Pre-excavated retracement channel stability high-position pressure relief and low-position support cooperative control method

Abstract

The embodiment of the invention provides a stability high-position pressure relief and low-position support cooperative control method for a pre-excavated retracement channel. The method comprises the steps that anchor rod and anchor cable support is adopted for a low-position rock stratum of the retracement channel in the initial excavation period; the high-position rock stratum of the withdrawing channel is subjected to pressure relief through hydraulic fracturing in the stable period; and the retracement channel is supported by adopting a stack type bracket in the through period. According to the pre-excavated retracement channel stability high-position pressure relief and low-position support cooperative control method disclosed by the embodiment of the invention, an anchor cable belt is adopted for a low-position rock stratum in an initial excavation period to enhance self-stabilization, hydraulic fracturing is adopted for realizing high-position pressure relief and low-position weakening in a stable period, and a high-resistance stack type bracket resists deformation in a cut-through period, so that scientific pressure relief is realized, and the stability of the pre-excavated retracement channel is improved. By means of the method, good stability of surrounding rock of the retracement channel is kept, roof cutting and frame pressing are avoided, the safety problem of pressure relief through a blasting means is avoided, safe and efficient retracement of the working face is guaranteed, mine productivity improvement is assisted, and the labor intensity of workers is greatly reduced.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the technical field of pre-excavation and withdrawal channels, and specifically relate to a method for coordinated control of high-position pressure relief and low-position support for stability of a pre-excavation and withdrawal channel. Background Art

[0002] At present, my country's coal mines usually use two technologies when moving the working face: the existing excavation and withdrawal channels and the pre-excavation and withdrawal channels. The existing excavation and withdrawal channel technology is a traditional method of moving the working face. It means that after the working face advances to the stop mining line, the hydraulic support stops moving forward, and the coal mining machine continues to advance to cut coal. After cutting coal, the roof is supported in time until enough space for equipment withdrawal is cut out. There are two problems with the existing excavation and withdrawal channel: one is that the working space is unsafe, the roof coal body in front of the support is generally more broken, and the safety of workers is difficult to effectively guarantee; the other is that the traditional moving technology is time-consuming and laborious, and the average moving time is 1 to 2 months. The pre-excavation and withdrawal channel is to pre-excavate one or more tunnels parallel to the mining working face at the stop mining line of the mining working face. It can be operated in parallel with coal mining, and there is no need to take up time to create a withdrawal space. At the same time, the excavation and support construction conditions of the pre-excavation and withdrawal channel are excellent, the support operation is convenient, the time is sufficient, and the support quality is high, which greatly reduces the difficulty of withdrawing the working face equipment and achieves the purpose of rapid relocation. The successful application of the pre-excavation withdrawal channel can improve the safety of the working face withdrawal space and significantly reduce the working face moving time, which can be shortened to within one week at the shortest. Compared with the traditional on-site excavation withdrawal channel technology, it can save more than 70% of the moving time and generate huge economic benefits. At present, the application scope of the pre-excavation withdrawal channel is rapidly expanding due to its significant economic and safety benefits.

[0003] However, since the pre-excavation withdrawal channel is different from the existing excavation withdrawal channel, it will be in an ultra-complex stress state during the final mining and finishing period of the working face. If it is not handled properly, it is easy to cause serious accidents such as roof collapse, pillar breakage, and support crushing, posing a serious safety threat to the finishing and moving work of the working face.

[0004] At present, the main control method is to significantly increase the strength of the internal support (combined support of high-strength anchor rods and anchor cables) and external support (pile-type supports, concrete columns, dense single pillars, etc.) of the pre-excavation and withdrawal channel. However, in many cases, even if strong support is used, the pre-excavation and withdrawal channel is still severely deformed during the final stage of the working face, resulting in phenomena such as crushing of supports, leakage of the roof, and strong bottom bulging, and the effect is limited. Summary of the invention

[0005] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a method for coordinated control of high-level pressure relief and low-level support for stability of a pre-excavation and withdrawal channel.

