A method for vibration isolation of a model tunnel in a centrifuge model test

Abstract

The application discloses a vibration reduction and isolation device for a model tunnel in a centrifugal model test, which comprises a model box, the periphery and the bottom surface of the inside of the model box are paved with damping materials, the model box is filled with sand, an aluminum pile and the model tunnel are placed in the sand, the model tunnel is located on one side of the aluminum pile, a vibration exciter is in contact with the aluminum pile, the vibration exciter is fixedly connected with a movable rod, and a plurality of acceleration sensors are arranged at the aluminum pile, the sand and the model tunnel. According to the application, the structure is simple, the operability is strong, the result is intuitive, the cost is low, the vibration of the model tunnel in the centrifugal model test can be effectively reduced, and the vibration reduction and isolation measures in the tunnel with strict vibration requirements in the city can be guided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of damping devices, in particular to a method for damping and isolation of a model tunnel in a centrifugal model test. BACKGROUND

[0002] Urban rail transit lines such as subways and maglevs often pass through densely populated urban areas, bustling city areas with many buildings, scenic areas, and science and technology parks, etc. The upper part or adjacent area of the urban rail transit lines may be residential buildings, precision instrument rooms, ancient architectural complexes, and other areas sensitive to vibration and noise. To ensure that the major precision scientific facilities are properly put into use, it is necessary to reduce the vibration impact of the surrounding rail transit. SUMMARY

[0003] In view of the deficiencies in the prior art, the purpose of the present application is to provide a method for damping and isolation of a model tunnel in a centrifugal model test, which is simple in structure, strong in operability, intuitive in results, low in cost, can effectively reduce the vibration of the model tunnel in the centrifugal model test, and can provide guidance for damping and isolation measures in tunnels with strict vibration requirements in cities. In order to achieve the above-mentioned purposes and other advantages according to the present application, a method for damping and isolation of a model tunnel in a centrifugal model test is provided, comprising:

[0004] a model box, the inside of the model box and the bottom surface of the model box are both paved with damping materials; and

[0005] an aluminum pile and a model tunnel are placed in the sand soil, and the model tunnel is located on one side of the aluminum pile;

[0006] a vibration exciter is in contact with the aluminum pile, and a movable rod is fixedly connected to the vibration exciter;

[0007] a plurality of acceleration sensors are arranged at the aluminum pile, the sand soil, and the model tunnel.

[0008] Preferably, the damping material is an EPS foam board, and the thickness of the EPS foam board is 5 cm.

[0009] Preferably, the aluminum pile comprises a pile body, a bearing platform arranged on the pile body, and a pier top arranged on the bearing platform, the pile body and the bearing platform are arranged in the sand soil, the pier top is exposed above the sand soil, and a force applying rod of the vibration exciter is in contact with the pier top.

[0010] Preferably, a steel beam support is fixedly connected to the model box, a motor is fixedly connected to the steel beam support, and a movable rod is arranged on one side of the motor.

[0011] Preferably, the model tunnel comprises an outer aluminum alloy lining layer, an inner aluminum alloy lining layer, and a waterproof rubber arranged between the outer aluminum alloy lining layer and the inner aluminum alloy lining layer.

[0012] Preferably, the acquisition system is connected to the acceleration sensor signal, and the acquisition system is used to convert the analog signal of the acceleration sensor into a digital signal.

[0013] Compared with the prior art, the vibration reduction device has the advantages that the structure is clear, the operation is strong, the result is intuitive, the cost is low, the vibration of the model tunnel in the centrifugal model test can be effectively reduced, and the vibration reduction and isolation measures in the tunnel with strict vibration requirements in the city can be guided. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 A front view of the method for vibration reduction and isolation of a model tunnel in a centrifugal model test according to the present application;

[0015] Figure 2 A model box physical diagram of the method for vibration reduction and isolation of a model tunnel in a centrifugal model test according to the present application;

[0016] Figure 3 A JMJ-2 type electromagnetic exciter physical diagram of the method for vibration reduction and isolation of a model tunnel in a centrifugal model test according to the present application;

[0017] Figure 4 A model tunnel acceleration sensor layout diagram of the method for vibration reduction and isolation of a model tunnel in a centrifugal model test according to the present application;

[0018] Figure 5 A NI-9231 acquisition card physical diagram of the method for vibration reduction and isolation of a model tunnel in a centrifugal model test according to the present application;

[0019] Figure 6 A LabVIEW program block diagram interface diagram of the method for vibration reduction and isolation of a model tunnel in a centrifugal model test according to the present application;

[0020] Figure 7 A LabVIEW front panel interface diagram of the method for vibration reduction and isolation of a model tunnel in a centrifugal model test according to the present application;

