Rock burst drilling pressure relief method

Abstract

The invention provides a rock burst drilling pressure relief method, and relates to the technical field of rock burst prevention and control. The method comprises the steps that the maximum principal stress direction of an area needing pressure relief is obtained, a parallel drill hole group is constructed on a roadway coal wall in the maximum principal stress direction, and a stress concentration area of the area needing pressure relief is covered with the parallel drill hole group. According to the method, construction is conducted in the maximum principal stress direction of the area needing pressure relief during drilling, compared with drilling directly perpendicular to the roadway coal wall without considering the stress direction, the clamping effect of surrounding rock can be reduced to the maximum extent, and therefore the pressure relief effect is good, namely the control effect on rock burst is good; the method is not only suitable for areas with medium and low stress and stable geological conditions, but also suitable for special areas with high-stress and complex-stress structures and the like.

Description

Technical Field

[0001] This invention relates to the field of rockburst prevention and control technology, and more specifically, to a method for relieving rockburst pressure through drilling. Background Technology

[0002] like Figure 1 As shown, current rockburst prevention technology based on boreholes is used to relieve pressure on coal and rock masses. This typically involves drilling a series of parallel and perpendicular boreholes into the coal face, such as the sides of the mining roadway, the working face cut, or the coal wall of the mining face. The borehole depth usually covers the stress concentration zone, causing cracks and plastic deformation in the coal body around the boreholes. This releases the accumulated elastic energy, reduces the stress concentration and energy storage capacity of the coal body, thereby eliminating or reducing the risk of rockburst and achieving the purpose of pressure relief.

[0003] However, the above methods are only applicable under relatively stable geological conditions and moderate or lower stress concentration. In other cases, such as when the coal body is hard and the tectonic stress field is disordered, it is not possible to obtain good stress data on site or the stress field is disordered. Therefore, it is difficult to efficiently deploy boreholes to the target area. Although the above methods can solve the on-site problems to a certain extent, the pressure relief effect is poor and the prevention and control effect is poor. At the same time, it will also generate significant safety hazards or cause blind construction, which will reduce the prevention and control efficiency. Therefore, it is difficult to meet the needs of the site. Summary of the Invention

[0004] The purpose of this invention is to provide a method for relieving pressure in rockburst boreholes, so as to solve the technical problems of limited applicability and insufficient pressure relief effect of existing rockburst borehole pressure relief methods.

[0005] The rockburst drilling method provided by the present invention obtains the direction of the maximum principal stress in the area to be relieved, and constructs a group of parallel boreholes in the coal wall of the roadway along the direction of the maximum principal stress, so that the group of parallel boreholes covers the stress concentration area of ​​the area to be relieved.

[0006] Furthermore, when obtaining the direction of the maximum principal stress in the area to be relieved, if it is impossible to perform in-situ stress detection, or if the detected in-situ stress field is disordered, a group of fan-shaped boreholes is constructed in the horizontal plane perpendicular to the coal wall of the roadway and in the vertical plane where the coal wall of the roadway is located. The direction of the maximum principal stress in the area to be relieved is inferred based on the drilling depth of each borehole in the group of fan-shaped boreholes.

[0007] Furthermore, if the difference in the depth of each borehole in the fan-shaped borehole group exceeds a preset depth difference, then the direction of the borehole with the longest depth is regarded as the direction of the maximum principal stress in the area to be relieved.

[0008] Furthermore, if the difference in the drilling depth of each borehole in the fan-shaped borehole group does not exceed the preset depth difference, then the direction perpendicular to the coal wall of the roadway is regarded as the direction of the maximum principal stress in the area requiring stress relief.

[0009] Furthermore, if the direction of the maximum horizontal principal stress in the pressure relief area is clearly related to the roadway axis, and the inclination angle of the stress field is less than the preset inclination angle, then the direction of the maximum horizontal principal stress is approximated as the direction of the maximum principal stress.

[0010] Furthermore, in the horizontal plane, the design depth L of the parallel borehole group must satisfy L=l / sinθ, where l is the vertical horizontal distance between the pressure relief area and the roadway coal wall, and the vertical horizontal distance is the distance from the coal wall surface to the horizontal projection of the target pressure relief area in the direction perpendicular to the coal wall within the roadway design cross section; θ is the angle between the direction of the maximum principal stress and the roadway coal wall.

