Elastic material for consolidating closed cracks in goaf and construction method thereof

Abstract

The present invention discloses an elastic material for consolidating closed fissures in goaf and a construction method thereof, wherein the elastic material is prepared by a mixed reaction of component A and component B in a mass ratio of 1:3; the component A includes: 70 to 75 parts of 1,4-phenylenediisocyanate, 18 to 25 parts of polytetrahydrofuran, and 0.5 to 2 parts of waste phosphoric acid; the component B includes: 2 to 7 parts of diethyltoluenediamine, 48 to 55 parts of slag powder, 35 to 42 parts of diisodecyl adipate, and 2 to 6 parts of calcium oxide. During the grouting construction process of the elastomer, cutting before grouting, punching before grouting, sealing of cracks before grouting, and grouting consolidation of crack construction are carried out in sequence. The material used in the present invention is harmless to the human body and the environment, and the material can meet the requirements for use in goaf, and because the material has elasticity after the cracks are consolidated, even if the closed wall is affected by secondary stress, new cracks will not be generated, thereby achieving the desired effect.

Description

Technical Field

[0001] The present invention relates to a material for crack consolidation and a construction method thereof, in particular to an elastic material for consolidating sealed cracks in goaf areas and a construction method thereof, belonging to the technical field of coal mine crack sealing and consolidation. Background Art

[0002] During coal mining, the mined areas are called goafs. As coal remains a vital energy source in my country, coal mining continues, leading to an increasing number of goafs. To prevent air leakage from these goafs and the resulting dangers, they must be sealed. During the mining process, the advancement of the working face creates shifting bearing pressure on both sides of the goaf. Factors such as large-scale construction above the goaf, groundwater disturbances, and geostress disturbances can also activate the goaf, leading to stress redistribution. Under the influence of secondary stresses, the surrounding rock can collapse, fracture, and deform, creating cracks in the goaf's containment walls. These cracks can lead to air leakage. The influx of fresh air into the goaf increases the risk of spontaneous combustion of the remaining coal within. Air leakage can also cause accumulated gas to leak or even explode, resulting in significant casualties and property damage.

[0003] Therefore, it is particularly important to carry out efficient prevention and control of air leakage in closed fissures in goafs. On-site spraying (hard materials such as cement, high-water quick-setting materials or clay) or injection of polymer materials such as Marisol, polyurethane or epoxy resin are generally used to seal air leakage in closed fissures in goafs. However, due to the continuous mining of the adjacent working face, the stress in the goaf is redistributed, and new cracks will appear in the sealed goaf treated by spraying. The reason for the cracks is that the hardness of the sealing material is high after solidification, and it is very easy to break under the action of stress, resulting in the generation of new cracks. Therefore, it is impossible to achieve long-term continuous sealing of air leakage; in addition, most of the polymer materials currently used are harmful to the human body and the environment. The reaction generates a lot of heat during operation, which can easily lead to secondary risks.

[0004] To sum up, how to provide a new consolidation material and construction method for sealing cracks in goaf areas, in which the materials used are harmless to the human body and the environment, and the materials can meet the requirements for use in goaf areas, and even after the cracks are consolidated, the sealed wall will not produce new cracks even if affected by secondary stress. This is the research direction required by the present invention. Summary of the Invention

[0005] In response to the problems existing in the above-mentioned prior art, the present invention provides an elastic material for consolidating closed cracks in goaf areas and a construction method thereof, which can effectively solve the above-mentioned technical problems.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: an elastic material for consolidating closed cracks in goaf areas, wherein the elastic material is prepared by mixing component A and component B in a mass ratio of 1:3, wherein component A is a semi-prepolymer and component B is a curing agent.

[0007] Furthermore, the component A includes: 70-75 parts of 1,4-phenylenediisocyanate, 18-25 parts of polytetrahydrofuran, and 0.5-1.5 parts of waste phosphoric acid; the component B includes: 7-10 parts of diethyltoluenediamine, 48-55 parts of slag powder, 35-42 parts of diisodecyl adipate, and 3-5 parts of calcium oxide.

[0008] Furthermore, the component A includes: 73 parts of 1,4-phenylenediisocyanate, 22 parts of polytetrahydrofuran, and 1 part of waste phosphoric acid; the component B includes: 8 parts of diethyltoluenediamine, 53 parts of slag powder, 38 parts of diisodecyl adipate, and 4 parts of calcium oxide.

[0009] The construction method of the elastic material for consolidating closed cracks in goaf areas comprises the following specific steps:

[0010] Step 1: Cutting before grouting: First observe the distribution of closed cracks, and pre-cut the closed wall to form cracks according to the situation for subsequent grouting;

[0011] Step 2: Drill holes before grouting: Use a drilling machine to alternately construct inclined holes along the closed wall surface on both sides of each crack. Each inclined hole must pass through the crack. After drilling, use a cleaning agent to clean the coal powder and dust around each inclined hole, and then install grouting nails in each inclined hole. After completion, if the width of the closed crack is greater than 1 cm, proceed to step 3; otherwise, proceed directly to step 4.

