A combined drilling and slitting method for pressure relief

Abstract

The application relates to the technical field of coal mine rock burst prevention and treatment, and provides a composite pressure relief method combining drilling and slotting, which comprises the following steps: obtaining geological conditions and stress conditions of a target roadway; determining a time sequence relationship and a spatial arrangement mode of drilling pressure relief and mechanical slotting pressure relief according to the geological conditions and the stress conditions, wherein the time sequence relationship comprises an operation sequence of drilling first and slotting later, slotting first and drilling later or drilling and slotting alternately, and the spatial arrangement mode comprises arrangement angle and spacing parameters; and performing drilling operation and mechanical slotting operation according to the time sequence relationship and the spatial arrangement mode, so that drilling and mechanical slotting form a coupled pressure relief structure in space. The application realizes accurate coupling of holes and slots in time and space, constructs a point-line-surface three-dimensional pressure relief system, and improves pressure relief efficiency and safety.

Description

Technical Field

[0001] This invention belongs to the field of coal mine rockburst prevention technology, and provides a composite pressure relief method that combines drilling and slotting. Background Technology

[0002] Rockbursts are a serious dynamic disaster during deep coal mining, and floor pressure relief is a key technical means to prevent and control them. Currently, commonly used floor pressure relief techniques mainly include drilling pressure relief, blasting pressure relief, excavator trenching pressure relief, and mechanical slotting pressure relief.

[0003] In existing technologies, to overcome the limitations of a single pressure relief method, multiple methods are often combined, such as a "blasting + excavation" composite method or a "hydraulic slotting + directional blasting" top-cutting pressure relief method, attempting to enhance the pressure relief effect through the superposition of different processes. However, existing composite pressure relief processes often involve simply splicing together or combining two methods in a fixed pattern, making it difficult to form an effective spatiotemporal coupling relationship between drilling and slotting. This not only fails to fully utilize the synergistic effect of "point-like release" and "linear blocking," but may also induce local stress concentration or even dynamic manifestation due to improper construction sequence or unreasonable spatial arrangement, resulting in technical problems such as low pressure relief efficiency, high safety risks, and difficulty in accurately controlling the direction of stress release. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a composite pressure relief method that combines drilling and slit cutting, enabling dynamic matching of the timing and spatial arrangement of boreholes and slits according to site conditions, and constructing a point-line-plane coupled three-dimensional pressure relief system.

[0005] The technical solution of this invention includes: obtaining the geological conditions, cross-sectional parameters, and stress conditions of the target roadway, wherein the geological conditions include the thickness of the bottom coal and the hardness of the coal body, and the stress conditions include the impact hazard level and the degree of stress concentration; determining the temporal relationship and spatial arrangement pattern of borehole pressure relief and mechanical slotting pressure relief based on the geological conditions and the stress conditions, wherein the temporal relationship includes the operation sequence of drilling before cutting, cutting before drilling, or alternating drilling and cutting, and the spatial arrangement pattern includes the arrangement angle and spacing parameters between the borehole and the slot; and performing borehole operation and mechanical slotting operation according to the temporal relationship and the spatial arrangement pattern, so that the borehole and the mechanical slotting form a coupled pressure relief structure in space.

[0006] The above scheme changes the blindness of traditional fixed composite construction by establishing a mapping relationship between geological stress conditions and pressure relief mode. It enables the point-like deep release of boreholes and the linear continuous blocking of mechanical cutting to achieve precise coupling in the spatiotemporal dimension, thereby maximizing the pressure relief efficiency while ensuring construction safety.

[0007] Optionally, determining the timing relationship between borehole pressure relief and mechanical slotting pressure relief includes: when the thickness of the bottom coal is greater than the effective depth of the mechanical slotting, the impact hazard level is medium or above, or direct mechanical slotting poses a risk of excessive equipment load and power manifestation, the timing relationship is determined to be a drill-then-slotting mode; when directional protection and stress transmission control are required, the timing relationship is determined to be a slotting-then-drilling mode; when the impact hazard level is high, or the effect of single borehole pressure relief or single mechanical slotting pressure relief fails to meet the preset pressure relief target, the timing relationship is determined to be a drilling-slotting alternating mode.

[0008] Optionally, when the timing relationship is the drill-then-cut mode, the drilling and mechanical cutting operations are performed according to the timing relationship and the spatial arrangement mode, so that the drilling and mechanical cutting form a coupled pressure relief structure in space. This includes: firstly, pressure relief boreholes are constructed on the roadway floor. The diameter of the pressure relief boreholes is 90 to 150 mm, the depth is 3.0 to 5.0 m, and the spacing is 1 to 5 m. The pressure relief boreholes are used to release local stress and serve as guide holes for subsequent mechanical cutting. After the pressure relief boreholes are constructed, chain mechanical cutting is performed between adjacent pressure relief boreholes or on the line connecting the pressure relief boreholes. The depth of the chain mechanical cutting is 1.0 to 2.5 m, the width of the chain mechanical cutting is greater than or equal to 200 mm, and the length of the chain mechanical cutting extends through the entire pressure relief zone. The pressure relief boreholes and the chain mechanical cutting together form a point-line combined pressure relief system.

[0009] Optionally, when the timing relationship is the "cut-then-drill" mode, the drilling and mechanical cutting operations are performed according to the timing relationship and the spatial arrangement mode to form a coupled pressure relief structure in space. This includes: firstly, constructing a chain-type mechanical cut on the roadway floor to cut off the stress transmission path and form a stress blocking surface; the depth of the chain-type mechanical cut is 1.0 to 2.5 m, and the width of the chain-type mechanical cut is greater than or equal to 200 mm; after the chain-type mechanical cut is completed, pressure relief boreholes are arranged on one or both sides of the chain-type mechanical cut according to the protected object and the location of the high-stress area; the pressure relief boreholes are arranged on the high-stress side facing away from the protected object or in the residual stress concentration area at the edge of the chain-type mechanical cut; the depth of the pressure relief boreholes is 3.0 to 5.0 m, and the angle with the plane of the chain-type mechanical cut is 45 to 90°; the pressure relief boreholes are arranged symmetrically or staggeredly to form a slot-hole cooperative pressure relief structure.

[0010] Optionally, when the timing relationship is the drilling-cutting alternation mode, the step of performing drilling and mechanical cutting operations according to the timing relationship and the spatial arrangement mode, so that the drilling and mechanical cutting form a coupled pressure relief structure in space, includes: performing a first round of pressure relief: constructing shallow holes and / or small-diameter holes to perform preliminary stress relief, and constructing shallow cuttings in the area of ​​the shallow holes and / or small-diameter holes to expand the pressure relief range; based on the effect verification results of the first round of pressure relief, performing a second round of pressure relief: constructing deep holes and / or large-diameter holes to release deep or residual high stress, and constructing deep cuttings, wherein the deep cuttings and the shallow cuttings form a continuous groove; and performing multiple rounds of drilling-cutting alternation according to the preset pressure relief target until the preset pressure relief target is achieved.

