WO2024077841A1 - Stress transfer method and device for low-position roof cutting and high-position directional fracturing of gob-side entry retaining - Google Patents

Abstract

Disclosed in the present invention are a stress transfer method and device for low-position roof cutting and high-position directional fracturing of gob-side entry retaining. A low-position immediate roof is subjected to directional fracturing by a dense linear sleeve fracturing method and the like, so that the length of a lateral cantilever of the immediate roof is shortened, and the stress transfer from a gob roof to an entry retaining roof brought by hanging the immediate roof is weakened; a high-position main roof is subjected to fracturing by a directional fracturing method, so that the original gob roof stress transferred by the main roof is weakened, the load applied to entry retaining surrounding rock is reduced to the maximum extent from the source, and ultimately, the objectives of implementing immediate roof cutting entry retaining by low-position sleeve fracturing and implementing stress transfer by high-position directional fracturing of the main roof are achieved, thereby reducing the deformation of gob-side entry retaining surrounding rock. Also disclosed is a main machine-slidable drilling and fracturing all-in-one equipment, comprising: mounting a fracturing pump on a drilling machine travelling mechanism, and additionally providing a sliding rail to enable a main machine to slide forward and backward along the sliding rail. The consistency of inclination parameters for dense drilling of a low-position rock formation is ensured, and an eccentricity error is prevented from occurring and affecting the effect of entry retaining via roof cutting; moreover, the number of movements of a drilling machine is reduced, and the construction efficiency is improved.

Description

Stress transfer method and equipment for low-level top cutting and high-level directional fracturing along gob-side entry retention Technical Field

The invention relates to the field of coal mining, and in particular to a method and equipment for low-position top cutting and high-position directional fracturing stress transfer along gob-side lane retention.

Background technique

In order to maximize the recovery of coal resources and avoid resource waste, the method of leaving lanes along the goaf is often used to arrange the mining roadway to achieve coal pillar-free mining. According to the conventional method of cutting the top and leaving the roadway, although the cut direct roof can effectively fill the roadway wall, the overlying key rock layer has not been fractured near the side of the goaf area of the roadway. After mining, the old roof rotates and sinks, transferring the stress of the goaf area to the surrounding rock of the roadway, causing the surrounding rock of the roadway along the goaf to bear large additional stress, resulting in serious deformation of the roadway. Therefore, the key to controlling the surrounding rock of the roadway along the goaf is to cut off the direct roof above the roadway while cutting off the key rock layer above the roadway.

Traditional methods of top cutting and lane retention mainly include blasting top cutting pressure relief, hydraulic fracturing top cutting pressure relief, etc. The safety management of blasting top cutting pressure relief is complex. The large amount of harmful gases such as CO generated instantly by large-scale blasting has a huge impact on the ventilation safety management of mines. Especially for high-gas mines, blasting top cutting pressure relief is not suitable due to the hidden danger of blasting sparks inducing gas explosions. At the same time, explosive blasting has high economic costs, a small control range of a single blasting hole, and top cutting holes need to be densely arranged. Hydraulic fracturing is a fracturing technology that uses clean water as the fracturing fluid. Hydraulic fracturing is a continuous process of working on the rock mass. Therefore, compared with explosive blasting and _CO2 phase change fracturing, hydraulic fracturing has the characteristics of longer crack length and larger control range.

Casing fracturing is to apply tangential stress to the borehole wall by expanding the high-pressure rubber tube on the surface of the casing, and then fracturing the borehole. Compared with hydraulic fracturing, casing fracturing does not cause the loss of fracturing fluid, the power of the fracturing pump is relatively small, and it does not involve fluid-solid coupling, and the construction process is relatively simple. At the same time, multi-hole simultaneous fracturing can avoid uneven pressure distribution, which is conducive to cutting the top and retaining the lane. However, the expansion rate and expansion pressure of casing fracturing are limited, and it is not suitable for deep fracturing.

Traditional fracturing pumps are independent of the drilling rig, although some fracturing pumps are also equipped with crawlers or auxiliary Wheels are used for movement, but the overall movement of the fracturing pump is still difficult, which is not suitable for dynamic mobile top cutting construction. Traditional directional top cutting drills or anchor cable drills have poor construction accuracy, slow speed, and low automation. It is difficult to keep the same angle between adjacent holes, which makes subsequent top cutting more difficult; the drilling construction speed is slow and does not match the advancement speed of the working face; the labor intensity of workers is high and the construction efficiency is low.

Summary of the invention

In order to overcome the above-mentioned shortcomings of conventional top cutting and lane retention methods and traditional directional top cutting drilling rigs (or anchor cable drilling rigs), and combining the advantages of sleeve fracturing and hydraulic fracturing, a method and equipment for stress transfer of low-level top cutting and high-level directional fracturing along the empty lane retention is proposed. While cutting off the direct top above the lane, the key rock formation above the lane is cut off, so as to achieve the purpose of directional cutting and leaving the lane at the low-level direct top, and directional fracturing at the high-level old top to achieve the purpose of stress transfer and reduce the deformation of the surrounding rock of the empty lane retention. At the same time, a main engine sliding drilling and pressure integrated machine is proposed, including installing a fracturing pump on the drilling rig walking mechanism, and adding a slide rail so that the main engine can slide back and forth along the slide rail, to ensure the consistency of the inclination parameters of dense drilling holes in the low-level rock formation, avoid the generation of eccentricity errors that affect the effect of top cutting and lane retention, and greatly reduce the number of drilling rig movements, thereby improving construction efficiency. It can improve the automation level of directional top cutting equipment, the construction speed and construction effect of directional top cutting.

There is a thick key rock layer on the overlying part. According to the conventional method of cutting the roof and retaining the lane, after mining, the cut direct roof can effectively fill the lane wall, but the overlying key rock layer did not break near the top of the side of the lane goaf, but broke near the top of the side of the solid coal in the lane to form three key blocks A, B, and C. The key block B rotated and sank, transferring the stress of the goaf to the surrounding rock of the retained lane, causing the surrounding rock of the retained lane along the goaf to bear a large additional stress, resulting in serious deformation of the lane.

