Method for modifying shape of bottom end of blast hole through direct drilling so as to accurately control explosion energy

Abstract

The invention relates to a method for transforming the shape of the bottom end of a blast hole through direct drilling so as to accurately control explosion energy, and provides a method for transforming the shape of the bottom end of the blast hole through direct drilling so as to accurately control explosion energy in view of the progress of the current rock drilling bit technology. The problem of step blasting root bottom in rock blasting is solved, breaking of rock at the bottom end of a cut blast hole in the tunnel blasting and tunneling process is improved, the phenomenon of hitching feet at the bottom of the hole in presplitting blasting and excessive damage to reserved rock mass are avoided, and the quality of a foundation surface in blasting excavation of the rock mass foundation surface is improved. Particularly, the in-situ exploitation range of shale oil (gas) wells and tight sandstone metal ores and the fracturing range of geothermal energy are enlarged, and the damage of blasting to a water-resisting layer is weakened. Besides, in nuclear power engineering construction, pre-splitting and smooth blasting transfer energy to one side in nuclear island negative excavation, damage to reserved rock mass is avoided while a contour surface is formed, a transformation scheme can be selected according to actual situation requirements and the size of a drill bit, and the application range is wide.

Description

Technical Field

[0001] The present invention relates to the fields of energy carbon reduction and clean energy extraction, and in particular, it designs a method for precisely controlling the explosion energy by directly drilling to transform the shape of the bottom end of the blast hole. Background Art

[0002] As the most commonly used technical means for rock excavation, drilling and blasting has been widely applied in engineering such as mine exploitation and water conservancy construction. In bench blasting, due to insufficient explosion energy at the end of the blast hole and a large resistance line at the bench, the rock-breaking effect is poor. Therefore, in solving the problem of stumps, the method of drilling deeper holes is adopted in the blasting design specifications. During the tunneling blasting process, the rock-breaking effect at the bottom end of the cut holes affects the tunneling footage. Therefore, the method of drilling deeper holes is also adopted for the cut holes in the tunnel blasting design. The connection quality at the bottom end of the perimeter holes in tunnel or slope projects directly affects the excavation quality. In the pre-splitting blasting design, considering the large clamping effect at the bottom end of the blast hole, enhanced charging is usually carried out. However, excessive explosive charges will inevitably expand the damage range of the remaining rock mass at the bottom, and too little explosive charge will cause the phenomenon of hanging feet. In the blasting excavation of the rock foundation surface, considering that the damage of the blast hole end to the remaining rock mass will affect the quality of the foundation, the horizontal pre-splitting blasting method is recommended by the specifications. Limited by the drilling difficulty and quality of the horizontal blast holes, the construction efficiency is low. During the efficient exploitation of fossil energy and the development of deep clean energy, the technical problem of enhancing the permeability of thin reservoirs is often encountered.

[0003] Zhao Gen et al. designed and fabricated two types of shaped charges, namely circumferential cutting type and circumferential perforating type, for vertical drilling and blasting attempts. Possibly limited by the explosive energy and construction technology, the method of using shaped charges at the end of the blast hole has not been popularized. Luo Yong designed a multi-point shaped charge cutting blasting by connecting single circumferential cuts in series. Deng Yongxing et al. proposed a spiral tube shaped charge, which concentrated the explosive energy in the direction of the vertical hole wall to penetrate the radial initial guiding cracks. However, the explosive in the shaped charge needs to use an explosive with a high energy density, and the operation of filling deeper blast holes is more cumbersome. Therefore, the popularization and application of the annular shaped charge are restricted. Subsequently, Lu Wenbo et al. proposed the vertical hole composite energy dissipation blasting technology, which improved the lateral work ability of the explosive in the blast hole by using the reflection of the shock wave on the high-wave impedance pad, and at the same time, the buffering effect of the loose sand cushion reduced the impact of blasting on the rock mass of the foundation surface. However, this method also has the problem of too many construction procedures. Summary of the Invention

[0004] In view of the above problems, the present invention adopts the following technical solutions:

[0005] A method for directly drilling to transform the shape of the bottom end of a blast hole to precisely control the explosion energy, which includes opening a circular cylindrical cutting slot downward at the bottom edge of the blast hole, or opening a circular cylindrical cutting slot downward at both the bottom edge and the middle of the blast hole, or opening a circular cylindrical cutting slot downward at the bottom edge of the blast hole and opening a hemispherical groove sunken downward in the middle of the bottom of the blast hole, or directly opening a spherical groove sunken downward in the middle of the bottom of the blast hole, or cutting a conical or hemispherical rock platform at the bottom of the blast hole, or cutting a wedge-shaped rock platform at the bottom of the blast hole.