[0011] Optionally, the spatial arrangement pattern further includes the spatial relative positional relationship between the borehole and the mechanical cut. The spatial relative positional relationship is determined according to the coupling purpose, which includes: when the borehole is used to provide guidance for the mechanical cut, the spatial relative positional relationship is that the mechanical cut line is located on the line connecting adjacent boreholes or close to the borehole axis; when the mechanical cut is used as a stress-blocking surface, the spatial relative positional relationship is that the borehole and the mechanical cut are arranged perpendicularly or obliquely; when the borehole is used to expand the pressure relief range of the mechanical cut, the spatial relative positional relationship is that the borehole and the mechanical cut are arranged parallel to each other, and the distance between the borehole and the mechanical cut is determined according to the pressure relief influence range.

[0012] Optionally, the arrangement of the spatial relative positions includes: symmetrical arrangement: with the mechanical cut as the center line, boreholes are arranged at the same distance on both sides of the mechanical cut, and the boreholes on the left and right sides correspond to the same mileage position in the direction of the roadway; staggered arrangement: the boreholes on both sides of the mechanical cut are staggered by 0.5 hole spacings along the direction of the roadway; wherein, the time interval between the boreholes and the mechanical cut is within the same shift to 24 hours, and the spatial distance between the boreholes and the mechanical cut is 1 to 3 meters.

[0013] Optionally, during the drilling operation, the amount of drill cuttings, drilling speed, drilling rig current or torque, and power display parameters are monitored in real time to determine the stress state of the coal body. When the amount of drill cuttings increases compared to the reference value, the drilling speed decreases by more than 30%, the drilling rig current or torque continues to increase by more than 20%, or abnormalities such as stuck drill, blowout, or coal blasting occur, the current location is determined to be a high-stress zone. For the high-stress zone, according to the three causes of unrelieved pressure between holes, unrelieved pressure at depth, and localized stress concentration, measures such as reducing hole spacing or adding holes, increasing hole depth or adjusting hole angle, and increasing hole diameter or increasing the number of hole rows are taken to adjust the parameters.

[0014] Optionally, after all drilling and mechanical slit cutting operations are completed, a drilling-cutting coupling effect test is performed. This test includes stress field distribution testing, pressure relief range testing, borehole-mechanical slit connectivity testing, and roadway deformation control effect testing. If the test results do not meet preset requirements, parameter optimization is performed. This optimization includes: if the stress reduction rate is insufficient, increasing the borehole depth or diameter, decreasing the borehole spacing, or increasing the mechanical slit depth; if the pressure relief range is discontinuous, adjusting the relationship between the mechanical slit line and the borehole connection line, decreasing the borehole spacing, or the mechanical slit spacing; if the stress on the side of a specific protected object increases, changing the borehole layout, adjusting the borehole angle, or first forming the mechanical slit blocking surface; the optimized parameters are then re-tested and confirmed, and after confirmation of compliance, they are incorporated into the subsequent construction plan.

[0015] Optionally, the mechanical kerf cutting operation is performed using a chain-type bottom plate cutter, which includes a traveling unit, a sliding platform mechanism, a chain cutting mechanism, a bucket unit, and a hydraulic and electrical control system. The cutting depth of the chain-type bottom plate cutter is adjustable within the range of 0 to 2.56 meters, and the kerf width is greater than or equal to 200 mm. During the mechanical kerf cutting operation, the cutting depth, feed speed, chain speed, hydraulic system pressure, and motor current parameters are monitored in real time to ensure cutting quality.

[0016] The technical solution provided by this invention has the following advantages compared with the prior art: By acquiring the geological and stress conditions of the target tunnel, and determining the temporal relationship and spatial arrangement of borehole pressure relief and mechanical slotting pressure relief accordingly, the borehole and mechanical slotting form a coupled pressure relief structure in space. This effectively solves the technical problem in the prior art where borehole and slotting are difficult to form an effective spatiotemporal coupling relationship. It fully leverages the synergistic effect of "point-like release" and "linear blocking", avoids local stress concentration and dynamic manifestation induced by improper construction sequence or unreasonable spatial arrangement, significantly improves pressure relief efficiency, reduces safety risks, and achieves precise control of stress release direction.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1This is a cross-sectional view of the combined pressure relief structure of tunnel drilling and slotting according to an embodiment of this application.

[0020] Figure 2 This is a plan view of the combined pressure relief layout of tunnel drilling and slotting according to an embodiment of this application.

[0021] Figure 3 This is a plan view of the drill-cut composite pressure relief roadway according to an embodiment of this application. Detailed Implementation

[0022] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the technical solution of this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] In the description of the embodiments of the present invention, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of the embodiments of the present invention, the borehole diameter D, borehole depth H, borehole spacing L, borehole angle θ, number of borehole rows n, kerf depth Hs, kerf width Ws, and kerf spacing Ls are specified.

[0026] like Figures 1 to 3 As shown, this embodiment provides a combined stress relief method that combines drilling and slotting. This method establishes a mapping relationship between geological stress conditions and stress relief modes, achieving an organic integration of point-like release from drilling and linear blocking via mechanical slotting. The specific implementation process is as follows:

[0027] First, the geological conditions, cross-sectional parameters, and stress conditions of the target roadway are obtained. Geological conditions include the thickness of the bottom coal seam and coal hardness, while stress conditions include the impact hazard level and stress concentration degree (these are existing technologies in the coal mining field, and this invention will not elaborate on their specific classifications). Specifically, this process is not simply data collection, but rather provides a basis for decision-making in subsequent pattern matching. For example, the thickness of the bottom coal seam directly determines the effective boundary of mechanical cutting and whether pre-drilling to create a free surface is necessary; coal hardness affects cutting resistance and borehole stability, which in turn relates to equipment load and construction safety; roadway cross-sectional dimensions limit the operating space of the equipment and the range of borehole layout; and the impact hazard level and stress concentration degree are core indicators for judging the urgency and intensity of pressure relief. By comprehensively acquiring multi-dimensional parameters, the mechanical environment characteristics of the target area can be accurately depicted, avoiding the one-sidedness of evaluation by a single indicator.

[0028] The cross-sectional parameters of the tunnel, including its dimensions and formation, are obtained through geological parameters.

