Graphite tailing-based coal mine underground energy-absorbing support material and preparation method thereof

Abstract

The invention relates to a method for preparing an underground coal mine energy-absorbing support material from graphite tailings, and belongs to the technical field of underground energy-absorbing support materials. In order to solve the problem that an existing underground coal mine energy-absorbing supporting material is insufficient in supporting strength and deformation resistance, the invention provides a method for preparing an underground coal mine energy-absorbing supporting material from graphite tailings, and the method comprises the following steps: pretreating raw materials, mixing dry materials, adding rubber particles, mixing, adding water, stirring, forming and curing. Compared with a traditional gravel-cement support material, the coal mine underground energy-absorbing support material prepared by taking the graphite tailings as the main aggregate and compounding the industrial rubber particles and the steel fibers has the advantages that the compressive strength is improved by 30-40%, the limit deformation quantity is improved by 50% or above, and the coal mine underground energy-absorbing support material has the double advantages of high strength and large deformation. When bearing mine ground pressure, the material can realize energy absorption through elastic deformation and fiber bridging effect, the energy absorption efficiency can reach 65-70%, and surrounding rock stress impact can be effectively buffered.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of underground energy-absorbing supporting materials, and particularly relates to a graphite tailings-based underground coal mine energy-absorbing supporting material and a preparation method thereof. BACKGROUND

[0002] In the current underground supporting engineering of coal mines, the supporting system made of natural sand such as river sand and mountain sand as the main aggregate, mixed with cement and other cementitious materials still occupies a dominant position. Such materials have been used in the field of coal mining for a long time due to the characteristics of easy availability of raw materials and simple construction technology. However, with the increasing depth of underground mining and the increasingly complex geological conditions, the inherent defects of traditional supporting materials gradually become prominent, becoming a key factor restricting construction efficiency and safety.

[0003] Firstly, natural sand aggregate needs to go through multiple grading and screening processes to meet the construction particle size requirements, which not only increases equipment investment, labor costs and material losses, but also prolongs the construction period and significantly increases the production cost of enterprises. Secondly, the mechanical properties of traditional supporting materials have inherent defects, with weak supporting strength and deformation resistance, and no energy-absorbing and pressure-reducing function. Under the action of surrounding rock stress, it is in a "rigid bearing" state. Once the surrounding rock stress exceeds the deformation critical range of the supporting structure, it will suddenly fail without warning, which not only fails to provide effective warning time for workers, but also is difficult to buffer stress impact, and is prone to cause roof collapse, surrounding rock collapse and other safety accidents. Therefore, it is urgent to develop new supporting materials to solve this problem. SUMMARY

[0004] To solve the problem of insufficient supporting strength and deformation resistance of existing underground energy-absorbing supporting materials in coal mines, the application provides a graphite tailings-based underground energy-absorbing supporting material for coal mines and a preparation method thereof.

[0005] The technical scheme of the application is as follows:

[0006] A method for preparing an underground energy-absorbing supporting material for coal mines from graphite tailings, comprising the following steps:

[0007] Step 1: Pretreatment of raw materials

[0008] The graphite tailings are dried for standby, and the rubber particles are surface modified with a silane coupling agent and then dried for standby;

[0009] Step 2: Dry material mixing

[0010] The pretreated graphite tailings, cement and steel fibers are weighed according to the proportion and mixed uniformly under a certain stirring speed;

[0011] Step 3: Adding rubber particles and mixing

[0012] The pretreated rubber particles are added into the stirrer, and dry mixing is continued to uniformly disperse the rubber particles in the dry material system;

[0013] Step four, stirring with water:

[0014] The amount of water is taken according to the proportioning quantity, and is added into the dry material system obtained in step three in batches, and stirring is carried out while adding water, until a uniform, viscous and non-bleeding slurry mixture is formed;

[0015] Step five, molding and curing:

[0016] It includes molding for pre-supporting components and molding for on-site casting underground, the molding for pre-supporting components is pouring the mixture obtained in step four into a mold, vibrating to remove internal bubbles, scraping the surface and covering a moisture-proof film for curing, to ensure that the cement is fully hydrated and reaches the design strength;

[0017] The molding for on-site casting underground is specifically direct construction by a delivery pump or a jet machine, and natural curing in a humid underground environment to ensure that the cement is fully hydrated and reaches the design strength.

