Gob-side entry retaining supporting method

Abstract

The invention discloses a gob-side entry retaining supporting method, which belongs to the technical field of roadway surrounding rock control, and comprises the following steps: arranging a supporting structure at a top plate position of a gob-side entry retaining, so that the rigidity of the top plate of the gob-side entry retaining is greater than that of a top plate on a gob side; a plurality of inclined top cutting holes are formed in the side portion, close to one side of the gob-side entry retaining, of the gob-side entry retaining, and the top cutting holes face a gob top plate and extend to the preset depth; blasting objects are arranged in the top cutting holes, the multiple top cutting holes are detonated in a segmented and delayed mode to form continuous presplitting gaps, and a goaf top plate close to the gob-side entry retaining area is guided to directionally collapse; a supporting frame is erected in the area below the top cutting hole in the gob-side entry retaining, and the two ends of the supporting frame abut against a top plate and a bottom plate of the gob-side entry retaining correspondingly to form a top plate support; and a sealing layer is laid with the supporting frame as a framework, so that sealing isolation of the gob-side entry retaining and the goaf is formed. The gob-side entry retaining sealing performance can be improved.

Description

Technical Field

[0001] This invention belongs to the field of tunnel surrounding rock control technology, and more specifically relates to a method for roadway support along the goaf. Background Technology

[0002] With the development of deep mining and high-intensity concentrated mining of coal resources, the technology of leaving roadways along the goaf has gradually become an important means to achieve pillarless mining and improve resource recovery rate.

[0003] Currently, the main methods used domestically and internationally are flexible concrete sealing and conventional shotcrete roadway reinforcement. Flexible concrete sealing involves spraying flexible concrete or polymer materials along the roadway to form a sealed layer, thus blocking air leakage channels in the goaf. This method is convenient to construct, but the sealing layer has high rigidity and poor coordination with surrounding rock deformation. It is prone to developing through cracks after secondary mining or roof movement, leading to seal failure. Conventional shotcrete roadway reinforcement uses mortar or gangue sprayed in conjunction with metal mesh to seal the roadway space, forming a single-layer rigid shell. This structure has good initial sealing performance, but because it does not consider the dynamic changes in roof movement and airflow channels, the sprayed layer often peels off and air leakage channels reappear in the later stages of working face advancement.

[0004] Therefore, how to provide a support method that can improve the sealing performance of the roadway along the goaf in the later stage is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for supporting roadways along the goaf, which can improve the sealing performance of roadways along the goaf.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for supporting roadways along the goaf includes:

[0008] Support structures are arranged at the top of the goaf-side roadway to make the stiffness of the top of the goaf-side roadway greater than that of the top of the goaf side.

[0009] Multiple inclined top-cutting holes are arranged on the side of the goaf-retaining roadway near the goaf area, with the top-cutting holes facing the top plate of the goaf area and extending to a predetermined depth;

[0010] Explosives are arranged in the cut-off holes, and multiple cut-off holes are detonated in stages with delayed detonation to form continuous pre-cracks and guide the directional collapse of the roof of the goaf near the goaf-side roadway area.

[0011] A support frame is erected in the area below the top cut hole in the goaf-side retaining lane. The two ends of the support frame abut against the top plate and bottom plate of the goaf-side retaining lane, respectively, to form a top plate support.

[0012] A sealing layer is laid using the support frame as a skeleton to form a sealed isolation between the goaf and the goaf.

[0013] Optionally, the inclination angle of the top-cutting hole is 10°–20°, and the spacing between the top-cutting holes is 0.4m–0.6m.

[0014] Optionally, the support frame includes a U-shaped steel bracket, and U-shaped steel leg recesses with a depth of 300±50mm and a spacing of 0.45m-0.6m are excavated in the goaf-retention tunnel, and the U-shaped steel bracket is erected at the U-shaped steel leg recesses.

[0015] Optionally, it also includes a flame-retardant layer, wherein a double-layer steel mesh is laid on the support frame, the flame-retardant layer is disposed between the double-layer steel mesh, and the sealing layer is disposed on the flame-retardant layer.

[0016] Optionally, the sealing layer is sprayed onto the flame-retardant layer. The sealing layer is sprayed in two stages: the initial spray is stopped when the thickness is 15mm-30mm, and the second spray is stopped when the designed thickness is reached.

