Honeycomb-like structure noise reduction device for subway shield tunnel and evaluation method of honeycomb-like structure noise reduction device

Abstract

The invention relates to a novel noise reduction device aiming at the noise problem in a subway shield tunnel and an evaluation method of the novel noise reduction device. The device is a honeycomb-multilayer composite sound energy absorption device based on a honeycomb structure, the device is composed of a multilayer honeycomb energy absorption pad structure, the reflection frequency of noise entering the absorption pad is greatly increased, and the laying condition of shield tunnel bent duct pieces can be adapted through unitized honeycomb holes. And meanwhile, a vehicle-track-infrastructure vibration noise analysis model containing a fluid domain is established as an evaluation method, so that the noise reduction performance of the device can be evaluated and verified. According to the honeycomb-multilayer composite sound energy absorption device, the porous material with an excellent sound absorption effect is adopted, so that the honeycomb-multilayer composite sound energy absorption device has independent noise reduction capability in structure and material, the composite noise reduction capability is more excellent, the established evaluation method can be suitable for device performance modulation of various scenes, and the evaluation method is suitable for popularization and application. And the method has relatively high universality.

Description

Technical Field

[0001] The present invention belongs to the technical field of vibration reduction of rail transit structures, and in particular relates to a honeycomb-like structure noise reduction device for a subway shield tunnel and an evaluation method thereof. Background Art

[0002] With the rapid development of urban economy and the increasing population density, subway, as an important part of large-scale urban transportation system, has been widely promoted and constructed due to its high efficiency, speed and environmental protection. Shield technology, as the main method of subway tunnel construction, has been widely used due to its advantages of high degree of automation, fast construction speed and small impact on the environment.

[0003] However, the noise problem generated by shield tunnels during construction and operation has become increasingly prominent. The noise in subway shield tunnels mainly comes from the running of trains and ventilation equipment. Due to the characteristics of closed spaces and the various noises generated by subway operations, this not only affects the comfort of citizens, but also has an adverse impact on the health of subway workers and the surrounding environment.

[0004] Traditional noise reduction measures, such as the use of special track pads, elastic supports and other vibration reduction equipment to achieve the effect of noise reduction at the source by optimizing wheel and track design to reduce friction noise; setting up sound barriers or sound-absorbing materials inside the tunnel to reduce the reflection and propagation of noise inside the tunnel. Although these noise reduction measures have certain effects, with the advancement of science and technology and the improvement of environmental standards, these traditional measures have gradually failed to meet the noise control needs in modern urban subway tunnels in terms of cost, installation difficulty, and maintenance complexity. Under conditions such as the large curvature of the shield tunnel segment and the restricted confined space, the noise reduction means of the subway shield tunnel space need to adopt more comprehensive measures, and the noise reduction equipment needs more accurate noise frequency identification and noise reduction effect, as well as more convenient installation and maintenance methods, so as to ensure that the subway system is more harmoniously integrated into urban life and guarantee the quality of life of passengers and residents. For this type of external lightweight noise reduction device, its noise reduction effect needs to be evaluated before installation, especially its noise absorption effect on the special frequency band of wheel-rail noise caused by vehicles passing through the track in the closed space of the shield tunnel. Currently, there is still a lack of a rapid analysis and evaluation method suitable for the paving project of noise reduction device. Summary of the invention

[0005] In order to solve the above-mentioned technical problems, the present invention provides a honeycomb-like structure noise reduction device for a subway shield tunnel and an evaluation method thereof. A honeycomb-like structure is used to make a honeycomb-multilayer composite sound energy absorption device, and an evaluation method based on finite element simulation calculation is established to evaluate and optimize the noise reduction effect of the device.

[0006] The technical solutions specifically adopted in the present invention are as follows:

[0007] In the first aspect, the present invention provides a honeycomb structure noise reduction device for a subway shield tunnel, wherein the noise reduction device is a multi-layer honeycomb energy absorption composite structure laid on the wall of the subway shield tunnel above the roadbed height, wherein the multi-layer honeycomb energy absorption composite structure is composited by multi-layer honeycomb energy absorption pads in the form of staggered stacking; each layer of honeycomb energy absorption pad is a porous material composed of a continuous solid phase skeleton and fluid-filled pores, wherein the fluid-filled pores distributed in the continuous solid phase skeleton are in the shape of regular hexagonal honeycomb holes on the plane; in the multi-layer honeycomb energy absorption composite structure, the regular hexagonal honeycomb holes in the upper and lower layers of honeycomb energy absorption pads are completely staggered and not through.

