A hard roof high-low position synergistic weakening method based on discontinuous cracking

Abstract

The application discloses a hard roof high-low position synergic weakening method based on discontinuous cracking, which comprises the following steps: obtaining reference area rock stratum parameters and current area rock stratum parameters; according to the reference area rock stratum parameters and the current area rock stratum parameters, the roadway is divided into multiple independent sections; a plurality of groups of cracking blast holes are drilled in each independent section, each group of cracking blast holes is composed of a high-position deep hole and a low-position shallow hole; according to the obtained weakening unit length and rock bridge unit length, the high-position deep hole and the low-position shallow hole are alternately arranged along the axial direction of the roadway; when the cracking blast holes are detonated, the detonation time of the high-position deep hole is delayed from the detonation time of the low-position shallow hole. Through the synergic cooperation of the low-position shallow hole and the high-position deep hole, the low-position hard rock and the high-position hard rock of the hard roof of the roadway are cut off, a discontinuous cracking structure of the weakening unit-rock bridge unit is constructed, the drilling amount of the cracking blast holes is reduced, thereby the explosive consumption is reduced, and the influence of the huge blasting energy generated during continuous roof cutting on the stability of the surrounding rock of the roadway is avoided.

Description

[Technical Field]

[0001] This invention relates to the field of coal mining technology, and in particular to a method for high-low level coordinated weakening of a hard roof based on discontinuous fracturing. [Background Technology]

[0002] Rigid roofs are generally characterized by their great thickness, exceptionally high strength, excellent integrity, and strong self-stabilizing ability. Numerous control methods exist for rigid roofs, including hydraulic fracturing, pre-fracturing and roof cutting, and ground fracturing techniques. These technologies have played a crucial role in resolving overhanging roof issues.

[0003] However, traditional hard roof control techniques have key flaws: First, relying on single borehole parameters makes it difficult to adapt to the significant differences between high and low hard rock layers. This means it cannot ensure that a short cantilever beam is formed after cutting to achieve good pressure relief while simultaneously ensuring the cut surface extends beyond the roadway anchorage zone to minimize the impact of roof cutting on the stability of the surrounding rock. Second, while continuous, dense roof cutting techniques used to promote collapse are effective, they involve a large number of boreholes and high explosive consumption. The blasting vibrations can easily damage the roadway's surrounding rock structure and support system, and frequent disturbances further worsen the long-term stability of the surrounding rock. Third, static design methods ignore the dynamic changes in roof lithology, often leading to deviations in the preset cutting position, resulting in incomplete cutting or failure to cut the hard rock layer. Specifically, large-angle boreholes are limited by length and sealing requirements, making it difficult to cut low-lying hard rock, and excessively large angles shorten the horizontal safety distance between the charging point and the roadway, threatening roadway stability. Conversely, small-angle boreholes require excessively long construction to cut high-lying thick hard rock, resulting in excessively long cantilever beams and poor pressure relief after cutting. Although there have been attempts at layered drilling, the lack of a quantitative control mechanism for the safe offset of the charge point and the lack of a design concept that utilizes the stress synergy between discontinuously fractured rock blocks have resulted in poor synergistic fracturing effect on the hard top plate at high and low positions.

[0004] Therefore, there is an urgent need to develop a new roof cutting technology that integrates dynamic lithology adaptation, synergistic fracturing of high and low hard rocks, and efficient utilization of natural rock bridges, so as to achieve efficient roof pressure relief while ensuring roadway safety. [Summary of the Invention]

[0005] To address the aforementioned technical problems, this invention proposes a method for coordinated weakening of a rigid top plate at high and low positions based on discontinuous cracking.

[0006] This invention is achieved by the following technical solution:

[0007] A method for coordinated weakening of a rigid top plate based on discontinuous fracturing at high and low elevations includes:

[0008] Obtain the rock strata parameters of the reference area and the current area;

[0009] Based on the rock strata parameters of the reference area and the rock strata parameters of the current area, the tunnel is divided into multiple independent sections;

[0010] Several sets of fracturing blast holes were drilled in each independent section, and each set of fracturing blast holes consisted of a high-position deep hole and a low-position shallow hole.

[0011] Obtain the explosive fracturing radius, and based on the explosive fracturing radius, obtain the weakening unit length and the rock bridge unit length, and arrange the high-level deep holes and the low-level shallow holes alternately along the roadway axis according to the weakening unit length and the rock bridge unit length;

[0012] When the fracturing borehole is detonated, the detonation time of the higher-level deep borehole is delayed compared to the detonation time of the lower-level shallow borehole. .

[0013] By adopting the above-mentioned technical solution, areas with small differences in hard rock strata parameters in the roadway are dynamically divided into independent sections. Low-level shallow holes and high-level deep holes are drilled in the independent sections. Through the coordinated operation of low-level shallow holes and high-level deep holes, the low-level hard rock and high-level hard rock of the roadway's hard roof are cut off in a targeted manner. At the same time, the spatial structure of alternating low-level shallow holes and high-level deep holes constructs a discontinuous fracturing structure of weakened unit-rock bridge unit. By utilizing the gravity-mining stress coupling effect to make the rock bridge unit collapse autonomously in a discontinuous roof cutting method, the amount of fracturing blast holes drilled is reduced, thereby reducing explosive consumption and avoiding the impact of the huge blasting energy generated during continuous roof cutting on the stability of the roadway's surrounding rock.

