A double-line protection net and its design method

Abstract

The present invention discloses a double-line protective net and its design method, belonging to the field of protective nets for rockfall impacts. The net comprises an upper layer and a lower layer for intercepting rockfalls from the same source area. The upper and lower layers are arranged sequentially from top to bottom along a slope, with the distance between the upper and lower layers exceeding the designed deformation of the upper layer when impacted, and the distance between the lower layer and the protected object exceeding the elongation of the lower layer. The double-line protective net and its design method improve the rockfall interception effect by setting up the double-line protective net.

Description

Technical Field

[0001] The present invention relates to the technical field of protection nets for rockfall impact, in particular to a double-line protection net and a design method thereof. Background Art

[0002] Rockfall occurs when a rock mass breaks away from its parent body and rapidly moves down a steep mountain slope, colliding with the slope, leaping, bouncing, and sliding, before finally coming to rest on a flat surface or near an obstacle. Its rapid, short-lived, sudden, and highly unpredictable movement can quickly cause massive damage to everything in its path.

[0003] In order to avoid the losses caused by rockfall disasters, it is generally necessary to use a protective net to intercept the falling rocks. The existing protective net structure is as follows:

[0004] CN202210849661.6 discloses a high and steep slope dangerous rock and rockfall protection net system, which includes an anchor support component, a protection net, a signal receiving and feedback component and a battery life component; the anchor support component includes a plurality of columns spaced apart on the steep slope, the columns are arranged to be inclined upward, and the protection net is arranged between adjacent columns; the signal receiving and feedback component is arranged on the protection net, and the signal receiving and feedback component is used to detect and feedback rockfall events; the battery life component is used to charge the signal receiving and feedback component, and the battery life component generates electricity through wind power.

[0005] It can be seen that most of the existing protective nets are single-line protective nets, which are less effective in intercepting high and steep rockfalls. Summary of the Invention

[0006] The purpose of the present invention is to provide a double-line protection net and a design method thereof to solve the above technical problems.

[0007] To achieve the above-mentioned object, the present invention provides a double-line protection net, comprising an upper protection net and a lower protection net for intercepting falling rocks from the same source area, wherein the upper protection net and the lower protection net are arranged in sequence from top to bottom along a slope, and the distance between the upper protection net and the lower protection net is greater than the designed deformation of the upper protection net when subjected to an impact, and the distance between the lower protection net and the protected object is greater than the elongation of the lower protection net;

[0008] The maximum heights of the upper and lower protective nets must meet the following conditions:

[0009] ;

[0010] ;

[0011] Where, Indicates the maximum height of the upper protective net; Indicates the design height of the upper protective net; Impact rockfall The safety factor of the trajectory height is related to the , Indicates impact rockfall The diameter of Indicates impact rockfall exist The speed of time, Indicates impact rockfall quality, is the acceleration due to gravity, Indicates the slope angle; Indicates safety margin; Indicates the maximum height of the lower protective net; Indicates the design height of the lower protective net.

[0012] A design method for a double-line protective net includes the following steps:

[0013] S1. Performing an initial trajectory analysis and determining whether to install a double-line protection net based on the initial trajectory analysis result, and when it is determined that the double-line protection net is to be installed, executing step S2;

[0014] S2. Upward line design and analysis: Set the height of the slope to The upper protection net is located at the bottom of the protective net, and a trajectory analysis is performed. Based on the results of the trajectory analysis, the impact rockfall intercepted by the upper protection net is determined. , impact rockfall not intercepted by the upper protective net , impact rockfalls that were blocked but not intercepted by the upper protective net ;

[0015] S3. Downline line design: Based on the proportion of impact rocks blocked by the upper protection net but not intercepted to the number of impact rocks reaching the upper protection net, and the proportion of impact rocks not intercepted by the upper protection net to the number of impact rocks reaching the upper protection net, determine the trajectory analysis method to be applied, and combine the maximum interception height of the lower protection net to determine the minimum energy absorption capacity and design height required for the lower protection net.

