阅读说明：本技术 一种减少采煤工作面回采末期回撤通道顶板压力的方法 (Method for reducing top plate pressure of withdrawal channel at last stage of coal face extraction ) 是由 宁建国 邱鹏奇 商和福 李学慧 王俊 胡善超 于 2019-11-15 设计创作，主要内容包括：本发明公开了一种减少采煤工作面回采末期回撤通道顶板压力的方法,包括以下步骤：第一步,确定采煤工作面基本顶最终断裂位置距回撤通道非生产帮的最佳距离；第二步,计算工作面与回撤通道之间间隔煤柱临界尺寸；第三步,确定停采等压位置；第四步,以第三步确定出的最佳停采等压位置为依据,当采煤工作面到达停采等压位置时,实施停采等压,工作面停采一段时间后出现顶板来压迹象,此后再将工作面继续推采至停采线,完成采煤作业。本发明可解决采煤工作面回采末期回撤通道顶板压力大的问题,通过对工作面回采末期合适位置处实施停采等压措施,改变基本顶周期来压位置,进而达到减少采煤工作面回采末期回撤通道顶板压力,保证采煤工作面顺利回撤。(The invention discloses a method for reducing the roof pressure of a withdrawal channel at the last stage of coal face extraction, which comprises the following steps: the method comprises the following steps that firstly, the optimal distance between the final fracture position of a basic roof of a coal face and a non-production side of a withdrawal passage is determined; secondly, calculating the critical dimension of the coal pillar between the working surface and the withdrawal passage; thirdly, determining the mining stop isobaric position; and fourthly, based on the optimal stop-mining isobaric position determined in the third step, when the coal face reaches the stop-mining isobaric position, stopping mining isobaric, indicating that the top plate pressure comes after the face stops mining for a period of time, and then continuously pushing the face to a stop-mining line to complete coal mining operation. The invention can solve the problem of high pressure of the top plate of the withdrawal channel at the last stage of the coal face recovery, and changes the basic top period pressure position by implementing a stopping constant pressure measure on the proper position at the last stage of the coal face recovery, thereby reducing the pressure of the top plate of the withdrawal channel at the last stage of the coal face recovery and ensuring the smooth withdrawal of the coal face.)

1. A method for reducing the roof pressure of a withdrawal channel at the last mining stage of a coal face is characterized by comprising the following steps:

the first step is to determine the optimal distance between the final fracture position of the basic roof of the coal face and the non-production side of the withdrawal passage

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

W₀＝w₁+w₂+w₃(1)

in formula (1): w₀The optimal distance, m, between the final fracture position of the basic roof and the non-production side of the withdrawal passage; w₁M, the width of the withdrawal passage; w₂Controlling the jacking distance m for the hydraulic support of the working face; w₃The distance m is the distance between the hydraulic support penetrating the rear working face and the stack type support in the retraction channel;

secondly, calculating the critical dimension B of the coal pillar between the working surface and the withdrawal passage

The critical dimension of the spacing coal pillar reserved between the working surface and the withdrawal passage is calculated by adopting a formula (2) to obtain:

B＝X₀+X₁+2m (2)

in formula (2): b is the critical dimension of the coal pillar at intervals, m; x₀The width m of a front coal body plastic zone caused by working face recovery; x₁The width m of the plastic zone of the coal body on the upper side is produced for the withdrawal passage; m is the height of the withdrawal passage;

wherein, the width X of the plastic zone of the coal body on the production side of the withdrawing channel₁The following formula (3) is adopted to calculate:

in formula (3): m is the height of the withdrawal passage; a is a side pressure coefficient;

front coal plasticity zone width X caused by working face recovery₀The following formula (4) is adopted to calculate:

in formula (4): d is the coal mining height of the working face, m; epsilon is the coefficient of the stress of the three axes,

thirdly, determining the extraction stop equal pressure position

Calculating the optimal stop production isobaric position according to the formula (5):

