Dangerous rock falling motion trail and multi-stage protective net system simulation method and system

Abstract

The invention relates to a dangerous rock falling motion trail and multistage protective net system simulation method and system, and the method comprises the steps: obtaining slope point cloud data, reconstructing a slope live-action three-dimensional model, and extracting slope elevation points; the elevation points of the slope surface are spread, a three-dimensional slope body model is established, and grids are divided; pFC loading is carried out to obtain an initial slope three-dimensional model; establishing a rockfall particle model, and loading the rockfall particle model to the initial slope three-dimensional model; model parameters are set, a gravity field is applied, and rockfall motion characteristics are obtained; the setting position of the combined protective net is determined and set; starting simulation, observing whether the combined protective net successfully intercepts rockfall or not, and if not, adjusting the setting until success; and optimizing the combined protective net according to the setting when the rockfall is successfully intercepted. According to the method, a curtain type protective net and passive protective net multi-stage energy dissipation combined model is established, the purpose of integrating dangerous rock falling and a protective structure for whole-process three-dimensional simulation is achieved, and a reference basis is provided for selection and design of the protective structure.

Description

Technical Field

[0001] The present invention relates to the field of rockfall protection technology, and in particular to a method and system for simulating the movement trajectory of dangerous rockfalls and a multi-level protection net system. Background Art

[0002] In recent years, with the development of computer technology and numerical simulation methods, numerical simulation has been widely used in the analysis of the movement characteristics and protection of dangerous rockfalls. Numerical simulation can not only simulate processes that cannot be carried out in field tests, but also reduce the cost of the test, accurately reflect the movement characteristics of dangerous rockfalls and the performance of various protection measures, and provide a reference for the selection and design of protective structures.

[0003] At present, many achievements have been made in the analysis of the movement characteristics and protection of dangerous rock falls using numerical simulation methods, but there are still some technical deficiencies: the existing numerical calculation models are still mainly two-dimensional, and there are few analysis models that consider three-dimensional; currently, most of the movement characteristics of dangerous rock falls and the dynamic response of protective structures are analyzed and studied separately, while there are few that integrate the two to simulate the movement characteristics of rock falls and the entire protection process.

[0004] Therefore, it is necessary to propose new measures to overcome the above-mentioned defects. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for simulating the movement trajectory of dangerous rockfall and multi-level protection net system, so as to solve the problem of lack of a three-dimensional simulation method integrating dangerous rockfall and protection structure for the whole process.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for simulating the trajectory of dangerous rockfall and a multi-level protection net system, the method comprising:

[0008] Obtain slope point cloud data;

[0009] Reconstruct the real-scene 3D model of the slope using the slope point cloud data, and extract the slope elevation points from the real-scene 3D model of the slope;

[0010] The elevation points of the slope are displayed, and the three-dimensional slope model is established based on the display results, and the grid is divided;

[0011] Perform PFC loading on the meshed three-dimensional slope model to obtain the initial three-dimensional slope model;

[0012] Establish a rockfall particle model and load it into the initial slope 3D model;

[0013] The model parameters are set in the initial slope 3D model, and the gravity field is applied to obtain the rockfall motion characteristics;

[0014] According to the characteristics of rockfall movement, determine the location of the combined protection net and set it up;

[0015] Start the simulation and observe whether the combined protection net successfully intercepts the falling rocks. If not, adjust the settings until it succeeds;

[0016] The combined protection net is optimized based on the settings when successfully intercepting falling rocks.

[0017] Furthermore, slope point cloud data is obtained, including:

[0018] Arrange measurement control points on site;

[0019] Use drones to shoot images of measurement control points from multiple angles in the air to obtain slope point cloud data.

[0020] Furthermore, model parameters are set in the initial slope 3D model, including:

[0021] Assign values ​​to the number, radius distribution, and density of rockfall particles;

[0022] Set the particle's tangential stiffness, normal stiffness, friction coefficient, cohesion, friction angle, effective modulus, and tensile strength;

[0023] Set the tangential stiffness, normal stiffness, and friction coefficient of the wall.

[0024] Furthermore, the rockfall motion characteristics are obtained, including:

[0025] Monitor the speed, rotational velocity and Z-direction displacement of the falling rock.

[0026] Furthermore, the combined protection net includes a curtain-type protection net and a passive protection net. The curtain-type protection net is arranged in the middle area of ​​the slope, and the passive protection net is arranged in the bottom area of ​​the slope.

