Coal pillar digging entry retaining stress source control method

Abstract

The invention relates to the technical field of coal mine roadway surrounding rock control, in particular to a coal pillar digging entry retaining stress source control method which comprises the following steps: before stoping of an upper section working face, arranging a plurality of top cutting drill holes along the trend of the working face, the top cutting drill hole is vertical to the trend of the working surface; carrying out top cutting treatment on the top cutting drill hole to form a through top cutting surface along the trend of the working surface; the upper section working face is stoped, so that the overlying strata top plate is fractured and collapsed along the top cutting face; and after the overlying strata roof collapses stably, tunneling or stoping operation of the lower section working face roadway is carried out, stress transmission and superposition can be effectively avoided through the coal pillar tunneling entry retaining stress source control method provided by the embodiment of the invention, and then the influence of mining-induced stress on the lower section roadway is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of surrounding rock control of coal mine tunnels, and in particular to a method for controlling stress sources of coal pillar excavation and retention tunnels. Background Art

[0002] Coal pillar excavation and retention is a common tunnel layout method in coal mining. Its stress environment is complex and is mainly affected by the mining stress caused by the mining of the upper and lower sections. In the prior art, the surrounding rock control of coal pillar excavation and retention mainly adopts the following methods: one method is to increase the support strength and resist the influence of mining stress by arranging a high-strength support system. For example, support means such as high-strength anchor rods, anchor cables or hydraulic supports are used. However, this method has the following problems: on the one hand, the support cost is high and the construction process is complicated; on the other hand, due to the continuous effect of mining stress, the support system is prone to failure and requires frequent maintenance and reinforcement, which affects production efficiency. Another method is to adopt pre-reinforcement technology, such as grouting reinforcement, pre-cracking and cutting. Although these methods have improved the surrounding rock conditions of the tunnel to a certain extent, they are still passive protection measures and cannot fundamentally solve the problem of the influence of mining stress. Especially in the mining process of the upper and lower sections, the superposition effect of mining stress is more significant, resulting in serious deformation and damage of the tunnel.

[0003] At present, coal pillar excavation and retention roadways mainly face the following technical problems: when the upper section working face is mined, the mining stress is transmitted to the lower section roadway through the overburden, causing the roadway surrounding rock to become unstable and damaged; the residual mining stress in the upper section and the advanced mining stress in the lower section are superimposed and coupled, causing the roadway to bear double stress disturbance; the continuous effect of mining stress leads to a decrease in the effectiveness of the support system, which requires repeated reinforcement and maintenance; the existing control methods are mostly passive support, which makes it difficult to control the generation and transmission of mining stress from the source.

[0004] Therefore, there is an urgent need for a technical solution that can control mining stress at the source and avoid stress transfer and superposition. Summary of the invention

[0005] The present invention provides a method for controlling the stress source of coal pillar excavation and retained laneway, which can effectively avoid stress transfer and superposition, thereby effectively reducing the influence of mining stress on the lower section laneway.

[0006] An embodiment of the present invention provides a method for controlling stress sources in coal pillar excavation and retention lanes, comprising the following steps: before mining at the upper section working face, arranging a plurality of top cutting drill holes along the direction of the working face, the top cutting drill holes being perpendicular to the direction of the working face; performing top cutting treatment on the top cutting drill holes to form a through top cutting surface along the direction of the working face; mining at the upper section working face to cause the overburden roof to fracture and collapse along the top cutting surface; after the collapse of the overburden roof is stable, excavating or mining operations are carried out at the lower section working face lanes.

[0007] In a possible implementation, the topping process is hydraulic fracturing or explosive topping.

[0008] In a possible implementation, when hydraulic fracturing is used, the layout parameters of the top-cutting boreholes are: the borehole depth is 40-60 m; the spacing between adjacent boreholes is 8-10 m; and the angle between the borehole and the horizontal plane is 40°-60°.

[0009] In a possible implementation, when hydraulic fracturing is used, the following steps are included: in each top-cut borehole, a staged fracturing method is used; the length of each stage of fracturing is 3m; the fracturing pressure is 15-20MPa; the duration of a single stage of fracturing is 20-30min; and fracturing is performed in sequence from the bottom of the hole to the hole mouth.

[0010] In a possible implementation, a pressure holding time of 5-10 minutes is set between adjacent fracturing stages.

[0011] In a possible implementation, when hydraulic fracturing is used, before hydraulic fracturing is performed, the method further includes: performing a water pressure test on the top cut borehole; and determining a fracturing initiation pressure according to the result of the water pressure test.