[0008] As a preferred embodiment of the first aspect, in the honeycomb energy absorption pad, the continuous solid phase skeleton is made of melamine material, and the fluid medium filled in the fluid-filled pores is air.

[0009] As a preferred embodiment of the first aspect, the honeycomb energy absorption pad is obtained by machining regular hexagonal honeycomb holes arranged in a honeycomb structure on a sound-absorbing plate of a continuous solid-phase skeleton material.

[0010] In a second aspect, the present invention provides a method for evaluating the noise reduction effect of the honeycomb-like noise reduction device for a subway shield tunnel as described in the first aspect, comprising:

[0011] S1: A macroscopic dynamic model including a vehicle model, a track model, a tunnel model, a wheel-rail contact model, a surface acoustic cavity model and a fluid domain model is established using the finite element method to calculate the incident acoustic field; the vehicle model, the track model and the tunnel model are assembled according to the actual spatial position; the wheel-rail contact model is used to connect the vehicle model and the track model and calculate the wheel-rail interaction; the surface acoustic cavity model is a layer of acoustic cavity units covering the surface around the vehicle model, which is used to apply the incident acoustic field to the tunnel surface through the fluid domain when calculating the reflected noise;

[0012] S2: setting the surface acoustic cavity model of the vehicle model surface to an inactive state, then after importing the wheel-rail noise excitation into the wheel-rail contact model, running the macroscopic dynamics model to perform vehicle-rail coupling dynamics calculation, thereby calculating the wheel-rail noise caused by the movement of the vehicle model, and at the same time using the fluid domain to calculate the aerodynamic noise, superimposing the wheel-rail noise and the aerodynamic noise to obtain the noise field distribution in the tunnel; extracting the sound field distribution of the vehicle model surface from the noise field distribution in the tunnel, and importing the extracted surface sound field into the surface acoustic cavity model as the incident sound field excitation when calculating the reflected noise;

[0013] S3: for the design scheme to be evaluated of the noise reduction device, establish a noise reduction device sub-model according to the parameters in the design scheme to be evaluated, and assemble it on the inner wall of the tunnel model of the macrodynamic model according to the laying position designed in the design scheme to be evaluated;

[0014] S4: Based on the finite element model assembled by the noise reduction device sub-model and the macro-dynamic model in S3, the vehicle-track coupling dynamics calculation is no longer performed. The incident sound field excitation is directly applied to the noise reduction device sub-model on the tunnel surface through the surface acoustic cavity model via the fluid domain, the reflected noise space is simulated and calculated, and noise measurement points are selected on the vehicle body surface to record the reflected noise size, so as to evaluate the noise reduction amount before and after the application of the noise reduction device.

[0015] As a preferred embodiment of the above-mentioned second aspect, in the macro-dynamic model described in step S1, the vehicle model is a multi-body dynamic model, the track model and the tunnel model are modeled by solid units, the fluid domain model is modeled by fluid units, the surfaces of the vehicle model, the track model and the tunnel model are set as no-slip walls, and infinite unit boundaries are set at both ends of the fluid domain; when running the macro-dynamic model to perform vehicle-track coupled dynamics calculations, in the near field where the vehicle and the fluid domain are in contact, the CFD (computational fluid dynamics) method is used to solve the sound source flow field considering the turbulent effect, and according to the pressure and flow velocity calculated from the sound source flow field, the Lighthill body sound source model is used to obtain the sound source of the aerodynamic noise and use it as the source term to calculate the sound propagation, and predict the far-field radiated noise.

[0016] As a preferred embodiment of the second aspect, in step S2, when introducing the wheel-rail noise excitation into the wheel-rail contact model, the measured wheel-rail roughness spectrum or the measured wheel-rail noise is selected as the sound source excitation.

