WO2021093122A1

WO2021093122A1 - Method for reducing withdrawal roadway roof pressure at end of coal face mining

Info

Publication number: WO2021093122A1
Application number: PCT/CN2019/129988
Authority: WO
Inventors: 宁建国; 邱鹏奇; 商和福; 李学慧; 王俊; 胡善超
Original assignee: 山东科技大学
Priority date: 2019-11-15
Filing date: 2019-12-30
Publication date: 2021-05-20
Also published as: CN110847909A; CN110847909B

Abstract

Disclosed is a method for reducing withdrawal roadway roof pressure at the end of coal face mining, comprising the following steps: step 1, determining an optimum distance between a final fracture position of a main roof (1) of a coal face and a non-production side of a withdrawal roadway (7); step 2, calculating the critical size of separated coal pillars (8) between the coal face and the withdrawal roadway (7); step 3, determining a stop-mining isobaric position; and step 4, implementing, when the coal face reaches the stop-mining isobaric position, a stop-mining isobaric pressure on the basis of the optimum stop-mining isobaric position determined in step 3, and after a roof weighting phenomenon occurs after the mining of the coal face has stopped for a period of time, continuing to mining the coal face to a stop line to complete coal mining operations. The problem of high withdrawal roadway roof pressure at the end of coal face mining can be solved, and the periodic weighting position of the main roof is changed by taking a stop-mining isobaric pressure measure in an appropriate position at the end of coal face mining, thereby reducing the withdrawal roadway roof pressure at the end of coal face mining, and ensuring the smooth withdrawal of the coal face.

Description

Method for reducing roof pressure of withdrawal channel at the end of coal mining face

Technical field

The invention relates to the field of coal mining pressure control, in particular to a method for reducing the roof pressure of a withdrawal channel at the end of coal mining face mining.

Background technique

When deploying the production system of the working face in underground coal mining, the retracement channel is often excavated in advance, and the roadway is supported by bolts, meshes and cables. When the working face is far from the retracement channel, the retracement channel is used as a connecting lane. When the working face is 200-400m away from the retreat channel, a stacking support control roof shall be arranged in the roadway in advance. When the working face is pushed to the position of the withdrawal channel, stop the working face, and the withdrawal channel is used as the mechanical equipment withdrawal space of the working face, which saves the time of the excavation and withdrawal space at the end of the working face, so as to speed up the final mining of the coal face. speed.

However, in many coal working faces, the roof pressure occurs at the end of the mining stage, and the roof is basically on the upper part of the withdrawal channel or the front part is broken, and the basic roof slips and falls instability or drastically rotates and sinks. The hydraulic support at the lower part of the basic roof will bear huge pressure. The expansion and contraction of the pillars dropped sharply, or even crushed. The basic roof transmits the huge pressure it bears to the surrounding rock of the retreat channel, and the roadway roof is broken, the coal wall is smashed, and the bottom heave appears. The height of the hydraulic support is insufficient, and the convergent deformation of the retreat channel is serious, resulting in insufficient retreat space, which brings difficulties to the retreat of face equipment. In order to ensure the normal use of the withdrawal channel, a lot of manpower and material resources need to be spent on repairing the roadway.

Summary of the invention

technical problem

At present, in order to solve the problem of roof pressure at the end of mining, some adopt the method of cutting roof and pressure relief in the final mining withdrawal channel of coal mining face, such as drilling a deep hole pre-splitting drill at the middle position of the roof in the withdrawal channel. Then, load the explosives to blast and release the pressure, or set up a fracturing hole on the top plate of the retreat channel, and then perform the hydraulic fracturing and pressure relief treatment. However, the above method has problems such as cumbersome operation, labor consuming, and high cost for implementation.

The solution to the problem

Technical solutions

Based on the above technical problems, the present invention proposes a method for reducing the roof pressure of the withdrawal channel at the end of the mining face.

The technical solution adopted by the present invention is:

A method for reducing the roof pressure of the withdrawal channel at the end of the coal mining face, including the following steps:

The first step is to determine the best distance between the final fracture position of the basic top of the coal mining face and the non-production side of the withdrawal channel

The optimal distance between the final fracture position of the basic roof of the coal mining face and the non-production side of the withdrawal channel is calculated by formula (1):

W ₀ ＝w ₁ +w ₂ +w ₃ (1)

In formula (1): W ₀ is the best distance between the final fracture position of the basic roof and the non-production side of the withdrawal channel, m; W ₁ is the width of the withdrawal channel, m; W ₂ is the working face hydraulic support control roof distance, m ; W ₃ is the distance between the hydraulic support in the working face after the penetration and the stack support in the withdrawal channel, m;