[0012] In a possible implementation, when blasting is used for top cutting, the method includes: loading explosives in the top cutting borehole; using a millisecond delay detonation method; and detonating in sequence from the bottom of the hole to the hole mouth.

[0013] In a possible implementation, the top cutting surface is located at the edge of the goaf of the upper section working surface.

[0014] In a possible implementation, when applied to coal pillar roadway retention: the top cutting operation is completed before mining at the upper section working face; and the above steps are performed when the excavation of the lower section roadway has been completed.

[0015] In a possible implementation, when applied to coal pillar tunneling: after the mining of the upper section working face is completed and the overburden roof collapses and stabilizes; the tunneling operation of the lower section tunnel is carried out.

[0016] The present invention provides a method for controlling the stress source of coal pillar excavation and retention lanes. The method for controlling the stress source of coal pillar excavation and retention lanes arranges a top cutting drill hole and performs a top cutting process before mining at the upper section working face, so that the overburden roof breaks and collapses along the preset top cutting surface, thereby changing the traditional mining stress transmission mechanism. Field application verification has shown that this source control method can avoid the formation of a cantilever beam overburden structure, causing the roof to collapse in the expected direction, and effectively reducing the impact of mining stress on the lower section laneway. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 The present invention provides a flow chart of a method for controlling the stress source of coal pillar excavation and retention.

[0019] Figure 2 It is a schematic diagram of the inclined overburden structure and stress distribution after mining of the upper section working face when the top is not cut in the prior art.

[0020] Figure 3 It is a schematic diagram of the inclined overburden structure and stress distribution after mining of the upper section working face provided by the present invention.

[0021] Figure 4 It is a plan view schematic diagram of a drilling arrangement provided by the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Combine the following Figure 1-4 A method for controlling the stress source of a coal pillar excavation and retention roadway provided by an embodiment of the present invention is described, comprising the following steps: S1. Before mining in the upper section working face, multiple top cutting drill holes are arranged along the working face direction, and the top cutting drill holes are perpendicular to the working face direction; S2, performing a top cutting process on the top cutting drill hole to form a through top cutting surface along the direction of the working surface; S3, mining the upper section working face to cause the overburden roof to fracture and collapse along the cutting top surface; S4. After the overburden roof collapses and stabilizes, excavation or mining operations are carried out in the tunnel of the lower section working face.

[0024] In the embodiment of the present invention, by arranging top cutting drill holes and performing top cutting treatment before mining the upper section working face, the overburden roof is broken and collapsed along the preset top cutting surface, thereby changing the traditional mining stress transfer mechanism. Through field application verification, this source control method can avoid the formation of a cantilever beam overburden structure, causing the roof to collapse in the expected direction, effectively reducing the impact of mining stress on the lower section roadway. Specifically, measured data show that after adopting this method, the roof subsidence of the lower section roadway is reduced by 65%, the convergence of the two sides is reduced by 58%, and the bottom drum is reduced by 70%, providing a strong guarantee for the stability of the roadway.

[0025] If the top cutting method is not adopted before the upper section working face is mined, the overburden structure and stress distribution after the working face is mined will be as follows: Figure 2 As shown in the figure, A is the original stress area, B is the stress increase area, C is the stress reduction area; D is the stress stability area, and P is the soil pressure. If the top cutting measure is taken, the overburden structure and stress distribution after the working face is mined are as follows: Figure 3 As shown, A is the original stress area, B is the stress increase area, C is the stress reduction area; D is the stress stability area, and P is the soil pressure. Figure 2 and Figure 3 The mechanical mechanism of regulating mining stress is explained as follows: for coal pillar retained lanes, blasting or hydraulic fracturing is used to cut off the overburden roof of the working face in advance before mining. After mining, the overburden roof naturally collapses to the goaf along the cut top surface. The working face no longer forms an overburden structure attached to the coal pillar. The overburden structure is changed by cutting the top, eliminating the source of mining stress. Therefore, the mining lanes of the lower section working face adjacent to the coal pillar are no longer affected by lateral mining stress after mining of the upper section working face, solving the mining influence of the upper section working face mining on the coal pillar retained lanes. For coal pillar excavation, the excavation is in the original rock stress environment and is almost unaffected. Regardless of coal pillar retained lanes or coal pillar excavation, the lanes of the lower section working face are only affected by the advanced mining stress of the working face during mining.

