Preparation method of full-tailing cemented filling body for mine filling

Abstract

The invention provides a preparation method of a full-tailing cemented filling body for mine filling. The preparation method comprises three steps. 1, setting an experimental scheme and preparing a filling sample; 2, carrying out a uniaxial compression test on the fiber-doped and fiber-undoped full-tailing cemented filling body, and analyzing a test result; and 3, carrying out a dynamic impact experiment on the fiber-doped full-tailing cemented filling body and the fiber-undoped full-tailing cemented filling body, and analyzing the test result. The invention relates to the related technical field of underground mine goaf filling and filling body mechanical property research. According to the method, the polypropylene fiber material which is low in price and wide in material source is selected and added into the filling slurry, so that the brittle failure characteristic of the filling body is improved, and meanwhile, the amplification effect of fiber doping on the dynamic and static mechanical strength of the filling body is calculated. The research result of the invention can provide a theoretical basis for popularizing a fiber reinforcement technology for similar mines.

Description

Technical Field

[0001] This invention relates to the technical field of underground mine goaf filling and mechanical property research, and particularly to a method for preparing whole tailings cemented filling for mine filling. Background Technology

[0002] As my country's shallow mineral resources reserves gradually deplete, the development of mining towards deeper deposits has become the mainstream trend; however, a series of problems inevitably arise during the process of deep mining.

[0003] For example, when mining reaches a certain depth, large-volume goaf areas underground may experience widespread surface subsidence due to disturbances such as blasting and ore falling, damaging surface buildings and transportation facilities and causing huge economic losses. Secondly, the large amounts of tailings solid waste generated during ore beneficiation accumulate on the surface for extended periods, increasing the risk of tailings dam failure and threatening the lives and property of people around the mining area, while also severely polluting the local ecosystem. Tailings cemented backfill technology is increasingly widely used in underground mines due to its advantages, including effectively mitigating stress concentration in the surrounding rock, reducing the risk of surface subsidence, and consuming large amounts of solid tailings. Based on the actual engineering background of underground mines, it is known that backfill bodies exist in a special geological environment, facing both quasi-static loads from overlying rock subsidence and minor deformation of the surrounding rock, and dynamic loads that will inevitably be encountered during underground excavation, blasting, and the second-stage recovery of the ore pillar. Therefore, comprehensively optimizing the mechanical properties of the backfill body under both static and dynamic loads is of great significance.

[0004] Currently, domestic and international scholars have conducted extensive research on improving the strength of backfill bodies. Patent publication number CN112284892A discloses a method for improving the compressive strength of cemented tailings backfill bodies by replacing part of the cement with straw ash. This method significantly improves the compressive strength of the backfill body, reduces backfill costs by replacing part of the cement, and has the advantage of simple process. Straw ash, as a renewable resource, has low utilization and is even subject to indiscriminate discharge, which not only wastes resources but also causes environmental pollution. Furthermore, straw ash is widely available and inexpensive compared to chemical reagents and synthetic fibers. Applying straw ash to mine backfill not only improves the compressive strength of the backfill body but also reduces backfill costs and is beneficial to environmental protection. The simple process flow is also more suitable for on-site application.

[0005] However, existing research mainly focuses on static loads, and primarily emphasizes the addition of chemical reagents and synthetic fibers to enhance the strength of the infill. Considering that the infill is subjected to complex underground disturbances over a long period, research on the dynamic load of the infill has practical guiding significance. Related studies have shown that incorporating flexible fibers into the infill slurry to prepare infill specimens significantly improves both compressive and tensile strength. However, there are few reports on the dynamic uniaxial compressive strength of fiber-reinforced infill, and flexible fibers come in various types and prices. Existing technologies lack relevant research on the selection of flexible fiber materials, especially research on the selection of flexible fiber materials to meet the dynamic compressive strength requirements of the infill. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing cemented tailings backfill for mine filling, which addresses the shortcomings of the prior art. By preparing backfill samples with and without added fibers with the same ash-sand ratio as the mine site, and conducting dynamic and static mechanical tests on them, the static uniaxial compressive strength and dynamic compressive strength of the backfill samples with and without added fibers are obtained. The strength increase rate of the backfill sample with added fibers is calculated to obtain the improvement effect of the fibers.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a cemented backfill body made entirely of tailings for mine filling, characterized in that the method includes the following steps:

[0008] S1: Selection of test materials and preparation and curing of filling specimens:

[0009] The test materials include polypropylene fiber, mine tailings and cementing materials; according to the experimental design, tailings, cementing materials, water and polypropylene fiber are mixed to prepare filling body samples, with at least three samples at each level, and cured for 7 days and 28 days.

[0010] S2: The uniaxial compressive strength of the filling specimen was tested using a universal testing machine.

[0011] Uniaxial compressive strength tests were conducted on the fill samples after 7 days of curing to obtain the uniaxial compressive strength values ​​of fill samples with and without fiber under different cement-sand ratios. The increase in uniaxial compressive strength of the fill samples due to fiber incorporation was then calculated using the following formula:

[0012]

[0013] In the formula: n is the increase in compressive strength of fiber-reinforced fillings compared to ordinary fillings.

[0014] The compressive strength of the fiber-reinforced filler is expressed in MPa.

[0015] This represents the compressive strength of a typical filling material, expressed in MPa.

[0016] The increase rate of compressive strength of fiber-infused fillers relative to that of ordinary fillers was calculated, thereby determining the effect of fiber incorporation on the increase of static compressive strength of fillers.

[0017] In this invention, the preparation and curing of the filling sample in S1 includes the following steps:

[0018] a1: First, according to the actual filling ratio of the mine, calculate and weigh the mass of tailings, cement, fiber and tap water (the fiber content is 0.6% of the dry mass of tailings and cement, and the length is 12mm). Mix the cement, tailings and fiber until uniform. Then, add tap water in small amounts and stir for 5 minutes. Pour the uniformly mixed slurry into cylindrical molds of 50×50 and 50×100.

[0019] a2: Scrape off the excess slurry from the surface of the filling sample, demold it and transfer it to a constant temperature and humidity curing chamber (temperature 22.0℃, humidity 96%) for curing until the designed age.

[0020] The method for adding polypropylene fibers and the stirring steps in this invention are as follows:

[0021] 1. Anti-static drying.

[0022] 12mm polypropylene fibers (thickness ≤ 2cm) are laid flat on a breathable tray using a controlled-humidity drying method and placed in a constant temperature and humidity drying chamber. The temperature is set at 50~55℃ and the relative humidity at 30~40%, and the drying time is 3~4 hours. Appropriate humidity inhibits frictional charging between fibers and avoids static electricity buildup caused by simple hot air drying.

[0023] Before drying, dilute a nonionic antistatic agent (such as polyethylene glycol ester) into a 5% aqueous solution at a ratio of 0.1-0.2% of the fiber weight. Spray the solution evenly onto the fiber surface using a sprayer, let it stand for 10 minutes, and then proceed with controlled-humidity drying. The antistatic agent can form a conductive film on the fiber surface, quickly dissipating the charge and reducing adhesion at the source.

[0024] After drying, the fibers are immediately passed through an 80-mesh vibrating screen to break up the slightly clumped fiber bundles and prevent them from re-adheding due to static electricity during the cooling process.

[0025] II. Optimization of anti-static measures in the mixing process.

[0026] Humidification adjustment is carried out during the dry mixing stage. After the cement and tailings are dry mixed for 2 minutes, a small amount of water mist is sprayed evenly into the dry material using a sprayer (the amount of water sprayed is ≤ 0.5% of the total mass of the dry material), and then the dry mixing continues for 1 minute to increase the humidity of the dry material and reduce the frictional static electricity between the fibers and particles.

[0027] The fiber is fed using a spiral feeder with a guide groove, and the feeding speed is controlled at 5~10g / s. This method can replace manual spreading, so that the fiber is evenly dispersed along the guide groove and falls into the mixer, avoiding local high fiber concentration that leads to electrostatic adsorption and agglomeration.

