WO2020192055A1 - Two-step grouting modified water-protective coal mining method for roof aquifers - Google Patents

Abstract

A two-step grouting modified water-protective coal mining method for roof aquifers, comprising a coal seam and an aquifer located above the coal seam, and the specific steps implemented being: acquiring a parameter; obtaining a first spatial range by means of calculation; arranging a plurality of first grouting boreholes; injecting a first grout into a bottom portion of the aquifer, and performing normal extraction; using the parameter to calculate a second spatial range into which a second grout is to be injected; boring out a second grouting borehole; and then injecting a second grout having a high strength and a low permeability. The beneficial effect is: the present method respectively injects grouts of different materials into a roof aquifer before and after mining, in one aspect increasing the thickness of the aquiclude before mining, and weakening disturbances to the roof aquifer from coal seam mining, and in another aspect, also being able to prevent the aquifer and the mining area from being communicated by a water-conducting fracture after mining, thus implementing water-protective coal mining.

Description

Two-step grouting modified water-preserving coal mining method for roof aquifer Technical field

The invention relates to a water-preserving coal mining method in the field of mining, in particular to a two-step grouting modified water-preserving coal mining method for a roof aquifer.

Background technique

During the mining process, the overlying rock moves and deforms to form a water channel, which connects the roof aquifer and the mined area, causing a large loss of water resources, and even poses a safety hazard to the mining space such as coal seam faces and roadways, especially for my country For mines in the west where water resources are scarce and the ecological environment is fragile, these problems are even more serious. How to reduce the disturbance of coal seam mining to the roof aquifer and prevent the aquifer from passing through the goaf is one of the key issues that must be solved to achieve safe and water-preserving mining.

At present, there have been many studies and practices on the treatment of aquifers, and good results have been achieved. For example, drilling the roof aquifer water in advance through construction drilling to reduce the water richness of the aquifer; grouting into the water-conducting fissures formed by mining to block the water-conducting fissures to prevent the influx of water.

However, these methods have the following problems: (1) From the perspective of mine flood prevention, the aquifer is released to reduce potential safety hazards, but causes a large amount of water loss; (2) At present, grouting into the aquifer is mainly used To prevent and control floor confined flood disasters, there are fewer applications for roof aquifers; (3) Previous studies mostly used plugging after cracks in the roof after mining to treat roof water damage, but a large amount of water loss has occurred at this time; ( 4) The protection of the roof aquifer is mostly achieved at the expense of resource recovery and mining efficiency, such as increasing the thickness of the remaining coal pillars, limiting the mining height, and adopting filling mining methods.

Therefore, in view of the limitations of existing research, a two-step grouting modified water-preserving coal mining method for roof aquifer is proposed.

Summary of the invention

The object of the present invention is to provide a two-step grouting modified water-preserving coal mining method for the roof aquifer to solve the problems raised in the background art.

In order to achieve the above objectives, the present invention provides the following technical solutions:

A two-step grouting modified water-preserving coal mining method for roof aquifer includes a coal seam and an aquifer located above the coal seam, and further includes the following steps:

a. Obtain the basic geological parameters and mining technical parameters of the work site; calculate the first spatial range of the aquifer and aquifer that needs to be modified before mining;

b. In the first space range in step a, a number of first grouting boreholes are arranged at intervals from the surface to the bottom of the aquifer, and the first grouting boreholes include vertical boreholes, borehole deflection sections and bonding Horizontal boreholes at the bottom of the aquifer;

c. The ground grouting pump station injects the first slurry with flexibility and water resistance into the bottom of the aquifer in step b through the first grouting borehole to modify the aquifer;

d. After the grouting modification is completed, carry out normal mining on the working face of the coal seam;

e. After the coal seam working face is mined, calculate the second space range into which the second slurry is injected according to the parameters in step a;

f. Drill a second grouting borehole from the surface to the second space range, and then go through the second grouting borehole and/or the first grouting borehole from the ground grouting pump station. A second grout with high strength and low permeability may be injected into new water-conducting fissures caused by stable overburden activity.

