A method for shaped charge stress relief blasting based on diffuse reflection of stress waves

Abstract

This invention provides a stress relief blasting method based on the control of diffuse reflection of stress waves. This method involves placing a diffuse reflection sphere at the bottom of the borehole. The sphere's surface contains raised structures, which form a diffuse reflection surface for stress waves. Compared to existing shaped charge stress relief blasting technologies, in this invention, when the explosive detonates inside the borehole, the raised structures on the diffuse reflection sphere at the bottom of the borehole allow the explosive impact to be reflected more evenly to the nearby rock mass in the stress relief section of the borehole. This results in uniform fracturing of the surrounding rock, forming a uniformly fractured zone perpendicular to the borehole axis rather than a primary crack in a specific direction. This significantly reduces the bearing capacity of the surrounding rock near the borehole in the stress relief section, shifting the stress concentration zone away from the tunnel face, reducing the risk of rockburst during deep tunnel excavation, and better ensuring construction safety.

Description

Technical Field

[0001] This invention relates to the field of blasting technology, and in particular to a method for shaped charge stress relief blasting based on diffuse reflection of stress waves. Background Technology

[0002] my country's infrastructure projects, such as water conservancy and transportation, are large-scale, requiring extensive excavation. Among current excavation technologies, blasting excavation is one of the main methods. However, deep-buried tunnel blasting excavation projects, applicable to mining, transportation, and water conservancy, often face the problem of excessively high ground stress. Under high ground stress conditions, the strain energy or potential energy accumulated in the rock mass during blasting excavation may be suddenly released, causing rock mass failure and rock bursts. Rock bursts can lead to damage to construction equipment and personnel casualties, severely impacting construction progress.

[0003] Currently, based on traditional blasting methods, some scholars have proposed stress-relieving blasting methods that actively damage and rationally release the stress in the surrounding rock of tunnels, based on the transient stress unloading effect. This involves using borehole blasting technology perpendicular to the tunnel face to perform asymmetric pre-blasting of the stress concentration zone in the surrounding rock near the face, thereby inducing the premature transient release of strain energy in the surrounding rock to improve the stress distribution and shift the stress concentration zone away from the tunnel face, thus preventing rockburst. Meanwhile, some scholars (CN202210694271.6) have introduced shaped charge blasting technology into stress-relieving blasting to enhance its effectiveness and reduce explosive usage. However, existing shaped charge stress-relieving blasting methods, through directional shaped charge blasting, cause the reflected explosive stress wave to concentrate in a fixed direction behind the tunnel face, resulting in only a few cracks and an insufficient fracture zone. This portion of the rock mass still has high bearing capacity, and the effect of improving stress concentration is not significant. Furthermore, the installation requires consideration of the shaped charge structure direction, making installation inconvenient and affecting construction efficiency. Summary of the Invention

[0004] To address the aforementioned issues, a method for shaped charge stress relief blasting based on diffuse reflection of stress waves is proposed. This method aims to use a diffuse reflection sphere to reflect most of the explosive stress waves propagating towards the bottom of the borehole into the surrounding rock mass more evenly, thereby increasing the extent of the surrounding rock damage zone and reducing the stress level of the surrounding rock to prevent rockburst.

[0005] The principle behind this invention's diffuse reflection sphere structure enhancing the cracking effect around rock masses is as follows:

[0006] After detonation, the stress waves generated by the explosion are first transmitted and reflected at the interface between the spherical structure and the air. Because the spherical structure is made of a high wave impedance material, most of the explosive stress waves propagating towards the bottom of the borehole can be reflected into the surrounding rock mass through diffuse reflection. At the same time, due to the protruding structure on the diffuse reflection sphere, each protruding structural unit has a transmission and reflection effect on the explosive stress waves at different angles. The explosive stress waves that should have been transmitted and reflected in a fixed direction at the contact point with the diffuse reflection structure will be affected by the local protruding structure. The stress waves near this point will propagate in different directions, and the stress wave effect will be further dispersed, resulting in a uniform fracturing effect on a larger area of ​​rock mass. This forms a uniform fracturing zone perpendicular to the borehole axis rather than cracks, reducing the bearing capacity of the surrounding rock near the borehole in the stress relief section and pushing the stress concentration area away from the working face, thereby improving the stress distribution of the surrounding rock and reducing the risk of rockburst during the excavation of deep-buried tunnels.