Based on the above reasons, the direct roof is fractured by directional fracturing such as the advanced dense linear sleeve fracturing method, the lateral cantilever length of the direct roof is shortened, and the stress transfer from the goaf roof to the remaining roadway roof caused by the direct roof suspension is weakened. After the rock formation in the cutting range collapses, the mining space can be better filled, avoiding the rapid pressure increase caused by the impact of the roof breakage, and slowing down the movement of the overlying rock formation. The directional fracturing method is used to fracture the high-position old roof of the roadway, so that the B key block among the three key blocks A, B, and C is fractured near the top of the goaf side of the roadway, weakening the original goaf roof stress transmitted by the old roof, and reducing the load applied to the surrounding rock of the roadway to the greatest extent from the source. At the same time, the three key blocks A, B, and C form a masonry beam structure, which is horizontally A, B, and C. The three key blocks B and C squeeze each other, thereby slowing down the sinking of the key block A, and thus maintaining the stress distribution of the roof of the gob-side retained roadway at a lower stress level. The low-position sleeve fracturing direct top and directional fracturing method are used to fracture the old top, so as to achieve the purpose of cutting down the roadway with the low-position sleeve fracturing direct top and achieving stress transfer with the high-position fracturing old top. The deformation of the surrounding rock of the gob-side retained roadway is transformed from "mutation type" to "slow change type", and the deformation of the surrounding rock is reduced.

Ordinary fracturing pumps and drilling rigs are two independent devices. Although some fracturing pumps are also equipped with crawlers or auxiliary wheels for movement, the overall movement of the fracturing pump is still difficult, which is not suitable for dynamic moving cutting construction. In addition, ordinary drilling rigs need to be moved as a whole every time a borehole is drilled. Although they will be readjusted before drilling the next borehole, due to the complex occurrence conditions of coal seams, the mining tunnels are generally excavated along the bottom of the coal seams, and the bottom of the tunnels are often uneven. Therefore, it is difficult to ensure the consistency of parameters such as the inclination angle of the low-level rock formations in the construction of a single borehole, and a group of boreholes have eccentric errors. The consistency of the drilling parameters of the low-level rock formation is the basis for direct top cutting and leaving the tunnels, especially the eccentricity error of the inclination angle between boreholes will affect the directional fracturing effect.

In order to solve the above two problems, the present invention patent proposes a main engine sliding drilling and pressure integrated machine. The design principle of the main engine sliding drilling and pressure integrated machine is to lengthen the traveling mechanism (crawler) of the drilling rig on the basis of the conventional drilling rig, install the fracturing pump on the traveling mechanism, and add a slide rail to the traveling mechanism, so that the main engine can slide back and forth on the traveling mechanism. The main engine sliding drilling and pressure integrated machine can realize the synchronous movement of the drilling rig and the fracturing pump, which is adapted to the dynamically moving cutting top construction. After the drilling construction is completed, the pipeline can be immediately connected to implement fracturing, thereby improving the construction efficiency. In addition, the main engine sliding drilling and pressure integrated machine can realize linear drilling by sliding the main engine, ensuring the consistency of drilling parameters in the same group of low-lying rock formations, and avoiding the eccentricity error of the inclination angle between boreholes affecting the directional fracturing effect.

The present invention provides a method for low-position top cutting and high-position directional fracturing stress transfer in gob-side entry retention, comprising the following steps:

Step 1: Install the fracturing pump on the traveling mechanism of the drilling rig, and install a slide rail on the traveling mechanism so that the main machine can slide forward and backward along the slide rail;

Step 2: Determine the low position according to the physical and mechanical properties of the low-level direct top rock layer, the confining pressure and the sleeve expansion force. The spacing of the boreholes in the rock formation;

Step 3: Determine the drilling spacing of the high-level rock formation according to the physical and mechanical properties of the high-level old top rock formation, the confining pressure, and the directional expansion range of the fracturing cracks;

Step 4: using the drilling rig to drill holes on the side of the trench working face, including a number of dense linear holes in low-level rock formations and holes in high-level rock formations;

Step 5, the low-level rock formation boreholes are divided into several groups, and then the dense linear sleeve fracturing method is used to carry out directionally fracturing on each group of low-level rock formation boreholes, so as to realize the dense linear sleeve fracturing of the low-level direct roof and the roof cutting and lane retaining; the lateral cantilever length of the direct roof is shortened, and the stress transfer from the goaf roof to the lane retaining roof caused by the direct roof hanging is weakened, and the rock formation within the cutting range can be better filled with the mining space after the collapse, so as to avoid the rapid pressure increase caused by the roof breakage impact, and slow down the movement of the overlying rock formation;

Step 6: Use directional fracturing method to carry out directional fracturing on each high-level rock formation borehole to achieve directional fracturing stress transfer of high-level old roof; weaken the stress of the original goaf roof transmitted by the old roof, and reduce the load applied to the tunnel surrounding rock to the greatest extent from the source, so as to maintain the stress distribution of the goaf-side retained roadway roof at a lower stress level;

Step 7: The low-level dense linear sleeve fracturing direct top and the high-level directional fracturing old top are constructed in coordination until all low-level and high-level rock formations are drilled and fractured, so that the low-level sleeve fracturing direct top is cut off to retain the roadway, and the high-level fracturing old top achieves the purpose of stress transfer; the deformation of the surrounding rock along the goaf is transformed from "sudden change type" to "slow change type", and the deformation of the surrounding rock is reduced.

Preferably, in step 2, the opening position of the low-level rock formation drilling hole is at the top plate 0.15m away from the side wall of the working face in the drift, the angle of the low-level rock formation drilling hole is 80°, and the final hole position of the low-level rock formation drilling hole is located on the upper surface of the direct top; the principle and method for determining the drilling hole spacing of the low-level rock formation: the drilling skeleton stress disturbance zones caused by the expansion force of the adjacent drilling sleeves in the low-level rock formation are superimposed on each other, thereby inducing expansion cracks to start and expand in the direction of the drilling line, forming a directional fracture surface, and realizing directional cutting of the top and leaving the lane. The cutting of the top and leaving the lane in the low-level rock formation has high requirements on the directional fracturing effect. The directional fracturing method needs to ensure that the straightness of the broken contour line of the left lane is good, which is convenient for later use. The drilling hole spacing of the low-level rock formation is mainly affected by factors such as the physical and mechanical properties of the low-level direct top rock formation, the confining pressure and the expansion force of the sleeve. The low-level rock formation is determined through laboratory tests and field tests. The spacing between rock formation drilling holes is 0.5 to 1.0 m.

