Double-layer composite protective net and optimization method thereof

Abstract

The invention discloses a double-layer composite protective net and an optimization method thereof, and belongs to the field of protective nets for rockfall impact, the double-layer composite protective net comprises a supporting pile and double-layer protective net structures fixed on the two sides of the supporting pile, and each double-layer protective net structure comprises an inner side protective net facing the rockfall impact side and an outer side protective net deviating from the rockfall impact side; wherein the inner side protective net is an annular net formed by weaving steel strands, the outer layer protective net is a square net composed of transverse NPR steel strands and longitudinal NPR steel strands, the aperture of the square net is smaller than that of the annular net, and the strength of the annular net is higher than that of the square net; the two ends of the inner side protective net and the two ends of the outer layer protective net are fixed to the side slope through the opposite-pulling plates and the ground anchors in sequence, and the supporting piles are fixed to the ground through the pre-stressed anchor cables. By the adoption of the double-layer composite protective net and the optimization method thereof, the double-layer protective net structure is adopted, huge stones can be intercepted, meanwhile, broken stones can be intercepted, and the protection safety level is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of protective nets for rockfall impact, and particularly to a double-layer composite protective net and an optimization method thereof. Background Art

[0002] Rockfall refers to a dynamic evolution process in which dangerous rock masses or boulders on a slope suddenly collapse downward after exceeding the critical balance point, and roll downward along the slope through one or several combinations of rolling, collision, rebound, jumping or sliding movement modes until they fall onto flat ground, rivers, reservoirs or obstacles and stop moving. When there are human activity areas such as residential areas and construction sites below the rockfall, it may cause huge casualties and property losses. The passive protective net can form a surface protection for the protected area, thereby preventing the falling of collapsed rock masses and soils, and reducing the impact of rockfall on the protected area to a certain extent. Therefore, protective measures need to be set up in actual engineering to intercept rockfall.

[0003] The existing protective net structure is as follows: CN202410130285.4 discloses a high-position and high-steep rockfall protection structure applicable to a rockfall impact energy level of 8000 KJ, which includes a protective net arranged on one side of the mountain tunnel entrance and exit or on the mountain slope side. The protective net is fixed to the ground by multiple support columns; the protective net is a grid structure composed of multiple bundles of transverse NPR steel strands and multiple bundles of longitudinal NPR steel strands that intersect vertically and horizontally. The two ends of the transverse NPR steel strands pass through the outermost support columns and continue to extend, and the extended parts are anchored to the mountain slope or the ground after applying prestress.

[0004] It can be seen that the existing protective net is a single-layer structure, which can only intercept large boulders and has a poor interception effect on crushed stones. Summary of the Invention

[0005] The purpose of the present invention is to provide a double-layer composite protective net and an optimization method thereof to solve the above technical problems.

[0006] To achieve the above purpose, the present invention provides a double-layer composite protective net, including support piles and a double-layer protective net structure fixed on both sides of the support piles. The double-layer protective net structure includes an inner protective net arranged facing the rockfall impact side and an outer protective net facing away from the rockfall impact side. The inner protective net is an annular net woven by steel strands, and the outer protective net is a square grid composed of transverse NPR steel strands and longitudinal NPR steel strands. The aperture of the square grid is smaller than that of the annular net, and the strength of the annular net is higher than that of the square grid; Both ends of the inner protective net and the outer protective net are fixed to the slope through tension plates and ground anchors in sequence, and the support piles are fixed to the ground through prestressed anchor cables.

[0007] Preferably, a plurality of spring buffer members are provided between the outer protective net and the inner protective net.

[0008] An optimization method for a double-layer composite protective net includes the following steps: S1. Based on a double-layer composite protective net and a polyhedron rockfall model, construct an obstacle model under rockfall impact conditions; S2. Dynamically analyze the constructed obstacle model through numerical simulation software, and evaluate the performance of the double-layer composite protective net under different rockfall speeds, rockfall masses, and impact angles; S3. Parameter adjustment: Adjust the sizes of the outer protective net and the inner protective net, the distance between the outer protective net and the inner protective net, the number and position distribution of the spring buffer members respectively, and re-enter the adjusted parameters into step S2 for simulation. Compare the performance after each adjustment to determine the optimal parameter combination; S4. Based on the optimal parameter combination, produce experimental samples and conduct actual tests under laboratory conditions to verify whether their protective efficacy reaches the expected goal. If the expected indicators are met, output the final solution; otherwise, return to step S3; S5. Construct according to the final solution.

