Double-wire protective net and design method thereof

Abstract

The invention discloses a double-line protective net and a design method thereof, and belongs to the field of protective nets for rockfall impact, the double-line protective net comprises an upper protective net and a lower protective net which are used for intercepting rockfall in the same source area, and the upper protective net and the lower protective net are sequentially arranged from top to bottom along a slope; the distance between the upper-layer protective net and the lower-layer protective net is greater than the design deformation of the upper-layer protective net when the upper-layer protective net is impacted, and the distance between the lower-layer protective net and a protected object is greater than the elongation of the lower-layer protective net. According to the double-line protective net and the design method thereof, by arranging the double-line protective net, the rockfall interception effect is improved.

Description

Technical Field

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

[0002] Rockfall refers to the process in which a rock mass separates from the parent body, undergoes movements such as collision, leap, bounce, and slide with the slope surface, moves rapidly downward along the steep mountain slope, and finally stops moving at a gentle place or near an obstacle. Its movement speed is fast, the time is short, the suddenness is strong, and the uncertainty is high. Once it occurs, it will cause great damage to all things on the rockfall trajectory in a very short time.

[0003] In order to avoid the losses caused by the occurrence of rockfall disasters, it is generally necessary to intercept rockfalls with the help of a protection net. The existing protection net structures are as follows: CN202210849661.6 discloses a protection net system for dangerous rocks and rockfalls on high-steep slopes, which includes an anchoring and supporting component, a protection net, a signal receiving and feedback component, and a power supply component; the anchoring and supporting component includes multiple columns arranged at intervals on the high-steep slope, the columns are arranged obliquely 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 power supply component is used to charge the signal receiving and feedback component, and the power supply component generates electricity through wind power.

[0004] It can be seen that the existing protection nets are mostly single-line protection nets, and the interception effect on high-steep rockfalls is poor. Summary of the Invention

[0005] The purpose of the present invention is to provide a double-line protection net and its design method to solve the above technical problems.

[0006] To achieve the above purpose, the present invention provides a double-line protection net, which includes an upper protection net and a lower protection net for intercepting rockfalls from the same source area. The upper protection net and the lower protection net are arranged in sequence from top to bottom along the slope, and the distance between the upper protection net and the lower protection net is greater than the designed deformation amount of the upper protection net when it is impacted, and the distance between the lower protection net and the protected object is greater than the elongation amount of the lower protection net; The maximum heights of the upper protection net and the lower protection net satisfy the following conditions: ; ; In the formula, represents the maximum height of the upper protection net; represents the designed height of the upper protection net; represents the impact rockfall Safety factor related to the trajectory height, and , represents the diameter of the impact falling rock ; represents the velocity of the impact falling rock at time; represents the mass of the impact falling rock ; is the acceleration due to gravity, represents the slope angle; represents the safety margin; represents the maximum height of the lower protective net; represents the designed height of the lower protective net.

[0007] A design method for a double-line protective net, comprising the following steps: S1. Perform an initial trajectory analysis, and based on the results of the initial trajectory analysis, determine whether to install a double-line protective net. When it is determined to install a double-line protective net, perform step S2; S2. Upward line design and analysis: Set an upper protective net with a height of on the slope, and perform a trajectory analysis once. Based on the results of the once trajectory analysis, determine the impact falling rocks intercepted by the upper protective net , the impact falling rocks not intercepted by the upper protective net , and the impact falling rocks blocked but not intercepted by the upper protective net ; S3. Downward line design: Based on the proportion of the impact falling rocks blocked but not intercepted by the upper protective net in the number of impact falling rocks reaching the upper protective net, and the proportion of the impact falling rocks not intercepted by the upper protective net in the number of impact falling rocks reaching the upper protective net, determine the applied trajectory analysis method, and in combination with the maximum interception height of the lower protective net, determine the minimum energy absorption capacity and the designed height required for the lower protective net.