The second step is to calculate the critical dimension B of the coal pillar between the working face and the withdrawal channel

The critical size of the spaced coal pillar between the working face and the withdrawal channel is calculated by formula (2):

B=X ₀ +X ₁ +2m (2)

In formula (2): B is the critical size of the interval coal pillar, m; X ₀ is the width of the plastic zone of the coal body in front of the working face, m; X ₁ is the width of the plastic zone of the coal body on the side of the production side of the withdrawal channel, m; m is the height of the retracement channel, m;

_{Among them, the width X 1} of the plastic zone of the coal body on the side of the production side of the withdrawal channel is calculated by formula (3):

In formula (3): m is the height of the retracement channel, m; A is the lateral pressure coefficient;

Is the internal friction angle of the coal seam, °; C ₀ is the coal seam cohesion, MPa; k ₁ is the stress concentration factor caused by roadway excavation; γ is the bulk density of the overlying rock mass, KN/m ³ ; H is the thickness of the overlying rock mass, m;

_{The width X 0} of the plastic zone in the front coal body caused by the mining face is calculated by formula (4):

In formula (4): d is the coal mining height of the working face, m; f is the friction coefficient between the coal seam and the roof, k ₀ is the stress concentration factor caused by the excavation of the working face, and P ₀ is the resistance of the hydraulic support to the coal bank, MPa ; Ε is the triaxial stress coefficient, and its expression is as follows:

The third step is to determine the isostatic position of stopping mining

According to formula (5) to calculate the best stop isobaric position:

S=W ₀ +(n·L) (5)

In the formula (5): S is the optimal stop and equal pressure position; W ₀ is the optimal distance between the final fracture position of the basic top of the coal mining face and the non-production side of the withdrawal channel, m; n is an integer, taking the value 1. 2, 3, 4...; L is the basic top break step distance of the working face, m;

Use formula (6) and formula (7) to constrain the value of n:

w ₂ +w ₃ +n·L≥B (6)

W ₀ +(n·L)=M-〔1/2～1〕·L (7)

In formula (7): M is the distance between the basic roof fracture position and the stop line before the stop isobaric at the working face, m;

Take the minimum value of n that satisfies the above formula (6) and formula (7), and then substitute it into formula (5) to calculate the best stop isobaric position;

The fourth step is based on the optimal stop isostatic position determined in the third step. When the coal mining face reaches the stop isostatic position, the stop isostatic pressure is implemented, and the roof will appear after stopping mining for a period of time. If there is a sign of pressure, then continue to push the working face to the stop line to complete the coal mining operation.

The beneficial effects of the invention

Beneficial effect

Implementing the method of stopping mining and isostatic pressure of the present invention at the end of the working face can change the position of the basic roof fracture, so that the basic roof is broken at a reasonable position, and finally achieve the purpose of reducing the mine pressure of the withdrawal channel at the end of the working face and ensure the safe use of the withdrawal channel . Compared with the top-cutting and pressure relief method of the withdrawal channel, it has the advantages of simple operation, low implementation cost, and higher safety.

Brief description of the drawings

Description of the drawings

The present invention will be further described below in conjunction with the drawings and specific embodiments:

Fig. 1 is a diagram of the best fracture position of the basic roof when the working face is stopped in the present invention;

Figure 2 is a diagram of the basic roof fracture position before and after the working face is stopped and isobaric in the present invention; (a) is the rock movement diagram when the working face is stopped and isobaric; (b) is the working face when the working face is stopped after the mining is stopped and isobaric Diagram of rock formations movement.

In the figure: 1. Basic roof, 2. Direct roof, 3. Coal seam, 4. Basic roof with a length of L, 5. Basic roof with a length of (0.5～1)L, 6. Hydraulic support, 7 .Retracement channel, 8. Space coal pillar between the retreat channel and the working face, 9. Stop mining line of the working face, 10. Stack support.

Invention embodiment

Embodiments of the present invention

In view of the possibility of roof pressure at the end of the coal mining face, which may cause difficulty in the end of the working face, the present invention adopts a method of stopping mining and equal pressure when the working face is advanced to a suitable position. As shown in Figure 2, the basic roof is fractured in advance, Then change the position of the basic jacking period to press, and when the working face stops mining, the basic jack breaks at the optimal position, as shown in Figure 1, the phenomenon of the emergence of the rock pressure in the withdrawal channel is minimized.

A more detailed description will be given below in conjunction with the drawings.