[0009] Preferably, step S1 specifically includes the following steps: S11. Determine the geometric parameters of the double-layer composite protective net: Set the aperture of the inner protective net as , and the strength as ; and set the aperture of the outer protective net as , and the strength as ; where , ; At the same time, set the cross-sectional area of the support pile as , and the distance between the outer protective net and the inner protective net as ; Set the number of spring buffer members as , and the elastic coefficient as ; S12. Establish a polyhedron rockfall model: Determine the coordinates of each vertex of the rockfall. In the geometric modeling software, draw each face of the polyhedron according to the determined vertex coordinates to obtain the polyhedron model, and then import the polyhedron model into the physical simulation software. Set the material properties of the rockfall, the mass of the rockfall as , the initial velocity and the impact angle as , S13. Construct the mechanical model of the double-layer composite protective net: Regard both the inner protective net and the outer protective net as flexible structures, and establish the total stiffness calculation formula of the double-layer composite protective net: ; ; ; ; ; ; In the formula, represents the total stiffness of the double-layer composite protection net; represents the stiffness of the outer protection net; represents the stiffness of the inner protection net; represents the stiffness of the spring buffer; represents the number of steel strands of the inner protection net; represents the elastic modulus of the steel strand; represents the cross-sectional area of the steel strand; represents the length of the steel strand; and respectively represent the stiffness of the transverse NPR steel strand and the longitudinal NPR steel strand; and respectively represent the number of the transverse NPR steel strand and the longitudinal NPR steel strand; and respectively represent the elastic modulus of the transverse NPR steel strand and the longitudinal NPR steel strand; and respectively represent the cross-sectional area of the transverse NPR steel strand and the longitudinal NPR steel strand; and respectively represent the length of the transverse NPR steel strand and the longitudinal NPR steel strand; represents the number of spring buffers; represents the elastic coefficient of the spring buffer; S14. Set the contact conditions between the falling rock and the double-layer composite protection net to obtain the contact model; S15. Simulate the contact force between the falling rock and the double-layer composite protection net, and calculate the normal force and the tangential force at each time step according to the contact conditions: ; ; In the formula, and respectively represent the spring constants in the normal and tangential directions; and respectively represent the displacement amounts in the normal and tangential directions; and respectively represent the velocity components in the normal and tangential directions; and represent the normal viscous damping coefficient and the tangential viscous damping coefficient respectively; S16. Optimize the contact conditions described in step S14 using the simulation results of step S15, loop through steps S14 and S15 until the end condition is met, and output the obstruction model.

[0010] Preferably, in step S14, the rockfall is regarded as a rigid body, and the double-layer composite protection net is regarded as a flexible structure, and the contact type is determined to be a rigid body-flexible body contact, and a surface-surface contact; And set the static friction coefficient of the contact interface and dynamic friction coefficient , to describe the friction behavior of the contact interface; At the same time, the energy dissipation when the falling rock hits the double-layer composite protective net is considered. The energy dissipation includes elastic energy , sliding energy Plasticity , which is expressed as follows: ; ; ; In the formula, The cross-sectional area of ​​the strand indicating the rockfall impact location; The elastic modulus of the steel strand at the rockfall impact location; Indicates the deformation at the rockfall impact location; Represents the force-displacement relationship function; Indicates the displacement of the double-layer composite protection net at the impact location of the rockfall; for A random number in a range; represents the force-displacement curve; The length of the strand that indicates the rockfall impact location.

[0011] Preferably, in step S2, the polyhedron rockfall model and double-layer composite protective net parameters are input into the finite element software, simulation is performed, and the deformation, stress distribution and energy absorption of the double-layer composite protective net during the rockfall impact are recorded as performance indicators.