[0017] As a preferred embodiment of the second aspect, in step S3, a standard absorbent pad specimen is processed based on the design to be evaluated, and the density (kg / m 3 ), flow resistance (N·s / m 4 ), porosity and tortuosity are measured, and the sound absorption coefficient of the standard specimen of the absorption pad at different frequencies is measured by standard specimen testing; when establishing the noise reduction device sub-model, each layer of honeycomb energy absorption pad in the noise reduction device is simplified and modeled as a layer of plate body that meets the measured parameters, and there is no need to model the internal structure of each layer of honeycomb energy absorption pad.

[0018] As a preferred embodiment of the above-mentioned second aspect, all optimizable parameters of the noise reduction device are used as control variables, the sound pressure values ​​of the noise reduction amount before and after the application of the noise reduction device are set as the objective function, the constraints and upper and lower limits that each control variable should meet are defined, and an optimization algorithm is used to iterate and optimize all optimizable parameters to obtain the optimal parameter combination of the noise reduction device.

[0019] As a preferred embodiment of the second aspect, the optimizable parameters in the noise reduction device include the number of stacked layers of honeycomb energy absorption pads and the size of the regular hexagonal honeycomb holes in each layer of honeycomb energy absorption pads.

[0020] As a preferred embodiment of the second aspect, the optimization algorithm adopts a moving asymptotes algorithm (Method of Moving Asymptotes, MMA).

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The present invention provides a honeycomb-like structure noise reduction device for a subway shield tunnel. The noise reduction device is composed of a honeycomb-like structure to form a honeycomb-multilayer composite sound energy absorption device. It has independent noise reduction capabilities in terms of structure and material, making its composite noise reduction capability more outstanding. The use of an integrated processing method for a porous sound-absorbing material plate can reduce processing costs and difficulty. At the same time, the honeycomb-like unitized structure can be appropriately bent and cut as needed, so that it can directly fit on the curved and uneven surface of the shield tunnel segment, and is easy to disassemble without affecting the maintenance of the segment itself, pipeline layout, etc.

[0023] The evaluation method proposed in the present invention adopts a modular design concept. It first calculates the initial unreduced noise field through vehicle-track coupling dynamics, then introduces the noise reduction device sub-model, and introduces the initial unreduced sound field into the surface acoustic cavity model as the sound source excitation of the noise reduction sub-model, so that when performing a refined evaluation, there is no need to perform large-scale vehicle motion and wheel-rail coupling vibration calculations. While maintaining the calculation accuracy, the calculation cost is greatly reduced, and a model space with simple calculations and fast solutions is provided for the introduction of optimization algorithms. In addition, the evaluation method can be used for the design and evaluation of the noise reduction device in the present invention. At the same time, after adjusting the vehicle, track, and infrastructure according to actual needs, it can also be adapted to the vibration reduction and noise reduction design and evaluation of other scenarios, and has strong scene adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the laying method of the honeycomb-multilayer composite sound energy absorbing device;

[0025] Figure 2 It is a cross-sectional view of a single honeycomb unit cell structure (the upper side of the figure is the side close to the noise source);

[0026] Figure 3 It is a schematic diagram of the overall structure of a single-layer honeycomb energy absorption pad;

[0027] Figure 4 It is a schematic diagram of the combination of honeycomb unit cell structures in a single-layer honeycomb energy absorption pad structure;

[0028] Figure 5 It is a flow chart of the main steps of the evaluation method of the honeycomb-like noise reduction device for subway shield tunnels;

[0029] Figure 6 This is a schematic diagram of the relative position relationship of each model in the evaluation method.

[0030] Figure 7 This is a schematic diagram of the data flow during the noise reduction evaluation process in the evaluation method of the present invention.

[0031] Figure 8 Schematic diagram of the positions of measuring points 1 to 3 for comparing the noise reduction effect in an embodiment of the present invention

[0032] Fig. 9 This is a data comparison diagram of measuring point 1 of the melamine board honeycomb-multilayer composite sound energy absorbing device in an embodiment of the present invention;

[0033] Fig.10 This is a data comparison diagram of measuring point 2 of the melamine board honeycomb-multilayer composite sound energy absorbing device in an embodiment of the present invention;

[0034] Fig.11 This is a data comparison diagram of measuring point 3 of the melamine board honeycomb-multilayer composite sound energy absorbing device in an embodiment of the present invention; DETAILED DESCRIPTION

[0035] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0036] In the description of the present invention, it is to be understood that when an element is considered to be "connected" to another element, it may be directly connected to the other element or indirectly connected, that is, there are intermediate elements. On the contrary, when an element is said to be "directly" connected to another element, there are no intermediate elements.

