A method and system for regional pressure relief by inducing vertical fracture propagation through blasting
Patent Information
- Application Number
- CN202610771065.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-29
- Publication Date
- 2026-09-25
AI Technical Summary
[0004]本申请提供一种爆破诱导垂向裂缝扩展的区域卸压方法及系统，以至少解决现有水力压裂技术在煤矿厚硬顶板中难以实现垂向大范围贯通裂缝，导致卸压效果差、冲击地压风险高的技术问题
本申请提出了一种爆破诱导垂向裂缝扩展的区域卸压方法及系统，所述方法包括：在目标顶板岩层中设置爆破孔，然后通过所述爆破孔实施定向爆破，在所述顶板岩层内形成垂向弱面层和人工诱导应力场；在爆破孔周边设置多个监测孔，通过所述监测孔内不同层位安装的三向应变传感器采集爆破实施后的应变数据；基于有限元反演算法，并根据所述应变数据计算所述人工诱导应力场的全空间分布及垂向应力梯度；将所述全空间分布中的应力值与原位地应力基准值进行对比，得到所述目标顶板内各位置的应力相对变化幅度，然后根据所述应力相对变化幅度，将所述目标顶板划分为水力裂缝起裂区、裂缝扩展加速区和裂缝止裂控制区；在所述水力裂缝起裂区内设置水力压裂孔，以临界间距比K＝L/R确定所述水力压裂孔与所述爆破孔的空间间距，基于所述空间间距在所述水力裂缝起裂区内设置水力压裂孔，其中R为爆破诱导裂隙发育区的半径，K的取值范围为0.85～0.95；在所述水力压裂孔内实施水力压裂作业，使水力裂缝依次经所述起裂区起裂、在所述扩展加速区内沿所述垂向应力梯度方向扩展、并在所述裂隙发育区的边缘停止扩展，形成贯通所述目标顶板的垂向裂缝。本申请提出的技术方案，通过爆破与水力压裂的协同作用，实现厚硬顶板的立体切割与区域卸压，有效防控冲击地压灾害。
Smart Images
Figure CN122812622A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of rockburst relief technology, and in particular to a regional pressure relief method and system for blast-induced vertical crack propagation. Background Technology
[0002] Rockburst is one of the common dynamic disasters in coal mining. Especially when there is a thick and hard roof above the coal seam, as the working face advances, the thick and hard roof is difficult to collapse naturally, forming a large area of suspended roof. Once it suddenly breaks and collapses, it will release huge energy, which can easily induce rockburst accidents and seriously threaten the safe production of the mine.
[0003] Currently, conventional hydraulic fracturing technology is one of the main engineering methods for controlling rockburst in thick, hard roofs of coal mines. A typical implementation involves: first, constructing stress testing boreholes in the target area to determine the magnitude and direction of the three principal stresses using hydraulic fracturing or acoustic emission methods, thus identifying the direction of the maximum horizontal principal stress; then, arranging hydraulic fracturing boreholes along the direction of the maximum horizontal principal stress, and injecting high-pressure fracturing fluid using a segmented or layered fracturing process to force the rock mass to fracture along its natural dominant surface; finally, using ground microseismic monitoring and borehole television imaging, tracking the azimuth, length, and height of fracture propagation, and evaluating the pressure relief effect. However, the above-mentioned conventional hydraulic fracturing technology has the following shortcomings: First, the direction of fracture propagation is strictly controlled by the natural stress field. Since the maximum horizontal principal stress usually dominates in thick, hard roofs, hydraulic fractures mainly propagate horizontally, with limited vertical propagation capacity, making it difficult to increase the vertical height of the fractures and achieve large-scale vertical penetration of the roof. Second, conventional hydraulic fracturing can only achieve localized weakening of the roof, without fundamentally altering the integrity of the rock mass. The roof retains high integrity, the stress transmission path is not effectively cut off, and the pressure relief effect is unsatisfactory. Third, existing technologies lack quantitative control indicators for the coordinated operation of blasting and hydraulic fracturing, resulting in poor process stability and difficulty in achieving replicable and scalable application effects in engineering practice. Therefore, there is an urgent need to propose a regional pressure relief scheme that can actively guide hydraulic fractures to preferentially propagate vertically, achieve three-dimensional pressure relief of thick and hard roofs, and possess quantitative control indicators. Summary of the Invention
[0004] This application provides a regional pressure relief method and system for blasting-induced vertical crack propagation, which at least solves the technical problem that existing hydraulic fracturing technology is unable to achieve large-scale vertical through cracks in thick and hard roofs of coal mines, resulting in poor pressure relief effect and high risk of rockburst.