[0029] Secondly, based on the acquired geological and stress conditions, the temporal relationship and spatial arrangement pattern of borehole decompression and mechanical slotting decompression are determined. The temporal relationship includes the operation sequence of drilling before slotting, slotting before drilling, or alternating drilling and cutting. The spatial arrangement pattern includes the arrangement angle and spacing parameters between boreholes and slots. This step embodies the core concept of "condition-driven mode selection" in this application. Unlike the fixed construction routines in the prior art, this embodiment dynamically adapts the optimal strategy according to the actual site conditions. For example, when the bottom coal is thick and the stress is extremely high, the drilling-before-spinning mode is prioritized to utilize borehole guidance and pre-release energy; when it is necessary to protect specific chambers or facilities, the slotting-before-drilling mode is matched to construct a stress isolation barrier; when facing extremely strong impact danger or insufficient single-round decompression, the alternating drilling-cutting mode is matched to achieve graded disturbance control. The design of the spatial arrangement pattern also serves specific mechanical objectives, such as achieving different coupling functions such as guidance, blocking, or expansion by adjusting the angle between the borehole and the slot (vertical, parallel, or oblique), and ensuring continuous coverage of the decompression zone by optimizing the spacing parameters.

[0030] Finally, based on the temporal sequence and spatial arrangement, drilling and mechanical kerfing are performed, creating a coupled and stress-relieving structure in space. The "synergy" and "coupling" referred to here are not simply the superposition of the two processes in time or space, but rather a complementary and enhanced relationship in their mechanical mechanisms. Figure 1 The cross-sectional structure shown illustrates how boreholes, acting as point-like stress relief units, penetrate deep into the coal and rock mass, forming local free surfaces and deep stress release channels. Mechanically cut slots, acting as linear stress relief units, create continuous grooves in the floor, cutting off horizontal stress transmission paths and inducing roof subsidence. These two elements are spatially interconnected or arranged adjacently, jointly constructing a three-dimensional stress relief system combining "point-line-surface" elements. Figure 2 and Figure 3 As shown, in terms of planar layout, the pressure relief range of the borehole and the pressure relief range of the kerf overlap and even intersect, eliminating the pressure relief blind spots present by a single method. This coupled structure allows the borehole to provide guidance and pre-fracture for the kerf, reducing cutting resistance; while the kerf provides a lateral free surface for the borehole, promoting crack propagation and full stress release. Through this synergistic operation, not only is the effective pressure relief range significantly expanded, but precise control of the stress release direction is also achieved, fundamentally solving the problems of low efficiency and high risk caused by the blind assembly of traditional composite pressure relief processes.

[0031] When determining the timing relationship between borehole pressure relief and mechanical slotting pressure relief, the timing relationship is determined to be "drill first, then cut" when the thickness of the bottom coal seam is greater than the effective depth of the mechanical slotting, the impact hazard level reaches medium or above, or direct mechanical slotting poses a risk of excessive equipment load and power manifestation. Specifically, the triggering logic of this mode is based on the matching assessment of geological conditions and equipment capabilities. When the thickness of the coal seam exceeds the effective cutting depth of the mechanical slit cutting equipment (usually around 2.5m), slit cutting alone cannot reach the deep high-stress zone. Drilling is necessary to penetrate deep into the coal seam and establish a release channel. When the roadway is at a medium or higher level of impact hazard, the elasticity of the coal accumulation is high. Directly slit cutting over a large area can easily induce chain jamming, drill bit jacking, or even rockburst accidents due to excessive disturbance. In this case, it is necessary to first perform local pre-release through drilling to reduce the stress level of the coal seam before slit cutting to ensure construction safety. In addition, for coal seams with high hardness or good integrity, direct slit cutting will lead to accelerated wear of the cutting teeth and motor overload. Drilling first can provide a free surface, significantly reducing the cutting resistance of subsequent slit cutting.

[0032] When using a pre-drilling-then-cutting method, pressure relief boreholes are first constructed in the roadway floor. These boreholes have a diameter of 90 to 150 mm, a depth of 3.0 to 5.0 m, and a spacing of 1 to 5 m. These boreholes are used to release localized stress and serve as guide holes for subsequent mechanical cutting. In this stage, the selection of borehole parameters balances pressure relief efficiency and construction efficiency: a borehole diameter of 90 to 150 mm ensures sufficient dust removal space and pressure relief volume while avoiding drilling difficulties and excessive coal damage caused by excessively large boreholes; a depth of 3.0 to 5.0 m covers the core area of ​​the stress concentration zone in the floor, ensuring effective energy dissipation; and the spacing of 1 to 5 m is dynamically adjusted according to the coal hardness and stress distribution to ensure that the pressure relief rings between adjacent boreholes overlap. More importantly, these boreholes are not isolated; they spatially form the benchmark for subsequent cutting operations. Figure 1 As shown, the boreholes are arranged linearly along the direction or inclination of the tunnel, and their axial positions accurately mark the cutting path, enabling subsequent cuttings to precisely cut into the predetermined layers, avoiding resource waste and structural damage caused by blind cutting.

[0033] After the pressure relief boreholes are completed, chain-type mechanical slits are made between adjacent pressure relief boreholes or along the connecting lines. The depth of the chain-type mechanical slits is 1.0 to 2.5 m, the width is greater than or equal to 200 mm, and the length of the chain-type mechanical slits extends throughout the entire pressure relief zone. Here, the chain-type mechanical slits utilize the lateral free surface and guiding effect provided by the boreholes to significantly reduce the clamping force and deviation risk during the cutting process. The slit depth of 1.0 to 2.5 m is set for the optimal working range of existing chain cutters, which can form an effective stress-blocking groove and maintain the stability of equipment operation; the slit width ≥200 mm provides sufficient compensation space for deformation of the bottom rock strata, preventing premature closure and failure of the groove. Through this "point-first, line-later" construction sequence, the pressure relief boreholes and chain-type mechanical slits together form a point-line combined pressure relief system. Figure 1 As shown, boreholes serve as point-like pressure relief units that penetrate deep into the earth, while slots serve as line-like pressure relief units that connect the boreholes and form a continuous barrier in the shallow and middle parts. The two are interconnected in space and complement each other in function, thus constructing a three-dimensional pressure relief network.

[0034] As a specific application example, the above-mentioned drill-then-cut approach was used to treat a roadway with a bottom coal thickness of 4.5m, a coal hardness of 15MPa, and a medium impact hazard level. During construction, two rows of pressure-relief boreholes were first laid out, 1.0m from each sidewall, with a diameter of 150mm, a depth of 4.5m, and a spacing of 3m. After drilling, tests showed that the amount of drill cuttings decreased from an average of 6.8kg / m to 4.2kg / m, indicating that local stress had been initially released, meeting the prerequisites for safe cutting. Subsequently, chain-type mechanical cutting was carried out along the borehole line, with a cutting width of 200mm, and cutting operations were performed within the effective depth range according to equipment capacity, penetrating the entire pressure-relief zone. Final inspection results showed that the amount of drill cuttings further decreased to 2.8kg / m, the stress release rate reached 58.8%, the pressure relief influence range expanded from 1-3m for a single borehole to 5-8m, and the roadway floor heave decreased by 70.8% compared to before treatment. This example fully verifies that under conditions of thick coal seam and medium to high stress, the pre-drilling and post-cutting mode can effectively solve the problems of insufficient pressure relief and high risk caused by single methods through the synergistic mechanism of borehole pre-release energy, guidance, and expansion of the cut, thus achieving the goal of safe and efficient pressure relief.