[0037] like Figure 1As shown, in an embodiment of the present invention, a honeycomb structure noise reduction device for a subway shield tunnel is provided. The honeycomb structure noise reduction device is a multi-layer honeycomb energy absorption composite structure, which is composed of a plurality of honeycomb energy absorption pads in the form of staggered stacking. The multi-layer honeycomb energy absorption composite structure is bent and paved to fit the inner wall of the tunnel above the roadbed height. Each layer of honeycomb energy absorption pad is a porous material composed of a continuous solid phase skeleton and fluid-filled pores, wherein the fluid-filled pores distributed in the continuous solid phase skeleton are in the shape of regular hexagonal honeycomb holes on the plane. In the multi-layer honeycomb energy absorption composite structure, a single regular hexagonal honeycomb hole is a honeycomb unit cell. Figure 2 The structural cross-section of the honeycomb unit cell is shown ( Figure 2 The upper side is the side close to the noise source), it can be seen that the regular hexagonal honeycomb holes in the upper and lower layers of honeycomb energy absorption pads are completely staggered and cannot be directly connected. The multi-layer honeycomb energy absorption pad structure has a large number of Figure 2 As shown in the figure, each honeycomb unit cell is a sound absorbing cavity, and the upper and lower layers of the sound absorbing cavity are completely staggered, so that the sound waves can be absorbed to the greatest extent after being incident and no longer reflected back into the tunnel space.

[0038] The honeycomb energy absorption pad can be obtained by processing a sound absorption plate made of a continuous solid skeleton material into regular hexagonal honeycomb holes arranged in a honeycomb structure. Figure 3 As shown, during production, a sound-absorbing board made of a continuous solid skeleton material can be processed on a plane into a series of Figure 2 The honeycomb unit cell structure shown in the figure. The edges of the hexagonal honeycomb unit cell structure are closely connected to each other, such as Figure 4 As shown. The specific structural dimensions of the regular hexagonal honeycomb holes can be reasonably optimized and designed according to actual needs. At the same time, the specific stacking number of the honeycomb energy absorption pad can also be reasonably adjusted according to actual needs. Since the regular hexagonal honeycomb holes of two adjacent layers of honeycomb energy absorption pads are completely staggered during stacking, the number of reflections when the noise enters the absorption pad is greatly increased, achieving the effect of energy absorption and noise reduction. In theory, the more stacking numbers, the better the noise reduction effect.

[0039] Meanwhile, in the honeycomb energy absorbing pad, the continuous solid phase skeleton and the fluid medium filled in the fluid-filled pores can also be adjusted according to actual needs. In an embodiment of the present invention, the continuous solid phase skeleton can be made of melamine material with low cost, light weight and easy processing, and the fluid medium filled in the fluid-filled pores can be air.

[0040] Since the number of layers of honeycomb energy absorption pads and the structural parameters of each layer of honeycomb energy absorption pads in the above-mentioned honeycomb-like structure noise reduction device for subway shield tunnels will affect the final noise reduction effect. Therefore, before producing the finished product of the above-mentioned honeycomb-like structure noise reduction device for subway shield tunnels, the noise reduction effect of each design scheme of the noise reduction device can be pre-evaluated to determine whether it is necessary to continue to optimize the parameters of the noise reduction device. For each design scheme of the noise reduction device to be evaluated, the specific evaluation method mainly includes the following steps:

[0041] S1: Establishing macro-dynamic model: Using finite element method, establish macro-dynamic model including vehicle model, track model, tunnel model, wheel-rail contact model, surface acoustic cavity model and fluid domain model to calculate the incident acoustic field. Figure 6 As shown, in this macro-dynamic model, the vehicle model, track model and tunnel model are assembled according to the actual spatial position; the wheel-rail contact model is used to connect the vehicle model and the track model and calculate the wheel-rail interaction; the surface acoustic cavity model is a layer of acoustic cavity units covering the surface around the vehicle model, which is used to apply the incident sound field to the tunnel surface through the fluid domain when calculating the reflected noise, but it is closed when calculating the initial sound field and does not need to be activated, and is only activated when calculating the reflected noise.