[0005] The first aspect of this application provides a regional pressure relief method for blast-induced vertical crack propagation, the method comprising:
[0006] Blasting holes are set in the target top rock layer, and then directional blasting is carried out through the blasting holes to form a vertical weak surface layer and an artificially induced stress field in the top rock layer; Multiple monitoring holes are set around the blast hole, and strain data after the blast is collected by triaxial strain sensors installed at different levels in the monitoring holes. Based on the finite element inversion algorithm, the full spatial distribution and vertical stress gradient of the artificially induced stress field are calculated according to the strain data. The stress values in the full spatial distribution are compared with the in-situ geostress benchmark values to obtain the relative stress variation amplitude at each location within the target top plate. Then, based on the relative stress variation amplitude, the target top plate is divided into a hydraulic fracture initiation zone, a fracture propagation acceleration zone, and a fracture arrest control zone. Hydraulic fracturing holes are set in the hydraulic fracture initiation zone. The spatial distance between the hydraulic fracturing holes and the blasting holes is determined by the critical spacing ratio K = L / R. Based on the spatial distance, hydraulic fracturing holes are set in the hydraulic fracture initiation zone, where R is the radius of the blasting-induced fracture development zone and K ranges from 0.85 to 0.95. Hydraulic fracturing is performed in the hydraulic fracturing hole, causing the hydraulic fracture to initiate in the fracturing zone, extend along the vertical stress gradient in the extension acceleration zone, and stop extending at the edge of the fracture development zone, forming a vertical fracture that penetrates the target top plate.
[0007] Preferably, the number of monitoring holes is 2 to 3, and the angle of each monitoring hole is different; One of the three-dimensional strain sensors is installed every 20m along the vertical direction in each of the monitoring holes, and the monitoring points cover the entire top layer of the target plate.
[0008] Furthermore, the directional blasting adopts a top-down segmented delayed detonation method; The blasting parameters include: a charge spacing of 3-5m, an inter-segment delay of 25-50ms, a charge decoupling coefficient of 1.8-2.2, a total charge weight to target top plate thickness ratio of 0.8-1.2kg / m, and a sealing hole length ≥15m.
[0009] Furthermore, the blasting holes are arranged in a multi-layered fan-shaped hole group of 3 to 5 layers, with an inclination angle of 60° to 75° and a hole depth covering the entire layer of the target pressure relief top plate.
[0010] Furthermore, the hydraulic fracture initiation zone is a region where the stress value decreases by 30% to 50% relative to the original geostress reference value; The crack propagation acceleration zone is the area where the stress value decreases by 10% to 20% relative to the original geostress reference value; The crack arrest control zone is the area where the stress value increases by 15% to 25% relative to the original ground stress reference value.
[0011] Furthermore, the radius of the blast-induced fracture development zone is determined by borehole television observation or ground microseismic monitoring, or by the inflection point where the stress changes from decreasing to increasing in the inverted stress field results.
[0012] A second aspect of this application provides a zone pressure relief system for blast-induced vertical crack propagation, comprising: The directional blasting module is used to set blasting holes in the target roof rock layer, and then carry out directional blasting through the blasting holes to form a vertical weak surface layer and an artificially induced stress field in the roof rock layer; The acquisition module is used to set up multiple monitoring holes around the blasting hole and collect strain data after the blasting is carried out through triaxial strain sensors installed at different levels in the monitoring holes; The calculation module is used to calculate the full-space distribution and vertical stress gradient of the artificially induced stress field based on the finite element inversion algorithm and the strain data. The division module is used to compare the stress values in the full spatial distribution with the in-situ geostress reference values to obtain the relative stress variation amplitude at each location within the target top plate. Then, based on the relative stress variation amplitude, the target top plate is divided into a hydraulic fracture initiation zone, a fracture propagation acceleration zone, and a fracture arrest control zone. The module is used to set up hydraulic fracturing holes in the hydraulic fracture initiation zone, determine the spatial distance between the hydraulic fracturing holes and the blasting holes using a critical spacing ratio K = L / R, and then set up hydraulic fracturing holes in the hydraulic fracture initiation zone based on the spatial distance, where R is the radius of the blasting-induced fracture development zone and K ranges from 0.85 to 0.95. The hydraulic fracturing module is used to perform hydraulic fracturing operations in the hydraulic fracturing hole, so that the hydraulic fractures are initiated sequentially through the fracture initiation zone, expand along the vertical stress gradient direction in the expansion acceleration zone, and stop expanding at the edge of the fracture development zone, forming a vertical fracture that penetrates the target top plate.