Preferably, in step 3, the opening position of the high-level rock formation drilling hole is at the top plate 0.15m away from the side wall of the working face in the trench, the angle of the high-level rock formation drilling hole is 80°, and the terminal hole position of the high-level rock formation drilling hole is located at 2/3 to 3/4 of the thickness of the high-level rock formation. Principles and methods for determining the spacing of drilling holes in high-level rock formations: the directional fracturing cracks of adjacent boreholes in high-level rock formations can be extended and connected to form a through weak surface, cut off the high-level hard old top, and realize stress transfer. High-level rock formations have low requirements for the directional fracturing effect. Directional fracturing only needs to form a through fracture surface and cut off the high-level old top rock formation. There is no requirement for the straightness of the old top fracture contour line. The drilling spacing of high-level rock formations is mainly affected by factors such as the physical and mechanical properties of the high-level old top rock formation, the confining pressure and the directional expansion range of the cracks. The spacing of high-level rock formation drilling holes is determined to be 5 to 8m through laboratory tests and field tests.

Preferably, in step 4, the above-mentioned drilling machine is used to perform linear drilling, and the specific steps are:

(1) Slide the mainframe and drill rod of the drilling rig along the slide rail to the inner side of the slide rail, that is, the side close to the power source;

(2) drilling the first high-level rock formation borehole according to the borehole design parameters;

(3) When the drilling rig is stationary, slide the main machine and its drill rod along the slide rail to the outside of the slide rail for a distance a (the spacing of the low-position drilling holes) to drill the first low-position drilling hole;

(4) Then slide the main machine along the slide rail to the outside of the slide rail by a distance a (low-position drilling hole spacing) to drill the second drill hole;

(5) Similarly, complete the drilling of each group of low-level rock formation boreholes and high-level rock formation boreholes.

Preferably, the method of step 5 is as follows:

(1) According to the number of each group of low-level rock formation boreholes, the same number of high-pressure sealing installation rods are connected to the sleeve fracturing device, and each sleeve fracturing device is sent to the corresponding fracturing area near the corresponding low-level rock formation borehole opening, and then the high-pressure sealing installation rod is connected to the output high-pressure hose of the fracturing pump on the drilling rig through multiple three-way valves, and the high-pressure hose is provided with a pressure relief valve and a hydraulic fracturing measurement and control instrument;

(2) Turn on the fracturing pump and inject high-pressure water into the sleeve fracturing device through a high-pressure hose to perform dense linear multi-pore controlled sleeve directional fracturing;

(4) Using the staged forward fracturing method, the sleeve fracturator is advanced to the corresponding second stage fracturing zone, and the fracturing pump is used to re-fracturate until the multi-stage fracturing of each group of low-level rock formation boreholes is completed according to the design;

(5) Remove the sleeve fracturer and mounting rod.

Preferably, the method of step 6 is as follows:

(1) 3 to 5 high-position boreholes are grouped together, the same number of high-pressure sealing installation rods are connected to the sealers, each sealer is sent to the vicinity of 1/3 of the corresponding high-position rock formation borehole, and then each high-pressure sealing installation rod is connected to the output high-pressure hose of the fracturing pump on the drilling rig through multiple three-way valves; the high-pressure hose is provided with a pressure relief valve and a hydraulic fracturing measurement and control instrument;

(2) Turn on the fracturing pump and inject high-pressure water into the high-level rock formation borehole through a high-pressure hose to cause fracturing;

(3) Remove the hole sealer and mounting rod.

Preferably, when the thickness of the high-level rock formation is greater than 15 m, a packer is used in place of a hole sealer in step 3 to perform multiple fracturing operations.

Preferably, in step 5, the directional fracturing method for each group of low-lying rock formations adopts a dense linear porous controlled expansion screw type hydraulic pulling expansion fracturing method, and the specific steps are as follows:

(1) An expansion screw type hydraulic puller is placed in each group of low-level rock formation boreholes, and a pulling jack is installed at the outer end of the hole;

(2) connecting multiple expansion capsule water injection pipelines in parallel to the main pipeline of the fracturing pump;

(3) Turn on the fracturing pump, and use multiple pull-out jacks to cause the expansion screws to expand and squeeze the hole wall, causing the low-lying rock formation to fracture in a directional manner;

(4) Remove the expansion screw type hydraulic puller and the pulling jack.

Preferably, in step 5, the directional fracturing method for each group of low-lying rock formations adopts a dense linear porous controlled static expansion agent fracturing method, and the specific steps are as follows:

(1) Inject static expansion agent evenly mixed with water into each group of low-level rock formation boreholes simultaneously;

(2) Seal the drilled hole with a sealer;

(3) The static expansion agent gradually expands and squeezes the hole wall, causing directional fracture of the low-lying rock formation.

Preferably, in step 6, the high-level rock stratum directional fracturing method adopts a directional hydraulic fracturing method of pre-hydraulic slitting in the axial direction of the borehole, and the specific steps are as follows:

(1) In each high-level rock formation borehole, a hydraulic slotted drill bit is first used to slowly drill from the bottom of the hole outward. Withdraw the drill rod and use high-pressure water jet to form symmetrical axial pre-cutting slits in the axial direction of the borehole;

(2) withdraw the drill pipe and the hydraulic slotting drill bit, connect the high-pressure sealing installation rod with the hole sealer, send the hole sealer to the vicinity of 1/3 of the corresponding high-level rock formation borehole, and then connect the high-pressure sealing installation rod to the output high-pressure hose of the fracturing pump on the drilling rig through a three-way valve; the high-pressure hose is provided with a pressure relief valve and a hydraulic fracturing measurement and control instrument;

(3) Turn on the fracturing pump and inject high-pressure water into the high-level rock formation borehole through a high-pressure hose to perform pre-cut directional hydraulic fracturing;

(4) Turn off the high-pressure pump, remove the water pressure in the pipeline, and remove the hole sealer and high-pressure sealing mounting rod.