[0012] Therefore, the present invention adopts the above-mentioned double-layer composite protective net and its optimization method, which has the following beneficial effects: 1. Multi-layer protection: The inner ring net (woven steel strands) and the outer grid net (composed of NPR steel strands) are used. The inner and outer layers of the protection net form a double barrier, which effectively disperses and absorbs the impact energy of falling rocks and improves the overall protection performance. The high strength of the inner protection net ensures reliable protection in extreme situations, while the small aperture design of the outer protection net can prevent smaller gravel or objects from passing through. 2. Application of spring buffers: Multiple spring buffers are set between the inner and outer protective nets to further enhance the shock absorption capacity of the system and reduce the impact force directly transmitted to the supporting piles and fixed structures; the number and distribution position of spring buffers can be adjusted according to actual conditions to flexibly adapt to different terrain and environmental requirements; 3. Optimization process based on numerical simulation: starting from building the obstacle model, after multiple simulation analyses and parameter adjustments, the optimal design solution is found, ensuring the scientificity and reliability of the final solution; Using advanced finite element analysis software to accurately simulate actual working conditions can accurately predict the performance of the protection net under various conditions, providing solid data support for engineering applications; 4. Comprehensive consideration of influencing factors: not only focusing on the static parameters of the protective net itself, such as geometric dimensions and material properties, but also fully considering dynamic factors such as the speed, mass, and impact angle of falling rocks, so that the optimization results are closer to the real scene; at the same time, in-depth research is conducted on the friction behavior of the contact interface and the energy dissipation mechanism, which helps to improve the system's ability to resist complex external loads; 5. Experimental verification: Experimental samples were made under laboratory conditions and actual tests were carried out to verify the effectiveness of the simulation results and further ensure the feasibility and safety of the design scheme. At the same time, the design was continuously improved and perfected based on experimental feedback, forming a closed-loop optimization system, which improved the success rate and technical level of the project.

[0013] In summary, the double-layer composite protective net and the optimization method thereof described in the present invention have the characteristics of reasonable structure, superior performance, scientific optimization, etc., and have broad application prospects in the fields of slope protection and the like.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is one of the layout diagrams of a double-layer composite protective net of the present invention; Figure 2 Another layout diagram of a double-layer composite protective net of the present invention; Figure 3 The present invention is a flowchart of an optimization method for a double-layer composite protective net.

[0016] Description of the drawings: 1. Outer protective net; 2. Inner protective net; 3. Tension plate; 4. Ground anchor; 5. Prestressed anchor cable; 6. Support pile; 7. Spring buffer. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in combination 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 used 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 reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0018] 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 explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products or devices.

[0019] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0020] like Figure 1 and Figure 2 As shown, a double-layer composite protective net includes supporting piles and a double-layer protective net structure fixed on both sides of the supporting piles, the double-layer protective net structure includes an inner protective net 2 arranged facing the rockfall impact side and an outer protective net 1 away from the rockfall impact side, wherein the inner protective net 2 is a ring net woven by steel strands, and the outer protective net 1 is a grid net composed of transverse NPR steel strands and longitudinal NPR steel strands, the aperture of the grid net is smaller than the aperture of the ring net, and the strength of the ring net is higher than the strength of the grid net; both ends of the inner protective net 2 and the outer protective net 1 are fixed to the slope via tension plates 3 and ground anchors 4 in turn, and the supporting piles 6 are fixed to the ground via prestressed anchor cables 5.

[0021] A plurality of spring buffers 7 are arranged between the outer protective net 1 and the inner protective net 2 .

[0022] like Figure 2 As shown, a method for optimizing a double-layer composite protective net comprises the following steps: S1. Based on a double-layer composite protection net and a polyhedron rockfall model, an obstruction model under rockfall impact conditions is constructed; Step S1 specifically includes the following steps: S11. Determine the geometric parameters of the double-layer composite protective net: set the aperture of the inner protective net , the intensity is ; and set the aperture of the outer protective net , the intensity is ;in, , ; At the same time, the cross-sectional area of ​​the supporting pile is set to , the distance between the outer protective net and the inner protective net is ; Set the number of spring buffers to , the elastic coefficient is ; S12. Establish a polyhedron rockfall model: determine the coordinates of each vertex of the rockfall, use the geometric modeling software to draw each face of the polyhedron according to the determined vertex coordinates, obtain the polyhedron model, and then import the polyhedron model into the physical simulation software, set the material properties of the rockfall and the mass of the rockfall , initial velocity and the impact angle is , S13. Construct a mechanical model of a double-layer composite protective net: Consider both the inner and outer protective nets as flexible structures, and establish a calculation formula for the total stiffness of the double-layer composite protective net: ; ; ; ; ; ; In the formula, Indicates the total stiffness of the double-layer composite protective net; Indicates the stiffness of the outer protective net; Indicates the stiffness of the inner protective net; Indicates the stiffness of the spring buffer; Indicates the number of steel strands of the inner protective net; It represents the elastic modulus of the steel strand; Indicates the cross-sectional area of ​​the steel strand; Indicates the length of the steel strand; and They represent the stiffness of the transverse NPR strand and the longitudinal NPR strand respectively; and They represent the number of transverse NPR steel strands and longitudinal NPR steel strands respectively; and They represent the elastic modulus of the transverse NPR steel strand and the longitudinal NPR steel strand respectively; and They represent the cross-sectional areas of the transverse NPR steel strand and the longitudinal NPR steel strand respectively; and Respectively represent the lengths of the transverse NPR steel strand and the longitudinal NPR steel strand; Indicates the number of spring buffers; Indicates the elastic coefficient of the spring buffer; S14, setting the contact condition between the falling rock and the double-layer composite protection net to obtain a contact model; S15, simulate the contact force between the falling rock and the double-layer composite protection net, and calculate the normal force at each time step according to the contact conditions and tangential force : ; ; In the formula, and denote the spring constants in the normal and tangential directions, respectively; and Represent the displacement in the normal and tangential directions respectively; and denote the normal and tangential velocity components respectively; and represent the normal viscous damping coefficient and the tangential viscous damping coefficient respectively; S16. Optimize the contact conditions described in step S14 using the simulation results of step S15, loop through steps S14 and S15 until the end condition is met, and output the obstruction model.

