Quantitative evaluation method for blasting pressure relief effect

Abstract

The invention belongs to the field of roadway support, and particularly relates to a quantitative evaluation method for a blasting pressure relief effect, which comprises the following steps of: drilling a first drill hole in a roadway side at a comparison section by adopting a geological drilling machine, and drilling a second drill hole at a blasting test section after blasting pressure relief, respectively recording the relationship between the propulsive force and the drilling depth in the drilling process, the relationship between the propulsive force and the drilling depth before blasting pressure relief, and the vertical stress at different depth positions of a drill hole; and then according to the blasting surrounding rock failure range increase rate, the blasting surrounding rock stress peak value reduction rate and the blasting surrounding rock stress peak value position transfer rate, a blasting pressure relief effect comprehensive evaluation index K is obtained, the blasting pressure relief effect comprehensive evaluation index K is compared with a standard value K0, and pressure relief measures are adjusted according to the result. According to the method, surrounding rock failure range partition and stress transfer quantitative analysis can be obtained by punching once before and after blasting and analyzing data, the construction method and calculation steps are simple and easy to implement, supporting guidance can be scientifically quantified through calculation results, and evaluation results are reliable.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel support, and in particular relates to a quantitative evaluation method for blasting pressure relief effect. Background Art

[0002] In recent years, with the continuous increase in mining depth and intensity, a large number of difficult-to-support tunnels with high stress, strong mining impact, soft and broken surrounding rock have appeared one after another. Large deformation, support failure, roof collapse, bottom heave and other phenomena are frequent, which not only greatly increases the intensity, frequency and support costs of tunnel repairs, but also poses serious safety hazards.

[0003] Under high stress conditions in deep wells, blasting to relieve pressure is an important way to solve the problem of tunnel stability control. Figure 1 As shown in the figure, by blasting and unloading the surrounding rock stress concentration area, the shallow surrounding rock stress can be transferred to the deep part, reducing the shallow stress concentration of the floor and the side of the tunnel. However, there is currently a lack of targeted methods for the blasting and unloading effect, such as determining the scope of surrounding rock damage, the degree of stress transfer, and how to quantitatively guide subsequent support.

[0004] Among them, borehole television, geological radar and sonic wave method are commonly used to test the damage range of surrounding rock. Borehole television and geological radar are mainly qualitative, with a low degree of quantification; the sonic wave method requires water to be injected into the test hole or filled with water belts, which will cause cracks in the broken surrounding rock and the test success rate is low. In addition, there is a lack of coordinated analysis of the damage range of surrounding rock and stress distribution.

[0005] In view of the above problems, a quantitative evaluation method for joint analysis of surrounding rock failure range and stress transfer is urgently needed. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for quantitatively evaluating the blasting pressure relief effect.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A quantitative evaluation method for blasting pressure relief effect comprises the following steps:

[0009] S1. Select two sections with similar geological conditions in the tunnel, and mark them as the comparison section and the blasting test section; use a geological drill to drill the first borehole on the tunnel wall in the comparison section, and record the relationship between the propulsion force and the drilling depth during the drilling process, that is, the relationship between the propulsion force and the drilling depth before blasting pressure relief;

[0010] S2, after the first drilling is completed, clean it, bury the stress test rod in the first drilling hole, and after the data is stable, record the vertical stress magnitude at different depths of the first drilling hole;

[0011] S3, blasting and depressurizing the tunnel blasting test section, and after completion, use a geological drill to drill a second borehole on the side of the tunnel in the middle of the test section, and record the relationship between the propulsion force and the drilling depth during the drilling of the second borehole;

[0012] S4. After the second drilling is completed, it is cleaned and a stress test rod is buried in the second drilling hole. After the data is stable, the vertical stress at different depths of the second drilling hole is recorded, which is the relationship between the propulsion force and the drilling depth after blasting pressure relief;

[0013] S5. Evaluation of blasting pressure relief effect:

[0014] S51. Compare the relationship between the thrust and the drilling depth before and after blasting and pressure relief, and quantitatively determine the changes in the zoning of the surrounding rock damage range;

[0015] S52, comparing the vertical stress magnitudes at different depths of the first borehole before blasting pressure relief and the second borehole after blasting pressure relief, and quantitatively determining the stress reduction degree and peak position shift;

[0016] S53. Determine the comprehensive evaluation index K of blasting pressure relief effect based on the results of S51 and S52.