Preferably, in step 6, the high-level rock formation directional fracturing method adopts a directional hydraulic fracturing method of pre-mechanical grooving in the axial direction of the drilling hole, and the specific steps are as follows:

(1) In each high-level rock formation borehole, a mechanical slotting device is first used to form a symmetrical axial pre-slot in the borehole axial direction;

(2) withdraw the drill pipe and the mechanical slotting device, connect the high-pressure sealing installation rod with the hole sealer, send the hole sealer to the vicinity of 1/3 of the corresponding high-level rock formation borehole, and then connect the high-pressure sealing installation rod to the output high-pressure hose of the fracturing pump on the drilling rig through a three-way valve; the high-pressure hose is provided with a pressure relief valve and a hydraulic fracturing measurement and control instrument;

(3) Turn on the fracturing pump and inject high-pressure water into the high-level rock formation borehole through a high-pressure hose to perform pre-cut directional hydraulic fracturing;

(4) Turn off the high-pressure pump, remove the water pressure in the pipeline, and remove the hole sealer and high-pressure sealing mounting rod.

The present invention also provides a mainframe slidable drilling and pressure integrated machine, including a drilling rig provided with a walking device, wherein a fracturing pump and a drilling mainframe are provided at the upper end of the walking device, and the drilling mainframe can slide along the length direction of the walking device, and the drilling mainframe can drill holes on the side of the longitudinal working surface, and the left and right sliding length of the drilling mainframe on the walking device is greater than 2m, which is convenient for the construction of dense linear drilling.

Preferably, the drilling main unit is slidably connected to the traveling device via a slide rail device, the slide rail device includes a slide rail arranged on the traveling device, a pulley adapted to the slide rail is provided at the bottom of the drilling main unit, and the slide rail provides a drilling route for the drilling main unit to avoid eccentricity error in drilling.

The beneficial effects of the present invention are:

(1) Directed fracturing of the direct roof is carried out by means of advanced dense linear sleeve fracturing methods, etc., to shorten the lateral cantilever length of the direct roof, weaken the stress transfer from the goaf roof to the retained roadway roof caused by the direct roof suspension, and fill the mining space well after the rock formation collapses within the cutting range, thus avoiding the rapid pressure increase caused by the impact of roof breakage and slowing down the movement of the overlying rock formations;

(2) The directional fracturing method is used to fracture the high old roof of the tunnel, so that the key block B among the three key blocks A, B, and C is fractured near the top of the goaf side of the tunnel, which weakens the stress of the original goaf roof transmitted by the old roof and reduces the load applied to the tunnel surrounding rock to the greatest extent from the source. At the same time, the three key blocks A, B, and C form a masonry beam structure, and the three key blocks A, B, and C squeeze each other in the horizontal direction, thereby slowing down the sinking of the key block A.

(3) The dense linear sleeve fracturing direct top and directional fracturing methods are used to fracture the old top, so that the low-level sleeve fracturing direct top is cut off to retain the roadway, and the high-level directional fracturing old top is used to achieve the purpose of stress transfer. The deformation of the surrounding rock along the gob-retained roadway is transformed from "sudden change type" to "slow change type", and the deformation of the surrounding rock is reduced.

(4) A mainframe sliding drilling and pressure integrated machine is proposed. On the basis of a conventional drilling rig, the traveling mechanism (crawler) of the drilling rig is lengthened, the fracturing pump is installed on the traveling mechanism, and a slide rail is added to the traveling mechanism, so that the mainframe can slide back and forth on the traveling mechanism. The mainframe sliding drilling and pressure integrated machine can realize the synchronous movement of the drilling rig and the fracturing pump, which is adapted to the dynamically moving cutting top construction. After the drilling construction is completed, the pipeline can be immediately connected to implement fracturing, thereby improving the construction efficiency. In addition, the design of this drilling rig can realize linear drilling through the sliding mainframe. Linear drilling ensures the consistency of a group of low-level rock formation drilling parameters, avoids the influence of the eccentric error of the inclination angle between the boreholes on the directional fracturing effect, is conducive to the direct top being cut off and leaving the lane, and at the same time greatly reduces the number of movements of the drilling rig and improves the drilling efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in 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 only some embodiments of the present invention, and for ordinary technicians in this field, it is not necessary to pay attention to the drawings. On the premise of creative work, other drawings can be obtained based on these drawings.

FIG1 is a schematic diagram of cutting off the direct top without cutting off the old top provided by an embodiment of the present invention;

FIG2 is a schematic diagram of cutting off the direct top and cutting off the old top provided by an embodiment of the present invention;

FIG3 is a schematic diagram of the planar layout of low-level rock formation drilling holes and high-level rock formation drilling holes provided by an embodiment of the present invention;

Fig. 4 is a cross-sectional view of A-A in Fig. 3;

Fig. 5 is a cross-sectional view of B-B in Fig. 3;

FIG6 is a schematic diagram of the arrangement of a drilling host on a drilling rig provided by an embodiment of the present invention;

FIG7 is a schematic diagram of directional fracturing of a low top plate provided by an embodiment of the present invention;

FIG8 is a schematic diagram of directional fracturing of a high roof provided by an embodiment of the present invention (the thickness of the high roof is less than 15 m);

FIG9 is a schematic diagram of directional fracturing of a high roof provided in an embodiment of the present invention (the thickness of the high roof is greater than 15 m).

Among them: 1-A key block, 2-B key block, 3-C key block, 4-cut-off direct roof, 5-normal collapsed direct roof, 6-slope, 7-direct bottom, 8-coal wall of working face, 9-drilling hole in low-level rock formation, 10-drilling hole in high-level rock formation, 11-old roof, 12-direct roof, 13-coal seam, 14-drill pipe, 15-host machine, 16-fracturing pump, 17-power source, 18-control panel, 19-switch, 20-slide rail, 21-travel mechanism, 22-sleeve fracturing device, 23-hydraulic fracturing measuring and controlling instrument, 24-host machine slidable drilling and pressure integrated machine, 25-hole sealer, 26-packer, 27-vertical stress distribution of roof before artificial cutting off of old roof, 28-vertical stress distribution of roof after artificial cutting off of old roof.

Detailed ways

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

In the prior art, ordinary fracturing pumps and drilling rigs are two independent devices, although some fracturing pumps are also equipped with Tracks or auxiliary wheels are provided for movement, but the overall movement of the fracturing pump is still difficult, which is not suitable for the dynamic movement of the cutting top construction. In addition, the ordinary drilling rig needs to be moved once for each drilling hole. Although it will be readjusted before drilling the next hole, due to the complex occurrence conditions of the coal seam, the mining tunnel is generally excavated along the bottom plate of the coal seam, and the bottom plate of the tunnel is often uneven. Therefore, it is difficult to ensure the consistency of parameters such as the inclination angle of the low-level rock formation in the construction of a single drilling hole, and a group of drilling holes has eccentricity errors, etc.