[0016] Preferably, in step S1, based on the initial trajectory analysis, it is determined whether the single protection net can meet the safety formula. If so, a single protection net is set, otherwise a double-line protection net is set;

[0017] It specifically includes the following steps:

[0018] S11. Identify potential rockfalls on slopes based on images captured by drones.

[0019] Using drones to capture aerial images, the pre-processed images are stitched together to form a slope image. The slope's edges and surface features are then extracted. Based on feature point matching and stereo vision principles, the two-dimensional image is converted into a three-dimensional model to obtain the slope's surface elevation information. The slope value of each rock on the slope is calculated based on the three-dimensional model. The slope value of each rock is then compared with a set threshold, and rocks with slope values ​​greater than the threshold are considered potential rockfalls.

[0020] S12. Evaluate the probability of potential rockfall release. Consider potential rockfalls with a release probability greater than a set threshold as impact rockfalls. The probability of potential rockfall release is expressed as follows:

[0021] ;

[0022] Where, They represent the earthquake factors, rainfall factors, and weathering factors that trigger potential rockfall release;

[0023] S13. Based on the 3D model, obtain the initial trajectory and kinetic energy of the impact rockfall:

[0024] ;

[0025] ;

[0026] ;

[0027] ;

[0028] Where, Indicates impact rockfall exist Position at the moment; Represents the impact rockfall obtained from the 3D model The source location; Indicates impact rockfall Acceleration exist Directional component; Indicates impact rockfall In position Kinetic energy at Indicates impact rockfall density;

[0029] in,

[0030] ;

[0031] Where, It represents the friction coefficient between the impact rockfall and the slope surface;

[0032] S14: Input the position of the single-line protection net into the trajectory and kinetic energy formula of the impact rockfall described in step S13 to obtain the kinetic energy of the impact rockfall reaching the single-line protection net. and height , the kinetic energy and height Enter the security formula, the security formula is as follows:

[0033] ;

[0034] Where, Indicates the design energy absorption capacity of the single-line protection net; Indicates the height tolerance of impact rockfall considering its shape; Indicates the design height of the single-line protection net;

[0035] S15. When the safety formula described in step S14 is met, a single-line protection net is set; otherwise, a double-layer protection net is set.

[0036] Preferably, in step S2, a trajectory analysis process is: set the height on the slope to The maximum interception speed is calculated based on the upper protective net's designed energy absorption capacity:

[0037] ;

[0038] Where, Indicates the maximum interception speed; Indicates the designed energy absorption capacity of the upper protective net; Indicates impact rockfall The quality characteristic value of 、 、 Respectively represent and test impact rockfall Mass, speed and the designed energy absorption capacity of the upper protective net associated safety factors;

[0039] Impact rocks with a speed lower than the maximum interception speed and a height lower than the design height of the upper protection net are regarded as impact rocks intercepted by the upper protection net. ;

[0040] Impact rocks with a speed greater than the maximum interception speed and a height lower than the design height of the upper protection net are considered as impact rocks that are blocked but not intercepted by the upper protection net. , and the number of impact rockfalls is ,in, The number of rockfalls that were blocked but not intercepted by the upper protection net accounts for the number of rockfalls that reached the upper protection net. proportion;

[0041] The impact rockfall that is higher than the design height of the upper protection net is regarded as the impact rockfall that is not intercepted by the upper protection net. , and impact rockfall The number of ,in, Indicates the percentage of rockfall that is not intercepted by the upper protection net to the total number of rockfall that reaches the upper protection net. proportion.

