Manufacturing method of high-water-content tailing soil roadbed material

Abstract

The invention relates to a manufacturing method of a roadbed material based on high-water-content tailing soil, and belongs to the field of road engineering and environmental geotechnical engineering. The roadbed material comprises high-water-content tailing soil, lime, cement and water; the preparation method comprises the following steps: crushing the high-water-content tailing soil, and measuring the initial water content of the high-water-content tailing soil; the method comprises the following steps: fully mixing high-water-content tailing soil with lime in different mass ratios, carrying out a lime precipitation test, crushing the tailing soil subjected to lime reaction, fully mixing the crushed tailing soil with cement and water in different mass ratios, carrying out a compaction test, and measuring the optimal water content and the maximum dry density under different cement dosages; according to the optimal water content and the maximum dry density, a California bearing ratio test is carried out, and the optimal cement mixing amount is preferably selected; and producing the high-water-content tailing soil roadbed material. According to the method, the quicklime is adopted for carrying out precipitation pretreatment on the high-water-content tailing soil, and compared with a drying method in a laboratory, the feasibility in large-scale industrial production is higher.

Description

Technical Field

[0001] The invention relates to a method for preparing a tailings soil roadbed material with a high water content, and belongs to the fields of road engineering and environmental geotechnical engineering. Background Art

[0002] Tailings soil is a byproduct of the iron ore beneficiation process. It is the solid waste with the lowest content of the target component after the sorting operation. It is generally in the form of fine powder, but because it is accumulated in the tailings pond all year round, there are many sticky particles inside, and the water retention capacity is strong. Once it rains, the water is not easy to lose, so the water content is generally high. At present, the stock of tailings soil still remains at a high level. On the one hand, the storage of a large amount of tailings soil requires the factory to bear additional land acquisition fees, transportation costs, landfill fees, etc., which increases production costs; on the other hand, this accumulation of tailings soil not only requires a large amount of land resources, but also easily causes environmental pollution and safety problems. New pollutants are likely to be formed during the deposition of tailings soil. All signs indicate that the reduction of the stock of tailings soil is imminent.

[0003] The sources of materials for road construction are diversified and they are characterized by large consumption. The huge consumption of soil, stone and sand and gravel has caused great environmental pressure on some sand and gravel production areas, and even excessive mining has occurred, causing damage to the local ecological environment. Therefore, the recycling of tailings soil resources in road construction can not only solve the various problems caused by the current large-scale accumulation of tailings soil, but also meet the huge demand for materials in road construction, reduce the cost of road construction, and achieve dual benefits of ecology and economy.

[0004] Many existing patents have also innovated the reuse of tailings soil in road engineering. For example, patent CN114292064A discloses a cement-stabilized tailings pavement semi-rigid base, which uses dried coarse-grained and fine-grained tailings waste rock and tailings soil with a particle size of more than 0.075 mm for grading design, and cement is added to prepare the semi-rigid base material of the pavement.

[0005] Patent CN109020338A discloses a design method for cement-stabilized tailings base materials. The method conducts a large number of 7d unconfined compressive strength tests on mixtures with 5-30% dry tailings soil, and uses a star-point design test table to fit a ternary quadratic equation to select the best design parameters.

[0006] Patent CN104152148A discloses a method for preparing a road base material by stabilizing tailings soil with a new soil solidifier. Under laboratory conditions, the road base material is obtained by mixing cement, crushed stone, dried tailings soil, a new soil solidifier and polypropylene fibers.

[0007] In summary, although the reuse of tailings soil in road engineering has achieved certain results, it does not have much reference value for most tailings soil with a particle size less than 0.075 mm, and the proportion of tailings soil in the material is relatively small, and it cannot effectively solve the problem of large tailings soil inventory. More importantly, most patents emphasize drying tailings soil under laboratory conditions and then making materials for different layers of the road surface, but high water content is an inevitable and important feature of tailings soil. At the same time, due to the limitations of on-site construction conditions, the current methods of drying tailings soil with high water content are quite costly, such as vacuum pumping, filter press dehydration, etc., which are difficult to use in large quantities in actual projects. This also makes the material production based on the laboratory environment unable to be applied to actual projects. Summary of the invention

[0008] The present invention aims at the practical problems that the tailings soil inventory is large, the technical process for recycling a large amount of viscous tailings soil is insufficient, and the high water content is difficult to solve in industrial production, and provides a method for preparing a tailings soil roadbed material with a high water content.