[0035] In other embodiments, when directional protection and stress transfer control are required, the timing relationship is determined to be a cut-then-drill pattern. Unlike the aforementioned drill-then-cut pattern, which focuses on pre-releasing high stress, the core concept of this pattern is to use mechanical cuts to construct artificial stress isolation boundaries, thereby changing the stress transfer path of the floor plate to achieve precise protection of specific areas (such as important chambers, intersections, or adjacent roadways). Specifically, when there is a protected object on one side of the roadway that must have its deformation or stress increase strictly limited, or when it is necessary to forcibly guide the energy release direction of the high-stress area to the non-protected area, it is difficult to form a continuous mechanical barrier by simply relying on drilling. In this case, the cut-then-drill pattern should be preferred to ensure that the decompression operation itself does not cause secondary disturbance to the protected object.

[0036] In this mode, a chain-type mechanical cut is first constructed on the tunnel floor to cut off the stress transmission path and form a stress-blocking surface. The depth of the chain-type mechanical cut is 1.0 to 2.5 m, and the width of the chain-type mechanical cut is greater than or equal to 200 mm. For example... Figure 2 As shown, the chain-type mechanical slits spatially constitute a physical barrier perpendicular to or oblique to the principal stress transmission direction. Their depth covers the main stress-transmitting layers in the shallow to middle part of the base, while their width provides ample compensation space for rock compression deformation, preventing premature closure of the slits under high pressure and loss of their blocking function. It should be understood that although the slits cut off the main stress transmission channels, this does not mean that both sides of the slits are "stress-free zones." On the contrary, due to the diffraction effect of stress flow, new residual stress concentration zones often form at the ends and edges of the slits. Therefore, the arrangement of subsequent boreholes is not arbitrarily selected from so-called "low-stress sides," but must be directionally designed based on the stress redistribution law.

[0037] After the chain-type mechanical cutting is completed, pressure relief boreholes are arranged on one or both sides of the chain-type mechanical cutting, depending on the location of the protected object and the high-stress zone. These boreholes are located on the high-stress side facing away from the protected object or in the residual stress concentration area at the edge of the chain-type mechanical cutting. This arrangement principle is key to achieving "directional protection" in this model: by placing the boreholes on the side away from the protected object, the deep free surface provided by the boreholes induces the residual stress accumulated at the edge of the cutting to be released in the direction away from the protected object, thereby preventing stress transfer to the protected area. For example, if the protected object is located on the left side of the roadway, the cutting should be arranged in front of the protected object, while the pressure relief boreholes should be densely arranged on the right side of the cutting (i.e., the side facing away from the protected object), making the right side the main channel for stress release. The depth of the pressure relief boreholes is 3.0 to 5.0 m, forming an angle of 45 to 90° with the plane of the chain-type mechanical cutting. The pressure relief boreholes are arranged symmetrically or staggeredly, forming a coordinated pressure relief structure between the cutting and the boreholes. The 45 to 90° angle range ensures that the borehole can penetrate the pressure relief zone formed by the cut and reach deep high-stress areas, which avoids the difficulty of hole formation caused by slippage along the cut surface and ensures effective connection between the hole and the cut in three-dimensional space.

[0038] Regarding the specific arrangement of boreholes, a symmetrical arrangement refers to placing boreholes at equal distances on both sides of the mechanical cut, suitable for scenarios where the stress environments on both sides are similar and require balanced pressure relief. A staggered arrangement, on the other hand, involves offsetting the boreholes on both sides by 0.5 borehole spacing along the roadway direction. This arrangement effectively avoids the formation of excessively large weakened zones on the same cross-section and expands the pressure relief coverage along the direction, making it particularly suitable for conditions with uneven stress distribution or strong unilateral protection requirements. Regardless of the arrangement, the boreholes and cuts should be closely linked in sequence, typically with an interval not exceeding 24 hours, to prevent stress re-accumulation after the cut, which could increase the risk of borehole construction.

[0039] As a specific application example, the above-mentioned "cut-then-drill" mode was adopted in the roadway management of a mine requiring the protection of an important substation chamber. In this scenario, a transverse chain-type mechanical cut was first constructed 10m in front of the chamber, with a depth of 2.5m and a width of 200mm, spanning the entire width of the roadway to form a stress barrier. Subsequently, pressure relief boreholes were arranged 2m away from the chamber (i.e., the side facing away from the protected object), with a diameter of 150mm, a depth of 4.5m, at a 60° angle to the cut plane, and spaced 2.5m apart. Monitoring data showed that the cut effectively blocked the transmission of mining stress towards the chamber, and the stress increase in the surrounding rock of the chamber was controlled within 10%; at the same time, the pressure relief boreholes on the opposite side successfully guided the directional release of residual stress, with a stress reduction rate of over 25% in the borehole area. This example fully demonstrates that the "cut-then-drill" mode, through the synergistic mechanism of "blocking + directional release," can achieve efficient and controllable floor pressure relief while ensuring the safety of critical facilities.

[0040] In other embodiments, when the impact hazard level is high, or when the effect of single borehole decompression or single mechanical slotting decompression fails to meet the preset decompression target, the timing relationship is determined to be an alternating drilling and cutting mode. This mode is mainly designed for extremely high stress environments or complex geological conditions. Its core concept is to avoid dynamic disasters induced by a single high-intensity decompression disturbance through phased and graded "shallow-deep" alternating operations, while giving the construction plan the ability to adaptively adjust based on real-time feedback. Specifically, in areas with high impact hazard, the elastic energy accumulated inside the coal and rock mass is extremely high and in a critical stable state. If large-diameter deep holes or deep slotting are directly implemented, it is very easy to break the mechanical balance and cause premature rockburst. At this time, the alternating drilling and cutting mode can gradually release energy with a smaller initial disturbance, allowing the stress path of the surrounding rock to transition smoothly to a safe state. In addition, when the stress reduction rate is found to be insufficient or there are blind spots in the decompression range after conventional single-round decompression, this mode provides a standardized remedial and enhancement mechanism to ensure that the final treatment effect meets the engineering requirements.

[0041] When using an alternating drilling and cutting mode, the first round of stress relief is performed: shallow holes and / or small-diameter holes are drilled for initial stress release, and shallow slots are drilled in the areas of these holes to expand the stress relief range. The main purpose of this stage is to explore the stress distribution characteristics and establish an initial free surface under low disturbance conditions. For example, the depth of the shallow holes can be controlled at around 2 to 3 meters, and the hole diameter can be selected from 90 to 120 mm. This can effectively guide the high-stress zone in the shallow part while avoiding instability caused by drilling too deep or too large, which may touch the deep core high-energy zone. The depth of the shallow slots used in conjunction with the drilling is usually 1.0 to 1.5 meters. Their main function is to connect adjacent shallow holes, form an initial stress relief zone in the shallow part of the bottom plate, and provide lateral compensation space for subsequent deep operations. This "small steps, quick progress" strategy not only reduces construction risks but also provides experimental data for the optimization of parameters in the second round.