[0027] Furthermore, a curtain type protective net is provided, comprising:

[0028] Generate a rectangle in the XY plane, formed by closely arranged ball particles;

[0029] Delete the specified ball particles every set number of particles to form a rectangular network;

[0030] Fixed pillars are arranged on both sides of the rectangular net, and the fixed pillars and the corner points of the rectangular net are connected together to obtain a curtain-type protective net;

[0031] Set the parameters of the curtain protection net, including particle radius, particle density, tensile strength, cohesion, friction coefficient and internal friction angle;

[0032] Set boundary conditions.

[0033] Furthermore, a passive protection net is provided, including:

[0034] Generate a rectangle in the XZ plane, which is formed by the closely packed ball particles;

[0035] Delete the specified ball particles every set number of particles to form a rectangular network;

[0036] Fixed pillars are arranged on both sides of the rectangular net, and the fixed pillars and the corner points of the rectangular net are connected together to obtain a passive protection net;

[0037] Set the passive protection net parameters, including particle radius, particle density, tensile strength, cohesion, friction coefficient and internal friction angle;

[0038] Set boundary conditions.

[0039] Furthermore, boundary conditions are set, including:

[0040] Keep the horizontal speed and rotation speed of the fixed support constant;

[0041] Set the gravity acceleration to -9.8m / s2.

[0042] Further, simulations are started, including:

[0043] The curtain-type protection net is balanced under the stress of its own weight and automatically laid on the slope;

[0044] Passive protection nets are balanced under their own weight;

[0045] Falling rocks fall under the stress of their own weight.

[0046] On the other hand, a system for simulating the trajectory of falling dangerous rocks and a multi-level protection net system is provided, and the system is used to implement the method described, including:

[0047] The reconstruction and extraction module is used to obtain the slope point cloud data, reconstruct the slope real scene three-dimensional model using the slope point cloud data, and extract the slope elevation points in the slope real scene three-dimensional model;

[0048] The model building and division module is used to display the elevation points on the slope surface, use the display results to build a three-dimensional slope model, and divide the grid;

[0049] The PFC loading module is used to perform PFC loading on the gridded three-dimensional slope model to obtain an initial slope three-dimensional model;

[0050] The rockfall model loading module is used to establish a rockfall particle model and load it into the initial slope 3D model;

[0051] The rockfall motion feature acquisition module is used to set model parameters in the initial slope three-dimensional model and apply a gravity field to acquire the rockfall motion features;

[0052] A combined protection net setting module is used to determine the location of the combined protection net and set it according to the characteristics of rockfall movement;

[0053] The simulation module is used to start the simulation and observe whether the combined protection net successfully intercepts the falling rocks. If not, the settings are adjusted until it succeeds;

[0054] Optimization module for optimizing the combined protection net according to the settings when successfully intercepting falling rocks.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] The present invention provides a method and system for simulating the movement trajectory of falling dangerous rocks and a multi-level protective net system, establishes a multi-level energy dissipation combined protective net model of a curtain-type protective net and a passive protective net, and then performs static and dynamic calculations to obtain a more realistic and accurate movement trajectory of falling rocks, thereby achieving the purpose of integrating falling dangerous rocks and protective structures for full-process three-dimensional simulation, and can accurately reflect the performance of the combined protective net, providing a reference basis for the selection and design of the protective structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without paying creative work.

[0058] Figure 1 It is a flow chart of the method of the present invention.

[0059] Figure 2 It is a three-dimensional slope model generated by the present invention.

[0060] Figure 3 It is a spherical rockfall model generated by the present invention.

[0061] Figure 4 It is a curtain type protection net model generated by the present invention.

[0062] Figure 5 It is a calculation schematic diagram of the curtain type protection net of the present invention.

[0063] Figure 6 It is a passive protection net model generated by the present invention.

[0064] Figure 7The present invention is a model of a curtain-type protective net generated by the present invention after being laid on a slope surface.

[0065] Figure 8 This is a schematic diagram of the monitoring point setting of the passive protection network. DETAILED DESCRIPTION

[0066] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0067] It should be noted that similar reference numerals and letters represent similar items, and therefore, once an item is defined in one embodiment, it does not need to be further defined and explained in subsequent embodiments. In addition, the term "comprising" and the like and any variation thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising 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 inherent to these processes, methods, products or devices.

[0068] It should also be noted that although the order of steps is mentioned in the method description, in some cases, they may be performed in an order different from that shown here, and this should not be construed as a limitation on the order of the steps.

