A method for two-step pre-excavation of support and support withdrawal of a withdrawal channel

Abstract

The application discloses a kind of back channel step two times pre-excavation support and support back method, comprising the following steps: (A) determining the range of stress reduction zone in advance mining;(B) support in advance mining influence zone;(C) excavate the back channel of first half, excavate transfer chamber and corner;Excavation is carried out simultaneously with the support of first half back space and the equipment of first half back;(D) excavate the back channel of second half, excavate transfer chamber and corner;Excavation is carried out simultaneously with the support of second half back space and the equipment of second half back.The present application is in advance according to support stress curve in stress reduction zone before stopping mining line, and the back channel is excavated in two steps on site, and the back channel is excavated and the support is shielded to realize the synergistic effect.

Description

Technical Field

[0001] This invention relates to the field of coal mining, and in particular to a method for pre-excavating and supporting a retreat channel in two stages and for the retreat of the support. Background Technology

[0002] After the longwall mining face is completed, large equipment such as hydraulic supports needs to be moved to the next working face; this process is commonly known as "working face relocation." Currently, there are generally two methods for equipment relocation: excavating relocation channels in place and pre-excavating relocation channels. The former has an unsafe working space, is time-consuming and labor-intensive, and the average relocation time is 1 to 2 months. The pre-excavated relocation channel technology involves pre-excavating a relocation channel parallel to the coal mining face near the final mining line. Once the coal mining face and the pre-excavated relocation channel are connected, this pre-excavated channel is used as the channel for removing equipment. Pre-excavated relocation channels offer a safe working space, significantly reduce the difficulty of equipment relocation, and can be carried out simultaneously with coal mining on the working face, saving a lot of time in relocating equipment. However, since the pre-excavated relocation channel is completed before the working face is mined, the dynamic support pressure from the advanced working face mining can easily lead to accidents such as crushing the coal pillars in the final mining section and killing the hydraulic supports. Therefore, the support effect of the pre-excavated relocation channel directly affects the handover of the working face and mine production. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for excavating and withdrawing a tunnel in two steps on-site in the stress reduction zone before the mining line is stopped, based on the stress curve of the advanced support, so as to achieve the coordinated effect of tunnel excavation and support protection.

[0004] The present invention provides a method for pre-excavating and retracting the support in two stages for the withdrawal channel, comprising the following steps:

[0005] (A) Determine the range of the stress reduction zone caused by advance mining;

[0006] (B) Support for the area affected by advanced mining;

[0007] (C) Excavate the first half of the retreat passage, excavate the transfer chamber and chamfer the corners; while excavating, support the first half of the retreat space and retreat the first half of the equipment;

[0008] (D) Excavate the retreat passage in the second half, excavate the transfer chamber and chamfer the corners; while excavating, support the retreat space in the second half and retreat the equipment in the second half.

[0009] The method for pre-excavating and supporting the retreat channel in two steps according to the present invention includes the following steps in step (A): combining the on-site mining process and numerical simulation calculation to analyze the characteristics of the impact of advance mining on the fully mechanized longwall face, calculate the stress concentration coefficient and mining failure depth of the impact of advance mining on the fully mechanized longwall face, and then determine the range of the mining stress reduction zone.

[0010] The method for pre-excavating and retracting the support in two steps for the withdrawal channel as described in this invention, wherein the calculation process in step (A) is as follows:

[0011] ① Determine the length of the basic top cantilever structure and the periodic pressure step distance based on the mining pressure manifestation law of the working face. L b Based on the principle of force equivalence, the equilibrium equation for the transmission of mining power in front of the coal face in a fully mechanized longwall mining face is established through integration:

[0012]

[0013] In the formula: L b The period is used to adjust the step size, m; e is the natural constant, which is the base of the natural logarithm function, and its value is 2.718; P z The stress is the original rock stress, in MPa. ; m The thickness of the lateral edge coal and rock mass is in meters (m). f The frictional resistance coefficient for lateral displacement of the coal and rock mass boundary; Uniaxial compressive strength, MPa ; C Cohesion, MPa; The internal friction angle is °; ; P j The horizontal resistance of the coal face is measured in MPa. y p The depth of coal face damage caused by advanced mining, in meters (m).

[0014] ② Perform univariate numerical calculations on step ① to obtain the depth of advance mining damage to the coal face in the fully mechanized longwall face. y p ;

[0015] ③ Calculate the stress concentration factor caused by mining from step ②: ;

[0016] ④ Calculate the vertical stress distribution of the coal face under advance mining from step ②:

[0017]

[0018] In the formula: , The vertical stress in MPa represents the mining-induced stress in the advanced coal and rock failure zone and elastic zone in front of the coal face.