[0018] Further, the drying temperature of the graphite tailings in step one is 105±5℃, and the drying time is 4-6h; the silane coupling agent is KH-550, and the modification method is to soak the rubber particles in a 5% silane coupling agent ethanol solution for 30min, the drying temperature of the modified rubber particles is 80±5℃, and the drying time is 2h.

[0019] Further, the graphite tailings are continuously graded, the particle size range is 0.15-10mm, the coarse particle size of 5-10mm accounts for 25-30%, the medium particle size of 1-5mm accounts for 40-45%, and the fine particle size of 0.15-1mm accounts for 25-30%.

[0020] Further, the proportioning in step two is that, based on the mass of cement, the mass ratio of water, cement, graphite tailings, rubber particles and steel fibers is 1:(0.72-0.8):(4.67-5):(0.01-0.02):(0.03-0.05).

[0021] Further, the type of the cement in step two is PO42.5, PO42.5R, PⅠ42.5, PⅡ42.5, PC42.5 or PSA42.5; the steel fiber is a steel or iron fiber with a length of 1-1.2cm and a diameter of 0.05-0.15cm.

[0022] Further, the stirring speed in step two is 200-300r / min, and the dry mixing time is 3-5min.

[0023] Further, the rubber particles in step three are uniform particles with a length of 0.2-0.4 cm.

[0024] Further, the stirring speed in step four is 350-400 r / min, and the total stirring time is 5-8 min; the slump of the obtained slurry mixture is controlled to be 120-150 mm.

[0025] Further, the curing temperature of the prefabricated support member in step five is not lower than 5 DEG C, and the curing time is not less than 7 days.

[0026] The beneficial effects of the present application are as follows:

[0027] The coal mine underground energy absorption support material prepared by the present application with graphite tailings as the main aggregate, compounded with industrial rubber particles and steel fibers has a 30-40% increase in compressive strength and an increase of more than 50% in ultimate deformation, and has the dual advantages of high strength and large deformation. When subjected to the action of mine pressure, the material can realize energy absorption through elastic deformation and fiber bridging effect, and the energy absorption efficiency can reach 65-70%, which can effectively buffer the stress impact of surrounding rock and avoid the disadvantages of sudden brittle failure of traditional support structure, thereby reserving sufficient emergency warning time for underground workers, and improving the stability of support space surrounding rock by 45%, thereby significantly reducing the incidence of safety accidents such as roof collapse and surrounding rock collapse.

[0028] The natural particle size of the graphite tailings completely meets the technical requirements of underground support construction, and no grading and screening pretreatment is required, thereby directly saving the investment cost of screening equipment and reducing the consumption of labor and working hours by more than 30%. At the same time, the graphite tailings are used to replace natural aggregates such as river sand and mountain sand, thereby reducing the raw material procurement cost by 15-20%; and large-scale absorption of tailings can reduce the management cost of land leasing, environmental protection treatment and other aspects of solid waste storage of graphite production enterprises. The comprehensive production cost of the support member prepared by the present application is reduced by 25-30% compared with the traditional process, the economic effect is very significant, and the present application is consistent with the concept of green mine construction and ecological and environmental protection development, and has outstanding ecological and social benefits. DETAILED DESCRIPTION

[0029] The technical solutions of the present application are further described below in conjunction with the examples, but are not limited thereto, and any modification or equivalent replacement to the technical solutions of the present application without departing from the spirit and scope of the present application shall be covered in the protection scope of the present application. The process equipment or device not specifically mentioned in the following examples is the conventional equipment or device in the art, and the raw materials used in the examples of the present application are commercially available if not specifically mentioned; and the technical means used in the examples of the present application is the conventional means well known to those skilled in the art if not specifically mentioned.

[0030] Example 1

[0031] The embodiment provides a preparation method of a graphite tailing-based energy-absorbing supporting material for underground coal mines.

[0032] The graphite tailing in the embodiment is a continuous grading with a particle size of 0.15-10 mm, wherein the coarse particle size of 5-10 mm accounts for 30%, the compressive strength and structural stability of the supporting material are provided; the medium particle size of 1-5 mm accounts for 40%, the coarse particle gap is filled, and the aggregate compactness is improved; the fine particle size of 0.15-1 mm accounts for 30%, the adhesion with the cement paste is enhanced; and the clay content is less than or equal to 1%.