[0028] The aforementioned screw feeder has an open feed hopper at the top and an open discharge port on one side at the bottom. A screw conveyor blade is provided between the discharge port and the feed hopper. During the directional rotation of the screw conveyor blade, the directional and precise conveying of fiber materials can be achieved, ensuring the stability of the material conveying.

[0029] The mixing equipment and screw conveyor blades are made of metal and are grounded. The metal body is grounded (grounding resistance ≤10Ω) to conduct away static electricity generated during conveying and mixing in real time, preventing charge from accumulating on the fiber surface.

[0030] III. Key Verification Steps.

[0031] After mixing, take a small amount of slurry and filter it through a Φ5mm sieve. If the number of residual fiber clumps on the sieve is ≤3 / 100g of slurry and the mass of a single fiber clump is ≤0.1g, the dispersion effect is satisfactory. If it is not satisfactory, add 0.05% antistatic agent or extend the dry mixing time by 2 minutes until the requirements are met.

[0032] In this invention, the uniaxial compressive strength test of the filling sample in S2 includes the following steps:

[0033] b1: Preparation before uniaxial compressive strength test of filling body: Grind the filling body sample that has reached the 7-day curing age to make it smooth; preheat the universal testing machine and perform the pressure test.

[0034] b2: Uniaxial compressive strength test process of filling body: The test was conducted using a WDW-20 microcomputer-controlled electronic universal testing machine manufactured by Jinan Huaxing Testing Equipment Co., Ltd. The maximum load of the testing machine is 20KN. Displacement loading was used with a loading rate of 0.5mm / min. Displacement and load data were recorded every 0.3s. Finally, the stress-strain curves of the filling body specimens at each level were obtained. The strength corresponding to the highest point of the curve is the uniaxial compressive strength of the filling body specimen.

[0035] b3: Calculation of strength increase rate: The uniaxial compressive strengths of fiber-filled and fiber-free samples under different cement-sand ratios are summarized, and the strength increase rate is calculated according to the following formula:

[0036]

[0037] In the formula: n is the increase in compressive strength of fiber-reinforced fillings compared to ordinary fillings.

[0038] The compressive strength of the fiber-reinforced filler is expressed in MPa.

[0039] This represents the compressive strength of a typical filling material, expressed in MPa.

[0040] The increase rate of compressive strength of fiber-infused fillers relative to that of ordinary fillers was calculated, thereby determining the effect of fiber incorporation on the increase of static compressive strength of fillers.

[0041] S3: Testing the dynamic uniaxial compressive strength of the filling specimen using the Hopkinson bar:

[0042] Dynamic uniaxial impact tests were conducted on infill specimens that had reached a curing age of 28 days to obtain the dynamic compressive strength values ​​of infill specimens with and without fiber under different cement-sand ratios. The strength increase rate was calculated using the following formula:

[0043]

[0044] In the formula: m is the increase rate of dynamic compressive strength of fiber-reinforced filling compared to ordinary filling.

[0045] The dynamic compressive strength of the fiber-reinforced filler is expressed in MPa.

[0046] This represents the dynamic compressive strength of a typical filling material, expressed in MPa.

[0047] The increase rate of dynamic compressive strength of fiber-infused fillers relative to that of ordinary fillers was calculated, thereby determining the effect of fiber incorporation on the increase of dynamic compressive strength of fillers.

[0048] The beneficial effects of this invention are as follows:

[0049] Compared with existing technologies, this method has the following advantages: by adding polypropylene fibers to the filling slurry to form a fiber-reinforced tailings backfill, its mechanical properties are significantly improved compared to ordinary backfill. Furthermore, compared to adding chemical reagents, plant fibers, and other additives, polypropylene fibers are simple to process, sourced from minerals, inexpensive, and cause minimal environmental pollution. The research findings can promote the application of fiber-reinforced technology in practical mining operations. Attached Figure Description

[0050] Figure 1 This is a flowchart of the method of the present invention.