[0042] Preferably, step S3 specifically includes the following steps:

[0043] S31. Determine the trajectory analysis method: and When the upper protection net is located, the secondary trajectory analysis is performed on the source area, where the impact rockfall Initial velocity The expression is as follows:

[0044] ;

[0045] Where, It means that when analyzing the energy distribution of the impact rockfall reaching the upper protection net under the premise of considering only the upper protection net, the first percentile, ;

[0046] Impact rockfall Initial height The expression is as follows:

[0047] ;

[0048] Where, It means that when analyzing the height distribution of the impact rockfall reaching the upper protection net under the premise of considering only the upper protection net, the first percentile, and ;

[0049] when and When , execute the first trajectory analysis result or the second trajectory analysis result;

[0050] when and , merge the results of the primary and secondary trajectory analysis and create a subset containing the impact rockfall height and velocity:

[0051] ;

[0052] Where, Indicates the number of subsets; Indicates the number of impact rocks that reach the lower protective net;

[0053] S32. Calculate the minimum energy absorption capacity and design height required for the lower protective net:

[0054] ;

[0055] ;

[0056] Where, Indicates the design height of the lower protective net; Indicates the height characteristic value of the lower protection net in a trajectory analysis; Indicates the height eigenvalue of the lower protection net in the secondary trajectory analysis; Represents the energy absorption capacity characteristic value of the lower protective net in a trajectory analysis; represents the energy absorption capacity characteristic value of the lower protective net in the secondary trajectory analysis;

[0057] S33. Evaluate the energy absorption level of the lower protective net:

[0058] Calculate the ratio of the impact rockfall that is intercepted and stopped by the lower protection net to the impact rockfall that reaches the lower protection net. :

[0059] ;

[0060] Where, It indicates the ratio of the impact rockfall that is intercepted and stopped by the lower protection net to the impact rockfall that reaches the position of the lower protection net; Indicates the falling rocks that are not intercepted by the upper protection net and reach the lower protection net; Indicates that the impact rockfall is blocked by the upper protection net but not intercepted and reaches the lower protection net. When performing secondary trajectory analysis, ; It represents the ratio of the number of impact rockfalls intercepted by the double-line protection net to the total number of impact rockfalls; Indicates the number of impact rockfalls that are not intercepted by the lower protection net;

[0061] when and as well as or When , we simplify to:

[0062] ;

[0063] Take the velocity distribution of the intercepted impact rockfall trajectory Percentile values ​​as , and use Evaluate the energy absorption level of the lower protective net.

[0064] Therefore, the present invention adopts the above-mentioned double-line protection net and its design method, which has the following beneficial effects:

[0065] 1. Double protection of upper and lower protective nets: By setting up two layers of protective nets, a multi-level safety barrier is formed. The upper protective net first intercepts most of the impact of falling rocks, reducing the pressure on the lower protective net. Even if some falling rocks are not completely intercepted, they can be effectively handled in the second line of defense. The double-layer design greatly improves the reliability and safety of the protection system;

[0066] 2. Dynamic adjustment based on trajectory analysis results: This method not only relies on static design parameters but also incorporates dynamic trajectory analysis. By performing an initial trajectory analysis and multiple subsequent analyses, the movement path of falling rocks and their impact on the protection net can be evaluated in real time, thereby optimizing the height and energy absorption capacity of the protection net. This allows the protection system to better adapt to the actual needs of different environmental conditions.

[0067] 3. Efficient resource utilization: By accurately calculating the interception ratio of the upper protection net and the number of uninterrupted rockfalls, as well as the energy absorption capacity and design height required by the lower protection net, we ensure that each layer of protection net can maximize its effectiveness under the most appropriate conditions. This not only improves the protection effect, but also reduces unnecessary material waste and construction costs.

[0068] 4. Flexible response to different terrain and rockfall situations: This method can be adjusted according to different terrain characteristics (such as slope angle) and rockfall characteristics. For example, the specific setting of the slope is taken into account when determining the height of the upper protection net, while the actual interception effect of the upper protection net is incorporated into the design parameters of the lower protection net. This makes the design solution widely applicable to various complex natural environments.

[0069] 5. Comprehensive coverage of potential risk points: By implementing protective measures in steps, with clear objectives and inspection standards for each step, the entire protection system, from design to construction to final operation, can achieve optimal safety protection. This is especially important for critical facilities located in mountainous areas or areas prone to geological disasters such as landslides.

[0070] In summary, the double-line protective net and design method thereof described in the present invention, through the application of scientific and reasonable structural layout and technical means, not only improve the protective performance, but also achieve effective utilization of resources and maximization of environmental adaptability.

