A method for controlling over-break and under-break of tunnel blasting contour based on blasthole drilling parameters

Abstract

The present application relates to a tunnel blasting profile over-break and under-break control method based on blasthole drilling parameters, which includes: S1, drilling blastholes by a rock drill; S2, collecting drilling parameters during the drilling process, the drilling parameters including the rotation speed, drilling pressure, torque and drilling speed of the rock drill during the drilling process; S3, performing noise reduction processing on the drilling parameter data; S4, obtaining the rock uniaxial compressive strength value R according to the drilling parameter data after the noise reduction processing; S5, obtaining the number of structural surfaces per meter depth N according to the drilling parameter data after the noise reduction processing; S6, determining the explosive unit consumption q, blasthole spacing a and charge structure according to the uniaxial compressive strength value R and the number of structural surfaces per meter depth N. The blasting design is dynamically optimized according to the on-site working conditions, and the blasting parameters are scientifically and reasonably adjusted in real time to avoid over-break, which greatly improves the overall construction efficiency and ensures the safety and progress of the project.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel engineering, and in particular to a method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters. Background Art

[0002] In the field of tunnel engineering, over-excavation is the main engineering problem faced by drilling and blasting construction. During the excavation process, the over-excavation part must be filled with an equal amount of shotcrete. During the tunnel excavation process, the geological conditions of the surrounding rock, the development of joints, the distribution of cracks, weak interlayers and other factors have a significant impact on the blasting effect during the excavation process. These naturally formed structural surfaces make the actual blasting effect deviate from the designed surrounding blasthole contour line. The rock mass is more inclined to fracture and expand along these existing structural surfaces, resulting in a deviation between the actual shape of the excavation contour line and the expected shape, resulting in over-excavation. In addition, the geological conditions of the tunnel surrounding rock, the shape and size of the cross section, etc. are all changing with time and space. Real-time grasp of the tunnel surrounding rock information and dynamic adjustment of blasting parameters can help control the over-excavation of the tunnel.

[0003] The fundamental solution to the problem of tunnel over-excavation lies in the accurate selection of blasting hole network parameters. Traditional drilling and blasting design methods are mainly based on empirical design, which makes it difficult to fully consider the spatial variation of lithology in different sections and the mutual influence of complex structural surfaces during the excavation process, resulting in the failure to achieve the designed blasting effect, causing waste of resources and serious over-excavation and under-excavation, and increasing the difficulty of the project. Traditional means can no longer guarantee the quality and cost control during tunnel excavation. Even the over-excavation and concrete backfilling of some tunnel sections cause over-consumption of up to 5,000 yuan per linear meter. For example, the parameters and arrangement of smooth blasting holes are often insufficient to adapt to the changing geological environment of long and large tunnels. Especially when the geological conditions are extremely complex, the blasting parameters cannot be scientifically and reasonably adjusted in real time according to the tunnel section and lithology conditions, and the blasting design cannot be dynamically optimized according to the on-site working conditions. Summary of the invention

[0004] In order to dynamically optimize the blasting design according to the on-site working conditions, scientifically and rationally adjust the blasting parameters in real time, and avoid over-excavation, the present application provides a tunnel blasting profile over-excavation and under-excavation control method based on blasthole drilling parameters.

[0005] The present application provides a method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters, which adopts the following technical solutions:

[0006] A tunnel blasting profile over-break and under-break control method based on blasthole drilling parameters, comprising:

[0007] S1. Drilling blastholes by rock drill;

[0008] S2. Collecting drilling parameters during the drilling process, including the rotation speed, drilling pressure, torque and drilling speed of the rock drill during the drilling process;

[0009] S3, performing noise reduction processing on the drilling parameter data;

[0010] S4, obtaining the rock uniaxial compressive strength value R according to the drilling parameter data after noise reduction processing;

[0011] S5, obtaining the number N of structural surfaces per meter depth according to the drilling parameter data after noise reduction processing;

[0012] S6. Determine the explosive consumption q, the blasthole spacing a and the charge structure based on the uniaxial compressive strength value R and the number of structural surfaces per meter depth N.

[0013] Optionally, in step S2, a sensor is installed on the rock drill to collect drilling parameters during the drilling process.