The consistency of the parameters of the low-level rock formation drilling hole 9 is the basis for direct top cutting and leaving lanes, especially the eccentric error of the inclination angle between the boreholes will affect the directional fracturing effect. In order to solve the above two problems, referring to Figure 6, the patent of the present invention proposes a main engine sliding drilling and pressure integrated machine 24. The design principle of the main engine sliding drilling and pressure integrated machine 24 is to lengthen the running mechanism (crawler) of the drilling rig on the basis of the conventional drilling rig, install the fracturing pump on the running mechanism 21, and add a slide rail 20 to the running mechanism 21, so that the main engine 15 can slide back and forth on the running mechanism 21. The main engine sliding drilling and pressure integrated machine 24 can realize the synchronous movement of the drilling rig and the fracturing pump 16, which is adapted to the dynamically moving top cutting construction. After the drilling construction is completed, the pipeline can be immediately connected to implement fracturing, thereby improving the construction efficiency. In addition, the main engine sliding drilling and pressure integrated machine can realize linear drilling by sliding the main engine 15.

The steps of linear drilling of the main machine with sliding drilling and pressing machine are as follows:

(1) Turn on the switch 19 of the main unit that can slide the drilling and pressure machine, and operate the drilling machine 15 and the drill rod 14 of the drilling rig to slide along the slide rail 20 to the inner side of the slide rail (close to the power source 17) on the control console 18;

(2) drilling the first high-level rock formation borehole according to the borehole design parameters;

(3) When the drilling rig is stationary, slide the main machine 15 along the slide rail 20 to the outside of the slide rail by 0.5 m (the spacing of the low-level rock formation drilling holes) to drill the first low-level rock formation drilling hole;

(4) Then, the main machine 15 is slid along the slide rail 20 toward the outside of the slide rail by 0.5 m (the spacing of the low-level rock formation drilling holes) to drill the second low-level rock formation drilling hole;

(5) Similarly, complete the drilling of one high-level rock formation hole and a group of low-level rock formation holes.

The linear drilling constructed by the main machine's slidable drilling and pressure integrated machine ensures the consistency of parameters of a group of low-level rock formation drilling holes 9, avoids the influence of directional fracturing effect due to eccentric error of inclination angle between drilling holes, is conducive to cutting off the direct top 12 and leaving the lane, and at the same time greatly reduces the number of drilling rig movements and improves the drilling efficiency.

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

Embodiment 1, as shown in FIG. 1 to FIG. 9 , this embodiment provides a method for low-position top cutting and high-position directional fracturing stress transfer along gob-side entry retention,

See Figure 1. The average thickness of the coal seam 13 mined in a certain mine is 1.4m; the immediate roof 12 is 6.1m thick mudstone, the old roof 11 is 10m thick limestone, and the immediate bottom 7 is 4.5m thick sandstone. The sections of the two drifts of the working face are both rectangular, and the support method is a combination of anchor rods, anchor cables, and metal mesh support. Both drifts are excavated along the bottom plate; the specifications of the air intake and return air lanes are: width × height = 4.3 × 2.6m ² .

Referring to FIG1 , the coal seam 13 is covered by a thick key rock layer. According to the conventional method of cutting the top and retaining the lane, after mining, the normal collapse of the direct roof 5 far away from the lane-retaining area fully fills the goaf and supports the overlying roof rock layer. Although the direct roof 4 cut near the lane-retaining area can effectively fill the lane wall, the overlying key rock layer does not break near the top of the lane goaf side, but breaks near the top of the lane solid coal side to form three key blocks A, B, and C. The key block B 2 rotates and sinks, transferring the stress of the goaf to the surrounding rock of the lane, causing the surrounding rock of the lane along the goaf to bear a large additional stress 27, resulting in serious deformation of the lane.

Referring to FIG2 , for the above reasons, the direct roof 12 is fractured by the advanced dense linear sleeve fracturing technology, the lateral cantilever length of the direct roof 12 is shortened, and the stress transfer from the goaf roof to the roadway roof caused by the direct roof suspension is weakened. After the rock formation in the cutting range collapses, the mining space can be well filled, avoiding the rapid pressure increase caused by the impact of the roof breakage, and slowing down the movement of the overlying rock formation. The high-position old roof of the roadway is fractured by the directional fracturing method, so that the B key block 2 of the three key blocks A, B, and C is fractured near the top of the goaf side of the roadway, weakening the original goaf roof stress transmitted by the old roof 11, and reducing the load applied to the roadway surrounding rock to the greatest extent from the source. At the same time, the three key blocks A, B, and C form a masonry beam structure, and the three key blocks A, B, and C squeeze each other in the horizontal direction, thereby slowing down the sinking of the A key block 1, and then maintaining the stress distribution 28 of the roadway roof along the goaf at a lower stress level. Through the intensive linear sleeve fracturing direct roof 12 and directional fracturing method to fractur the old roof 11, the low-level sleeve fracturing direct roof 12 is cut off to retain the roadway, and the high-level fracturing old roof 11 is used to achieve the purpose of stress transfer. The surrounding rock deformation along the gob-retained roadway is transformed from "sudden change type" to "slow change type", and the surrounding rock deformation is reduced.

Therefore, the process of directional fracturing of the roof of the present invention can be summarized as arranging the top cutting drilling holes and implementing the drilling fracturing. The specific steps are as follows:

Step 1, referring to the drilling parameters set in FIG. 3, FIG. 4, and FIG. 5, two types of roof boreholes are drilled on the side of the working face of the chute by using the main slidable drilling and pressure integrated machine 24 to advance the working face coal wall 8, one is a low-level rock formation borehole 9, and the other is a high-level rock formation borehole 10. The opening position of the low-level rock formation borehole 9 is at the top plate 0.15m away from the side wall of the working face in the chute 6, the angle of the low-level rock formation borehole 9 is 80°, the spacing of the low-level rock formation borehole 9 is 0.5m, and the final hole position of the low-level rock formation borehole 9 is located on the upper surface of the direct roof 12. The opening position of the high-level rock formation borehole 10 is at the top plate 0.15m away from the side wall of the working face in the chute 6, the angle of the high-level rock formation borehole 10 is 80°, the spacing of the high-level rock formation borehole 10 is 5m, and the final hole position of the high-level rock formation borehole 10 is located at 2/3 of the thickness of the high-level rock formation.