[0013] Furthermore, the number of monitoring holes is 2 to 3, and the angle of each monitoring hole is different; One of the three-dimensional strain sensors is installed every 20m along the vertical direction in each of the monitoring holes, and the monitoring points cover the entire top layer of the target plate.
[0014] A third aspect of this application provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, it implements the method described in the first aspect embodiment.
[0015] A fourth aspect of this application provides a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the method described in the first aspect.
[0016] The technical solutions provided by the embodiments of this application bring at least the following beneficial effects: This application proposes a regional stress relief method and system for blasting-induced vertical crack propagation. The method includes: setting blasting holes in the target roof strata, and then performing directional blasting through the blasting holes to form a vertically weak surface layer and an artificially induced stress field within the roof strata; setting multiple monitoring holes around the blasting holes, and collecting strain data after the blasting through triaxial strain sensors installed at different layers within the monitoring holes; calculating the full-space distribution and vertical stress gradient of the artificially induced stress field based on the finite element inversion algorithm and the strain data; comparing the stress values in the full-space distribution with the in-situ geostress reference value to obtain the relative stress change amplitude at each location within the target roof strata, and then calculating the stress gradient based on the stress gradient. For varying degrees of change, the target roof is divided into a hydraulic fracture initiation zone, a fracture propagation acceleration zone, and a fracture arrest control zone. Hydraulic fracturing holes are installed within the hydraulic fracture initiation zone. The spatial distance between the hydraulic fracturing holes and the blasting holes is determined by a critical spacing ratio K = L / R. Based on this spatial distance, hydraulic fracturing holes are installed within the hydraulic fracture initiation zone, where R is the radius of the blast-induced fracture development zone, and K ranges from 0.85 to 0.95. Hydraulic fracturing operations are performed within the hydraulic fracturing holes, causing the hydraulic fractures to initiate sequentially in the initiation zone, propagate along the vertical stress gradient direction in the propagation acceleration zone, and stop propagating at the edge of the fracture development zone, forming a vertical fracture penetrating the target roof. The technical solution proposed in this application achieves three-dimensional cutting and regional pressure relief of thick, hard roofs through the synergistic effect of blasting and hydraulic fracturing, effectively preventing rockburst disasters.
[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description
[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of a regional decompression method for blast-induced vertical crack propagation according to an embodiment of this application; Figure 2 This is a schematic diagram showing the positions of the ore base, blasting hole, blasting charge, monitoring hole, and triaxial strain sensor according to an embodiment of this application; Figure 3 This is a structural diagram of a zone pressure relief system for blast-induced vertical crack propagation according to an embodiment of this application; Figure Labels 1. Ore base; 2. Blasting hole; 3. Blasting charge; 4. Monitoring hole; 5. Triaxial strain sensor. Detailed Implementation
[0019] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.
[0020] This application proposes a regional stress relief method and system for blasting-induced vertical crack propagation. The method includes: setting blasting holes in the target roof strata, and then performing directional blasting through the blasting holes to form a vertically weak surface layer and an artificially induced stress field within the roof strata; setting multiple monitoring holes around the blasting holes, and collecting strain data after the blasting through triaxial strain sensors installed at different layers within the monitoring holes; calculating the full-space distribution and vertical stress gradient of the artificially induced stress field based on the finite element inversion algorithm and the strain data; comparing the stress values in the full-space distribution with the in-situ geostress reference value to obtain the relative stress change amplitude at each location within the target roof strata, and then calculating the stress gradient based on the stress gradient. For varying degrees of change, the target roof is divided into a hydraulic fracture initiation zone, a fracture propagation acceleration zone, and a fracture arrest control zone. Hydraulic fracturing holes are installed within the hydraulic fracture initiation zone. The spatial distance between the hydraulic fracturing holes and the blasting holes is determined by a critical spacing ratio K = L / R. Based on this spatial distance, hydraulic fracturing holes are installed within the hydraulic fracture initiation zone, where R is the radius of the blast-induced fracture development zone, and K ranges from 0.85 to 0.95. Hydraulic fracturing operations are performed within the hydraulic fracturing holes, causing the hydraulic fractures to initiate sequentially in the initiation zone, propagate along the vertical stress gradient direction in the propagation acceleration zone, and stop propagating at the edge of the fracture development zone, forming a vertical fracture penetrating the target roof. The technical solution proposed in this application achieves three-dimensional cutting and regional pressure relief of thick, hard roofs through the synergistic effect of blasting and hydraulic fracturing, effectively preventing rockburst disasters.