S＝W₀+(n·L) (5)

in formula (5): s is the best stoping isobaric position; w₀The optimal distance m between the final fracture position of the basic roof of the coal face and the non-production side of the withdrawal passage; n is an integer and takes the values of 1, 2, 3 and 4 … …; l is the basic top fracture step distance of the working surface, m;

and (3) constraining the value of n by adopting a formula (6) and a formula (7):

W₂+W₃+n·L≥B (6)

in formula (7): m is the distance between the basic top fracture position and the mining stop line before the working face is subjected to mining stop isobaric pressure, and M is the distance between the basic top fracture position and the mining stop line;

taking the minimum value of n meeting the formula (6) and the formula (7), and substituting the minimum value into the formula (5) to calculate the optimal stop-mining isobaric position;

and fourthly, based on the optimal stop-mining isobaric position determined in the third step, when the coal face reaches the stop-mining isobaric position, stopping mining isobaric, indicating that the top plate pressure comes after the face stops mining for a period of time, and then continuously pushing the face to a stop-mining line to complete coal mining operation.

Technical Field

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

Background

When underground coal mining is used for arranging a working face production system, a withdrawal passage is usually tunneled in advance, and a roadway is supported by an anchor net cable. When the working face is far away from the withdrawal passage, the withdrawal passage is used as a connection roadway. When the distance between the working face and the withdrawing channel is 200-400 m, a control top plate of the stack type support is arranged in the roadway in advance. When the working face is pushed to the position of the withdrawal channel, the working face withdrawal is stopped, the withdrawal channel is used as a withdrawal space of the working face mechanical equipment, and the time for tunneling the withdrawal space at the last stage of the working face withdrawal is saved, so that the final-stage withdrawal speed of the coal face is accelerated.

However, the top plate comes to press at the last stage of the mining of many coal faces, the top of the basic top is broken at the upper part or the front part of the withdrawal passage, the basic top slips and is unstable or rotates and sinks greatly, the hydraulic support at the lower part of the basic top bears huge pressure, and the expansion amount of the support is reduced sharply or even is dead. And the basic roof transmits the borne huge pressure to surrounding rocks of the withdrawal passage, and the crushing of a roadway top plate, the rib caving of a coal wall and the bottom bulging occur. The height of the hydraulic support is insufficient, the retraction channel is seriously contracted and deformed to cause insufficient retraction space, and difficulty is brought to the retraction of equipment on a working face. In order to ensure the normal use of the withdrawal passage, a great deal of manpower and material resources are needed to repair the tunnel.

At present, in order to solve the problem of roof pressure coming at the last stage of mining, some methods for roof cutting, pressure relief and roadway protection of a mining face terminal mining withdrawal channel are adopted, for example, a deep hole pre-splitting drill hole is drilled in the middle of a roof in the withdrawal channel, then explosive is filled for blasting pressure relief, or a fracturing drill hole is drilled in the roof of the withdrawal channel, and then hydraulic fracturing pressure relief treatment is carried out. However, the method has the problems of complex operation, labor consumption, high cost required for realization and the like.

Disclosure of Invention

Based on the technical problem, the invention provides a method for reducing the roof pressure of a withdrawal channel at the last stage of coal face recovery.

The technical solution adopted by the invention is as follows:

a method for reducing the roof pressure of a withdrawal channel at the last mining stage of a coal face comprises the following steps:

the first step is to determine the optimal distance between the final fracture position of the basic roof of the coal face and the non-production side of the withdrawal passage

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

W₀＝w₁+w₂+w₃(1)

in formula (1): w₀The optimal distance, m, between the final fracture position of the basic roof and the non-production side of the withdrawal passage; w₁M, the width of the withdrawal passage; w₂Controlling the jacking distance m for the hydraulic support of the working face; w₃The distance m is the distance between the hydraulic support penetrating the rear working face and the stack type support in the retraction channel;

secondly, calculating the critical dimension B of the coal pillar between the working surface and the withdrawal passage