Step 2, see step 7, divide every 4 to 6 low-level rock formation boreholes into a group, and use the sleeve fracturing device 22 to simultaneously fracture a group of low-level rock formation boreholes 9. The details are as follows:

(1) Connect 4 to 6 sets of high-pressure sealing installation rods to 4 to 6 sleeve fracturing devices 22, deliver the 4 to 6 sleeve fracturing devices 22 to the corresponding fracturing areas near the orifices of 4 to 6 low-level rock formation boreholes 9, and then connect the 4 to 6 sets of high-pressure sealing installation rods to a high-pressure hose connected to a fracturing pump 16 on a main slidable drilling and pressure integrated machine 24 through a plurality of three-way valves, wherein a pressure relief valve and a hydraulic fracturing monitoring and control instrument 23 are provided on the high-pressure hose;

(2) Turn on the fracturing pump 16 on the main slidable drilling and pressure machine 24, and inject high-pressure water into the sleeve fracturing device 22 through the pipeline to perform fracturing;

(3) Using staged forward fracturing, 4 to 6 sleeve fracturing devices 22 are pushed forward to the corresponding second stage fracturing zone, and the fracturing pump 16 on the main slidable drilling and pressure integrated machine 24 is used to re-fracturate until the multi-stage fracturing of this group of boreholes is completed according to the design;

(4) Remove the sleeve fracturing device 22 and the mounting rod.

Step 3, see FIG8 , divide every three high-level rock formation boreholes into a group, and use the “linear multi-hole controlled directional hydraulic fracturing method” to simultaneously fracture a group of high-level rock formation boreholes 10. The specific steps are as follows:

(1) Connect three sets of high-pressure sealing installation rods to three hole sealers 25, send the three hole sealers 25 to the vicinity of 1/3 of the three high-level rock formation boreholes 10, and then connect the three sets of high-pressure sealing installation rods through multiple tees. The valve is connected to a high-pressure hose connected to a fracturing pump 16 on a main slidable drilling and pressure-integrated machine 24; a pressure relief valve and a hydraulic fracturing monitoring and control instrument 23 are provided on the high-pressure hose;

(2) turning on the fracturing pump 16 on the main slidable drilling and pressure machine 24, and injecting high-pressure water into the borehole through the pipeline to cause fracturing;

(3) Take out the hole sealer 25 and the mounting rod.

Embodiment 2:

The average thickness of the coal seam 13 mined in a certain mine is 1.5m; the immediate roof 12 is 7m thick mudstone, the old roof 11 is 30m thick limestone, and the immediate bottom 7 is 5.5m thick sandstone. The sections of the two drifts 6 of the working face are both rectangular sections, and the support method is a combination of anchor rods, anchor cables, and metal mesh support. Both drifts are excavated along the bottom plate; the specifications of the air intake and return air lanes are: width × height = 4.3 × 2.4m ² .

Step 1, referring to the drilling parameters set in FIG. 3, FIG. 4, and FIG. 5, two types of roof boreholes are drilled on the side of the working face of the chute by using the main slidable drilling and pressure integrated machine 24 to advance the working face coal wall 8, one is a low-level rock formation borehole 9, and the other is a high-level rock formation borehole 10. The opening position of the low-level rock formation borehole 9 is at the top plate 0.15m away from the side wall of the working face in the chute 6, the angle of the low-level rock formation borehole 9 is 80°, the spacing of the low-level rock formation borehole 9 is 0.5m, and the final hole position of the low-level rock formation borehole 9 is located on the upper surface of the direct roof 12. The opening position of the high-level rock formation borehole 10 is at the top plate 0.15m away from the side wall of the working face in the chute 6, the angle of the high-level rock formation borehole 10 is 80°, the spacing of the high-level rock formation borehole 10 is 5m, and the final hole position of the high-level rock formation borehole 10 is located at 2/3 of the thickness of the high-level rock formation.

Step 2, referring to FIG. 7 , divide every 4 to 6 low-level rock formation boreholes 9 into a group, and use a sleeve fracturing device 22 to simultaneously fracture a group of low-level rock formation boreholes 9. The details are as follows:

(1) Connect 4 to 6 sets of high-pressure sealing installation rods to 4 to 6 sleeve fracturing devices 22, deliver the 4 to 6 sleeve fracturing devices 22 to the corresponding fracturing areas near the orifices of 4 to 6 low-level rock formation boreholes 9, and then connect the 4 to 6 sets of high-pressure sealing installation rods to a high-pressure hose connected to a fracturing pump 16 on a main slidable drilling and pressure integrated machine 24 through a plurality of three-way valves, wherein a pressure relief valve and a hydraulic fracturing monitoring and control instrument 23 are provided on the high-pressure hose;

(2) Turn on the fracturing pump 16 on the main slidable drilling and pressure machine 24, and inject high-pressure water into the sleeve fracturing device 22 through the pipeline to perform fracturing;

(3) Using staged forward fracturing, 4 to 6 sleeve fracturing devices 22 are pushed forward to the corresponding second stage fracturing zone, and the fracturing pump 16 on the main slidable drilling and pressure integrated machine 24 is used to re-fracturate until the multi-stage fracturing of this group of boreholes is completed according to the design;

(4) Remove the sleeve fracturing device 22 and the mounting rod.

