Paste filling material as well as preparation method and application thereof

Abstract

The invention relates to a paste filling material as well as a preparation method and application thereof, and belongs to the technical field of filling materials. The paste filling material provided by the invention is prepared from the following components in parts by weight: 20 to 30 parts of cement, 50 to 60 parts of coal gangue and 15 to 25 parts of mine water, the coal gangue comprises coarse-fraction coal gangue and fine-fraction coal gangue, the particle size of the coarse-fraction coal gangue is 5mm-20mm, and the particle size of the fine-fraction coal gangue is 1t; the mass ratio of the coarse-fraction coal gangue to the fine-fraction coal gangue is (6: 4)-(9: 1); meanwhile, an aggregate model conforming to specific particle size distribution is generated in a programmed mode through a Python script, and proper particle size distribution is designed. According to the paste filling material disclosed by the invention, wastes such as coal gangue and mine water are used, so that the utilization rate of the wastes is high, and the integration of mining, filling and discharging is realized, namely coal mining, filling and mine water recycling are synchronously carried out.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of filling materials, and particularly relates to a paste filling material and a preparation method and application thereof. BACKGROUND

[0002] A large amount of coal gangue and mine water is generated in the process of coal mining and washing and selecting, and the large accumulation of coal gangue and the direct discharge of mine water cause serious pollution to water sources, soil, air and ecological environment. At the same time, the large-scale mining of coal causes ground subsidence and loss of groundwater resources. The use of filling mining technology to improve the recovery rate of mineral resources is one of the effective ways to solve resource shortage. With the advancement of the stoping working face, coal mining technology of filling gangue, fly ash, construction waste and special filling materials into the goaf has been developed. In recent years, some coal mining enterprises have actively explored and implemented various filling process technologies such as coal gangue and other solid material filling, paste material filling and high-water material filling. The paste filling material is prepared by mixing coarse aggregate, fine aggregate, cementing material (usually cement) and water in a certain proportion.

[0003] However, the current mine filling material has defects such as high cost, low filling efficiency, low strength and slow setting speed. The treatment process of mine water is complex and costly. Based on this, researchers have conducted a lot of research on the treatment of coal gangue and mine water. Chinese patent CN113250744A discloses the application of a coal-based solid waste filling material in filling and repairing mine tunnels. The preparation raw materials include fly ash, desulfurization gypsum, cement, additives, coal gangue aggregate and water. The filling material needs to use alkali activator, water reducing agent and water retaining agent and other additives. Although good compressive strength can be achieved after 3 days, the setting speed is slow and the early strength is not ideal. Patent CN107619249A discloses a mine filling material, which includes the following components: cementing material, coal gangue aggregate, additive and water; wherein the cementing material includes silicon-calcium slag, fly ash, desulfurization gypsum and cement. The filling material also needs to use multiple additives, and also has the defects of slow setting speed and unsatisfactory early strength. To speed up the setting speed and improve the early strength, some filling materials will choose to add a large amount of early strength agent, accelerator and alkali activator and other additives, but this approach will affect the later compressive strength and also easily cause a large increase in cost. In addition, the mixing water of the filling material is all water, which also increases the degree of water resource shortage in arid and semi-arid areas, and limits the application of paste filling material. At the same time, the treatment cost of mine water is high and the process is complex, which limits the local adaptation of mine water.

[0004] Therefore, it is urgent to find a mine filling material with low cost, high compressive strength and good retention, and to recycle mine water and coal gangue, so as to save water resources, treat mine water and coal gangue underground and realize on-site reuse, which has important industrial and social significance. SUMMARY

[0005] The present application aims to overcome the problems in the prior art and provide a paste filling material and a preparation method and application thereof.

[0006] The present application is implemented by the following technical solutions: In a first aspect, the present application provides a paste filling material, which comprises the following components in parts by weight: cement 20-30 parts, coal gangue 50-60 parts, and mine water 15-25 parts; the coal gangue comprises coarse-grained coal gangue and fine-grained coal gangue, the particle size of the coarse-grained coal gangue is 5-20 mm, the particle size of the fine-grained coal gangue is <5 mm, and the mass ratio of the coarse-grained coal gangue to the fine-grained coal gangue is 6:4-9:1.