[0007] The beneficial effects of the above scheme are:

[0008] 1) Compared with the existing energy-focused stress relief blasting technology, which can only focus energy in a small area at certain angles and cannot uniformly form cracks around the borehole, effectively reduce the bearing capacity of the rock mass, and thus improve the stress distribution of the rock mass, this invention adds a spherical structure with a special surface shape to the bottom of the borehole. This can improve the distribution angle of the reflected stress wave and make most of the stress wave that should have been transmitted to the borehole be reflected and uniformly propagated to the rock mass around the borehole. This forms a uniform fracture zone perpendicular to the borehole axis, which reduces the bearing capacity of the surrounding rock near the borehole in the stress relief section and pushes the stress concentration area away from the tunnel face. This improves the stress distribution of the surrounding rock and reduces the risk of rockburst during the excavation of deep-buried tunnels.

[0009] 2) The diffuse reflection sphere in this invention is easy to install. Compared with other types of energy-concentrating structures, there is no need to consider the installation direction, which can improve construction efficiency and speed up construction. Attached Figure Description

[0010] Figure 1 This is a cross-sectional view of the stress relief blasting borehole arrangement in this invention;

[0011] Figure 2 This is a longitudinal cross-sectional view of the stress relief blasting borehole arrangement in this invention;

[0012] Figure 3 This is a diagram illustrating the stress relief effect in this invention;

[0013] Figure 4 This is a schematic diagram illustrating the principle of a conventional shaped charge structure reflecting explosive stress waves.

[0014] Figure 5 This is a schematic diagram illustrating the principle of the diffuse reflection sphere reflecting the explosive stress wave in this invention.

[0015] The markings in the diagram are: 1. Diffuse sphere; 11. Sphere; 12. Protrusion; 2. Tunnel; 3. Blast hole; 4. Charge. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0019] like Figures 1 to 3 As shown, the method for shaped charge stress relief blasting based on diffuse reflection of stress waves provided in the embodiments of the present invention includes the following steps:

[0020] Step 1: Prefabricate a diffuse reflective spherical structure

[0021] According to the designed borehole diameter, a diffuse reflection sphere 1 is made of cast iron (including a spherical part 11 and a protrusion 12 on the surface of the spherical part 11, with the protrusion 12 evenly distributed on the spherical part 11). The diameter of the spherical part 11 of the diffuse reflection sphere 1 is slightly smaller than the borehole diameter.

[0022] Step 2: Drilling blast holes

[0023] First, the blast hole area is cleaned (manual cleaning combined with high-pressure air blowing). Then, each blast hole is laid out (corresponding points are clearly marked with red paint). Next, within the blasting zone, the blast holes are laid out strictly according to the blasting design, and the required drilling depth for each hole is calculated. Drilling operations only proceed after the hole layout accuracy is checked and approved (the blast hole layout is as follows). Figure 1 , Figure 2 As shown, the blast holes 3 are evenly arranged in 3 to 4 rows from top to bottom on the working face, with 4 to 5 blast holes 3 arranged in each row. The top row of blast holes 3 has a certain angle of elevation with the horizontal plane, and the other rows of blast holes 3 are arranged in the horizontal direction.

[0024] Step 3: Placement of the flexible padding layer and diffuse reflection spherical structure

[0025] First, pile up gravel or wood chips at the bottom of the borehole 3 to form a flexible pad, and then insert the diffuse reflection ball into the bottom of the borehole 3.

[0026] Step 4: Loading explosives, plugging the plug, and detonating.