An embodiment of the present invention: the basic geological parameters and mining technical parameters mentioned in step a include: the distance H from the aquifer to the coal seam, the inclination angle α of the coal seam, the mining height m of the working face to be mined, the strike length l, the inclined length l', and the rock formation Moving angle trend δ, uphill β, downhill γ, roof subsidence coefficient q, further, calculate the space size of the aquifer that needs to be modified is: along the direction of the working face, the thickness from the bottom of the aquifer d=qm cosα, length L=1+2H cotδ, length along the inclination direction of the working face B=l′+H(cotβ+cotγ), the grouting modification range of the aquifer is the L×B×d space directly above the working face from the bottom of the aquifer area.

An embodiment of the present invention: the first grouting borehole in step b further includes several horizontal branch boreholes separated from the horizontal borehole.

An embodiment of the present invention: as in step c, the first slurry is a clay slurry.

An embodiment of the present invention: the grouting step of injecting the first slurry in step c is:

①The first use of dilute slurry is mainly to plug the cracks in the lower part of the aquifer and solidify the lower water;

②Inject thick slurry again, and adjust the grouting pressure to ensure that the slurry fills the area to be grouted and is evenly distributed until it reaches the expected thickness of the water barrier.

An embodiment of the present invention: the second slurry in step e is a high-strength and low-permeability slurry formed by mixing water, cement slurry, and water glass.

An embodiment of the present invention: the second space range described in step e is a closed annular structure, and the specific dimensions are as follows: in the direction of the working face, the width of the solid coal side from the top of the coal wall is Hcotδ, along the working face In the direction of inclination, an annular area with the width of H cot γ and H cot β at the upper and lower ends of the solid coal side from directly above the coal wall.

Compared with the prior art, the present invention has the following beneficial effects: the method injects slurry of different materials into the roof aquifer before and after mining. On the one hand, the thickness of the water barrier is increased before mining and the impact of coal mining is reduced. The disturbance of the roof aquifer, on the other hand, can also prevent the post-harvest water conducting fissures from connecting the aquifer and the mined-out area, thereby realizing water-retaining mining.

Description of the drawings

Figure 1 is a schematic diagram of the front structure of the present invention;

Figure 2 is a top view of the modified aquifer of the present invention;

Fig. 3 is a cross-sectional view at A-A in Fig. 2.

In the picture: 1. Ground grouting pump station, 2. The first grouting borehole, 3. The surface soil layer, 4. Aquifer, 41 water barrier, 5. Coal seam, 6. Working face, 7. The first space, 8. Goaf, 9. Second space, 91, second grouting hole.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described below 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

In the background art, the technical problem to be solved by this application is described in detail, that is, a coal mining method that can not only retain water but also increase the output rate is proposed. The specific implementation may be as follows:

As shown in Figure 1, a two-step grouting modified water-preserving coal mining method for roof aquifers includes coal seam 5 and aquifer 4 located above coal seam 5. Under normal circumstances, when coal seam 5 is mined, it will cause water The rock layer of the water barrier 41 below layer 4 has broken cracks. When the cracks continue to develop and communicate with the aquifer and the coal seam, water inrush will form. Before using the method of this application, you need to implement the following steps:

As shown in Figure 1, a. Obtain the basic geological parameters and mining technical parameters of the work site. There are many ways to obtain the parameters. You can use field surveys or query data. The main parameters obtained include the distance H from the aquifer 4 to the coal seam, the coal seam inclination α, The mining height m, strike length l, inclination length l', strata movement angle strike δ, uphill β, downhill γ, roof subsidence coefficient q of working face 6 to be mined are calculated, and it is concluded that modification is required before mining. The first spatial extent of the aquifer 4 and the water barrier 41. The spatial scope here specifically refers to the spatial dimensions of the aquifer that needs to be modified: along the direction of the working surface, the thickness from the bottom of the aquifer 4 is d=qm cosα, the length L=l+2Hcotδ, along the direction of the working surface’s inclination The length B=l′+H(cotβ+cotγ), the grouting modification range of the aquifer 4 is the space area L×B×d directly above the working surface from the bottom of the aquifer.

As shown in Figures 1 and 2, b. In the range of the first space 7 described in step a, several first grouting boreholes 2 are arranged at intervals from the surface to the bottom of the aquifer. The first grouting boreholes include vertical boreholes. , Borehole deflection section and horizontal borehole that fits the bottom of the aquifer. In order to ensure that the entire L×B×d space at the bottom of the aquifer 4 is modified by the first slurry, a first grouting borehole 2 needs to be drilled at intervals on the ground surface. The specific spacing distance is It can be calculated according to the water permeability of the aquifer 4 on site.

