A method for anti-corrosion of anchor bolts in coal mine roadways in an alkaline water environment

Abstract

The present invention discloses a method for preventing corrosion of anchor bolts in coal mine roadways in an alkaline water environment. This method comprehensively considers the influence of factors such as the alkaline water chemical environment, the stress state of the anchor bolts, the erosion age (service life), and the diameter of the anchor bolts on the thickness of the hot-dip galvanized layer of the anchor bolts; according to established parameters such as the strength and category of the alkaline water (service object), different positions (both sides, roof, shoulder socket), and the diameter of the anchor bolts in the coal mine roadway, the thickness of the hot-dip galvanized anti-corrosion layer can be determined. This method provides support for the thickness of the hot-dip galvanized layer of anchor bolts in coal mine roadways in an alkaline water environment, and on the basis of improving the anti-corrosion ability of the anchor bolts and the applicability to the geological environment, it avoids the excess or deficiency of the thickness of the hot-dip galvanized layer.

Description

Technical Field

[0001] The present invention relates to the field of surrounding rock control in coal mines, and specifically relates to a method for preventing corrosion of bolts in coal mine roadways in an alkaline water environment. Background Art

[0002] The durability, stability, and effectiveness of the anchoring system are important guarantees for the safe and efficient production of coal mines. Bolts are in a stressed state for a long time, and the harsh working environment causes the bolts to rust, greatly shortening the service life of the bolts. At present, in coal mine production, the stability of the anchoring system is mainly achieved by improving the properties of the surrounding rock and preventing corrosion of the bolt body to cut off the hydraulic connection between groundwater and the bolt.

[0003] In the western mining area, the alkalinity of the aquifer is relatively high, with a local pH value up to 13, and it is rich in ions such as K+, Ca2+, Cl-, SO42-, and Mg2+, which will accelerate the corrosion rate of metal bolts and cause bolt fractures. There are many methods and processes for bolt corrosion prevention, and their essence is to improve the inherent corrosion resistance of metal materials, including coating or plating non-metallic or metallic coatings and chemical conversion films.

[0004] Hot-dip galvanizing is a common method for bolt corrosion prevention. However, as an amphoteric metal, zinc combines with OH- to cause overall or local corrosion. At the same time, the oxide film formed by zinc hydroxide and zinc oxide is damaged under the stressed state of the bolt, further exacerbating the damage of the zinc layer. Although national standards have limited the thickness of the hot-dip galvanized anti-corrosion layer on the threaded rod body, the complex working environment of the mine has not been considered. Therefore, determining the thickness of the hot-dip galvanized bolt anti-corrosion layer under different alkaline water strengths, service times, and stressed states is an urgent problem to be solved for bolt anti-corrosion in coal mine roadways in an alkaline environment. Summary of the Invention

[0005] Aiming at the above-mentioned technical deficiencies, the purpose of the present invention is to provide a method for preventing corrosion of bolts in coal mine roadways in an alkaline water environment, which determines the thickness of hot-dip galvanized bolts based on the alkaline water chemistry environment, stressed state, erosion age, and bolt diameter, and can effectively avoid the erosion of bolts by alkaline water, which is beneficial to the stability, durability, and effectiveness of the anchoring system.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions:

[0007] 2. The present invention provides a method for preventing corrosion of bolts in coal mine roadways in an alkaline water environment, including the following steps:

[0008] S1. Obtain and test the alkaline water strength of the water-filled aquifer in the coal mine roadway in the target area, and divide it into three grades: weakly alkaline, moderately alkaline, and strongly alkaline;

[0009] S2. Calculate the service life of the roadway according to the type of roadway service, and divide it into four time limits: short-term, medium-term, medium-long-term, and long-term;

[0010] S3. Classify into three positions: roof, two sides, and shoulder sockets according to the tensile and shear stress states of the anchor bolts.

[0011] S4. Determine the thickness of the hot-dip galvanized anti-corrosion layer of the anchor bolts by comprehensively considering the alkaline water environment, service life, and stress state of the coal mine roadway.

[0012] Preferably, in step S1, weak alkalinity is pH = 7 - 9, medium alkalinity is pH = 9 - 11, and strong alkalinity is pH > 11.

[0013] Preferably, in step S2, short term is 0 - 5 years, medium term is 5 - 30 years, medium and long term is 30 - 70 years, and long term is greater than 70 years.