[0009] The present invention adopts the following technical solution:

[0010] A method for preparing a high-water content tailings soil roadbed material, the roadbed material comprising high-water content tailings soil, lime, cement, and water;

[0011] The production steps are as follows:

[0012] Step S1: crush the high-water content tailings soil and measure its initial water content w 0 ;

[0013] Step S2: After the tailings soil with high water content and lime in different mass ratios are fully mixed, a lime precipitation test is performed to preset the water content w set Determine the best lime dosage as the main control index;

[0014] Step S3: crush the tailings soil after lime reaction, mix it with cement and water in different mass ratios, and then conduct compaction test to measure the optimal moisture content w under different cement dosages. opt and maximum dry density ρ dmax ;

[0015] Step S4: According to the optimal moisture content w opt and maximum dry density ρ dmax , after the tailings soil after lime reaction, cement and water are fully mixed and compacted according to different cement dosages, the California bearing ratio test is carried out to select the best cement dosage;

[0016] Step S5: Determine the mix ratio of the roadbed material according to the optimal lime content, the optimal moisture content and the optimal cement content, and produce a high-moisture-content tailings soil roadbed material.

[0017] The method for making the high-water content tailings soil roadbed material and the high-water content tailings soil roadbed test method of the present invention comprise the following steps:

[0018] Step S1: crush the high-water content tailings soil and measure its initial water content w 0 ;

[0019] Step S2: Add lime of different mass ratios into the tailings soil with high water content and mix thoroughly to obtain the optimum water content w obtained by the compaction test of common clay soil. opt is the preset moisture content w set ;

[0020] Step S3: Perform static precipitation for 4 days, a total of 96 hours, during which the moisture content is measured every 12 hours, and the moisture content on the surface of the tailings pile and the moisture content inside the tailings pile are measured respectively, and the average value is taken as the moisture content data;

[0021] Step S4: Arrange the data obtained in step S3. The moisture content decline curve of high-water content tailings soil should follow the basic soil evaporation theory. The Black evaporation model is used to fit and analyze the data. If the significance test fails, it is necessary to re-test to obtain data and fit and analyze the data with the Black evaporation model. The Black evaporation model is as follows:

[0022] E=F+Bt 0 1 / 2

[0023] Where, E is the cumulative evaporation (g); t 0 is the evaporation duration (h); F and B are evaporation parameters;

[0024] Step S5: Step S5: Plot the data obtained by the Black evaporation model in step S4 into a curve chart showing the change of moisture content of high-moisture tailings soil over time at different lime dosages to optimize the lime dosage.

[0025] The method for making the high-water content tailings soil roadbed material of the present invention, the basic performance parameters of the high-water content tailings soil for road use, the maximum particle size is not more than 4.75mm;

[0026] The mass fraction of particles with a particle size below 0.075 mm is greater than 60%, the plasticity index is 17 to 19, and the organic matter content is less than 5%.

[0027] The mineral phase components of the high-water content tailings soil of the present invention are as follows: the various minerals in the tailings soil include dolomite (CaMg(CO3)2) 18-22%, siderite (FeCO3) 18-22%, quartz (SiO2) 15-16%, calcite (CaCO3) 12-13%, hematite (Fe2O3) 11-12%, kaolinite (Al4[Si4O10](OH)8) 9-10%, muscovite (KAl2[AlSi3010](OH)2) 8-9% and pyrite (FeS2) 2-3%.

[0028] The method for preparing the high-water content tailings soil roadbed material of the present invention has a leaching concentration of copper element in the high-water content tailings soil used for the test less than 26.77 μg / L, barium element less than 61.61 μg / L, chromium element less than 2.28 μg / L, cadmium element less than 2.28 μg / L, and lead element less than 0.20 μg / L.

[0029] The method for preparing the high-water content tailings soil roadbed material of the present invention and the high-water content tailings soil roadbed material prepared by the preparation method are used for roads of main roads, secondary roads and urban roads of the following levels.

[0030] The method for preparing the high-water content tailings soil roadbed material of the present invention is as follows: the road layers in which the high-water content tailings soil roadbed material prepared by the preparation method is applied are upper and lower roadbed layers and lower bearing layers.