[0042] In an embodiment of the present invention, in the macro-dynamic model described in step S1, the vehicle model is a multi-body dynamic model, the track model and the tunnel model are modeled by solid units, and the fluid domain model is modeled by fluid units. The surfaces of the vehicle model, track model and tunnel model are set as non-slip walls, and infinite unit boundaries are set at both ends of the fluid domain. The specific structural parameters of each model can be determined according to measured data or design documents.

[0043] S2: Calculate the incident sound field: Figure 7 As shown, the surface acoustic cavity model of the vehicle model surface is set to an inactive state, and then after the wheel-rail noise excitation is introduced into the wheel-rail contact model, the macro dynamics model is run to perform vehicle-rail coupling dynamics calculation, thereby calculating the wheel-rail noise caused by the movement of the vehicle model, and at the same time using the fluid domain to calculate the aerodynamic noise, and the wheel-rail noise and aerodynamic noise are superimposed to calculate the noise field distribution in the tunnel. Then, the sound field distribution of the vehicle model surface is extracted from the above-mentioned noise field distribution in the tunnel, and the extracted surface sound field is introduced into the surface acoustic cavity model as the incident sound field excitation when calculating the reflected noise.

[0044] In an embodiment of the present invention, in the above step S2, when the wheel-rail noise excitation is introduced into the wheel-rail contact model, the measured wheel-rail roughness spectrum or the measured wheel-rail noise can be selected as the sound source excitation.

[0045] In addition, when running the macro-dynamic model to perform vehicle-track coupled dynamics calculations, in the near field where the vehicle contacts the fluid domain, the CFD (computational fluid dynamics) method is used to solve the sound source flow field considering the turbulence effect. According to the pressure and flow velocity calculated from the sound source flow field, the Lighthill body sound source model is used to obtain the sound source of the aerodynamic noise and use it as the source term to calculate the sound propagation and predict the far-field radiated noise.

[0046] The above-mentioned surface acoustic cavity model is mainly used to store the noise field distribution on the surface of the vehicle model obtained by superposition calculation. The noise field can be directly applied as a sound source excitation to the subsequently established noise reduction device sub-model without the need to repeat large-scale vehicle-track coupling dynamics calculations, thereby improving the efficiency of the evaluation.

[0047] S3: Establish and assemble a noise reduction device sub-model: For the design scheme to be evaluated of the noise reduction device, establish a noise reduction device sub-model according to the parameters in the design scheme to be evaluated, and assemble it on the inner wall of the tunnel model of the macro-dynamic model according to the laying position of the noise reduction device designed in the design scheme to be evaluated.

[0048] S4: Calculation of the reflected noise sound field after noise reduction: Based on the finite element model assembled by the noise reduction device sub-model and the macro-dynamic model in S3, the vehicle-track coupling dynamic calculation is no longer performed. The incident sound field excitation is directly applied to the noise reduction device sub-model on the tunnel surface through the surface acoustic cavity model via the fluid domain, the reflected noise space is simulated and calculated, and noise measurement points are selected on the vehicle body surface to record the reflected noise size, so as to evaluate the noise reduction amount before and after the application of the noise reduction device.

[0049] Therefore, based on the above steps S1 to S4, the noise reduction amount before and after application can be obtained through simulation for each design scheme to be evaluated of the noise reduction device.

[0050] In addition, based on this evaluation method, the optimization algorithm can be further set or the parameters such as the size and stacking method of the noise reduction device can be manually adjusted, and S3 to S4 can be repeated to compare the calculated reflection noise and the noise reduction amount after the noise reduction devices with different design parameters are introduced, and the optimal solution can be selected. The overall process is as follows: Figure 5 shown.