[0014] Preferably, the specific method for determining the thickness of the hot-dip galvanized anti-corrosion layer of the anchor bolts in step S4 is as follows:

[0015] a. When the alkaline water strength of the water-filled aquifer in the roadway is weakly alkaline, the minimum thickness of its hot-dip galvanized anti-corrosion layer is:

[0016] (a1) When the service life of the roadway is short term, the thicknesses of the hot-dip galvanized anti-corrosion layers of the shoulder socket, roof, and two-side anchor bolts are 66, 60, and 56 μm respectively;

[0017] (a2) When the service life of the roadway is medium term, the thicknesses of the hot-dip galvanized anti-corrosion layers of the shoulder socket, roof, and two-side anchor bolts are 74, 66, and 60 μm respectively;

[0018] (a3) When the service life of the roadway is medium and long term, the thicknesses of the hot-dip galvanized anti-corrosion layers of the shoulder socket, roof, and two-side anchor bolts are 84, 74, and 66 μm respectively;

[0019] (a4) When the service life of the roadway is long term, the thicknesses of the hot-dip galvanized anti-corrosion layers of the shoulder socket, roof, and two-side anchor bolts are 92, 84, and 74 μm respectively;

[0020] b. When the alkaline water strength of the water-filled aquifer in the roadway is medium alkaline, the minimum thickness of its hot-dip galvanized anti-corrosion layer is:

[0021] (b1) When the service life of the roadway is short term, the thicknesses of the hot-dip galvanized anti-corrosion layers of the shoulder socket, roof, and two-side anchor bolts are 80, 72, and 66 μm respectively;

[0022] (b2) When the service life of the roadway is medium term, the thicknesses of the hot-dip galvanized anti-corrosion layers of the shoulder socket, roof, and two-side anchor bolts are 90, 80, and 72 μm respectively;

[0023] (b3) When the service life of the roadway is medium and long term, the thicknesses of the hot-dip galvanized anti-corrosion layers of the shoulder socket, roof, and two-side anchor bolts are 102, 90, and 80 μm respectively;

[0024] (b4) When the roadway service life is long, the hot-dip galvanized thicknesses of the shoulder socket, roof, and two sides of the roadway bolts are 114, 102, and 90 μm respectively;

[0025] c. When the alkaline water strength of the water-bearing aquifer in the roadway roof is strongly alkaline, the minimum value of the hot-dip galvanized anti-corrosion layer thickness is:

[0026] (c1) When the roadway service life is short, the hot-dip galvanized thicknesses of the shoulder socket, roof, and two sides of the roadway bolts are 116, 104, and 95 μm respectively;

[0027] (c2) When the roadway service life is medium, the hot-dip galvanized thicknesses of the shoulder socket, roof, and two sides of the roadway bolts are 126, 112, and 100 μm respectively;

[0028] (c3) When the roadway service life is medium to long, the hot-dip galvanized thicknesses of the shoulder socket, roof, and two sides of the roadway bolts are 135, 122, and 110 μm respectively;

[0029] (c4) When the roadway service life is long, the hot-dip galvanized thicknesses of the shoulder socket, roof, and two sides of the roadway bolts are 145, 130, and 120 μm respectively.

[0030] Preferably, for the hot-dip galvanized anti-corrosion layer thickness where the bolt diameter ≤ 20 mm, when the bolt diameter is greater than 20 mm, the anti-corrosion layer thickness is increased by an additional 10 μm.

[0031] The beneficial effects of the present invention are as follows:

[0032] (1) The present invention combines the hot-dip galvanized anti-corrosion layer thickness with the alkaline water formation conditions, and fully considers the operating environments of bolts with different diameters, namely different alkaline water strengths, service lives, and stress states, to form a complete system for determining the hot-dip galvanized anti-corrosion layer thickness.

[0033] (2) Especially for the hot-dip galvanized anti-corrosion layer thickness of bolts in roadways with different service lives, while improving the anti-corrosion ability of the bolts, it avoids excessive or insufficient hot-dip galvanized thickness. Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 It is a schematic diagram of the alkaline water environment of the main haulage roadway provided by the embodiment of the present invention;

[0036] Figure 2 For Figure 1Schematic diagram of bolt in Section 1-1;

[0037] Figure 3 Schematic diagram of the alkaline water environment in the mining roadway provided by the embodiment of the present invention;

[0038] Figure 4 is Figure 3 Schematic diagram of bolt in Section 2-2;

[0039] Figure 5 Chart of the hot-dip galvanized anti-corrosion layer thickness of bolts under different alkaline water environments and roadways provided by the embodiment of the present invention;

[0040] Figure 6 Corrosion rate of the hot-dip galvanized layer under different pH value conditions provided by the embodiment of the present invention. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0042] It includes the following steps:

[0043] S1. Obtain and test the alkaline water strength of the water-filled aquifer in the coal mine roadway in the target area, and divide it into three levels: weak alkalinity, i.e., pH = 7 - 9, medium alkalinity, i.e., pH = 9 - 11, and strong alkalinity, i.e., pH > 11;

[0044] S2. Calculate the service life of the roadway according to the service type of the roadway, and divide it into four time limits: short term, i.e., 0 - 5 years, medium term, i.e., 5 - 30 years, medium and long term, i.e., 30 - 70 years, and long term, i.e., > 70 years;

[0045] S3. According to the tensile and shear stress states of the bolts, divide them into three positions: roof, two sides, and shoulder sockets; according to the stress characteristics of the surrounding rock of the roadway, the stress environments of the bolts at these three positions are different;

[0046] S4. Determine the thickness of the hot-dip galvanized anti-corrosion layer of the bolt by comprehensively considering the alkaline water environment, service life, and stress state of the coal mine roadway.