[0014] As described above, the method for coordinated weakening of a hard top plate based on discontinuous fracturing, specifically the acquisition of strata parameters in the reference zone and the current zone, includes:

[0015] Drilling was performed at the beginning of the tunnel to obtain the rock strata parameters of the reference area.

[0016] Starting from the initial section of the tunnel, boreholes are drilled every 30m to obtain multiple sets of rock strata parameters for the current area.

[0017] The above-described method for coordinated weakening of a hard, discontinuously fractured top plate, whereby the reference zone strata parameters include the depth of the low-lying hard rock strata top plate in the reference zone. Thickness of low-lying hard rock layers in the benchmark area Depth of the top plate of the high-level hard rock layer in the benchmark area and the thickness of high-level hard rock layers in the benchmark area ;

[0018] The current strata parameters include the depth of the center of the low-lying hard rock strata from the top plate in the current area. The current thickness of the low-lying hard rock layer in the area The current area has a high-level hard rock layer center at a depth from the top plate. and the current thickness of high-level hard rock layers in the area .

[0019] The above-described method for coordinated weakening of a hard roof at different elevations based on discontinuous fracturing, wherein the roadway is divided into multiple independent sections according to the rock strata parameters of the reference area and the current area, includes:

[0020] Calculate the center depth deviation rate of low-lying hard rock The calculation formula is as follows:

[0021]

[0022] Calculate the center depth deviation rate of high-altitude hard rock The calculation formula is as follows:

[0023]

[0024] Calculate the relative deviation rate of low-lying hard rock thickness The calculation formula is as follows:

[0025]

[0026] Calculate the relative deviation rate of high-altitude hard rock thickness The calculation formula is as follows:

[0027]

[0028] Based on the low-lying hard rock center depth deviation rate The deviation rate of the center depth of the high-level hard rock The relative deviation rate of the thickness of the low-lying hard rock and the relative deviation rate of the thickness of the high-level hard rock The relative change rate of lithological parameters was obtained. The relative rate of change of the lithological parameters The calculation process is as follows: If the relative change rate of the lithological parameters If the value is less than the preset threshold, it will be divided into an independent segment.

[0029] The above-described method for coordinating high and low-level weakening of a hard top plate based on discontinuous fracturing includes drilling several sets of fracturing boreholes in each independent section, comprising:

[0030] Set the drilling angle of the low-position shallow hole and the drilling angle of the high-position deep hole ;

[0031] According to the drilling angle of the low-position shallow hole and the depth of the center of the low-lying hard rock layer in the current area from the top plate The depth length of the shallow hole at the lower position is obtained. The calculation process is as follows:

[0032]

[0033] According to the drilling angle of the high-level deep hole and the current depth of the center of the high-level hard rock layer from the top plate The depth length of the high-position deep hole is obtained. The calculation process is as follows:

[0034]

[0035] As described above, in a method for coordinating high and low-level weakening of a hard top plate based on discontinuous cracking, the drilling angle of the low-level shallow hole is set. and the drilling angle of the high-position deep hole ,include:

[0036] The drilling angle of the low-position shallow hole To meet the sealing length requirement of the aforementioned shallow hole. Not less than the hole depth length of the lower shallow hole 1 / 3;

[0037] The drilling angle of the high-level deep hole To meet the sealing length requirement of the high-level deep hole Not less than the hole depth length of the high-position deep hole 1 / 3 of.

[0038] As described above, in a method for coordinating high and low-level weakening of a hard top plate based on discontinuous cracking, the drilling angle of the low-level shallow hole is set. and the drilling angle of the high-position deep hole It also includes:

[0039] The drilling angle of the low-position shallow hole It is also necessary to satisfy the vertical projection position of the loading point of the low-position shallow hole. Not less than the roadway anchorage area ,Right now

[0040]

[0041] The drilling angle of the high-level deep hole It is also necessary to satisfy the vertical projection position of the loading point of the high-position deep hole. Not less than the roadway anchorage area ,Right now

[0042]

[0043] As described above, in a method for coordinating high and low-level weakening of a hard top plate based on discontinuous cracking, the drilling angle of the low-level shallow hole is set. and the drilling angle of the high-position deep hole It also includes:

[0044] The drilling angle of the low-position shallow hole It also needs to meet the requirements of low-level cantilever after cutting through low-level hard rock. The length should be less than 10m, and the low-mounted cantilever... for:

[0045]

[0046] The drilling angle of the high-level deep hole It also needs to meet the requirements of high-level cantilever after high-level hard rock cutting. The height must be less than 10m, and the high-mounted cantilever... for:

[0047]

[0048] The above-described method for coordinating high-low level weakening of a hard roof based on discontinuous fracturing includes obtaining the explosive fracturing radius, determining the weakening unit length and rock bridge unit length based on the explosive fracturing radius, and alternately arranging the high-level deep holes and the low-level shallow holes along the roadway axis according to the weakening unit length and the rock bridge unit length, comprising:

[0049] According to the explosive's fracture radius The length of the weakening unit is obtained. The length of the weakening unit Twice the fracture radius of the explosive ;

[0050] According to the length of the weakening unit The length of the rock bridge unit is obtained. The length of the rock bridge unit =1-1.5 times the length of the weakening unit ;

[0051] According to the explosive's fracture radius and the length of the rock bridge unit Set the spacing between two adjacent sets of fracturing boreholes. for:

[0052]

[0053] The above-described method for coordinating high-low level weakening of a hard roof based on discontinuous fracturing, comprising obtaining the explosive fracturing radius, determining the weakening unit length and rock bridge unit length based on the explosive fracturing radius, and alternately arranging the high-level deep holes and the low-level shallow holes along the roadway axis according to the weakening unit length and the rock bridge unit length, further includes:

[0054] The spacing between the high-level deep holes and the low-level shallow holes within the same group of fracturing boreholes. Set as the radius of the explosive crack .