The first step is to determine the best distance between the final fracture position of the basic top of the coal mining face and the non-production side of the withdrawal channel (stop mining line)

In order to ensure that the emergence of underground pressure in the withdrawal channel is minimized and the roadway convergence and deformation are minimized, it is first necessary to determine the best distance between the final fracture position of the basic roof 1 and the non-production side of the withdrawal channel 7 (stopping line 9) when the working face stops mining. . This breaking position of the roof is most beneficial to the stability of the withdrawal channel.

As shown in Figure 1, the optimal distance between the final fracture position of the basic roof and the non-production side of the retracement channel (stop mining line 9) satisfies the formula (1):

W ₀ ＝w ₁ +w ₂ +w ₃ (1)

In formula (1):

W ₀ -The best distance between the final fracture position of the basic top 1 and the non-production side of the retracement channel 7 (stop mining line 9), m;

W ₁ -Width of retracement channel, m;

W ₂ -Controlling top distance of hydraulic support in working face, m;

W ₃ -The distance between the hydraulic support in the working face after the penetration and the stack support in the withdrawal channel, m.

The second step is to calculate the critical size of the coal pillar 8 between the working face and the withdrawal channel 7

At the end of the working face, stop and equal pressure, leave a certain size of interval coal pillars between the stop and equal pressure position and the withdrawal channel (as shown in Figure 2(a)). The size of the spaced coal pillars should not be too small, otherwise the coal pillars will be damaged and the basic roof will not break at a reasonable position. The critical size of the spaced coal pillars is calculated by formula (2):

B=X ₀ +X ₁ +2m (2)

In formula (2):

B- the critical size of the interval coal pillar, m;

X ₀ -the width of the plastic zone in front of the coal body caused by mining at the working face, m;

X ₁ -The width of the coal body plastic zone on the production side of the withdrawal channel, m;

m-the height of the retracement channel, m.

_{The width X 1} of the coal body plastic zone on the side of the production side of the withdrawal channel is calculated by formula (3):

In formula (3):

m-the height of the retracement channel, m;

A-side pressure coefficient;

-The internal friction angle of coal seam 3, °;

C ₀ -the cohesion of coal seam 3, MPa;

k ₁ -Stress concentration factor caused by roadway excavation;

γ- Bulk density of the overlying rock mass, KN/m ³ ;

H- thickness of overlying rock mass, m;

In formula (4):

d- coal mining height of working face, m;

ε-triaxial stress coefficient, its expression is as follows:

f-Coefficient of friction between coal body and roof;

k ₀ -the stress concentration factor caused by excavation of the working face;

P ₀ -the resistance of the hydraulic support 6 to the coal bank, MPa;

The third step is to determine the isostatic position of stopping mining

When the working face is stopped and equal pressure, the width of the interval coal pillar between the reserved working face and the withdrawal channel shall be greater than the critical size of the interval coal pillar. However, the size of the spaced coal pillars should not be too large. If it is too large, it may be impossible to wait for pressure. In order to ensure that the final fracture position of the basic roof is shown in Figure 1, the calculation formula for the optimal stop isobaric position is:

S=W ₀ +(n·L) (5)

In formula (5):

S-The best stop isobaric position, that is, the distance between the working face and the withdrawal channel at the stop isobaric position, m;

W ₀ -The best distance between the final fracture position of the basic roof and the non-production side of the withdrawal channel (stop mining line), m;

n- takes the value of 1, 2, 3, 4 and other integers;

L-the basic top break step distance of the working face, which can be obtained through the observation of rock pressure, m;

The following formula (6) and formula (7) are used to jointly constrain the value of n.

w ₂ +w ₃ +n·L≥B (6)

W ₀ +(n·L)=M-〔1/2～1〕·L (7)

In the above formula (6) and formula (7):

M- is the distance between the basic roof fracture position and the stop mining line before the stop isobaric at the working face, m;

W ₂ -is the working face hydraulic support control top distance, m;

W ₃ -is the distance between the hydraulic support in the working face after the penetration and the stack support in the withdrawal channel, m;

B- is the critical size of coal pillars between the working face and the withdrawal channel, m;

Take the minimum value of n that satisfies formula (6) and formula (7); then substitute it into formula (5) to calculate the best stop isobaric position;

Using the above method of stopping mining at a suitable position and equal pressure can achieve the purpose of reducing the mine pressure of the withdrawal channel at the end of the mining face, and ensure the safe use of the withdrawal channel.

The present invention will be further explained below in conjunction with specific application examples.