[0071] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 This is a structural schematic diagram of a double-line protection net of the present invention.

[0073] Reference numerals

[0074] 1. Upper protective net; 2. Lower protective net. DETAILED DESCRIPTION

[0075] In order to make the purposes, technical solutions and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar numbers throughout represent the same or similar elements or elements with the same or similar functions.

[0076] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0077] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0078] like Figure 1 As shown, a double-line protection net includes an upper protection net 1 and a lower protection net 2 for intercepting falling rocks from the same source area. The upper protection net 1 and the lower protection net 2 are arranged in sequence from top to bottom along the slope, and the distance between the upper protection net 1 and the lower protection net 2 is greater than the designed deformation of the upper protection net 1 when subjected to impact, and the distance between the lower protection net 2 and the protected object is greater than the elongation of the lower protection net 2;

[0079] The maximum heights of the upper protective net 1 and the lower protective net 2 meet the following conditions:

[0080] ;

[0081] ;

[0082] Where, Indicates the maximum height of the upper protective net; Indicates the design height of the upper protective net; Impact rockfall The safety factor of the trajectory height is related to the , Indicates impact rockfall The diameter of Indicates impact rockfall exist The speed of time, Indicates impact rockfall quality, is the acceleration due to gravity, Indicates the slope angle; Indicates safety margin; Indicates the maximum height of the lower protective net; Indicates the design height of the lower protective net.

[0083] A design method for a double-line protective net includes the following steps:

[0084] S1. Performing an initial trajectory analysis and determining whether to install a double-line protection net based on the initial trajectory analysis result, and when it is determined that the double-line protection net is to be installed, executing step S2;

[0085] In step S1, based on the initial trajectory analysis, it is determined whether the single protection net can meet the safety formula. If it does, a single protection net is set up; otherwise, a double-line protection net is set up;

[0086] It specifically includes the following steps:

[0087] S11. Identify potential rockfalls on slopes based on images captured by drones.

[0088] Aerial drone photography is used to capture images (no double-line protective netting is installed on the slope at this time). After preprocessing, the captured images are stitched together to form a slope image. The slope's edges and surface features are then extracted. Based on feature point matching and stereo vision principles, the two-dimensional image is converted into a three-dimensional model to obtain the slope's surface elevation information. The slope value of each rock on the slope is calculated based on the three-dimensional model. The slope value of each rock is then compared with a set threshold (60° in this embodiment). Rocks with slope values ​​greater than the set threshold are considered potential rockfalls.

[0089] S12. Evaluate the probability of potential rockfall release. Consider potential rockfalls with a release probability greater than a set threshold as impact rockfalls. The probability of potential rockfall release is expressed as follows:

[0090] ;

[0091] Where, They represent the earthquake factors, rainfall factors, and weathering factors that trigger potential rockfall release;

[0092] S13. Based on the 3D model, obtain the initial trajectory and kinetic energy of the impact rockfall:

[0093] ;

[0094] ;

[0095] ;

[0096] ;

[0097] Where, Indicates impact rockfall exist Position at the moment; Represents the impact rockfall obtained from the 3D model The source location; Indicates impact rockfall Acceleration exist Directional component; Indicates impact rockfall In position Kinetic energy at Indicates impact rockfall density;

[0098] in,

[0099] ;

[0100] Where, It represents the friction coefficient between the impact rockfall and the slope surface;

[0101] S14: Input the position of the single-line protection net into the trajectory and kinetic energy formula of the impact rockfall described in step S13 to obtain the kinetic energy of the impact rockfall reaching the single-line protection net. and height , the kinetic energy and height Enter the security formula, the security formula is as follows:

[0102] ;

[0103] Where, Indicates the design energy absorption capacity of the single-line protection net; Indicates the height tolerance of impact rockfall considering its shape; Indicates the design height of the single-line protection net;

[0104] S15. When the safety formula described in step S14 is met, a single-line protection net is set; otherwise, a double-layer protection net is set.