[0008] Preferably, in step S1, based on the initial trajectory analysis, determine whether a single protective net can meet the safety formula. If it meets, set a single protective net; otherwise, set a double-line protective net; It specifically includes the following steps: S11. Based on the images collected by UAV aerial photography, identify potential falling rocks on the slope; Use UAV aerial photography to collect images. After preprocessing, splice the collected images to form a slope image, then extract the edge and surface features of the slope, and then based on feature point matching and the principle of stereo vision, convert the two-dimensional image into a three-dimensional model, obtain the elevation information of the slope surface, and calculate the slope value of each rock on the slope based on the three-dimensional model. Then compare the slope value of each rock with the set threshold, and regard the rocks with slope values greater than the set threshold as potential falling rocks; S12. Evaluate the probability of potential rockfall release, and regard the potential rockfalls with a release probability greater than the set threshold as impact rockfalls. The expression for the probability of potential rockfall release is as follows: ; In the formula, respectively represent the seismic factor, rainfall factor, and weathering factor that trigger the release of potential rockfalls; S13. Based on the three-dimensional model, obtain the initial trajectory and kinetic energy of the impact rockfall: ; ; ; ; In the formula, represents the position of the impact rockfall at time; represents the source area position of the impact rockfall obtained from the three-dimensional model; represents the acceleration of the impact rockfall in the direction component; represents the kinetic energy of the impact rockfall at the position ; represents the density of the impact rockfall represents the impact rockfall ; Among them, ; In the formula, represents the friction coefficient between the impact rockfall and the slope surface; S14. Input the position of the single-wire protection net into the trajectory and kinetic energy formula of the impact rockfall described in step S13 to obtain the kinetic energy and height of the impact rockfall when it reaches the single-wire protection net. Input the kinetic energy and height into the safety formula. The safety formula is as follows: ; In the formula, represents the designed energy absorption capacity of the single-wire protection net; represents the height tolerance of the impact rockfall considering the shape; represents the designed height of the single-wire protection net; S15. When the safety formula described in step S14 is satisfied, set the single-wire protection net; otherwise, set the double-layer protection net.

[0009] Preferably, in step S2, the process of the first trajectory analysis is as follows: An upper protective net with a height of is set on the slope, and the maximum interception speed is calculated based on the designed energy absorption capacity of the upper protective net: ; In the formula, represents the maximum interception speed; represents the designed energy absorption capacity of the upper protective net; represents the impact falling rock 's mass characteristic value; , , respectively represent the safety factors related to the mass, speed of the test impact falling rock and the designed energy absorption capacity of the upper protective net ; The impact falling rocks with a speed less than the maximum interception speed and a height lower than the designed height of the upper protective net are regarded as the impact falling rocks intercepted by the upper protective net ; The impact falling rocks with a speed greater than the maximum interception speed and a height lower than the designed height of the upper protective net are regarded as the impact falling rocks blocked but not intercepted by the upper protective net , and the number of impact falling rocks is , where represents the proportion of the impact falling rocks blocked but not intercepted by the upper protective net in the number of impact falling rocks reaching the upper protective net ; The impact falling rocks with a height higher than the designed height of the upper protective net are regarded as the impact falling rocks not intercepted by the upper protective net , and the number of impact falling rocks is , where represents the proportion of the impact falling rocks not intercepted by the upper protective net in the number of impact falling rocks reaching the upper protective net .

