mm is ≤70%; and the moisture content of the tailings in a natural state is ≤14%.

10. The method for constructing a cement-improved tailings roadbed according to claim 1, characterized in that: In step S5, after the tailings are evenly arranged on the roadbed, their moisture content is measured. If the moisture content is higher than the moisture content control value ±1%, the tailings are aired; if the moisture content is lower than the moisture content control value ±1%, water is sprinkled; the filler of the cement-improved tailings roadbed is spread in layers with a thickness of 30 to 40 cm, and the minimum compacted thickness of the last layer on the top of the roadbed is ≥10 cm.

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