[0017] Optionally, the grout used for the sealing layer is prepared by mixing cement, sand, gangue, and fly ash in a ratio of 1:1:2:1, with a water-cement ratio of 0.4-0.5.

[0018] Optionally, after the sealing layer is sprayed, a monitoring device and a gas injection device are installed in the goaf retainer. The monitoring device monitors the temperature, CO concentration and O2 concentration inside the goaf retainer in real time. When the CO concentration exceeds a set threshold and / or the O2 concentration exceeds a set threshold, the gas injection device injects inert gas until the CO and O2 concentrations are both below the set thresholds, and then stops injecting inert gas.

[0019] Optionally, when the CO concentration is greater than a set threshold and the O2 concentration is greater than a set threshold, and the duration exceeds a set threshold time, the gas injection device is turned on until the CO concentration is less than the set threshold and the O2 concentration is less than the set threshold, and then the gas injection device is turned off.

[0020] The above technical solution includes at least the following technical effects:

[0021] By supporting the roof with a support structure, the stability of the roof in the goaf-retaining area is improved, reducing the possibility of roof cracks in the goaf-retaining area during subsequent blasting. The blasting guides the directional collapse of the roof in the goaf area near the goaf-retaining area, forming a certain void range, thereby effectively reducing the impact of secondary mining or roof movement on the roof in the goaf-retaining area and reducing the probability of air leakage channels forming. The sealing layer and the support frame are used to block the air leakage channels, thereby achieving effective sealing of the goaf-retaining area. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 : This is a cross-sectional view of a goaf-keeping support method according to an embodiment of the present invention;

[0024] Figure 2 : This is a cross-sectional view of the support structure of a goaf retention support method according to an embodiment of the present invention;

[0025] Figure 3 : This is a logic diagram of a gas injection device for a goaf-retention support method in an embodiment of the present invention.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1. Goaf-side roadway; 2. Goaf area; 3. Support structure; 4. Top cutting hole; 5. Support frame; 6. Sealing layer; 61. First sealing layer; 62. Second sealing layer; 7. Reinforcing mesh; 8. Flame retardant layer; 9. Monitoring device. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0030] The following description, in conjunction with the accompanying drawings, details a method for roadway support along the goaf provided by the present invention through specific embodiments and application scenarios.

[0031] See appendix Figure 1—3. This invention provides a method for supporting roadways along the goaf, comprising:

[0032] A support structure 3 is arranged at the top of the goaf-retaining roadway 1 so that the stiffness of the top of the goaf-retaining roadway is greater than that of the top of the goaf side.

[0033] Optionally, the support structure 3 adopts anchor cables and steel strips, with three rows of constant resistance anchor cables arranged along the roadway axis in the roof. The anchor cable hole depth is 8.5-10.0m, the bottom section of the hole is enlarged by 300-700mm, and the hole diameter is 90-110mm; the anchor cable diameter is 20-22mm, and the tension force is ≥180kN.

[0034] A steel strip is installed between the anchor cables. The steel strip is reliably connected to the anchor cables through the anchor cable tray and locking device, so that the concentrated load of a single anchor cable can be distributed along the direction of the steel strip. This transforms the load on the top plate from a local point load to an overall line load, forming a stable top plate structure with overall load-bearing capacity.

[0035] The direction of the blast crack will preferentially extend to the weak side. The support structure 3 can form a stable zone with greater stiffness in the roof of the goaf-side roadway, making the stiffness of the roof of the goaf-side roadway 1 significantly greater than that of the goaf side. This provides a clear mechanical boundary for the extension of cracks to the goaf side during subsequent roof cutting blasting, thus avoiding damage to the roof of the roadway caused by blasting disturbance.

[0036] The length of the steel strip is customized according to the width of the tunnel. It is firmly connected to the anchor cable through locking devices to ensure that the tension of each row of anchor cables can be evenly transmitted to the steel strip to form an overall load-bearing structure.

[0037] Multiple inclined roof-cutting holes 4 are arranged on the side of the goaf 1 near the goaf 2, with the roof-cutting holes 4 facing the roof of the goaf 2 and extending to a predetermined depth.