[0021] Figure 8 A centrifuge laboratory vibration test related equipment layout physical diagram of the method for vibration reduction and isolation of a model tunnel in a centrifugal model test according to the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0023] With reference to Figures 1-8 A method for vibration isolation and reduction of a model tunnel in a centrifugal model test, comprising: a model box 1, the inner periphery and the bottom surface of the model box 1 are paved with damping materials 2, in order to reduce the reflection effect of the rigid boundary of the model box on the vibration wave, 5cm thick EPS foam plates are respectively paved on the four walls and the bottom of the model box to weaken the boundary reflection and external interference, the role of the EPS damping material has two points: first, in the centrifugal model test, the centrifuge itself and the external environment all have vibrations, which will greatly affect the test results, the EPS damping material can effectively isolate most of the environmental vibrations. Second, the centrifugal model test is a method for simulating actual working conditions, the actual working condition tunnel is buried in a semi-infinite soil body, in order to match the actual working conditions and prevent strong reflection of the vibration generated by the exciter at the boundary, the addition of the EPS damping material can effectively reduce the boundary reflection; the effective space size of the model box 1 is 900mmx700mmx700mm; the model box 1 is filled with sand 2; the sand 2 is placed with an aluminum pile 3 and a model tunnel 4, the model tunnel 4 is located on one side of the aluminum pile 3; the aluminum pile 3 is in contact with an exciter 5, the exciter 5 is a JMJ-2 type electromagnetic exciter. The exciter has a small volume, is convenient to arrange, can normally work in a high g value centrifugal field, and can provide a one-way excitation force of up to 20N, the vibration frequency range is up to 15kHz, the exciter 5 generates an excitation force, the excitation force is input from the top of the aluminum pile 3 and is transmitted into the sand 2 through the aluminum pile 3, the exciter 5 is fixed with a movable rod 6; a plurality of acceleration sensors are arranged at the aluminum pile 3, the sand 2 and the model tunnel 4, one acceleration sensor is arranged on the pile cap 32, that is, the acceleration of the aluminum pile is taken as the vibration input of the system, marked as a0, acceleration sensors a1 and a2 are arranged on the pile bottom plane of the aluminum pile 3 from near to far, an acceleration sensor a3 is arranged at the center position of the bottom plate, an acceleration sensor a5 is arranged at the center position of the top of the model tunnel 4, an acceleration sensor a4 is arranged at the center position of the top of the model tunnel 4, and an acceleration sensor a6 is arranged directly below the model tunnel 4, as shown in Figure 1 、 Figure 4 The purpose is to observe the vibration isolation and reduction effect of filling 1mm thick rubber between the double-layer lining and the vibration attenuation law in the soil layer.

[0024] The model box 1 is fixed with a steel beam support 7, the steel beam support 7 is fixed with a motor 8, one side of the motor 8 is provided with a movable rod 6, the aluminum pile 3 includes a pile body 31, a bearing platform 32 provided on the pile body and a pier top provided on the bearing platform 32, and the pile body 31 and the bearing platform 32 are arranged in the sand 2, the pier top is exposed on the sand 2, the force applying rod of the exciter 5 is in contact with the pier top, in order to prevent the force applying rod end of the exciter 5 from being separated from the top of the aluminum pile 3, a motor 8 capable of moving up and down in the centrifugal field is introduced into the system, the motor 8 is fixed on the steel beam support 7 through bolts, and the exciter 5 is fixed to the movable rod end of the motor 8, so that the force applying rod end of the exciter 5 can be in contact with the top of the aluminum pile 3.

[0025] Further, the model tunnel 4 includes an outer aluminum alloy lining layer 41, an inner aluminum alloy lining layer 42 and waterproof rubber arranged between the outer aluminum alloy lining layer 41 and the inner aluminum alloy lining layer 42.

[0026] Further, the system further includes a collection system connected with the acceleration sensor signal, and the collection system is used for converting the analog signal of the acceleration sensor into a digital signal, and the data collection system needs at least 7 measurement channels. The vibration frequency range of the measured input and output is 0-8,000 Hz, according to the Nyquist sampling theorem, in the process of converting the analog signal into the digital signal, that is, in the sampling process, if the digital signal after sampling can completely retain the information in the original signal, the sampling frequency must be set to be more than 2 times of the highest frequency in the signal. In actual application, the sampling frequency is generally set to be 2.56-4 times of the highest frequency of the signal. In the test, the highest frequency of the signal is 8,000 Hz, and the sampling frequency is set to be 2.56 times of the frequency, that is, 20,480 Hz.

[0027] The NI-9231 collection card of the United States National Instrument (National Instruments) is adopted, see Figure 5This data acquisition card can provide up to 8 channels of simultaneous acquisition, with a maximum sampling rate of 51.2 kHz per channel and a quantization accuracy of 24 bits. Normal operation of the NI-9231 data acquisition card requires installation on the matching cDAQ-9174 chassis, which transmits data to the PC via a USB 2.0 port. To avoid additional electromagnetic interference from cable extensions, the cDAQ-9174 chassis is placed in the centrifuge laboratory and connected to a small PC installed on the centrifuge via a USB 2.0 data cable. The small PC can be remotely controlled from the laboratory computer. Reading and saving vibration data requires the accompanying software LabVIEW Full. LabVIEW, short for Laboratory Virtual Instrument Engineering Platform, is a graphical programming platform developed by National Instruments that intuitively displays various aspects of the application, including hardware configuration, measurement data, and debugging. Data acquired by the data acquisition card can be saved to a local PC file via LabVIEW, and this data can be further analyzed using MATLAB.