[0014] Optionally, in step S3, data with large fluctuations in the initial stage and the stop stage of the rock drill are eliminated, and noise reduction processing is performed on the eliminated while-drilling parameter data.

[0015] Optionally, in step S4, the drilling parameter data after noise reduction processing is input into the prediction model, and the prediction model adopts a trained CNN-LSTM-Attention model; the drilling parameter data after noise reduction processing is input into the CNN-LSTM-Attention model to obtain the rock uniaxial compressive strength value R that changes with time during the drilling process.

[0016] Optionally, in the CNN-LSTM-Attention model training process, the spatial connection between different eigenvalues ​​in the drilling parameter data is first extracted through the CNN layer to obtain a data feature map, and the data feature map is converted into a real vector and passed to the LSTM layer. The LSTM layer introduces an input gate, a forget gate, and an output gate to alleviate the gradient disappearance and extract time series change information. The output vector of the LSTM layer is passed to the Attention layer. The Attention layer calculates the weighted average sum of the output vector of the LSTM layer, and outputs the uniaxial compressive strength value R of the sample through the fully connected layer. The weight when the prediction result is optimal during the training process is used as the weight of the prediction model.

[0017] Optionally, in step S5, the number of structural planes is the number of times at least two drilling parameters among the rotation speed, drilling pressure, torque and drilling speed of the rock drill simultaneously undergo sudden changes during the drilling process.

[0018] Optionally, in step S6,

[0019] The unit consumption of explosives q is determined by the uniaxial compressive strength value R and the number of structural surfaces per meter depth N;

[0020] The rock crushing energy W is defined according to the rock uniaxial compressive strength value R and the number of structural planes per meter depth N:

[0021] ; (1)

[0022] In formula (1), is the correction factor, based on the number of structural surfaces per meter depth Sure:

[0023] ; (2)

[0024] According to the energy relationship, rock crushing must satisfy the requirement that the energy released by the explosive is not less than the energy of rock crushing, that is:

[0025] ; (3)

[0026] Formula (3) is the energy released by the explosive, where E is:

[0027] ; (4)

[0028] In formula (4) is the explosive equivalent, The energy released by the explosion of 1gTNT is ;

[0029] The unit consumption of explosives q is:

[0030] ; (5).

[0031] Optionally, in step S6,

[0032] Hole spacing Determined by the uniaxial compressive strength value R and the number of structural surfaces per meter depth N;

[0033] Hole spacing for:

[0034] ; (6)

[0035] In formula (6) is the thickness of the light explosion layer, for:

[0036] ; (7)

[0037] In formula (7), is the blasthole diameter, f is the robustness coefficient, and the robustness coefficient f is determined by the uniaxial compressive strength value R of the rock;

[0038] ; (8)

[0039] The specific value of G is determined by the strength factor f and the number of structural surfaces per meter depth N;

[0040] When the strength coefficient f is not less than 6 and the number of structural surfaces per meter depth N is not more than 2, G is 11;

[0041] When the strength coefficient f is less than 6 and not less than 3, and the number of structural surfaces per meter depth N is not more than 2, G is 12;

[0042] When the strength coefficient f is less than 6 and not less than 3, and the number of structural surfaces per meter depth N is greater than 2, G is 13;

[0043] When the strength coefficient f is less than 3 and the number of structural surfaces per meter depth N is not greater than 2, G is 14;

[0044] When the strength coefficient f is less than 3 and the number of structural surfaces per meter depth N is greater than 2, G is 15.

[0045] Optionally, in step S6,

[0046] The charge structure is determined by the uniaxial compressive strength value R and the number of structural faces per meter depth N;

[0047] The charge structure specifically adopts an air-spaced uncoupled charge structure, in which the radial uncoupling coefficient is determined by the solidity coefficient f;

[0048] When the firmness factor f is not less than 6, the radial uncoupling factor is 1.25-1.50;

[0049] When the firmness factor f is not greater than 6 and not less than 3, the radial uncoupling factor is 1.50-2.00;

[0050] When the firmness factor f is less than 3, the radial uncoupling factor is 2.00-2.50;

[0051] The radial uncoupling coefficient is the ratio of the borehole diameter to the explosive diameter.