[0017] K = α1η1+α2η2+α3η3;

[0018] In the formula, η1 is the increase rate of the destruction range of the surrounding rock caused by blasting; η2 is the reduction rate of the peak stress of the surrounding rock caused by blasting; η3 is the transfer rate of the peak position of the surrounding rock stress caused by blasting; α1, α2, α3 are the weight coefficients of each index;

[0019] S54. Compare the comprehensive evaluation index K of blasting pressure relief effect with the standard value K0. When K>K0, the blasting pressure relief effect is qualified; when K<K0, the blasting pressure relief effect is unqualified and it is necessary to increase the drilling depth for additional pressure relief.

[0020] Further, in step S5, according to the relationship between the propulsion force and the drilling depth, the destruction range of the surrounding rock of the comparison section is quantitatively determined to obtain the destruction range D1; the stress test rod records the vertical stress magnitude at different depths of the first borehole, and the stress peak is measured as σ1, and the stress peak position is L1;

[0021] After the blasting test section is blasted, the damage range of the surrounding rock in the blasting section is quantitatively determined according to the relationship between the propulsion force and the drilling depth, and the damage range D2 is obtained; the stress test rod records the vertical stress at different depths of the second borehole, and the stress peak is measured as σ2, and the stress peak position is L2; ​​then,

[0022] The increase rate of blasting surrounding rock damage range η1 = |D2-D1| / D1;

[0023] The peak reduction rate of blasting surrounding rock stress η2 = |σ1-σ2| / σ1;

[0024] The peak position transfer rate of blasting surrounding rock stress η3 = |L1-L2| / L1.

[0025] Furthermore, in step S5, the weights vary according to different lanes and are determined according to the ratio between the indicators corresponding to each weight. The formula for determining the weight coefficient is α i＝ η i / ∑η i , and ∑α i =1; where i=1, 2, 3.

[0026] Furthermore, in step S5, the standard value K0 is an empirical value obtained by comprehensively analyzing the statistics of blasting pressure relief effects in different tunnels of the mine in the early stage.

[0027] Furthermore, in step S1, the comparison section and the blasting test section belong to a tunnel, the two have the same length, the same support design, the tunnel elevation difference does not exceed 1m, and the strata are in the same lithological layer; the comparison section and the blasting test section are separated by 30 to 40m.

[0028] Furthermore, the first borehole and the second borehole have the same depth, both of which are 10 to 20 meters.

[0029] Furthermore, when drilling the first borehole and the second borehole, the geological drilling rig selects a mode of constant drilling rate and rotation speed, and monitors the torque and propulsion force during the drilling process.

[0030] Furthermore, a stress measuring point is arranged every 0.8 to 1 m on the stress testing rod.

[0031] Furthermore, the stress test rod includes a main rod, a plurality of stress test components installed at intervals on the main rod, a hole sealing sleeve installed at the end of the main rod, and a data display, and the stress test component is electrically connected to the data display through a data transmission wire.

[0032] The beneficial effects of the present invention are:

[0033] The present invention determines the zoning of surrounding rock damage range by using the relationship between the propulsion force and the drilling depth recorded by the drilling rig, thereby avoiding adverse factors such as hole collapse, and a stress test rod can be installed after drilling for stress monitoring, so that one hole can be used for two purposes, and data can be obtained for the same position in the tunnel; the same borehole is used for drilling and stress testing, which ensures that the data will not deviate between different holes, that is, the damage range and stress distribution of a certain borehole obtained by testing are unique.

[0034] The invention can obtain surrounding rock damage range zoning and stress transfer quantitative analysis by drilling once before and after blasting and analyzing the data. The construction method and calculation steps are simple and easy to implement. The calculation results can provide scientific and quantitative support guidance, and the evaluation results are reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them:

[0036] Figure 1 Schematic diagram of stress transfer during blasting pressure relief.

[0037] Figure 2 It is a schematic diagram of the positions of the blasting test section and the comparison section of an embodiment of the present invention.

[0038] Figure 3 Schematic diagram of the structure of a stress testing rod according to an embodiment of the present invention.

[0039] Figure 4 It is the stress variation curve before and after the explosion pressure relief of the embodiment of the present invention.

[0040] Figure 5 This is a schematic diagram of the damage range obtained based on the propulsion force-drilling depth variation curve.