[0031] The method for preparing the high-water content tailings soil roadbed material of the present invention is characterized in that the lime in the roadbed material is quicklime, the grade of which is grade II lime or above; and the cement is ordinary Portland cement, the grade of which is 42.5 or above.

[0032] Beneficial Effects

[0033] 1. The present invention uses quicklime to pre-treat the high-water content tailings soil, which is more feasible in large-scale industrial production than the laboratory drying method. At the same time, the present invention directly addresses the engineering problem of high water content of tailings soil, and is more in line with actual engineering needs than the ideal environment of the laboratory.

[0034] 2. The present invention uses tailings soil to completely replace clay and sand in traditional processes, and the recycling rate of tailings soil is higher. Compared with the prior art, the present invention can more effectively alleviate the pollution of tailings soil accumulation to the environment, and also solve the problem of shortage of high-quality road construction resources, reduce the mining of natural gravel, and has good environmental benefits.

[0035] 3. From an economic point of view, tailings soil is solid waste generated during mineral processing. Except for the transportation cost, the rest of the cost for road construction is basically zero. At the same time, the pretreatment process of precipitation with quicklime is cheaper than the existing large-scale drying method, which can effectively reduce the cost of road construction and has good economic benefits.

[0036] Compared with the traditional lime and cement composite stabilized clay, the tailings soil roadbed material proposed in the present invention has a higher California bearing ratio and has a better bearing capacity after the roadbed layer is paved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a curve diagram showing the change of moisture content of tailings soil with high moisture content over time at different lime dosages;

[0038] Figure 2 Schematic diagram of the California bearing ratio test for high water content tailings soil roadbed materials;

[0039] Figure 3 The figure is a bar chart of the California bearing ratio of high moisture content tailings soil roadbed materials at different mix ratios. DETAILED DESCRIPTION

[0040] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0041] The tailings soil used in the present invention is iron tailings soil in a tailings pond in a certain area, which is collected on site and then sealed.

[0042] Embodiment 1:

[0043] This embodiment provides an implementation scheme of a preferred lime dosage, which mainly includes: tailings soil with a moisture content of 35%, and lime with a mass of 10% of the dry tailings soil; the preparation method of the material and data includes the following steps:

[0044] Step S1: crush the original high-water content tailings soil and measure its initial water content w 0 35%;

[0045] Step S2: Add 10% of the dry tailings soil mass of lime to the tailings soil with high moisture content and mix thoroughly to obtain the optimum moisture content w obtained by the compaction test of common clay soil. opt is the preset moisture content w set , generally set below 14% to basically meet the requirements. In this test, the preset moisture content w set 14%;

[0046] Step S3: Perform static precipitation for 4 days, a total of 96 hours, during which the moisture content is measured every 12 hours, and the moisture content on the surface of the tailings pile and the moisture content inside the tailings pile are measured respectively, and the average value is taken as the moisture content data;

[0047] Step S4: Arrange the measured data. The moisture content decline curve of high-water content tailings soil should follow the basic soil evaporation theory. The Black evaporation model is used to fit and analyze the data. If the significance test fails, it is necessary to re-test to obtain data. The Black evaporation model is as follows:

[0048] E=F+Bt 0 1 / 2

[0049] Where, E is the cumulative evaporation (g); t 0 is the evaporation duration (h); F and B are evaporation parameters;

[0050] Step S5: Plot the tested data into a curve chart showing the change of moisture content of high moisture tailings soil over time at different lime dosages to optimize the lime dosage.

[0051] Comparative Example 1:

[0052] The difference from Example 1 is that the lime added in Comparative Example 1 is 4% of the mass of dry tailings soil, and the rest is the same as Example 1, and the required materials and data are prepared in the same way.

[0053] Comparative Example 2:

[0054] The difference from Example 1 is that the lime added in Comparative Example 1 is 6% of the mass of dry tailings soil, and the rest is the same as Example 1, and the required materials and data are prepared in the same way.

[0055] Comparative Example 3:

[0056] The difference from Example 1 is that the lime added in Comparative Example 1 is 8% of the mass of dry tailings soil, and the rest is the same as Example 1, and the required materials and data are prepared in the same way.

[0057] Comparative Example 4:

[0058] The difference from Example 1 is that the lime added in Comparative Example 1 is 12% of the mass of dry tailings soil, and the rest is the same as Example 1, and the required materials and data are prepared in the same way.