[0055] Compared with existing technologies, the present invention proposes a method for coordinated weakening of a hard top plate based on discontinuous cracking at high and low positions, which has the following advantages:

[0056] 1. The proposed method for weakening hard roof through high-low synergistic fracturing involves dynamically dividing areas with small differences in hard rock parameters within a roadway into independent sections. Within these independent sections, shallow low-level holes and deep high-level holes are drilled. Through the coordinated operation of these holes, the low-level and high-level hard rock of the roadway's hard roof are selectively cut. Simultaneously, the alternating arrangement of these holes creates a discontinuous fracturing structure of weakened units – rock bridge units. By utilizing the gravity-mining stress coupling effect to cause the rock bridge units to collapse autonomously in this discontinuous roof-cutting method, the amount of fracturing boreholes drilled is reduced, thereby reducing explosive consumption and avoiding the impact of the enormous blasting energy generated during continuous roof-cutting on the stability of the roadway's surrounding rock.

[0057] 2. The high-low position synergistic fracturing and weakening method for hard roof proposed in this invention, which drills shallow holes at low positions and deep holes at high positions in independent sections, can better adapt to the significant differences between high and low hard rock layers compared to the traditional single-hole design. Moreover, the drilling angle and depth of the shallow holes at low positions and the deep holes at high positions can be designed according to the location and characteristics of the hard rock layers at high and low positions, thereby better preventing the problem of incomplete or excessive roof cutting, ensuring that hard rock layers at different locations can be effectively cut off, and the reasonable drilling angle design can also minimize the impact on the stability of the surrounding rock of the roadway itself during roof cutting. [Attached Image Description]

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0059] Figure 1 This is a flowchart of a high-low level coordinated weakening method for a rigid top plate based on discontinuous cracking according to the present invention;

[0060] Figure 2 This is a schematic diagram of the cracking structure of the weakening unit - rock bridge unit of the present invention;

[0061] Figure 3 This is a schematic diagram illustrating the top-cutting scheme of the present invention.

Detailed Implementation Methods

[0062] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0063] Please refer to Figures 1 to 3 As shown, this embodiment of the invention proposes a method for coordinated weakening of a hard top plate based on discontinuous cracking, including steps S1-S5, wherein:

[0064] S1, obtain the rock strata parameters of the reference area and the current area.

[0065] Specifically, the strata parameters of the reference area include the depth of the low-lying hard rock top plate in the reference area. Thickness of low-lying hard rock layers in the benchmark area Depth of the high-level hard rock roof in the benchmark area and the thickness of high-level hard rock layers in the benchmark area The current strata parameters include the depth of the center of the low-lying hard rock in the current area from the top plate. The current thickness of the low-lying hard rock layer in the area The current depth of the center of the high-level hard rock in the area from the top plate and the current thickness of high-level hard rock layers in the area .

[0066] The aforementioned depth of the low-lying hard rock stratum roof refers to the vertical distance from the roadway roof to the upper boundary of the low-lying hard rock stratum, while the aforementioned depth of the high-lying hard rock stratum roof refers to the vertical distance from the roadway roof to the upper boundary of the high-lying hard rock stratum.

[0067] Furthermore, as a preferred embodiment of this solution and not a limitation thereof, step S1 includes steps S11-S12, wherein:

[0068] S11, Drilling is performed at the beginning of the tunnel to obtain the rock strata parameters of the reference area;

[0069] S12, starting from the initial section of the tunnel, boreholes are drilled every 30m to obtain multiple sets of rock strata parameters for the current area.

[0070] Specifically, in the initial section of the tunnel or the first construction section, a region with stable geological conditions and no significant disturbance to lithological characteristics (such as the absence of faults, cracks, or fracture zones) is selected as the benchmark area. A core drilling rig is used to drill a geological exploration hole with a diameter of 75 mm in this area. Then, a borehole imaging device is used to image and detect the geological exploration hole and measure and obtain the strata parameters of the benchmark area.

[0071] Starting from the initial section of the tunnel, a geological exploration hole with a diameter of 75mm is drilled every 30m along the tunnel direction. Similarly, a borehole imaging device is used for imaging detection to measure and obtain the current area rock strata parameters. In this way, boreholes are drilled every 30m to obtain multiple sets of the current area rock strata parameters.

[0072] In this embodiment, by selecting a region with stable geological conditions and no obvious disturbance as the benchmark region, a unified and reliable reference standard is provided for the subsequent analysis of the hard rock layer parameters in the current region and the design of the roof cutting scheme. This avoids the unreasonable design of the roof cutting scheme due to excessive differences in the reference benchmark, which would damage the long-term stability of the surrounding rock of the roadway.

[0073] S2, based on the rock strata parameters of the reference area and the rock strata parameters of the current area, obtain the relative change rate of lithological parameters. According to the relative ratio of the lithological parameters The alleyway is divided into several independent sections.