[0041] In the figure: 1-stress test component, 2-main rod, 3-data transmission wire, 4-hole sealing sleeve, 5-data display. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0043] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0044] A quantitative evaluation method for blasting pressure relief effect comprises the following steps:

[0045] S1. Select two sections with similar geological conditions in the tunnel, and mark them as the comparison section and the blasting test section; use a geological drill to drill the first borehole on the tunnel wall in the comparison section, and record the relationship between the propulsion force and the drilling depth during the drilling process, that is, the relationship between the propulsion force and the drilling depth before blasting pressure relief;

[0046] S2, after the first drilling is completed, clean it, bury the stress test rod in the first drilling hole, and after the data is stable, record the vertical stress magnitude at different depths of the first drilling hole;

[0047] S3, blasting and depressurizing the tunnel blasting test section, and after completion, use a geological drill to drill a second borehole on the side of the tunnel in the middle of the test section, and record the relationship between the propulsion force and the drilling depth during the drilling of the second borehole;

[0048] S4. After the second drilling is completed, it is cleaned and a stress test rod is buried in the second drilling hole. After the data is stable, the vertical stress at different depths of the second drilling hole is recorded, which is the relationship between the propulsion force and the drilling depth after blasting pressure relief;

[0049] S5. Evaluation of blasting pressure relief effect:

[0050] S51. Compare the relationship between the thrust and the drilling depth before and after blasting and pressure relief, and quantitatively determine the changes in the zoning of the surrounding rock damage range;

[0051] S52, comparing the vertical stress magnitudes at different depths of the first borehole before blasting pressure relief and the second borehole after blasting pressure relief, and quantitatively determining the stress reduction degree and peak position shift;

[0052] S53. Determine the comprehensive evaluation index K of blasting pressure relief effect based on the results of S51 and S52.

[0053] K = α1η1+α2η2+α3η3;

[0054] In the formula, η1 is the increase rate of the destruction range of the surrounding rock caused by blasting; η2 is the reduction rate of the peak stress of the surrounding rock caused by blasting; η3 is the transfer rate of the peak position of the surrounding rock stress caused by blasting; α1, α2, α3 are the weight coefficients of each index;

[0055] S54. Compare the comprehensive evaluation index K of blasting pressure relief effect with the standard value K0. When K>K0, the blasting pressure relief effect is qualified; when K<K0, the blasting pressure relief effect is unqualified and it is necessary to increase the drilling depth for additional pressure relief.

[0056] Further, in step S5, according to the relationship between the propulsion force and the drilling depth, the destruction range of the surrounding rock of the comparison section is quantitatively determined to obtain the destruction range D1; Figure 4 As shown in the figure, the stress test rod records the vertical stress magnitude at different depths of the first borehole, and the stress peak value is measured as σ1, and the stress peak position is L1; the damage range D1 is obtained from the propulsion force-drilling depth change curve, that is, the boundary between the low-speed stage and the high-speed stage of the propulsion force, which is the damage range, such as Figure 5 As shown;

[0057] After the blasting test section is blasted, the damage range of the surrounding rock in the blasting section is quantitatively determined according to the relationship between the propulsion force and the drilling depth, and the damage range D2 is obtained; the stress test rod records the vertical stress at different depths of the second borehole, and the stress peak is measured as σ2, and the stress peak position is L2; ​​then,

[0058] The increase rate of blasting surrounding rock damage range η1 = |D2-D1| / D1;

[0059] The peak reduction rate of blasting surrounding rock stress η2 = |σ1-σ2| / σ1;

[0060] The peak position transfer rate of blasting surrounding rock stress η3 = |L1-L2| / L1.

[0061] Under the condition of the same drilling depth, the relatively intact surrounding rock requires a larger propulsion force, while the relatively broken surrounding rock requires a smaller force; after the blasting, the surrounding rock damage range increases, and the propulsion force required for drilling the newly increased damage range is smaller. By comparing the propulsion force-drilling depth before and after the blasting, the change in the damage zone can be obtained; the present invention directly obtains the increase rate of the blasting surrounding rock damage range based on the propulsion force-drilling depth relationship curve.

[0062] Furthermore, in step S5, the weights vary according to different lanes. The specific calculation method is determined based on the ratio between the indicators corresponding to each weight. The formula for determining the weight coefficient is α i＝ η i / ∑η i , and ∑α i =1; where i=1,2,3.