[0069] The present invention provides a method for simulating the motion trajectory of dangerous rockfall and a multi-level protection net system based on discrete elements, which can obtain a true and accurate motion trajectory of rockfall, optimize the layout position of the multi-level energy dissipation protection net, and evaluate the protection effect, providing a true and reliable basis for multi-level energy dissipation protection of rockfall in dangerous mountainous areas.

[0070] like Figure 1 , the method comprising:

[0071] S1: Obtain slope point cloud data. Specifically including:

[0072] S101: Arrange measurement control points on site;

[0073] S102: Use a drone to shoot images of measurement control points at multiple angles in the air to obtain slope point cloud data.

[0074] S2: Reconstruct the real-life 3D model of the slope using the slope point cloud data, and extract the slope elevation points from the real-life 3D model of the slope.

[0075] S3: Expand the slope elevation points, use the expansion results to build a three-dimensional slope model, and divide it into grids.

[0076] S4: Perform PFC loading on the gridded three-dimensional slope model to obtain an initial slope three-dimensional model.

[0077] S5: Establish a rockfall particle model and load it into the initial slope 3D model.

[0078] S6: Setting model parameters in the initial slope 3D model and applying a gravity field to obtain rockfall motion characteristics.

[0079] In this step:

[0080] Set model parameters in the initial slope 3D model, including:

[0081] S601: Assign values ​​to the number, radius distribution and density of rockfall particles;

[0082] S602: Set the tangential stiffness, normal stiffness, friction coefficient, cohesion, friction angle, effective modulus and tensile strength of the particles;

[0083] S603: Set the tangential stiffness, normal stiffness and friction coefficient of the wall. The slope surface is modeled using the wall method, that is, setting the parameters of the slope surface.

[0084] Obtain rockfall motion characteristics, including:

[0085] Monitor the speed, rotational velocity and Z-direction displacement of the falling rock.

[0086] S7: Determine the location for setting up the combined protection net and set it up based on the movement characteristics of the falling rocks.

[0087] The combined protection net includes a curtain-type protection net and a passive protection net. The curtain-type protection net is arranged in the middle area of ​​the slope, and the passive protection net is arranged in the bottom area of ​​the slope.

[0088] Set up curtain protection net, including:

[0089] S711: Generate a rectangle in the XY plane, which is formed by closely arranged ball particles;

[0090] S712: Delete the designated ball particles every set number of particles to form a rectangular network;

[0091] S713: Setting fixed pillars on both sides of the rectangular net, and connecting the fixed pillars and the corner points of the rectangular net together to obtain a curtain-type protective net;

[0092] S714: Set the parameters of the curtain protection net, including particle radius, particle density, tensile strength, cohesion, friction coefficient and internal friction angle;

[0093] S715: Setting boundary conditions.

[0094] Set up a passive protection network, including:

[0095] S721: Generate a rectangle in the XZ plane, which is formed by the closely arranged ball particles;

[0096] S722: Delete the designated ball particles every set number of particles to form a rectangular network;

[0097] S723: Setting fixed pillars on both sides of the rectangular net, connecting the fixed pillars and the corner points of the rectangular net together to obtain a passive protection net;

[0098] S724: Set the passive protection net parameters, including particle radius, particle density, tensile strength, cohesion, friction coefficient and internal friction angle;

[0099] S725: Setting boundary conditions.

[0100] The above boundary conditions are set, including:

[0101] S731: Keep the horizontal speed and rotation speed of the fixed support unchanged;

[0102] S732: Set gravity acceleration to -9.8m / s 2 .

[0103] S8: Start simulation. The curtain protection net is balanced under the stress of its own weight and automatically laid on the slope. The passive protection net is balanced under its own weight and the falling rocks fall under the stress of their own weight.

[0104] Observe whether the combined protection net successfully intercepts the falling rocks. If not, adjust the settings until it succeeds.

[0105] S9: Optimize the combined protection net according to the settings when successfully intercepting falling rocks.

[0106] The method of the present invention fully considers factors such as the geometric characteristics of the slope, the shape of the falling rocks, the trajectory of the falling rocks, the curtain-type protection net combined with the passive protection net and the multi-level energy dissipation combination protection net when modeling, and realizes the simulation of the whole process from the falling rocks to the multi-level energy dissipation protection system taking effect and finally the falling rocks being successfully intercepted.