[0051] Figure 2 This is a particle size distribution diagram of the tailings used in the experiment of this invention.

[0052] Figure 3This is a static compressive strength diagram of the cemented tailings backfill with and without fiber in this invention.

[0053] Figure 4 The diagram shows the dynamic compressive strength of the fiber-coated and fiber-free tailings cemented backfill bodies of this invention. Detailed Implementation

[0054] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0055] This invention proposes a method for improving the dynamic and static mechanical properties of cemented tailings backfill using flexible fiber materials, comprising three steps: 1. Setting up an experimental scheme and preparing backfill samples; 2. Conducting uniaxial compressive strength tests on cemented tailings backfill with and without fiber, and analyzing the test results; 3. Conducting dynamic impact tests on cemented tailings backfill with and without fiber, and analyzing the test results. This invention improves the brittle fracture characteristics of the backfill by adding inexpensive and widely available polypropylene fiber materials to the backfill slurry, and simultaneously calculates the effect of fiber incorporation on the increase in the dynamic and static mechanical strength of the backfill. The research results of this invention can provide a theoretical basis for promoting fiber reinforcement technology in similar mines.

[0056] Please refer to the appendix for details. Figure 1 -Appendix Figure 4 A method for preparing cemented tailings backfill for mine filling includes the following steps:

[0057] S1: Select test materials, set up test plans, and prepare filling body samples.

[0058] Polypropylene fibers were selected and processed to a length of 12mm. Three ash-sand ratios of 1:4, 1:6, and 1:8 were designed in the experiment, with curing ages of 7 days and 28 days, and a slurry concentration of 75%.

[0059] (1) Through experiments, it was found that the strength of the filling sample was the greatest when 12mm fiber was used.

[0060] (2) The three ash-sand ratios of 1:4, 1:6, and 1:8 and the slurry concentration of 75% are commonly used parameters for underground filling in mines.

[0061] (3) The curing period is set at 7 days to test the early strength of the filling body. After 28 days of curing, the hydration reaction in the filling body has basically ended, and the strength of the filling body is basically stable at this time.

[0062] S2: Conduct uniaxial compressive strength testing of the filling material.

[0063] The compressive strength of fiber-added and non-fiber-added infill materials that have reached the curing age was tested to obtain the peak uniaxial compressive strength of infill materials at each level, and the increase rate of compressive strength was calculated using the following formula:

[0064]

[0065] In the formula: n is the increase in compressive strength of fiber-reinforced fillings compared to ordinary fillings.

[0066] The compressive strength of the fiber-reinforced filler is expressed in MPa.

[0067] This represents the compressive strength of a typical filling material, expressed in MPa.

[0068] The increase rate of compressive strength of fiber-infused fillers relative to that of ordinary fillers was calculated, thereby determining the effect of fiber incorporation on the increase of static compressive strength of fillers.

[0069] S3: Conduct dynamic compressive strength testing of the filling material.

[0070] Dynamic compressive strength tests were conducted on fiber-added and non-fiber-added infill materials that had reached the curing age. The peak dynamic compressive strength of each infill material was obtained, and the increase rate of dynamic compressive strength was calculated using the following formula:

[0071]

[0072] In the formula: m is the increase rate of dynamic compressive strength of fiber-reinforced filling compared to ordinary filling.

[0073] The dynamic compressive strength of the fiber-reinforced filler is expressed in MPa.

[0074] This represents the dynamic compressive strength of a typical filling material, expressed in MPa.

[0075] The increase rate of dynamic compressive strength of fiber-infused fillers relative to that of ordinary fillers was calculated, thereby determining the effect of fiber incorporation on the increase of dynamic compressive strength of fillers.

[0076] The preparation and curing of the filling sample in S1 includes the following steps:

[0077] a1: Preparation of backfill samples: Considering the actual backfill ratio in the mine, according to the experimental design, the weighed cement tailings were first mixed dry, and then the fiber was added in small amounts several times and mixed thoroughly (the fiber content was 0.6% of the dry mass of the cement tailings, and the fiber content in the control group was 0%). Then, water was added to the bucket in small amounts several times and stirred with a mixer until uniform. Then, it was poured into 50×50mm and 50×100mm circular molds. The above dimensions are the standard sample dimensions.