[0052] In summary, the present application includes at least one of the following beneficial technical effects:

[0053] Determine the unit consumption of explosives q, the spacing between blastholes a and the charge structure according to the uniaxial compressive strength value R and the number of structural surfaces per meter depth N. Dynamically adjust the unit consumption of explosives q, the spacing between blastholes a and the charge structure according to the uniaxial compressive strength value R and the number of structural surfaces per meter depth N obtained on site. Dynamically optimize the blasting design according to the on-site working conditions. Scientifically and reasonably adjust the blasting parameters in real time to avoid over-excavation, greatly improve the overall construction efficiency and ensure the safety and progress of the project.

[0054] With the help of measurement while drilling technology and model prediction, the utilization rate of drilling information is improved, and with the continuous expansion of sample size and optimization of algorithms, the accuracy of model prediction results is continuously improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The present invention is a schematic diagram of the overall structure of a tunnel blasting contour over-break and under-break control method based on blasthole drilling parameters.

[0056] Figure 2 It is a schematic diagram for showing the installation of various sensors on the rock drill in the embodiment of the present application.

[0057] Figure 3 It is used to show the schematic diagram of CNN-LSTM-Attention model.

[0058] Figure 4 It is a data diagram for displaying the rotation speed of the rock drill during the drilling process in the embodiment of the present application.

[0059] Figure 5 It is a graph for displaying the drilling pressure data of the rock drill during the drilling process in the embodiment of the present application.

[0060] Figure 6 It is a diagram for showing the torque data of the rock drill during the drilling process in the embodiment of the present application.

[0061] Figure 7 It is a graph for showing the drilling speed data of the rock drill during the drilling process in the embodiment of the present application.

[0062] Figure 8 It is a schematic diagram for showing the charging structure in the embodiment of the present application.

[0063] Explanation of the accompanying drawings: 1. Pressure sensor; 2. Torque / speed sensor; 3. Laser displacement sensor. DETAILED DESCRIPTION

[0064] The present application is further described in detail below in conjunction with all the accompanying drawings.

[0065] The embodiment of the present application discloses a method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters.

[0066] Reference Figure 1 , a tunnel blasting profile over-break and under-break control method based on blasthole drilling parameters, comprising:

[0067] S1. Drilling blastholes by rock drill;

[0068] S2. Collecting drilling parameters during the drilling process, including the rotation speed, drilling pressure, torque and drilling speed of the rock drill during the drilling process;

[0069] S3, performing noise reduction processing on the drilling parameter data;

[0070] S4, obtaining the rock uniaxial compressive strength value R according to the drilling parameter data after noise reduction processing;

[0071] S5, obtaining the number N of structural surfaces per meter depth according to the drilling parameter data after noise reduction processing;

[0072] S6. Determine the explosive consumption q, the blasthole spacing a and the charge structure based on the uniaxial compressive strength value R and the number of structural surfaces per meter depth N.

[0073] Reference Figure 1 , wherein, in step S2, a sensor is installed on the rock drill to collect drilling parameters during the drilling process.

[0074] Reference Figure 2 Specifically, the sensors include a pressure sensor 1, a torque / speed sensor 2, and a laser displacement sensor 3; the pressure sensor 1 records the propulsion force during drilling; the torque / speed sensor 2 collects torque data and speed data during drilling; the laser displacement sensor 3 collects the relationship between drilling depth and drilling time during drilling, and determines the drilling speed through the relationship between drilling depth and time. The assembly of sensors can ensure the real-time acquisition of drilling parameters under complex geological conditions without affecting the drilling of blastholes.

[0075] Among them, in step S3, the data with large fluctuations in the initial stage and the stop stage of the rock drill are eliminated, and the noise reduction processing is performed on the eliminated while drilling parameter data.