[0026] In some embodiments, the topping process is performed by hydraulic fracturing or explosive topping.

[0027] In the embodiment of the present invention, two optional cutting methods, hydraulic fracturing and blasting cutting, are provided, so that the method of the present invention can adapt to different geological conditions. Under soft rock conditions, hydraulic fracturing can be preferred to avoid the disturbance of blasting to the surrounding rock; under hard rock conditions, blasting cutting can be used to overcome the problem of unsatisfactory hydraulic fracturing effect. Engineering practice shows that this flexible technical solution significantly improves the applicability of the method and better guarantees the cutting effect.

[0028] In some embodiments, when hydraulic fracturing is used, the arrangement parameters of the top-cut boreholes are: the borehole depth is 40-60 m; the spacing between adjacent boreholes is 8-10 m; and the angle between the borehole and the horizontal plane is 40°-60°.

[0029] The embodiment of the present invention clarifies the drilling arrangement parameters during hydraulic fracturing. Among them, the drilling depth of 40-60m ensures the effective height of the cutting top surface, the drilling spacing of 8-10m ensures the connectivity of the fracturing cracks, and the drilling inclination of 40°-60° is convenient for construction and can achieve an ideal cutting top effect. These parameters are obtained through a large number of experimental optimizations, which can reduce the construction difficulty and cost while ensuring the cutting top effect. The measured data show that after adopting this set of parameters, the penetration rate of the fracturing cracks reaches more than 95%.

[0030] In some embodiments, when hydraulic fracturing is used, the following steps are included: in each top-cut borehole, a staged fracturing method is used; the length of each stage of fracturing is 3m; the fracturing pressure is 15-20MPa; the duration of a single stage of fracturing is 20-30min; and fracturing is performed in sequence from the bottom of the hole to the hole mouth.

[0031] In the embodiment of the present invention, for the setting of hydraulic fracturing process parameters, a staged fracturing method is adopted and various specific parameters are clarified to make the fracturing process more controllable. The segment length of 3m is convenient for pressure control, the fracturing pressure of 15-20MPa ensures sufficient fracturing without causing excessive crushing, and the fracturing time of 20-30min ensures that the cracks are fully developed. The fracturing sequence from the bottom of the hole to the hole mouth is conducive to the formation of a continuous cut top surface. Field applications have shown that the success rate of this fracturing method exceeds 90%.

[0032] In some embodiments, a pressure holding time of 5-10 minutes is set between adjacent fracturing stages.

[0033] In the embodiment of the present invention, by setting a pressure holding time of 5-10 minutes between adjacent fracturing sections, the fracturing cracks have sufficient expansion time. Microseismic monitoring data show that during this pressure holding time, the fracturing cracks are still slowly expanding, and the crack network finally formed is more complete. Practice has proved that the setting of this process parameter improves the reliability of the fracturing effect.

[0034] In some embodiments, when hydraulic fracturing is used, before hydraulic fracturing is performed, the method further includes: performing a water pressure test on the top cut borehole; and determining the fracturing initiation pressure according to the result of the water pressure test.

[0035] In the embodiment of the present invention, a water pressure test is performed before the formal fracturing, so that the fracture pressure of the formation can be accurately obtained, providing a basis for determining the formal fracturing parameters. This pre-test method avoids the blindness of fracturing parameter selection, improves the success rate of fracturing, and also avoids excessive crushing of the surrounding rock caused by excessive pressure. Field data shows that after adopting this method, the accuracy of fracturing parameters is improved by 40%.

[0036] In some embodiments, when blasting is used to cut the top, the method includes: loading explosives in the top cutting drill hole; using a millisecond delay detonation method; and detonating in sequence from the bottom of the hole to the hole mouth.

[0037] In the embodiment of the present invention, for the blasting top cutting method, the millisecond delay detonation technology is used and the detonation is carried out in a specific order, which can produce a good penetration effect. This detonation method can not only ensure the continuity of the top cutting surface, but also control the superposition effect of blasting vibration. Actual measurements show that with this blasting scheme, the continuity of the top cutting surface reaches more than 85%, and the disturbance of the surrounding rock formation is controlled within an acceptable range.

[0038] In some embodiments, the position of the top cutting surface is located at the edge of the goaf of the upper section working face and 10-15 m on one side of the goaf.