[0010] Preferably, step S3 specifically includes the following steps: S31. Determine the trajectory analysis method: When and , the position where the upper protective net is located is regarded as the source area position for secondary trajectory analysis, where the initial velocity of the impact falling rock has the following expression: ; In the formula, represents the Percentile ; Impact falling rock Initial height The expression is as follows: ; In the formula, When analyzing the height distribution of impact falling rocks reaching the upper protection net considering only the upper protection net, it represents the percentile in the height distribution result, and ; When and Execute the result of the first trajectory analysis or the result of the second trajectory analysis; When and Merge the result of the first trajectory analysis and the result of the second trajectory analysis, and create a subset containing the height and speed of the impact falling rock: ; In the formula, Represents the number of subsets; Represents the number of impact falling rocks reaching the lower protection net; S32. Calculate the minimum energy absorption capacity and design height required for the lower protection net: ; ; In the formula, Represents the design height of the lower protection net; Represents the height eigenvalue of the lower protection net in the first trajectory analysis; Represents the height eigenvalue of the lower protection net in the second trajectory analysis; Represents the energy absorption capacity eigenvalue of the lower protection net in the first trajectory analysis; Represents the energy absorption capacity eigenvalue of the lower protection net in the second trajectory analysis; S33. Evaluate the energy absorption level of the lower protection net: Calculate the ratio of the impact falling rocks intercepted and stopped by the lower protection net to the impact falling rocks reaching the position of the lower protection net : ; In the formula, Represents the ratio of the impact falling rocks intercepted and stopped by the lower protection net to the impact falling rocks reaching the position of the lower protection net; Represents the falling rocks that are not intercepted by the upper protection net and reach the lower protection net; Indicates the impact falling rocks that are blocked by the upper protective net but not intercepted and reach the lower protective net. When performing secondary trajectory analysis, ; Indicates the proportion of the number of impact falling rocks intercepted by the double-layer protective net in the total number of impact falling rocks; Indicates the number of impact falling rocks not intercepted by the lower protective net; When and and or , it is simplified to: ; Take the percentile value of the velocity distribution in the trajectory of the intercepted impact falling rocks as , and use to evaluate the energy absorption level of the lower protective net.

[0011] Therefore, the present invention adopts the above-mentioned double-layer protective net and its design method, and the beneficial effects are as follows: 1. Double protection of the upper protective net and the lower protective net: By setting the upper and lower protective nets, a multi-level safety barrier is formed. The upper protective net first intercepts most of the impact falling rocks, reducing the pressure on the lower protective net, ensuring that even if some falling rocks are not completely intercepted, they can be effectively processed in the second line of defense. The two-level design greatly improves the reliability and safety of the protection system; 2. Dynamic adjustment based on the trajectory analysis results: This method not only relies on static design parameters but also combines dynamic trajectory analysis. By performing initial trajectory analysis and subsequent multiple analyses, the movement path of the falling rocks and their impact on the protective net can be evaluated in real time, thereby optimizing the height and energy absorption capacity of the protective net, enabling the protection system to better adapt to the actual needs under different environmental conditions; 3. Efficient resource utilization: By accurately calculating the proportion intercepted by the upper protective net and the number of non-intercepted falling rocks, as well as the required energy absorption capacity and design height of the lower protective net, it is ensured that each layer of the protective net can exert its maximum efficiency under the most suitable conditions, which not only improves the protection effect but also reduces unnecessary material waste and construction costs; 4. Flexible response to different terrains and falling rock conditions: This method can be adjusted according to different terrain features (such as slope angles) and falling rock characteristics; for example, the specific setting of the slope is considered when determining the height of the upper protective net, and the actual interception effect of the upper protective net is combined when determining the design parameters of the lower protective net, enabling this design scheme to be widely applicable to various complex natural environments; 5. Comprehensive coverage of potential risk points: By implementing protective measures step by step, with clear goals and inspection criteria for each step, ensure that the entire protection system can achieve optimal safety from design to construction and then to final operation. Especially for key facilities located in mountainous areas or regions prone to geological disasters such as landslides, such a protection system is particularly important.

[0012] In summary, for the double - line protection net and its design method described in the present invention, through scientific and reasonable structural layout and the application of technical means, not only the protection performance is improved, but also the effective utilization of resources and the maximization of environmental adaptability are achieved.

[0013] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Brief Description of the Drawings

[0014] Figure 1 It is a structural schematic diagram of a double - line protection net of the present invention.

[0015] Reference Signs 1. Upper protection net; 2. Lower protection net. Detailed Embodiments

[0016] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clearly understood, the following further elaborates on the embodiments of the present invention with reference to the 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 used to limit the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end.