[0033] The preparation method of the graphite tailing-based energy-absorbing supporting material for underground coal mines in the embodiment comprises the following steps:

[0034] Step one, raw material pretreatment:

[0035] The graphite tailing is placed in a drying device, dried at 105 DEG C for 5 h, and cooled to room temperature for standby after removing the surface free water;

[0036] The rubber particles are washed with clean water to remove the surface dust, then soaked in a 5% silane coupling agent KH-550 ethanol solution for 30 min, and taken out and dried at 80 DEG C for 2 h, so that the interfacial adhesion between the rubber particles and the cement paste is improved, and the debonding in the later stage is avoided;

[0037] Step two, dry material mixing:

[0038] The pretreated graphite tailing, cement, steel fiber and rubber particles are weighed according to the mass ratio of water, cement, graphite tailing, rubber particles and steel fiber, that is, 1:0.8:5:0.01:0.03, and put into a concrete mixer, dry mixing at a speed of 200 r / min for 5 min, to ensure that the cement uniformly wraps the surface of the aggregate;

[0039] Step three, adding rubber particles and mixing:

[0040] The pretreated rubber particles are added to the mixer, and dry mixing is continued for 2 min, so that the rubber particles are uniformly dispersed in the dry material system;

[0041] Step four, water mixing:

[0042] The quantitative water is taken according to the proportioning amount, added into the mixer in three times, and stirred while adding water, the speed is improved to 350 r / min, the total stirring time is 8 min, until a uniform, viscous and non-bleeding paste mixture is formed, and the slump is controlled at 120-150 mm;

[0043] Step five, molding and curing:

[0044] For prefabricated support components: pour the mixture obtained in step four into the mold, vibrate for 3 min with a vibrating table to remove internal bubbles, scrape the surface and cover it with a moisture-retaining film for curing. The test piece used in this example has a length of 100 mm and a diameter of 50 mm. After the test piece is made, it is placed in a curing box with a temperature of 25°C, a humidity of 95%, and a curing time of 28 days.

[0045] Example 2

[0046] The present example provides a preparation method of a graphite tailings-based energy-absorbing support material for underground coal mines.

[0047] The graphite tailings of the present example have a continuous gradation of particle sizes of 0.15-10 mm, wherein the particle size range is 0.15-10 mm, the coarse particle size of 5-10 mm accounts for 30%, the medium particle size of 1-5 mm accounts for 40%, and the fine particle size of 0.15-1 mm accounts for 30%, and the clay content is ≤1%.

[0048] The preparation method of the graphite tailings-based energy-absorbing support material for underground coal mines of the present example includes the following steps:

[0049] Step one, raw material pretreatment:

[0050] The graphite tailings are placed in a drying device and dried at 105°C for 5h to remove surface free water, and then cooled to room temperature for standby;

[0051] The rubber particles are rinsed with clean water to remove surface dust, then soaked in a 5% silane coupling agent KH-550 ethanol solution for 30 min, and then dried at 80°C for 2h after taking out, to improve the interfacial adhesion between the rubber particles and the cement paste, and to avoid debonding in the later stage;

[0052] Step two, dry material mixing:

[0053] Based on the mass of cement, the pretreated graphite tailings, cement, steel fiber, and rubber particles are weighed according to the mass ratio of water, cement, graphite tailings, rubber particles, and steel fiber of 1:0.72:4.67:0.02:0.05, and then put into a concrete mixer for dry mixing at a speed of 200r / min for 5min to ensure that the cement uniformly wraps the surface of the aggregate;

[0054] Step three, rubber particle mixing:

[0055] The pretreated rubber particles are added to the mixer and continue to dry mix for 2min to evenly disperse the rubber particles in the dry material system;

[0056] Step four, water mixing:

[0057] Take the quantitative water according to the proportioning amount, add it into the stirring machine in 3 times, stir while adding water, the rotating speed is raised to 350 r / min, the total stirring time is 8 min, until a uniform, viscous and no bleeding slurry mixture is formed, the slump is controlled at 120~150 mm;

[0058] Step five, forming and curing:

[0059] For prefabricated support members: pour the mixture obtained in step four into the mold, vibrate for 3 min with a vibrating table, remove internal bubbles, scrape the surface and cover with a moisture retention film for curing. The test piece used in this example has a length of 25 mm and a diameter of 50 mm. After the test piece is made, it is placed in a curing box with a temperature of 25°C, a humidity of 95%, and a curing time of 28 days.

[0060] Example 3

[0061] The present embodiment provides a preparation method of a graphite tailings-based energy-absorbing support material for underground coal mines.