Taking a certain mine as an example, the average buried depth of 3# coal seam 3 at the level of -180m is 200m, the average coal thickness is 3.6m, and the structure of coal seam 3 is relatively simple. The 330 mining area is the first mining area at the level of -180m. The fully mechanized coal mining method is adopted, and the full height is mined at one time. The ZY7500/21/45 hydraulic support 6 supports the roof. The roof 2 directly above the coal seam 3 is sandy mudstone with a thickness of 6m, and the basic roof 1 is siltstone with a thickness of 12m.

The 3302 working face is 200m long and the strike length is 1200m. The stop position of the working face is to excavate the withdrawal channel 7 in advance, the width of the withdrawal channel 7 is 4.0m, the height is 3.6m, and the tunnel is along the roof of the coal seam 3. The ZZ12000/20/40 type stack support is installed in the withdrawal channel 7 in advance 10. Through the observation of rock pressure, the periodic pressure step L of the working face is 16m.

The first step is to determine the best distance between the final fracture position of the basic top 1 and the non-production side of the retracement channel (stop mining line 9)

_{The optimal distance W 0} between the final fracture position of the basic top 1 and the non-production side of the withdrawal channel 7 (stop mining line 9) satisfies the following formula (1):

W ₀ ＝w ₁ +w ₂ +w ₃ (1)

In formula (1):

W ₀ -The best distance between the final fracture position of the basic top 1 and the non-production side of the withdrawal channel (stop mining line 9), m;

W ₁ -Width of retracement channel 7, which is 4.0m;

W ₂ -The top control distance of the hydraulic support 6 in the working face, which is 4.0m;

W ₃ -The distance between the hydraulic support 6 of the working face after the penetration and the inner stack support of the withdrawal channel 7 is 1.0m;

_{It is determined by the above formula that the optimal distance W 0} between the final fracture position of the basic top 1 and the non-production slab (stop mining line 9) of the withdrawal channel 7 is 9m.

The second step is to calculate the critical size of the coal pillar 8 between the working face and the withdrawal channel

The calculation formula of the _{width X 1} of the plastic zone of the coal body on the production side of the withdrawal channel 7 is:

In formula (3):

m-The height of retracement channel 7, 3.6m;

A-Coefficient of lateral pressure, which takes a value of 0.36;

-The internal friction angle of coal seam 3, which takes a value of 20°;

C ₀ -the cohesive force of coal seam 3, with a value of 1.2 MPa;

k ₁ -the stress concentration factor caused by the excavation of the roadway, with a value of 1.3;

γ-The bulk density of the overlying rock mass, which is 25kN/m ³ ;

H- the thickness of the overlying rock mass, with a value of 200m;

Through the above calculation, it can be obtained: X ₁ =1.939m.

The formula for calculating the _{width X 0} of the plastic zone of the front coal body caused by the mining face is:

In formula (4):

d- the coal mining height of the working face, the value is 3.6m;

ε-triaxial stress coefficient, its expression is as follows:

f-Coefficient of friction between coal seam 3 and the roof, with a value of 0.15;

k ₀ -the stress concentration factor caused by excavation of the working face, taking a value of 2.5;

γ-The bulk density of the overlying rock mass, which is 25kN/m ³ ;

H- the thickness of the overlying rock mass, with a value of 200m;

C ₀ -the cohesive force of coal seam 3, with a value of 1.2 MPa;

-The internal friction angle of coal seam 3, which takes a value of 20°;

P ₀ -the resistance of the hydraulic support 6 to the coal bank, with a value of 0.1 MPa;

Through the above calculation, it can be obtained: X ₀ =4.849m;

The calculation method of the critical size B of the coal pillar 8 between the working face and the withdrawal channel 7 is as follows:

B=X ₀ +X ₁ +2m (2)

among them:

X ₀ -The width of the plastic zone in the front coal body caused by mining at the working face, which is 4.849m according to the aforementioned calculation;

X ₁ -The width of the plastic zone of the coal body on the production side of the withdrawal channel 7, which is 1.939m according to the aforementioned calculation;

m-The height of retracement channel 7, which is 3.6m;

Through the above calculation, it can be obtained: B=13.988m.

The third step is to calculate the isostatic position of stop mining

The formula for calculating the optimal stop-production isostatic position is:

S=W ₀ +(n·L) (5)

In formula (5):

S-The best stop isobaric position;

W ₀ -The best distance between the final fracture position of the basic top 1 and the non-production side of the retracement channel 7 (stop mining line 9), the value is 9.0m;

n- takes the value of 1, 2, 3, 4 and other integers;

L-the basic top cycle of the working face is used to compress the fracture step distance, which can be obtained through the observation of rock pressure, and the value is 16m.

It can be calculated by formula (5): S=25m, 41m, 57m, etc.