[0078] a2: Curing of filling samples: After demolding, the samples are transferred to a constant temperature and humidity curing chamber for curing. The temperature is set at (20±2)℃ and the humidity is (95%±1%). Curing is carried out for 7 days and 28 days. In order to ensure that the filling is fully hydrated and avoid early cracking, the temperature should be set at 20±2℃ and the humidity at 95%±1%.

[0079] The compressive strength test of the filling material in S2 includes the following steps:

[0080] b1: Preparation for uniaxial compressive strength test of filling specimens: Grind the upper and lower end faces of the filling specimens that have reached the curing age of 7 days and 28 days to make them smooth.

[0081] b2: Compressive strength test process of filling body specimens: The uniaxial compressive strength test of filling bodies was conducted using a WDW-20 microcomputer-controlled electronic universal testing machine. Displacement loading was used during the test. Because the prepared filling body specimens are brittle-ductile materials, in order to avoid incomplete data acquisition due to instantaneous specimen fracture, the loading rate was set to 0.01 mm / s. The loading rate range of this equipment is 0.01 mm / s to 500 mm / s. Therefore, in order to obtain complete experimental data and in combination with the properties of the filling body material, the loading rate in this test was set to the minimum value of 0.01 mm / s. When the peak compressive strength of the filling body was reached, the test system automatically ended the work. Three groups of specimens were tested at each level, and the average value was calculated.

[0082] The dynamic compressive strength test of the filling material in S3 includes the following steps:

[0083] c1: Preparation for dynamic compressive strength test of filling specimen: Grind the end face of the 50×50mm filling specimen flat and apply Vaseline coupling agent, and adjust the instrument level.

[0084] c2: Dynamic compression test process of filling body: The dynamic impact test adopts the Hopkinson bar test system.

[0085] Lubricating oil is applied to both ends of the filled specimen that has reached the curing age. It is placed between the incident rod and the transmission rod, and the rods are kept aligned. The air pressure is fixed, and the position of the punch in the chamber is controlled each time to achieve a single impact test at different impact velocities. After the test, the waveform and time acquired by the data acquisition system are saved.

[0086] The universal electronic press has a maximum load of 20KN, a pressure sensor accuracy of 0.001N, and a displacement sensor accuracy of 0.001mm.

[0087] The Hopkinson pressure bar main body includes an incident rod, a transmission rod, an absorption rod, and a punch, wherein the lengths of the three rods are 2.0m, 1.5m, and 0.5m, respectively; the density of this type of steel is... 7810kg / elastic modulus The pressure is 240 GPa, the elastic wave velocity is 5400 m / s, and the wave impedance of the rod is 42 TPa / s.

[0088] The present invention will be further described below with reference to specific embodiments.

[0089] The technical problem to be solved by this invention is to comprehensively improve the dynamic and static compressive strength of the cemented tailings backfill using inexpensive and widely available polypropylene fibers. The specific method is described in detail in conjunction with the following embodiments:

[0090] Example 1

[0091] A method for preparing cemented tailings backfill for mine filling includes the following steps:

[0092] Raw material preparation: The tailings used in the experiment were obtained from the whole tailings slurry generated by the ore dressing plant. After natural settling, it was spread out and dried before being transported to the laboratory. The particle size distribution of the whole tailings was then measured using a laser particle size analyzer after agate grinding. (See figure). Figure 2 .from Figure 2 It can be seen that the cumulative particle size distribution of the tailings in this mine is D. 10 =3.14μm, D 30 =7.6μm, D 50 =14.9μm, D 60 =19.8μm, D 90 =50.3μm, the total tailings particle size is calculated to be of medium to fine grade. The uniformity coefficient C of the tailings is also calculated. u (D) 60 / D 10 Curvature coefficient C c (D) 30 2 / D 60 ×D 10 The values ​​were 6.3 and 0.93 respectively, indicating poor gradation of the tailings in the mine. P.O42.5 ordinary Portland cement was used as the cementitious agent.