[0076] Specifically, if the drill is stuck or the equipment fails during the drilling process, the data collected while drilling will be quite different from that under normal circumstances, which will have a great impact on the judgment result. The collected data needs to be processed and the data collected under abnormal conditions needs to be eliminated. In addition, at the initial stage of the blasthole drilling process, the drill bit of the rock drill begins to contact the rock, and the various while drilling parameters increase significantly; at the end of the blasthole drilling, the various while drilling parameters fluctuate greatly due to the deceleration of the rock drill when it stops. The initial stage and the end data with large fluctuations due to the influence of operation are eliminated;

[0077] During the transmission process, the signal will be affected by factors such as the environment and the vibration of the rock drill and will be contaminated by noise. If the noise is not eliminated, the accuracy and reliability of the prediction results may be reduced. Therefore, noise reduction processing is required before the drilling data is input;

[0078] Through computing service equipment with data processing, network communication and program running functions, such as laptops, tablet computers or other electronic devices with the above functions, the computing service equipment removes abnormal data and noise from the collected drilling parameters.

[0079] Reference Figure 3 , wherein, in step S4, the drilling parameter data after noise reduction processing is input into the prediction model, and the prediction model adopts the trained CNN-LSTM-Attention model; the drilling parameter data after noise reduction processing is input into the CNN-LSTM-Attention model to obtain the rock uniaxial compressive strength value R that changes with time during the drilling process.

[0080] Specifically, in the training process of the CNN-LSTM-Attention model, the spatial connection between different eigenvalues ​​in the drilling parameter data is first extracted through the CNN layer to obtain the data feature map, and the data feature map is converted into a real vector and passed to the LSTM layer. The LSTM layer introduces an input gate, a forget gate, and an output gate to alleviate the gradient disappearance and extract the time series change information. The output vector of the LSTM layer is passed to the Attention layer. The Attention layer calculates the weighted average sum of the output vectors of the LSTM layer, and outputs the uniaxial compressive strength value R of the sample through the fully connected layer. The weight when the prediction result is optimal during the training process is used as the weight of the prediction model.

[0081] Wherein, in step S5, the number of structural planes is the number of times at least two drilling parameters among the rotation speed, drilling pressure, torque and drilling speed of the rock drill simultaneously undergo sudden changes during the drilling process.

[0082] Specifically, refer to Figures 4 to 7 The change of drilling parameters is closely related to the lithology. The existence of structural plane can be identified according to the change of drilling parameters during blasthole drilling. The specific method is as follows: the cracks, voids and weak interlayers in the structural plane generally have a short extension range. When encountering a structural plane, the drilling parameters will change instantaneously. After passing through the structural plane, they will return to a relatively stable stage. In order to eliminate the influence of the environment or the equipment itself, when at least two parameters change at the same location, it is considered that there is a structural plane.

[0083] Among them, in step S6,

[0084] The unit consumption of explosives q is determined by the uniaxial compressive strength value R and the number of structural surfaces per meter depth N;

[0085] The rock crushing energy W is defined according to the rock uniaxial compressive strength value R and the number of structural planes per meter depth N:

[0086] ; (1)

[0087] In formula (1), is the correction factor, based on the number of structural surfaces per meter depth Sure:

[0088] ; (2)

[0089] According to the energy relationship, rock crushing must satisfy the requirement that the energy released by the explosive is not less than the energy of rock crushing, that is:

[0090] ; (3)

[0091] Formula (3) is the energy released by the explosive, where E is:

[0092] ; (4)

[0093] In formula (4) is the explosive equivalent, The energy released by the explosion of 1gTNT is ;

[0094] The unit consumption of explosives q is:

[0095] ; (5).

[0096] Among them, in step S6,

[0097] Hole spacing Determined by the uniaxial compressive strength value R and the number of structural surfaces per meter depth N;

[0098] Hole spacing for:

[0099] ; (6)

[0100] In formula (6) is the thickness of the light explosion layer, for:

[0101] ; (7)

[0102] In formula (7), is the blasthole diameter, f is the robustness coefficient, and the robustness coefficient f is determined by the uniaxial compressive strength value R of the rock;

[0103] ; (8)

[0104] The specific value of G is determined by the strength factor f and the number of structural surfaces per meter depth N;

[0105] When the strength coefficient f is not less than 6 and the number of structural surfaces per meter depth N is not more than 2, G is 11;

[0106] When the strength coefficient f is less than 6 and not less than 3, and the number of structural surfaces per meter depth N is not more than 2, G is 12;

[0107] When the strength coefficient f is less than 6 and not less than 3, and the number of structural surfaces per meter depth N is greater than 2, G is 13;

[0108] When the strength coefficient f is less than 3 and the number of structural surfaces per meter depth N is not greater than 2, G is 14;

[0109] When the strength coefficient f is less than 3 and the number of structural surfaces per meter depth N is greater than 2, G is 15.