[0017] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non - exclusive inclusion. For example, a process, method, system, product or server that includes a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0018] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0019] As Figure 1As shown in the figure, 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 amount of the upper protection net 1 when it is impacted. The distance between the lower protection net 2 and the protected object is greater than the elongation amount of the lower protection net 2; The maximum heights of the upper protection net 1 and the lower protection net 2 satisfy the following conditions: ; ; In the formula, represents the maximum height of the upper protection net; represents the designed height of the upper protection net; represents the safety factor related to the trajectory height of the impacting falling rock, and , , represents the diameter of the impacting falling rock , represents the velocity of the impacting falling rock at time, represents the mass of the impacting falling rock , is the acceleration due to gravity, represents the slope angle; represents the safety margin; represents the maximum height of the lower protection net; represents the designed height of the lower protection net.

[0020] A design method for a double-line protection net includes the following steps: S1. Perform an initial trajectory analysis, and based on the results of the initial trajectory analysis, determine whether to install a double-line protection net. When it is determined to install a double-line protection net, perform step S2; In step S1, based on the initial trajectory analysis, determine whether a single protection net can meet the safety formula. If it meets, set a single protection net; otherwise, set a double-line protection net; Specifically, it includes the following steps: S11. Based on the images collected by UAV aerial photography, identify potential falling rocks on the slope; Use a drone to capture images by aerial photography (at this time, a double-line protection net is not installed on the slope). After preprocessing, the captured images are stitched to form a slope image. Then, extract the edge and surface features of the slope. Next, based on feature point matching and the principle of stereo vision, convert the two-dimensional image into a three-dimensional model, obtain the elevation information of the slope surface, and calculate the slope value of each rock on the slope based on the three-dimensional model. Then, compare the slope value of each rock with the set threshold. In this embodiment, the set threshold is 60°. Consider the rocks with slope values greater than the set threshold as potential falling rocks; S12. Evaluate the probability of release of potential falling rocks, and consider the potential falling rocks with a release probability greater than the set threshold as impact falling rocks. The expression for the probability of release of potential falling rocks is as follows: ; In the formula, respectively represent the seismic factor, rainfall factor, and weathering factor that trigger the release of potential falling rocks; S13. Based on the three-dimensional model, obtain the initial trajectory and kinetic energy of the impact falling rock: ; ; ; ; In the formula, represents the position of the impact falling rock at time; represents the source area position of the impact falling rock obtained from the three-dimensional model; represents the acceleration of the impact falling rock at in the direction of the component; represents the kinetic energy of the impact falling rock at the position ; represents the density of the impact falling rock ; Among them, ; In the formula, represents the friction coefficient between the impact falling rock and the slope surface; S14. Input the position of the single-line protection net into the trajectory and kinetic energy formula of the impact falling rock described in step S13 to obtain the kinetic energy of the impact falling rock when it reaches the single-line protection net and the height . Input the kinetic energy and the height ​ ; In the formula, represents the designed energy absorption capacity of the single-layer protection net; represents the tolerance of the impact falling rock height considering the shape; represents the designed height of the single-layer protection net; S15. When the safety formula described in step S14 is satisfied, set the single-layer protection net; otherwise, set the double-layer protection net.

[0021] S2. Upward line design and analysis: Set the upper protection net with a height of on the slope and perform a trajectory analysis once. Based on the results of the first trajectory analysis, determine the impact falling rocks intercepted by the upper protection net , the impact falling rocks not intercepted by the upper protection net , and the impact falling rocks blocked but not intercepted by the upper protection net ; In step S2, the process of the first trajectory analysis is as follows: Set the upper protection net with a height of on the slope and calculate the maximum interception speed based on the designed energy absorption capacity of the upper protection net: ; In the formula, represents the maximum interception speed; represents the designed energy absorption capacity of the upper protection net; represents the impact falling rock 's mass characteristic value; , , respectively represent the safety factors related to the mass, speed of the test impact falling rock and the designed energy absorption capacity of the upper protection net ; Regard the impact falling rocks with a speed less than the maximum interception speed and a height lower than the designed height of the upper protection net as the impact falling rocks intercepted by the upper protection net ; Regard the impact falling rocks with a speed greater than the maximum interception speed and a height lower than the designed height of the upper protection net as the impact falling rocks blocked but not intercepted by the upper protection net , and the number of impact falling rocks is , where represents the proportion of the impact falling rocks blocked but not intercepted by the upper protection net in the number of impact falling rocks reaching the upper protection net ; Regard the impact falling rocks with a height higher than the designed height of the upper protection net as the impact falling rocks not intercepted by the upper protection net , and the number of impact falling rocks is , where represents the proportion of the impact falling rocks not intercepted by the upper protection net in the number of impact falling rocks reaching the upper protection net .