[0074] Specifically, the relative rate of change of lithological parameters This is an indicator used to quantify the degree of difference in lithological parameters across different regions, reflecting the extent of change in hard rock strata in the current region relative to a baseline state. This embodiment compares and analyzes multiple sets of current region lithological parameters obtained above with those of the baseline region to obtain the relative change rate of lithological parameters for each current region. If the relative change rate of the lithological parameters of the current region is obtained If the relative change rate of the lithological parameters is less than the preset lithological parameters, it indicates that the hard rock parameters of the current area are not significantly different from those of the benchmark area. Therefore, the area is divided into an independent section, and the same top-cutting scheme is adopted in each independent section.

[0075] If the relative change rate of lithological parameters in a certain current region If the relative change rate of the preset lithological parameters exceeds the threshold, it indicates that the parameters of the hard rock layer in the current area have changed significantly. Therefore, it cannot be divided into an independent section. Instead, a new cutting scheme that is adapted to the parameters of the hard rock layer in the area needs to be designed.

[0076] It should be noted that the setting value of the relative change rate of the above-mentioned preset lithological parameters needs to be comprehensively determined based on the explosive performance, charge amount, drilling design (such as drilling depth and angle) and engineering requirements (such as how thick the rock layer needs to be cut). Generally speaking, when the relative change rate of lithological parameters reaches a deviation of 15% to 25%, the engineers need to be highly vigilant. Preferably, in this embodiment, the relative change rate of the preset lithological parameters is set to 20%.

[0077] In this embodiment, areas with small differences in hard rock parameters are divided into independent sections based on the relative change rate of lithological parameters, and the same top-cutting scheme is adopted in each independent section, which helps to standardize the construction process, improve construction efficiency and shorten the construction period.

[0078] Furthermore, as a preferred embodiment of this solution and not a limitation thereof, step S2 includes steps S21-S25, wherein:

[0079] S21, Calculate the center depth deviation rate of low-lying hard rock. The calculation formula is as follows:

[0080]

[0081] S22, Calculate the center depth deviation rate of high-altitude hard rock. The calculation formula is as follows:

[0082]

[0083] S23, Calculate the relative deviation rate of low-lying hard rock thickness. The calculation formula is as follows:

[0084]

[0085] S24, Calculate the relative deviation rate of high-altitude hard rock thickness. The calculation formula is as follows:

[0086]

[0087] S25, based on the aforementioned low-lying hard rock center depth deviation rate The deviation rate of the center depth of the high-level hard rock The relative deviation rate of the thickness of the low-lying hard rock and the relative deviation rate of the thickness of the high-level hard rock The relative change rate of the lithological parameters was obtained. The relative rate of change of the lithological parameters The calculation process is as follows: If the relative change rate of the lithological parameters If the value is less than the preset threshold, it will be divided into an independent segment.

[0088] By analyzing the rock strata parameters of each group in the current area through the above steps S21-S24, the deviation rate of the center depth of low-position / high-position hard rock and the relative deviation rate of the thickness of low-position / high-position hard rock can be obtained. The deviation rate of the center depth of low-position / high-position hard rock can reflect the degree of deviation of the spatial position of the hard rock layer in the current area from the depth of the hard rock layer in the reference area. The relative deviation rate of the thickness of low-position / high-position hard rock can reflect the degree of change of the thickness of the hard rock layer in the current area from the thickness of the hard rock layer in the reference area.

[0089] Furthermore, excessive variations in the depth of hard rock layers can easily cause the cutting area to deviate from the target layer, while excessive variations in the thickness of hard rock layers may result in an inability to bear the expected load. Therefore, in order to avoid excessive variations in the depth or thickness of the current area, which could lead to the failure of the cutting scheme, this embodiment takes the relative change rate of lithological parameters in each current area as the maximum value of the depth deviation rate of the low / high hard rock center and the relative deviation rate of the thickness of the low / high hard rock in the current area as a comprehensive judgment index, thereby ensuring that the hard rock layer parameters in each section are within the design safe and controllable range to the greatest extent possible.

[0090] To better understand this embodiment, this embodiment uses the baseline value of the low-lying hard rock roof depth of the assumed reference zone strata parameters. The baseline value for the thickness of the low-lying hard rock layer is 10m. The depth was set to 5m, and the relative change rate of low-level lithological parameters was also set. Taking 20% ​​as an example, and combining it with the formula for calculating the depth deviation rate of the low-lying hard rock center, it can be seen that the threshold for the depth of the low-lying hard rock center from the top plate in each current region is... Therefore, we can solve this problem. The range is 9-11m. That is, if the depth of the center of the low-lying hard rock in the current area from the top plate is less than 9m or greater than 11m, it indicates that the hard rock depth in the current area varies too much. Combining this with the formula for calculating the relative deviation rate of low-lying hard rock thickness, the threshold for the low-lying hard rock thickness in each current area can be determined as follows: Therefore, we can solve this problem. The range is 4-6m. That is to say, if the thickness of the low-lying hard rock in the current area is less than 4m or greater than 6m, it indicates that the thickness variation in the current area is too large.

[0091] Similarly, based on the benchmark values ​​of the high-level hard rock top depth and high-level hard rock thickness in the benchmark area, the threshold values ​​of the high-level hard rock center depth from the top plate and the high-level hard rock thickness in each current area can be obtained. If the low-level / high-level hard rock center depth from the top plate in the current area exceeds the threshold range, or the low-level / high-level hard rock thickness exceeds the threshold range, it can be determined that the rock strata in the current area have changed too much.

[0092] S3, Drill several sets of fracturing boreholes in each independent section, each set of fracturing boreholes consisting of a high-position deep hole and a low-position shallow hole.