[0063] Furthermore, the standard value K0 is an empirical value applicable to the tunnels of this mine, which is an empirical value obtained by comprehensively analyzing the blasting pressure relief effects of different tunnels in the previous mines. The empirical value K0 is obtained as follows:

[0064] 1) Determine the increase rate of the blasting surrounding rock damage range. It is generally believed that the increase rate of the blasting surrounding rock damage range is 20% to 50%, which can be considered to be a good blasting pressure relief effect. The specific value is determined according to the geological conditions of the tunnel, blasting parameters, tunnel burial depth and other conditions. For example, under the condition of less than 600m, the recommended value of the increase rate of the blasting surrounding rock damage range is 20%; under the condition of 600 to 1000m, the value increases by 5% for every 100 meters decrease in the tunnel burial depth, and the range of the increase rate of the blasting surrounding rock damage range is 20 to 40%; under the condition of more than 1000m, the recommended value of the increase rate of the blasting surrounding rock damage range is 50%.

[0065] 2) Determine the peak stress reduction rate of the blasting surrounding rock. It is generally believed that if the peak stress reduction rate reaches more than 30%, the pressure relief effect is better; when the peak stress reduction rate reaches more than 50%, the pressure relief effect is very significant. The specific value is determined according to the geological conditions of the tunnel location, the tunnel burial depth, the rock type and other conditions. For example, under coal rock conditions, the recommended value of the peak stress reduction rate of the blasting surrounding rock is 30%; under mudstone conditions, the recommended value of the peak stress reduction rate of the blasting surrounding rock is 40%; under sandstone conditions, the recommended value of the peak stress reduction rate of the blasting surrounding rock is 50%.

[0066] 3) Determine the peak position transfer rate of the blasting surrounding rock stress. It is generally believed that if the peak position transfer rate of the stress reaches more than 20%, the pressure relief effect is better. When the peak position transfer rate of the stress reaches more than 30%, the pressure relief effect is very significant. The specific value also needs to take into account the geological conditions, blasting parameters, support conditions, etc. For example, under the conditions of anchor nets, the recommended value of the peak position transfer rate of the blasting surrounding rock stress is 20%; under the conditions of anchor injection, the recommended value of the peak position transfer rate of the blasting surrounding rock stress is 25%; under the conditions of U-shaped steel, the recommended value of the peak position transfer rate of the blasting surrounding rock stress is 30%.

[0067] 4) Calculate the empirical value. Assuming that the increase rate of the blasting surrounding rock damage range is 40%, the decrease rate of the blasting surrounding rock stress peak value is 40%, and the transfer rate of the blasting surrounding rock stress peak position is 20%, then the standard value K0 = 0.4 × 40% + 0.4 × 40% + 0.2 × 2% = 0.36.

[0068] Further, such as Figure 2 As shown, in step S1, the comparison section and the blasting test section belong to a tunnel, and the geological conditions of the two are similar; specifically, the two have the same length, the same support design, the similar tunnel elevation (the difference does not exceed 1m), and the similar strata (the lithology of the strata is the same); the comparison section and the blasting test section are separated by 30 to 40m to eliminate the influence of the pressure relief blasting of the blasting test section on the comparison section, and at the same time avoid being too far away from the blasting point so that the surrounding rock stress is not affected.

[0069] Furthermore, the first borehole and the second borehole have the same depth, both of which are 10 to 20 meters.

[0070] Furthermore, when drilling the first borehole and the second borehole, the geological drilling rig selects a mode of constant drilling rate and rotation speed, and monitors the torque and propulsion force during the drilling process.

[0071] like Figure 3 As shown, Figure 3 As shown, the stress test rod is an integration of multiple stress test components 1, and the stress test component 1 can be a stress sheet or a pressure box; the length of the stress test rod is adapted to the depth of the borehole, so that the end of the stress test rod can extend to the bottom of the borehole; a stress measuring point is set on the stress test rod every 0.8 to 1 m, so that the stress distribution of the surrounding rock in the corresponding borehole can be tested. The structure of the stress test rod is similar to the force measuring anchor rod in the prior art; specifically, the stress test rod includes a main rod 2, a plurality of stress test components 1 installed at intervals on the main rod 2, a hole plugging sleeve 4 installed at the end of the main rod 2, and a data display 5, and the stress test component 1 is electrically connected to the data display 5 through a data transmission wire 3. The stress test rod can be purchased directly or purchased components to be made by itself.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are within the scope of protection of the pending claims of the present invention.