[0007] The present application uses coal gangue with different particle sizes, in which the coarse-grained coal gangue particles form a skeleton, and the fine-grained coal gangue particles are filled in the gaps of the skeleton to form a dense skeleton structure. The present application further uses mine water to fully utilize sulfate and chloride ions in the mine water, which can act as activators of coal gangue to promote the hydration reaction of SiO2 and Al2O3 and other potentially active substances in the coal gangue to generate hydraulic substances, so that the paste filling material has excellent setting performance and mechanical properties, and can maintain high compressive strength in the early and late stages, with high strength and good durability.

[0008] In some embodiments, the paste filling material comprises the following components in parts by weight: cement 24.85 parts, coal gangue 53.85 parts, and mine water 21.3 parts.

[0009] Preferably, the mass ratio of the coarse-grained coal gangue to the fine-grained coal gangue is 6:4-8:2.

[0010] Preferably, the mass ratio of the coarse-grained coal gangue to the fine-grained coal gangue is 7:3-8:2.

[0011] The present application researches and finds that the combination of coarse-grained coal gangue and fine-grained coal gangue in the above mass ratio range can make the filling material have more excellent strength and durability.

[0012] Preferably, the coal gangue has a grading of A:B:C:D:E:F:G:H:I=(0.6-3):(0.15-0.8):(0.5-2.5):(0.5-3.5):(1.5-7):(1-4.5):(5-25):(35-55):(20-40); A, B, C, D, E, F, G, H, I are coal gangue particle size gradients, and satisfy: A<0.074mm, 0.074≤B<0.1mm, 0.1≤C<0.2mm, 0.2≤D<0.5mm, 0.5≤E<1.25mm, 1.25≤F<2mm, 2≤G<5mm, 5≤H<10mm, 10≤I≤20mm.

[0013] More preferably, the coal gangue has a grading of A:B:C:D:E:F:G:H:I=(1-2):(0.3-0.6):(1-2):(1-3):(3-5):(2-4):(10-20):(40-50):(25-35); A, B, C, D, E, F, G, H, I are coal gangue particle size gradients, and satisfy: A<0.074mm, 0.074≤B<0.1mm, 0.1≤C<0.2mm, 0.2≤D<0.5mm, 0.5≤E<1.25mm, 1.25≤F<2mm, 2≤G<5mm, 5≤H<10mm, 10≤I≤20mm.

[0014] Further, the coal gangue has a grading of A:B:C:D:E:F:G:H:I=(1.5-2):(0.5-0.6):(1.5-2):(2-3):(4-5):(3-4):(15-20):(40-45):(25-30); A, B, C, D, E, F, G, H, I are coal gangue particle size gradients, and satisfy: A<0.074mm, 0.074≤B<0.1mm, 0.1≤C<0.2mm, 0.2≤D<0.5mm, 0.5≤E<1.25mm, 1.25≤F<2mm, 2≤G<5mm, 5≤H<10mm, 10≤I≤20mm.

[0015] Preferably, the content of silicate in the cement is 40%-45%.

[0016] In some embodiments, the content of silicate in the cement is 42.5%.

[0017] Preferably, the total content of SiO2 and Al2O3 in the coal gangue is 80%-90%.

[0018] In some embodiments, the total content of SiO2 and Al2O3 in the coal gangue is 86.9%.

[0019] Preferably, the total content of SO4 2- and Cl - in the mine water is 1000 mg / L-1200 mg / L.

[0020] In some embodiments, the total content of SO4 2- and Cl - in the mine water is 1158 mg / L.

[0021] Preferably, a three-dimensional aggregate packing model conforming to the particle size gradation of the coal gangue is generated by using a Python script, and the packing body of the coal gangue is visualized and quantitatively analyzed by finite element calculation.

[0022] In the second aspect, the application provides a preparation method of the paste filling material, comprising the following steps: uniformly mixing components according to the weight fractions, and obtaining the paste filling material.

[0023] The preparation method of the paste filling material is simple, and the paste filling material can be directly produced and used underground, and has high application flexibility.

[0024] In some embodiments, the preparation method of the paste filling material comprises the following steps: crushing coal gangue according to the weight fractions to obtain coarse-grained coal gangue and fine-grained coal gangue with the mass ratio, adding cement and mine water according to the weight fractions, and uniformly mixing to obtain the paste filling material.

[0025] In the third aspect, the application provides application of the paste filling material or the paste filling material prepared by the preparation method of the paste filling material in mine filling.