[0110] Reference Figure 8 , wherein, in step S6,

[0111] The charge structure is determined by the uniaxial compressive strength value R and the number N of structural faces per meter depth.

[0112] The charge structure specifically adopts an air-gap uncoupled charge structure, which corresponds to the radial uncoupled coefficient. The uncoupled coefficient is an important parameter in controlled blasting and is mainly used for pre-splitting blasting and smooth blasting. The uncoupled coefficient is the ratio of the borehole diameter to the explosive diameter. When charging along the radial length direction in the borehole, the air-gap charging method is used to reduce the charge amount, making full use of the gas wedge effect during the detonation process to destroy the rock mass. The radial uncoupled charge is that the explosive diameter is not completely equal to the borehole diameter, and the increased effect of the transflection of the explosive gas on the borehole wall can be used to provide a higher detonation pressure.

[0113] The radial uncoupling coefficient is determined by the robustness coefficient f;

[0114] When the firmness factor f is not less than 6, the radial uncoupling factor is 1.25-1.50;

[0115] When the firmness factor f is not greater than 6 and not less than 3, the radial uncoupling factor is 1.50-2.00;

[0116] When the firmness factor f is less than 3, the radial uncoupling factor is 2.00-2.50.

[0117] There are air gaps between each section of the charge column. The rock damage is small at the air gap. The position of the air column for interval charging should be set at the structural surface as much as possible to avoid the formation of uncontrollable cracks and over-excavation. The structural surface position is the sudden change of the drilling parameters. The distance between the structural surface and the hole mouth can be determined based on the laser displacement sensor data.

[0118] Before charging, the blasthole needs to be inspected to ensure that there is no rock debris or water in the hole. Figure 8 The section view AA is used to show the position of the explosive roll in the blasthole. When charging, it is necessary to strictly follow the charge quantity and charge structure required by the design, and ensure that the explosives are evenly distributed in the blasthole. After charging, the gun mud is used for blocking to prevent flying rocks when the explosives explode, ensuring the safety of personnel and equipment.

[0119] The plugging length of the taphole mud :

[0120] ; (9)

[0121] In formula (9), is the borehole diameter.

[0122] The implementation principle of a method for controlling over- and under-excavation of a tunnel blasting profile based on borehole drilling parameters in an embodiment of the present application is as follows: determining the unit consumption of explosives q, the borehole spacing a, and the charging structure according to the uniaxial compressive strength value R and the number of structural surfaces per meter depth N; dynamically adjusting the unit consumption of explosives q, the borehole spacing a, and the charging structure according to the uniaxial compressive strength value R and the number of structural surfaces per meter depth N obtained on site; dynamically optimizing the blasting design according to the on-site working conditions; scientifically and rationally adjusting the blasting parameters in real time to avoid over-excavation, thereby greatly improving the overall construction efficiency and ensuring the safety and progress of the project.