[0011] Furthermore, the borehole ends of the parallel borehole group must exceed the peak position of the coal seam support pressure in the roadway. If the coal seam mining thickness is less than 3.5m, the borehole depth shall not be less than 15m; if the coal seam mining thickness is greater than or equal to 3.5m and less than or equal to 8m, the borehole depth shall not be less than 20m; if the coal seam mining thickness is greater than 8m, the borehole depth shall not be less than 25m; the borehole depth at the face of the tunneling roadway shall not be less than 20m.

[0012] Furthermore, the holes in the parallel borehole group are large-diameter holes, with a diameter of not less than 100 mm.

[0013] Furthermore, when encountering hard coal and rock masses that make direct drilling difficult, a step-by-step process of pilot hole drilling followed by hole enlargement is adopted to construct the borehole.

[0014] Furthermore, during the drilling process using a step-by-step method, a large-diameter variable-diameter drill bit is used for hole enlargement.

[0015] The pressure relief method for rockburst drilling provided by this invention can produce the following beneficial effects: The rockburst drilling and stress relief method provided by this invention drills along the direction of the maximum principal stress in the area to be relieved. Compared with drilling directly perpendicular to the coal wall of the roadway without considering the stress direction, it can minimize the supporting effect of the surrounding rock, so the stress relief effect is good, that is, the prevention and control effect of rockburst is good. It is not only suitable for areas with medium and low stress and stable geological conditions, but also for special areas with high stress and complex stress structures. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the borehole layout in an existing rockburst pressure relief borehole drilling method. Figure 2 A schematic diagram of the parallel hole layout in the horizontal plane for the rockburst drilling pressure relief method provided in the embodiment of the present invention; Figure 3 This is a schematic diagram of the rockburst drilling stress relief method provided in the embodiment of the present invention, showing a fan-shaped hole layout in the horizontal plane. The geological conditions in the stress relief area are unstable and the stress field is disordered. Figure 4 This is a schematic diagram of a fan-shaped borehole layout in a horizontal plane for the rockburst drilling decompression method provided in an embodiment of the present invention. The geological conditions in the decompression area in the diagram are stable. Figure 5 A schematic diagram of the fan-shaped hole layout in a vertical plane for the rockburst drilling pressure relief method provided in the embodiments of the present invention; Figure 6 This is a schematic diagram of the step-by-step drilling method for relieving pressure from impact ground pressure provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] This embodiment provides a method for stress relief through drilling in the rockburst zone. Specifically, it involves obtaining the direction of the maximum principal stress in the area to be relieved, and constructing a group of parallel boreholes along the direction of the maximum principal stress in the coal wall of the roadway, ensuring that the group of parallel boreholes covers the stress concentration area of ​​the area to be relieved. Figure 2 As shown.

[0020] The rockburst drilling and stress relief method provided in this embodiment involves drilling along the direction of the maximum principal stress in the area to be relieved. Compared with drilling directly perpendicular to the coal wall of the roadway without considering the stress direction, this method can minimize the supporting effect of the surrounding rock, thus achieving a better stress relief effect and a better prevention and control effect against rockburst. It is suitable not only for areas with medium and low stress and stable geological conditions, but also for special areas with high stress and complex stress structures.

[0021] Specifically, in this embodiment, when obtaining the direction of the maximum principal stress in the area to be relieved, if it is impossible to perform in-situ stress detection, or if the detected in-situ stress field is disordered, a group of fan-shaped boreholes is constructed in the horizontal plane perpendicular to the coal wall of the roadway and in the vertical plane where the coal wall of the roadway is located. The direction of the maximum principal stress in the area to be relieved is inferred based on the drilling depth of each borehole in the group of fan-shaped boreholes.

[0022] Figure 3 and Figure 4 These are all schematic diagrams showing fan-shaped perforations within a horizontal plane perpendicular to the coal face of the roadway. Figure 5 This diagram illustrates a fan-shaped borehole layout within the vertical plane of the coal face in the roadway. In actual construction, the layout can be adjusted according to specific circumstances. Specifically, if the stress field is known to be predominantly horizontal, a group of horizontal fan-shaped boreholes can be constructed only in the horizontal plane; if the stress field is known to be predominantly vertical, a group of vertical fan-shaped boreholes can be constructed only in the vertical plane; otherwise, both horizontal and vertical fan-shaped boreholes can be constructed in the horizontal and vertical planes to better relieve pressure or find the direction of maximum principal stress in three-dimensional space.