[0059] The curve graphs including Example 1 and Comparative Examples 1 to 4 are analyzed, and it is preferred that the water content w is reduced to the preset water content w within 96 hours. set The lime addition scheme, the test results are as follows Figure 1As shown in the test results, both Example 1 and Comparative Example 4 reduced the moisture content to below 14% within 96 hours, 13.4% and 12.5% ​​respectively. The lowest cost and the smallest lime dosage were further optimized. Finally, the best lime dosage in this test was 10% in Example 1.

[0060] In addition, when the subsequent compaction test results show that the optimum moisture content w opt The water content w is still set set If the water content w is below , the preset water content w should be reset based on step S2. set , and increase the lime dosage to 14% of the dry tailings soil mass. At the same time, the test time is extended based on step S3, and can be added to 120h at most. The rest are prepared according to the same steps as in Example 1, and the water content w is selected again. set Optimal lime dosage.

[0061] Embodiment 2:

[0062] This embodiment provides an implementation scheme of a preferred cement dosage, which mainly includes: tailings soil with a moisture content of less than 14% and containing 10% of reacted lime, and cement with a mass of 6% of the dry tailings soil; the preparation method of the material and data includes the following steps:

[0063] Step S1: crush the tailings soil after lime reaction, add 6% cement of dry tailings soil and 1%, 2%, 3%, 4% water of dry tailings soil, and conduct compaction test after sufficient mixing to measure the optimal moisture content w opt is 15.2%, the maximum dry density ρ dmax 1.81 g / cm 3 ;

[0064] Step S2: According to the optimal moisture content w opt and the maximum dry density ρ dmax , add 4% cement and 1.8% water of dry tailings soil mass, mix and compact thoroughly, and then conduct California bearing ratio test;

[0065] Step S3: Record the California bearing ratio test results and plot them into a California bearing ratio bar chart of high-water content tailings soil roadbed materials under different mix ratios to optimize cement dosage.

[0066] Comparative Example 5:

[0067] Different from Example 2, no cement was added in Comparative Example 5, and the optimal moisture content w was measured. opt and the maximum dry density ρ dmax They are 14.7% and 1.84 g / cm 3, the rest is the same as Example 2, and the required materials are prepared in the same way.

[0068] Comparative Example 6:

[0069] Different from Example 2, in Comparative Example 6, cement with a mass percentage of 2% of the dry tailings soil is added, and the optimum moisture content w is measured. opt and the maximum dry density ρ dmax 15.7% and 1.79g / cm 3 , the rest is the same as Example 2, and the required materials are prepared in the same way.

[0070] Comparative Example 7:

[0071] Different from Example 2, in Comparative Example 7, cement with a mass percentage of 4% of the dry tailings soil was added, and the optimum moisture content w was measured. opt and the maximum dry density ρ dmax 14.6% and 1.77g / cm 3 , the rest is the same as Example 2, and the required materials are prepared in the same way.

[0072] Comparative Example 8:

[0073] Different from Example 2, in Comparative Example 8, cement with a mass percentage of 8% of the dry tailings soil was added, and the optimum moisture content w was measured. opt and the maximum dry density ρ dmax They are 14.9% and 1.82 g / cm 3 , the rest is the same as Example 2, and the required materials are prepared in the same way.

[0074] Comparative Example 9:

[0075] Different from Example 2, in Comparative Example 9, cement with a mass of 10% of the dry tailings soil was added, and the optimal moisture content w was measured. opt and the maximum dry density ρ dmax They are 14.3% and 1.81 g / cm 3 , the rest is the same as Example 2, and the required materials are prepared in the same way.

[0076] Comparative Example 10:

[0077] The difference from Example 2 is that in Comparative Example 10, the traditional clay was treated with 6% lime ash reaction, and the best moisture content w was measured. opt and the maximum dry density ρ dmax 15.2% and 1.73g / cm 3 , the rest is the same as Example 2, and the required materials are prepared in the same way.

[0078] The tests described in Example 2 and Comparative Examples 5 to 10 all meet the California load ratio test method (T0134-1993) in the "Test Procedure for Inorganic Binder Stabilized Materials for Highway Engineering" (JTGE51-2009). The test results are as follows: Figure 2 shown.