[0021] The following description, with reference to the accompanying drawings, describes a regional pressure relief method and system for blasting-induced vertical crack propagation according to an embodiment of this application.
[0022] Example 1 Figure 1 This is a flowchart of a zone decompression method for blast-induced vertical crack propagation according to an embodiment of this application, as shown below. Figure 1As shown, the method includes: Step 1: Set blasting holes in the target roof rock layer, and then carry out directional blasting through the blasting holes to form a vertical weak surface layer and an artificially induced stress field in the roof rock layer; It should be noted that, as Figure 2 The diagram shows the locations of the following components involved in the implementation of this scheme: ore base 1, blasting hole 2, blasting charge 3, monitoring hole 4, and triaxial strain sensor 5.
[0023] like Figure 2 As shown, multiple vertical blasting holes 2 are opened on the ore base 1, and each vertical blasting hole 2 is filled with a blasting charge 3. Multiple monitoring holes 4 are opened on the ore base 1, and the angles of the multiple monitoring holes 4 are different. Each of the multiple monitoring holes 4 is equipped with a triaxial strain sensor 5, and the distance between the multiple triaxial strain sensors 5 is 20m.
[0024] In this embodiment of the disclosure, the directional blasting adopts a top-down segmented delayed initiation method; The blasting parameters include: a charge spacing of 3-5m, an inter-segment delay of 25-50ms, a charge decoupling coefficient of 1.8-2.2, a total charge weight to target top plate thickness ratio of 0.8-1.2kg / m, and a sealing hole length ≥15m.
[0025] In this embodiment, the blasting holes are arranged in a multi-layered fan-shaped hole group of 3 to 5 layers, with an inclination angle of 60° to 75° and a hole depth covering the entire layer of the target pressure relief top plate.
[0026] It should be noted that the formation of a vertical weak layer and an artificially induced stress field within the top stratum is achieved by controlling the directional blasting parameters. Specifically, a segmented, delayed initiation method from top to bottom is adopted, with the spacing between explosive charges controlled at 3–5 m to ensure the continuous vertical penetration of adjacent blast fractures, forming a weak layer. The inter-segment delay is controlled at 25–50 ms to guide the continuous expansion of cracks from top to bottom, avoiding stress wave interference. The decoupling coefficient of the explosive charge is controlled at 1.8–2.2 to ensure that the blasting energy acts uniformly along the borehole wall, forming dense micro-fractures without completely breaking the rock mass. The ratio of total charge to target roof thickness is controlled between 0.8 and 1.2 kg / m to ensure that the blasting energy covers the entire target roof layer. The sealing length is controlled to ≥15m to ensure that the blasting energy is concentrated in the target layer inside the hole. Through the synergistic effect of the above blasting parameters, a directional vertical weak surface layer with dense vertical micro-fractures is formed in the roof rock layer, but the rock mass has not completely collapsed. At the same time, due to the vertical segmented release of blasting energy, the stress state at different heights along the vertical direction changes to different degrees, forming a vertically distributed artificial induced stress gradient field.
[0027] The resulting vertical weak surface layer and artificially induced stress field play the following roles in subsequent hydraulic fracturing steps: First, strain data after blasting is collected by a triaxial strain sensor in the monitoring borehole, and the full-space distribution of the artificially induced stress field and the vertical stress gradient are calculated based on the finite element inversion algorithm. The calculated stress distribution is compared with the in-situ geostress benchmark value, and the target roof is divided into a hydraulic fracture initiation zone, a fracture propagation acceleration zone, and a fracture arrest control zone according to the relative stress change amplitude. Hydraulic fracturing boreholes are constructed in the fracture initiation zone, and the relative positions of the fracturing boreholes and blasting boreholes are controlled by the critical spacing ratio K = L / R. During hydraulic fracturing, the vertical weak surface layer provides a preferential physical path for the hydraulic fracture to propagate, while the vertical stress gradient exerts mechanical guidance on the hydraulic fracture, causing it to propagate preferentially along the vertical direction. When the hydraulic fracture propagates to the fracture arrest control zone (i.e., the edge of the fracture development zone), the fracture automatically stops propagating due to the relative increase in stress in this area, thereby avoiding excessive penetration and leakage of fracturing fluid. Therefore, the formation of the vertical weak surface layer and the artificially induced stress field is the logical starting point and technical foundation for subsequent directional propagation of hydraulic fractures, functional zoning, fracturing hole location, and control of fracture initiation and arrest.