[0093] Table 1. Main chemical composition of tailings and cement (%)

[0094] Table 1

[0095]

[0096] Preparation and curing of filling samples: Based on the actual cement-sand ratio of the filling at the mine site, three cement-sand ratios of 1:4 to 1:8 were designed, with a slurry concentration of 75%. Specific parameters are shown in Table 2. All raw materials were weighed. First, the tailings and cement were dry-mixed for 5 minutes. Then, water was added in small amounts several times, mixing until uniform. The mixture was poured into cylindrical molds of 50mm×50mm and 50mm×100mm. After 24 hours, the samples were demolded and transferred to a constant temperature and humidity curing chamber for curing until the designed age.

[0097] Table 2

[0098]

[0099] Testing the uniaxial compressive strength of fiber-free fillings

[0100] Preparation before the test: First, grind the top and bottom of the filling sample that has reached the 7-day curing age to make it smooth, and apply a small amount of petroleum jelly coupling agent evenly to reduce end friction.

[0101] Testing process: Before the formal test, the universal testing machine was pre-loaded to ensure the stability of the subsequent testing process. The universal testing machine adopted displacement loading at a loading rate of 0.5 mm / min, and the data was recorded every 0.3 s to obtain the stress-strain curve of the filling body throughout the process. The ordinate corresponding to the highest point of the curve is the uniaxial compressive strength of the filling body. Three sets of samples were set for each level, and the average value was taken as the uniaxial compressive strength value of the filling body at that level.

[0102] According to the test results, the uniaxial compressive strength of the fiberless tailings cemented backfill body after 7 days of curing is 2.39MPa, 1.20MPa and 0.78MPa.

[0103] Testing the dynamic uniaxial compressive strength of fiber-free fillings

[0104] Test Procedure: Align the incident rod, transmission rod, and absorption rod; check the stability of the nitrogen cylinder pressure; install the launching punch in a suitable position in the chamber and conduct a trial impact test; check if the waveform displayed on the oscilloscope is normal; after everything is normal, grind the cross-section of the filling sample that has reached the 28-day curing age, apply a small amount of petroleum jelly coupling agent, align it with the pressure rod, and conduct an impact test at a suitable speed. After the test is completed, read the speed and filter the waveform to finally plot the dynamic uniaxial compressive strength curve.

[0105] Tests showed that the uniaxial compressive strength of the fiberless tailings cemented backfill was 4.80 MPa, 3.90 MPa, and 2.59 MPa after 28 days of curing.

[0106] Example 2

[0107] Fiber selection: Based on the unit price of the fiber and physical and mechanical parameters, polypropylene fiber is selected as the additive in this invention, processed into 12mm, with a content of 0.6% (0.6% of the dry mass of tailings and cement).

[0108] Preparation of filling body samples: Three cement-sand ratios of 1:4 to 1:8 were designed, and the slurry concentration was 75%. Specific parameters are shown in Table 3. Weigh each raw material. First, mix the tailings, cement and polypropylene fiber dry for 5 minutes. Then, add water in small amounts several times and mix until uniform. Pour the mixture into cylindrical molds of 50mm×50mm and 50mm×100mm. After 24 hours, demold the samples and transfer them to a constant temperature and humidity curing chamber for curing until the designed age.

[0109] Table 3

[0110]

[0111] Testing the uniaxial compressive strength of fiber-reinforced filling specimens

[0112] Preparation before the test: First, grind the top and bottom of the filling sample that has reached the 7-day curing age to make it smooth, and apply a small amount of petroleum jelly coupling agent evenly to reduce end friction.

[0113] Testing Procedure: Before the formal test, the universal testing machine was pre-loaded to ensure stability during the subsequent testing process. The universal testing machine used displacement loading at a loading rate of 0.5 mm / min, recording data every 0.3 seconds to obtain the stress-strain curve of the filling material throughout the entire process. The ordinate corresponding to the highest point of the curve represents the uniaxial compressive strength of the filling material. Three sets of samples were used at each level, and the average value was taken as the uniaxial compressive strength value of the filling material at that level.