[0012] Step 3: Crack sealing before grouting: Use sealing tape to seal the crack surface;

[0013] Step 4: Grouting to consolidate cracks: Mix component A and component B in a mass ratio of 1:3 and stir evenly, then use a grouting machine to grout the cracks of the closed wall through the grouting nails in each inclined hole.

[0014] Furthermore, step one specifically includes the following steps: If the cracks are concentrated and have roughly the same direction, the distance between each crack is first determined. A handheld cutter is then used to cut the sealed wall midway between the two cracks with the largest distance. If the cracks are concentrated and have different directions, the handheld cutter is then used to cut the sealed wall, connecting the cracks with different directions. Grouting after cutting connects the elastic material within the cracks, effectively resisting the effects of secondary stress in the goaf.

[0015] Furthermore, the cleaning agent used in the step 2 is prepared by uniformly mixing 4 parts of sodium dodecyl sulfate (SDS) and 96 parts of water according to mass fraction.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The consolidation material used in the present invention is a flame-retardant elastic material that can meet the requirements for use in goaf areas, wherein component A and component B will not produce toxic and harmful substances during the reaction process, and the elastomer after curing is also non-toxic. Its curing speed meets the construction requirements, and since it will form an elastic elastomer after curing, it has good mechanical properties such as compressive strength, tensile strength and shear strength, has good adhesion to the closed wall of the goaf, and can partially deform and buffer when subjected to new stress, thereby preventing new cracks from being generated under the action of secondary stress in the goaf.

[0018] (2) In the present invention, in the cutting work before grouting, pre-cutting is performed according to the distribution of cracks (stress conditions), and the places where the closed wall is most affected by stress are artificially cut to form cracks, i.e. new cracks, and grouting is also performed on the cut cracks to fill the positions with elastic materials, so as to prevent new cracks from being generated when stress acts again.

[0019] (3) The elastic material used in the present invention is an organic polymer material. Although heat is released during the reaction process, in the grouting process of the present invention, components A and B are stirred in advance, and heat release is completed before grouting is completed. There is no risk of spontaneous combustion of coal due to the increase in temperature in the goaf due to the heat release of the reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the cutting process in Example 1 where the cracks are concentrated and oriented in the same direction;

[0021] Figure 2 This is a schematic diagram of the cutting in Example 2 where cracks are concentrated and have inconsistent directions;

[0022] Figure 3 It is a schematic diagram of the punching before grouting of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described below.

[0024] Example 1: The elastic material of this example is prepared by mixing component A and component B in a mass ratio of 1:3, wherein component A is a semi-prepolymer and component B is a curing agent; the component A includes, in parts by mass: 72 parts of 1,4-phenylene diisocyanate, 24 parts of polytetrahydrofuran, and 0.6 parts of waste phosphoric acid; the component B includes, in parts by mass: 10 parts of diethyltoluenediamine, 49 parts of slag powder, 42 parts of diisodecyl adipate, and 3 parts of calcium oxide.

[0025] The construction method of the elastic material in this embodiment comprises the following specific steps:

[0026] Step 1: Cutting before grouting: First observe the distribution of closed cracks, and pre-cut the closed wall to form cracks according to the situation. Specifically: if the distance between the cracks is less than 5m, it can be considered that the cracks are concentrated; if Figure 1 As shown, in this embodiment, the cracks are concentrated and the directions are basically consistent. The distance between each crack is first determined, and the middle position between the two cracks with the largest distance is selected to use a handheld cutting machine to cut the closed wall to form a crack, i.e. a new crack. The width of the cut crack is about 0.1 cm and the depth is about 50 cm, so that the horizontal distance between each crack is less than 2 m for subsequent grouting.

[0027] Step 2: Drilling before grouting: Figure 3 As shown, a punch is used to alternately construct inclined holes along the surface of the closed wall on both sides of each crack. Each inclined hole must pass through the crack. The diameter of the inclined hole is about 2.5 cm, and the vertical distance between the two holes is generally 50 cm. After drilling, the coal powder and dust around each inclined hole are cleaned with a cleaning agent. The cleaning agent used is made by mixing 4 parts sodium dodecyl sulfate (SDS) and 96 parts water according to the mass fraction. Grouting nails are then installed in each inclined hole. After completion, if the width of the closed crack is greater than 1 cm, proceed to step three; otherwise, proceed directly to step four.

[0028] Step 3: Crack sealing before grouting: Use sealing tape to seal the crack surface;

[0029] Step 4: Grouting to consolidate cracks: Mix component A and component B in a mass ratio of 1:3 and stir evenly, then use a grouting machine to grout the cracks of the closed wall through the grouting nails in each inclined hole.

