Method for analyzing the effect of fiber on the compression toughness of tailings cemented filling body

Abstract

An analytical method for enhancing the compressive toughness of cemented tailings backfill includes preparing specimens of cemented tailings backfill without fibers and specimens of cemented tailings backfill with different fibers. Uniaxial compression tests are conducted on each specimen, and load-displacement curves are plotted. The compressive toughness index is defined as the ratio of the area enclosed by the curve and the horizontal axis at the ultimate load to the area enclosed at the peak load. The compressive toughness index of the cemented tailings backfill specimen is then calculated. A specimen of cemented tailings backfill without fibers serves as a control group. The percentage enhancement of compressive toughness is calculated as the load ratio between the fiber-loaded cemented tailings backfill specimen and the control group. This invention can fully characterize the post-peak load ductility characteristics of cemented tailings backfill and can quickly and accurately analyze the enhancing effect of different fibers on the compressive toughness of cemented tailings backfill. This provides a theoretical basis for metal mines to adopt suitable backfill materials and ensure the safety of tailings backfill engineering, while also improving the utilization rate of tailings in metal mines.

Description

Technical Field

[0001] This invention belongs to the field of tailings treatment methods for metal mines, specifically involving an analytical method for enhancing the compressive toughness of fiber-bonded tailings backfill. Background Technology

[0002] Tailings left over from metal mining pollute the environment. Tailings cemented backfilling is a preferred mining method because it achieves green mining and improves the utilization rate of mineral resources. Therefore, the mechanical properties of tailings cemented backfill are crucial. Admixtures are a common method to enhance tailings cemented backfill. For example, incorporating artificial fibers into tailings cemented backfill addresses its brittleness and cracking susceptibility, improving its practicality. Research on the reinforcing effects of different fiber types, contents, and lengths on tailings cemented backfill determines the optimal parameters for fiber reinforcement. In the field of fiber-reinforced materials, the compressive toughness of fiber-reinforced concrete in construction engineering is defined as the ratio of the area enclosed by the curves at peak load and crack initiation load to the horizontal axis.

[0003] However, in the existing technology, neither the bending toughness is used to characterize the toughness enhancement effect of different fibers on the tailings cemented infill body, nor the compressive toughness of fiber-reinforced concrete is defined, which cannot objectively characterize the compressive toughness of the fiber on the tailings cemented infill body. This is because the post-peak bearing capacity of the fiber-reinforced tailings cemented infill body is an important property characterizing its strength and toughness, and the post-peak ductile deformation stage of the fiber-reinforced tailings cemented infill body cannot be ignored. Summary of the Invention

[0004] To address the shortcomings of the prior art, this invention provides a method for analyzing the compressive toughness enhancement effect of fibers on cemented tailings backfill by defining the compressive toughness index as the ratio of the area enclosed by the curve and the horizontal axis at ultimate load to the area enclosed at peak load. This method can quickly and accurately analyze the enhancing effect of different fibers on the compressive toughness of cemented tailings backfill, improve the utilization rate of tailings in metal mines, and provide a scientific reference for ensuring the safety of tailings backfill engineering.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An analytical method for enhancing the compressive toughness of cemented tailings backfill includes the following steps:

[0007] Step 1: Prepare tailings cemented backfill specimens. The tailings cemented backfill specimens include non-fiber tailings cemented backfill specimens and fiber tailings cemented backfill specimens. The fiber tailings cemented backfill specimens include glass fiber tailings cemented backfill specimens, polyacrylonitrile fiber tailings cemented backfill specimens, and glass fiber and polyacrylonitrile fiber mixed tailings cemented backfill specimens.

[0008] Step 2: Conduct uniaxial compression tests on the tailings cemented backfill specimens described in Step 1 and plot load-displacement curves for each specimen.