[0047] Preferably, the specific method for determining the thickness of the hot-dip galvanized anti-corrosion layer of the bolt in step S4 is:

[0048] a. When the alkaline water strength of the water-filled aquifer in the roadway is weak alkalinity, the minimum value of the thickness of its hot-dip galvanized anti-corrosion layer is:

[0049] (a1) When the roadway service life is short, the thicknesses of the hot-dip galvanized anti-corrosion coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 66 μm, 60 μm, and 56 μm respectively;

[0050] (a2) When the roadway service life is medium, the thicknesses of the hot-dip galvanized anti-corrosion coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 74 μm, 66 μm, and 60 μm respectively;

[0051] (a3) When the roadway service life is medium to long, the thicknesses of the hot-dip galvanized anti-corrosion coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 84 μm, 74 μm, and 66 μm respectively;

[0052] (a4) When the roadway service life is long, the thicknesses of the hot-dip galvanized coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 92 μm, 84 μm, and 74 μm respectively;

[0053] b. When the alkaline water strength of the water-bearing aquifer in the roadway is moderately alkaline, the minimum thickness of its hot-dip galvanized anti-corrosion coating is:

[0054] (b1) When the roadway service life is short, the thicknesses of the hot-dip galvanized coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 80 μm, 72 μm, and 66 μm respectively;

[0055] (b2) When the roadway service life is medium, the thicknesses of the hot-dip galvanized coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 90 μm, 80 μm, and 72 μm respectively;

[0056] (b3) When the roadway service life is medium to long, the thicknesses of the hot-dip galvanized coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 102 μm, 90 μm, and 80 μm respectively;

[0057] (b4) When the roadway service life is long, the thicknesses of the hot-dip galvanized coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 114 μm, 102 μm, and 90 μm respectively;

[0058] c. When the alkaline water strength of the water-bearing aquifer in the roadway roof is strongly alkaline, the minimum thickness of its hot-dip galvanized anti-corrosion coating is:

[0059] (c1) When the roadway service life is short, the thicknesses of the hot-dip galvanized coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 116 μm, 104 μm, and 95 μm respectively;

[0060] (c2) When the roadway service life is medium, the thicknesses of the hot-dip galvanized coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 126 μm, 112 μm, and 100 μm respectively;

[0061] (c3) When the roadway service life is medium to long, the thicknesses of the hot-dip galvanized coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 135 μm, 122 μm, and 110 μm respectively;

[0062] (c4) When the roadway service life is long, the thicknesses of the hot-dip galvanized coatings for the shoulder sockets, roof, and both sides of the roadway bolts are 145 μm, 130 μm, and 120 μm.

[0063] Preferably, for the hot-dip galvanized anti-corrosion layer, when the diameter of the anchor bolt is ≤ 20 mm, and when the diameter of the anchor bolt is greater than 20 mm, the thickness of the anti-corrosion layer is additionally increased by 10 μm.

[0064] Taking a certain mine in the west as an example, the specific method of this embodiment includes:

[0065] First step: Through on-site investigation and statistics, the alkaline strength of the aquifer in this mine is between 7 and 12, and the distribution is relatively uneven. Taking the main haulage roadway and the mining roadway as examples, the total length of the main haulage roadway is 2,500 m, of which the section from 0 to 1,000 m is the pH = 8 area (weak alkaline), the section from 1,000 to 1,800 m is the pH = 10 area (medium alkaline), and the section from 1,800 to 2,500 m is the pH = 12 area (strong alkaline); the total length of the mining roadway is 800 m, of which the section from 0 to 600 m is the pH = 13 area (strong alkaline), and the remaining section is the pH = 10 area (medium alkaline). See Figures 1-4 ;

[0066] Second step: According to the mine development manual, the recoverable reserves, and the annual output, calculate that the service life of the main haulage roadway is 100 years. According to the reserves, length, and daily output of the working face, calculate that the service life of the mining roadway is 3 years;

[0067] Third step: According to the alkaline water environment and service life determined in the first two steps, and the diameter of the anchor bolt, determine the hot-dip galvanized thickness of the anchor bolts at different positions. The specific results are shown in Figure 5 。

[0068] From Figure 6 It can be seen that as time increases, the reaction rates under different pH conditions are all small and show a constant trend, but as the pH increases, the reaction rate trend shows an exponential growth, which provides a necessary basis for the division of the pH value range.