[0023] Preferably, in step S14, the rockfall is regarded as a rigid body, and the double-layer composite protection net is regarded as a flexible structure, and the contact type is determined to be a rigid body-flexible body contact, and a surface-surface contact; And set the static friction coefficient of the contact interface and dynamic friction coefficient , to describe the friction behavior of the contact interface; At the same time, the energy dissipation when the falling rock hits the double-layer composite protective net is considered. The energy dissipation includes elastic energy , sliding energy Plasticity , which is expressed as follows: ; ; ; In the formula, The cross-sectional area of ​​the strand indicating the rockfall impact location; The elastic modulus of the steel strand at the rockfall impact location; Indicates the deformation at the rockfall impact location; Represents the force-displacement relationship function; Indicates the displacement of the double-layer composite protection net at the impact location of the rockfall; for A random number in a range; represents the force-displacement curve; The length of the strand that indicates the rockfall impact location.

[0024] S2. Dynamically analyze the constructed obstruction model through numerical simulation software to evaluate the performance of the double-layer composite protection net under different rockfall speeds, rockfall masses and impact angles; In step S2, the polyhedron rockfall model and double-layer composite protective net parameters are input into the finite element software, and the simulation is performed to record the deformation, stress distribution and energy absorption of the double-layer composite protective net during the rockfall impact process as performance indicators.

[0025] S3, parameter adjustment: respectively adjust the size of the outer protective net and the inner protective net, the distance between the outer protective net and the inner protective net, the number and position distribution of the spring buffers, and re-enter the adjusted parameters into step S2 for simulation, compare the performance after each adjustment, and determine the optimal parameter combination; S4. Based on the optimal parameter combination, an experimental sample is prepared and an actual test is carried out under laboratory conditions to verify whether its protective effectiveness reaches the expected target. If the expected target is reached, the final solution is output, otherwise, the process returns to step S3; S5. Carry out construction according to the final plan.

[0026] The parameters involved in the final solution obtained by using the optimization method of the present invention are as follows: the aperture of the inner protection net is 0.08m; the aperture of the outer protection net is 0.02m; the cross-sectional area of ​​the support pile is 2m*3m; the spacing between the inner protection net and the outer protection net is 3m; the number of spring buffers is 50; the elastic coefficient of the spring buffer is 2000; the static friction coefficient is 0.6; the dynamic friction coefficient is 0.4; the total stiffness of the protection net obtained by using the above final solution is 180,000 N / m, which can intercept gravel with a particle size of more than 0.02m.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A double-layer composite protective net, characterized by: It includes a supporting pile and a double-layer protective net structure fixed on both sides of the supporting pile, the double-layer protective net structure includes an inner protective net arranged facing the rockfall impact side and an outer protective net away from the rockfall impact side, wherein the inner protective net is a ring net woven by steel strands, and the outer protective net is a grid net composed of transverse NPR steel strands and longitudinal NPR steel strands, the aperture of the square grid net is smaller than the aperture of the ring net, and the strength of the ring net is higher than the strength of the square grid net; Both ends of the inner protective net and the outer protective net are fixed to the slope via tension plates and ground anchors respectively, and the supporting piles are fixed to the ground via prestressed anchor cables.

2. A double-layer composite protective net according to claim 1, characterized in that: A plurality of spring buffers are arranged between the outer protective net and the inner protective net.