[0105] S2. Upward line design and analysis: Set the height of the slope to The upper protection net is located at the bottom of the protective net, and a trajectory analysis is performed. Based on the results of the trajectory analysis, the impact rockfall intercepted by the upper protection net is determined. , impact rockfall not intercepted by the upper protective net , impact rockfalls that were blocked but not intercepted by the upper protective net ;

[0106] In step S2, a trajectory analysis process is as follows: set the height on the slope to The maximum interception speed is calculated based on the upper protective net's designed energy absorption capacity:

[0107] ;

[0108] Where, Indicates the maximum interception speed; Indicates the designed energy absorption capacity of the upper protective net; Indicates impact rockfall The quality characteristic value of 、 、 Respectively represent and test impact rockfall Mass, speed and the designed energy absorption capacity of the upper protective net associated safety factors;

[0109] Impact rocks with a speed lower than the maximum interception speed and a height lower than the design height of the upper protection net are regarded as impact rocks intercepted by the upper protection net. ;

[0110] Impact rocks with a speed greater than the maximum interception speed and a height lower than the design height of the upper protection net are considered as impact rocks that are blocked but not intercepted by the upper protection net. , and the number of impact rockfalls is ,in, The number of rockfalls that were blocked but not intercepted by the upper protection net accounts for the number of rockfalls that reached the upper protection net. proportion;

[0111] The impact rockfall that is higher than the design height of the upper protection net is regarded as the impact rockfall that is not intercepted by the upper protection net. , and impact rockfall The number of ,in, Indicates the percentage of rockfall that is not intercepted by the upper protection net to the total number of rockfall that reaches the upper protection net. proportion.

[0112] S3. Downline line design: Based on the proportion of impact rocks blocked by the upper protection net but not intercepted to the number of impact rocks reaching the upper protection net, and the proportion of impact rocks not intercepted by the upper protection net to the number of impact rocks reaching the upper protection net, determine the trajectory analysis method to be applied, and combine the maximum interception height of the lower protection net to determine the minimum energy absorption capacity and design height required for the lower protection net.

[0113] Step S3 specifically includes the following steps:

[0114] S31. Determine the trajectory analysis method: and When the upper protection net is located, the secondary trajectory analysis is performed on the source area, where the impact rockfall Initial velocity The expression is as follows:

[0115] ;

[0116] Where, It means that when analyzing the energy distribution of the impact rockfall reaching the upper protection net under the premise of considering only the upper protection net, the first percentile, ;

[0117] Impact rockfall Initial height The expression is as follows:

[0118] ;

[0119] Where, It means that when analyzing the height distribution of the impact rockfall reaching the upper protection net under the premise of considering only the upper protection net, the first percentile, and ;

[0120] when and When , execute the first trajectory analysis result or the second trajectory analysis result;

[0121] when and , merge the results of the primary and secondary trajectory analysis and create a subset containing the impact rockfall height and velocity:

[0122] ;

[0123] Where, Indicates the number of subsets; Indicates the number of impact rocks that reach the lower protective net;

[0124] S32. Calculate the minimum energy absorption capacity and design height required for the lower protective net:

[0125] ;

[0126] ;

[0127] Where, Indicates the design height of the lower protective net; Indicates the height characteristic value of the lower protection net in a trajectory analysis; Indicates the height eigenvalue of the lower protection net in the secondary trajectory analysis; Represents the energy absorption capacity characteristic value of the lower protective net in a trajectory analysis; represents the energy absorption capacity characteristic value of the lower protective net in the secondary trajectory analysis;

[0128] S33. Evaluate the energy absorption level of the lower protective net:

[0129] Calculate the ratio of the impact rockfall that is intercepted and stopped by the lower protection net to the impact rockfall that reaches the lower protection net. :

[0130] ;