[0062] The graphite tailings of the present embodiment have a continuous gradation of particle sizes of 0.15~10 mm, wherein the particle size range is 0.15~10 mm, the coarse particle size of 5~10 mm accounts for 30%, the medium particle size of 1~5 mm accounts for 40%, and the fine particle size of 0.15~1 mm accounts for 30%, with a clay content of ≤1%.

[0063] The preparation method of the graphite tailings-based energy-absorbing support material for underground coal mines of the present embodiment includes the following steps:

[0064] Step one, raw material pretreatment:

[0065] The graphite tailings are placed in a drying equipment and dried at 105°C for 5h to remove surface free water, and then cooled to room temperature for standby;

[0066] The rubber particles are rinsed with clean water to remove surface dust, then soaked in a 5% silane coupling agent KH-550 ethanol solution for 30 min, and then dried at 80°C for 2h after taking out, to improve the interfacial adhesion between the rubber particles and the cement slurry, and to avoid debonding in the later stage;

[0067] Step two, dry material mixing:

[0068] Based on the mass of cement, the pretreated graphite tailings, cement, steel fiber, and rubber particles are weighed according to the mass ratio of water, cement, graphite tailings, rubber particles and steel fiber as 1:0.78:4.85:0.015:0.035, and then put into a concrete mixer for dry mixing at a rotating speed of 200 r / min for 5 min, to ensure that the cement uniformly wraps the surface of the aggregate;

[0069] Step three, rubber particle mixing:

[0070] The pretreated rubber particles are added into the mixer, and dry mixing is continued for 2 min to uniformly disperse the rubber particles in the dry material system;

[0071] Step four, water stirring:

[0072] The quantitative water is taken according to the proportioning amount, and is added into the mixer in three times, stirring while adding water, the rotating speed is increased to 350 r / min, the total stirring time is 8 min, until a uniform, viscous and no bleeding slurry mixture is formed, the slump is controlled at 120-150 mm;

[0073] Step five, molding and curing:

[0074] For prefabricated support components: the mixture obtained in step four is poured into a mold, vibrated for 3 min with a vibrating table to remove internal bubbles, and then covered with a moisture-proof film after scraping the surface. The test piece used in this example has a length of 100 mm and a diameter of 50 mm. After the test piece is made, it is placed in a curing box with a temperature of 25°C, a humidity of 95%, and a curing time of 28 days.

[0075] Comparative example 1

[0076] This comparative example provides an underground energy-absorbing support material prepared using natural river sand and gravel as aggregate.

[0077] The preparation method of the underground energy-absorbing support material includes the following steps:

[0078] Step one, pretreatment of raw materials:

[0079] The particle size of the natural river sand is 0.15-5 mm, and the particle size of the gravel is 5-10 mm. The natural river sand and gravel are respectively sieved by 10 mm, 5 mm and 0.15 mm grading screens for three-stage screening to remove particles and impurities with particle sizes exceeding the standard; then the sieved river sand and gravel are dried at 105°C for 5 h, and cooled to room temperature for standby;

[0080] Step two, dry material mixing:

[0081] Based on the mass of cement, the pretreated river sand, gravel and cement are weighed according to the mass ratio of water, cement, natural river sand and gravel of 1:0.8:5:0.01, and are put into a concrete mixer for dry mixing at a rotating speed of 200 r / min for 5 min;

[0082] Step three, water stirring:

[0083] The quantitative water is taken according to the proportioning amount, and is added into the mixer in three times, stirring while adding water, the rotating speed is increased to 350 r / min, the total stirring time is 8 min, until a uniform, viscous and no bleeding slurry mixture is formed, the slump is controlled at 120-150 mm;

[0084] Step four, forming and curing:

[0085] For prefabricated support components: pour the mixture obtained in step four into a mold, vibrate for 3 min with a vibrating table, remove internal bubbles, scrape the surface and cover with a moisture-retaining film for curing, the curing temperature is not less than 5 DEG C, the curing time is not less than 7 days, ensure that the cement is fully hydrated, and reach the design strength.

[0086] The prefabricated support components prepared in Example 1 and the prefabricated support components prepared in Comparative Example 1 were subjected to performance tests, and the results are shown in Table 1.