[0022] S3. Downlink line design: Based on the proportion of the impact falling rocks blocked but not intercepted by the upper protection net in the number of impact falling rocks reaching the upper protection net, and the proportion of the impact falling rocks not intercepted by the upper protection net in the number of impact falling rocks reaching the upper protection net, determine the applied trajectory analysis method, and combine it with 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.

[0023] Step S3 specifically includes the following steps: S31. Determine the trajectory analysis method: When and , consider the position of the upper protection net as the source area position for secondary trajectory analysis, where the initial velocity of the impact falling rock has the following expression: ; In the formula, represents the th percentile in the energy distribution result when analyzing the energy distribution of the impact falling rocks reaching the upper protection net only considering the upper protection net, ; The initial height of the impact falling rock has the following expression: ; In the formula, represents the th percentile in the height distribution result when analyzing the height distribution of the impact falling rocks reaching the upper protection net only considering the upper protection net, and ; When and , execute the result of the first trajectory analysis or the second trajectory analysis; When and , combine the results of the first trajectory analysis and the second trajectory analysis, and create a subset containing the height and velocity of the impact falling rocks: ; In the formula, represents the number of subsets; represents the number of impact falling rocks reaching the lower protection net; S32. Calculate the minimum energy absorption capacity and design height required for the lower protection net: ; ; In the formula, represents the designed height of the lower protective net; represents the height eigenvalue of the lower protective net in the first trajectory analysis; represents the height eigenvalue of the lower protective net in the second trajectory analysis; represents the energy absorption capacity eigenvalue of the lower protective net in the first trajectory analysis; represents the energy absorption capacity eigenvalue of the lower protective net in the second trajectory analysis; S33. Evaluate the energy absorption level of the lower protective net: Calculate the ratio of the impact falling rocks intercepted and stopped by the lower protective net to the impact falling rocks reaching the position of the lower protective net : ; In the formula, represents the ratio of the impact falling rocks intercepted and stopped by the lower protective net to the impact falling rocks reaching the position of the lower protective net; represents the falling rocks that are not intercepted by the upper protective net and reach the lower protective net; represents the impact falling rocks that are blocked by the upper protective net but not intercepted and reach the lower protective net. When performing the second trajectory analysis, ; represents the ratio of the number of impact falling rocks intercepted by the double-layer protective net to the total number of impact falling rocks; represents the number of impact falling rocks not intercepted by the lower protective net; When and and or , it is simplified to get: ; Take the percentile value of the velocity distribution in the trajectory of the intercepted impact falling rocks as , and use to evaluate the energy absorption level of the lower protective net.

[0024] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A double-line protection net, characterized in that: It includes an upper protection net and a lower protection net for intercepting falling rocks from the same source area. The upper protection net and the lower protection net are arranged in sequence from top to bottom along the 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 it is impacted, 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 meet the following conditions: ； ； In the formula, 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 protection net, characterized in that: The following steps are involved: S1, perform initial trajectory analysis, and determine whether to install a double-line protection net according to claim 1 based on the initial trajectory analysis result, and when it is determined to install the double-line protection net, execute step S2; S2. Upward line design and analysis: Set the height of the slope to The upper protection net is used to perform a trajectory analysis, and the impact rockfall intercepted by the upper protection net is determined based on the trajectory analysis results. , impact rockfall not intercepted by the upper protective net , impact rockfall that was blocked but not intercepted by the upper protective net ; S3. Downlink line design: Based on the ratio of rockfall blocked by the upper protection net but not intercepted to the number of rockfalls reaching the upper protection net, and the ratio of rockfalls not intercepted by the upper protection net to the number of rockfalls reaching the upper protection net, determine the trajectory analysis method to be applied, and determine the minimum energy absorption capacity and design height required for the lower protection net in combination with the maximum interception height of the lower protection net.