[0028] Step 2: Set up multiple monitoring holes around the blast hole, and collect strain data after the blasting by installing triaxial strain sensors at different levels in the monitoring holes; In this embodiment of the disclosure, the number of monitoring holes is 2 to 3, and the angle of each monitoring hole is different; One of the three-dimensional strain sensors is installed every 20m along the vertical direction in each of the monitoring holes, and the monitoring points cover the entire top layer of the target plate.
[0029] Step 3: Based on the finite element inversion algorithm, calculate the full spatial distribution and vertical stress gradient of the artificially induced stress field according to the strain data; The specific implementation method is as follows: First, a three-dimensional geomechanical model of the target roof strata is established, and the strain data collected by the triaxial strain sensors at each measuring point in the monitoring borehole is used as the input boundary conditions. Second, based on the finite element inversion algorithm, with the measured strain data as the objective function, the stress field distribution that minimizes the error between the theoretically calculated strain and the measured strain is solved through iterative inversion calculation, thereby obtaining the stress components of each node in the entire target roof area, constituting the full spatial distribution of the artificially induced stress field. Then, the stress values at different elevations are extracted along the vertical direction, and the rate of change of stress along the vertical direction is calculated to obtain the vertical stress gradient. Finally, by comparing the full spatial distribution stress values obtained by inversion with the in-situ geostress benchmark values of each measuring point, the spatial distribution law of the relative stress variation amplitude can be obtained.
[0030] Step 4: Compare the stress values in the full spatial distribution with the in-situ ground stress reference values to obtain the relative stress variation amplitude at each location within the target top plate. Then, based on the relative stress variation amplitude, divide the target top plate into a hydraulic fracture initiation zone, a fracture propagation acceleration zone, and a fracture arrest control zone. In this embodiment of the disclosure, the hydraulic fracture initiation zone is a region where the stress value decreases by 30% to 50% relative to the original geostress reference value; The crack propagation acceleration zone is the area where the stress value decreases by 10% to 20% relative to the original geostress reference value; The crack arrest control zone is the area where the stress value increases by 15% to 25% relative to the original ground stress reference value.
[0031] Step 5: Set up hydraulic fracturing holes in the hydraulic fracture initiation zone, determine the spatial distance between the hydraulic fracturing holes and the blasting holes using the critical spacing ratio K = L / R, and set up hydraulic fracturing holes in the hydraulic fracture initiation zone based on the spatial distance, where R is the radius of the blasting-induced fracture development zone, and K ranges from 0.85 to 0.95. In this embodiment of the disclosure, the radius of the blast-induced fracture development zone is determined by borehole television observation or ground microseismic monitoring, or by the inflection point where the stress changes from decreasing to increasing in the inversion results of the induced stress field.
[0032] It should be noted that the blasting hole and the hydraulic fracturing hole are dedicated boreholes constructed independently. The spatial distance between them is precisely quantified and controlled using the critical distance ratio as a core indicator. The core design principle is as follows: Through numerical simulation and field test verification, the radius R of the blast-induced fracture development zone and the ultimate propagation range of the hydraulic fracturing fracture are determined respectively. The spatial distance between the hydraulic fracturing hole and the blasting hole is defined as the critical distance L. The critical distance ratio K is further defined as L / R, with an optimal value range of 0.85 to 0.95. The control effects of different value ranges are as follows: When K < 0.85, hydraulic fractures are prone to directly enter the fracture development zone, causing excessive fracture penetration and leading to problems such as fracturing fluid leakage. When K = 0.85 to 0.95, hydraulic fractures can stably extend vertically under the guidance of the blast-induced vertical stress gradient and accurately stop at the edge of the fracture development zone, taking into account both directional extension effect and construction safety. When K > 0.95, the stress gradient guidance effect is insufficient, the vertical extension distance of hydraulic fractures is insufficient, the prefabricated fracture initiation zone cannot be fully utilized, and the pressure relief modification effect is limited.
[0033] The edge of the blast-induced fracture development zone can be determined by borehole television observation and ground microseismic monitoring, or by the inflection point where the stress changes from decreasing to increasing in the inversion results of the induced stress field, which can improve the accuracy of the observation data.
[0034] Step 6: Perform hydraulic fracturing operations in the hydraulic fracturing hole, so that the hydraulic fractures sequentially initiate in the fracturing zone, extend along the vertical stress gradient in the expansion acceleration zone, and stop extending at the edge of the fracture development zone, forming a vertical fracture that penetrates the target top plate.