[0079] The column charts including Example 2 and Comparative Examples 5 to 10 were analyzed to optimize the cement addition scheme. The test results are as follows: Figure 3 As shown. It can be seen from the test results that compared with the traditional lime-soil roadbed process of Comparative Example 10, the California bearing ratios of Example 2, Comparative Examples 8 and 9 are higher. At the same time, when the cement content does not exceed 6% of the dry tailings soil mass, the more cement content, the higher the California bearing ratio of the material; when the cement content exceeds 6% of the dry tailings soil mass, the more cement content, the lower the California bearing ratio of the material. Therefore, with the maximum bearing capacity as the preferred principle, the optimal cement content of this test is 6% in Example 2.

[0080] With the above-mentioned ideal embodiments of the present invention as inspiration, through the above-mentioned description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

[0081] The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. For those skilled in the art, without departing from the principle of the present invention, according to actual use needs, certain improvements can be made, and such improvements should be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a high-water content tailings soil roadbed material, characterized in that: The roadbed materials include tailings soil with high moisture content, lime, cement, and water; The production steps are as follows: Step S1: crushing the tailings soil with high water content and measuring its initial water content w0; Step S2: After the tailings soil with high water content and lime in different mass ratios are fully mixed, a lime precipitation test is performed to preset the water content w set Determine the best lime dosage as the main control index; Step S3: crush the tailings soil after lime reaction, mix it with cement and water in different mass ratios, and then conduct compaction test to measure the optimal moisture content w under different cement dosages. opt and the maximum dry density ρ dmax ; Step S4: According to the optimal moisture content w opt and the maximum dry density ρ dmax , after the tailings soil after lime reaction, cement and water are fully mixed and compacted according to different cement dosages, the California bearing ratio test is carried out to select the best cement dosage; Step S5: Determine the mix ratio of the roadbed material according to the optimal lime content, the optimal moisture content and the optimal cement content, and produce the high moisture content tailings soil roadbed material.

2. The method for making a high-water content tailings soil roadbed material according to claim 1, characterized in that: The test method for high water content tailings soil roadbed includes the following steps: Step S1: crushing the tailings soil with high water content and measuring its initial water content w0; Step S2: Add lime of different mass ratios into the tailings soil with high water content and mix thoroughly to obtain the optimum water content w obtained by the compaction test of common clay soil. opt is the preset moisture content w set ; Step S3: Perform static precipitation for 4 days, a total of 96 hours, during which the moisture content is measured every 12 hours, and the moisture content on the surface of the tailings pile and the moisture content inside the tailings pile are measured respectively, and the average value is taken as the moisture content data; Step S4: Arrange the data obtained in step S3 and fit the data with the Black evaporation model. The Black evaporation model is as follows: E=F+Bt0 1 / 2 Where, E is the cumulative evaporation amount (g); t0 is the evaporation duration (h); F and B are evaporation parameters; Step S5: Plot the data obtained by the Black evaporation model in step S4 into a curve chart showing the change of moisture content of high-moisture tailings soil over time at different lime dosages to optimize the lime dosage.

3. The method for making the high-water content tailings soil roadbed material according to claim 1, characterized in that: Basic performance parameters of high-water content tailings soil for road use: maximum particle size is no more than 4.75mm; The mass fraction of particles with a particle size below 0.075 mm is greater than 60%, the plasticity index is 17 to 19, and the organic matter content is less than 5%.

4. The method for making the high-water content tailings soil roadbed material according to claim 2, characterized in that: The leaching concentration of copper in the high-water content tailings soil used in the test was less than 26.77μg / L, barium less than 61.61μg / L, chromium less than 2.28μg / L, cadmium less than 2.28μg / L, and lead less than 0.20μg / L.

5. The method for making the high-water content tailings soil roadbed material according to claim 1, characterized in that: The high-water content tailings soil roadbed material prepared by the manufacturing method is used for road types and grades such as main roads, secondary roads and urban roads of the following levels.

6. The method for making the high-water content tailings soil roadbed material according to claim 1, characterized in that: The road layers used for the tailings soil roadbed material with high water content prepared by the manufacturing method are upper and lower roadbed layers and lower bearing layers.

7. The method for making the high-water content tailings soil roadbed material according to claim 1, characterized in that: The lime in the roadbed material is quicklime, and the grade is Grade II lime or above; The cement is ordinary Portland cement with a grade of 42.5 or above.

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