[0107] The present invention adopts a three-dimensional numerical simulation method of a multi-level protection net system, which is different from the simulation method of the prior art that only adopts a two-dimensional model or a single protection structure. The present invention combines a multi-level energy dissipation combination of a curtain-type protection net and a passive protection net in the simulation process, which can more realistically reproduce the movement trajectory of dangerous rockfalls and provide a basis for optimizing the layout of the protection structure. Through the introduction of a multi-level protection net system, the present invention can more effectively reduce the energy and speed of falling rocks, especially when the falling rocks pass through the first layer of curtain-type protection nets, their kinetic energy is greatly reduced, creating favorable conditions for the final passive protection net interception. This method solves the problem that the prior art cannot simultaneously consider the comprehensive effects of multi-level protection structures, and provides a more accurate and comprehensive protection design solution.

[0108] Example:

[0109] The following is the actual process of simulating the trajectory of dangerous rockfall and the multi-level protection net system using the method of the present invention:

[0110] Step 1: Obtain slope point cloud data.

[0111] First, survey control points are set up on site. By setting up field image control points, i.e. survey control points, the 1:500 aerial survey mapping accuracy is met, providing image control data for internal data processing. The interval between each point is about 200 meters, and about 30 image control points are set up in the survey area. The real three-dimensional coordinate information of the field image control points is obtained through measurement, providing an accuracy basis for internal data processing and modeling.

[0112] Then use the drone to shoot the images of the on-site measurement control points from multiple angles in the air to obtain the slope point cloud data in .OSGB format. Determine the weather conditions on the day of the operation, including light, visibility and wind speed, and conduct aerial photography flights in strict accordance with the technical design requirements. A total of 20 routes are laid out in the entire survey area, which are completed in five flights. Three flights are at the station take-off and landing point, and two flights are at the top of the mountain. Each flight takes about 30 minutes. The image resolution is 2-3cm, which meets the requirement of better than 3cm. A total of 10,528 images were obtained during the entire flight, with clear images, rich layers, moderate contrast and soft tones. Small ground features that are compatible with the ground resolution can be identified; clear three-dimensional models can be established. There are no defects such as clouds, cloud shadows, smoke, large-area reflections, and stains on the images.

[0113] Step 2: Import the slope point cloud data into EPS software to reconstruct the real-life 3D model of the slope and extract the slope elevation points.

[0114] Step 3: Import the slope elevation points into CAD for point development, and then import the data into Rhino to build a 3D slope model and divide the mesh. In Rhino, the mesh accuracy is controlled by controlling the size of surface U spans and surface V spans, and the generated 3D slope model is saved as a .stl file.

[0115] Step 4: Load the 3D slope model through PFC to obtain the initial slope 3D model, such as Figure 2 As shown. Figure 2 It can be seen that the obtained three-dimensional slope model can realistically and effectively reproduce the actual slope shape.

[0116] Step 5: According to the rockfall situation on site, such as rockfall size and shape, etc., build the corresponding rockfall particle model based on ZBrush 3D modeling software, and export it to .stl format file. Then load the rockfall particle model into PFC as geometry, and use particle filling to form the final rockfall clump unit. A specific rockfall generation implementation example is Figure 3 As shown, in this embodiment, the generated rockfall shape is spherical, and the rockfall radius varies from 0 to 1 m. In specific applications, the shape of the rockfall can be adjusted according to the on-site survey, such as generating a sheet-shaped or cylindrical rockfall model in ZBrush software.

[0117] Step 6: Set the model parameters and apply the gravity field to calculate the motion characteristics of the falling rocks, and monitor the trajectory, translation and rotation speed, bounce height, etc. of all the falling rocks. Among them, it is worth noting that the selection of the collision recovery coefficient in the parameters directly affects the motion characteristics of the falling rocks. In order to select the appropriate collision recovery coefficient, parameter calibration is required.

[0118] Step 7: According to the characteristics of rockfall, the location of the combined protection net is preliminarily selected. The combined protection net is composed of a curtain protection net and a passive protection net. The main function of the curtain protection net is to slow down the movement speed and bounce height of the rockfall, so that the energy of the rockfall when it reaches the bottom of the slope is greatly reduced. The passive protection net is laid at the bottom of the slope to resist the rockfall after energy dissipation. The size of the combined protection net is determined according to the rockfall trajectory, maximum lateral offset distance and maximum bounce height in step 6.

[0119] The core of step 7 is to establish a curtain-type protection net and a passive protection net based on Fish language programming. The specific idea of ​​establishing a curtain-type protection net in the slope is to first generate a rectangular net in the XY plane through Fish loop, which is formed by the ball particles tightly together. Then, based on Fish language, the specified ball particles are deleted every certain number of particles, so that the deleted model forms a mesh.