[0051] It is worth noting that if Figure 7 As shown in the figure, when S2 calculates the initial incident sound field, the surface acoustic cavity model is not activated. The main function of the surface acoustic cavity model is to store the initial incident sound field calculated in the previous step and use it as the sound source excitation for the surface acoustic cavity model introduced in S4. The sound source excitation can be directly applied to the noise reduction device sub-model established in S3, so that there is no need to perform large-scale vehicle motion and wheel-rail coupling vibration calculations when performing refined evaluation.

[0052] In addition, in the above S4, the vehicle, track, etc. are all in a stationary state, and are only used to provide solid boundaries for noise conduction and reflection during the calculation process. This is because the speed of sound in air is 340m / s, and the speed of sound in solids, especially metals, is often greater than 1000m / s, while the actual speed of subway trains is difficult to exceed 30m / s. In addition, the space in the tunnel is small. When calculating the changes in reflected noise, the movement of the train can be temporarily ignored to reduce the calculation cost while ensuring relative accuracy.

[0053] In addition, when constructing the noise reduction device sub-model in step S3, a refined model can be constructed in a finite element environment based on the specific internal structure design of each layer of honeycomb energy absorption pad in the noise reduction device (including a continuous solid phase skeleton and fluid-filled pores), thereby simulating the absorption and reflection of noise by the noise reduction device. However, in the embodiment of the present invention, considering the efficiency of the simulation, when the test conditions are met, a standard specimen of the absorption pad can also be processed based on the design to be evaluated, and the density (kg / m 3 ), flow resistance (N·s / m 4 ), porosity and tortuosity are used for parameter determination. At the same time, the sound absorption coefficient of the standard specimen of the absorption pad at different frequencies is measured through standard specimen testing and recorded in the measured parameters. Therefore, when establishing the noise reduction device sub-model, each layer of honeycomb energy absorption pad in the noise reduction device in the scheme to be evaluated is simplified and modeled as a layer of plate body that meets the measured parameters, and there is no need to model the internal structure of each layer of honeycomb energy absorption pad. Based on this approach, the noise reduction device can be equivalent to a multi-layer plate structure instead of a refined sub-model for calculation. In the noise reduction device model established in the embodiment of the present invention, a single-layer honeycomb energy absorption pad uses a melamine board processed with regular hexagonal honeycomb holes. There are a total of 24 layers of absorption pads in the noise reduction device with a total thickness of 12 cm. In the early stage, a standard specimen of melamine board was obtained through scaled material testing. After optimization analysis, the regular hexagonal honeycomb holes in the melamine board are according to Figure 2 The shape shown is designed to be small at the top and large at the bottom in cross section. The honeycomb hole side length corresponding to the smallest cross section of the top honeycomb hole is 3 mm, the honeycomb hole side length corresponding to the largest cross section of the bottom honeycomb hole is 5 mm, and the thickness of the single-layer melamine board is 5 mm. Finally, after the actual test of the processed absorption pad standard specimen, the melamine board material parameters used to input the model are shown in Table 1.

[0054] Table 1 Melamine board material parameters

[0055] Material Name Melamine foam <![CDATA[Density (kg / m 3 )]]> 8.8 <![CDATA[Flow resistance rate (N·s / m 4 )]]> <![CDATA[1.09×10 3 ]]> Void ratio 0.99 Tortuosity 1.02

[0056] In the two types of sound fields obtained in S2 and S4 before and after the installation of the noise reduction device, the sound pressure at the typical measuring points is extracted for comparison. In this embodiment, the control group without sound-absorbing material pasted on the tunnel wall is compared with the experimental group of the honeycomb-multilayer composite sound energy absorber with melamine board material pasted on it, and finally the noise reduction after the introduction of the multi-layer honeycomb energy absorption pad can be analyzed. The selected indicator is the one-third octave band sound pressure, and the selected measuring points 1-3 are as follows: Figure 8 The noise pressure of the control group without sound-absorbing material pasted on the wall and the experimental group with melamine board material is shown in Fig. 9 , Fig.10 and Fig.11 .