[0026] The application has the following beneficial effects: (1) The paste filling material uses waste such as coal gangue and mine water, has high waste utilization rate, realizes harmless resource utilization and in-situ reuse of coal gangue and mine water, reduces damage to soil, underground water and the like, does not need to add external agents, greatly reduces the cost of the filling material, and still can obtain good filling effect.

[0027] (2) The paste filling material provided by the application uses mine water with high mineralization, fully utilizes sulfate and chloride ions in the mine water, and the two types of substances can be used as activators of coal gangue, can promote SiO2 and Al2O3 and other substances with potential activity to occur hydration reaction to generate hydraulic substances, and thus the paste filling material prepared has excellent coagulation performance and mechanical properties, can maintain high compressive strength in early and late stages, has good strength durability, and thus can be used as a new type of high-strength filling material.

[0028] (3) The paste filling material provided by the application can be directly produced and used in the well, the mechanical properties of the filling material can be flexibly controlled by controlling the gradation of the coal gangue aggregate, the adjustment according to different working conditions is facilitated, and the application flexibility is higher. Therefore, the paste filling material provided by the application has low cost, simple manufacturing, is suitable for large-scale production, has important economic and social values, and thus has a very good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a preparation and curing process schematic diagram of the paste filling material in the embodiment of the application. Figure 2 It is a comparison diagram of the coal gangue aggregate gradation fitting curve and the Fuller curve of Example 1. Figure 3 It is a comparison diagram of the coal gangue aggregate gradation fitting curve and the Fuller curve of Example 2. Figure 4 It is a comparison diagram of the coal gangue aggregate gradation fitting curve and the Fuller curve of Example 3. Figure 5 It is a comparison diagram of the coal gangue aggregate gradation fitting curve and the Fuller curve of Example 4. Figure 6 It is a random polygon coal gangue aggregate model of Example 1. Figure 7 It is a random polygon coal gangue aggregate model of Example 2. Figure 8 It is a random polygon coal gangue aggregate model of Example 3. Figure 9 It is a random polygon coal gangue aggregate model of Example 4. Figure 10 It is a random polygon coal gangue aggregate model of Comparative Example 1. Figure 11 It is a process schematic diagram of the application for constructing a'mining-filling-draining' integrated green mining system. DETAILED DESCRIPTION

[0030] In order to better illustrate the purposes, technical solutions and advantages of the application, the application will be further described below in combination with specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0031] Unless otherwise specified, the test methods used in the embodiments are conventional methods; and unless otherwise specified, the materials, reagents and the like used can be obtained from commercial channels.

[0032] In the following examples and comparative examples, the chemical composition of the coal gangue is as shown in Table 1: Table 1 Chemical composition of coal gangue

[0033] The water composition and properties of the mine water are shown in Table 2 below: Table 2 Composition and Properties of Mine Water

[0034] A schematic diagram of the preparation and curing process of paste filling materials is shown below. Figure 1 As shown.

[0035] Example 1 A paste-like filling material, by weight, comprises the following components: 24.85 parts cement, 53.85 parts coal gangue, and 21.3 parts mine water; wherein the coal gangue includes coarse-grained coal gangue and fine-grained coal gangue, the coarse-grained coal gangue has a particle size of 5mm-20mm, the fine-grained coal gangue has a particle size of <5mm, and the mass ratio of coarse-grained coal gangue to fine-grained coal gangue is 9:1.

[0036] The preparation method of the paste filling material includes the following steps: (1) The coal gangue is crushed into two particle sizes: coarse and fine. 5~20mm is the coarse particle size and <5mm is the fine particle size. The mass ratio of coarse coal gangue to fine coal gangue is 9:1. (2) Weigh 24.85 parts of cement, 53.85 parts of coarse and fine-grained compounded coal gangue, and 21.30 parts of mine water (the silicate content in the cement is 42.5wt%, the total SiO2 and Al2O3 content in the coal gangue is 86.9wt%, and the SO4 content in the mine water is...). 2- and Cl - The total content is 1158 mg / L. (3) Mix all components together and vibrate to obtain paste filling material.

[0037] The gradation results of coarse and fine coal gangue in this embodiment are shown in Table 3.

[0038] Table 3. Gradation results of coarse and fine coal gangue in Example 1.

[0039] The paste filling material of this embodiment was placed in a standard constant temperature and humidity curing chamber for curing. The temperature of the curing chamber was set to 20°C and the humidity to 95%. The curing was carried out for 3 days, 7 days and 28 days respectively. The uniaxial compressive strength of the specimens cured for 3 days, 7 days and 28 days was tested using an electro-hydraulic pressure testing machine. The test results are shown in Table 4.