[0087] Table 1

[0088]

[0089] As can be seen from the data in Table 1, the support components prepared in Example 1 of the present application are significantly superior to Comparative Example 1 in terms of 28-day compressive strength, ultimate deformation, energy absorption efficiency, crack resistance and long-term stability. Among them, the compressive strength is increased by about 29%, the ultimate deformation is 3.17 times that of Comparative Example 1, the energy absorption efficiency is increased by nearly 3.5 times, the cracking load is increased by 124%, the 6-month strength retention rate is increased by 15.2%, which fully verifies that the technical scheme of using graphite tailings as the main aggregate and compounding rubber particles and steel fibers can effectively improve the mechanical properties and energy absorption characteristics of the support material, and solve the problem that the strength and toughness of traditional support materials are difficult to balance. At the same time, compared with Comparative Example 1 which needs to pretreat the natural aggregate by grading and screening, the present application utilizes the natural continuous grading characteristics of graphite tailings, which can reduce the equipment investment and labor consumption of the raw material pretreatment link, further highlighting its economy and feasibility in engineering applications.

Claims

1. A method for preparing energy-absorbing support materials for underground coal mines from graphite tailings, characterized in that, Includes the following steps: Step 1: Raw material pretreatment: Graphite tailings are dried and kept for later use; rubber granules are surface-modified with silane coupling agent and then dried for later use. Step 2: Mixing dry ingredients: Weigh out the pretreated graphite tailings, cement and steel fibers according to the proportion, and dry mix them at a certain stirring speed. Step 3: Add rubber granules and mix. Add the pretreated rubber granules to the mixer and continue to dry mix to evenly disperse the rubber granules in the dry material system; Step 4: Add water and stir. Measure a certain amount of water according to the ratio and add it in batches to the dry material system obtained in step three, stirring while adding water until a uniform, viscous slurry mixture without bleeding is formed. Step 5: Shaping and Curing This includes molding for precast support components and molding for on-site casting in the well. The molding for precast support components involves pouring the mixture obtained in step four into a mold, vibrating it to remove internal air bubbles, smoothing the surface, and then covering it with a moisturizing film for curing to ensure that the cement is fully hydrated and reaches the design strength. The molding process for on-site casting in the well is specifically carried out by direct construction using a delivery pump or jetting machine, followed by natural curing in the humid environment of the well to ensure that the cement is fully hydrated and reaches the design strength.

2. The method for preparing underground energy-absorbing support material from graphite tailings according to claim 1, characterized in that, The drying temperature of the graphite tailings in step one is 105±5℃, and the drying time is 4~6h; the silane coupling agent is KH-550, and the modification method is to soak the rubber particles in a 5% silane coupling agent ethanol solution for 30min; the drying temperature of the modified rubber particles is 80±5℃, and the drying time is 2h.

3. The method for preparing underground energy-absorbing support material from graphite tailings according to claim 1 or 2, characterized in that, The graphite tailings are continuously graded with a particle size range of 0.15~10mm. The coarse particles with a particle size of 5~10mm account for 25~30%, the medium particles with a particle size of 1~5mm account for 40~45%, and the fine particles with a particle size of 0.15~1mm account for 25~30%.

4. The method for preparing underground energy-absorbing support material from graphite tailings according to claim 3, characterized in that, The proportions described in step two are as follows: based on the cement mass, the mass ratio of water, cement, graphite tailings, rubber particles, and steel fibers is 1:(0.72-0.8):(4.67-5):(0.01-0.02):(0.03-0.05).

5. The method for preparing underground energy-absorbing support material from graphite tailings according to claim 4, characterized in that, The cement used in step two is of type PO42.5, PO42.5R, PⅠ42.5, PⅡ42.5, PC42.5 or PSA42.5; the steel fibers are steel or iron fibers with a length of 1~1.2cm and a diameter of 0.05~0.15cm.

6. The method for preparing underground energy-absorbing support material from graphite tailings according to claim 5, characterized in that, The stirring speed in step two is 200~300 r / min, and the dry mixing time is 3~5 min.

7. The method for preparing underground energy-absorbing support material from graphite tailings according to claim 6, characterized in that, The rubber particles mentioned in step three are uniform particles with a length of 0.2~0.4cm.

8. The method for preparing underground energy-absorbing support material from graphite tailings according to claim 7, characterized in that, The stirring speed in step four is 350~400 r / min, and the total stirring time is 5~8 min; the slump of the resulting slurry mixture is controlled at 120~150 mm.

9. The method for preparing underground energy-absorbing support material from graphite tailings according to claim 8, characterized in that, The curing temperature of the prefabricated support components described in step five shall not be lower than 5℃, and the curing time shall not be lower than 7 days.

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