[0019] ⑤ After calculating the advanced support stress curve, based on the calculated stress reduction zone distance... y p Determine the width y of the excavation and retreat passage.c :

[0020] make time The calculated y is y c .

[0021] The method for pre-excavation and support of the retreat channel in two steps and the method for support retreat described in this invention, wherein the support of the advance mining-affected area in step (B) is as follows:

[0022] End supports are provided at both ends of the working face. The support method is passive support of two single columns + π-shaped beams. The distance between the single columns on both sides and the adjacent coal wall does not exceed 200mm, and the end support spacing is 0.6m.

[0023] Strengthen the support in the roadway in the original rock stress zone. The support method is two anchor cables + steel beam active reinforcement support. The distance between the anchor cables on both sides and the adjacent coal wall shall not exceed 200mm. The length of the anchor cables is 1.5m and the reinforcement support spacing is 1.2m.

[0024] The roadway support method for the stress-increased zone is two short anchor cables + one long anchor cable + steel beam active reinforcement support. The long anchor cable is in the middle, and the distance between the short anchor cables at both ends and the adjacent coal face does not exceed 200mm. The length of the short anchor cables is 1.5m. The length of the long anchor cable in the middle is 3m. The roadway support spacing in the stress-increased zone is 0.6m.

[0025] The present invention describes a method for pre-excavating and retracting a retreat channel in two steps, wherein the roof of the retreat channel in steps (C) and (D) is designed to be inclined, forming a π-shaped roadway. The side closer to the hydraulic support is the lower side, with a height of h, where h is the coal seam thickness. The side closer to the coal seam is the higher side, and the height is calculated using the following formula:

[0026] .

[0027] The method for pre-excavation and support of the retreat channel in two steps and the method for support retreat described in this invention, wherein the support method of the retreat space in steps (C) and (D) is a broken line support + single support + π-shaped beam support, and the retreat space includes the retreat channel and the chamber.

[0028] The zigzag support includes a lower zigzag support and an upper zigzag support mounted thereon. A wall shield is provided outside the lower zigzag support. The wall shield is elongated and close to the coal wall. A groove is provided on the wall shield along its length. The lower zigzag support is fixed in the groove. The height of the lower zigzag support is the same as the height of the single support. The π-shaped beam is inclined and has slots on both sides, which are fixed to the single support and the upper zigzag support, respectively. The upper zigzag support is perpendicular to the π-shaped beam.

[0029] The present invention describes a method for pre-excavating and retracting a retreat channel in two steps, wherein the height of the wall shield is 150mm-250mm higher than that of the lower support column, the width is 300mm, the thickness is 12mm, and the material is Q235 ordinary carbon structural steel. The groove runs through the entire wall shield from top to bottom, and the inner diameter is equal to the maximum radius of the lower support column. The support spacing of the retreat space is 0.8m.

[0030] The method for pre-excavating and retracting the support in two steps in the retreat channel described in this invention includes the following steps in step (A): at a position 15-20 m away from the stop line on the working face, a diamond-shaped metal mesh is hung on the top plate of the working face above the position of the first half of the hydraulic support to prevent the top of the working face from collapsing due to breakage.

[0031] The present invention describes a method for pre-excavating and retracting the support in two steps for the withdrawal channel, wherein the hydraulic supports on the working face are numbered sequentially, with the main haulage roadway as the starting point and the auxiliary haulage roadway as the ending point.

[0032] The method for retracting the first half of the equipment in step (C) specifically includes the following steps: retract the scraper conveyor and the coal mining machine, retract all the odd-numbered hydraulic supports on the first half of the working face in forward order, and build timber stacks to support them behind them, then retract all the even-numbered hydraulic supports on the first half of the working face in reverse order, and build timber stacks to support them behind them.

[0033] The method for retracting the second half of the equipment in step (D) specifically includes the following steps: retract all hydraulic supports with even numbers on the second half of the working surface in reverse order, and build timber stacks for support behind them; then retract all hydraulic supports with odd numbers on the second half of the working surface in forward order, and build timber stacks for support behind them.