[0093] Specifically, the fracturing boreholes drilled in this embodiment adopt a dual-hole design, that is, a combination of shallow low-level holes and deep high-level holes. Through the coordinated operation of the shallow low-level holes and the deep high-level holes, the hard rock at both the lower and upper levels of the roadway's hard roof is cut off in a targeted manner. Compared with the traditional single-hole design, it can better adapt to the significant differences between the high and low hard rock layers. Moreover, the drilling angle and depth of the shallow low-level holes and the deep high-level holes can be designed according to the location and characteristics of the high and low hard rock layers, thereby better preventing the problems of incomplete or excessive roof cutting. This ensures that the hard rock layers at different locations can be effectively cut off, and the reasonable drilling angle design can also minimize the impact on the stability of the roadway's surrounding rock itself during roof cutting.

[0094] In addition, when drilling fracturing blast holes, the engineering designers first set the drilling angle for the shallow holes at low positions and the drilling angle for the deep holes at high positions. Then, they verify whether the set drilling angles meet the following requirements: whether the vertical projection of the charge point exceeds the roadway anchorage zone; whether the sealing length of the shallow holes at low positions is not less than 1 / 3 of the hole depth; whether the sealing length of the deep holes at high positions is not less than 1 / 3 of the hole depth; and whether the cantilever after cutting off the hard rock at high positions is less than 10m, and the cantilever after cutting off the hard rock at low positions is less than 10m. If any of these requirements are not met, it indicates that the currently set drilling angles are unreasonable and the drilling angles for the shallow holes at low positions and the deep holes at high positions need to be reset.

[0095] In this embodiment, the drilling angles of both the low-level shallow holes and the high-level deep holes must meet the constraint that the vertical projection of the charging point exceeds the anchoring zone of the roadway. This is to avoid the impact of blasting energy on the roadway support structure, which could lead to support failure, thereby minimizing the impact on the stability of the surrounding rock during roof cutting. The sealing length must be no less than 1 / 3 of the hole depth to prevent poor sealing due to insufficient sealing length, which could lead to gas leakage and safety risks. It also ensures the effective use of blasting energy and avoids energy waste. The cantilever length must be less than 10m to avoid shearing damage or bending fracture caused by excessive cantilever length, and also to avoid sudden roof collapse caused by incomplete roof cutting and pressure relief due to excessive cantilever length.

[0096] Furthermore, as a preferred embodiment of this solution and not a limitation thereof, step S3 includes steps S31-S33, wherein:

[0097] S31, Set the drilling angle of the low-position shallow hole. and the drilling angle of the high-position deep hole ;

[0098] S32, based on the drilling angle of the low-position shallow hole and the depth of the center of the low-lying hard rock layer in the current area from the top plate The depth length of the shallow hole at the lower position is obtained. The calculation process is as follows:

[0099]

[0100] S33, based on the drilling angle of the high-position deep hole and the current depth of the center of the high-level hard rock layer from the top plate The depth length of the high-position deep hole is obtained. The calculation process is as follows:

[0101]

[0102] Specifically, when drilling fracturing blast holes, engineering designers can first set the drilling angles for low-level shallow holes and high-level deep holes based on previous top-cutting schemes or the actual rock strata parameters at the construction site. Then, based on the set drilling angles, they can calculate the hole depths to be drilled for the low-level shallow holes and high-level deep holes. Finally, based on the calculated hole depths and the set drilling angles, they can verify whether the set drilling angles are reasonable.

[0103] In a preferred embodiment, step S31 includes steps S311-S312, wherein:

[0104] S311, the drilling angle of the shallow hole at the low position must meet the sealing length requirement of the shallow hole at the low position. Not less than 1 / 3 of the hole depth length of the shallow hole in the lower position;

[0105] S312, the drilling angle of the high-position deep hole must meet the sealing length of the high-position deep hole. It is not less than 1 / 3 of the hole depth length of the high-position deep hole.

[0106] Specifically, the sealing length of shallow holes and deep holes refers to the length of the borehole openings of shallow holes and deep holes that are sealed with sealing materials before blasting. This prevents the blasting energy from leaking out of the opening during blasting, ensures that the blasting energy is concentrated on the rock mass, improves blasting efficiency, and also reduces hazards such as flyrock and noise.

[0107] Among them, the sealing materials mentioned above are generally made of clay, sand and water mixed in a certain proportion to form blasting mud (i.e. special blasting sealing mud). Because this type of blasting mud is dense and has a certain degree of plasticity, it can effectively block the leakage of gas and blasting energy. It is also non-flammable, non-explosive and has a high safety level. Therefore, it is the most commonly used sealing material in this engineering field.

[0108] In a preferred embodiment, step S31 further includes steps S313-S314, wherein:

[0109] S313, the drilling angle of the low-position shallow hole It is also necessary to satisfy the vertical projection position of the loading point of the low-position shallow hole. Not less than the roadway anchorage area ,Right now

[0110]

[0111] S314, the drilling angle of the high-position deep hole It is also necessary to satisfy the vertical projection position of the loading point of the high-position deep hole. Not less than the roadway anchorage area ,Right now

[0112]

[0113] Specifically, the roadway anchorage zone refers to the area reinforced by anchoring support structures such as anchor bolts, anchor cables, and anchor mesh after roadway excavation to prevent deformation and collapse of the surrounding rock (such as roof, sidewalls, and floor). The vertical projection of the charging points in low-level shallow holes and high-level deep holes extends beyond the roadway anchorage zone. This indicates the presence of a certain thickness of unanchored rock mass between the charging point and the anchoring support structure, i.e., a buffer layer. This layer prevents the blasting energy generated during blasting from directly impacting the anchoring support structure, avoiding damage to the anchor bolts, anchor cables, or anchor mesh, which could lead to support structure failure and reduce the stability of the roadway surrounding rock.