[0039] In the embodiment of the present invention, the top cutting surface is set at the edge of the goaf of the upper section working face, 10-15m away from the goaf. This position selection fully considers the need for overburden structure control. Practice has proved that this position can ensure the top cutting effect without affecting the safety of the upper section working face. Monitoring data shows that this position setting makes the overburden collapse more regular and the pressure release of the goaf more sufficient.

[0040] In some embodiments, when applied to coal pillar roadway retention: the top cutting operation is completed before mining at the upper section working face; and the above steps are performed when the excavation of the lower section roadway has been completed.

[0041] In the embodiment of the present invention, for the coal pillar lane retention working condition, the top cutting operation is completed before the upper section working face is mined, which can change the overburden structure in advance and avoid the influence of mining stress on the excavated lane. Measured data show that this construction sequence arrangement reduces the lane deformation during the lane retention process by more than 60%, reduces the support cost by 42%, and reduces the maintenance times by 76%.

[0042] In some embodiments, when applied to coal pillar tunneling: after the upper section working face is mined and the overburden roof collapses and stabilizes; the tunneling operation of the lower section is carried out.

[0043] In the embodiment of the present invention, for the coal pillar tunneling condition, tunneling is carried out after the upper section working face is mined and the overburden roof collapse is stable, which can ensure that the tunneling working face is in a relatively stable stress environment. Field application has proved that this construction sequence increases the tunneling speed by 35%, reduces the support workload by 45%, and significantly improves the tunnel quality.

[0044] The stress source control method for coal pillar excavation and retention provided by the present invention arranges top cutting drilling holes and performs top cutting treatment before mining at the upper section working face, so that the overburden roof breaks and collapses along the preset top cutting surface, thus changing the traditional mining stress transmission mechanism. Through field application verification, this source control method can avoid the formation of a cantilever beam overburden structure, causing the roof to collapse in the expected direction, effectively reducing the impact of mining stress on the lower section roadway.

[0045] The coal pillar excavation and retention lane is a typical type of strong mining dynamic pressure lane in my country's coal mines. Its maintenance and control are quite difficult and have become the main obstacle to the safe production of coal mine recovery working faces. The present invention specifically proposes a "method for controlling the source of mining stress in the coal pillar excavation and retention lane", which is a practical and effective way to crack the surrounding rock control of this type of lane. The present invention is aimed at controlling mine pressure rock formations and has significant innovation. It can not only solve the problem of surrounding rock control of large deformation dynamic pressure lanes of coal mine excavation and retention type, make up for the shortcomings of existing inventions, but also promote and develop the theory and method of surrounding rock control of coal mine lanes, and also promote the innovative development of the discipline of mine pressure and rock formation control.

[0046] Provide specific embodiments of the present invention below: Example 1: Stress source control method for coal pillar excavation and retention based on hydraulic fracturing This embodiment is applied on site in a coal mine. The specific parameters of the mine are as follows: the average thickness of the mined coal seam is 4.5m, the burial depth is about 580m, the roof is medium-thick layered sandstone, and the immediate roof is thin-layered mudstone. The length of the mining working face is 180m, and the inclination angle is 8°. The working face adopts the fully mechanized top coal caving technology, and the mining height is 3.5m.

[0047] Through preliminary theoretical analysis and numerical simulation, the optimal process parameters and construction procedures were determined. First, before the upper section working face was mined, the top cutting boreholes were arranged along the working face. After multiple sets of comparative tests, the optimal drilling arrangement parameters were determined: drilling depth 50m, adjacent drilling spacing 9m, and drilling angle 45° with the horizontal plane. The basis for selecting these parameters is: when the drilling depth is less than 40m, the top cutting effect is not ideal due to the requirement of overburden breaking height; when the drilling depth is greater than 60m, it not only increases the construction difficulty, but also the fracturing effect is not significantly improved. A drilling spacing of less than 8m will result in too many drilling holes and a significant increase in construction costs; a spacing greater than 10m will make it difficult for the fracturing cracks to penetrate. The angle between the borehole and the horizontal plane is most suitable in the range of 40°-60°. When it is lower than 40°, the fracturing effect is poor, and when it is higher than 60°, drilling construction is difficult.

[0048] Before hydraulic fracturing, a water pressure test is first conducted on the top-cut borehole, which is a key step in determining the fracturing parameters. The test adopts a step-by-step pressurization method, with the pressure starting from 5MPa and increasing by 2MPa each time for 5 minutes. By recording the water absorption under different pressures and drawing a pressure-water absorption curve, when the pressure reaches 18MPa, the water absorption suddenly increases, indicating that the formation fracturing pressure has been reached. Based on this, the working pressure during formal fracturing is determined to be 20MPa to ensure sufficient fracturing effect.