[0042] Based on the results of the first round of pressure relief, a second round of pressure relief was implemented: deep holes and / or large-diameter holes were constructed to release deep or residual high stress, and deep slots were constructed, forming a continuous groove with the shallow slots. The second round of work was a deeper treatment based on the safety barrier established in the first round. The deep holes typically extended to 4.5 to 5.0 meters or even deeper, with diameters increased to 150 to 200 mm, aiming to penetrate the shallow pressure relief ring and reach the deep high-stress core area, completely cutting off the energy supply channel. Simultaneously, the depth of the deep slots increased to 1.5 to 2.5 meters, and they vertically interconnected with the shallow slots formed in the first round, forming a complete continuous groove structure. This continuous groove not only achieved full coverage in depth but also eliminated potential stress concentration zones left by layered pressure relief through the three-dimensional intersection of boreholes and slots in the horizontal direction, significantly improving the overall pressure relief efficiency. It should be understood that the above two rounds are only illustrative descriptions. In actual engineering, multiple rounds of alternating drilling and cutting can be flexibly executed according to the preset pressure relief target and the feedback from each round of inspection until all indicators fully meet the preset pressure relief target.

[0043] As a specific application example, the aforementioned alternating drilling and cutting mode was adopted in the treatment of roadways in an area of ​​extreme impact hazard in a mine. The initial stress monitoring values ​​in this area remained consistently high, making single stress relief methods ineffective. A strict tiered strategy was implemented during construction: the first round involved drilling shallow holes, 2m deep, 150mm in diameter, spaced 2m apart, and creating shallow cuts 1.5m deep along the borehole connection line to complete preliminary energy release and stress field detection. Based on the first round's data confirming that the shallow stress had decreased to a safe threshold, the second round of work was implemented. Deeper holes, 5m deep and 150mm in diameter, were drilled between the first round's holes, and deep cuts 2.5m deep were created, seamlessly connecting with the shallow cuts to form a continuous stress relief zone. Final results showed that after two rounds of alternating treatment, the stress reduction rate in the area reached 55%, the stress relief influence range stably expanded to over 5m, and roadway deformation was effectively controlled, fully verifying the safety and effectiveness of the alternating drilling and cutting mode in handling extremely high stress problems.

[0044] Building upon the aforementioned embodiments, the spatial arrangement pattern also includes the relative spatial positions of boreholes and mechanical cuts, determined according to the coupling objective. This design principle decouples the specific geometric arrangement from a single construction mode, forming a universal parametric design methodology. This allows technicians to flexibly combine borehole-cut relationships based on actual on-site mechanical requirements, rather than mechanically applying fixed templates. Specifically, the coupling objectives mainly include three categories: guiding, blocking, and expansion. Each objective corresponds to a specific spatial configuration to achieve optimal mechanical response.

[0045] When boreholes are used to guide mechanical kerfs, the spatial relative positions are such that the kerf line is located on the line connecting adjacent boreholes or close to the borehole axis. For example... Figure 2 As shown, this arrangement utilizes boreholes as pre-formed free surfaces and physical references to guide the chain of the chain cutter along a predetermined trajectory. In thick-bottomed or hard coal conditions, direct slit cutting is prone to deviation or chain jamming due to the anisotropy of the coal mass. By strictly confining the slit line within the borehole connection range, it effectively creates an "invisible guide rail" for the slit cutting operation. This not only improves the accuracy of the slit formation but also reduces cutting resistance by utilizing the pre-crushing zone around the borehole, thus extending the equipment's lifespan.

[0046] When mechanical kerfing is used as a stress-breaking surface, the spatial relative positional relationship is such that the borehole and the mechanical kerf are arranged perpendicularly or obliquely. For example... Figure 1 and Figure 3As shown, the core of this configuration lies in maximizing the efficiency of cutting off the horizontal stress transmission path. Vertical arrangement is suitable for conditions where the principal stress direction is clear and parallel to the roadway direction, forming the most direct mechanical barrier. Oblique arrangement is suitable for complex areas where the principal stress direction is inclined or where there is multi-directional stress coupling. By adjusting the included angle, the projected area of ​​the cut surface in the direction of maximum principal stress is maximized, thereby enhancing the blocking effect. In this case, the borehole is usually arranged on the high-stress side of the cut, forming a three-dimensional intersection with the cut, further releasing the residual stress accumulated at the cut end after being blocked.

[0047] When boreholes are used to expand the pressure relief range of mechanical slits, the spatial relative positions are such that the boreholes and mechanical slits are arranged parallel to each other, and the distance between the boreholes and the mechanical slits is determined according to the pressure relief influence range. In this configuration, the pressure relief circles formed by the boreholes and slits overlap spatially. Since the influence radius of borehole pressure relief is usually 10 to 20 times the borehole diameter (i.e., 1 to 3 m), while the influence range of slit pressure relief is about 2 to 3 times the slit depth, arranging them parallel and maintaining an appropriate distance allows the point-like pressure relief zone and the line-like pressure relief zone to be seamlessly integrated, eliminating the pressure relief blind spots existing with a single method, and forming a three-dimensional continuous pressure relief zone.

[0048] Furthermore, the spatial arrangement patterns include symmetrical and staggered arrangements. A symmetrical arrangement refers to placing boreholes at equal distances on both sides of the mechanical cut, with the boreholes on both sides corresponding to the same mileage position along the roadway direction. This pattern is suitable for conventional roadways where the stress environment on both sides is similar and energy needs to be released evenly, ensuring uniform stress on the floor and avoiding asymmetrical deformation caused by eccentric loading. A staggered arrangement, on the other hand, refers to placing the boreholes on both sides of the mechanical cut at a 0.5 hole spacing offset along the roadway direction. For example... Figure 2 As shown, the advantage of the staggered arrangement is that it avoids the formation of too many weakening holes on the same cross section, preventing the base plate from losing too much load-bearing capacity in an instant, which could induce local collapse or sudden heave. At the same time, the staggered holes form a denser stress relief grid in the longitudinal direction, expanding the effective coverage area along the direction, which is particularly suitable for working conditions with uneven stress distribution or high requirements for the integrity of the base plate.