[0006] The present disclosure provides a method for coordinated control of high-position pressure relief and low-position support for stability of a pre-excavation and withdrawal channel, comprising:

[0007] In the initial excavation period, anchor rods and cables are used to support the low-lying rock formations in the withdrawal channel;

[0008] During the stable period, hydraulic fracturing is used to relieve pressure on high-level rock formations in the withdrawal channel;

[0009] During the breakthrough period, the withdrawal channel is supported by pile-type supports.

[0010] Furthermore, the method of using hydraulic fracturing to relieve pressure on high-level rock formations in the withdrawal channel during the stable period includes:

[0011] Obtain working face top plate parameters;

[0012] Designing hydraulic fracturing pressure relief parameters according to the working face roof parameters;

[0013] The withdrawal channel is depressurized at a high position according to the hydraulic fracturing depressurization parameters.

[0014] Furthermore, the working face roof parameters include at least roof rock layer thickness, roof rock layer lithology and roof rock layer mining height.

[0015] Furthermore, the hydraulic fracturing pressure relief parameters include the number of boreholes, the length of boreholes, the inclination of boreholes, the fracturing spacing and the number of fracturing times.

[0016] Furthermore, the high-position pressure relief of the withdrawal channel according to the hydraulic fracturing pressure relief parameters includes:

[0017] Drilling the top plate according to the number of holes, the length of holes and the inclination of holes;

[0018] Use a hole sealer to seal the hole;

[0019] According to the fracturing spacing and the fracturing times, hydraulic fracturing is performed on the borehole to perform high-level pressure relief on the withdrawal channel.

[0020] Further, the roof drilling is performed according to the number of holes, the length of holes and the inclination of holes, including:

[0021] If water comes out of the previous borehole, increase the distance between the next borehole and the previous one;

[0022] If no water emerges from the previous borehole, reduce the distance between the next borehole and the previous one.

[0023] Furthermore, the use of a hole sealer to seal the hole includes:

[0024] Push the hole sealer to the pre-crack position in the drilled hole;

[0025] A manual pump is used to pressurize the hole sealer. If water flows out of the borehole or the pressure drops, it is determined that the hole seal has failed and the pressurization is interrupted.

[0026] Further, the hydraulic fracturing of the borehole comprises:

[0027] Using a high-pressure water pump to continuously pressurize the hole sealer, if the pressure drops, it is determined that the pre-crack has cracked;

[0028] Keep the pressure and inject water until water comes out of the borehole, then stop pressurizing.

[0029] Furthermore, after the pressurization is stopped, the method further comprises:

[0030] Cut off the power supply to the high-pressure water pump first and then stop the water supply;

[0031] Drilling and draining water through water injection pipes;

[0032] After the pressure of the hole sealer is relieved, the hole sealer is withdrawn from the borehole.

[0033] Furthermore, it is characterized in that when hydraulic fracturing is used to relieve pressure on the high-level rock formation in the withdrawal channel, the method further comprises:

[0034] When the tunnel at the fracturing location is deformed or the anchor rod or anchor cable is broken, stop fracturing and adjust the fracturing method.

[0035] The disclosed embodiment provides a coordinated control method for high-level pressure relief and low-level support for the stability of a pre-excavation withdrawal channel. The method adopts anchor belts to enhance the self-stabilization of low-level rock strata in the initial excavation period, hydraulic fracturing in the stable period to achieve high-level pressure relief and low-level weakening, and high-resistance pile-type supports to resist deformation during the breakthrough period, thereby achieving scientific pressure relief, maintaining good stability of the surrounding rock of the withdrawal channel, avoiding top cutting and frame crushing, and avoiding the safety issues of pressure relief by blasting, ensuring safe and efficient withdrawal of the working face, helping to improve mine production capacity, and greatly reducing the labor intensity of workers. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of a method for coordinated control of high-position pressure relief and low-position support for stability of a pre-excavation and withdrawal channel according to an embodiment of the present disclosure;