[0114] According to the test results, the uniaxial compressive strength of the fiber-reinforced tailings cemented backfill body after 7 days of curing is 2.55MPa, 1.33MPa and 0.87MPa.

[0115] Calculation of the increase rate of uniaxial compressive strength:

[0116] The uniaxial compressive strengths of fiber-filled and fiber-free samples at different cement-sand ratios were summarized, and the strength increase rate was calculated using the following formula:

[0117]

[0118] In the formula: n is the increase in compressive strength of fiber-reinforced fillings compared to ordinary fillings.

[0119] The compressive strength of the fiber-reinforced filler is expressed in MPa.

[0120] This represents the compressive strength of a typical filling material, expressed in MPa.

[0121] See Table 4 for specific increases.

[0122] Table 4

[0123]

[0124] Testing the dynamic uniaxial compressive strength of fiber-reinforced filling specimens

[0125] Test Procedure: Align the incident rod, transmission rod, and absorption rod; check the stability of the nitrogen cylinder pressure; install the launching punch in a suitable position within the chamber and conduct a trial impact test; check if the waveform displayed on the oscilloscope is normal. After everything is normal, grind the cross-section of the filling sample that has reached 28 days of curing age, apply a small amount of petroleum jelly coupling agent, align it with the pressure rod, and conduct an impact test at an appropriate speed. After the test is completed, read the speed, filter the waveform, and finally plot the dynamic uniaxial compressive strength curve.

[0126] Tests showed that the uniaxial compressive strength of the fiberless tailings cemented backfill was 7.26 MPa, 4.79 MPa, and 3.37 MPa after 28 days of curing.

[0127] Calculation of dynamic uniaxial compressive strength increase rate: The dynamic uniaxial compressive strengths of fiber-filled and fiber-free filling samples under different cement-sand ratios are summarized, and the strength increase rate is calculated according to the following formula:

[0128]

[0129] Where: m is the increase rate of dynamic compressive strength of fiber-reinforced filling compared to ordinary filling;

[0130] The dynamic compressive strength of the fiber-reinforced filler is expressed in MPa.

[0131] This represents the dynamic compressive strength of a typical filling material, expressed in MPa.

[0132] See Table 5 for specific increases.

[0133] Table 5

[0134]

[0135] In summary, based on the experimental data in the table, it can be seen that when the fiber length is processed to 12mm and the fiber content is 0.6%, the static compressive strength of the fiber-filled material can be increased by up to 11.54%, and the dynamic compressive strength increase is even more significant, reaching up to 51.25%. Therefore, it is clear that optimizing fiber length and fiber content can significantly enhance the mechanical properties of the filling material. This technological breakthrough not only effectively improves the quality of mine filling but also provides a reliable technical guarantee for the safe and efficient recovery of underground pillar resources.

[0136] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing cemented tailings backfill for mine filling, characterized in that, Includes the following steps: S1. Determine the uniaxial compressive strength of the filling material. Compressive strength tests were conducted on fiber-added and non-fiber-added infill bodies that had reached a curing age of 7 days. The peak uniaxial compressive strength of each infill body was obtained, and the increase rate of compressive strength was calculated using the following formula: ； In the formula: n is the increase rate of compressive strength of fiber-reinforced filling compared to ordinary filling; The compressive strength of the fiber-reinforced filler is expressed in MPa. This represents the compressive strength of a typical filling material, expressed in MPa. The increase rate of compressive strength of fiber-infused fillers relative to that of ordinary fillers was calculated, and the effect of fiber incorporation on the increase of static compressive strength of fillers was determined. S2. Determine the dynamic compressive strength of the filling material. Dynamic compressive strength tests were conducted on fiber-added and non-fiber-added infill bodies that had reached a curing age of 28 days. The peak dynamic compressive strength of each infill body level was obtained, and the increase rate of dynamic compressive strength was calculated using the following formula: ； Where: m is the increase rate of dynamic compressive strength of fiber-reinforced filling compared to ordinary filling; The dynamic compressive strength of the fiber-reinforced filler is expressed in MPa. This represents the dynamic compressive strength of a typical filling material, expressed in MPa. The increase rate of dynamic compressive strength of fiber-infused fillers relative to that of ordinary fillers was calculated, thereby determining the effect of fiber incorporation on the increase of dynamic compressive strength of fillers. S3. Determination and preparation of filler materials Based on the uniaxial compressive strength and dynamic compressive strength of the filling material, polypropylene fiber was selected, with a processing length of 12 mm and a slurry concentration of 75%.