[0030] Example 2: The elastic material of this example is prepared by mixing component A and component B in a mass ratio of 1:3, wherein component A is a semi-prepolymer and component B is a curing agent; the component A includes, in parts by mass: 73 parts of 1,4-phenylene diisocyanate, 22 parts of polytetrahydrofuran, and 1 part of waste phosphoric acid; the component B includes, in parts by mass: 8 parts of diethyltoluenediamine, 53 parts of slag powder, 38 parts of diisodecyl adipate, and 4 parts of calcium oxide.

[0031] The construction method of the elastic material in this embodiment is basically the same as that in the embodiment, and the only difference is the process of crack cutting in step 1. Specifically, if the distance between the cracks is less than 5m, it can be considered that the cracks are concentrated; if Figure 2 As shown, in this embodiment, the cracks are concentrated and the directions are inconsistent, so a handheld cutting machine is used to cut the closed wall to form cracks, and the cut cracks are used to connect the cracks with inconsistent directions for subsequent grouting.

[0032] Example 3: The elastic material of this example is prepared by mixing component A and component B in a mass ratio of 1:3, wherein component A is a semi-prepolymer and component B is a curing agent; the component A includes, in parts by mass: 74 parts of 1,4-phenylene diisocyanate, 19 parts of polytetrahydrofuran, and 1.5 parts of waste phosphoric acid; the component B includes, in parts by mass: 7 parts of diethyltoluenediamine, 55 parts of slag powder, 37 parts of diisodecyl adipate, and 5 parts of calcium oxide.

[0033] The construction method of the elastic material in this embodiment is the same as that in embodiment 1.

[0034] The mechanical properties of the elastic materials of Examples 1 to 3 were tested, and the test results are shown in Table 1:

[0035] Table 1 Mechanical properties test table of elastic materials

[0036] Test items Example 1 Example 2 Example 3 Tensile strength (MPa) 5.1 5.1 4.3 Compressive strength (MPa) 8.2 8.2 8.8 Shear strength (MPa) 3.4 3.4 3.7 Bond strength (MPa) 3.7 3.7 3.2 Solid content (wt%) 98.7 98.7 99.1 Bubble content inside the finished product after curing (%) 0 0 0 Elongation at break (%) 770 780 810 Limiting Oxygen Index (LOI) 37.8 37.8 36.7

[0037] It can be seen from Table 1 that the elastic materials of Examples 1 to 3 have good mechanical properties such as tensile strength, compression strength, and shear strength. After solidification, there are no bubbles inside the solid and the material is flame retardant, which can meet the requirements for crack consolidation in goaf areas.

[0038] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An elastic material for consolidating closed cracks in goaf, characterized in that: The elastic material is prepared by mixing component A and component B in a mass ratio of 1:3, wherein component A is a semi-prepolymer and component B is a curing agent; component A includes: 70-75 parts of 1,4-phenylenediisocyanate, 18-25 parts of polytetrahydrofuran, and 0.5-1.5 parts of waste phosphoric acid; component B includes: 7-10 parts of diethyltoluenediamine, 48-55 parts of slag powder, 35-42 parts of diisodecyl adipate, and 3-5 parts of calcium oxide.

2. The elastic material for consolidating closed cracks in goaf according to claim 1, characterized in that: The component A comprises: 73 parts of 1,4-phenylenediisocyanate, 22 parts of polytetrahydrofuran, and 1 part of waste phosphoric acid; the component B comprises: 8 parts of diethyltoluenediamine, 53 parts of slag powder, 38 parts of diisodecyl adipate, and 4 parts of calcium oxide.

3. A construction method of elastic material for consolidating closed cracks in goaf according to claim 1 or 2, characterized in that: The specific steps are: Step 1: Cutting before grouting: First observe the distribution of closed cracks, and pre-cut the closed wall to form cracks according to the situation for subsequent grouting; Step 2: Drill holes before grouting: Use a drilling machine to alternately construct inclined holes along the closed wall surface on both sides of each crack. Each inclined hole must pass through the crack. After drilling, use a cleaning agent to clean the coal powder and dust around each inclined hole, and then install grouting nails in each inclined hole. After completion, if the width of the closed crack is greater than 1 cm, proceed to step 3; otherwise, proceed directly to step 4. Step 3: Crack sealing before grouting: Use sealing tape to seal the crack surface; Step 4: Grouting to consolidate cracks: Mix component A and component B in a mass ratio of 1:3 and stir evenly, then use a grouting machine to grout the cracks of the closed wall through the grouting nails in each inclined hole.

4. The construction method according to claim 3, characterized in that: The step 1 specifically includes: if the cracks are concentrated and have basically the same direction, first determine the distance between each crack, select the middle position between the two cracks with the largest distance, and use a handheld cutting machine to cut the closed wall to form a crack; If the cracks are concentrated and inconsistent in direction, use a handheld cutting machine to cut the closed wall to form cracks, and make the cut cracks connect the cracks with inconsistent directions.

5. The construction method according to claim 3, characterized in that: The cleaning agent used in the step 2 is prepared by uniformly mixing 4 parts of sodium lauryl sulfate and 96 parts of water in parts by mass.

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