[0037] Figure 2 This is a schematic diagram of a hydraulic fracturing process according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0038] At present, the support of the pre-excavation and withdrawal channel is mainly controlled by greatly improving the strength of the internal support (high-strength anchor bolt and cable combined support) and external support (pile-type support, concrete column, dense single pillar, etc.) of the pre-excavation and withdrawal channel. The above method solves the problem from the perspective of "hard resistance", and does not fundamentally reduce or transfer the stress accumulated in the surrounding rock of the pre-excavation and withdrawal channel. The key factor affecting the stability of the surrounding rock of the pre-excavation and withdrawal channel is that the advanced support pressure formed by the violent activity of the roof overburden structure during the final mining of the working face is transmitted to the surrounding rock of the pre-excavation and withdrawal channel of the working face, causing high stress instability. Therefore, the key to solving this problem should be "stress transfer", by changing the fracture position of the working face roof at the end of mining through artificial intervention, cutting off or weakening the concentration of the advanced support pressure on the surrounding rock of the pre-excavation and withdrawal channel of the working face, and improving the stress field environment of the surrounding rock of the pre-excavation and withdrawal channel of the working face, rather than simply adopting a strong support method.

[0039] In order to solve the above problems, an embodiment of the present disclosure provides a method for coordinated control of high-level pressure relief and low-level support for stability of a pre-excavation and withdrawal channel.

[0040] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0041] In addition, the described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the present disclosure.

[0042] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0043] It should be understood that although the terms first, second, third, etc. may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another component. Therefore, the first component discussed below can be referred to as the second component without departing from the teachings of the concepts of the present disclosure. As used in this disclosure, the term "and / or" includes any one of the associated listed items and all combinations of one or more.

[0044] Those skilled in the art will appreciate that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present disclosure, and therefore cannot be used to limit the protection scope of the present disclosure.

[0045] like Figure 1 As shown, an embodiment of the present disclosure provides a method for coordinated control of high-position pressure relief and low-position support for stability of a pre-excavation and withdrawal channel, the method comprising:

[0046] Step S1: during the initial excavation period, anchor rods and cables are used to support the low-lying rock formations in the withdrawal channel.

[0047] Specifically, the anchor holes are drilled row by row from the outside excavation working face. Each row of anchor holes can be constructed from the middle to the sides. At the same time, anchors are quickly installed in each anchor hole using anchoring agents. Then, anchor holes are drilled using an anchor drill. The anchor holes should be perpendicular to the roof or the tunnel contour line. At the same time, electric or pneumatic tensioning equipment is used to install anchors in each anchor hole. This forms a high-strength combined internal support for anchors and anchor cables in the low-lying rock formations during the initial excavation period.

[0048] Step S2: during the stable period, hydraulic fracturing is used to relieve pressure on the high rock formations in the withdrawal channel.

[0049] Specifically, the working face roof parameters are first obtained through exploration drilling, including the thickness, lithology and mining height of the roof rock layer. As an example, the coal seam where the working face of a certain project is located is the 3-1 coal seam, and the thickness of the coal seam varies slightly. The upper coal layer is 0.5m to 0.6m thick, the middle layer is 2.0m to 2.1m thick, the lower coal layer is 1.1m thick, and the total coal seam thickness is 3.6m to 3.8m. The hardness coefficient f = 0.34-0.53 is relatively small. The thickness of the 3-1 coal seam roof from bottom to top is 5.89m of sandy mudstone, 4.64m of fine sandstone, and 22.97m of sandy mudstone. There are a small amount of siltstone and coarse sandstone in some parts, and the rock composition of the roof is relatively complex. According to the results of the drilling rock mechanics test, the compressive strength of the roof rock layer is 9.6MPa to 23.6MPa, which belongs to a weak rock layer, and the softening coefficient is 0.15 to 0.79.

[0050] Then, according to the parameters of the working face roof, the hydraulic fracturing pressure relief parameters are designed. Hydraulic fracturing technology can effectively control the collapse of the working face roof, minimize the integrity of the roof, and make the working face roof collapse in layers in a timely manner. While hydraulic fracturing technology effectively controls the roof, it avoids affecting the normal recovery of the working face, avoids difficulties in maintaining the working face roof due to excessive fracturing and softening, avoids difficulties in roof management due to hydraulic fracturing, and avoids other possible disasters. Hydraulic fracturing pressure relief parameters include the number of drill holes, drill hole length, drill hole inclination, fracturing spacing, and fracturing times. Based on the above-mentioned parameters such as roof rock thickness, lithology, and mining height, the hydraulic fracturing pressure relief parameters are designed as follows:

[0051] 1) Fracturing drilling-S, drilling length 50m, inclination 50°, a total of 16 holes, one fracturing every 3m, and 13 fracturing times per hole;

[0052] 2) Fracturing borehole-L, the borehole length is 58m, the inclination is 30°, there are 14 holes in total, one fracturing is done every 3m, and each hole is fractured 15 times.