[0035] It should be noted that the critical spacing ratio is used as the core control index to determine the optimal spatial spacing between hydraulic fracturing holes and blasting holes. Hydraulic fracturing holes are constructed and layered or segmented hydraulic fracturing operations are carried out. Through the dual guiding effect of the vertical weak surface layer and stress gradient, the hydraulic fractures are guided to expand preferentially along the vertical direction, and the thick hard top plate is three-dimensionally cut into block structures to achieve regional pressure relief.
[0036] After hydraulic fracturing, vertical through-cracks are formed that penetrate multiple layers of the top plate, cutting the thick and hard top plate into regular block structures. This causes the stress in the overlying strata to be transferred from hard to soft, achieving large-scale pressure relief of the thick and hard top plate.
[0037] In the target area, a multi-index joint evaluation method was used to comprehensively evaluate the vertical crack penetration effect and the regional stress relief effect through borehole inspection. Specifically, this included: determining the vertical crack penetration height through borehole television imaging observation and ground microseismic monitoring; evaluating the roof rock mass integrity index through borehole television imaging observation and rock mass acoustic wave velocity testing; and monitoring the roof periodic pressure intensity and periodic pressure step distance in real time through the working face online mine pressure monitoring system. The test results of the above four indicators were compared with the original data before the implementation of this method. If the vertical crack penetration height significantly increased, the roof rock mass integrity index significantly decreased, and both the periodic pressure intensity and periodic pressure step distance significantly decreased, then the regional stress relief effect was deemed satisfactory.
[0038] This embodiment addresses the need for rockburst prevention in thick, hard roofs of coal mines. First, directional blasting creates a pre-existing vertical weak layer and a non-uniform artificially induced stress field within the roof strata. Then, hydraulic fracturing is performed. Utilizing the combined physical guidance of the pre-existing vertical weak layer and the mechanical guidance of the blast-induced vertical stress gradient, hydraulic fractures are guided to preferentially extend vertically, forming high-height, vertically penetrating fractures that run through multiple layers of the roof. The spatial positions of the blast holes and fracturing holes are precisely controlled by a critical spacing ratio to prevent excessive fracture penetration. Ultimately, the entire thick, hard roof is three-dimensionally cut. Its blocky structure facilitates the transformation of stress transmission from "hard" to "soft" in the overlying strata, enabling large-scale stress relief and proactive prevention of rockburst disasters in thick, hard roofs. The quantitative control index of the spacing between blasting and hydraulic fracturing operations, namely the critical spacing ratio, avoids fracturing fluid leakage, ensuring stable and reliable processes and significantly improving the stability and reliability of collaborative operations. It possesses replicable and scalable engineering application value. Furthermore, it achieves three-dimensional roof shearing, fracturing the thick, hard roof into layers and small blocks for timely collapse and filling, thus cutting off stress transmission paths and achieving large-scale stress relief. The technical solution proposed in this embodiment has the following beneficial effects: A breakthrough has been achieved in shifting the crack propagation from "passive compliance" to "active control." By pre-constructing a vertical weak surface layer and a non-uniform artificially induced stress field in the top rock strata through directional blasting, the hydraulic cracks are actively guided to propagate preferentially along the vertical direction. This eliminates the passive dependence on the natural geostress field and significantly improves the controllability of the crack direction.
[0039] Significantly enhancing the vertical crack propagation capacity and achieving three-dimensional pressure relief, this invention enables hydraulic cracks to achieve a vertical penetration height of ≥30m, forming a high-height vertical through crack that penetrates multiple layers of the top plate, and three-dimensionally cutting the thick and hard top plate into a block structure, thus achieving an upgrade from "planar transformation" to "three-dimensional pressure relief".
[0040] By cutting off the hard stress transmission path and achieving pressure relief over a large area, the stress in the overlying strata is transformed from "hard transmission" to "soft transmission" through three-dimensional cutting of the thick and hard roof. The roof collapses and fills the goaf in time, effectively cutting off the stress transmission path and reducing the risk of rockburst.
[0041] A quantitative control index was established to improve the stability and reliability of the process. A quantitative control system with "critical spacing ratio K = L / R" as the core was proposed. The optimal value range is 0.85 to 0.95. It can accurately control the spatial position of the blasting hole and the hydraulic fracturing hole, avoid excessive fracture penetration or insufficient guidance, prevent fracturing fluid leakage, and ensure that the process is stable and reliable. It has replicable and scalable engineering application value.
[0042] The combined evaluation of multiple indicators ensures that the effects can be quantified and verified. By using methods such as borehole television, microseismic monitoring, acoustic testing, and mine pressure monitoring, the vertical crack penetration height, roof integrity index, periodic pressure intensity, and step distance are comprehensively evaluated to ensure that the pressure relief effect can be quantified and verified.