[0040] Table 4. Uniaxial compressive strength test results of paste filling material in Example 1

[0041] The test results show that the coal gangue-mine water paste filling material of this embodiment has a dense skeleton structure formed by the coarse-grained coal gangue particles and the fine-grained coal gangue particles filling the gaps in the skeleton, which significantly improves the uniaxial compressive strength of the paste filling material. The compressive strength after 28 days can reach 8.01 MPa.

[0042] Example 2 A paste-like filling material, by weight, comprises the following components: 24.85 parts cement, 53.85 parts coal gangue, and 21.3 parts mine water; wherein the coal gangue includes coarse-grained coal gangue and fine-grained coal gangue, the coarse-grained coal gangue has a particle size of 5mm-20mm, the fine-grained coal gangue has a particle size of <5mm, and the mass ratio of coarse-grained coal gangue to fine-grained coal gangue is 8:2.

[0043] The preparation method of the paste filling material includes the following steps: (1) The coal gangue is crushed into two particle sizes: coarse and fine. 5~20mm is the coarse particle size and <5mm is the fine particle size. The mass ratio of coarse coal gangue to fine coal gangue is 8:2. (2) Weigh 24.85 parts of cement, 53.85 parts of coarse and fine-grained compounded coal gangue, and 21.30 parts of mine water (the silicate content in the cement is 42.5%, the total SiO2 and Al2O3 content in the coal gangue is 86.9%, and the SO4 content in the mine water is...). 2- and Cl - The total content is 1158 mg / L. (3) Mix all components together and vibrate to obtain paste filling material.

[0044] The gradation results of coarse and fine coal gangue in this embodiment are shown in Table 5.

[0045] Table 5. Gradation results of coarse-grained and fine-grained coal gangue in Example 2.

[0046] The paste filling material of this embodiment was placed in a standard constant temperature and humidity curing chamber for curing. The temperature of the curing chamber was set to 20°C and the humidity to 95%. The curing was carried out for 3 days, 7 days and 28 days respectively. The uniaxial compressive strength of the specimens cured for 3 days, 7 days and 28 days was tested using an electro-hydraulic pressure testing machine. The test results are shown in Table 6.

[0047] Table 6. Uniaxial compressive strength test results of paste filling material in Example 2

[0048] The test results show that the coal gangue-mine water paste filling material of this embodiment has a dense skeleton structure formed by the coarse-grained coal gangue particles and the fine-grained coal gangue particles filling the gaps in the skeleton, which significantly improves the uniaxial compressive strength of the paste filling material.

[0049] Example 3 A paste-like filling material, by weight, comprises the following components: 24.85 parts cement, 53.85 parts coal gangue, and 21.3 parts mine water; wherein the coal gangue includes coarse-grained coal gangue and fine-grained coal gangue, the coarse-grained coal gangue has a particle size of 5mm-20mm, the fine-grained coal gangue has a particle size of <5mm, and the mass ratio of coarse-grained coal gangue to fine-grained coal gangue is 7:3.

[0050] The preparation method of the paste filling material includes the following steps: (1) The coal gangue is crushed into two particle sizes: coarse and fine. 5~20mm is the coarse particle size and <5mm is the fine particle size. The mass ratio of coarse coal gangue to fine coal gangue is 7:3. (2) Weigh 24.85 parts of cement, 53.85 parts of coarse and fine-grained compounded coal gangue, and 21.30 parts of mine water (the silicate content in the cement is 42.5%, the total SiO2 and Al2O3 content in the coal gangue is 86.9%, and the SO4 content in the mine water is...). 2- and Cl - The total content is 1158 mg / L. (3) Mix all components together and vibrate to obtain paste filling material.

[0051] The gradation results of coarse and fine coal gangue in this embodiment are shown in Table 7.

[0052] Table 7. Gradation results of coarse-grained and fine-grained coal gangue in Example 3.

[0053] The paste filling material of this embodiment was placed in a standard constant temperature and humidity curing chamber for curing. The temperature of the curing chamber was set to 20°C and the humidity to 95%. The curing was carried out for 3 days, 7 days and 28 days respectively. The uniaxial compressive strength of the specimens cured for 3 days, 7 days and 28 days was tested using an electro-hydraulic pressure testing machine. The test results are shown in Table 8.