[0057] Depend on Fig. 9 and Fig.11 It can be seen that under the working condition of "no sound-absorbing material pasted on the wall", the maximum sound pressure level of measuring points 1-3 in the frequency band exceeds 67dB, which means that without taking any vibration reduction measures, the sound pressure is very likely to be too high within 25m along the tunnel, causing physical and psychological discomfort to the human body. Under the working condition of "melamine board honeycomb-multi-layer composite sound energy absorber", the maximum sound pressure level at each measuring point is less than the corresponding value in working condition 1, which shows that after using the melamine board honeycomb-multi-layer composite sound energy absorber, the sound pressure inside the tunnel has been significantly reduced.

[0058] In the 20-200Hz frequency band, the sound pressure level of the melamine honeycomb-multi-layer composite sound energy absorber is almost the same as that of the non-sound absorbing material. The sound pressure drops the most at 160Hz, and the average drop of the three measuring points is 4dB. In the 200-2000Hz frequency band, the sound pressure level of the melamine honeycomb-multi-layer composite sound energy absorber and the non-sound absorbing material is significantly reduced at some frequencies. At measuring point 2, the sound pressure at 315Hz and 400Hz is reduced by 18dB, and at 1600Hz, the three measuring points are reduced by an average of 9dB. It can be seen that the melamine honeycomb-multi-layer composite sound energy absorber has a good noise reduction effect in the 200-2000Hz frequency band. In the frequency band of 2000-8000Hz, the sound pressure of the melamine board honeycomb-multi-layer composite sound energy absorber at some frequencies is also significantly reduced, among which the sound pressure at 2500Hz, 3150Hz, and 4000Hz is reduced by 24dB, 10dB, and 21dB at most. There is also a slight decrease or basically remains the same at other frequencies. It can be seen that the melamine board honeycomb-multi-layer composite sound energy absorber also has a good noise reduction level in the high-frequency band.

[0059] In summary, the noise reduction device based on the multi-layer honeycomb energy absorption pad structure in the present invention can greatly increase the number of reflections when the noise enters the absorption pad, and the unitized honeycomb holes can also adapt to the laying conditions of the curved segments of the shield tunnel. At the same time, the present invention also establishes a vehicle-track-infrastructure vibration noise analysis model including a fluid domain as an evaluation method to evaluate and verify the noise reduction performance of the device. The honeycomb-multi-layer composite sound energy absorption device adopts porous materials with excellent sound absorption effects, so that the honeycomb-multi-layer composite sound energy absorption device has the ability to independently reduce noise in structure and material, making its composite noise reduction ability more excellent. The established evaluation method can be applied to the device performance modulation of various scenarios and has strong versatility.

[0060] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A honeycomb-like noise reduction device for a subway shield tunnel, characterized in that: The noise reduction device is a multi-layer honeycomb energy absorption composite structure laid on the wall of a subway shield tunnel above the roadbed height, and the multi-layer honeycomb energy absorption composite structure is composed of a plurality of honeycomb energy absorption pads in the form of staggered stacking; each layer of honeycomb energy absorption pad is a porous material composed of a continuous solid phase skeleton and fluid-filled pores, wherein the fluid-filled pores distributed in the continuous solid phase skeleton are in the shape of regular hexagonal honeycomb holes on the plane; in the multi-layer honeycomb energy absorption composite structure, the regular hexagonal honeycomb holes in the upper and lower layers of honeycomb energy absorption pads are completely staggered and not through.

2. The honeycomb-like noise reduction device for subway shield tunnel according to claim 1, characterized in that: In the honeycomb energy absorption pad, the continuous solid phase skeleton is made of melamine material, and the fluid medium filled in the fluid-filled pores is air.

3. The honeycomb-like noise reduction device for a subway shield tunnel according to claim 1, characterized in that: The honeycomb energy absorption pad is obtained by machining regular hexagonal honeycomb holes arranged in a honeycomb structure on a sound absorption plate made of a continuous solid-phase skeleton material.