[0023] The following example, using the construction of a fan-shaped borehole group in a horizontal plane, illustrates how to infer the direction of the maximum principal stress based on the borehole depth. Figure 3 As shown, if the difference in drilling depth among the boreholes in the fan-shaped borehole group exceeds a preset depth difference, then the direction of the borehole with the longest drilling depth is considered as the direction of the maximum principal stress in the area requiring stress relief. However, if... Figure 4 As shown, if the difference in the drilling depth of each borehole in the fan-shaped borehole group does not exceed the preset depth difference, then the direction perpendicular to the coal wall of the roadway is regarded as the direction of the maximum principal stress in the area to be relieved.

[0024] That is, in the absence of geostress data, it is possible to construct fan-shaped boreholes within the coal seam of the mining face, such as... Figures 3 to 5 As shown. The specific angle of the fan-shaped aperture arrangement can be optimized and adjusted according to the site geological conditions and stress distribution characteristics, such as... Figures 3 to 5 In this process, the included angle between two adjacent boreholes is sometimes 45°, sometimes 30°, and sometimes 5°. Of course, other angles are also possible.

[0025] In actual drilling operations, such as Figure 4 As shown, if the depths of each borehole tend to be consistent and the coal seam itself has good drillability, the drilling process will be relatively smooth. Under these conditions, to balance pressure relief, construction efficiency, and economy, drilling in a direction perpendicular to the coal wall of the roadway can be prioritized. After construction, it will be connected with... Figure 6 Similarly, this direction is conducive to achieving uniformity in borehole layout and standardization of construction operations, simplifying construction processes and reducing operating costs to the greatest extent possible while ensuring an effective pressure relief range.

[0026] And if... Figure 3 As shown, there are significant differences in the actual borehole depths. Some boreholes experienced low drilling resistance and were successfully completed, while others encountered difficulties and shorter drilling depths due to geological conditions such as the high hardness of the coal and rock mass. This resulted in a fan-shaped group of boreholes with varying depths. Based on elastoplastic mechanics theory and field engineering practice, it is evident that in this situation, the direction of the borehole with the longest drilling depth is usually parallel to or closest to the direction of the maximum principal stress in the coal seam (e.g., ...). Figure 3 As shown, assuming σ1 is the direction of the maximum principal stress, the direction of the longest borehole advance is considered the direction of the maximum principal stress. In this case, to balance construction economy and stress relief, the borehole layout strategy in this area can be optimized, changing from a fan-shaped layout to a group of parallel boreholes drilled along the direction of the longest advance (i.e., approximately the direction of the maximum principal stress). This arrangement facilitates the synergistic effect of the borehole group on the high stress transmission path, achieving concentrated stress relief and efficient energy release, thereby improving the overall effectiveness and maximization of regional stress relief while controlling costs.

[0027] like Figure 2 As shown in this embodiment, if the direction of the maximum horizontal principal stress in the area requiring stress relief has a clear relationship with the roadway axis, and the inclination angle of the stress field is less than the preset inclination angle, then the stress field is considered to be dominated by horizontal forces, and the direction of the maximum horizontal principal stress is approximated as the direction of the maximum principal stress. A group of parallel boreholes is then constructed in the horizontal plane. That is, when the regional stress field is relatively stable, and the direction of the maximum horizontal principal stress has a clear relationship with the roadway axis and the stress inclination angle is small, the stress field can be approximated as being dominated by horizontal forces. In this case, to balance construction convenience and economy, parallel boreholes are constructed perpendicular to the roadway coal wall and along the horizontal direction. This process is simple, efficient, and can achieve effective stress release while controlling costs. Specifically, such as Figure 2 As shown, in the horizontal plane, the design depth L of the parallel borehole group must satisfy L=l / sinθ, where l is the vertical horizontal distance between the pressure relief area and the roadway coal wall, and the vertical horizontal distance is the distance from the coal wall surface to the horizontal projection of the target pressure relief area in the direction perpendicular to the coal wall within the design cross section of the roadway; θ is the angle between the direction of the maximum principal stress and the roadway coal wall.

[0028] In addition, the end of the parallel borehole group must exceed the peak position of the coal seam support pressure in the roadway. Generally, if the coal seam thickness is less than 3.5m, the borehole depth shall not be less than 15m; if the coal seam thickness is greater than or equal to 3.5m and less than or equal to 8m, the borehole depth shall not be less than 20m; if the coal seam thickness is greater than 8m, the borehole depth shall not be less than 25m; the borehole depth at the face of the tunnel shall not be less than 20m.