[0069] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preventing corrosion of anchor bolts in coal mine roadways in an alkaline water environment, characterized in that, It includes the following steps: S1. Obtain and test the alkaline water strength of the water - filled aquifer in the coal roadway of the target formation, and classify it into three levels: weak alkalinity, medium alkalinity, and strong alkalinity; Weak alkalinity means pH = 7 - 9, medium alkalinity means pH = 9 - 11, and strong alkalinity means pH > 11; S2. Calculate the service life of the roadway according to the service type of the roadway, and classify it into four time limits: short - term, medium - term, medium - long - term, and long - term; S3. Classify it into three positions: roof, two sides, and shoulder socket according to the tensile and shear stress states of the bolt; S4. Determine the thickness of the hot - dip galvanized anti - corrosion layer of the bolt by comprehensively considering the alkaline water environment, service life, and stress state of the coal roadway. The specific method for determining the thickness of the hot - dip galvanized anti - corrosion layer of the bolt is as follows: a. When the alkaline water strength of the water - filled aquifer in the roadway is weak alkalinity, the minimum value of its hot - dip galvanized anti - corrosion layer thickness is: (a1)When the service life of the roadway is short, the thicknesses of the hot-dip galvanized anti-corrosion coatings of the shoulder socket, roof, and two sides' bolts are 66, 60, and 56 respectively μ m; (a2)When the roadway service life is in the medium term, the thicknesses of the hot-dip galvanized anti-corrosion coatings of the shoulder sockets, roof, and two sides' bolts are 74, 66, and 60 respectively μ m; (a3) When the roadway service life is medium to long term, the thicknesses of the hot-dip galvanized anti-corrosion coatings for the shoulder sockets, roof, and two sides' bolts are 84, 74, and 66 μ m respectively. (a4)When the roadway service life is long, the thicknesses of the hot-dip galvanized anti-corrosion coatings for the shoulder sockets, roof, and two sides of the roadway bolts are 92, 84, and 74 μ m, respectively. b. When the alkaline water strength of the water - filled aquifer in the roadway is medium alkalinity, the minimum value of its hot - dip galvanized anti - corrosion layer thickness is: (b1) When the roadway service life is short, the hot-dip galvanized thicknesses of the shoulder socket, roof, and two sides' bolts are 80, 72, and 66 μ m respectively. (b2) When the roadway service life is in the medium term, the hot-dip galvanized thicknesses of the shoulder sockets, roof, and two sides of the bolts are 90, 80, and 72 respectively μ m; (b3) When the roadway service life is medium- to long-term, the hot-dip galvanized thicknesses of the bolts in the shoulder sockets, roof, and both sides are 102, 90, and 80 μ m, respectively. (b4) When the roadway service life is long, the hot-dip galvanized thicknesses of bolts in the shoulder sockets, roof, and two sides are 114, 102, and 90 respectively μ m; c. When the alkaline water strength of the water - filled aquifer in the roof of the roadway is strong alkalinity, the minimum value of its hot - dip galvanized anti - corrosion layer thickness is: (c1)When the roadway service life is short, the hot-dip galvanized thicknesses of the shoulder socket, roof, and two sides' bolts are 116, 104, and 95 respectively μ m; (c2)When the roadway service life is in the medium term, the hot-dip galvanized thicknesses of the shoulder sockets, roof, and two sides of the bolts are 126, 112, and 100 respectively μ m; (c3) When the roadway service life is medium to long term, the hot-dip galvanized thicknesses of the bolts in the shoulder sockets, roof, and both sides are 135, 122, and 110 μ m respectively. (c4) When the roadway service life is long, the hot-dip galvanized thicknesses of the shoulder socket, roof, and two sides' bolts are 145, 130, and 120 μ m respectively.

2. The anti-corrosion method for bolts in coal mine roadways in an alkaline water environment according to claim 1, characterized in that, In step S2, the short - term is 0 - 5 years, the medium - term is 5 - 30 years, the medium - long - term is 30 - 70 years, and the long - term is more than 70 years.

3. A method for preventing corrosion of anchor bolts in coal mine roadways in an alkaline water environment, characterized in that, The thickness of the hot-dip galvanized anti-corrosion layer is for anchor bolts with a diameter ≤ 20 mm. When the diameter of the anchor bolt is greater than 20 mm, the thickness of the anti-corrosion layer is additionally increased by 10 μ mm.

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