4. A method for evaluating the noise reduction effect of the honeycomb-like noise reduction device for a subway shield tunnel as claimed in claim 1, characterized in that: include: S1: A macroscopic dynamic model including a vehicle model, a track model, a tunnel model, a wheel-rail contact model, a surface acoustic cavity model and a fluid domain model is established using the finite element method to calculate the incident acoustic field; the vehicle model, the track model and the tunnel model are assembled according to the actual spatial position; the wheel-rail contact model is used to connect the vehicle model and the track model and calculate the wheel-rail interaction; the surface acoustic cavity model is a layer of acoustic cavity units covering the surface around the vehicle model, which is used to apply the incident acoustic field to the tunnel surface through the fluid domain when calculating the reflected noise; S2: setting the surface acoustic cavity model of the vehicle model surface to an inactive state, then after importing the wheel-rail noise excitation into the wheel-rail contact model, running the macroscopic dynamics model to perform vehicle-rail coupling dynamics calculation, thereby calculating the wheel-rail noise caused by the movement of the vehicle model, and at the same time using the fluid domain to calculate the aerodynamic noise, superimposing the wheel-rail noise and the aerodynamic noise to obtain the noise field distribution in the tunnel; extracting the sound field distribution of the vehicle model surface from the noise field distribution in the tunnel, and importing the extracted surface sound field into the surface acoustic cavity model as the incident sound field excitation when calculating the reflected noise; S3: for the design scheme to be evaluated of the noise reduction device, establish a noise reduction device sub-model according to the parameters in the design scheme to be evaluated, and assemble it on the inner wall of the tunnel model of the macrodynamic model according to the laying position designed in the design scheme to be evaluated; S4: Based on the finite element model assembled by the noise reduction device sub-model and the macro-dynamic model in S3, the vehicle-track coupling dynamics calculation is no longer performed. The incident sound field excitation is directly applied to the noise reduction device sub-model on the tunnel surface through the surface acoustic cavity model via the fluid domain, the reflected noise space is simulated and calculated, and noise measurement points are selected on the vehicle body surface to record the reflected noise size, so as to evaluate the noise reduction amount before and after the application of the noise reduction device.

5. The noise reduction effect evaluation method according to claim 4, characterized in that: In the macro-dynamic model of step S1, the vehicle model is a multi-body dynamic model, the track model and the tunnel model are modeled by solid units, the fluid domain model is modeled by fluid units, the surfaces of the vehicle model, the track model and the tunnel model are set as no-slip walls, and infinite unit boundaries are set at both ends of the fluid domain; When running the macro-dynamic model to perform vehicle-track coupled dynamics calculations, in the near field where the vehicle contacts the fluid domain, the computational fluid dynamics method is used to solve the sound source flow field considering the turbulence effect. Based on the pressure and flow velocity calculated from the sound source flow field, the Lighthill body sound source model is used to obtain the sound source of the aerodynamic noise and use it as the source term to calculate the sound propagation and predict the far-field radiated noise.

6. The noise reduction effect evaluation method according to claim 4, characterized in that: In step S2, when the wheel-rail noise excitation is introduced into the wheel-rail contact model, the measured wheel-rail roughness spectrum or the measured wheel-rail noise is selected as the sound source excitation.

7. The noise reduction effect evaluation method according to claim 4, characterized in that: In step S3, a standard specimen of the absorption pad is processed based on the design scheme to be evaluated, and the density, flow resistivity, porosity and tortuosity of the standard specimen of the absorption pad are measured. At the same time, the sound absorption coefficient of the standard specimen of the absorption pad at different frequencies is obtained by testing and measuring the standard specimen. When establishing the noise reduction device sub-model, each layer of honeycomb energy absorption pad in the noise reduction device is simplified and modeled as a layer of plate that meets the measured parameters, and there is no need to model the internal structure of each layer of honeycomb energy absorption pad.

8. The noise reduction effect evaluation method according to claim 4, characterized in that: All optimizable parameters of the noise reduction device are used as control variables, the sound pressure values ​​of the noise reduction amount before and after the application of the noise reduction device are set as the objective function, the constraints and upper and lower limits that each control variable should meet are defined, and an optimization algorithm is used to iterate and optimize all optimizable parameters to obtain the optimal parameter combination of the noise reduction device.

9. The noise reduction effect evaluation method according to claim 8, characterized in that: The optimizable parameters in the noise reduction device include the number of superimposed layers of the honeycomb energy absorption pads and the size of the regular hexagonal honeycomb holes in each layer of the honeycomb energy absorption pads.

10. The noise reduction effect evaluation method according to claim 8, characterized in that: The optimization algorithm adopts a moving asymptote algorithm.

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