[0049] At the construction organization level, the time interval between drilling and mechanical cutting is within the same shift to 24 hours, and the spatial distance between the drilling and mechanical cutting is 1 to 3 meters. This time interval is limited based on the aging deformation characteristics of the surrounding rock: if the interval is too long, the stress redistribution caused by the earlier construction process (whether drilling or cutting) may have already stabilized or even re-accumulated, leading to higher construction risks for subsequent processes or the loss of the window of opportunity for synergistic effects. Controlling the interval to within 24 hours allows full utilization of the temporary free surfaces and stress disturbance zones created by the preceding operations, achieving continuous pressure relief in a "striking while the iron is hot" manner. The selection of a spatial distance of 1 to 3 meters is based on a balance between extensive engineering practice and theoretical calculations: when the distance is less than 1 meter, the coal pillar between the boreholes and cuts is too narrow, making it prone to through-damage during construction and reducing the overall stability of the floor; when the distance is greater than 3 meters, it exceeds the effective influence radius overlap zone of the drilling and cutting, making it difficult to form a continuous pressure relief network, resulting in residual stress concentration in the middle area. Therefore, 1 to 3 meters is both the mechanical lower limit to ensure synergistic effects and the structural upper limit to ensure construction safety. It should be understood that the above parameters are only preferred ranges. In practical applications, they can be adjusted according to the coal hardness, burial depth and equipment performance, as long as the core concept of co-constructing a continuous pressure relief zone with pores and fissures is met.

[0050] During drilling operations, real-time monitoring of drill cuttings volume, drilling speed, drilling rig current or torque, and dynamic manifestation parameters is used to determine the stress state of the coal seam. This process transforms drilling itself into a stress detection method, achieving dynamic perception through "integrated detection and unloading." Specifically, the amount of drill cuttings directly reflects the volume of coal seam fracture and the degree of stress release under the cutting action of the drill bit. When the amount of drill cuttings per unit depth is significantly higher than the normal benchmark value for the same coal seam, it indicates that the coal seam in that area is in a state of high elastic energy accumulation. Drilling speed and drilling rig current or torque are direct representations of cutting resistance. Under the same propulsion pressure and rotation speed, if the drilling speed suddenly decreases or the current and torque continuously increase, it indicates that the coal seam is under pressure and dense or that there are hard rock interlayers, leading to an abnormal increase in cutting energy consumption. Dynamic manifestation parameters such as stuck drill, blowout, and coal bursts are macroscopic signals of energy instability and release within the coal and rock mass, possessing extremely high early warning value. Through the comprehensive analysis of the above multi-source parameters, the limitations of misjudgment by a single indicator can be overcome, and the stress distribution pattern along the drilling path can be accurately depicted.

[0051] When the amount of drill cuttings increases compared to the baseline value, the drilling speed decreases by more than 30%, the drilling rig current or torque continuously increases by more than 20%, or abnormalities such as stuck drill, blowout, or coal blasting occur, the current location is determined to be a high-stress zone. The 30% and 20% thresholds set here are relative change rate criteria derived from a large number of field engineering practices. Their advantage lies in eliminating absolute value deviations caused by differences in drilling rig performance, drill bit wear, and coal seam hardness, making the determination of high-stress zones universally applicable across working conditions. For example, during the construction of a certain roadway, when drilling reached a depth of 3.5m, the monitoring system showed that the drilling speed suddenly dropped from the normal 1.2m / min to 0.7m / min (a decrease of 41.7%), while the motor current increased from 45A to 58A (an increase of 28.9%), accompanied by slight coal blasting sounds. Based on this, it was immediately determined that the location had entered the high-stress core zone, triggering the subsequent dynamic adjustment mechanism. This quantitative judgment based on real-time data replaces the traditional subjective estimation that relies on human experience, significantly improving the accuracy and safety of pressure relief construction.

[0052] For the identified high-stress areas, parameters were adjusted according to three causes: unrelieved pressure between holes, unrelieved pressure at depth, and localized stress concentration. These adjustments included reducing hole spacing or adding new holes, increasing hole depth or adjusting hole angles, and increasing hole diameter or increasing the number of hole rows. This categorized adjustment strategy constitutes a real-time closed-loop control system during construction, rather than a post-construction remedy. Specifically, if monitoring data shows that high stress response still exists between two adjacent holes, it indicates that the original hole spacing was too large, resulting in ineffective overlap of the stress relief rings and the formation of "stress islands." In this case, measures should be taken to reduce the hole spacing or drill additional holes between the two holes to eliminate the stress relief blind zone. If the drilling parameters show high stress throughout the entire process, but the bottom of the hole still does not penetrate the high-energy zone, or the stress peak position exceeds the original design hole depth, it indicates insufficient deep stress relief. It is necessary to increase the hole depth or adjust the hole angle to make the drilling trajectory penetrate deeper into the high-stress core area or perpendicular to the principal stress direction to enhance the deep energy conduction effect. If the stress is abnormally concentrated in a certain local area and the range is small, simply increasing the hole spacing may cause excessive disturbance. In this case, it is advisable to increase the hole diameter or increase the number of hole rows to expand the stress relief volume of a single hole or to build a multi-hole group synergistic effect to achieve targeted dissipation of local high-energy points. It should be understood that the above adjustment measures can be used individually or in combination according to the actual situation on site. For example, in extremely strong stress areas, a comprehensive strengthening method of "adding holes + increasing depth + increasing diameter" can be adopted simultaneously. This dynamic mechanism of simultaneous construction, monitoring, and adjustment ensures that the decompression scheme always maintains an adaptive match with the actual stress state of the formation, fundamentally avoiding the risk of decompression failure or excessive disturbance caused by blind construction.

[0053] After drilling and mechanical slotting operations are completed, the drilling-slot coupling effect is verified. This verification includes stress field distribution verification, stress relief range verification, borehole-mechanical slot connectivity verification, and roadway deformation control effect verification. This step constitutes the quality acceptance and feedback center of the composite stress relief method. Unlike traditional acceptance methods that only focus on a single indicator, this application specifically emphasizes "connectivity verification" as the core criterion for verifying the synergistic effect of boreholes and slots. Specifically, the stress field distribution verification quantitatively assesses the degree of energy release by comparing the changes in the readings of stress sensors inside the coal body before and after stress relief; the stress relief range verification uses drill cuttings method or geophysical exploration to determine the boundary of the effective stress relief zone and confirm whether it covers the design target area; the roadway deformation control effect verification directly reflects the improvement in surrounding rock stability by monitoring macroscopic indicators such as floor heave and sidewall convergence. Crucially, the borehole-mechanical slot connectivity verification uses a borehole inspection instrument or water injection tracing method to directly verify whether the deep borehole and the shallow-to-medium-level slot are physically connected in space. Only when the two are truly connected can it be proven that the expected "point-line" three-dimensional pressure relief network has been formed. Otherwise, even if individual indicators are qualified, the lack of coordination may lead to a long-term decline in pressure relief effect. This multi-dimensional comprehensive inspection system ensures that the pressure relief project is not only "done", but also "done correctly" and "worked smoothly".