[0054] Table 8. Uniaxial compressive strength test results of paste filling material in Example 3

[0055] The test results show that the coal gangue-mine water paste filling material of this embodiment has a dense skeleton structure formed by the coarse-grained coal gangue particles and the fine-grained coal gangue particles filling the gaps in the skeleton. This significantly improves the uniaxial compressive strength of the paste filling material. The compressive strength after 28 days can reach 9.42 MPa, which is 17.6% higher than the compressive strength of the 10% fine-grained filling material in Example 1.

[0056] Example 4 A paste-like filling material, by weight, comprises the following components: 24.85 parts cement, 53.85 parts coal gangue, and 21.3 parts mine water; wherein the coal gangue includes coarse-grained coal gangue and fine-grained coal gangue, the coarse-grained coal gangue has a particle size of 5mm-20mm, the fine-grained coal gangue has a particle size of <5mm, and the mass ratio of coarse-grained coal gangue to fine-grained coal gangue is 6:4.

[0057] The preparation method of the paste filling material includes the following steps: (1) The coal gangue is crushed into two particle sizes: coarse and fine. 5~20mm is the coarse particle size and <5mm is the fine particle size. The mass ratio of coarse coal gangue to fine coal gangue is 6:4. (2) Weigh 24.85 parts of cement, 53.85 parts of coarse and fine-grained compounded coal gangue, and 21.30 parts of mine water (the silicate content in the cement is 42.5%, the total SiO2 and Al2O3 content in the coal gangue is 86.9%, and the SO4 content in the mine water is...). 2- and Cl - The total content is 1158 mg / L. (3) Mix all components together and vibrate to obtain paste filling material.

[0058] The gradation results of coarse and fine coal gangue in this embodiment are shown in Table 9.

[0059] Table 9. Gradation results of coarse and fine coal gangue in Example 4.

[0060] The paste filling material of this embodiment was placed in a standard constant temperature and humidity curing chamber for curing. The temperature of the curing chamber was set to 20°C and the humidity to 95%. The curing was carried out for 3 days, 7 days and 28 days respectively. The uniaxial compressive strength of the specimens cured for 3 days, 7 days and 28 days was tested using an electro-hydraulic pressure testing machine. The test results are shown in Table 10.

[0061] Table 10. Uniaxial compressive strength test results of paste filling material in Example 4

[0062] The test results show that the coal gangue-mine water paste filling material of this embodiment has a dense skeleton structure formed by the coarse-grained coal gangue particles and the fine-grained coal gangue particles filling the gaps in the skeleton. This significantly improves the uniaxial compressive strength of the paste filling material. However, the performance is lower than that of Example 3, indicating that the addition of too much fine-grained coal gangue aggregate will weaken the mechanical properties of the filling material at later ages.

[0063] Comparative Example 1 A paste-like filling material, by weight, comprises the following components: 24.85 parts cement, 53.85 parts coal gangue, and 21.3 parts mine water.

[0064] The preparation method of the paste filling material includes the following steps: (1) Weigh 24.85 parts of cement, 53.85 parts of coal gangue and 21.30 parts of mine water (the silicate content in the cement is 42.5%, the total SiO2 and Al2O3 content in the coal gangue is 86.9%, and the SO4 content in the mine water is 100%. 2- and Cl - The total content is 1158 mg / L. (2) Mix all components together and vibrate to obtain paste filling material.

[0065] The paste filling material of this comparative example was placed in a standard constant temperature and humidity curing chamber for curing. The temperature of the curing chamber was set at 20℃ and the humidity at 95%. The curing was carried out for 3 days, 7 days and 28 days respectively. The uniaxial compressive strength of the specimens cured for 3 days, 7 days and 28 days was tested using an electro-hydraulic pressure testing machine. The test results are shown in Table 11.

[0066] Table 11. Uniaxial compressive strength test results of the paste filling material in Comparative Example 1

[0067] The test results show that the uniaxial compressive strength of the coal gangue-mine water paste filling material in this comparative example decreased because the coal gangue was not graded into coarse and fine particles.

[0068] Comparative Example 2 A paste-like filling material, by weight, comprises the following components: 24.85 parts cement, 53.85 parts coal gangue, and 21.3 parts deionized water.