[0038] The inclination angle of the top-cutting hole 4 is 10°–20°, the spacing of the top-cutting holes 4 is 0.4m–0.6m, and the depth of the top-cutting hole 4 is adapted to the thickness of the top plate and the lithology, with a value of 8m–10m. In order to protect the support structure, the top-cutting hole 4 should maintain a certain safe distance from the support structure 3. According to the actual situation, the safe distance should be greater than or equal to 0.6m.

[0039] Explosives are placed in the top-cutting hole 4, and multiple top-cutting holes 4 are detonated in stages with delayed detonation to form continuous pre-cracks and guide the directional collapse of the roof of the goaf 2 near the goaf-side roadway 1 area.

[0040] The top-cutting hole 4 employs a millisecond-level delayed sequential detonation to ensure that the blasting effect unfolds sequentially along the top-cutting line. After the first top-cutting hole 4 is detonated, initial cracks and stress release zones will form in the roof of the goaf side. When subsequent top-cutting holes 4 are detonated, their blast cracks, under the combined effect of stress wave superposition and crack propagation, preferentially trace and propagate to the crack areas already formed in the previous top-cutting hole 4. This process promotes the gradual connection of cracks between adjacent top-cutting holes 4, ultimately forming a continuous pre-cracked surface along the arrangement direction of the top-cutting holes 4.

[0041] By controlling the blasting parameters and blasting sequence through segmented delayed detonation, the superposition of instantaneous large energy can be avoided, thereby effectively regulating the height and range of roof collapse and ensuring that the collapse effect meets the design requirements of the goaf retaining roadway 1.

[0042] The blasting energy causes the roof of the goaf 2 to form a directional fracture surface along the cutting hole 4. After the pre-cracks are formed, the roof of the goaf 2 will collapse directionally along the pre-set crack surface under its own weight and the pressure of the overlying strata, thereby changing the stress distribution of the roof and causing the high stress area to shift to the depth of the goaf 2. This avoids the goaf roadway 1 being in a stress concentration area, thereby reducing the pressure on the roof of the roadway space and creating a stable stress environment for the goaf roadway 1.

[0043] Optionally, the explosive may be a shaped charge tube or a shaped charge cartridge.

[0044] A support frame 5 is erected in the area below the top cut hole 4 in the goaf sill 1. The two ends of the support frame 5 abut against the top plate and bottom plate of the goaf sill 1 respectively to form a top plate support.

[0045] A sealing layer 6 is laid with the support frame 5 as the skeleton to form a sealed isolation between the goaf 1 and the goaf 2.

[0046] The combination of the support frame 5 below the top cut hole 4 and the sealing layer 6 not only further reinforces the roof through rigid support, but also achieves effective sealing and isolation between the roadway and the goaf 2, preventing harmful gases such as gas and dust and gangue from entering the goaf 2, and significantly improving the safety and stability of the roadway 1 along the goaf.

[0047] In this embodiment, specifically, the support frame 5 includes a U-shaped steel support. U-shaped steel leg recesses with a depth of 300±50mm and a spacing of 0.45m-0.6m are excavated in the goaf chute 1, and the U-shaped steel support is erected at the U-shaped steel leg recesses.

[0048] Alternatively, the top of the U-shaped steel support can be connected to the top plate anchor cable tray or steel strip via wire rope, chain or special connecting ring, using a flexible connection method to form a combined support system with the support structure 3.

[0049] In this embodiment, specifically, it also includes a flame-retardant layer 8, a double-layer steel mesh 7 is laid on the support frame 5, the flame-retardant layer 8 is disposed between the double-layer steel mesh 7, and the sealing layer 6 is disposed on the flame-retardant layer 8.

[0050] The sealing layer 6, together with the flame-retardant layer 8 and the double-layer steel mesh 7, not only enhances the overall support strength and deformation resistance of the goaf-side retainer 1, but also endows the sealing structure with good flame-retardant properties. It can effectively prevent gas, dust and harmful gases in the goaf 2 from penetrating into the retainer, while preventing airflow in the retainer from entering the goaf 2 and causing spontaneous combustion hazards. This further enhances the safety and reliability of the retainer and provides a strong guarantee for the long-term stable use of the goaf-side retainer 1.