3. A method for designing a double-wire protection net as described in claim 2, characterized in that: In step S1, based on the initial trajectory analysis, determine whether the single protection net can meet the safety formula. If so, set the single protection net, otherwise set the double-line protection net; It specifically includes the following steps: S11. Identify potential rockfalls on slopes based on images collected by drones; Use drones to capture images, stitch the images together after preprocessing to form a slope image, extract the edge and surface features of the slope, and then convert the two-dimensional image into a three-dimensional model based on feature point matching and stereo vision principles to obtain the elevation information of the slope surface. Calculate the slope value of each rock on the slope based on the three-dimensional model, and then compare the slope value of each rock with the set threshold. Rocks with slope values ​​greater than the set threshold are considered potential rockfalls. S12. Evaluate the probability of potential rockfall release, and regard potential rockfalls with a release probability greater than a set threshold as impact rockfalls. The probability expression of potential rockfall release is as follows: ； In the formula, They represent the earthquake factor, rainfall factor, and weathering factor that trigger the potential rockfall release; S13. Based on the three-dimensional model, the initial trajectory and kinetic energy of the impact rockfall are obtained: ； ； ； ； In the formula, Indicates impact rockfall exist The location at the moment; Represents the impact rockfall obtained from the 3D model The location of the source region; Indicates impact rockfall Acceleration exist Directional weight; Indicates impact rockfall In Location Kinetic energy at Indicates impact rockfall density; in, ； In the formula, 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, and 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: ； In the formula, Indicates the design energy absorption capacity of the single-line protection net; It indicates the height tolerance of the impact rockfall considering the 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 protection net as described in 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 protection net’s designed energy absorption capacity: ； In the formula, 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 energy absorption capacity of the upper protection net design The associated safety factor; The impact rockfall with a speed lower than the maximum interception speed and a height lower than the design height of the upper protection net is regarded as the impact rockfall intercepted by the upper protection net. ; The impact rockfall with a speed greater than the maximum interception speed and a height lower than the design height of the upper protection net is regarded as the impact rockfall blocked but not intercepted by the upper protection net. , and the number of impact rocks is ,in, The number of rockfalls that were blocked by the upper protection net but not intercepted accounts for the number of rockfalls that reached the upper protection net. proportion; The impact rockfall with a height higher than the design height of the upper protection net is regarded as the impact rockfall 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 number of rockfall that reaches the upper protection net. proportion.

5. A method for designing a double-wire protection net as claimed in 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 location of the source area is considered as the secondary trajectory analysis, in which the impact rockfall Initial velocity The expression is as follows: ； In the formula, 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 energy distribution result is percentile, ; Impact rockfall Initial height The expression is as follows: ； In the formula, 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 , the first trajectory analysis result or the second trajectory analysis result is executed; when and , merge the results of the primary and secondary trajectory analysis and create a subset containing the impact rockfall height and velocity: ； In the formula, Indicates the number of subsets; Indicates the number of rockfalls that reach the lower protection net; S32. Calculate the minimum energy absorption capacity and design height required for the lower protection net: ； ； In the formula, Indicates the design height of the lower protective net; Represents the height characteristic value of the lower protection net in a trajectory analysis; It represents the height eigenvalue of the lower protection net in the secondary trajectory analysis; It represents the energy absorption capacity characteristic value of the lower protection net in a trajectory analysis; It represents the energy absorption capacity characteristic value of the lower protection 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. : ； In the formula, It indicates the ratio of the impact rockfalls that are intercepted and stopped by the lower protection net to the impact rockfalls that reach 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; It means that the impact rockfall is blocked by the upper protection net but not intercepted and reaches the lower protection net. When performing the secondary trajectory analysis, ; It indicates the ratio of the number of rockfalls intercepted by the double-line protection network to the total number of rockfalls; Indicates the number of rockfalls that are not intercepted by the lower protection net; when and as well as or When , we simplify to get: ； Take the velocity distribution of the intercepted impact rockfall trajectory Percentile values ​​are , and use Evaluate the energy absorption level of the lower protective net.

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