[0009] Step 3: Define and calculate the compressive toughness index of the tailings cemented backfill specimen;

[0010] Toughness is a key indicator characterizing the post-peak load-bearing ductility of infill materials, and also an important property representing the fracture energy absorbed by the infill material from initial compression to failure. In research in the field of building engineering, the compressive toughness index of fiber-reinforced concrete is defined as the ratio of the area enclosed by the curves at peak load and crack initiation load to the horizontal axis. However, this is not suitable for fiber-reinforced infill materials because the post-peak load-bearing capacity of fiber-reinforced infill materials is an important property characterizing their strength and toughness, and the post-peak ductile deformation stage of fiber-reinforced infill materials cannot be ignored. Therefore, in order to quantitatively analyze the compressive toughness of infill materials under the influence of different fibers, the compressive toughness index TI is defined as:

[0011] TI=(A1+A2) / A1 (1)

[0012]

[0013] In the formula: F(X) represents the functional expression of the load-displacement curve; A1 and A2 are the definite integral values ​​of F(X) in the intervals [0, Xm] and [Xm, Xp], respectively, i.e., the areas; Xm and Xp represent the displacement values ​​corresponding to the peak value Pmax and the ultimate load Pp, respectively.

[0014] Step 4: Calculate the maximum load and compressive toughness index of the tailings cemented backfill specimen described in Step 1. Using the fiberless tailings cemented backfill specimen as the control group, calculate the load ratio and the increase rate of the compressive toughness index of the fiber tailings cemented backfill specimen compared to the control group.

[0015] Furthermore, the tailings cemented backfill specimen described in step one is made from a cementing material with a mass fraction of 68% and a tailings-cement ratio of 1:6 or / and 1:10.

[0016] Furthermore, the fiber length in the fiber tailings cemented filling specimen is 12 mm.

[0017] Furthermore, the uniaxial compression test described in step two adopts a loading strain test with a loading rate of 0.5 mm / min until the specimen fails and the loading is stopped.

[0018] The beneficial effects of this invention are:

[0019] The compressive toughness of the fiber-bonded tailings backfill defined in this invention can fully characterize the post-peak load-bearing ductility of the backfill. It can quickly and accurately analyze the enhancing effect of different fibers on the compressive toughness of the backfill, providing a theoretical basis for metal mines to adopt suitable backfill and ensure the safety of tailings backfill engineering, and improving the utilization rate of tailings in metal mines. Attached Figure Description

[0020] Figure 1 This is a diagram showing the calculation relationship of the compressive toughness index in an embodiment of the present invention;

[0021] Figure 2 This is a load-displacement relationship diagram of the tailings cemented backfill specimen in an embodiment of the present invention;

[0022] Figure 3 This is a graph showing the maximum load percentage of the fiber tailings cemented backfill specimen compared to the control group in an embodiment of the present invention. Detailed Implementation

[0023] The fiber-reinforced tailings cemented backfill specimen in this embodiment consists of tailings, cement, and fibers. The tailings were selected from a tailings dam of a gold mine in Henan Province. The cement used was composite silicate cement with the code P.C32.5. The fibers were of three types: glass fiber, polyacrylonitrile fiber, and a mixture of glass fiber and polyacrylonitrile fiber.

[0024] An analytical method for enhancing the compressive toughness of cemented tailings backfill includes the following steps:

[0025] Step 1: Prepare tailings cemented backfill specimens;

[0026] Using a tailings cemented backfill with a mass concentration (solid concentration) of 68% and a ash-to-sand ratio of 1:6, fiberless tailings cemented backfill (sample number: N-6), glass fiber tailings cemented backfill (B-6), polyacrylonitrile fiber tailings cemented backfill (J-6), and a glass fiber and polyacrylonitrile mixed fiber tailings cemented backfill (H-6) were prepared. Using a tailings cemented backfill with a mass concentration of 68% and an ash-to-sand ratio of 1:10, fiberless tailings cemented backfill (N-10), glass fiber tailings cemented backfill (B-10), polyacrylonitrile fiber tailings cemented backfill (J-10), and a glass fiber and polyacrylonitrile mixed fiber tailings cemented backfill were prepared. The mixed fiber-reinforced tailings cemented backfill (H-10) was prepared by mixing fiber, cement, tailings, and water in the above proportions. The fiber length was selected as the optimal length for inclusion in the backfill based on relevant research. To prevent fiber floating, a dry mixing method was used, adding the fiber at the beginning of mixing and stirring for 10 minutes to obtain a homogeneous backfill mixture with the required slump. Eight sets of molds with dimensions of 70.7mm×70.7mm×70.7mm (length×width×height) were made. Based on the actual conditions of the mine, the demolded tailings cemented backfill specimens were cured for 7 days in a natural environment with a relative humidity of 95±5% and a temperature of 20±5℃.