The critical dimension of the spacing coal pillar reserved between the working surface and the withdrawal passage is calculated by adopting a formula (2) to obtain:

B＝X₀+X₁+2m (2)

in formula (2): b is the critical dimension of the coal pillar at intervals, m; x₀The width m of a front coal body plastic zone caused by working face recovery; x₁The width m of the plastic zone of the coal body on the upper side is produced for the withdrawal passage; m is the height of the withdrawal passage;

wherein, the width X of the plastic zone of the coal body on the production side of the withdrawing channel₁The following formula (3) is adopted to calculate:

in formula (3): m is the height of the withdrawal passage; a is a side pressure coefficient;

the angle of friction in the coal bed is degree; c₀Is the coal bed cohesion, MPa; k is a radical of₁Stress concentration coefficient caused by roadway excavation; gamma is the volume weight of the overburden rock mass, KN/m 3; h is the thickness of the overlying rock mass m;

front coal plasticity zone width X caused by working face recovery₀The following formula (4) is adopted to calculate:

in formula (4): d is the coal mining height of the working face, m; epsilon is the coefficient of the stress of the three axes,

f is the friction coefficient between the coal bed and the top plate, k₀Stress concentration factor, P, for excavation of working face₀The resistance of the hydraulic support to the coal side is MPa;

thirdly, determining the extraction stop equal pressure position

Calculating the optimal stop production isobaric position according to the formula (5):

S＝W₀+(n·L) (5)

in formula (5): s is the best stoping isobaric position; w₀The optimal distance m between the final fracture position of the basic roof of the coal face and the non-production side of the withdrawal passage; n is an integer and takes the values of 1, 2, 3 and 4 … …; l is the basic top fracture step distance of the working surface, m;

and (3) constraining the value of n by adopting a formula (6) and a formula (7):

W₂+W₃+n·L≥B (6)

in formula (7): m is the distance between the basic top fracture position and the mining stop line before the working face is subjected to mining stop isobaric pressure, and M is the distance between the basic top fracture position and the mining stop line;

taking the minimum value of n meeting the formula (6) and the formula (7), and substituting the minimum value into the formula (5) to calculate the optimal stop-mining isobaric position;

and fourthly, based on the optimal stop-mining isobaric position determined in the third step, when the coal face reaches the stop-mining isobaric position, stopping mining isobaric, indicating that the top plate pressure comes after the face stops mining for a period of time, and then continuously pushing the face to a stop-mining line to complete coal mining operation.

The beneficial technical effects of the invention are as follows:

the stoping isobaric method is implemented at the last stage of the working face stoping, the fracture position of the basic roof can be changed, the basic roof is fractured at a reasonable position, the aim of reducing the mine pressure of the withdrawal channel at the last stage of the working face stoping is finally achieved, and the safe use of the withdrawal channel is ensured. Compared with a mode of roof cutting and pressure relief of a withdrawal channel, the roof cutting and pressure relief device has the advantages of simplicity in operation, low implementation cost, higher safety and the like.

Drawings

The invention is further described with reference to the following figures and detailed description:

FIG. 1 is a diagram of a substantially top-most fracture location when the present invention is directed to face stoping;

FIG. 2 is a diagram of the basic top fracture location before and after face stop recovery isobaric in accordance with the present invention; wherein (a) is a stratum movement diagram when the working face stops producing at equal pressure, and (b) is a stratum movement diagram when the working face stops producing after stopping producing at equal pressure.

In the figure: 1. the method comprises the following steps of (1) basic roof, (2) direct roof, (3) coal bed, (4) broken basic roof with the length of L, (5) broken basic roof with the length of (0.5-1) L, (6) hydraulic support, (7) withdrawal channel, (8) coal pillar spacing between the withdrawal channel and the working face, (9) working face stoping line, and (10) stack type support.