3. An optimization method for a double-layer composite protective net, characterized in that: The following steps are involved: S1. Based on the double-layer composite protective net and the polyhedron rockfall model described in claim 2, an obstruction model under rockfall impact conditions is constructed; S2. Dynamically analyze the constructed obstruction model through numerical simulation software to evaluate the performance of the double-layer composite protection net under different rockfall speeds, rockfall masses and impact angles; S3, parameter adjustment: respectively adjust the size of the outer protective net and the inner protective net, the distance between the outer protective net and the inner protective net, the number and position distribution of the spring buffers, and re-enter the adjusted parameters into step S2 for simulation, compare the performance after each adjustment, and determine the optimal parameter combination; S4. Based on the optimal parameter combination, an experimental sample is prepared and an actual test is carried out under laboratory conditions to verify whether its protective effectiveness reaches the expected target. If the expected target is reached, the final solution is output, otherwise, the process returns to step S3; S5. Carry out construction according to the final plan.

4. The optimization method of a double-layer composite protective net according to claim 3, characterized in that: Step S1 specifically includes the following steps: S11. Determine the geometric parameters of the double-layer composite protective net: set the aperture of the inner protective net , the intensity is ; and set the aperture of the outer protective net , the intensity is ;in, , ; At the same time, the cross-sectional area of ​​the supporting pile is set to , the distance between the outer protective net and the inner protective net is ; Set the number of spring buffers to , the elastic coefficient is ; S12. Establish a polyhedron rockfall model: determine the coordinates of each vertex of the rockfall, use the geometric modeling software to draw each face of the polyhedron according to the determined vertex coordinates, obtain the polyhedron model, and then import the polyhedron model into the physical simulation software, set the material properties of the rockfall and the mass of the rockfall , initial speed and the impact angle is , S13. Construct a mechanical model of a double-layer composite protective net: Consider both the inner and outer protective nets as flexible structures, and establish a calculation formula for the total stiffness of the double-layer composite protective net: ； ； ； ； ； ； In the formula, Indicates the total stiffness of the double-layer composite protective net; Indicates the stiffness of the outer protective net; Indicates the stiffness of the inner protective net; Indicates the stiffness of the spring buffer; Indicates the number of steel strands of the inner protective net; It represents the elastic modulus of the steel strand; Indicates the cross-sectional area of ​​the steel strand; Indicates the length of the steel strand; and They represent the stiffness of the transverse NPR strand and the longitudinal NPR strand respectively; and They represent the number of transverse NPR steel strands and longitudinal NPR steel strands respectively; and They represent the elastic modulus of the transverse NPR steel strand and the longitudinal NPR steel strand respectively; and They represent the cross-sectional areas of the transverse NPR steel strand and the longitudinal NPR steel strand respectively; and Respectively represent the lengths of the transverse NPR steel strand and the longitudinal NPR steel strand; Indicates the number of spring buffers; Indicates the elastic coefficient of the spring buffer; S14, setting the contact condition between the falling rock and the double-layer composite protection net to obtain a contact model; S15, simulate the contact force between the falling rock and the double-layer composite protection net, and calculate the normal force at each time step according to the contact conditions and tangential force : ； ； In the formula, and denote the spring constants in the normal and tangential directions, respectively; and Represent the displacement in the normal and tangential directions respectively; and denote the normal and tangential velocity components respectively; and represent the normal viscous damping coefficient and the tangential viscous damping coefficient respectively; S16. Optimize the contact conditions described in step S14 using the simulation results of step S15, loop through steps S14 and S15 until the end condition is met, and output the obstruction model.

5. The optimization method of a double-layer composite protective net according to claim 4, characterized in that: In step S14, the rockfall is regarded as a rigid body, and the double-layer composite protection net is regarded as a flexible structure, and the contact type is determined to be a rigid body-flexible body contact and a surface-surface contact; And set the static friction coefficient of the contact interface and dynamic friction coefficient , to describe the friction behavior of the contact interface; At the same time, the energy dissipation when the falling rock hits the double-layer composite protective net is considered. The energy dissipation includes elastic energy , sliding energy Plasticity , which is expressed as follows: ； ； ； In the formula, The cross-sectional area of ​​the strand indicating the rockfall impact location; The elastic modulus of the steel strand at the rockfall impact location; Indicates the deformation at the rockfall impact location; Represents the force-displacement relationship function; The displacement of the double-layer composite protection net at the impact location of the rockfall; for A random number in a range; represents the force-displacement curve; The length of the strand that indicates the rockfall impact location.

6. The optimization method of a double-layer composite protective net according to claim 5, characterized in that: In step S2, the polyhedron rockfall model and double-layer composite protective net parameters are input into the finite element software, and the simulation is performed to record the deformation, stress distribution and energy absorption of the double-layer composite protective net during the rockfall impact process as performance indicators.

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