[0027] Step 2: Conduct uniaxial compression tests on the tailings cemented backfill specimens described in Step 1, and plot the load-displacement curves of the tailings cemented backfill specimens respectively.

[0028] Load-displacement curves were plotted for uniaxial compression tests on the above eight groups of tailings cemented backfill specimens. The uniaxial compression tests employed a loaded strain test with a loading rate of 0.5 mm / min (this loading rate effectively represents the mechanical properties of fiber-reinforced backfill compared to non-fiber-reinforced backfill, such as maximum load-bearing capacity and compressive toughness). Loading was stopped when the specimen failed. Specimens numbered N-6 (control group), B-6, J-6, H-6, and N-10 (control group), B-10, J-10, and H-10 respectively represent non-fiber tailings cemented backfill with a ash-sand ratio of 1:6 and 1:10, glass fiber tailings cemented backfill, polyacrylonitrile fiber tailings cemented backfill, and a mixture of glass fiber and polyacrylonitrile fiber tailings cemented backfill. Figure 1As shown, the maximum load that the fiber-bonded tailings backfill specimens can withstand is higher than that of the non-fiber-bonded tailings backfill specimens, and the higher the ash-sand ratio, the greater the increase in maximum load. This indicates that adding fiber to the tailings backfill greatly improves the stability of the internal structure of the tailings backfill. Among them, when the cement-sand ratio is 1:6, the maximum load of N-6 is 4.162 kN, and the maximum loads of B-6, J-6, and H-6 are 6.562 kN, 5.659 kN, and 6.823 kN respectively, which are 57.66%, 35.97%, and 63.94% higher than those of the fiberless tailings cemented backfill. When the cement-sand ratio is 1:10, the maximum loads of B-10, J-10, and H-10 are 3.501 kN, 2.779 kN, and 3.246 kN respectively, which are 40.49%, 11.52%, and 30.26% higher than the maximum load of the fiberless tailings cemented backfill (N-10) (2.492 kN). Therefore, compared with polyacrylonitrile fiber, glass fiber can better enhance the load-bearing capacity of tailings cemented backfill. Meanwhile, the curves of the tailings cemented infill from loading to failure were divided into four stages: compaction, elasticity, plasticity, and post-peak decline. In the compaction to elastic stage, the fiber-reinforced infill showed no obvious "upward concavity," indicating that the initial defects of the fiber-reinforced tailings cemented infill were fewer than those of the non-fiber-reinforced tailings cemented infill. Compared to the non-fiber-reinforced tailings cemented infill, the curve decline of the fiber-reinforced tailings cemented infill was more gradual after reaching the maximum load, but it never dropped to zero, demonstrating that the tailings cemented infill possessed a certain load-bearing capacity after the peak. The curve of the polyacrylonitrile fiber-reinforced tailings cemented infill showed a longer ductile deformation characteristic after the peak, indicating that polyacrylonitrile fibers could better enhance the compressive toughness of the tailings cemented infill compared to glass fibers.

[0029] Step 3: Define and calculate the compressive toughness index of the tailings cemented backfill;

[0030] like Figure 2 As shown, the compressive toughness index (TI) is defined as:

[0031] TI=(A1+A2) / A1 (1)

[0032]

[0033] In the formula: F(X) represents the function expression of the load-displacement curve of each specimen; A1 and A2 are the definite integral values ​​of F(X) in the intervals [0, Xm] and [Xm, Xp], respectively, i.e., the areas; Xm and Xp represent the displacement values ​​corresponding to the peak value Pmax and the ultimate load Pp, respectively.