[0114] In a preferred embodiment, step S31 further includes steps S315-S316, wherein:

[0115] S315, the drilling angle of the low-position shallow hole It also needs to meet the requirements of low-level cantilever after cutting through low-level hard rock. The length should be less than 10m, and the low-mounted cantilever... for:

[0116]

[0117] S316, Drilling angle of the high-position deep hole It also needs to meet the requirements of high-level cantilever after high-level hard rock cutting. The height must be less than 10m, and the high-mounted cantilever... for:

[0118]

[0119] Specifically, low / high cantilever refers to the cantilever beam formed above the roadway roof by the remaining uncut hard rock after the hard rock layer has been cut by blasting. Since the bending moment and shear force of the cantilever beam will increase significantly with the increase of the cantilever beam length, in order to avoid the cantilever beam from breaking or becoming unstable due to stress concentration exceeding the shear and bending strength of the hard rock layer, which would lead to the sudden collapse of the cantilever rock block, the drilling angle of the low-level shallow hole and the high-level deep hole must ensure that the length of the low-level cantilever and the high-level cantilever is less than 10m, so that the bending moment and shear force of the hard rock layer cantilever are within a safe range, and the sudden collapse of the cantilever rock block is avoided.

[0120] See attached diagram. Figure 3 As shown in the diagram, this embodiment provides a schematic diagram of the top-cutting scheme to facilitate a better understanding of the above process. The specific calculation process of this scheme is as follows:

[0121] First, the depth of the center of the low-lying hard rock layer in the current area from the top plate can be obtained using borehole imaging equipment. The depth is 13m, and the current area has a high hard rock layer center distance from the top plate. The depth is 39m, and the current area has a low-lying hard rock layer thickness. The thickness of the high-level hard rock layer in the current area is 6m. The drilling depth is 16m, and the drilling angle for the shallow hole at the low position is set. The drilling angle is 60° for high-level deep holes. The angle is 80°, and the roadway anchorage zone in this embodiment is... It is 2m.

[0122] Based on the parameters obtained above and combined with the set drilling angle, the drilling depth can be obtained, which is the hole depth length for low-lying, shallow holes. According to the calculation formula in step S32, we can obtain For the depth length of high-position deep holes According to the calculation formula in step S33, we can obtain Based on the depth lengths of the shallow holes at lower positions and the deep holes at higher positions, the sealing lengths of the shallow holes at lower positions that meet the sealing length requirements can be obtained as follows: The sealing length of the high-position deep hole is According to the calculation in step S313, the vertical projection position of the loading point of the low-position shallow hole can be obtained as follows: According to the calculation in step S314, the vertical projection position of the loading point in the high-position deep hole can be obtained as follows: Therefore, it can be seen that the vertical projection positions of the low-level shallow hole charging point and the high-level deep hole charging point are both greater than the roadway anchorage zone.

[0123] Based on the calculation in step S315, the low-level cantilever of the low-level shallow hole can be obtained as follows: According to the calculation in step S316, the high-level cantilever of the high-level deep hole is... Therefore, it can be seen that the low-position cantilever of the shallow hole and the high-position cantilever of the deep hole are both less than 10m. Thus, the drilling angle settings for the shallow hole and the deep hole are reasonable and meet the design requirements.

[0124] It is worth noting that if any item in the above verification process fails to meet the design requirements, it proves that the drilling angle setting is unreasonable. In this case, the drilling angle needs to be reset and recalculated until the drilling angle setting meets all the above constraints.

[0125] S4, obtain the explosive fracturing radius, obtain the weakening unit length and rock bridge unit length based on the explosive fracturing radius, and arrange the high-level deep holes and the low-level shallow holes alternately along the roadway axis according to the weakening unit length and the rock bridge unit length.

[0126] Specifically, by obtaining the explosive fracturing radius, the lengths of the weakened unit and the rock bridge unit are obtained. Based on these parameters, shallow low-level holes and deep high-level holes are arranged along the tunnel axis to construct a discontinuous fracturing structure of weakened unit-rock bridge unit. Thus, during blasting roof cutting, the weakened unit is subjected to explosive fracturing to form a blasting weakened zone, while the rock bridge unit, as the rock mass between two adjacent blasting weakened zones that is not directly destroyed, can avoid the impact of blasting energy on the surrounding rock and reduce the stability of the tunnel surrounding rock itself. At the same time, since roof cutting of a hard roof is carried out during the construction process... The working face advances 100-200m ahead of the face. When the working face reaches the roof-cutting area, the rock strata in this area are within the mining-affected zone. At this point, the hard roof is subjected to strong mining stress, causing the existing weakened blasting zone to further fracture and expand. The previously unbroken rock bridge units will also be destroyed under the mining stress. As the working face pushes past the roof-cutting area, the coal seam is mined out, forming a goaf. The overlying strata above this goaf will collapse and fill the goaf under the influence of gravity and mining stress. At this time, the broken rock bridge units will also collapse. Compared to the traditional continuous roof-cutting method, this discontinuous roof-cutting method does not require drilling a large number of fracturing holes in the roadway due to the rock bridge units, reducing explosive consumption and avoiding the impact of the huge blasting energy generated during continuous roof-cutting on the stability of the surrounding rock.