[0043] This invention improves the safety of coal mining by effectively preventing rockburst disasters caused by thick and hard roofs, reducing the risk of sudden roof collapse, and ensuring the safety of mine personnel and equipment, thus having significant social and economic benefits.
[0044] In summary, the regional depressurization method for blasting-induced vertical crack propagation proposed in this embodiment achieves three-dimensional cutting and regional depressurization of thick and hard roofs through the synergistic effect of blasting and hydraulic fracturing, effectively preventing rockburst disasters.
[0045] Example 2 Figure 3 This is a structural diagram of a zone pressure relief system for blast-induced vertical crack propagation according to an embodiment of this application, as shown below. Figure 3 As shown, the system includes: The directional blasting module 100 is used to set blasting holes in the target roof rock layer, and then carry out directional blasting through the blasting holes to form a vertical weak surface layer and an artificially induced stress field in the roof rock layer. The directional blasting adopts a segmented delayed detonation method from top to bottom; The blasting parameters include: charge spacing of 3-5m, inter-segment delay of 25-50ms, charge decoupling coefficient of 1.8-2.2, total charge weight to target top plate thickness ratio of 0.8-1.2kg / m, and sealing hole length ≥15m.
[0046] The blasting holes are arranged in a multi-layered fan-shaped group of 3 to 5 holes, with an inclination angle of 60° to 75° and a hole depth covering the entire layer of the target pressure relief top plate.
[0047] The acquisition module 200 is used to set up multiple monitoring holes around the blasting hole and acquire strain data after the blasting is carried out through triaxial strain sensors installed at different levels in the monitoring holes; The number of monitoring holes is 2 to 3, and the angle of each monitoring hole is different; One of the three-dimensional strain sensors is installed every 20m along the vertical direction in each of the monitoring holes, and the monitoring points cover the entire top layer of the target plate.
[0048] The calculation module 300 is used to calculate the full-space distribution and vertical stress gradient of the artificially induced stress field based on the finite element inversion algorithm and the strain data. The division module 400 is used to compare the stress values in the full spatial distribution with the in-situ geostress reference values to obtain the relative stress change amplitude at each location within the target top plate. Then, based on the relative stress change amplitude, the target top plate is divided into a hydraulic fracture initiation zone, a fracture propagation acceleration zone, and a fracture arrest control zone. The hydraulic fracture initiation zone is the area where the stress value decreases by 30% to 50% relative to the original geostress benchmark value. The crack propagation acceleration zone is the area where the stress value decreases by 10% to 20% relative to the original geostress reference value; The crack arrest control zone is the area where the stress value increases by 15% to 25% relative to the original ground stress reference value.
[0049] The module 500 is used to set up hydraulic fracturing holes in the hydraulic fracture initiation zone, determine the spatial distance between the hydraulic fracturing holes and the blasting holes using the critical spacing ratio K = L / R, and then set up hydraulic fracturing holes in the hydraulic fracture initiation zone based on the spatial distance, where R is the radius of the blasting-induced fracture development zone and K ranges from 0.85 to 0.95. The radius of the blast-induced fracture development zone is determined by borehole television observation or ground microseismic monitoring, or by the inflection point where the stress changes from decreasing to increasing in the inverted stress field results.
[0050] The hydraulic fracturing module 600 is used to perform hydraulic fracturing operations in the hydraulic fracturing hole, so that the hydraulic fractures are initiated sequentially through the fracture initiation zone, expand along the vertical stress gradient direction in the expansion acceleration zone, and stop expanding at the edge of the fracture development zone, forming a vertical fracture that penetrates the target top plate.
[0051] In summary, the regional pressure relief system proposed in this embodiment, which induces vertical crack propagation through blasting, achieves three-dimensional cutting and regional pressure relief of thick and hard roof through the synergistic effect of blasting and hydraulic fracturing, effectively preventing rockburst disasters.
[0052] Example 3 To implement the above embodiments, this disclosure also proposes an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, it implements the method described in Embodiment 1.
[0053] Example 4 To implement the above embodiments, this disclosure also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in Embodiment 1.
[0054] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0055] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.
[0056] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.