[0051] In this embodiment, specifically, the sealing layer 6 is sprayed onto the flame-retardant layer 8. The sealing layer 6 is sprayed in two stages. The first stage is sprayed to a thickness of 15mm-30mm to form the first sealing layer 61. The second stage is sprayed to the designed thickness to form the second sealing layer 62, with a designed thickness of 80-120mm.

[0052] This two-stage spraying method effectively ensures the forming quality and overall sealing performance of the sealing layer 6. The initial spraying primarily serves to quickly seal and fix the reinforcing mesh 7 and the flame-retardant layer 8, ensuring the stability of the base layer and laying a good foundation for the second spraying. It avoids defects such as coating flow, peeling, or internal bubbles and voids caused by excessive thickness in a single spraying. The second spraying is carried out after the initial spraying layer has reached a certain strength. By precisely controlling the amount and thickness of the spray, the sealing layer 6 achieves the structural strength and sealing performance required by the design. It effectively blocks the airflow channel between the goaf 1 and the goaf 2, avoiding safety hazards such as gas accumulation and spontaneous combustion caused by air leakage. At the same time, it enhances the integrity and deformation resistance of the support system, ensuring the stability of the long-term sealing effect.

[0053] In this embodiment, specifically, the grout material for the sealing layer 6 is mixed with cement: sand: gangue blocks: fly ash = 1:1:2:1, and the water-cement ratio is 0.4-0.5.

[0054] In this embodiment, specifically, after the sealing layer 6 is sprayed, a monitoring device 9 and a gas injection device are installed inside the goaf chute 1. The monitoring device 9 monitors the CO concentration and O2 concentration inside the goaf chute 1 in real time. When the CO concentration exceeds the set threshold and / or the O2 concentration exceeds the set threshold, the gas injection device injects inert gas until the CO and O2 concentrations are both below the set threshold, and then stops injecting inert gas.

[0055] Optionally, a monitoring device 9 is installed every 25-40m in the roadway section, and nitrogen is injected by the gas injection device.

[0056] This real-time monitoring and inert gas injection linkage safety mechanism enables dynamic monitoring and timely intervention of the gas environment within the goaf retainer 1. The injected inert gas rapidly dilutes the oxygen concentration in the goaf 2, inhibiting oxidation reactions and reducing the concentration of harmful gases, thereby effectively preventing the occurrence or escalation of spontaneous combustion accidents. By precisely setting the threshold conditions for starting and stopping the injection, and by rationally arranging the spacing of the monitoring devices 9, the comprehensiveness of monitoring and the timeliness of intervention can be ensured, further improving the safety level of the working environment in the goaf retainer 1.

[0057] In this embodiment, specifically, when the CO concentration is greater than a set threshold and the O2 concentration is greater than a set threshold, and the duration exceeds the set threshold time, the gas injection device is turned on, and the gas injection device is turned off after the CO concentration is less than the set threshold and the O2 concentration is less than the set threshold.

[0058] Setting a duration gives the gas injection device a hysteresis effect, which can avoid frequent start-up and shutdown of the gas injection device, prevent false triggering caused by instantaneous fluctuations or monitoring errors, reduce unnecessary gas consumption and equipment wear, and ensure the economy and stability of system operation.

[0059] The specific threshold parameter is CO concentration 100-300×10⁻ 6 The O2 content is 9%–12%, the duration is 10–30 min, and the injection flow rate of the gas injection device is 300–800 m³ / h.

[0060] Optionally, the monitoring device 9 also includes a temperature monitor. After the gas injection device is started, not only must the CO concentration be less than the set threshold and the O2 concentration be less than the set threshold, but the temperature along the goaf 1 must also stop increasing before the gas injection device can be shut down.

[0061] In one embodiment, the specific support method is as follows:

[0062] First, surveying and setting out were conducted within the working face roadway to determine the locations for reinforced support. Roof anchor cable holes were drilled using an MQT-120 anchor drill rig, with a hole depth of 9.3 meters. An MS-SY45 / 95 type borehole expander was used to enlarge the hole by 500 mm at the bottom, resulting in a hole diameter of 95 mm. When installing Φ21.6 mm anchor cables, four rolls of MSZ2550 medium-speed anchoring agent were used per hole. The anchor cable tray was tightly fitted to the W-shaped steel strip, and the tension was increased to over 200 kN.