[0127] It should be noted that the aforementioned explosive fracture radius refers to the radius of the effective fracture range in the rock mass after the explosive blasts. When measuring the explosive fracture radius, blast observation holes are usually arranged in advance. After the explosive blasts, the crack condition of the hole wall after the blast is observed by the drilling imaging equipment, and the maximum distance where a clear through crack appears in the blast observation hole is taken as the explosive fracture radius.

[0128] Furthermore, as a preferred embodiment of this solution and not a limitation thereof, step S4 includes steps S41-S43, wherein:

[0129] S41, based on the explosive's fracture radius The length of the weakening unit is obtained. The length of the weakening unit Twice the fracture radius of the explosive ;

[0130] S42, according to the length of the weakening unit The length of the rock bridge unit is obtained. The length of the rock bridge unit =1-1.5 times the length of the weakening unit ;

[0131] S43, based on the explosive's fracture radius and the length of the rock bridge unit Set the spacing between two adjacent sets of fracturing boreholes. for:

[0132]

[0133] Specifically, the weakening unit refers to the rock mass area that needs to be broken or fractured, namely the pre-fractured area (also known as the blasting weakening zone) generated during low-level shallow hole and high-level deep hole blasting. In this embodiment, the length of the weakening unit is set to twice the radius of the explosive fracturing. The purpose is to ensure that a single weakening unit can completely cover the area of ​​hard rock layer that needs to be cut off or depressurized, and to avoid stress not being effectively released due to insufficient weakening length.

[0134] A rock bridge unit refers to the portion of rock mass between two adjacent blasting weakened zones that has not been directly destroyed. Its length and integrity directly affect the blasting effect and rock mass stability. The length of a rock bridge unit is usually 1 to 1.5 times the length of a weakened unit. By setting a certain length of intact rock mass, we can prevent excessive weakening on the one hand, and avoid the impact of blasting energy on the surrounding rock on the other hand, thereby reducing the stability of the surrounding rock of the tunnel itself.

[0135] Furthermore, as a preferred embodiment of this solution and not a limitation thereof, step S4 further includes step S44, wherein:

[0136] S44, the spacing between the high-position deep holes and the low-position shallow holes within the same group of fracturing boreholes. Set as the radius of the explosive crack .

[0137] In this embodiment, the spacing between the low-level shallow holes and the high-level deep holes in the same set of fracturing blast holes is set as the explosive fracturing radius. This ensures that the fracture boundaries of the two holes just touch during blasting, forming a blasting weakening zone where the high-level hard rock layer and the low-level hard rock layer cooperate with each other. At the same time, a rock bridge unit of a certain length is set between two adjacent sets of fracturing blast holes, thus constructing a discontinuous fracturing structure of weakening unit-rock bridge unit. When the working face pushes past the roof cutting area, the hard roof is subjected to strong mining stress, causing the original blasting weakening zone to further fracture and expand. The original unbroken rock bridge unit will also be destroyed under the action of mining stress, causing the remaining rock bridge unit to fracture autonomously under the coupling effect of gravity and mining stress. Compared with the continuous roof cutting method, the setting of rock bridge unit does not require drilling a large number of fracturing blast holes in the roadway, reducing explosive consumption and avoiding the impact of the huge blasting energy generated during continuous roof cutting on the stability of the roadway surrounding rock itself.

[0138] S5, when the fracturing borehole is detonated, the detonation time of the high-level deep borehole is delayed compared to the detonation time of the low-level shallow borehole, and the delay time is [delay time missing]. .

[0139] In this embodiment, the shallow hole at the lower position is detonated first, which will generate an initial stress field wave and crack network in the rock mass below the roadway. This will cause the hard rock layer at the lower position to break, depressurize, and form a pre-fractured zone of a certain range. After a delay of 50ms, the deep hole at the higher position is detonated. The stress field wave generated at this time will be superimposed with the residual stress field wave in the pre-fractured zone at the lower position and guided upward along the crack network already formed at the lower position, thereby forming a continuous blasting weakening zone and avoiding the phenomenon of high and low position separation and discontinuous weakening.

[0140] Those skilled in the art should understand that the above description is one embodiment provided in conjunction with specific content, and does not imply that the specific implementation of the present invention is limited to these descriptions. Furthermore, due to differences in industry naming conventions, the invention is not limited to the above names or English names. Any methods or structures similar to or identical to those of the present invention, or any technical deductions or substitutions made based on the concept of the present invention, should be considered within the scope of protection of the present invention.

Claims

1. A method for coordinated weakening of a hard top plate based on discontinuous cracking at high and low positions, characterized in that, include: Obtain the rock strata parameters of the reference area and the current area; Based on the rock strata parameters of the reference area and the rock strata parameters of the current area, the tunnel is divided into multiple independent sections; Several sets of fracturing blast holes were drilled in each independent section, and each set of fracturing blast holes consisted of a high-position deep hole and a low-position shallow hole. Obtain the explosive fracturing radius, and based on the explosive fracturing radius, obtain the weakening unit length and the rock bridge unit length, and arrange the high-level deep holes and the low-level shallow holes alternately along the roadway axis according to the weakening unit length and the rock bridge unit length; When the fracturing borehole is detonated, the detonation time of the higher-level deep borehole is delayed compared to the detonation time of the lower-level shallow borehole. ; The rock strata parameters of the reference area include the depth of the top plate of the low-lying hard rock strata in the reference area. Thickness of low-lying hard rock layers in the benchmark area Depth of the top plate of the high-level hard rock layer in the benchmark area and the thickness of high-level hard rock layers in the benchmark area ; The current strata parameters include the depth of the center of the low-lying hard rock strata from the top plate in the current area. The current thickness of the low-lying hard rock layer in the area The current area has a high-level hard rock layer center at a depth from the top plate. and the current thickness of high-level hard rock layers in the area .