[0006] Furthermore, a circular cylindrical cutting slot is opened downward on the outer sides of the above-mentioned cone, hemispherical rock platform, and wedge-shaped rock platform.

[0007] After the present invention adopts the above technical solutions, compared with the prior art, it has the following advantages:

[0008] In view of the progress of the current rock drilling bit technology, the present invention proposes a method for directly drilling to transform the shape of the bottom end of a blast hole to precisely control the explosion energy, so as to solve the problem of bench blasting foundation in rock blasting, improve the rock fragmentation at the bottom end of the cut blast hole during the tunneling blasting process, avoid the phenomenon of foot hanging at the hole bottom in pre-splitting blasting and excessive damage to the reserved rock mass, and improve the quality of the construction base surface in the blasting excavation of the rock mass construction base surface. Especially, it can increase the fracturing range of shale oil (gas) wells, in-situ mining of tight sandstone metal mines, and geothermal energy, and weaken the damage to the aquiclude caused by blasting. In addition, during the construction of nuclear power projects, in the negative excavation of the nuclear island, pre-splitting and smooth blasting transfer the energy to one side, which not only forms the contour surface but also avoids damage to the reserved rock mass, and the transformation plan can be selected according to the actual situation and the size of the drill bit, with a wide range of adaptability. And the transformation plan can be selected according to the actual situation and the size of the drill bit, with a wide range of adaptability. The present invention can, without affecting the lower floor and the upper roof, improve the fragmentation range and fragmentation uniformity of the middle high-content rock energy reservoir, so as to improve the flow, replacement, and exploitation efficiency of low-permeability energy in the pores.

[0009] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0010] Figure 1 It is a schematic structural diagram when opening a circular cylindrical cutting slot downward at the bottom edge of the blast hole;

[0011] Figure 2 It is a schematic diagram of opening a circular cylindrical cutting slot downward at both the bottom edge and the middle of the blast hole;

[0012] Figure 3 It is directly opening a spherical groove sunken downward in the middle of the bottom of the blast hole;

[0013] Figure 4A cylindrical cutting slot is opened in a circle downward at the bottom edge of the blast hole, and a downwardly concave hemispherical groove is opened in the middle of the bottom of the blast hole;

[0014] Figure 5 Schematic diagram of cutting a conical rock bench at the bottom of the blast hole;

[0015] Figure 6 Schematic diagram of cutting a hemispherical rock bench at the bottom of the blast hole;

[0016] Figure 7 Schematic diagram of cutting a wedge-shaped rock bench at the bottom of the blast hole;

[0017] Figure 8 Schematic diagram of the finite element calculation model after cutting at the bottom;

[0018] Figure 9 Schematic diagram of the finite element calculation model before cutting at the bottom;

[0019] Figure 10 Damage nephogram under the condition of no cutting at the bottom;

[0020] Figure 11 Damage nephogram under the condition of cutting at the bottom;

[0021] Figure 12 Damage time history curve of the observation element under the condition of no cutting at the bottom;

[0022] Figure 13 Damage time history curve of the observation element under the condition of no cutting at the bottom. Specific implementation mode

[0023] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0024] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0025] To avoid damage to the rock at the bottom of the hole caused by the explosion of explosives, after drilling to a certain depth, a frustum shape is cut at the bottom of the hole, as shown in Figure 1 . By means of the impact damage effect of the frustum carrying the explosive, the explosion damage to the rock at the bottom of the hole is avoided.