[0029] In this embodiment, the parallel borehole group consists of large-diameter boreholes, with a diameter of not less than 100 mm. Using large-diameter boreholes is more conducive to creating fissures and causing plastic deformation in the coal seam surrounding the boreholes, thereby achieving the purpose of pressure relief.

[0030] In this embodiment, as Figure 6 As shown, when encountering hard coal and rock masses that make direct drilling difficult, the resulting issues include high drilling resistance, poor slag removal, abnormally high drill bit load, or low borehole formation efficiency. In such cases, a step-by-step drilling process of pilot hole followed by reaming is employed. Specifically, in large-diameter pressure relief borehole construction, if direct borehole formation is difficult, a smaller diameter drill bit can be used to drill to the target design depth to form a pilot hole. Then, a larger diameter drill bit is used to ream the borehole along the same trajectory, either forward or reverse drilling, ultimately forming a large-diameter borehole that meets the pressure relief requirements. Figure 6 The dotted line in the middle indicates the small-diameter pilot hole. By adopting a step-by-step drilling process, the mechanical disturbance to the coal and rock mass and the requirements for slag removal during a single drilling operation are reduced. This effectively avoids the risks of stuck drills and buried drills that occur during direct large-diameter drilling. While ensuring the quality of the hole and the designed depth, it achieves economical and safe construction of large-diameter pressure-relief boreholes under difficult conditions.

[0031] Preferably, in this embodiment, during the step-by-step drilling process, a large-diameter variable-diameter drill bit is used for hole enlargement. Variable-diameter drilling can protect the roadway surface support, offering a safety advantage.

[0032] The above mainly introduces the borehole layout strategy under a geostress field dominated by horizontal forces. However, if there is a significant angle between the geostress field and the horizontal plane, such as a large lateral pressure coefficient or a prominent vertical stress, or if the geostress conditions have not yet been accurately determined, a more flexible borehole layout strategy should be adopted. This could involve selecting boreholes within the vertical plane of the coal face in the roadway, such as... Figure 5 The diagram shows a fan-shaped borehole layout. The borehole angles can be dynamically adjusted based on on-site measured stress data, geological structure indicators, or drilling difficulty gradients identified through prior exploratory boreholes. This ensures that the borehole group can more effectively act on the actual principal stress transmission path, guaranteeing the effectiveness of the pressure relief range in three-dimensional space.

[0033] In summary, this embodiment provides a method for stress relief through drilling in the event of rock bursts. By optimizing the construction angle and flexibly integrating various techniques such as parallel borehole layout, fan-shaped borehole layout, and step-by-step borehole construction, it achieves complementary advantages and synergistic enhancement of different processes, ensuring a safe and efficient prevention and control effect. Specifically, if the direction of the maximum principal stress is known, or can be obtained through geostress detection, a group of parallel boreholes is constructed along the direction of the maximum principal stress. If geostress detection is not possible, or the detected stress field is disordered, a group of fan-shaped boreholes can be constructed. The group of fan-shaped boreholes can serve as stress relief boreholes or as probe boreholes to detect the direction of the maximum principal stress. Specifically, if the drilling depth of each borehole in the group of fan-shaped boreholes tends to be consistent, they can be directly used as stress relief boreholes. If the drilling depth of each borehole in the group of fan-shaped boreholes differs significantly, the direction of the borehole with the longest drilling depth can be approximated as the direction of the maximum principal stress, and a group of parallel boreholes can be constructed along it to improve the stress relief and prevention and control effect.

[0034] Among them, when the direction of the maximum principal stress is known, orifices can be oriented along this direction to accurately act on the high stress transmission path, achieving more thorough stress release and energy transfer with less engineering work, thereby significantly improving pressure relief efficiency and reducing prevention and control costs.

[0035] By observing the significant differences in drilling depth during the construction of fan-shaped boreholes, the dominant direction of the maximum principal stress in the region can be directly and quickly deduced. This provides a low-cost and high-efficiency on-site criterion for subsequent optimization of borehole layout schemes, and enables the simultaneous implementation of construction process and geological diagnosis.

[0036] When encountering hard coal and rock masses that make direct drilling difficult, a step-by-step process of pilot hole followed by borehole enlargement is flexibly switched to, which significantly improves the reliability and borehole formation rate of successfully forming an effective large-diameter pressure relief space under complex geological conditions, and ensures the smooth implementation of the prevention and control project.