[0069] The preparation method of the paste filling material includes the following steps: (1) Weigh 24.85 parts of cement, 53.85 parts of coal gangue and 21.30 parts of deionized water (the silicate content in the cement is 42.5%, and the total content of SiO2 and Al2O3 in the coal gangue is 86.9%). (2) Mix all components together and vibrate to obtain paste filling material.

[0070] The paste filling material of this comparative example was placed in a standard constant temperature and humidity curing chamber for curing. The temperature of the curing chamber was set at 20℃ and the humidity at 95%. The curing was carried out for 3 days, 7 days and 28 days respectively. The uniaxial compressive strength of the specimens after curing for 3 days, 7 days and 28 days was tested using an electro-hydraulic pressure testing machine. The test results are shown in Table 12.

[0071] Table 12. Uniaxial compressive strength test results of the paste filling material in Comparative Example 2

[0072] The test results show that the initial uniaxial compressive strength of the coal gangue-mine water paste filling material in this comparative example decreased by 26.5% compared with Example 3 because the coal gangue was not graded into coarse and fine particles and no mine water was added. The long-term performance also decreased significantly compared with Example 3.

[0073] Comparative Example 3 A paste-like filling material, by weight, comprises the following components: 24.85 parts cement, 53.85 parts coal gangue, and 21.3 parts deionized water; wherein the coal gangue includes coarse-grained coal gangue and fine-grained coal gangue, the coarse-grained coal gangue has a particle size of 5mm-20mm, the fine-grained coal gangue has a particle size of <5mm, and the mass ratio of coarse-grained coal gangue to fine-grained coal gangue is 7:3.

[0074] The preparation method of the paste filling material includes the following steps: (1) The coal gangue is crushed into two particle sizes: coarse and fine. 5~20mm is the coarse particle size and <5mm is the fine particle size. The mass ratio of coarse coal gangue to fine coal gangue is 7:3. (2) Weigh 24.85 parts of cement, 53.85 parts of coarse and fine-grained compounded coal gangue and 21.30 parts of deionized water (the silicate content in the cement is 42.5%, and the total content of SiO2 and Al2O3 in the coal gangue is 86.9%). (3) Mix all components together and vibrate to obtain paste filling material.

[0075] The gradation results of coarse and fine coal gangue in this embodiment are shown in Table 13.

[0076] Table 13 Gradation results of coarse and fine coal gangue in Comparative Example 3

[0077] The paste filling material of this embodiment was placed in a standard constant temperature and humidity curing chamber for curing. The temperature of the curing chamber was set to 20°C and the humidity to 95%. The curing was carried out for 3 days, 7 days and 28 days respectively. The uniaxial compressive strength of the specimens cured for 3 days, 7 days and 28 days was tested using an electro-hydraulic pressure testing machine. The test results are shown in Table 14.

[0078] Table 14. Uniaxial compressive strength test results of the paste filling material in Comparative Example 3

[0079] The test results show that the coal gangue-mine water paste filling material in this comparative example has a dense skeleton structure formed by coarse-grained coal gangue particles and fine-grained coal gangue particles filling the gaps in the skeleton. However, without the addition of mine water, the uniaxial compressive strength of the paste filling material is improved to a certain extent, but the compressive strength at 28 days is 20.4% lower than that in Example 3.

[0080] This invention uses Talbol gradation theory to perform curve fitting on the particle size distribution of coal gangue aggregates in Examples 1-4, and compares it with the Fuller ideal gradation curve. The results are as follows: Figures 2-5 As shown, Figure 2 This is a comparison chart of the fitted curve (red curve) and the Fuller curve (blue curve) of the coal gangue aggregate gradation in Example 1. Figure 3 This is a comparison chart of the fitting curve (red curve) and the Fuller curve (blue curve) of the coal gangue aggregate gradation in Example 2. Figure 4 This is a comparison chart of the fitted curve (red curve) and the Fuller curve (blue curve) of the coal gangue aggregate gradation in Example 3. Figure 5 This is a comparison chart of the fitting curve (red curve) and Fuller curve (blue curve) of the coal gangue aggregate gradation in Example 4; from Figures 2-5 As can be seen, the gradation curve of Example 3 is closer to the Fuller ideal gradation curve, indicating that the coal gangue aggregate under the gradation of this example is more compactly packed, which corresponds to the 28-day compressive strength.