Claims

1. A quantitative evaluation method for blasting pressure relief effect, characterized in that: The following steps are involved: S1. Select two sections with similar geological conditions in the tunnel, and mark them as the comparison section and the blasting test section; use a geological drill to drill the first borehole on the tunnel wall in the comparison section, and record the relationship between the propulsion force and the drilling depth during the drilling process, that is, the relationship between the propulsion force and the drilling depth before blasting pressure relief; S2, after the first drilling is completed, clean it, bury the stress test rod in the first drilling hole, and after the data is stable, record the vertical stress magnitude at different depths of the first drilling hole; S3, blasting and depressurizing the tunnel blasting test section, and after completion, use a geological drill to drill a second borehole on the side of the tunnel in the middle of the test section, and record the relationship between the propulsion force and the drilling depth during the drilling of the second borehole; S4. After the second drilling is completed, it is cleaned and a stress test rod is buried in the second drilling hole. After the data is stable, the vertical stress at different depths of the second drilling hole is recorded, which is the relationship between the propulsion force and the drilling depth after blasting pressure relief; S5. Evaluation of blasting pressure relief effect: S51. Compare the relationship between the thrust and the drilling depth before and after blasting and pressure relief, and quantitatively determine the changes in the zoning of the surrounding rock damage range; S52, comparing the vertical stress magnitudes at different depths of the first borehole before blasting pressure relief and the second borehole after blasting pressure relief, and quantitatively determining the stress reduction degree and peak position shift; S53. Determine the comprehensive evaluation index K of blasting pressure relief effect based on the results of S51 and S52. K = α1η1+α2η2+α3η3; Where, η1 is the increase rate of the damage range of the surrounding rock caused by blasting; η2 is the reduction rate of the peak stress of the surrounding rock caused by blasting; η3 is the transfer rate of the peak position of the blasting surrounding rock stress; α1, α2, α3 are the weight coefficients of each index; S54. Compare the comprehensive evaluation index K of blasting pressure relief effect with the standard value K0. When K>K0, the blasting pressure relief effect is qualified; when K<K0, the blasting pressure relief effect is unqualified and it is necessary to increase the drilling depth for additional pressure relief.

2. The method for quantitatively evaluating blasting pressure relief effect according to claim 1, characterized in that: In step S5, according to the relationship between the propulsion force and the drilling depth, the destruction range of the surrounding rock of the comparison section is quantitatively determined to obtain the destruction range D1; the stress test rod records the vertical stress magnitude at different depths of the first borehole, and the stress peak is measured as σ1, and the stress peak position is L1; After the blasting test section is blasted, the damage range of the surrounding rock in the blasting section is quantitatively determined according to the relationship between the propulsion force and the drilling depth, and the damage range D2 is obtained; the stress test rod records the vertical stress at different depths of the second borehole, and the stress peak is measured as σ2, and the stress peak position is L2; ​​then, The increase rate of blasting surrounding rock damage range η1 = |D2-D1| / D1; The peak reduction rate of blasting surrounding rock stress η2 = |σ1-σ2| / σ1; The peak position transfer rate of blasting surrounding rock stress η3 = |L1-L2| / L1.

3. The method for quantitatively evaluating blasting pressure relief effect according to claim 1, characterized in that: In step S5, the weights vary according to different lanes and are determined according to the ratio between the indicators corresponding to each weight. The formula for determining the weight coefficient is α i＝ η i / ∑η i , and ∑α i =1; where i=1, 2, 3.

4. The method for quantitatively evaluating blasting pressure relief effect according to claim 1, characterized in that: In step S5, the standard value K0 is an empirical value obtained by comprehensively analyzing the statistics of blasting pressure relief effects in different tunnels of the mine in the early stage.

5. The method for quantitatively evaluating blasting pressure relief effect according to claim 1, characterized in that: In step S1, the comparison section and the blasting test section belong to a tunnel, the two have the same length, the same support design, the tunnel elevation difference does not exceed 1m, and the strata are in the same lithological layer; the comparison section and the blasting test section are separated by 30 to 40m.

6. The method for quantitatively evaluating blasting pressure relief effect according to claim 1, characterized in that: The first borehole and the second borehole have the same depth, both of which are 10 to 20 meters.

7. The method for quantitatively evaluating blasting pressure relief effect according to claim 1, characterized in that: When drilling the first and second holes, the geological drill rig selects a mode of constant drilling rate and rotation speed, and monitors the torque and propulsion force during the drilling process.

8. The method for quantitatively evaluating blasting pressure relief effect according to claim 7, characterized in that: A stress measuring point is arranged every 0.8 to 1 m on the stress testing rod.

9. The method for quantitatively evaluating blasting pressure relief effect according to claim 1, characterized in that: The stress test rod comprises a main rod (2), a plurality of stress test components (1) installed at intervals on the main rod (2), a hole plugging sleeve (4) installed at the end of the main rod (2), and a data display (5), wherein the stress test component (1) is electrically connected to the data display (5) via a data transmission wire (3).

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