[0131] Where, It indicates the ratio of the impact rockfall that is intercepted and stopped by the lower protection net to the impact rockfall that reaches the position of the lower protection net; Indicates the falling rocks that are not intercepted by the upper protection net and reach the lower protection net; Indicates that the impact rockfall is blocked by the upper protection net but not intercepted and reaches the lower protection net. When performing secondary trajectory analysis, ; It represents the ratio of the number of impact rockfalls intercepted by the double-line protection net to the total number of impact rockfalls; Indicates the number of impact rockfalls that are not intercepted by the lower protection net;

[0132] when and as well as or When , we simplify to:

[0133] ;

[0134] Take the velocity distribution of the intercepted impact rockfall trajectory Percentile values ​​as , and use Evaluate the energy absorption level of the lower protective net.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A double-line protective net, characterized by: It includes an upper protection net and a lower protection net for intercepting falling rocks from the same source area. The upper and lower protection nets are arranged in sequence from top to bottom along the slope. The distance between the upper and lower protection nets is greater than the designed deformation of the upper protection net when subjected to impact, and the distance between the lower protection net and the protected object is greater than the elongation of the lower protection net. The maximum heights of the upper and lower protective nets must meet the following conditions: ； ； Where, Indicates the maximum height of the upper protective net; Indicates the design height of the upper protective net; Impact rockfall The safety factor of the trajectory height is related to the , Indicates impact rockfall The diameter of Indicates impact rockfall exist The speed of time, Indicates impact rockfall quality, is the acceleration due to gravity, Indicates the slope angle; Indicates safety margin; Indicates the maximum height of the lower protective net; Indicates the design height of the lower protective net.

2. A design method for a double-line protective net, characterized by: The following steps are involved: S1. Performing an initial trajectory analysis, and determining whether to install the double-line protection net according to claim 1 based on the initial trajectory analysis result, and executing step S2 when it is determined that the double-line protection net is to be installed; S2. Upward line design and analysis: Set the height of the slope to The upper protection net is located at the bottom of the protective net, and a trajectory analysis is performed. Based on the results of the trajectory analysis, the impact rockfall intercepted by the upper protection net is determined. , impact rockfall not intercepted by the upper protective net , impact rockfalls that were blocked but not intercepted by the upper protective net ; S3. Downline line design: Based on the proportion of impact rocks blocked by the upper protection net but not intercepted to the number of impact rocks reaching the upper protection net, and the proportion of impact rocks not intercepted by the upper protection net to the number of impact rocks reaching the upper protection net, determine the trajectory analysis method to be applied, and combine the maximum interception height of the lower protection net to determine the minimum energy absorption capacity and design height required for the lower protection net.

3. A method for designing a double-wire protective net according to claim 2, characterized in that: In step S1, based on the initial trajectory analysis, it is determined whether the single protection net can meet the safety formula. If it does, a single protection net is set up; otherwise, a double-line protection net is set up; It specifically includes the following steps: S11. Identify potential rockfalls on slopes based on images captured by drones. Using drones to capture aerial images, the pre-processed images are stitched together to form a slope image. The slope's edges and surface features are then extracted. Based on feature point matching and stereo vision principles, the two-dimensional image is converted into a three-dimensional model to obtain the slope's surface elevation information. The slope value of each rock on the slope is calculated based on the three-dimensional model. The slope value of each rock is then compared with a set threshold, and rocks with slope values ​​greater than the threshold are considered potential rockfalls. S12. Evaluate the probability of potential rockfall release. Consider potential rockfalls with a release probability greater than a set threshold as impact rockfalls. The probability of potential rockfall release is expressed as follows: ； Where, They represent the earthquake factors, rainfall factors, and weathering factors that trigger potential rockfall release; S13. Based on the 3D model, obtain the initial trajectory and kinetic energy of the impact rockfall: ； ； ； ； Where, Indicates impact rockfall exist Position at the moment; Represents the impact rockfall obtained from the 3D model The source location; Indicates impact rockfall Acceleration exist Directional component; Indicates impact rockfall In position Kinetic energy at Indicates impact rockfall density; in, ； Where, It represents the friction coefficient between the impact rockfall and the slope surface; S14: Input the position of the single-line protection net into the trajectory and kinetic energy formula of the impact rockfall described in step S13 to obtain the kinetic energy of the impact rockfall reaching the single-line protection net. and height , the kinetic energy and height Enter the security formula, the security formula is as follows: ； Where, Indicates the design energy absorption capacity of the single-line protection net; Indicates the height tolerance of impact rockfall considering its shape; Indicates the design height of the single-line protection net; S15. When the safety formula described in step S14 is met, a single-line protection net is set; otherwise, a double-layer protection net is set.