[0081] Furthermore, this invention utilizes Python scripts in Abaqus to programmatically generate aggregate models with specific particle size distributions conforming to the embodiments and comparative examples, such as... Figures 6-10 As shown: Figure 6 The random polygonal coal gangue aggregate model of Example 1 has a polygonal aggregate ratio of 58.1%. Figure 7 The random polygonal coal gangue aggregate model in Example 2 has a polygonal aggregate ratio of 62.6%. Figure 8 The random polygonal coal gangue aggregate model in Example 3 has a polygonal ratio of 63.5%. Figure 9The random polygonal coal gangue aggregate model in Example 4 has a polygonal ratio of 66.1%. Figure 10 The model for Comparative Example 1 shows a random polygonal coal gangue aggregate with a polygonal proportion of 61.6%. In the model diagram of Example 3, the larger proportion of random polygonal aggregate indicates that the coal gangue aggregate in this example has a more compact packing. Coal gangue particles of different sizes are combined to minimize porosity and form a stable spatial skeleton, which corresponds to the 28-day compressive strength test results and Fuller's theoretical analysis. Although Example 4 has the most compact packing, the reduced number of large particles weakens the skeleton effect, thus resulting in a lower 28-day compressive strength. Considering both economic benefits and compressive strength, the gradation design of Example 3 is the most reasonable, which also corresponds to its highest 28-day compressive strength.

[0082] As can be seen from the examples and comparative examples, the early and later compressive strengths of the paste filling material provided by this invention are significantly higher than those of the comparative examples. This demonstrates the superior performance of the paste filling material provided by this invention, which is inseparable from the optimized gradation of coal gangue and the activating effect of sulfate and chloride ions in mine water. This invention establishes a closed-loop analysis process of "theoretical guidance - model generation - visual evaluation": using Fuller theory as the theoretical basis for gradation design, a three-dimensional aggregate packing model conforming to a specific gradation is generated parametrically in the Abaqus environment using Python scripts. Through post-processing of finite element calculations, the internal structure of the packing (such as particle spatial arrangement and pore distribution) is visualized, reconstructed, and quantitatively analyzed. This method can directly and quantitatively output key indicators for evaluating packing quality (such as local porosity distribution), thereby achieving scientific diagnosis and optimization of the aggregate packing state and significantly improving the scientific rigor and foresight of the filling material mix design.

[0083] In summary, the paste-like filling material provided by this invention can achieve excellent solidification and mechanical properties, and does not require the addition of additives. Coal gangue and mine water can be directly utilized as resources. Therefore, it can be used as a new type of high-strength filling material and has great industrial applicability.

[0084] Furthermore, the paste-based filling material of this invention is not only suitable for filling goaf areas in conventional coal mines, but can also be flexibly adapted to various complex mining conditions and the needs of green mine construction, specifically in the following aspects: (1) Applicable to high-gas, deep and rockburst mines Traditional backfill materials require the addition of organic additives (such as polycarboxylate superplasticizers), which pose a risk of combustion and explosion in high-gas environments. This invention contains no additives or volatile components, is inherently safe, and is suitable for high-gas mines.

[0085] The paste exhibits stable early strength development, effectively controlling the deformation of surrounding rock caused by high ground stress in deep areas and mitigating the risk of rockburst.

[0086] (2) Compatible with existing filling systems, requiring no equipment modification This paste, when mixed with 15-25 parts mine water, exhibits excellent rheological properties (yield stress 50-50 Pa, plastic viscosity 20-60 Pa·s), and can be directly transported to the goaf via existing paste pumping systems (such as piston filling pumps and pipeline delivery systems) without the need for new or modified equipment. Its solids concentration is as high as 75%–80%, meeting the technical requirements for high-concentration paste filling (HCP).

[0087] (3) Supports continuous operation mode of "mining and charging simultaneously". The slurry preparation cycle is short (it can be pumped after 5-10 minutes of mixing), allowing it to be carried out simultaneously with the advance of the coal face, achieving coordinated mining and backfilling, and improving mining efficiency. The backfill material initially sets in 24 hours and reaches a strength of over 3MPa in 7 days, which can timely support the roof and ensure the safety of the next mining cycle.

[0088] (4) Achieve closed-loop utilization of water resources in mining areas Mine water is no longer discharged or subjected to further treatment; it is directly reused as mixing water, reducing wastewater discharge by tens of thousands of tons annually and lowering water treatment costs. After solidification, the backfill material physically encapsulates and chemically adsorbs heavy metals and other pollutants, achieving in-situ solidification of harmful substances in the mine water and preventing groundwater pollution.