[0034] Step 4, as follows Figure 3As shown, using the fiberless tailings cemented backfill specimen as the control group, the load ratio of the fiber-reinforced tailings cemented backfill specimen described in step one to the load ratio of the control group was calculated to obtain the percentage enhancement effect of fiber on the compressive toughness of the tailings cemented backfill.

[0035] The compressive toughness index (TI) of the tailings cemented backfill was calculated and is shown in Table 1. When the ash-sand ratio was 1:6, compared with the control group (N-6), the TI value of the polyacrylonitrile fiber backfill was the largest, with an improvement rate of 101.33%. When the ash-sand ratio was 1:10, compared with the control group (N-10), the TI value of the mixed fiber backfill was the largest, with an improvement rate of 118.68%. This indicates that polyacrylonitrile fiber is more suitable than glass fiber in enhancing the compressive toughness of tailings cemented backfill, providing a scientific reference for ensuring the safety of tailings backfill engineering and improving the utilization rate of tailings in metal mines. In addition, glass fiber can also improve the compressive toughness of the backfill, but the improvement rate decreases rapidly with the increase of the ash-sand ratio.

[0036] Table 1. Compression toughness index and improvement rate of cemented tailings backfill

[0037]

[0038] This invention defines the compressive toughness index of fiber-reinforced tailings cemented backfill by the ratio of the area enclosed by the curves at ultimate load and peak load to the horizontal axis. It analyzes the enhancing effect of different types of fibers on the compressive toughness of tailings cemented backfill, providing a rapid and accurate theoretical reference for construction units when using fiber-reinforced backfill for engineering support and backfilling. The above-disclosed embodiments are merely preferred embodiments of the invention and should not be construed as limiting the scope of the invention. Therefore, equivalent variations made within the scope of this invention are still within its coverage.

Claims

1. An analytical method for enhancing the compressive toughness of cemented tailings backfill, characterized in that, Includes the following steps: Step 1: Prepare tailings cemented backfill specimens. The tailings cemented backfill specimens include non-fiber tailings cemented backfill specimens and fiber tailings cemented backfill specimens. The fiber tailings cemented backfill specimens include glass fiber tailings cemented backfill specimens, polyacrylonitrile fiber tailings cemented backfill specimens, and glass fiber and polyacrylonitrile fiber mixed tailings cemented backfill specimens. Step 2: Conduct uniaxial compression tests on the tailings cemented backfill specimens described in Step 1 and plot load-displacement curves for each specimen. Step 3: Define and calculate the compressive toughness index of the tailings cemented backfill specimen; The compressive toughness index TI is defined as: TI=(A1+A2) / A1 (1) In the formula: F(X) represents the functional expression of the load-displacement curve; A1 and A2 are the values ​​of F(X) in the interval [0, X]. m ] and [X m X p The definite integral value within ], i.e., the area; X m With X p They represent the peak value P respectively. max With ultimate load P p The corresponding displacement value; Step 4: Calculate the maximum load and compressive toughness index of the tailings cemented backfill specimen described in Step 1. Using the fiberless tailings cemented backfill specimen as the control group, calculate the load ratio and the increase rate of the compressive toughness index of the fiber tailings cemented backfill specimen compared to the control group.

2. The analytical method for enhancing the compressive toughness of tailings cemented backfill bodies according to claim 1, characterized in that, The tailings cemented backfill specimens described in step one are made from cementing materials with a mass fraction of 68% and a tailings to cement ratio of 1:6 or / and 1:

10.

3. The analytical method for enhancing the compressive toughness of tailings cemented backfill bodies according to claim 1, characterized in that, The fiber length in the fiber-bonded tailings filler specimen is 12 mm.

4. The analytical method for enhancing the compressive toughness of tailings cemented backfill bodies according to claim 1, 2, or 3, characterized in that, The uniaxial compression test described in step two adopts a loading strain test with a loading rate of 0.5 mm / min until the specimen fails and the loading is stopped.

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