[0034] The present invention describes a method for pre-excavating and retracting a support in two stages for a retreat channel, wherein the "cornering" refers to applying a radius of [missing information] to the coal face at the auxiliary transport end. y c chamfering

[0035] The difference between the present invention's method of step-by-step two-stage pre-excavation and support withdrawal and the existing technology is that:

[0036] The method for step-by-step pre-excavation and support withdrawal of the pullback channel in this invention has the following advantages:

[0037] 1. Inclined π-shaped roadway: The excavation of the inclined π-shaped roadway is designed based on scientific and reasonable calculations and the actual stress variation characteristics of the roadway and coal seam. The left side represents the coal seam thickness, and the right side represents the height value fitted according to the relationship between the stress concentration coefficient and the coal seam thickness, fully following the scientific laws of the stress curve. Secondly, as can be seen from the relationship of the stress curve, the rock above the coal seam will still form an inclined plastic zone. When the broken coal and rock mass is included in the support structure such as anchor bolts and anchor cables, it is difficult for the structural surface to be in a compressed state, and the overall support effect of the rock mass will be very poor, which will pose a safety hazard. This reinforcement is safer, more efficient and reasonable, and greatly improves safety. Finally, traditional rectangular roadways will have anchor bolt heads left at the top, and the supports need to be lowered too much. However, the design of this invention, the inclined π-shaped roadway excavation, increases safety performance, increases the operating space of the retraction equipment, increases the operating speed, reduces the number of procedures, and improves safety.

[0038] 2. Inclined π-shaped roadway support: First, it increases lateral space, because every inch of space is extremely precious when the pre-stress reduction zone is very small. Second, the near-vertical support of the pillars along the zigzag line to the roof can efficiently increase the support stress. Third, it relies on the strong lateral support provided by the coal wall to form a stable support. Fourth, both lateral and longitudinal space are increased, and the support safety is higher.

[0039] 3. Coordination method for tunneling and retreat during the retreat channel stage: At a position 15-20 m from the stop line on the working face, begin to adjust the hydraulic support position of the front half of the working face roof (1... # -64 # In the first stage, diamond-shaped metal mesh was installed to prevent the top of the working face from collapsing, thus forming a relatively stable roof rock structure. The vast majority of the roof pressure was borne by the stable upper structure, resulting in much less pressure on the tunneling, support, and retreat equipment in the first half of the process, ensuring safety and reliability. In the second stage, the diamond-shaped metal mesh was not used because the upper structure, which had formed over a large area and for too long, would be extremely dangerous should pressure be released. Therefore, in this stage, it was necessary to release the pressure from above. In the second stage, the pressure on the tunneling, support, and retreat equipment was actually only the pressure from the directly broken roof above; other pressures were still borne by the coal wall and goaf. This operation fully followed the distribution characteristics and spatiotemporal variations of the working face pressure, making it scientific, reasonable, safe, and efficient.

[0040] 4. The pre-excavation of the withdrawal channel before the stop-mining line overcomes the problem of traditional pre-excavation withdrawal channels being completed ahead of the working face mining. Under the influence of the dynamic support pressure of the advanced mining face, accidents such as crushing the coal pillars in the final mining section and killing the hydraulic supports are prone to occur. This invention achieves safe, pressure-free, rapid, and low-cost withdrawal of the final mining equipment. The withdrawal channel of this invention is pre-excavated and supported in two stages, and the support withdrawal method can avoid the strong influence of the advanced mining face, while the withdrawal speed is fast and the cost is low, fundamentally solving the drawbacks of traditional support withdrawal.

[0041] The following description, in conjunction with the accompanying drawings, further illustrates the step-by-step pre-excavation and support withdrawal method of the present invention for the withdrawal channel. Attached Figure Description

[0042] Figure 1 This is the vertical stress distribution curve of the coal face under advance mining in the method of the present invention;

[0043] Figure 2 This is a schematic diagram of the end support structure at both ends of the working face in the method of the present invention;

[0044] Figure 3 This is a schematic diagram of the structure for reinforcing the roadway in the original rock stress zone in the method of the present invention;

[0045] Figure 4 This is a schematic diagram of the structure of the roadway support in the stress-increased zone in the method of the present invention;

[0046] Figure 5 This is a schematic diagram of the excavation and support of the first half of the retreat channel in the method of the present invention;

[0047] Figure 6 This is a schematic diagram of the broken-line support structure in the retraction channel of the method of the present invention;

[0048] Figure 7 This is a schematic diagram of the excavation and support of the second half of the retreat channel in the method of the present invention;

[0049] Figure 8 This is the vertical stress distribution curve of the coal face during advance mining in the fully mechanized mining method of the present invention. Detailed Implementation

[0050] Example 1

[0051] A method for pre-excavation and support removal in two stages for a retreat channel includes the following steps:

[0052] (A) Determine the range of stress reduction zone for advance mining: Combine the on-site mining process and numerical simulation calculation to analyze the characteristics of the impact of advance mining on the fully mechanized longwall face, calculate the stress concentration coefficient and mining failure depth of the impact of advance mining on the fully mechanized longwall face, and then determine the range of stress reduction zone for mining.