In order for the first grouting borehole 2 in step b to make the first grout more comprehensively modify the aquifer 4, the first grouting borehole 2 can also include several levels separated from the horizontal borehole. Branch drilling. The horizontal branch drilling here belongs to the existing technology in the field of drilling and will not be detailed here.

c. The ground grouting pump station injects the first slurry with flexibility and water resistance into the bottom of the aquifer 4 in step b through the first grouting bore 2 to modify the aquifer 4.

The specific formulation of the first slurry used may be a clay-based slurry, and more specifically, the formulation of the first slurry may be clay: water: cement = 5:10:1.

Moreover, in order to better inject the first slurry into the rock formation of the aquifer 4, the following operating methods can be followed:

①First, the thin slurry is used to plug the cracks in the lower part of the aquifer 4 and solidify the lower water;

②Inject thick slurry again, and adjust the grouting pressure to ensure that the slurry fills the area to be grouted and is evenly distributed until the thickness of the water barrier layer 41 is expected to be transformed.

According to the capillary theory, the thinner first slurry can quickly diffuse into the capillaries inside the aquifer 4, and this diffusion can block all the capillaries in the aquifer 4, thus transforming the aquifer 4 into a water barrier 41 in a disguised form. . Then inject the thick slurry, which can block the thicker capillary tube. Through the above method, the purpose of modifying the aquifer 4 is achieved.

As shown in Figure 3, d. After the grouting modification is completed, the working face 6 of the coal seam 5 is normally recovered, but because the aquifer 4 has been modified and has a certain anti-interference ability, it can ensure the entire aquifer 4 There will be no water inrush.

As shown in Fig. 3, the present invention takes into account the roof subsidence of the working face, and the modified aquifer 4 has a more important function: the height of the modified aquifer 4 can just supplement the depression caused by the subsidence.

As shown in Figs. 2 and 3, although the aquifer 4 does not incur water inrush in step d, due to the sinking of the roof of the working face, new tensile cracks will appear on the edge of the modified aquifer 4. Therefore, in order to eliminate hidden dangers, in step e, after the coal seam face is mined, the second space 9 range into which the second slurry is injected is calculated according to the parameters in step a, and the specific range is as follows:

The scope of the second space 9 is a closed ring structure. The specific dimensions are as follows: in the direction of the working face, the width of the solid coal side is H cot δ from the top of the coal wall, and in the direction of the working face, at the upper and lower ends of the coal The width of the solid coal side on the upper side of the wall is an annular area with Hcotγ and Hcotβ respectively. The specific working process is as step f: drill a second grouting borehole 91 from the surface to the second space range, and then pass the second grouting borehole 91 and/or the first grouting hole from the ground grouting pump station 1 Drill hole 2 injects a second slurry with high strength and low permeability into new water-conducting fractures that may be generated due to unstable overburden activity after step d.

The second slurry may be a mixture of water, cement slurry, and water glass. Specifically, the ratio of water: cement: water glass is 2:2:3.

The principle of the present invention is roughly divided into two steps: The first step is to modify the bottom of the aquifer 4 into a water barrier. Since the bottom of the aquifer 4 itself is above the original water-resistant layer 41, and because of the use of clay slurry, the anti-disturbance ability is relatively strong. Therefore, after the modification, when the original water-resistant layer 41 is broken, the first slurry used will be Play a water barrier function; on the other hand, after the modified aquifer 4 is superimposed on the barrier layer 41, the thickness of the barrier layer is increased. This extra thickness will be used to supplement the height difference of the subsidence of the goaf .

The second step of the present invention is to re-grouting to block the newly emerging cracks at the edge of the modified aquifer 4. In addition to plugging the cracks, the second step has another role: A pulling force on the edge of 4 allows the modified aquifer 4 and the second slurry to form a whole, which can ensure that the water source of the entire water layer will not be exhausted, and the use of this method can also mine all the coal in the entire working face 6 To improve output efficiency.

The practical application of the present invention will be described below in conjunction with a specific implementation case.