[0054] If the test results do not meet the preset requirements, parameter optimization is performed. Parameter optimization is not arbitrary trial and error adjustment, but a precise correction based on test data and mechanical mechanisms. Specifically, if the stress reduction rate is insufficient, it indicates that the current pressure relief strength cannot counteract the ground stress level. In this case, the drilling depth or diameter should be increased to expand the pressure relief volume of a single hole, or the hole spacing should be reduced and the mechanical slit depth increased to improve the density and penetration of the pressure relief medium. If the pressure relief range is discontinuous, it indicates that there is a blind zone in the spatial overlap between the holes and slits, failing to form an overall pressure relief zone. In this case, the relative positional relationship between the mechanical slit line and the drilling line needs to be adjusted, or the hole spacing and mechanical slit spacing should be directly reduced to ensure that adjacent pressure relief rings fully overlap. If the stress on the side of a specific protected object increases, it means that the pressure relief operation has induced stress to transfer to the protected area, which is an out-of-control release direction. In this case, the drilling layout must be changed immediately, moving it to the high-stress side away from the protected object, or the hole angle should be adjusted to make the crack propagation direction deviate from the protected area. If necessary, mechanical slits should be constructed first to form a blocking surface before drilling operations are carried out to forcibly cut off the stress transmission path to the protected area.

[0055] The optimized parameters are then re-verified and confirmed to meet the standards before being incorporated into subsequent construction plans. This step serves as the final line of defense in closed-loop control, aiming to prevent the blind promotion of unverified adjustments. In actual engineering projects, the complexity of geological conditions means that there may be discrepancies between theoretical calculations and on-site responses; any parameter adjustments must be verified through field measurements on a small-scale test section. Only after all indicators consistently reach the preset pressure relief target during the re-verification process can the optimized parameter combination be solidified into a standard process to guide subsequent large-scale construction. This iterative mechanism of "verification-diagnosis-optimization-re-verification" endows the composite pressure relief method with the ability to adapt to uncertain geological environments, ensuring the reliability and durability of the treatment effect.

[0056] Based on the above embodiments, the mechanical slit cutting operation is performed using a chain-type bottom plate cutter. This limitation clearly anchors the pressure relief method of this application to mechanical cutting technology, thereby distinguishing it from existing technologies such as hydraulic slit cutting and blasting roof cutting. Specifically, the chain-type bottom plate cutter includes a traveling unit, a sliding platform mechanism, a chain cutting mechanism, a bucket unit, and a hydraulic and electrical control system. Among them, the traveling unit is responsible for the autonomous movement and precise positioning of the equipment on the roadway floor, ensuring that the slit trajectory meets the design requirements; the sliding platform mechanism carries the cutting head and realizes its lateral or longitudinal posture adjustment to adapt to the cutting requirements of different inclination angles or depths; the chain cutting mechanism, as the core execution unit, continuously cuts the coal and rock mass through the rotational motion of a high-strength alloy chain to form regular slits; the bucket unit is integrated below or behind the cutting head to collect and discharge coal dust generated during cutting in real time, preventing coal dust accumulation from causing chain jamming or motor overload; the hydraulic and electrical control system provides stable power output and intelligent control logic for the whole machine, ensuring the coordinated operation of each execution mechanism. This modular and integrated mechanical design makes the slit cutting operation highly controllable and repeatable, overcoming the shortcomings of traditional pressure relief methods such as poor forming quality and high safety risks.

[0057] Regarding process parameters, the chain-type floor cutting machine has an adjustable cutting depth ranging from 0 to 2.56 meters, with a kerf width greater than or equal to 200 mm. This wide range of adjustable cutting depth allows it to flexibly adapt to different working conditions, from shallow stress release to deep blockage. In particular, the upper limit of 2.56 meters covers the core strata of most coal mine floor stress concentration zones, ensuring effective pressure relief. The kerf width of ≥200 mm is set based on the rheological characteristics of the surrounding rock under deep high-stress environments. Sufficient kerf width provides the necessary physical compensation space for the compression deformation of the floor strata, effectively preventing premature closure of the kerf under mining stress and loss of pressure relief function. It should be understood that the above parameter ranges are optimal intervals derived from current mainstream equipment performance and engineering practice. In practical applications, if equipment performance is improved or geological conditions are special, adaptive adjustments can be made based on these parameters, as long as the core concept of forming continuous and effective pressure relief kerf is met.

[0058] To ensure cutting quality and construction safety, cutting depth, feed rate, chain speed, hydraulic system pressure, and motor current parameters are monitored in real time during mechanical kerfing operations. This multi-parameter synchronous monitoring mechanism constitutes the "sensory nerves" of the kerfing operation, enabling transparent control over the construction status of underground concealed works. Specifically, real-time feedback on cutting depth ensures that the kerf reaches the designed pressure relief boundary, avoiding pressure relief blind spots due to insufficient depth; the dynamic matching relationship between feed rate and chain speed directly determines cutting efficiency and tool wear, and excessively fast feed or excessively low speed may lead to drill blockage or chain breakage; hydraulic system pressure and motor current are the most sensitive indicators reflecting changes in coal hardness and equipment load status. When a continuous abnormal increase in pressure or current is detected, it often indicates the encounter of hard rock interlayers, poor powder discharge, or impending jamming. At this time, the control system can automatically reduce the feed rate or trigger an alarm shutdown to avoid equipment damage or induce power disasters. This closed-loop feedback control not only ensures the accuracy and continuity of the groove geometry, but also significantly improves the equipment's adaptability and operational reliability under complex geological conditions, providing a solid hardware guarantee for the final formation of the composite pressure relief system.

[0059] It should be noted that any parts not disclosed or specifically described in this invention are existing technology or conventional configurations, and their specific structures and working principles will not be elaborated further. In this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0060] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Other modifications can be readily implemented by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A combined pressure relief method that combines drilling and slit cutting, characterized in that, include: Obtain the geological conditions, cross-sectional parameters, and stress conditions of the target roadway. The geological conditions include the thickness of the bottom coal and the hardness of the coal body. The stress conditions include the impact hazard level and the degree of stress concentration. Based on the geological conditions and stress conditions, the temporal relationship and spatial arrangement pattern of borehole pressure relief and mechanical slotting pressure relief are determined. The temporal relationship includes the operation sequence of drilling before slotting, slotting before drilling, or alternating drilling and slotting. The spatial arrangement pattern includes the arrangement angle and spacing parameters between boreholes and slots. Based on the time sequence and spatial arrangement, drilling and mechanical cutting operations are performed to create a spatially coupled pressure-relieving structure between the drilling and mechanical cutting operations.

2. The composite pressure relief method combining drilling and slit cutting according to claim 1, characterized in that, Determining the timing relationship between borehole pressure relief and mechanical slotting pressure relief includes: When the thickness of the bottom coal is greater than the effective depth of the mechanical cut, the impact hazard level reaches medium or above, or there is a risk of excessive equipment load and power manifestation when directly performing mechanical cutting, the timing relationship is determined to be the drilling-then-cutting mode. When directional protection and stress transfer control are required, the timing relationship is determined to be a cut-then-drill mode; When the impact hazard level is high, or the effect of single borehole pressure relief or single mechanical cutting pressure relief fails to meet the preset pressure relief target, the timing relationship is determined to be a drilling-cutting alternating mode.