[0053] The calculation process is as follows:

[0054] ① Determine the length of the basic top cantilever structure and the periodic pressure step distance based on the mining pressure manifestation law of the working face. L b Based on the principle of force equivalence, the equilibrium equation for the transmission of mining power in front of the coal face in a fully mechanized longwall mining face is established through integration:

[0055]

[0056] In the formula: L b The period is used to adjust the step size, m; e is the natural constant, which is the base of the natural logarithm function, and its value is 2.718; P z The stress is the original rock stress, in MPa. ; m The thickness of the lateral edge coal and rock mass is in meters (m). f The frictional resistance coefficient for lateral displacement of the coal and rock mass boundary; Uniaxial compressive strength, MPa ; C Cohesion, MPa; The internal friction angle is °; ; P j The horizontal resistance of the coal face is measured in MPa. y p The depth of coal face damage caused by advanced mining, in meters (m).

[0057] ② Perform univariate numerical calculations on step ① to obtain the depth of advance mining damage to the coal face in the fully mechanized longwall face. y p ;

[0058] ③ Calculate the stress concentration factor caused by mining from step ②: ;

[0059] ④ Calculate the vertical stress distribution of the coal face under advance mining from step ②:

[0060]

[0061] In the formula: , The vertical stress in MPa represents the mining-induced stress in the advanced coal and rock failure zone and elastic zone in front of the coal face.

[0062] ⑤ After calculating the advanced support stress curve, based on the calculated stress reduction zone distance... y p Determine the width y of the excavation and retreat passage. c :

[0063] make time The calculated y is y c .

[0064] At a distance of 15-20 m from the stop line, diamond-shaped metal mesh is hung on the top plate of the working face above the location of the first half hydraulic support 1 to prevent the top of the working face from collapsing due to breakage.

[0065] (B) Support for the area affected by advanced mining:

[0066] like Figure 2 As shown, end supports 3 are provided at both ends of the working face. The support method is two single columns 301 + π-shaped beam passive support 302. The distance between the single columns 301 on both sides and the adjacent coal wall does not exceed 200mm. The spacing of the end supports 3 is 0.6m.

[0067] like Figure 3 As shown, reinforced support 4 is carried out in the roadway in the original rock stress zone. The support method is two anchor cables 401 + steel beam active reinforced support 402. The distance between the anchor cables 401 on both sides and the adjacent coal wall does not exceed 200mm. The length of the anchor cables 401 is 1.5m and the spacing of the reinforced support 4 is 1.2m.

[0068] like Figure 4 As shown, the support method for the roadway in the stress-increased zone is two short anchor cables 503 + one long anchor cable 502 + active reinforcement support 501 with steel beams. The long anchor cable 502 is in the middle, and the distance between the short anchor cables 503 at both ends and the adjacent coal face does not exceed 200mm. The length of the short anchor cables 503 is 1.5m. The length of the long anchor cable 502 in the middle is 3m. The spacing of the roadway support 5 in the stress-increased zone is 0.6m.

[0069] (C) such as Figure 5 As shown, the first half of the excavation involves the retraction passage 7, the excavation of the transfer chamber 10, and the cornering 6; the first half of the retraction space support 8 is carried out simultaneously with the excavation, and the first half of the equipment is retracted.

[0070] (D) such as Figure 7 As shown, the second half of the excavation involves the retraction passage 7, the excavation of the transfer chamber 10 and the corner 6, and the retraction space support 8 and the retraction of the equipment in the second half.

[0071] In steps (C) and (D), the roof of the retraction channel 7 is designed to be inclined, forming a π-shaped roadway. The side closer to the hydraulic support 1 is the lower side, with a height of h, where h is the coal seam thickness. The side closer to the coal seam 2 is the higher side, and the height is calculated using the following formula:

[0072] .

[0073] like Figure 6As shown, the support method for the retreat space is a broken line support + single support 801 + π-shaped beam support 802, and the retreat space includes the retreat passage 7 and the chamber 10.

[0074] The zigzag support system includes a lower zigzag support 803 and an upper zigzag support 804 mounted on it. A wall shield 9, elongated and close to the coal face, is installed outside the lower zigzag support 803. A groove 901 is formed along the length of the wall shield 9, and the lower zigzag support 803 is fixed to the groove 901. The height of the lower zigzag support 803 is the same as the height of the single support 801. The π-shaped beam support 802 is inclined and has slots on both sides. These slots are fixed to the single support 801 and the upper zigzag support 804 respectively, securing them when providing initial support force. This ensures vertical support for the single support 801 on the left and vertical support for the upper zigzag support 804 on the right. The specific positions are calculated based on the roof angle and roadway height and can be determined before production. The π-shaped beam slot processing technology is a conventional technique. The upper zigzag support 804 is perpendicular to the π-shaped beam support 802.