[0026] The mechanical model of the frustum under load is similar to uniaxial compression without lateral pressure. The impact pressure on the surface of the rock bench:

[0027]

[0028] Where: P J is the detonation pressure of the explosive explosion, ρ 岩 is the density of the rock, C 岩 is the longitudinal wave velocity of the rock, ρ 炸药 is the density of the explosive, D 炸药 is the detonation velocity of the rock explosive.

[0029] Approximate the columnar charge in contact with the rock bench at the bottom of the hole as a spherical charge with a diameter of D. The calculation formula for the height of the rock bench is:

[0030]

[0031] Where: σ cd is the dynamic compressive strength of the rock; α is the attenuation coefficient of the explosion pressure in the rock; D is the diameter of the charge. When the diameter of the charge is greater than or equal to the diameter of the rock bench, the impact pressure does not need to be converted. When the diameter of the charge is less than or equal to the diameter of the rock bench, the impact pressure can be converted according to the area ratio. The range of the rock bench height is H≥0. When H = 0, this situation is the common flat bottom end.

[0032] When the height of the rock bench is too large, drilling holes on the rock bench can be adopted, as shown in Figures 2 - 4 , which can better dissipate the impact pressure and thus reduce the height of the rock bench.

[0033] When it is required to protect the rock at the bottom of the hole but break the lateral rock, a conical or semi-cylindrical shape can be cut out on the round platform to transfer the explosion energy to both sides, as shown in Figures 5 - 6 .

[0034] In presplitting or smooth blasting, when it is required to protect the rock at the bottom of the hole but break the rock on one side, a wedge shape can be cut out on the round platform to transfer the explosion energy to one side. When more energy is required at the bottom of the blast hole, the hole can be enlarged, as shown in Figure 7 .

[0035] A finite element numerical calculation is established for the case of opening a circular cylindrical cutting slot downward at the bottom edge of the blast hole. The width×height of the rock matrix is 8×10m, the depth of the blast hole is 6m, and the diameter is 100mm. Among them, the length of the charging section is 4m, the diameter of the explosive is 70mm, the length of the stemming section is 2m, the Euler algorithm is used for the explosive and air, and the Lagrangian algorithm is used for the rock. The observation point is 1.2m away from the bottom of the blast hole. Partial screenshots of the finite element numerical models of the uncut blast hole bottom and the cut blast hole bottom are shown in Figures 8 - 9 ;

[0036] The comparison results of the damage cloud diagrams before and after cutting the bottom are shown in Figures 10 - 11As shown in the figure, analysis reveals that: under the condition of bottom cutting, the damage range is much smaller than that without bottom cutting.

[0037] As Figures 12 - 13 , the damage value of the observation unit under the condition of no bottom cutting of the blast hole is 0.85, while the damage value of the observation unit under the condition of bottom cutting of the blast hole is 0. It can be seen that adopting the solution of the present invention can significantly reduce the damage range at the bottom of the blast hole.

[0038] The above is an example of the best implementation mode of the present invention, and the parts not detailed herein are all common general knowledge of those of ordinary skill in the art. The protection scope of the present invention shall be subject to the content of the claims, and any equivalent transformation based on the technical inspiration of the present invention shall also be within the protection scope of the present invention.

Claims

1. A method for directly drilling to transform the shape of the bottom end of a blast hole to precisely control the explosion energy, characterized in that, A cylindrical cutting slot is opened downward at the bottom edge of the blast hole, or a cylindrical cutting slot is opened downward at both the bottom edge and the middle part of the blast hole, or a cylindrical cutting slot is opened downward at the bottom edge of the blast hole and a hemispherical groove sunken downward is opened in the middle of the bottom of the blast hole, or a spherical groove sunken downward is directly opened in the middle of the bottom of the blast hole, or a conical or hemispherical rock platform is cut at the bottom of the blast hole, or a wedge-shaped rock platform is cut at the bottom of the blast hole.

2. The method for directly drilling to transform the shape of the bottom end of a blast hole to precisely control the explosion energy according to claim 1, wherein A cylindrical cutting slot is opened downward on the outer sides of the conical, hemispherical rock platform and wedge-shaped rock platform.

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