[0028] Workflow: 1) Empty model box 1, keep the foam boards on the four walls and bottom, and weigh them.

[0029] 2) Use a sand hopper to evenly pour dry sand into model box 1.

[0030] 3) When the height of the backfilled sand reaches the design height of model tunnel 4, use a level to measure the levelness of the upper surface of the soil layer to ensure that the tunnel is placed horizontally. Then, place model tunnel 4 in the predetermined position and continue to add sand.

[0031] 4) When the height of the backfilled sand reaches the design height of the accelerometer, use a level to measure the levelness of the upper surface of the soil layer to ensure that the accelerometer is placed horizontally.

[0032] 5) Place the double-layer lining model tunnel 4 of aluminum pile 3 and aluminum alloy base plate into the predetermined position in the model box 1, and fill the gap between the double lining with 1mm thick rubber, and continue to add sand until the sand is filled to the predetermined height. During the sand filling process, ensure that the aluminum pile 3 is vertical.

[0033] 6) Weigh the model box 1 again and install the steel beam support 7, motor 8 and vibrator 5 in the corresponding positions.

[0034] 7) Hoist model box 1 into the centrifuge basket and connect the power supply and data cable.

[0035] The centrifuge was turned on and set to an 80g centrifugal field environment for the experiment. This means that when the centrifuge speed was 154.4 r / min, the acceleration at 1 / 3 depth of the model was 80g. Analysis of the sensor data revealed the attenuation of vibration inside the model tunnel after the addition of this vibration reduction and isolation device. This attenuation pattern can provide a basis for vibration reduction and isolation measures in tunnels during practical engineering projects.

[0036] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention, and applications, modifications and variations thereof will be obvious to those skilled in the art.

[0037] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for vibration isolation of a model tunnel in a centrifuge model test, characterized by, The damping and isolation device applied to the method comprises a model box (1), the inner periphery and the bottom surface of which are paved with damping materials (2); and the model box (1) is filled with sand (2); The sand (2) is placed with an aluminum pile (3) and a model tunnel (4), and the model tunnel (4) is located on one side of the aluminum pile (3); The aluminum pile (3) is provided with a vibration exciter (5) in contact, and the vibration exciter (5) is fixedly connected with a movable rod (6); The aluminum pile (3), the sand (2) and the model tunnel (4) are provided with a plurality of acceleration sensors. The method comprises the following steps: 1) emptying the model box (1), retaining the foam board of the four walls and the bottom, and weighing; 2) evenly dropping dry sand into the model box (1) with a sand bucket; 3) when the filled sand height reaches the design height of the model tunnel (4), measuring the levelness of the upper surface of the soil layer with a level meter to ensure that the tunnel placement position is horizontal, then placing the model tunnel (4) into the predetermined position, and continuing to add sand; 4) when the filled sand height reaches the design height of the acceleration sensor, measuring the levelness of the upper surface of the soil layer with a level meter to ensure that the acceleration sensor placement position is horizontal; 5) placing the aluminum pile (3) and the double-layer lining model tunnel (4) of the aluminum alloy bottom plate into the model box (1) in the predetermined position, filling the double-layer lining with 1mm thick rubber, continuing to add sand until the sand is filled to the predetermined height, and ensuring that the aluminum pile (3) is vertical during the sand filling process; 6) weighing the model box (1) again, and installing the steel beam support (7), the motor (8) and the vibration exciter (5) at the corresponding positions; 7) hoisting the model box (1) into the centrifuge basket, and connecting the power supply and the data line.

2. A method for reducing and isolating vibration of a model tunnel in a centrifugal model test according to claim 1, characterized in that, The damping material (2) is an EPS foam board, and the thickness of the EPS foam board is 5cm.

3. A method for reducing and isolating vibration of a model tunnel in a centrifugal model test according to claim 1, wherein The aluminum pile (3) comprises a pile body (31), a bearing platform (32) arranged on the pile body (31) and a pier top arranged on the bearing platform (32), the pile body (31) and the bearing platform (32) are arranged in the sand (2), the pier top is exposed above the sand (2), and the force applying rod of the vibration exciter (5) is in contact with the pier top.

4. A method for reducing and isolating vibration of a model tunnel in a centrifugal model test according to claim 3, wherein The model box (1) is fixedly connected with a steel beam support (7), the steel beam support (7) is fixedly connected with a motor (8), and one side of the motor (8) is provided with a movable rod (6).

5. A method for reducing and isolating vibration of a model tunnel in a centrifugal model test according to claim 4, wherein The model tunnel (4) comprises an external aluminum alloy lining layer (41), an internal aluminum alloy lining layer (42) and rubber arranged between the external aluminum alloy lining layer (41) and the internal aluminum alloy lining layer (42).

6. A method for reducing and isolating vibration of a model tunnel in a centrifugal model test according to claim 1, wherein Further comprising a collection system connected with the acceleration sensor signal, and the collection system is used for converting the analog signal of the acceleration sensor into a digital signal.

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