Detailed Description

Aiming at the phenomenon that the working face is difficult to terminate due to the fact that roof pressure possibly occurs at the last stage of mining of the coal face, the method for stopping mining and equalizing the pressure when the working face is pushed to a proper position is adopted, as shown in figure 2, the basic roof is broken forwards, the basic roof period pressure coming position is further changed, when the working face stops mining, the basic roof is broken at the best position, as shown in figure 1, and the phenomenon of mine pressure appearing in a withdrawal channel is minimized.

This will be described in more detail below with reference to the accompanying drawings.

A method for reducing the roof pressure of a withdrawal channel at the last mining stage of a coal face comprises the following steps:

the first step is to determine the optimal distance between the final fracture position of the basic roof of the coal face and the non-production side (stoping line) of the withdrawal passage

In order to ensure that the mine pressure appearance phenomenon of the withdrawal channel is minimum and the convergence deformation of the roadway is minimum, the optimal distance between the final fracture position of the basic roof 1 and the non-production side (the stop mining line 9) of the withdrawal channel 7 when the working face stops mining needs to be determined. This roof fracture location is most beneficial to the stability of the retraction channel.

As shown in fig. 1, the optimal distance from the final breaking position of the basic roof to the non-production side (stoping line 9) of the withdrawal passage satisfies the formula (1):

W₀＝w₁+w₂+w₃(1)

in formula (1):

W₀the optimal distance, m, of the final breaking position of the basic crown 1 from the non-production side (stoping line 9) of the withdrawal channel 7;

W₁-withdrawal channel width, m;

W₂-working face hydraulic support control jacking distance, m;

W₃and the distance m between the hydraulic support penetrating through the rear working face and the stack type support in the retraction channel.

Secondly, calculating the critical dimension of the coal pillar 8 between the working surface and the withdrawal passage 7

Stopping production and equalizing pressure are carried out at the last stage of working face recovery, and a spacing coal pillar with a certain size is reserved between the stopping production and equalizing pressure position and the withdrawal passage (as shown in figure 2 (a)). The size of the coal pillars with the reserved intervals cannot be too small, otherwise the coal pillars are damaged, and the basic roof is not broken at a reasonable position. The reserved interval coal pillar critical dimension is calculated by adopting an equation (2):

B＝X₀+X₁+2m (2)

in formula (2):

b, spacing the critical dimension of the coal pillar, m;

X₀-the width of the coal plastic zone in front, m, caused by face extraction;

X₁-the width, m, of the coal plastic zone on the production side of the withdrawal channel;

m-the height of the withdrawal passage, m.

Coal body plastic region width X of withdrawal channel production side₁Calculating by using formula (3):

in formula (3):

m-the height of the withdrawal passage, m;

a-side pressure coefficient;

-internal friction angle, degree, of the coal seam 3;

C₀-cohesion of coal seam 3, MPa;

k₁-stress concentration factor due to roadway excavation;

volume weight of gamma-overburden rock mass, KN/m³；

H, the thickness of the overlying rock mass m;

front coal plasticity zone width X caused by working face recovery₀Calculating by using formula (4):

in formula (4):

d-working face coal mining height, m;

epsilon-the coefficient of stress in the three axes,

f, friction coefficient of the coal body and the top plate;

k₀-the stress concentration factor caused by the excavation of the working face;

P₀the resistance of the hydraulic support 6 to the coal slope, MPa;

thirdly, determining the extraction stop equal pressure position

When the working face implements stoping and isobaric pressure, the width of the coal pillar between the reserved working face and the withdrawal channel is larger than the critical dimension of the coal pillar. However, the size of the reserved coal pillars cannot be too large, and if the size of the reserved coal pillars is too large, the situation of waiting for pressure can occur. To ensure that the basic crest ultimate failure location is as shown in FIG. 1, the optimal stop-production isopipe location calculation formula is:

S＝W₀+(n·L) (5)

in formula (5):

s-the optimal stop-production equal-pressure position, namely the interval between the working surface of the stop-production equal-pressure position and the withdrawal channel, m;

W₀-the optimal distance, m, of the final breaking position of the basic crown from the non-productive highwall (stope line) of the withdrawal passage;

n-takes the integers of 1, 2, 3, 4, etc.;

l is the basic top fracture step distance of the working face, which can be obtained by mine pressure observation, m;

and jointly constraining the value of n by adopting the following formula (6) and formula (7).