[0075] The shield 9 is close to the coal face, and the lower support column 803 can just hold the shield 9 tightly against the coal face. The upper support column 804 is shorter and can directly contact the lower support column 803. Because the shield 9 has a groove 901, they are just locked together when the two provide initial support force. The shield 9 has a large area, which can make full use of the lateral support force of the coal face.

[0076] The height of the wall shield 9 is 150mm-250mm higher than that of the lower support column 803 of the folding section. The width is 300mm and the thickness is 12mm. The material is Q235 ordinary carbon structural steel. The groove 901 runs through the entire wall shield 9 from top to bottom. The inner diameter is equal to the maximum radius of the lower support column 803 of the folding section. The support spacing of the retraction space is 0.8m.

[0077] Starting from the main haulage roadway and ending at the auxiliary haulage roadway, the hydraulic supports 1 on the working face are numbered sequentially.

[0078] The method for retracting the first half of the equipment in step (C) specifically includes the following steps: retract the scraper conveyor and the coal mining machine, retract all the odd-numbered hydraulic supports 1 on the first half of the working face in forward order, and build timber stacks to support them behind them, then retract all the even-numbered hydraulic supports 1 on the first half of the working face in reverse order, and build timber stacks to support them behind them.

[0079] The method for retracting the second half of the equipment in step (D) specifically includes the following steps: retract all hydraulic supports 1 with even numbers on the second half of the working surface in reverse order, and build timber stacks to support them behind them; then retract all hydraulic supports 1 with odd numbers on the second half of the working surface in forward order, and build timber stacks to support them behind them.

[0080] Chamfer 6 is used to chamfer the radius of the coal face at the auxiliary transport end of the working face.y c 6. The rounding.

[0081] Example 2

[0082] Taking 128 hydraulic supports as an example:

[0083] 1. Determine the width and height of the retreat passage based on the range of the stress reduction zone caused by advance mining;

[0084] 2. At a position 15-20 m away from the stop line on the working face, begin drilling on the top plate of the working face. # ~64 # Starting at position 1 of the hydraulic support, a diamond-shaped metal mesh is hung to prevent the top from collapsing due to breakage of the working face.

[0085] 3. Strengthen the support for the working face end and roadway;

[0086] 4. Excavate the first half of the retreat passage 7, transfer chamber 10, round the corner radius 6, and provide roadway support for it;

[0087] 5. Retreat the scraper conveyor and coal mining machine;

[0088] 6. Upward retracement 1 # ~64 # The odd-numbered hydraulic support 1 in the middle is supported by a timber stack behind it;

[0089] 7. Reverse pullback 1 # ~64 # The even-numbered hydraulic support 1 in the middle is supported by a timber stack behind it;

[0090] 8. Excavate the second half of the retreat passage 7, transfer chamber 10, round off the radius 6, and provide roadway support for it;

[0091] 9. Reverse retracement 65 # ~128 # The even-numbered hydraulic support 1 in the middle is supported by a timber stack behind it;

[0092] 10. Upward retracement of 65 # ~128 # The odd-numbered hydraulic support 1 in the middle is supported by a timber stack behind it.

[0093] The detailed calculation methods and support methods involved are the same as in Example 1.

[0094] Example 3

[0095] A method for pre-excavation and support removal in two stages for a retreat channel includes the following steps:

[0096] (A) Determine the range of stress reduction zone for advance mining: Combine the on-site mining process and numerical simulation calculation to analyze the characteristics of the impact of advance mining on the fully mechanized longwall face, calculate the stress concentration coefficient and mining failure depth of the impact of advance mining on the fully mechanized longwall face, and then determine the range of stress reduction zone for mining.

[0097] The calculation process is as follows:

[0098] ① Determine the length of the basic top cantilever structure and the periodic pressure step distance based on the mining pressure manifestation law of the working face. L b Based on the principle of force equivalence, the equilibrium equation for the transmission of mining power in front of the coal face in a fully mechanized longwall mining face is established through integration:

[0099]

[0100] Taking a working face in a mine in Inner Mongolia as an example, the formula is: L b The step size is set to 15m for the period; e is the natural constant, which is the base of the natural logarithm function, and its value is 2.718. P z The stress is the original rock stress, taken as 14 MPa; ; m The thickness of the lateral edge coal and rock mass is taken as 5m; f The frictional resistance coefficient for lateral slippage of the coal-rock mass boundary is taken as 0.2; β is calculated to be 0.08. Uniaxial compressive strength, MPa The calculated uniaxial compressive strength is 4.08 MPa. C For cohesion, take 1.3 MPa; The internal friction angle is set to 25°. The calculated value is 2.46; P j The horizontal resistance of the coal face is taken as 0 MPa; y p The depth of coal face damage caused by advanced mining, in meters (m).