2. The method for preparing a cemented tailings backfill for mine filling according to claim 1, characterized in that, In S3, the filling sample preparation and curing are carried out first. The filling sample preparation and curing includes the following steps: a1: Preparation of filling body samples: Considering the actual filling ratio of the mine, according to the experimental design, the weighed cement tailings were first mixed dry, then the fiber was added in small amounts and mixed thoroughly, then water was added in small amounts to the bucket and stirred with a mixer until uniform, and then poured into 50×50mm and 50×100mm circular molds. a2: Curing of filling samples: After demolding, the samples are transferred to a constant temperature and humidity curing chamber and cured for 7 days and 28 days.

3. The method for preparing a cemented tailings backfill for mine filling according to claim 2, characterized in that, In step a2, the temperature in the constant temperature and humidity curing chamber is (20±2)℃ and the humidity is (95%±1%).

4. The method for preparing a cemented tailings backfill for mine filling according to claim 2, characterized in that, In step a1, the fiber content is 0.6% of the dry mass of cement tailings.

5. The method for preparing a cemented tailings backfill for mine filling according to claim 1, characterized in that, The compressive strength test of the filling material in S1 includes the following steps: b1: Preparation for uniaxial compressive strength test of filling specimens: Grind the upper and lower end faces of the filling specimens that have reached the curing age of 7 days and 28 days to make them smooth. b2: Compressive strength test process of filling body specimens: The uniaxial compressive strength test of filling body adopts a microcomputer-controlled electronic universal testing machine. Displacement loading is used during the test. When the peak compressive strength of the filling body is reached, the test system automatically stops working. Three sets of specimens are tested at each level, and the average value is calculated.

6. The method for preparing a cemented tailings backfill for mine filling according to claim 5, characterized in that, Step b2 sets the loading rate to 0.01 mm / s.

7. The method for preparing a cemented tailings backfill for mine filling according to claim 1, characterized in that, The dynamic compressive strength test of the filling material in S2 includes the following steps: c1: Preparation for dynamic compressive strength test of filling specimen: Grind the end face of the 50×50mm filling specimen flat and apply Vaseline coupling agent, and adjust the instrument level. c2: Dynamic compressive strength test process of filling body: The dynamic impact test adopts the Hopkinson bar test system; Lubricating oil is applied to both ends of the filled specimen that has reached the curing age. It is placed between the incident rod and the transmission rod, and the rods are kept aligned. The air pressure is fixed, and the position of the punch in the chamber is controlled each time to achieve a single impact test at different impact velocities. After the test, the waveform and time acquired by the data acquisition system are saved.

8. The method for preparing a cemented tailings backfill for mine filling according to claim 7, characterized in that, The universal electronic press has a maximum load of 20KN, a pressure sensor accuracy of 0.001N, and a displacement sensor accuracy of 0.001mm.

9. The method for preparing a cemented tailings backfill for mine filling according to claim 7, characterized in that, The Hopkinson pressure bar main body includes an incident rod, a transmission rod, an absorption rod, and a punch, wherein the lengths of the three rods are 2.0m, 1.5m, and 0.5m, respectively; the density of this type of steel is... 7810kg / elastic modulus The pressure is 240 GPa, the elastic wave velocity is 5400 m / s, and the wave impedance of the rod is 42 TPa / s.

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