The surface ecological environment of a mine in northwest my country is harsh and water resources are scarce. According to the mine data, the study coal seam is a nearly horizontal coal seam, with a 7° coal seam inclination, a coal seam depth of 260m, a mineable coal seam thickness of 8m, a working face advance length of 1800m, and a working face length of 200m. Coal mining method is used for mining, and the roof is managed by all caving methods. After geological exploration, there is an aquifer with a thickness of about 15m at 165m above the coal seam. The data shows that under the conditions of this area, the mining subsidence coefficient is 0.6, and the rock movement angles are: strike movement angle 65°, downhill movement angle 55°, Uphill movement angle is 60°. Under the original mining method, water resources were lost seriously.

1) Obtain the basic geological parameters and mining technical parameters of the working face. By consulting the basic information of the mine, the distance between the aquifer and the coal seam is H=165m, the thickness of the aquifer is 15m, the inclination angle of the coal seam is α=7°, the buried depth of the coal seam is 260m, the thickness of the mineable coal seam is m=8m, and the working face advance length l=1800m. The surface length l'=200m. The mining subsidence coefficient q=0.6, and the rock formation movement angles are: strike movement angle δ=65°, downhill movement angle β=55°, and uphill movement angle γ=60°.

2) Before mining at the working face, grouting is modified to a certain range from the bottom of the aquifer. The specific steps are:

(1) Before mining the working face, firstly determine the pre-mining grouting modification range by calculation according to the basic parameters: thickness from the bottom of the aquifer d=qmcosα, length along the strike direction of the working face L=l+2Hcotδ, along the working face Inclination direction length B=1'+H(cotβ+cotγ). Substituting the relevant parameters into the formula to calculate, the bottom thickness of the aquifer is d=0.6×8×cos7°=4.8m, the length along the strike direction of the working face is L=1800+2×165×cot65°=1954m, along the direction of the working face’s inclination Length B=200+165×(cot55°+cot65°)=411m, then the range of grouting is 1954m×411m×4.8m from the bottom of the aquifer directly above the working surface, forming the first in Figure 1. Space 7.

(2) According to the position of the aquifer detected in 1) and the range of grouting modification obtained by calculation, grouting boreholes are arranged into the aquifer from the ground grouting pump station. The hole-making section, horizontal drilling and horizontal branch drilling are composed of four parts. As shown in Figure 1 (2), the vertical borehole is drilled to a buried depth of 55m, and the vertical distance from the aquifer is 20m-30m, which provides sufficient bending space for the subsequent drilling and deflection; The main borehole can be drilled into the lower part of the aquifer horizontally; the horizontal borehole is arranged at the position of the reconstructed aquifer calculated by calculation, the strike length is 1980m, which is slightly longer than the strike length L of the aquifer, and runs through the entire working surface; Adjust the position of the drill pipe, arrange several branch boreholes in the grouting modification area of the aquifer. The length of the branch boreholes is 420m. The arrangement method is evenly distributed to ensure that the injected slurry can be evenly distributed in the determined area to form the expected thickness Water barrier.

(3) Clay solidification slurry is used for grouting slurry, and the ratio is clay: water: cement = 5: 10:1, and appropriate amount of water glass can be added to increase the setting speed appropriately according to the situation. The grouting sequence adopts the first thin and then thick grouting method. The thin and thick slurry mainly plays the role of plugging the cracks in the lower part of the aquifer and solidifying the lower water. Then the thick slurry is injected, and the grouting pressure is adjusted to ensure The grout fills the area to be grouted and is evenly distributed until it reaches the expected thickness of the reconstructed water barrier.

3) After the pre-mining grouting modification is completed, the working face shall undergo normal mining.

4) After mining on the working face, the modified water-resistant layer is affected by mining, especially the deformation of the overlying rock layer causes tension cracks in some areas above the mining boundary roof. It is necessary to plug these possible water conduction through grouting strength Rift. The specific steps are:

(1) After mining of the working face, firstly, according to the basic parameters, the second space 9 range of post-mining grouting is calculated: in the strike direction of the working face, the width of the solid coal side from the top of the coal wall is Hcotδ, In the direction of face inclination, at the upper and lower ends, the width of the solid coal side from directly above the coal wall is Hcotγ and Hcotβ respectively. Substituting the relevant parameters into the formula to calculate, the width of the area to be grouted on both sides of the solid coal along the strike direction of the working face is Hcotδ=165×cot65°=77m, and the width of the solid coal side at the upper end of the working face is Hcotγ=165×cot60°=95m, and the width of the solid coal side at the lower end is Hcotβ=165×cot55°=116m. The grouting range is an annular area.