[0101] ② Perform univariate numerical calculations on step ① to obtain the depth of advance mining damage to the coal face in the fully mechanized longwall face. y p The calculated result is 11.71m.

[0102] ③ Calculate the stress concentration factor caused by mining from step ②: The calculated result is 2.40.

[0103] ④ The vertical stress distribution curve of the coal face under advance mining can be calculated from step ②;

[0104] ⑤ After calculating the advanced support stress curve, based on the calculated stress reduction zone distance... y p Determine the width y of the excavation and retreat passage. c :

[0105] make time The calculated y is y c Find y c =5.35m, meaning the width of the retreat passage is 5.35m.

[0106] The final vertical stress distribution curve of the coal face under advance mining is as follows: Figure 8 As shown: The stress change refers to the change in the stress distribution within coal seam 2 after excavation of a certain distance. The original stress distribution characteristics (γH) change to KγH, thus forming a stress reduction zone in front of the coal mining face. If this channel is excavated hundreds or tens of meters ahead of the coal seam 2 using traditional methods, the stress support point will definitely be crushed during the advancement of coal seam 2, causing damage and instability to the pre-excavated roadway. The present invention excavates the roadway within the stress reduction zone based on precise calculations, which not only ensures the safety, reliability and stability of the roadway, but also greatly reduces the excavation difficulty, lowers costs and improves excavation efficiency because the coal seam 2 within the stress reduction zone has already undergone plastic deformation.

[0107] At a distance of 15-20 m from the stop line, diamond-shaped metal mesh is hung on the top plate of the working face above the location of the first half hydraulic support 1 to prevent the top of the working face from collapsing due to breakage.

[0108] (B) Support for the area affected by advanced mining:

[0109] like Figure 2 As shown, end supports 3 are provided at both ends of the working face. The support method is two single columns 301 + π-shaped beam passive support 302. The distance between the single columns 301 on both sides and the adjacent coal wall does not exceed 200mm. The spacing of the end supports 3 is 0.6m.

[0110] like Figure 3 As shown, reinforced support 4 is carried out in the roadway in the original rock stress zone. The support method is two anchor cables 401 + steel beam active reinforced support 402. The distance between the anchor cables 401 on both sides and the adjacent coal wall does not exceed 200mm. The length of the anchor cables 401 is 1.5m and the spacing of the reinforced support 4 is 1.2m.

[0111] like Figure 4As shown, the support method for the roadway in the stress-increased zone is two short anchor cables 503 + one long anchor cable 502 + active reinforcement support 501 with steel beams. The long anchor cable 502 is in the middle, and the distance between the short anchor cables 503 at both ends and the adjacent coal face does not exceed 200mm. The length of the short anchor cables 503 is 1.5m. The length of the long anchor cable 502 in the middle is 3m. The spacing of the roadway support 5 in the stress-increased zone is 0.6m.

[0112] (C) such as Figure 5 As shown, the first half of the excavation involves the retraction passage 7, the excavation of the transfer chamber 10, and the cornering 6; the first half of the retraction space support 8 is carried out simultaneously with the excavation, and the first half of the equipment is retracted.

[0113] (D) such as Figure 7 As shown, the excavation includes the retraction passage 7 in the second half of the excavation, the excavation of the transfer chamber 10, and the corner 6; the retraction space support 8 in the second half of the excavation is carried out simultaneously with the retraction of the equipment in the second half of the excavation.

[0114] In steps (C) and (D), the roof of the retraction channel 7 is designed to be inclined, forming a π-shaped roadway. The side closer to the hydraulic support 1 is the lower side, with a height of h, where h is the coal seam thickness. The side closer to the coal seam 2 is the higher side, and the height is calculated using the following formula:

[0115] .

[0116] Calculate based on the parameters in step (A),

[0117] like Figure 6 As shown, the support method for the retreat space is a broken line support + single support 801 + π-shaped beam support 802, and the retreat space includes the retreat passage 7 and the chamber 10.

[0118] The zigzag support system includes a lower zigzag support 803 and an upper zigzag support 804 mounted on it. A wall shield 9, elongated and close to the coal face, is installed outside the lower zigzag support 803. A groove 901 is formed along the length of the wall shield 9, and the lower zigzag support 803 is fixed to the groove 901. The height of the lower zigzag support 803 is the same as the height of the single support 801. The π-shaped beam support 802 is inclined and has slots on both sides. These slots are fixed to the single support 801 and the upper zigzag support 804 respectively, securing them when providing initial support force. This ensures vertical support for the single support 801 on the left and vertical support for the upper zigzag support 804 on the right. The specific positions are calculated based on the roof angle and roadway height and can be determined before production. The π-shaped beam slot processing technology is a conventional technique. The upper zigzag support 804 is perpendicular to the π-shaped beam support 802.