W₂+W₃+n·L≥B (6)

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

m is the distance between the basic top fracture position and the mining stop line before the working face is subjected to mining stop and isobaric pressure, and M is the distance between the basic top fracture position and the mining stop line;

W₀-the optimal distance, m, of the final breaking position of the basic crown from the non-productive highwall (stope line) of the withdrawal passage;

W₂the control top distance m is the working face hydraulic support;

W₃the distance m between the hydraulic support penetrating the rear working face and the stack type support in the retraction channel;

b-is the critical dimension m of the coal pillar between the working surface and the withdrawal passage;

taking the minimum value of n meeting the formula (6) and the formula (7); then substituting the position into a formula (5) to calculate the optimal stop production isobaric position;

and fourthly, based on the optimal stop-mining isobaric position determined in the third step, when the coal face reaches the stop-mining isobaric position, stopping mining isobaric, indicating that the top plate pressure comes after the face stops mining for a period of time, and then continuously pushing the face to a stop-mining line to complete coal mining operation.

By adopting the method for stopping production at the proper position and keeping the pressure constant, the aim of reducing the mine pressure of the withdrawal channel at the last stage of the working face can be achieved, and the safe use of the withdrawal channel is ensured.

The invention is further illustrated below with reference to specific application examples.

Taking a certain mine as an example, the average burial depth of the horizontal 3# coal seam 3 of 180m in the coal mine is 200m, the average coal thickness is 3.6m, and the structure of the coal seam 3 is simpler. The 330 mining area is a first mining area at the level of-180 m, a fully mechanized coal mining method is adopted, the full height is mined at one time, and a ZY7500/21/45 type hydraulic support 6 supports a top plate. The upper part of the coal seam 3 is directly topped by sandy mudstone with the thickness of 6m, and the basic top 1 is siltstone with the thickness of 12 m.

3302 the working surface is 200m long and runs 1200m long. And (3) digging a withdrawal channel 7 in advance at the mining stop position of the working face, wherein the width of the withdrawal channel 7 is 4.0m, the height of the withdrawal channel 7 is 3.6m, the coal seam is tunneled along the top plate of the coal seam 3, and a ZZ12000/20/40 type stack type support 10 is installed in the withdrawal channel 7 in advance. The periodic pressure step L of the working face is 16m through ore pressure observation.

First, the optimal distance between the final fracture position of the basic roof 1 and the non-production side (stoping line 9) of the withdrawal passage is determined

Optimum distance W between final fracture position of basic roof 1 and non-production side (stop production line 9) of withdrawal passage 7₀Satisfies the following formula (1):

W₀＝w₁+w₂+w₃(1)

in formula (1):

W₀the optimal distance, m, of the final breaking position of the basic crown 1 from the non-productive side (stoping line 9) of the withdrawal passage;

W₁-the width of the withdrawal passage 7, taken to be 4.0 m;

W₂the control jacking distance of the hydraulic support 6 on the working face is 4.0 m;

W₃the distance between the hydraulic support 6 on the run-through rear working face and the stack type support in the retraction channel 7 is 1.0 m;

the optimal distance W between the final fracture position of the basic roof 1 and the non-production side (stop production line 9) of the withdrawal passage 7 is determined by the formula₀Is 9 m.