[0053] 3) Fracturing drilling-V, drilling length 50m, inclination 60°, a total of 11 holes, one fracturing every 3m, and 9 fracturing times per hole;

[0054] 4) Fracturing drilling-H, drilling length 40m, inclination 50°, 6 holes in total, one fracturing every 3m, 8 fracturing times per hole;

[0055] 5) The total length of S-hole, L-hole, V-hole and H-hole is 2402m. The angle between the S-hole and L-hole in the main withdrawal channel and the coal wall is 30°. The V-hole in the main withdrawal channel and the S-hole and L-hole in the two drifts are perpendicular to the coal wall. The angle between the H-hole in the auxiliary transport lane and the transport lane and the coal pillar of the lane is 5°, tending to the coal pillar side.

[0056] like Figure 2 As shown, finally, hydraulic fracturing high-position pressure relief is performed on the withdrawal channel according to the hydraulic fracturing pressure relief parameters designed above. Among them:

[0057] 1. According to the number of holes, length of holes and inclination angles designed above, a geological drill is used to drill holes in the top plate 21, and a backward fracturing method is used, i.e., fracturing is performed successively from the bottom of the hole to the hole mouth. The axis of the completed hole is required to be approximately a straight line, so it is required to reduce the drilling speed as much as possible during the drilling process, reduce the feed force of the drill, and ensure the linearity of the hole.

[0058] 2. Install the hole sealer 22 in the completed borehole, use the water injection steel pipe to push the straddle hole sealer 22 to the designated position in the corresponding borehole, that is, the pre-crack position, and use the water injection pump to seal the hole. The hole sealer partition section 221 must be a complete rock formation section. At this time, you can use a manual pump to connect the hole sealer 22 for pressurization, observe the borehole and monitor the pressure gauge to check whether the hole sealer can maintain pressure. If water flows out of the borehole or the pressure drops significantly, it means that the hole sealer has failed, then interrupt the pressurization, check the various connections of the hole sealer 22 and the hole sealer 22 itself, find and solve the problem, and ensure the normal operation of the hole sealer 22.

[0059] 3. According to the fracturing spacing and fracturing times designed above, use a high-pressure water pump 23 to connect the sealer 22 to hydraulically fractur the borehole. The high-pressure water pump 23 should first be powered by water and then powered on, and then slowly pressurized, while recording the data of the water pump pressure gauge 24, and continue to pressurize until the pre-cracks crack. At this time, the pressure will suddenly drop, and the pressure-maintaining water injection will continue to expand the cracks and soften the roof. If a large amount of water is observed to emerge from the borehole, the pressurization is stopped and the fracturing is ended. During the fracturing process, a certain amount of water injection time should be guaranteed to ensure sufficient fracturing and softening. At the same time, the roof around the fracturing hole should be checked, and the fracturing should be interrupted when a large amount of water flows out of the roof. The borehole that has completed hydraulic fracturing can be used as an observation hole for the next fracturing borehole. During the fracturing process, if water is observed to emerge from the borehole, the distance between the fracturing boreholes can be appropriately increased; if no water emerges, the distance between the fracturing boreholes needs to be appropriately reduced.

[0060] After the fracturing is completed, the high-pressure water pump 23 should be powered off first and then the water supply should be stopped. The water should be drained from the borehole through the water injection pipe 25. The draining time is usually 1.5 to 2 times the fracturing time. The sealer 22 can be depressurized after the water is completely drained. After the sealer 22 is depressurized, it exits the borehole, and the fracturing effect can be observed using a peep instrument. The above-mentioned drilling and fracturing operations can be carried out in parallel, and the operation spacing should be no less than 40m. In addition, during the hydraulic fracturing process, the conditions of the tunnels, anchor rods, and anchor cables at the fracturing site should be observed. When deformation or anchor rod (cable) breakage occurs, fracturing should be stopped immediately, and the fracturing method should be adjusted.