[0120] Set fixed pillars on both sides of the protective net to connect the pillars and the corner points of the net together. Figure 4 As shown. The bonding parameters between the protective net particles are set. The particles adopt a parallel bonding model, the particle radius is 2.5 cm, and the particle density is 2000 kg / cm 3 , tensile strength is 600MPa, cohesion is 300MPa, friction coefficient is 0.5, and internal friction angle is 45°.

[0121] When setting the bottom passive protection net, unlike the curtain type protection net, the bottom passive protection net is directly generated in the XZ plane. Fixed pillars are also required on both sides of the net. The protection net parameters are the same as those in step 7. The passive protection net diagram is as follows Figure 5 shown.

[0122] Add boundary conditions to fix the horizontal speed and rotation speed of the support ball during the calculation process. Set the gravity acceleration to -9.8m / s 2 The curtain-type protective net is balanced under the stress of its own weight and automatically laid on the slope surface. Figure 6 As shown in the figure, the passive protection net is also balanced under its own weight, and then the rock clump falls under the stress of its own weight.

[0123] Step 8: Based on the numerical calculation results, observe whether the combined protection net can successfully intercept the falling rocks. If it cannot, the size and calculation parameters need to be corrected until the falling rocks are successfully intercepted. Figure 7 shown.

[0124] Step 9: Based on the calculation results, further optimize the location and size parameters of the combined protective net, further guide the layout of the on-site protective net, and improve economic benefits.

[0125] The present invention also provides a simulation system for the trajectory of dangerous rockfall and multi-level protection net system, which is used to implement the above method, specifically comprising:

[0126] The reconstruction and extraction module is used to obtain the slope point cloud data, reconstruct the slope real scene three-dimensional model using the slope point cloud data, and extract the slope elevation points in the slope real scene three-dimensional model, which corresponds to S2 of the above method;

[0127] The model building and division module is used to display the elevation points on the slope surface, use the display results to build a three-dimensional slope model, and divide the grid, which corresponds to S3 of the above method;

[0128] A PFC loading module is used to perform PFC loading on the gridded three-dimensional slope model to obtain an initial three-dimensional slope model, corresponding to S4 of the above method;

[0129] A rockfall model loading module is used to establish a rockfall particle model and load it into the initial slope three-dimensional model, corresponding to S5 of the above method;

[0130] A rockfall motion feature acquisition module, used to set model parameters in the initial slope three-dimensional model and apply a gravity field to acquire rockfall motion features, corresponding to S6 of the above method;

[0131] A combined protection net setting module is used to determine the combined protection net setting position and set it according to the rockfall movement characteristics, corresponding to S7 of the above method;

[0132] A simulation module is used to start the simulation and observe whether the combined protection net successfully intercepts the rockfall. If unsuccessful, the settings are adjusted until it succeeds, corresponding to S8 of the above method;

[0133] The optimization module is used to optimize the combined protection net according to the settings when the rockfall is successfully intercepted, corresponding to S9 of the above method.

[0134] Those skilled in the art will appreciate that all or part of the functions of the embodiments of the present invention may be implemented by hardware or by computer programs. When all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program may be stored in a computer-readable storage medium, and the storage medium may include: a read-only memory, a random access memory, a disk, an optical disk, a hard disk, etc., and the program is executed by a computer to implement the above-mentioned functions. For example, the program is stored in the memory of the device, and when the program in the memory is executed by the processor, all or part of the above-mentioned functions can be implemented. In addition, when all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program may also be stored in a storage medium such as a server, another computer, a disk, an optical disk, a flash disk or a mobile hard disk, and is downloaded or copied and saved in the memory of the local device, or the system of the local device is updated, and when the program in the memory is executed by the processor, all or part of the functions in the above-mentioned embodiments can be implemented.

[0135] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A method for simulating the trajectory of dangerous rockfall and a multi-level protection net system, characterized in that: The method comprises: Obtain slope point cloud data; Reconstruct the real-scene 3D model of the slope using the slope point cloud data, and extract the slope elevation points from the real-scene 3D model of the slope; The elevation points of the slope are displayed, and the three-dimensional slope model is established based on the display results, and the grid is divided; Perform PFC loading on the meshed three-dimensional slope model to obtain the initial three-dimensional slope model; Establish a rockfall particle model and load it into the initial slope 3D model; The model parameters are set in the initial slope 3D model, and the gravity field is applied to obtain the rockfall motion characteristics; According to the characteristics of rockfall movement, determine the location of the combined protection net and set it up; Start the simulation and observe whether the combined protection net successfully intercepts the falling rocks. If not, adjust the settings until it succeeds; The combined protection net is optimized based on the settings when successfully intercepting falling rocks.