[0119] The shield 9 is close to the coal face, and the lower support column 803 can just hold the shield 9 tightly against the coal face. The upper support column 804 is shorter and can directly contact the lower support column 803. Because the shield 9 has a groove 901, they are just locked together when the two provide initial support force. The shield 9 has a large area, which can make full use of the lateral support force of the coal face.

[0120] The height of the wall shield 9 is 150mm-250mm higher than that of the lower support column 803 of the folding section. The width is 300mm and the thickness is 12mm. The material is Q235 ordinary carbon structural steel. The groove 901 runs through the entire wall shield 9 from top to bottom. The inner diameter is equal to the maximum radius of the lower support column 803 of the folding section. The support spacing of the retraction space is 0.8m.

[0121] Starting from the main haulage roadway and ending at the auxiliary haulage roadway, the hydraulic supports 1 on the working face are numbered sequentially.

[0122] The method for retracting the first half of the equipment in step (C) specifically includes the following steps: retract the scraper conveyor and the coal mining machine, retract all the odd-numbered hydraulic supports 1 on the first half of the working face in forward order, and build timber stacks to support them behind them, then retract all the even-numbered hydraulic supports 1 on the first half of the working face in reverse order, and build timber stacks to support them behind them.

[0123] The method for retracting the second half of the equipment in step (D) specifically includes the following steps: retract all hydraulic supports 1 with even numbers on the second half of the working surface in reverse order, and build timber stacks to support them behind them; then retract all hydraulic supports 1 with odd numbers on the second half of the working surface in forward order, and build timber stacks to support them behind them.

[0124] Chamfer 6 is used to chamfer the radius of the coal face at the auxiliary transport end of the working face. y c 6. The rounding.

[0125] Example 4

[0126] Taking 148 hydraulic supports as an example:

[0127] 1. Determine the width and height of the retreat passage based on the range of the stress reduction zone caused by advance mining;

[0128] 2. At a position 15-20 m away from the stop line on the working face, begin drilling on the top plate of the working face. # ~74 # Starting at position 1 of the hydraulic support, a diamond-shaped metal mesh is hung to prevent the top from collapsing due to breakage of the working face.

[0129] 3. Strengthen the support for the working face end and roadway;

[0130] 4. Excavate the first half of the retreat passage 7, transfer chamber 10, round the corner radius 6, and provide roadway support for it;

[0131] 5. Retreat the scraper conveyor and coal mining machine;

[0132] 6. Upward retracement 1 # ~74 # The odd-numbered hydraulic support 1 in the middle is supported by a timber stack behind it;

[0133] 7. Reverse pullback 1 # ~74 # The even-numbered hydraulic support 1 in the middle is supported by a timber stack behind it;

[0134] 8. Excavate the second half of the retreat passage 7, transfer chamber 10, round off the radius 6, and provide roadway support for it;

[0135] 9. Reverse retracement 75 # ~148 # The even-numbered hydraulic support 1 in the middle is supported by a timber stack behind it;

[0136] 10. Upward retracement of 75 # ~148 # The odd-numbered hydraulic support 1 in the middle is supported by a timber stack behind it.

[0137] The detailed calculation methods and support methods involved are the same as in Example 1.

[0138] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for two-step pre-excavation of a retreat passage and support retreat, characterized in that: It comprises the following steps: (A) determining the scope of the stress reduction area: combining the field recovery process and numerical simulation calculation, the stress concentration coefficient and mining damage depth of the fully mechanized working face are calculated, and then the scope of the mining stress reduction area is determined; The calculation process is as follows: ① According to the mining pressure appearance law of working face, the length of basic roof cantilever structure is determined to take periodic pressure step distance L b According to the force equivalence principle, the mining force transmission balance equation in front of the coal wall of the fully mechanized working face is established by integration: In the formula: L b is the period of the step distance, m; e, a natural constant, is the base of the natural logarithm function, with a value of 2.718; P z σ, the original rock stress, is in MPa; ; σc, the uniaxial compressive strength, is in MPa; m h, the lateral edge coal rock mass thickness, is in m; f μ, the friction resistance coefficient of lateral coal rock mass boundary dislocation, is dimensionless; σc, the uniaxial compressive strength, is in MPa, ; σc, the uniaxial compressive strength, is in MPa; C c, the cohesion, is in MPa; φ, the internal friction angle, is in °; ; σc, the uniaxial compressive strength, is in MPa, P j σh, the horizontal resistance of the coal wall, is in MPa; y p m is the depth of the coal wall advanced mining damage. ② Single variable numerical calculation is carried out on step ① to obtain the advanced mining damage depth of coal wall of fully mechanized working face y p ; ③ Calculate the stress concentration factor of mining by step ②: ; (4) calculating the vertical stress distribution of the fully mechanized working face coal wall affected by the advanced mining according to step 2: In the formula: , is the mining vertical stress in the advanced coal and rock failure zone and the elastic zone in front of the coal wall, MPa; ⑤ After calculating the advanced support stress curve, based on the calculated stress reduction zone distance... y p Determine the width y of the excavation and retreat passage. c : Let the time be , the calculated y is y c ; (B) supporting the advanced mining influence area; (C) excavating the first half of the withdrawal channel, excavating the transfer chamber and the corner; excavating while supporting the first half of the withdrawal space and withdrawing the first half of the equipment; (D) excavating the second half of the withdrawal channel, excavating the transfer chamber and the corner; excavating while supporting the second half of the withdrawal space and withdrawing the second half of the equipment.