[0061] Step S3: During the penetration period, the withdrawal channel is supported by stack-type supports.

[0062] Specifically, first install the columns of the stacking support at the predetermined position in the withdrawal channel, then install the crossbeams of the stacking support on the columns, ensure that the columns of the support are vertical and stable, the crossbeams are horizontal and tightly connected, and finally use the connectors to fix the supports together to form an overall support structure. After the installation is completed, adjust and correct the support, and reinforce it if necessary to ensure that it meets the design requirements.

[0063] The disclosed embodiment provides a coordinated control method for high-level pressure relief and low-level support for the stability of a pre-excavation withdrawal channel. The method adopts anchor belts to enhance the self-stabilization of low-level rock strata in the initial excavation period, hydraulic fracturing in the stable period to achieve high-level pressure relief and low-level weakening, and high-resistance pile-type supports to resist deformation during the breakthrough period, thereby achieving scientific pressure relief, maintaining good stability of the surrounding rock of the withdrawal channel, avoiding top cutting and frame crushing, and avoiding the safety issues of pressure relief by blasting, ensuring safe and efficient withdrawal of the working face, helping to improve mine production capacity, and greatly reducing the labor intensity of workers.

[0064] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A method for coordinated control of high-level pressure relief and low-level support for stability of a pre-excavation and withdrawal channel, characterized in that: The method comprises: In the initial excavation period, anchor rods and cables are used to support the low-lying rock formations in the withdrawal channel; During the stable period, hydraulic fracturing is used to relieve pressure on high-level rock formations in the withdrawal channel; During the breakthrough period, the withdrawal channel is supported by pile-type supports.

2. The method according to claim 1, characterized in that The method of using hydraulic fracturing to relieve pressure on high-level rock formations in the withdrawal channel during the stable period includes: Obtain working face top plate parameters; Designing hydraulic fracturing pressure relief parameters according to the working face roof parameters; The withdrawal channel is depressurized at a high position according to the hydraulic fracturing depressurization parameters.

3. The method according to claim 2, characterized in that The working face roof parameters include at least the roof rock layer thickness, the roof rock layer lithology and the roof rock layer mining height.

4. The method according to claim 2, characterized in that: The hydraulic fracturing decompression parameters include the number of boreholes, the length of boreholes, the inclination of boreholes, the fracturing spacing and the number of fracturing times.

5. The method according to claim 4, characterized in that The step of performing high-position pressure relief on the withdrawal channel according to the hydraulic fracturing pressure relief parameters comprises: Drilling the top plate according to the number of holes, the length of holes and the inclination of holes; Use a hole sealer to seal the hole; According to the fracturing spacing and the fracturing times, hydraulic fracturing is performed on the borehole to perform high-level pressure relief on the withdrawal channel.

6. The method according to claim 5, characterized in that The method of drilling the top plate according to the number of holes, the length of holes and the inclination of holes comprises: If water comes out of the previous borehole, increase the distance between the next borehole and the previous one; If no water emerges from the previous borehole, reduce the distance between the next borehole and the previous one.

7. The method according to claim 5, characterized in that The method of sealing the hole using a hole sealer comprises: Push the hole sealer to the pre-crack position in the drilled hole; A manual pump is used to pressurize the hole sealer. If water flows out of the borehole or the pressure drops, it is determined that the hole seal has failed and the pressurization is interrupted.

8. The method according to claim 5, characterized in that The method of hydraulically fracturing the borehole comprises: Using a high-pressure water pump to continuously pressurize the hole sealer, if the pressure drops, it is determined that the pre-crack has cracked; Keep the pressure and inject water until water comes out of the borehole, then stop pressurizing.

9. The method according to claim 8, characterized in that After the pressurization is stopped, the method further comprises: Cut off the power supply to the high-pressure water pump first and then stop the water supply; Drilling and draining water through water injection pipes; After the pressure of the hole sealer is relieved, the hole sealer is withdrawn from the borehole.

10. The method according to any one of claims 1 to 9, characterized in that: When hydraulic fracturing is used to relieve pressure on the high-level rock formation in the withdrawal channel, the method further comprises: When the tunnel at the fracturing location is deformed or the anchor rod or anchor cable is broken, stop fracturing and adjust the fracturing method.

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