[0027] Continue loading the explosive roll into borehole 3, concentrating the explosive section in the stress concentration section in front of the face of the tunnel. After the explosive is loaded, block borehole 3 with gravel until the opening of borehole 3. Finally, after confirming the safety of the entire detonation network, detonate the explosive in borehole 3 with a detonator to complete the blasting work.

[0028] Step 5: Check the effect of stress relief blasting

[0029] After the blasting work was completed, the risk of excavation induced by high-stress blasting excavation was controlled through microseismic monitoring and on-site rockburst recording.

[0030] Then, blasting and excavation of the working face will be carried out.

[0031] like Figure 4 As shown, compared to existing shaped charge stress relief blasting techniques that can only focus energy at certain angles within a small area and cannot uniformly form cracks around the borehole to effectively reduce the rock mass bearing capacity and thus improve the rock mass stress distribution, this invention adds a diffuse reflection sphere 1 at the bottom of the borehole. The protrusion 12 on the diffuse reflection sphere 1 improves the distribution angle of the reflected stress wave, thereby reflecting most of the stress wave that should have propagated through the borehole 3 to the surrounding rock mass. The stress wave effect is further dispersed, resulting in uniform fracturing of a larger area of ​​rock mass. This forms a uniform fracturing zone perpendicular to the axis of the borehole 3, reducing the bearing capacity of the surrounding rock near the borehole in the stress relief section and shifting the stress concentration area away from the tunnel face. This improves the stress distribution of the surrounding rock and reduces the risk of rockburst during deep tunnel excavation.

[0032] To expand the stress-relief zone formed after stress-relief blasting, the top first row of blast holes 3 in this invention can form an elevation angle of 8-12° with the horizontal plane (e.g., Figure 2 (As shown).

[0033] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for shaped charge stress relief blasting based on diffuse reflection of stress waves, characterized in that, Includes the following steps: Step 1: Prefabricate diffuse reflection spheres according to the designed diameter of the borehole; Step 2: Clean up the blast hole area, then lay out the blast holes one by one, and then strictly follow the blasting design to lay out the blast holes in the blasting area. Calculate the required drilling depth for each blast hole, and only proceed with drilling operations after the accuracy of the hole layout is checked and approved. Step 3: Install a flexible pad at the bottom of the borehole to dissipate energy, and then install the diffuse reflection ball into the borehole so that the diffuse reflection ball sits on the flexible pad. Step 4: Load the explosives into the borehole, concentrating the charge in the stress concentration section in front of the face of the tunnel. After the charge is completed, block the borehole with gravel until the opening is reached. Finally, after confirming the safety of the entire detonation network, detonate the explosives in the borehole with a detonator to complete the blasting operation. Step 5: Conduct blasting and excavation at the working face; The diffuse reflection sphere includes a spherical part and protrusions on the surface of the spherical part, the protrusions being evenly distributed on the spherical part.

2. The method for shaped charge stress relief blasting based on diffuse reflection of stress waves according to claim 1, characterized in that, The blast holes are evenly arranged in 3 to 4 rows from top to bottom on the working face, with 4 to 5 blast holes in each row.

3. The method for shaped charge stress relief blasting based on diffuse reflection of stress waves according to claim 2, characterized in that, The first blast hole at the top has a certain angle of elevation to the horizontal plane, while the blast holes in the other rows are arranged in a horizontal direction.

4. The method for shaped charge stress relief blasting based on diffuse reflection of stress waves according to claim 2 or 3, characterized in that, The depth of the borehole exceeds the stress concentration zone at the working face.

5. The method for shaped charge stress relief blasting based on diffuse reflection of stress waves according to claim 1, characterized in that, The spherical part and the protrusion part are integrally formed.

6. The method for shaped charge stress relief blasting based on diffuse reflection of stress waves according to claim 1 or 5, characterized in that, The diffuse reflection sphere is made of a high wave impedance material.

7. The method for shaped charge stress relief blasting based on diffuse reflection of stress waves according to claim 1, characterized in that, The flexible padding layer is formed by laying crushed stone or wood chips.

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