[0049] Hydraulic fracturing is carried out in a staged fracturing mode. The length of each fracturing section is determined to be 3m, which is obtained through field test optimization: when the segment length is less than 3m, the fracturing efficiency is low; when it is greater than 3m, pressure control is difficult. The fracturing process is strictly carried out in the order from the bottom of the hole to the hole mouth, and the duration of each fracturing section is controlled at 25min. This time is determined by monitoring the diffusion range of the fracturing fluid: when the duration is less than 20min, the fracturing cracks are not fully developed; after more than 30min, the fracturing effect is not significantly improved. An 8min pressure holding time is set between adjacent fracturing sections for full expansion of the cracks.

[0050] In order to monitor the fracturing effect in real time, a fluorescent tracer is added to the fracturing fluid at a concentration of 0.01%. The crack expansion is monitored by a special tracer detection device. When the tracer signal between adjacent boreholes is detected, it indicates that the fracturing crack has been connected. At the same time, a microseismic monitoring system is arranged, including 8 microseismic sensors with a sampling frequency of 100Hz, which is used to capture microseismic signals during the fracturing process. By analyzing the spatial distribution of microseismic signals, the direction and range of the fracturing cracks can be accurately determined.

[0051] Example 2: Stress source control method for coal pillar excavation and retention based on blasting top cutting Due to the limitation of geological conditions in a certain mining area, the hydraulic fracturing effect is not ideal, so the blasting top cutting method is used. The coal seam in this mining area is buried at a depth of 620m, and the roof is a thick layer of sandstone with good integrity. The specific implementation process of blasting top cutting is as follows: The drilling arrangement parameters are basically the same as those of hydraulic fracturing, but the borehole diameter is increased to 90mm to allow for sufficient explosive loading. The charge is loaded in intervals, with a charge length to air interval ratio of 3:1. No. 2 rock emulsion explosive is used, with a single-stage charge of 2.5kg. The millisecond delay detonation method is used, with a delay time of 50ms between adjacent charge sections, which can produce a good penetration effect. The detonation sequence is also from the bottom of the hole to the hole mouth to ensure the continuity of the cut top surface.

[0052] The determination of blasting parameters has undergone a large number of numerical simulations and field tests. When the charge is less than 2kg, the blasting energy is insufficient and it is difficult to form an effective top-cut surface; when the charge is greater than 3kg, it will cause excessive fragmentation of the surrounding rock formations. When the delay time is less than 30ms, the blasting vibration will be superimposed; when it is greater than 70ms, it is difficult to form a continuous top-cut surface.

[0053] In order to monitor the blasting effect, vibration meters are arranged around the blasting area to record the blasting vibration waveform. By analyzing the characteristics of the vibration waveform, the formation of the top cut surface can be judged. At the same time, the drilling TV is used to observe the condition of the hole wall after blasting and evaluate the blasting effect.

[0054] Example 3: Comparison of application effects under different geological conditions In order to verify the applicability of the method of the present invention, application tests were carried out in soft rock, hard rock and complex geological conditions: Soft rock conditions (the roof is mudstone, uniaxial compressive strength <30MPa): By using hydraulic fracturing, the fracturing pressure was reduced to 15MPa and the fracturing time was extended to 30min. Practice has shown that this combination of parameters can form an ideal top cutting surface under soft rock conditions. Monitoring results show that the overburden collapses more fully after top cutting and the pressure release of the goaf is more thorough.

[0055] Hard rock conditions (top plate is sandstone, uniaxial compressive strength> 80MPa): The blasting top cutting method is preferred, the charge is increased to 2.8kg / section, and the delay time is appropriately shortened to 40ms. Through high-speed photography, it is observed that this combination of parameters can produce an ideal fracture effect under hard rock conditions.

[0056] Complex geological conditions (fault development areas): A combination of hydraulic fracturing and blasting is used. First, a small-scale hydraulic fracturing test is carried out, and the appropriate cutting method is selected according to the fracturing effect. Practice has proved that this flexible treatment method can adapt to different geological conditions.

[0057] Through promotion and application in multiple mining areas, the method of the present invention has achieved remarkable economic and technical effects: Support costs: Compared with traditional methods, the cost of tunnel support is reduced by 42% on average. This is mainly because after the top cutting treatment, the stress environment of the tunnel surrounding rock is improved and the support strength can be reduced accordingly.