Step 3, see FIG9 , divide every three high-level rock formation boreholes 10 into a group, and use the “linear multi-pore controlled hydraulic fracturing method” to simultaneously and multiple times fracture a group of high-level rock formation boreholes 10. The details are as follows:

(1) Connecting three sets of high-pressure sealing installation rods with three sets of packers 26, delivering the three packers 26 to corresponding fracturing zones near the bottom of three high-level rock formation boreholes 10, and then connecting the three sets of high-pressure sealing installation rods to a high-pressure hose connected to a fracturing pump 16 on a main slidable drilling and pressure integrated machine 24 through a plurality of three-way valves, and injecting high-pressure water into the three packers 26 using three sets of hand pressure pumps to expand the packers 26 and seal the holes; the high-pressure hose is provided with a pressure relief valve and a hydraulic fracturing monitoring and control instrument 23;

(2) Turn on the fracturing pump 16 on the main slidable drilling and pressure integrated machine 24, and inject high-pressure water into the three boreholes through the pipeline to cause fracturing;

(3) adopting staged retreat fracturing, retreating the three packers 26 to the corresponding second stage fracturing zone, and re-fracturing using the fracturing pump 16 on the main engine slidable drilling and pressure integrated machine 24, until the multi-stage fracturing of this group of boreholes is completed according to the design;

(4) Remove the packer 26 and the installation rod.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims (13)

1. A method for low-position top cutting and high-position directional fracturing stress transfer in gob-side entry retention, characterized in that it comprises the following steps:

   Step 1: Install the fracturing pump on the traveling mechanism of the drilling rig, and install a slide rail on the traveling mechanism so that the main machine can slide forward and backward along the slide rail;

   Step 2: Determine the drilling spacing of the low-level rock formation according to the physical and mechanical properties of the low-level direct top rock formation, the confining pressure and the sleeve expansion force;

   Step 3: Determine the drilling spacing of the high-level rock formation according to the physical and mechanical properties of the high-level old top rock formation, the confining pressure, and the directional expansion range of the fracturing cracks;

   Step 4: using the drilling rig to drill holes on the side of the trench working face, including a number of dense linear holes in low-level rock formations and holes in high-level rock formations;

   Step 5, the low-level rock formation boreholes are divided into several groups, and then the dense linear sleeve fracturing method is used to carry out directionally fracturing on each group of low-level rock formation boreholes, so as to realize the dense linear sleeve fracturing of the low-level direct roof and the roof cutting and lane retaining; the lateral cantilever length of the direct roof is shortened, and the stress transfer from the goaf roof to the lane retaining roof caused by the direct roof hanging is weakened, and the rock formation within the cutting range can be better filled with the mining space after the collapse, so as to avoid the rapid pressure increase caused by the roof breakage impact, and slow down the movement of the overlying rock formation;

   Step 6: Use directional fracturing method to carry out directional fracturing on each high-level rock formation borehole to achieve directional fracturing stress transfer of high-level old roof; weaken the stress of the original goaf roof transmitted by the old roof, and reduce the load applied to the tunnel surrounding rock to the greatest extent from the source, so as to maintain the stress distribution of the goaf-side retained roadway roof at a low stress level;

   Step 7: The low-level dense linear sleeve fracturing direct top and the high-level directional fracturing old top are constructed in coordination until all low-level and high-level rock formations are drilled and fractured, so that the low-level sleeve fracturing direct top is cut off to retain the roadway, and the high-level fracturing old top achieves the purpose of stress transfer; the deformation of the surrounding rock along the goaf is transformed from "sudden change type" to "slow change type", and the deformation of the surrounding rock is reduced.
2. The method for low-level top cutting and high-level directional fracturing stress transfer along gob-side entry retention as claimed in claim 1 is characterized in that: in step 2, the opening position of the low-level rock formation drilling hole is within the trench and the distance from the working face side At the roof 0.15m away from the wall, the angle of the low-level rock formation drilling is 80°, and the final hole position of the low-level rock formation drilling is located on the upper surface of the direct roof; the drilling spacing of the low-level rock formation is affected by the physical and mechanical properties of the low-level direct roof rock formation, the confining pressure and the expansion force of the casing, and the straightness of the broken contour line of the low-level roof, and the spacing of the low-level rock formation drilling is determined to be 0.5~1.0m; ensure that the straightness of the directional broken contour line along the goaf is good to facilitate later use.
3. A method for low-level top cutting and high-level directional fracturing stress transfer along the gob-retaining lane as described in claim 1, characterized in that: in step 3, the opening position of the high-level rock formation drilling hole is at the top plate 0.15m away from the side wall of the working face in the longitudinal groove, the angle of the high-level rock formation drilling hole is 80°, and the final hole position of the high-level rock formation drilling hole is located at 2/3 to 3/4 of the thickness of the high-level rock formation; the drilling spacing of the high-level rock formation is affected by the physical and mechanical properties of the high-level old top rock formation, the confining pressure and the directional expansion range of the cracks, and the spacing of the high-level rock formation drilling holes is determined to be 5 to 8m.
4. The method for low-position top cutting and high-position directional fracturing stress transfer along gob-side entry retention as claimed in claim 1 is characterized in that: in step 4, the above-mentioned drilling rig is used to perform linear drilling, and the specific steps are:

   (1) Slide the mainframe and drill rod of the drilling rig along the slide rail to the inner side of the slide rail, that is, the side close to the power source;

   (2) drilling the first high-level rock formation borehole according to the drilling design parameters;

   (3) When the drilling rig is stationary, slide the main machine and its drill rod along the slide rail to the outside of the slide rail for a distance a to drill the first low-position drill hole;

   (4) Then slide the main machine along the slide rail to the outside of the slide rail by a distance a to drill a second hole;

   (5) Similarly, complete the drilling of each group of low-level rock formation boreholes and high-level rock formation boreholes.
5. The method for low-position top cutting and high-position directional fracturing stress transfer along gob-side entry retention as claimed in claim 1 is characterized in that the method of step 5 is as follows:

   (1) According to the number of each group of low-level rock formation boreholes, the same number of high-pressure sealing installation rods are connected to the sleeve fracturing device, and each sleeve fracturing device is sent to the corresponding fracturing area near the corresponding low-level rock formation borehole opening, and then the high-pressure sealing installation rod is connected to the output high-pressure hose of the fracturing pump on the drilling rig through multiple three-way valves, and the high-pressure hose is provided with a pressure relief valve and a hydraulic fracturing measurement and control instrument;

   (2) Turn on the fracturing pump and inject high-pressure water into the casing fracturing device through the high-pressure hose to make a dense line. The porous sleeve controls directional fracturing;

   (3) Using staged forward fracturing, the sleeve fracturator is advanced to the corresponding second stage fracturing zone, and the fracturing pump is used to re-fracturate until the multi-stage fracturing of each group of low-level rock formation boreholes is completed according to the design;