[0037] Of course, the aforementioned hole layout and drilling techniques are not isolated from each other, but should be systematically combined and dynamically adjusted based on the specific geomechanical conditions, measured stress data, and construction dynamic feedback on site. Multiple techniques such as parallel hole layout, fan-shaped hole layout, and step-by-step hole drilling can be flexibly integrated to achieve complementary advantages and synergistic enhancement of different processes. In the engineering practice of rockburst prevention and control, engineers can weigh different objectives such as prioritizing economy, ease of construction, or maximizing pressure relief effect, flexibly utilizing and combining modules such as parallel hole layout and fan-shaped hole layout, thereby pursuing the overall optimization of regional prevention and control effects while controlling costs and construction period.

[0038] In summary, the angle adjustment of the borehole in the horizontal plane and the angle adjustment in the cross-section can be used in combination, and even the design of borehole diameter changes can be flexibly selected according to the needs of the site to achieve pressure relief drilling construction under complex geological conditions. That is, this comprehensive application solution can form a customized and adaptive pressure relief solution for the variable coal seam occurrence and stress environment, thereby optimizing the pressure relief efficiency and improving the overall reliability and economy of the prevention and control project while ensuring safety.

[0039] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0040] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for relieving pressure during rockburst drilling, characterized in that, Obtain the direction of the maximum principal stress in the area to be relieved, and construct a group of parallel boreholes along the direction of the maximum principal stress in the coal wall of the roadway, so that the group of parallel boreholes covers the stress concentration area of ​​the area to be relieved.

2. The method for relieving pressure during rockburst drilling according to claim 1, characterized in that, When obtaining the direction of the maximum principal stress in the area to be relieved, if in-situ stress detection cannot be performed, or if the detected in-situ stress field is disordered, a group of fan-shaped boreholes is constructed in the horizontal plane perpendicular to the coal wall of the roadway and in the vertical plane where the coal wall of the roadway is located. The direction of the maximum principal stress in the area to be relieved is inferred from the drilling depth of each borehole in the group of fan-shaped boreholes.

3. The method for relieving pressure during rockburst drilling according to claim 2, characterized in that, If the difference in the depth of each borehole in the fan-shaped borehole group exceeds the preset depth difference, then the direction of the borehole with the longest depth will be regarded as the direction of the maximum principal stress in the area to be relieved.

4. The method for relieving pressure during rockburst drilling according to claim 2, characterized in that, If the difference in the drilling depth of each borehole in the fan-shaped borehole group does not exceed the preset depth difference, then the direction perpendicular to the coal wall of the roadway is regarded as the direction of the maximum principal stress in the area to be relieved.

5. The method for relieving pressure during rockburst drilling according to claim 1, characterized in that, If the direction of the maximum horizontal principal stress in the pressure relief area is clearly related to the roadway axis, and the inclination angle of the stress field is less than the preset inclination angle, then the direction of the maximum horizontal principal stress is approximated as the direction of the maximum principal stress.

6. The method for relieving pressure during rockburst drilling according to claim 5, characterized in that, In the horizontal plane, the design depth L of the parallel borehole group must satisfy L=l / sinθ, where l is the vertical horizontal distance between the pressure relief area and the roadway coal wall, and the vertical horizontal distance is the distance from the coal wall surface to the horizontal projection of the target pressure relief area in the direction perpendicular to the coal wall within the design cross section of the roadway; θ is the angle between the direction of the maximum principal stress and the roadway coal wall.

7. The method for relieving pressure during rockburst drilling according to claim 6, characterized in that, The end of the parallel borehole group must exceed the peak position of the coal seam support pressure in the roadway. If the coal seam mining thickness is less than 3.5m, the drilling depth shall not be less than 15m; if the coal seam mining thickness is greater than or equal to 3.5m and less than or equal to 8m, the drilling depth shall not be less than 20m. If the coal seam thickness is greater than 8m, the drilling depth shall not be less than 25m; the drilling depth at the face of the tunnel shall not be less than 20m.

8. The method for relieving pressure during rockburst drilling according to claim 1, characterized in that, The parallel borehole group consists of large-diameter boreholes with a diameter of not less than 100 mm.

9. The method for relieving pressure during rockburst drilling according to claim 8, characterized in that, When encountering hard coal and rock masses that make direct drilling difficult, a step-by-step process of pilot hole drilling followed by hole enlargement is adopted to construct the borehole.

10. The method for relieving pressure during rockburst drilling according to claim 9, characterized in that, During the drilling process using a step-by-step method, a large-diameter variable-diameter drill bit is used for hole enlargement.

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