[0058] Work efficiency: The excavation speed increased by 35% and the recovery efficiency increased by 28%. This is because the influence of mining stress was eliminated and the working environment became more stable.

[0059] Safety performance: The tunnel deformation was reduced by 65% ​​and the roof accident rate was reduced by 85%, which fully demonstrated the advantages of the method of the present invention in controlling the stability of surrounding rock.

[0060] Service life: The service life of the tunnel was extended by 1.8 times, and the number of maintenance times was reduced by 76%, which shows that the method of the present invention has a good long-term effect.

[0061] It should be noted that the above embodiments are only preferred implementations of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art may modify and change the present invention without departing from the spirit and scope of the present invention. For example, the arrangement of the top drilling holes may be appropriately adjusted according to the actual geological conditions; the fracturing parameters may be optimized according to the rock formation characteristics; the blasting parameters may be adjusted according to the on-site conditions; and the monitoring method may adopt other appropriate technical means.

[0062] The present invention changes the overburden structure by implementing top cutting treatment before mining the upper section working face, thereby fundamentally eliminating the conditions for the formation of mining stress. Different from the passive support method in the prior art, the present invention adopts an active control strategy and has significant innovation. At the same time, the present invention provides two top cutting methods, hydraulic fracturing and blasting top cutting, which enhances the applicability and operability of the method. It has been proved through a large number of engineering practices that the method of the present invention has significant technical effects and economic benefits, and has good promotion and application value.

[0063] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, i.e., they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Those of ordinary skill in the art may understand and implement it without creative effort.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the stress source of coal pillar excavation and retention, characterized in that: The following steps are involved: Before mining the upper section working face, a plurality of top cutting drill holes are arranged along the working face direction, wherein the top cutting drill holes are perpendicular to the working face direction; Performing a top cutting process on the top cutting drill hole to form a through top cutting surface along the direction of the working surface; The upper section working face is mined to cause the overburden roof to fracture and collapse along the top cutting surface; After the overburden roof collapses and stabilizes, excavation or mining operations are carried out in the lower section working face tunnel.

2. The method for controlling the stress source of coal pillar excavation and retention according to claim 1 is characterized in that: The topping treatment adopts hydraulic fracturing or blasting topping.

3. The method for controlling the stress source of coal pillar excavation and retention according to claim 2 is characterized in that: When hydraulic fracturing is used, the arrangement parameters of the top cutting drilling holes are: The drilling depth is 40-60m; The spacing between adjacent boreholes is 8-10m; The angle between the drill hole and the horizontal plane is 40°-60°.

4. The method for controlling the stress source of coal pillar excavation and retention according to claim 2 is characterized in that: When hydraulic fracturing is used, the following steps are involved: In each top-cut borehole, staged fracturing is used; The length of each fracturing section is 3m; The fracturing pressure is 15-20MPa; The duration of single-stage fracturing is 20-30 minutes; Fracturing is carried out in sequence from the bottom of the hole to the hole mouth.

5. The method for controlling the stress source of coal pillar excavation and retention according to claim 4 is characterized in that: Set a pressure holding time of 5-10 minutes between adjacent fracturing stages.

6. The method for controlling the stress source of coal pillar excavation and retention according to claim 2, characterized in that: When hydraulic fracturing is used, before hydraulic fracturing is carried out, it also includes: Performing a water pressure test on the top-cut borehole; The fracturing initiation pressure is determined based on the water pressure test results.

7. The method for controlling the stress source of coal pillar excavation and retention according to claim 2, characterized in that: When blasting is used, it includes: charging explosives in the top cut drill hole; Adopt millisecond delay detonation method; Detonate in sequence from the bottom of the hole to the hole mouth.

8. The method for controlling the stress source of coal pillar driving and retaining lane according to any one of claims 1 to 7, characterized in that: The position of the top cutting surface is located at the edge of the goaf area of ​​the upper section working face.

9. The method for controlling the stress source of coal pillar driving and retaining roadway according to any one of claims 1 to 7, characterized in that: When applied to coal pillar retaining: Complete the top cutting operation before mining in the upper section working face; The above steps are carried out after the excavation of the lower section tunnel has been completed.

10. The method for controlling the stress source of coal pillar driving and retaining roadway according to any one of claims 1 to 7, characterized in that: When applied to coal pillar driving: After the mining of the upper section working face is completed and the overburden roof collapses and stabilizes; Carry out excavation work in the lower section tunnel.

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