[0089] The "mining-filling-drainage" integrated system refers to the organic integration of three major stages: coal mining, goaf filling, and mine water reuse, forming a resource-recycling and environmentally friendly green mining closed-loop system. This invention is particularly suitable for constructing an integrated "mining-filling-drainage" green mining system. A schematic diagram of the mining system flow is shown below. Figure 11 In practical applications, coal gangue from coal mining is simply crushed and screened, then mixed with untreated mine water and a small amount of cement in a specific ratio to prepare a high-concentration paste. This paste is then pumped to the mined-out area of ​​the same day or the previous day through existing filling pipelines. This method not only eliminates the two main types of waste from the mining area but also significantly reduces filling costs (saving approximately 80–120 yuan / ton in additive costs), while avoiding the environmental risks caused by the discharge of mine water, achieving a win-win situation for both economic and ecological benefits.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A paste-like filling material, characterized in that, By weight, it comprises the following components: 20-30 parts cement, 50-60 parts coal gangue, and 15-25 parts mine water; the coal gangue includes coarse-grained coal gangue and fine-grained coal gangue, the coarse-grained coal gangue has a particle size of 5mm-20mm, the fine-grained coal gangue has a particle size of <5mm, and the mass ratio of coarse-grained coal gangue to fine-grained coal gangue is 6:4 to 9:

1.

2. The paste-filling material according to claim 1, characterized in that, The mass ratio of coarse-grained coal gangue to fine-grained coal gangue is 6:4 to 8:

2.

3. The paste-filling material according to claim 1 or 2, characterized in that, The mass ratio of coarse-grained coal gangue to fine-grained coal gangue is 7:3 to 8:

2.

4. The paste-filling material according to claim 1, characterized in that, The total content of SiO2 and Al2O3 in the coal gangue is 80%-90%; and / or, the SO4 content in the mine water is... 2- and Cl - The total content is 1000 mg / L-1200 mg / L.

5. The paste-filling material according to claim 1, characterized in that, The gradation of the coal gangue is A:B:C:D:E:F:G:H:I = (0.6-3):(0.15-0.8):(0.5-2.5):(0.5-3.5):(1.5-7):(1-4.5):(5-25):(35-55):(20-40); A, B, C, D, E, F, G, H, and I are the particle size gradient of the coal gangue, satisfying: A < 0.074 mm, 0.074 ≤ B < 0.1 mm, 0.1 ≤ C < 0.2 mm, 0.2 ≤ D < 0.5 mm, 0.5 ≤ E < 1.25 mm, 1.25 ≤ F < 2 mm, 2 ≤ G < 5 mm, 5 ≤ H < 10 mm, and 10 ≤ I ≤ 20 mm.

6. The paste-filling material according to claim 5, characterized in that, The gradation of the coal gangue is A:B:C:D:E:F:G:H:I = (1-2):(0.3-0.6):(1-2):(1-3):(3-5):(2-4):(10-20):(40-50):(25-35); A, B, C, D, E, F, G, H, and I are the particle size gradient of the coal gangue, satisfying: A < 0.074 mm, 0.074 ≤ B < 0.1 mm, 0.1 ≤ C < 0.2 mm, 0.2 ≤ D < 0.5 mm, 0.5 ≤ E < 1.25 mm, 1.25 ≤ F < 2 mm, 2 ≤ G < 5 mm, 5 ≤ H < 10 mm, and 10 ≤ I ≤ 20 mm.

7. The paste-filling material according to claim 5 or 6, characterized in that, A three-dimensional aggregate packing model conforming to the particle size distribution of the coal gangue was generated using a Python script, and the coal gangue packing was visualized, reconstructed, and quantitatively analyzed using finite element method (FEM) calculations.

8. A method for preparing the paste-like filling material according to any one of claims 1-7, characterized in that, The process includes the following steps: mixing the components evenly according to the stated weight proportions to obtain the paste filling material.

9. The method for preparing the paste filling material according to claim 8, characterized in that, Specifically, the following steps are included: Coal gangue is crushed according to the stated weight proportions to obtain coarse-grained coal gangue and fine-grained coal gangue in the stated mass ratio. Cement and mine water are then added according to the stated weight proportions and mixed evenly to obtain the paste filling material.

10. The application of the paste filling material according to any one of claims 1-7 or the paste filling material prepared by the preparation method according to any one of claims 8-9 in mine filling.

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