[0123] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters, characterized in that: include: S1. Drilling blastholes by rock drill; S2. Collecting drilling parameters during the drilling process, including the rotation speed, drilling pressure, torque and drilling speed of the rock drill during the drilling process; S3, performing noise reduction processing on the drilling parameter data; S4, obtaining the rock uniaxial compressive strength value R according to the drilling parameter data after noise reduction processing; In step S4, the drilling parameter data after noise reduction processing is input into the prediction model, and the prediction model adopts the trained CNN-LSTM-Attention model, and the drilling parameter data after noise reduction processing is input into the CNN-LSTM-Attention model to obtain the rock uniaxial compressive strength value R that changes with time during the drilling process; S5, obtaining the number N of structural surfaces per meter depth according to the drilling parameter data after noise reduction processing; In step S5, the number N of structural planes is the number of times at least two drilling parameters of the rock drill, namely, the rotation speed, drilling pressure, torque and drilling speed, suddenly change simultaneously during the drilling process; S6. Determine the explosive consumption q, the blasthole spacing a and the charge structure according to the uniaxial compressive strength value R and the number N of structural surfaces per meter depth; The unit consumption of explosives q is: ,in, is the explosive equivalent, The energy released by the explosion of 1gTNT is is the correction factor, According to the number of structural surfaces per meter depth Sure; Hole spacing Determined by the uniaxial compressive strength value R and the number of structural surfaces per meter depth N; Hole spacing for: ；（6） In formula (6) is the thickness of the light explosion layer, for: ；（7） In formula (7), is the blasthole diameter, f is the robustness coefficient, and the robustness coefficient f is determined by the uniaxial compressive strength value R of the rock; ；（8） The specific value of G is determined by the strength factor f and the number of structural surfaces per meter depth N; The charge structure specifically adopts an air-spaced uncoupled charge structure, in which the radial uncoupling coefficient is determined by the robustness coefficient f.

2. The method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters according to claim 1 is characterized in that ,In step S2, a sensor is installed on the rock drill to collect drilling parameters during the drilling process.

3. The method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters according to claim 1, characterized in that: In step S3, the data with large fluctuations in the initial stage and the stop stage of the rock drill are eliminated, and the eliminated while-drilling parameter data are subjected to noise reduction processing.

4. The method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters according to claim 1, characterized in that: In the training process of the CNN-LSTM-Attention model, the spatial connection between different eigenvalues ​​in the drilling parameter data is first extracted through the CNN layer to obtain the data feature map, and the data feature map is converted into a real vector and passed to the LSTM layer. The LSTM layer introduces an input gate, a forget gate, and an output gate to alleviate the gradient disappearance and extract the time series change information. The output vector of the LSTM layer is passed to the Attention layer. The Attention layer calculates the weighted average sum of the output vector of the LSTM layer, and outputs the uniaxial compressive strength value R of the sample through the fully connected layer. The weight when the prediction result is optimal during the training process is used as the weight of the prediction model.

5. The method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters according to claim 1, characterized in that: In step S6, The unit consumption of explosives q is determined by the uniaxial compressive strength value R and the number of structural surfaces per meter depth N; The rock crushing energy W is defined according to the rock uniaxial compressive strength value R and the number of structural planes per meter depth N: ； （1） In formula (1), is the correction factor, based on the number of structural surfaces per meter depth Sure: ；（2） According to the energy relationship, rock crushing must satisfy the requirement that the energy released by the explosive is not less than the energy of rock crushing, that is: ；（3） Formula (3) is the energy released by the explosive, where E is: ；（4） In formula (4) is the explosive equivalent, The energy released by the explosion of 1gTNT is ; The unit consumption of explosives q is: ；（5）。 6. The method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters according to claim 1, characterized in that: In step S6, When the strength coefficient f is not less than 6 and the number of structural surfaces per meter depth N is not more than 2, G is 11; When the strength coefficient f is less than 6 and not less than 3, and the number of structural surfaces per meter depth N is not more than 2, G is 12; When the strength coefficient f is less than 6 and not less than 3, and the number of structural surfaces per meter depth N is greater than 2, G is 13; When the strength coefficient f is less than 3 and the number of structural surfaces per meter depth N is not greater than 2, G is 14; When the strength coefficient f is less than 3 and the number of structural surfaces per meter depth N is greater than 2, G is 15.

7. The method for controlling over-break and under-break of tunnel blasting profile based on blasthole drilling parameters according to claim 6, characterized in that: In step S6, The charge structure is determined by the uniaxial compressive strength value R and the number of structural faces per meter depth N; The charge structure specifically adopts an air-spaced uncoupled charge structure, in which the radial uncoupling coefficient is determined by the solidity coefficient f; When the firmness factor f is not less than 6, the radial uncoupling factor is 1.25-1.50; When the firmness factor f is not greater than 6 and not less than 3, the radial uncoupling factor is 1.50-2.00; When the firmness factor f is less than 3, the radial uncoupling factor is 2.00-2.50; The radial uncoupling coefficient is the ratio of the borehole diameter to the explosive diameter.

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