2. The method for coordinated weakening of a hard top plate based on discontinuous cracking according to claim 1, characterized in that, The acquisition of the reference area strata parameters and the current area strata parameters includes: Drilling was performed at the beginning of the tunnel to obtain the rock strata parameters of the reference area. Starting from the initial section of the tunnel, boreholes are drilled every 30m to obtain multiple sets of rock strata parameters for the current area.

3. The method for coordinated weakening of a hard top plate based on discontinuous cracking according to claim 1, characterized in that, The process of dividing the roadway into multiple independent sections based on the rock strata parameters of the reference area and the rock strata parameters of the current area includes: Calculate the center depth deviation rate of low-lying hard rock The calculation formula is as follows: ； Calculate the center depth deviation rate of high-altitude hard rock The calculation formula is as follows: ； Calculate the relative deviation rate of low-lying hard rock thickness The calculation formula is as follows: ； Calculate the relative deviation rate of high-altitude hard rock thickness The calculation formula is as follows: ； Based on the low-lying hard rock center depth deviation rate The deviation rate of the center depth of the high-level hard rock The relative deviation rate of the thickness of the low-lying hard rock and the relative deviation rate of the thickness of the high-level hard rock The relative change rate of lithological parameters was obtained. The relative rate of change of the lithological parameters The calculation process is as follows: If the relative change rate of the lithological parameters If the value is less than the preset threshold, it will be divided into an independent segment.

4. The method for coordinated weakening of a hard top plate based on discontinuous cracking according to claim 1, characterized in that, The drilling of several sets of fracturing boreholes in each independent section includes: Set the drilling angle of the low-position shallow hole and The drilling angle of the high-level deep hole ; According to the drilling angle of the low-position shallow hole and the depth of the center of the low-lying hard rock layer in the current area from the top plate The depth length of the shallow hole at the lower position is obtained. The calculation process is as follows: ； According to the drilling angle of the high-level deep hole and the current depth of the center of the high-level hard rock layer from the top plate The depth length of the high-position deep hole is obtained. The calculation process is as follows: 。 5. The method for coordinated weakening of a hard top plate based on discontinuous cracking according to claim 4, characterized in that, The drilling angle of the low-position shallow hole is set. and the drilling angle of the high-position deep hole ,include: The drilling angle of the low-position shallow hole To meet the sealing length requirement of the aforementioned shallow hole. Not less than the hole depth length of the lower shallow hole 1 / 3; The drilling angle of the high-level deep hole To meet the sealing length requirement of the high-level deep hole Not less than the hole depth length of the high-position deep hole 1 / 3 of.

6. The method for coordinated weakening of a hard top plate based on discontinuous cracking according to claim 5, characterized in that, The drilling angle of the low-position shallow hole is set. and the drilling angle of the high-position deep hole It also includes: The drilling angle of the low-position shallow hole It is also necessary to satisfy the vertical projection position of the loading point of the low-position shallow hole. Not less than the roadway anchorage area ,Right now ； The drilling angle of the high-level deep hole It is also necessary to satisfy the vertical projection position of the loading point of the high-position deep hole. Not less than the roadway anchorage area ,Right now 。 7. The method for coordinated weakening of a hard top plate based on discontinuous cracking according to claim 4, characterized in that, The drilling angle of the low-position shallow hole is set. and the drilling angle of the high-position deep hole It also includes: The drilling angle of the low-position shallow hole It also needs to meet the requirements of low-level cantilever after cutting through low-level hard rock. The length should be less than 10m, and the low-mounted cantilever... for: ； The drilling angle of the high-level deep hole It also needs to meet the requirements of high-level cantilever after high-level hard rock cutting. The height must be less than 10m, and the high-mounted cantilever... for: 。 8. The method for coordinated weakening of a hard top plate based on discontinuous cracking according to claim 1, characterized in that, The process of obtaining the explosive fracturing radius, determining the rock bridge unit length based on the explosive fracturing radius, and alternately setting the high-level deep holes and the low-level shallow holes along the roadway axis based on the explosive fracturing radius and the rock bridge unit length includes: According to the explosive's fracture radius The length of the weakening unit is obtained. The length of the weakening unit Twice the fracture radius of the explosive ; According to the length of the weakening unit The length of the rock bridge unit is obtained. The length of the rock bridge unit =1-1.5 times the length of the weakening unit ; According to the explosive's fracture radius and the length of the rock bridge unit Set the spacing between two adjacent sets of fracturing boreholes. for: 。 9. The method for coordinated weakening of a hard top plate based on discontinuous cracking according to claim 8, characterized in that, The process of obtaining the explosive fracturing radius, determining the rock bridge unit length based on the explosive fracturing radius, and alternately setting the high-level deep holes and the low-level shallow holes along the roadway axis based on the explosive fracturing radius and the rock bridge unit length, further includes: The spacing between the high-level deep holes and the low-level shallow holes within the same group of fracturing boreholes. Set as the radius of the explosive crack .

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