2. The method of claim 1, wherein: The support of the advanced mining influence area in step (B) is as follows: The end support is carried out at both ends of the working face, and the support mode is two single columns + π type beam passive support, the distance between the single column on both sides and the adjacent coal wall is not more than 200mm, and the end support interval is 0.6m; The reinforcement support is carried out in the roadway of the original rock stress area, and the support mode is two anchor cables + steel beam active reinforcement support, the distance between the anchor cable on both sides and the adjacent coal wall is not more than 200mm, the length of the anchor cable is 1.5m, and the reinforcement support interval is 1.2m; The support mode of the stress increasing area roadway is two short anchor cables + one long anchor cable + steel beam active reinforcement support, the long anchor cable is in the middle, the distance between the short anchor cable at both ends and the adjacent coal wall is not more than 200mm, the length of the short anchor cable is 1.5m; the length of the long anchor cable in the middle is 3m, and the stress increasing area roadway support interval is 0.6m.

3. The method of claim 1, wherein: The roof of the withdrawal channel in step (C) and step (D) is designed as inclined, which is inclined π shaped roadway, the side close to the hydraulic support is lower side, the height is h, h is the thickness of coal seam, the side close to the coal seam is higher side, the height calculation formula is as follows: 。 4. The method of claim 3, wherein: The support mode of the withdrawal space in step (C) and step (D) is fold line prop + single prop + π type beam support, and the withdrawal space includes withdrawal channel and chamber; The fold line prop includes fold line lower prop and fold line upper prop arranged thereon, a wall shield is arranged outside the fold line lower prop, the wall shield is long strip shape, close to the coal wall, a groove is arranged on the wall shield along the length direction thereof, the fold line lower prop is fixed on the groove, the height of the fold line lower prop is consistent with the height of the single prop, the π type beam is arranged inclined, the two sides are provided with clamping grooves, which are respectively fixed with the single prop and the fold line upper prop, and the fold line upper prop is perpendicular to the π type beam.

5. The method according to claim 4, wherein: The height of the wall shield is 150-250mm higher than that of the fold line lower prop, the width is 300mm, the thickness is 12mm, the material is Q235 ordinary carbon structural steel, the groove penetrates through the whole wall shield, the inner diameter is equal to the maximum radius of the fold line lower prop; the support interval of the withdrawal space is 0.8m.

6. The method of claim 1, wherein: In step (A) further comprises the following steps: in the working face distance from the stop line 15~20 m position, start to the upper working face roof on the location of the front half of the hydraulic support hanging diamond metal net to prevent the working face broken top caving.

7. The method of claim 1, wherein: With the main transport gangway as the starting point and the auxiliary transport gangway as the terminal point, the hydraulic supports on the working face are sequentially numbered. The method for withdrawing the front half of the equipment in step (C) specifically comprises the following steps: withdrawing the scraper conveyor and the coal mining machine, withdrawing all the odd-numbered hydraulic supports on the front half of the working face in normal order, supporting behind with wood piles, and then withdrawing all the even-numbered hydraulic supports on the front half of the working face in reverse order, supporting behind with wood piles. The method for withdrawing the rear half of the equipment in step (D) specifically comprises the following steps: withdrawing all the even-numbered hydraulic supports on the rear half of the working face in reverse order, supporting behind with wood piles, and then withdrawing all the odd-numbered hydraulic supports on the rear half of the working face in normal order, supporting behind with wood piles.

8. The method of claim 1, wherein: The smearing angle is a smearing angle with a radius of 0.5-1.5 m for the coal side of the auxiliary transportation end head of the working face. y c the smearing angle is a smearing angle with a radius of 0.5-1.5 m for the coal

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