   (4) Turn off the high-pressure pump, release the pipeline pressure, and remove the sleeve fracturing device and the high-pressure sealing mounting rod.
6. The method for low-level top cutting and high-level directional fracturing stress transfer along gob-side entry retention as claimed in claim 1 is characterized in that the high-level rock stratum directional fracturing method in step 6 adopts a linear porous controlled directional hydraulic fracturing method, and the specific steps are as follows:

   (1) 3 to 5 high-position boreholes are grouped together, the same number of high-pressure sealing installation rods are connected to the sealers, each sealer is sent to the vicinity of 1/3 of the corresponding high-position rock formation borehole, and then each high-pressure sealing installation rod is connected to the output high-pressure hose of the fracturing pump on the drilling rig through multiple three-way valves; the high-pressure hose is provided with a pressure relief valve and a hydraulic fracturing measurement and control instrument;

   (2) Turn on the fracturing pump and inject high-pressure water into the high-level rock formation borehole through a high-pressure hose to perform linear multi-pore controlled directional hydraulic fracturing;

   (3) Turn off the high-pressure pump, remove the water pressure in the pipeline, and remove the hole sealer and high-pressure sealing mounting rod.
7. The method for low-level top cutting and high-level directional fracturing stress transfer along the gob-retaining entry as described in claim 5 is characterized in that: when the thickness of the high-level rock formation is greater than 15m, a packer is used in step 3 instead of a hole sealer to perform multiple staged fracturing of the drilling.
8. The method for low-level top cutting and high-level directional fracturing stress transfer along gob-side entry retention as claimed in claim 1 is characterized in that: in step 5, the directional fracturing method for each group of low-level rock formations adopts a dense linear porous controlled expansion screw type hydraulic pulling expansion fracturing method, and the specific steps are as follows:

   (1) An expansion screw type hydraulic puller is placed in each group of low-level rock formation boreholes, and a pulling jack is installed at the outer end of the borehole;

   (2) connecting multiple expansion capsule water injection pipelines in parallel to the main pipeline of the fracturing pump;

   (3) Turn on the fracturing pump, and use multiple pull-out jacks to cause the expansion screws to expand and squeeze the hole wall, causing the low-lying rock formation to fracture in a directional manner;

   (4) Remove the expansion screw type hydraulic puller and the pulling jack.
9. The method for low-level top cutting and high-level directional fracturing stress transfer along gob-side entry retention as claimed in claim 1 is characterized in that: in step 5, the directional fracturing method for each group of low-level rock formations adopts a dense linear porous controlled static expansion agent fracturing method, and the specific steps are as follows:

   (1) Inject static expansion agent evenly mixed with water into each group of low-level rock formation boreholes simultaneously;

   (2) Seal the drilled hole with a sealer;

   (3) The static expansion agent gradually expands and squeezes the hole wall, causing directional fracture of the low-lying rock formation.
10. The method for low-level top cutting and high-level directional fracturing stress transfer along gob-side entry retention as claimed in claim 1 is characterized in that the high-level rock stratum directional fracturing method in step 6 adopts a directional hydraulic fracturing method of pre-hydraulic slitting in the axial direction of the borehole, and the specific steps are as follows:

    (1) In each high-level rock formation borehole, a hydraulic slotting drill bit is first used to slowly withdraw the drill rod from the bottom of the hole to the outside, and a high-pressure water jet is used to form a symmetrical axial pre-slot in the borehole axis;

    (2) withdraw the drill pipe and the hydraulic slotting drill bit, connect the high-pressure sealing installation rod with the hole sealer, send the hole sealer to the vicinity of 1/3 of the corresponding high-level rock formation borehole, and then connect the high-pressure sealing installation rod to the output high-pressure hose of the fracturing pump on the drilling rig through a three-way valve; the high-pressure hose is provided with a pressure relief valve and a hydraulic fracturing measurement and control instrument;

    (3) Turn on the fracturing pump and inject high-pressure water into the high-level rock formation borehole through a high-pressure hose to perform pre-cut directional hydraulic fracturing;

    (4) Turn off the high-pressure pump, remove the water pressure in the pipeline, and remove the hole sealer and high-pressure sealing mounting rod.
11. The method for low-level top cutting and high-level directional fracturing stress transfer along gob-side entry retention as claimed in claim 1 is characterized in that the high-level rock stratum directional fracturing method in step 6 adopts a directional hydraulic fracturing method of mechanically grooving the borehole axially in advance, and the specific steps are as follows:

    (1) In each high-level rock formation borehole, a mechanical slotting device is first used to form a symmetrical axial pre-slot in the borehole axial direction;

    (2) withdraw the drill pipe and the mechanical slotting device, connect the high-pressure sealing installation rod with the hole sealer, send the hole sealer to the corresponding high-level rock formation borehole near 1/3, and then connect the high-pressure sealing installation rod to the output high-pressure hose of the fracturing pump on the drilling rig through a three-way valve; the high-pressure hose is provided with a pressure relief valve and a hydraulic fracturing valve. Measuring and controlling instrument;

    (3) Turn on the fracturing pump and inject high-pressure water into the high-level rock formation borehole through a high-pressure hose to perform pre-cut directional hydraulic fracturing;

    (4) Turn off the high-pressure pump, remove the water pressure in the pipeline, and remove the hole sealer and high-pressure sealing mounting rod.
12. A low-level top cutting and high-level directional fracturing stress transfer equipment for gob-side tunnel retention - a mainframe slidable drilling and pressure integrated machine, characterized in that it includes a drilling rig with a traveling device, a fracturing pump and a mainframe are arranged on the upper end of the traveling device, the mainframe can slide along the length direction of the traveling device, the drilling mainframe can drill holes on the side of the longitudinal working face, and the left and right sliding length of the drilling mainframe on the traveling device is greater than 2m, which is convenient for the construction of dense linear drilling.
13. The low-level top cutting and high-level directional fracturing stress transfer equipment for gob-side entry retention as claimed in claim 12 - a main machine with a slidable drilling and pressure integrated machine, characterized in that:

    The main machine is slidably connected to the traveling device through a slide rail device, wherein the slide rail device comprises a slide rail arranged on the traveling device, and a pulley adapted to the slide rail is arranged at the bottom of the main machine, and the slide rail provides a moving route for the main machine to avoid eccentric errors in the same group of drilling holes.