4. A method for designing a double-wire protective net according to claim 3, characterized in that: In step S2, a trajectory analysis process is as follows: set the height on the slope to The maximum interception speed is calculated based on the upper protective net's designed energy absorption capacity: ； Where, Indicates the maximum interception speed; Indicates the designed energy absorption capacity of the upper protective net; Indicates impact rockfall The quality characteristic value of 、 、 Respectively represent and test impact rockfall Mass, speed and the designed energy absorption capacity of the upper protective net associated safety factors; Impact rocks with a speed lower than the maximum interception speed and a height lower than the design height of the upper protection net are regarded as impact rocks intercepted by the upper protection net. ; Impact rocks with a speed greater than the maximum interception speed and a height lower than the design height of the upper protection net are considered as impact rocks that are blocked but not intercepted by the upper protection net. , and the number of impact rockfalls is ,in, The number of rockfalls that were blocked but not intercepted by the upper protection net accounts for the number of rockfalls that reached the upper protection net. proportion; The impact rockfall that is higher than the design height of the upper protection net is regarded as the impact rockfall that is not intercepted by the upper protection net. , and impact rockfall The number of ,in, Indicates the percentage of rockfall that is not intercepted by the upper protection net to the total number of rockfall that reaches the upper protection net. proportion.

5. A method for designing a double-wire protective net according to claim 4, characterized in that: Step S3 specifically includes the following steps: S31. Determine the trajectory analysis method: and When the upper protection net is located, the secondary trajectory analysis is performed on the source area, where the impact rockfall Initial velocity The expression is as follows: ； Where, It means that when analyzing the energy distribution of the impact rockfall reaching the upper protection net under the premise of considering only the upper protection net, the first percentile, ; Impact rockfall Initial height The expression is as follows: ； Where, It means that when analyzing the height distribution of the impact rockfall reaching the upper protection net under the premise of considering only the upper protection net, the first percentile, and ; when and When , execute the first trajectory analysis result or the second trajectory analysis result; when and , merge the results of the primary and secondary trajectory analysis and create a subset containing the impact rockfall height and velocity: ； Where, Indicates the number of subsets; Indicates the number of impact rocks that reach the lower protective net; S32. Calculate the minimum energy absorption capacity and design height required for the lower protective net: ； ； Where, Indicates the design height of the lower protective net; Indicates the height characteristic value of the lower protection net in a trajectory analysis; Indicates the height eigenvalue of the lower protection net in the secondary trajectory analysis; Represents the energy absorption capacity characteristic value of the lower protective net in a trajectory analysis; represents the energy absorption capacity characteristic value of the lower protective net in the secondary trajectory analysis; S33. Evaluate the energy absorption level of the lower protective net: Calculate the ratio of the impact rockfall that is intercepted and stopped by the lower protection net to the impact rockfall that reaches the lower protection net. : ； Where, It indicates the ratio of the impact rockfall that is intercepted and stopped by the lower protection net to the impact rockfall that reaches the position of the lower protection net; Indicates the falling rocks that are not intercepted by the upper protection net and reach the lower protection net; Indicates that the impact rockfall is blocked by the upper protection net but not intercepted and reaches the lower protection net. When performing secondary trajectory analysis, ; It represents the ratio of the number of impact rockfalls intercepted by the double-line protection net to the total number of impact rockfalls; Indicates the number of impact rockfalls that are not intercepted by the lower protection net; when and as well as or When , we simplify to: ； Take the velocity distribution of the intercepted impact rockfall trajectory Percentile values ​​as , and use Evaluate the energy absorption level of the lower protective net.

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