2. The method for simulating the movement trajectory of dangerous rockfall and multi-level protection net system according to claim 1, characterized in that: Obtain slope point cloud data, including: Arrange measurement control points on site; Use drones to shoot images of measurement control points from multiple angles in the air to obtain slope point cloud data.

3. The method for simulating the movement trajectory of dangerous rockfall and multi-level protection net system according to claim 2, characterized in that: Set model parameters in the initial slope 3D model, including: Assign values ​​to the number, radius distribution, and density of rockfall particles; Set the particle's tangential stiffness, normal stiffness, friction coefficient, cohesion, friction angle, effective modulus, and tensile strength; Set the tangential stiffness, normal stiffness, and friction coefficient of the wall.

4. The method for simulating the movement trajectory of dangerous rockfall and multi-level protection net system according to claim 3 is characterized by: Obtain rockfall motion characteristics, including: Monitor the speed, rotational velocity and Z-direction displacement of the falling rock.

5. The method for simulating the movement trajectory of dangerous rockfall and multi-level protection net system according to claim 4, characterized in that: The combined protection net includes a curtain-type protection net and a passive protection net. The curtain-type protection net is arranged in the middle area of ​​the slope, and the passive protection net is arranged in the bottom area of ​​the slope.

6. The method for simulating the movement trajectory of dangerous rockfall and multi-level protection net system according to claim 5, characterized in that: Set up curtain protection net, including: Generate a rectangle in the XY plane, formed by closely arranged ball particles; Delete the specified ball particles every set number of particles to form a rectangular network; Fixed pillars are arranged on both sides of the rectangular net, and the fixed pillars and the corner points of the rectangular net are connected together to obtain a curtain-type protective net; Set the parameters of the curtain protection net, including particle radius, particle density, tensile strength, cohesion, friction coefficient and internal friction angle; Set boundary conditions.

7. The method for simulating the movement trajectory of dangerous rockfall and multi-level protection net system according to claim 6, characterized in that: Set up passive protection nets, including: Generate a rectangle in the XZ plane, which is formed by the closely packed ball particles; Delete the specified ball particles every set number of particles to form a rectangular network; Fixed pillars are arranged on both sides of the rectangular net, and the fixed pillars and the corner points of the rectangular net are connected together to obtain a passive protection net; Set the passive protection net parameters, including particle radius, particle density, tensile strength, cohesion, friction coefficient and internal friction angle; Set boundary conditions.

8. The method for simulating the movement trajectory of dangerous rockfall and multi-level protection net system according to claim 6 or 7, characterized in that: Set boundary conditions, including: Keep the horizontal speed and rotation speed of the fixed support constant; Set gravity acceleration to -9.8m / s 2 .

9. The method for simulating the movement trajectory of dangerous rockfall and multi-level protection net system according to claim 8, characterized in that: Start the simulation, including: The curtain-type protection net is balanced under the stress of its own weight and automatically laid on the slope; Passive protection nets are balanced under their own weight; The falling rocks fall under the stress of their own weight.

10. The simulation system of the movement trajectory of dangerous rockfall and multi-level protection net system is characterized by: The system is used to implement the method of claim 9, comprising: The reconstruction and extraction module is used to obtain the slope point cloud data, reconstruct the slope real scene three-dimensional model using the slope point cloud data, and extract the slope elevation points in the slope real scene three-dimensional model; The model building and division module is used to display the elevation points on the slope surface, use the display results to build a three-dimensional slope model, and divide the grid; The PFC loading module is used to perform PFC loading on the gridded three-dimensional slope model to obtain an initial slope three-dimensional model; The rockfall model loading module is used to establish a rockfall particle model and load it into the initial slope 3D model; The rockfall motion feature acquisition module is used to set model parameters in the initial slope three-dimensional model and apply a gravity field to acquire the rockfall motion features; A combined protection net setting module is used to determine the location of the combined protection net and set it according to the characteristics of rockfall movement; The simulation module is used to start the simulation and observe whether the combined protection net successfully intercepts the falling rocks. If not, the settings are adjusted until it succeeds; Optimization module for optimizing the combined protection net according to the settings when successfully intercepting falling rocks.

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