Claims
1. A method for regional pressure relief inducing vertical crack propagation by blasting, characterized in that, The method includes: Blasting holes are set in the target top rock layer, and then directional blasting is carried out through the blasting holes to form a vertical weak surface layer and an artificially induced stress field in the top rock layer. Multiple monitoring holes are set around the blast hole, and strain data after the blast is collected by triaxial strain sensors installed at different levels in the monitoring holes. Based on the finite element inversion algorithm, the full spatial distribution and vertical stress gradient of the artificially induced stress field are calculated according to the strain data. The stress values in the full spatial distribution are compared with the in-situ geostress benchmark values to obtain the relative stress variation amplitude at each location within the target top plate. Then, based on the relative stress variation amplitude, the target top plate is divided into a hydraulic fracture initiation zone, a fracture propagation acceleration zone, and a fracture arrest control zone. Hydraulic fracturing holes are set in the hydraulic fracture initiation zone. The spatial distance between the hydraulic fracturing holes and the blasting holes is determined by the critical spacing ratio K = L / R. Based on the spatial distance, hydraulic fracturing holes are set in the hydraulic fracture initiation zone, where R is the radius of the blasting-induced fracture development zone and K ranges from 0.85 to 0.
95. Hydraulic fracturing is performed in the hydraulic fracturing hole, causing the hydraulic fracture to initiate in the fracturing zone, extend along the vertical stress gradient in the extension acceleration zone, and stop extending at the edge of the fracture development zone, forming a vertical fracture that penetrates the target top plate.
2. The method as described in claim 1, characterized in that, The number of monitoring holes is 2 to 3, and the angle of each monitoring hole is different; One of the three-dimensional strain sensors is installed every 20m along the vertical direction in each of the monitoring holes, and the monitoring points cover the entire top layer of the target plate.
3. The method as described in claim 2, characterized in that, The directional blasting adopts a segmented delayed detonation method from top to bottom; The blasting parameters include: a charge spacing of 3-5m, an inter-segment delay of 25-50ms, a charge decoupling coefficient of 1.8-2.2, a total charge weight to target top plate thickness ratio of 0.8-1.2kg / m, and a sealing hole length ≥15m.
4. The method as described in claim 3, characterized in that, The blasting holes are arranged in a multi-layered fan-shaped group of 3 to 5 holes, with an inclination angle of 60° to 75° and a hole depth covering the entire layer of the target pressure relief top plate.
5. The method as described in claim 4, characterized in that, The hydraulic fracture initiation zone is the area where the stress value decreases by 30% to 50% relative to the original ground stress reference value; The crack propagation acceleration zone is the area where the stress value decreases by 10% to 20% relative to the original geostress reference value; The crack arrest control zone is the area where the stress value increases by 15% to 25% relative to the original ground stress reference value.
6. The method as described in claim 5, characterized in that, The radius of the blast-induced fracture development zone is determined by borehole television observation or ground microseismic monitoring, or by the inflection point where the stress changes from decreasing to increasing in the inversion results of the induced stress field.
7. A zone pressure relief system for blast-induced vertical crack propagation, characterized in that, The system includes: The directional blasting module is used to set blasting holes in the target roof rock layer, and then carry out directional blasting through the blasting holes to form a vertical weak surface layer and an artificially induced stress field in the roof rock layer; The acquisition module is used to set up multiple monitoring holes around the blasting hole and collect strain data after the blasting is carried out through triaxial strain sensors installed at different levels in the monitoring holes; The calculation module is used to calculate the full-space distribution and vertical stress gradient of the artificially induced stress field based on the finite element inversion algorithm and the strain data. The division module is used to compare the stress values in the full spatial distribution with the in-situ geostress reference values to obtain the relative stress variation amplitude at each location within the target top plate. Then, based on the relative stress variation amplitude, the target top plate is divided into a hydraulic fracture initiation zone, a fracture propagation acceleration zone, and a fracture arrest control zone. The module is used to set up hydraulic fracturing holes in the hydraulic fracture initiation zone, determine the spatial distance between the hydraulic fracturing holes and the blasting holes using a critical spacing ratio K = L / R, and then set up hydraulic fracturing holes in the hydraulic fracture initiation zone based on the spatial distance, where R is the radius of the blasting-induced fracture development zone and K ranges from 0.85 to 0.
95. The hydraulic fracturing module is used to perform hydraulic fracturing operations in the hydraulic fracturing hole, so that the hydraulic fractures are initiated sequentially through the fracture initiation zone, expand along the vertical stress gradient direction in the expansion acceleration zone, and stop expanding at the edge of the fracture development zone, forming a vertical fracture that penetrates the target top plate.
8. The system as described in claim 7, characterized in that, The number of monitoring holes is 2 to 3, and the angle of each monitoring hole is different; One of the three-dimensional strain sensors is installed every 20m along the vertical direction in each of the monitoring holes, and the monitoring points cover the entire top layer of the target plate.
9. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and capable of running on the processor, wherein the processor, when executing the program, implements the method as described in any one of claims 1-6.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1-6.