(2) As shown in Figure 3, the drilling holes are directly arranged from the ground to the area where grouting is required. The final hole is drilled into the bottom of the reconstructed water barrier. The drilling depth is 95m and is located at the center of the grouting range. The holes are arranged every 50m in the direction of direction and inclination. The inclined grouting length of this working face is 411m, and the strike grouting length is 1954m. Therefore, 8 grouting holes are arranged on each side of the inclined direction, and 40 grouting holes are arranged on each side of the strike direction.

(3) It is recommended to use high-strength, low-permeability grout for the grouting material. In this example, the grouting slurry chooses water glass and cement slurry mixed slurry, and the ratio is water: cement: water glass = 2:2:3.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. And variations, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (8)

1. A two-step grouting modified water-preserving coal mining method for roof aquifers includes a coal seam (5) and an aquifer (4) located above the coal seam (5), and is characterized in:

   a. Obtain the basic geological parameters and mining technical parameters of the work site; calculate the first space (7) range of the aquifer (4) and the aquifer (41) that need to be modified before mining;

   b. In the range of the first space (7) in step a, a number of first grouting boreholes (2) are arranged at intervals from the surface to the bottom of the aquifer, and the first grouting boreholes (2) include vertical boreholes , Borehole skew section and horizontal borehole at the bottom of the aquifer (4);

   c. The ground grouting pump station injects the first slurry with flexibility and water resistance into the bottom of the aquifer (4) in step b through the first grouting borehole (2), so that the aquifer (4) is modified ；

   d. After the grouting modification is completed, carry out normal mining on the working face (6) of the coal seam;

   e. After the coal seam working face (6) is mined, calculate the second space (9) range into which the second slurry is injected according to the parameters in step a;

   f. Drill a second grouting borehole (91) from the surface to the second space (9), and then pass the second grouting borehole (91) and/or the second grouting borehole (91) from the ground grouting pump station (1) A grouting borehole (2) injects a second grout with high strength and low permeability into new water-conducting fissures that may be caused by unstable overburden activities after mining in step d.
2. The two-step grouting modified water-preserving coal mining method for roof aquifer according to claim 1, wherein the basic geological parameters and mining technical parameters in step a include: the distance between the aquifer (4) and the coal seam (5) H. Coal seam (5) dip angle α, working face to be mined (6) mining height m, strike length l, dip length l, rock movement angle (strike δ, uphill β, downhill γ), roof subsidence coefficient q.
3. The two-step grouting modified water-preserving coal mining method for roof aquifers according to claim 2, characterized in that the spatial dimensions of the aquifer to be modified are: along the strike direction of the working face (6), from the aquifer (4) Thickness from the bottom d=qmcosα, length L=l+2Hcotδ, length B=l′+H(cotβ+cotγ) along the inclination direction of working face (6), the grouting modification range of aquifer (4) is working face (6) The space area L×B×d from the bottom of the aquifer (4) directly above.
4. The two-step grouting modified water-preserving coal mining method for roof aquifers according to claim 1, characterized in that: in step b, the first grouting borehole (2) also includes several levels separated from the horizontal borehole Branch drilling.
5. The two-step grouting modified water-preserving coal mining method for roof aquifers according to claim 1, wherein the first slurry in step c is a clay slurry.
6. The two-step grouting modified water-preserving coal mining method for roof aquifer according to claim 1, wherein the grouting step of injecting the first slurry in step c is:

   ①The thin slurry is used first to plug the cracks in the lower part of the aquifer (4) and to solidify the lower water;

   ②Inject thick grout again, and adjust the grouting pressure to ensure that the grout fills the area to be grouted and is evenly distributed until it reaches the expected thickness of the reconstructed water barrier (41).
7. The two-step grouting modified water-preserving coal mining method for roof aquifers according to claim 1, wherein the second slurry in step e is a high-strength and low-permeability slurry mixed with water, cement slurry and water glass.
8. The two-step grouting modified water-preserving coal mining method for roof aquifer according to claim 2, characterized in that: the second space (9) in step e is a closed annular structure, and the specific dimensions are as follows: In the strike direction of face (6), the width of the solid coal side from the upper direction of the coal wall is Hcotδ, and along the inclination direction of the working face (6), the width of the solid coal side at the upper and lower ends and from the upper direction of the coal wall is Hcotγ, An annular region of Hcotβ.

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