The following equations (6) and (7) are used to constrain the value of n.

w ₂ +w ₃ +n·L≥B (6)

W ₀ +(n·L)=M-〔1/2～1〕·L (7)

In the formula: M- is the distance between the fracture position of the basic roof 1 and the stop line 9 before the working face is stopped and isobaric. Through on-site observation, there is a sign of roof pressure when the working face is pushed to 34m from the stop line.

W ₀ -The best distance between the final breaking position of the basic top 1 and the non-production side (stop mining line 9) of the retracement channel 7, which is 9.0m;

W ₂ -is the roof control distance of the hydraulic support 6 in the working face, which is 4.0m;

W ₃ -is the distance between the hydraulic support 6 in the working face after the penetration and the inner stack support of the withdrawal channel 7, and the value is 1.0m;

B- is the critical size of the coal pillar 8 between the working face and the withdrawal channel 7, m;

Substituting the value of M into equation (7), it can be found that when n takes the value 1, equations (6) and (7) are satisfied.

Therefore, through formula (5), the best stop isometric pressure position is when the working face is pushed to the stop line S=25m.

When the working face was 25m away from the stop line, the mining stopped equal pressure. 16 hours after the working face stopped mining, there were signs of roof pressure. After that, the working face continued to push to the stop line. During the period, the confining pressure deformation of the withdrawal channel 9 was relatively large. Small, can ensure the normal withdrawal of the working face equipment.

Claims

A method for reducing the roof pressure of the withdrawal channel at the end of the coal mining face, which is characterized in that it comprises the following steps:

The first step is to determine the best distance between the final fracture position of the basic top of the coal mining face and the non-production side of the withdrawal channel

The optimal distance between the final fracture position of the basic roof of the coal mining face and the non-production side of the withdrawal channel is calculated by formula (1):

W 0 ＝w 1 +w 2 +w 3 (1)

In formula (1): W 0 is the best distance between the final fracture position of the basic roof and the non-production side of the withdrawal channel, m; W 1 is the width of the withdrawal channel, m; W 2 is the working face hydraulic support control roof distance, m ; W 3 is the distance between the hydraulic support in the working face after the penetration and the stack support in the withdrawal channel, m;

The second step is to calculate the critical dimension B of the coal pillar between the working face and the withdrawal channel

The critical size of the spaced coal pillar between the working face and the withdrawal channel is calculated by formula (2):

B=X 0 +X 1 +2m (2)

In formula (2): B is the critical size of the interval coal pillar, m; X 0 is the width of the plastic zone of the coal body in front of the working face, m; X 1 is the width of the plastic zone of the coal body on the side of the production side of the withdrawal channel, m; m is the height of the retracement channel, m;

Among them, the width X 1 of the plastic zone of the coal body on the side of the production side of the withdrawal channel is calculated by formula (3):

In formula (3): m is the height of the retracement channel, m; A is the lateral pressure coefficient;

Is the internal friction angle of the coal seam, °; C 0 is the coal seam cohesion, MPa; k 1 is the stress concentration factor caused by roadway excavation; γ is the bulk density of the overlying rock mass, KN/m 3 ; H is the thickness of the overlying rock mass, m;

The width X 0 of the plastic zone in the front coal body caused by the mining face is calculated by formula (4):

In formula (4): d is the coal mining height of the working face, m; f is the friction coefficient between the coal seam and the roof, k 0 is the stress concentration factor caused by the excavation of the working face, and P 0 is the resistance of the hydraulic support to the coal bank, MPa ; Ε is the triaxial stress coefficient, and its expression is as follows:

The third step is to determine the isostatic position of stopping mining

According to formula (5) to calculate the best stop isobaric position:

S=W 0 +(n·L) (5)

In the formula (5): S is the best stop and equal pressure position; W 0 is the best distance between the final fracture position of the coal mining face and the non-production side of the withdrawal channel, m; n is an integer, taking the value 1. 2, 3, 4...; L is the basic top breaking step of the working face, m; formula (6) and formula (7) are used to restrict the value of n:

w 2 +w 3 +n·L≥B (6)

W 0 +(n·L)=M-〔1/2～1〕·L (7)

In formula (7): M is the distance between the basic roof fracture position and the stop line before the stop isobaric at the working face, m;

Take the minimum value of n that satisfies the above formula (6) and formula (7), and then substitute it into formula (5) to calculate the best stop isobaric position;

The fourth step is based on the optimal stop isostatic position determined in the third step. When the coal mining face reaches the stop isostatic position, the stop isostatic pressure is implemented, and the roof will appear after stopping mining for a period of time. If there is a sign of pressure, then continue to push the working face to the stop line to complete the coal mining operation.