Second, calculate the critical dimension of the coal pillar 8 between the working face and the retracting channel

Production side coal body plastic area width X of withdrawal channel 7₁The calculation formula is as follows:

in formula (3):

m-height of withdrawal passage 7, 3.6 m;

a, taking the lateral pressure coefficient to be 0.36;

-the internal friction angle of the coal seam 3, taken as 20 °;

C₀-the cohesion of the coal seam 3, taking 1.2 MPa;

k₁-stress concentration factor due to roadway excavation, taking 1.3;

the volume weight of the gamma-overlying rock mass is 25kN/m³；

H, the thickness of the overlying rock mass is 200 m;

from the above calculations it can be derived: x₁＝1.939m。

Front coal plasticity zone width X caused by working face recovery₀The calculation formula is as follows:

in formula (4):

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

epsilon-the coefficient of stress in the three axes,

f, the friction coefficient of the coal seam 3 and the top plate is 0.15;

k₀-the stress concentration coefficient caused by the excavation of the working face, taking the value of 2.5;

the volume weight of the gamma-overlying rock mass is 25kN/m³；

H, the thickness of the overlying rock mass is 200 m;

C₀-the cohesion of the coal seam 3, taking 1.2 MPa;

-the internal friction angle of the coal seam 3, taken as 20 °;

P₀the resistance of the hydraulic support 6 to the coal upper is 0.1 MPa;

from the above calculations it can be derived: x₀＝4.849m；

The critical dimension B of the coal pillar 8 between the working face and the withdrawal passage 7 is calculated as follows (2):

B＝X₀+X₁+2m (2)

wherein:

X₀the width of a front coal body plastic zone caused by recovery of a working face is calculated to be 4.849 m;

X₁the width of the plastic zone of the coal body on the production side of the withdrawal channel 7 is calculated to be 1.939 m;

m is the height of the withdrawal passage 7, and the value is 3.6 m;

from the above calculations it can be derived: and B is 13.988 m.

Thirdly, calculating the extraction stop equal pressure position

The optimal stop production isobaric position calculation formula is as follows:

S＝W₀+(n·L) (5)

in formula (5):

s-optimal stop-production equal-pressure position;

W₀the optimal distance between the final fracture position of the basic roof 1 and the non-production side (stop production line 9) of the withdrawal passage 7 is 9.0 m;

n-takes the integers of 1, 2, 3, 4, etc.;

l is the fracture step distance of the basic top period of the working face, and can be obtained by observing the mine pressure, and the value is 16 m.

The following can be calculated by equation (5): s25 m, 41m, 57m, etc.

The values of n are constrained by the following formulas (6) and (7).

W₂+W₃+n·L≥B (6)

In the formula: and M is the distance between the fracture position of the basic jack 1 and the stoping line 9 before stoping and isobaric of the working face, and the sign of the pressure coming of the jack panel appears when the working face is pushed to be 34M away from the stoping line through field observation.

W₀The optimal distance between the final fracture position of the basic roof 1 and the non-production side (stoping line 9) of the withdrawal passage 7 is 9.0 m;

W₂the control top distance of the hydraulic support 6 on the working face is 4.0 m;

W₃the distance between the hydraulic support 6 on the run-through working face and the stack type support in the retraction channel 7 is 1.0 m;

b-is the critical dimension m of the coal pillar 8 between the working face and the withdrawal passage 7;

when the value of M is substituted for the formula (7), it can be found that when n takes a value of 1, the formulas (6) and (7) are satisfied.

Therefore, the optimal stop-production equal pressure position is obtained by the formula (5) when the working face is pushed to a position which is 25m away from the stop-production line S.

The working face implements stop production equal pressure when the working face is 25m away from the stop production line, a top plate pressure coming sign appears after the working face stops production for 16 hours, then the working face continues to push production to the stop production line, the confining pressure deformation of the withdrawing channel 9 is small in the period, and normal withdrawing of working face equipment can be guaranteed.