3. The composite pressure relief method combining drilling and slit cutting according to claim 2, characterized in that, When the timing relationship is the drill-then-cut mode, the step of performing drilling and mechanical cutting operations according to the timing relationship and the spatial arrangement mode, so that the drilling and mechanical cutting form a coupled and pressure-relieving structure in space, includes: First, pressure relief boreholes are drilled in the roadway floor. The diameter of the pressure relief boreholes is 90 to 150 mm, the depth is 3.0 to 5.0 m, and the spacing is 1 to 5 m. The pressure relief boreholes are used to release local stress and serve as guide holes for subsequent mechanical cutting. After the pressure relief boreholes are constructed, a chain mechanical cut is made between adjacent pressure relief boreholes or along the line connecting the pressure relief boreholes. The depth of the chain mechanical cut is 1.0 to 2.5 m, the width of the chain mechanical cut is greater than or equal to 200 mm, and the length of the chain mechanical cut extends through the entire pressure relief zone. The pressure relief borehole and the chain-type mechanical cutting slit together form a point-line combined pressure relief system.

4. The composite pressure relief method combining drilling and slit cutting according to claim 2, characterized in that, When the timing relationship is the "cut-then-drill" mode, the step of performing drilling and mechanical kerfing operations according to the timing relationship and the spatial arrangement mode, so that the drilling and mechanical kerfing form a spatially coupled pressure-relieving structure, includes: First, a chain mechanical cut is constructed on the floor slab of the roadway to cut off the stress transmission path of the floor slab and form a stress blocking surface. The depth of the chain mechanical cut is 1.0 to 2.5m, and the width of the chain mechanical cut is greater than or equal to 200mm. After the chain mechanical cutting is completed, pressure relief holes are arranged on one or both sides of the chain mechanical cutting according to the protected object and the location of the high stress area. The pressure relief holes are arranged on the high stress side facing away from the protected object or in the residual stress concentration area at the edge of the chain mechanical cutting. The depth of the pressure relief borehole is 3.0 to 5.0 m, and it forms an angle of 45 to 90° with the plane of the chain mechanical cut. The pressure relief borehole is arranged symmetrically or staggeredly to form a pressure relief structure with coordinated cut and hole.

5. The composite pressure relief method combining drilling and slit cutting according to claim 2, characterized in that, When the timing relationship is the drilling-cutting alternating mode, the step of performing drilling operations and mechanical kerfing operations according to the timing relationship and the spatial arrangement mode, so that drilling and mechanical kerfing form a coupled and pressure-relieving structure in space, includes: Perform the first round of pressure relief: construct shallow holes and / or small-diameter holes to perform preliminary stress relief, and construct shallow slits in the area of ​​the shallow holes and / or small-diameter holes to expand the pressure relief range; Based on the results of the first round of pressure relief, the second round of pressure relief is carried out: deep holes and / or large-diameter holes are constructed to release deep or residual high stress, and deep slits are constructed, wherein the deep slits and the shallow slits form a continuous groove. According to the preset pressure relief target, multiple rounds of alternating drilling and cutting are performed until the preset pressure relief target is achieved.

6. The composite pressure relief method combining drilling and slit cutting according to claim 1, characterized in that, The spatial arrangement pattern also includes the relative spatial positions of the borehole and the mechanical cut, which are determined according to the coupling purpose, including: When the borehole is used to guide the mechanical cut, the spatial relative positional relationship is that the mechanical cut line is located on the line connecting adjacent boreholes or close to the borehole axis; When the mechanical cut is used as a stress-blocking surface, the spatial relative positional relationship is that the borehole and the mechanical cut are arranged perpendicularly or obliquely. When the borehole is used to expand the pressure relief range of the mechanical slit, the spatial relative position relationship is that the borehole and the mechanical slit are arranged in parallel, and the distance between the borehole and the mechanical slit is determined according to the pressure relief influence range.

7. The composite pressure relief method combining drilling and slit cutting according to claim 6, characterized in that, The arrangement patterns of the spatial relative positions include: Symmetrical arrangement: With the mechanical cut as the center line, boreholes are arranged at the same distance on both sides of the mechanical cut, and the boreholes on the left and right sides correspond to the same mileage position in the direction of the roadway. Staggered arrangement: The boreholes on both sides of the mechanical cut are staggered by 0.5 hole spacings along the roadway direction; The time interval between drilling and mechanical cutting is within the same shift to 24 hours, and the spatial distance between the drilling and mechanical cutting is 1 to 3 meters.

8. The composite pressure relief method combining drilling and slit cutting according to claim 1, characterized in that, During the drilling operation, the amount of drill cuttings, drilling speed, drilling rig current or torque, and power manifestation parameters are monitored in real time to determine the stress state of the coal body. When the amount of drill cuttings increases compared to the reference value, the drilling speed decreases by more than 30%, the drilling rig current or torque continues to increase by more than 20%, or abnormalities such as stuck drill, blowout, or coal blast occur, the current location is determined to be a high-stress zone. For the high-stress area, according to the three causes of unrelieved pressure between holes, unrelieved pressure in the deep part, and local stress concentration, the parameters are adjusted by taking measures such as reducing the hole spacing or adding holes, increasing the hole depth or adjusting the hole angle, increasing the hole diameter or increasing the number of hole rows.

9. A composite pressure relief method combining drilling and slit cutting according to claim 8, characterized in that, After all the drilling and mechanical cutting operations are completed, the drilling-cutting coupling effect is tested. The test includes stress field distribution test, pressure relief range test, borehole-mechanical cutting connectivity test, and roadway deformation control effect test. If the test results do not meet the preset requirements, parameter optimization is performed, including: If the stress reduction rate is insufficient, increase the drilling depth or diameter, decrease the hole spacing, or increase the depth of the mechanical cut. If the pressure relief range is not continuous, adjust the relationship between the mechanical cut line and the borehole connection line, reduce the hole spacing or the mechanical cut spacing; If the stress on the side of the specific protected object increases, then change the drilling arrangement, adjust the hole angle, or first form the mechanical cut blocking surface; The optimized parameters were re-checked and confirmed to meet the standards before being incorporated into the subsequent construction plan.

10. A composite pressure relief method combining drilling and slit cutting according to claim 1, characterized in that, The mechanical cutting operation is performed using a chain-type bottom plate cutter, which includes a traveling unit, a sliding platform mechanism, a chain cutting mechanism, a bucket unit, and a hydraulic and electronic control system. The cutting depth of the chain-type bottom plate cutting machine is adjustable from 0 to 2.56 meters, and the kerf width is greater than or equal to 200 mm. During the mechanical kerfing operation, the cutting depth, feed speed, chain speed, hydraulic system pressure, and motor current parameters are monitored in real time to ensure cutting quality.

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