[0063] A pneumatic rock drill was used to drill the top-cutting hole 4, with a hole spacing of 0.5 meters and an inclination angle of 15° towards the goaf 2. After the two-way shaped charge blasting tubes were installed, digital electronic detonators were used for segmented detonation.

[0064] First, construct 300 mm deep U-shaped steel leg recesses, then erect U-shaped steel supports at 0.5 m intervals. The top of the U-shaped steel supports is connected and fixed to the top plate anchor cable with iron chains. Then, lay double-layer steel mesh 7 and sandwich flame-retardant airtight cloth in the middle.

[0065] The shotcrete operation uses a ZP-5B shotcrete machine, and is sprayed twice to a total thickness of 100 mm. The first spray is a 20 mm initial layer for sealing, and the second spray is a final layer to the designed thickness of 100 mm. The shotcrete material is mixed on-site with the following ratio: cement: sand: gangue: fly ash = 1:1:2:1.

[0066] A set of monitoring sensors is set up every 30 meters in the roadway section to collect gas samples in real time to monitor CO and O2 concentrations. When both CO and O2 concentrations exceed the set threshold and remain above the threshold for more than 10 minutes, the gas injection device is activated to inject nitrogen until both CO and O2 concentrations drop below the set threshold.

[0067] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other modifications under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these modifications are within the protection scope of the present invention.

Claims

1. A method for supporting roadways along the goaf, characterized in that, include: Support structures are arranged at the top of the goaf-side roadway to make the stiffness of the top of the goaf-side roadway greater than that of the top of the goaf side. Multiple inclined top-cutting holes are arranged on the side of the goaf-retaining roadway near the goaf area, with the top-cutting holes facing the top plate of the goaf area and extending to a predetermined depth; Explosives are arranged in the cut-off holes, and multiple cut-off holes are detonated in stages with delayed detonation to form continuous pre-cracks and guide the directional collapse of the roof of the goaf near the goaf-side roadway area. A support frame is erected in the area below the top cut hole in the goaf-side retaining lane. The two ends of the support frame abut against the top plate and bottom plate of the goaf-side retaining lane, respectively, to form a top plate support. A sealing layer is laid using the support frame as a skeleton to form a sealed isolation between the goaf and the goaf.

2. The method for roadway support along the goaf according to claim 1, characterized in that, The inclination angle of the top-cutting hole is 10°–20°, and the spacing between the top-cutting holes is 0.4m–0.6m.

3. The method for roadway support along the goaf according to claim 1, characterized in that, The support frame includes a U-shaped steel support, and U-shaped steel leg recesses with a depth of 300±50mm and a spacing of 0.45m-0.6m are excavated in the goaf-retention tunnel, and the U-shaped steel support is erected at the U-shaped steel leg recesses.

4. The method for roadway support along the goaf according to claim 1, characterized in that, It also includes a flame-retardant layer, with a double-layer steel mesh laid on the support frame, the flame-retardant layer disposed between the double-layer steel mesh, and the sealing layer disposed on the flame-retardant layer.

5. The method for roadway support along the goaf according to claim 4, characterized in that, The sealing layer is sprayed onto the flame-retardant layer. The sealing layer is sprayed in two stages: the initial spray is stopped when the thickness is 15mm-30mm, and the second spray is stopped when the thickness is reached to the design thickness.

6. The method for roadway support along the goaf according to claim 5, characterized in that, The grout used for the sealing layer is prepared by mixing cement, sand, gangue, and fly ash in a ratio of 1:1:2:1, with a water-cement ratio of 0.4-0.

5.

7. The method for roadway support along the goaf according to claim 1, characterized in that, After the sealing layer is sprayed, a monitoring device and a gas injection device are installed in the goaf retainer. The monitoring device monitors the CO and O2 concentrations inside the goaf retainer in real time. When the CO concentration exceeds a set threshold and / or the O2 concentration exceeds a set threshold, the gas injection device injects inert gas until both the CO and O2 concentrations are below the set thresholds, and then stops injecting inert gas.

8. A method for supporting a roadway along the goaf according to claim 7, characterized in that, When the CO concentration is greater than a set threshold and the O2 concentration is greater than a set threshold, and the duration exceeds the set threshold time, the gas injection device is turned on until the CO concentration is less than the set threshold and the O2 concentration is less than the set threshold, then the gas injection device is turned off.

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