A damping ratio measuring device and signal processing method suitable for consolidation equipment

Abstract

The present invention discloses a damping ratio measuring device and signal processing method suitable for consolidation equipment, including a bracket, a consolidation pressurizing device and a sleeve; the consolidation pressurizing device is arranged at the top of the bracket, the output direction of the consolidation pressurizing device is directly downward, a pressurizing piston is connected to the bottom of the consolidation pressurizing device, and a displacement sensor is arranged on the pressurizing piston; the sleeve is arranged directly below the consolidation pressurizing device, the pressurizing piston extends from the top of the sleeve, the diameter of the pressurizing piston is the same as the inner diameter of the sleeve, the bottom of the sleeve is sealed and connected with a support plate, and two bending element sensors are respectively arranged on the top of the support plate and the bottom of the pressurizing piston. The inherent arrangement mode of the signal transmitting and receiving finite element sensors is changed to reduce the damping ratio measurement error and ensure the accuracy and reliability of the damping ratio measurement of the soil material.

Description

Technical Field

[0001] The invention belongs to the field of geotechnical engineering detection and relates to a damping ratio measuring device suitable for consolidation equipment and a signal processing method. Background Art

[0002] Damping ratio is a basic parameter for geotechnical engineering dynamic analysis. Damping ratio refers to the energy loss of the signal when the energy is transmitted inside the soil or the energy dissipation from the intrinsic attenuation of the soil itself, such as the friction loss between soil particles. In geotechnical engineering research, this energy loss is usually quantified by the damping ratio D, but there is often uncertainty and inaccuracy in the measurement of damping ratio in consolidation tests, especially in small strain conditions. For example, in small strains (<10 -5 ) condition, the measured damping ratio of fine sand is 0.20% to 5.00%. The reason for the large deviation is that the damping ratio is actually a very small quantity, and any test deviation can easily affect the measured value. In this case, it is a challenge to maintain the accuracy of damping ratio measurement during soil consolidation.

[0003] Material damping is a major form of damping and one of the basic properties of materials. Its measurement accuracy has important research and application value. In soil damping tests, various factors such as changes in the test environment and the damping characteristics of the soil being tested itself cause various measurement deviations such as unstable damping test results and poor accuracy. At present, the most commonly used damping test method is the traditional damping test method, which calculates its damping characteristics by measuring the resonant vibration response curve of the object being tested. The traditional test method has the advantages of clear and intuitive test principles and simple and clear operation steps. However, there are two obvious defects in the measurement process of the traditional method: (1) The bending element is used as a sensor for damping measurement, in which the receiver element is only a signal receiving device. The received signal is easily interfered by noise signals. These signals are often captured by the receiving signal source together with the main signal, thereby affecting the measurement of the damping ratio. Therefore, the received signal is often affected by the inherent characteristics of the element, resulting in a large error in the test results when the damping is tested. A slight change in the test environment will cause a large error in the test results. (2) Since the distance between the signal transmitter and the signal receiver is relatively close, there will be an obvious near-field effect during the signal transmission process, which will affect the accuracy of the received signal and thus the correctness of the test results. It can be found that the measurement error in the damping ratio measurement process is a key factor in determining the accuracy of the measurement data. However, due to uncontrollable factors such as test equipment and test sites, test errors are inevitable. Therefore, minimizing the measurement error as much as possible without affecting the accuracy of the test has become a key issue in the measurement of soil damping ratio. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, provide a damping ratio measurement device and signal processing method suitable for consolidation equipment, change the inherent arrangement mode of signal transmitting and receiving finite element sensors, reduce the damping ratio measurement error, and ensure the accuracy and reliability of the damping ratio measurement of soil materials.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A damping ratio measuring device suitable for consolidation equipment, comprising a bracket, a consolidation pressurizing device and a sleeve;

[0007] The consolidation pressurizing device is arranged at the top of the bracket, and the output direction of the consolidation pressurizing device is facing directly downward. The bottom of the consolidation pressurizing device is connected with a pressurizing piston, and a displacement sensor is arranged on the pressurizing piston; the sleeve is arranged directly below the consolidation pressurizing device, and the pressurizing piston extends into from the top of the sleeve. The diameter of the pressurizing piston is the same as the inner diameter of the sleeve. The bottom of the sleeve is sealed and connected with a support plate, and two bending element sensors are respectively arranged on the top of the support plate and the bottom of the pressurizing piston.

[0008] Preferably, a pressure sensor is disposed on both sides of the sleeve and on the bottom of the support plate, and the pressure sensor at the bottom of the support plate is located at the center of the support plate.

[0009] Preferably, the bending element sensor is arranged close to the axis of the sleeve.

[0010] Preferably, the sleeve and the support plate are connected by an O-ring.

[0011] Preferably, two support blocks are arranged at the bottom of the support plate, and the support blocks are arranged eccentrically with respect to the support plate.

[0012] Preferably, the displacement sensor is an LVDT displacement sensor, the bottom of the consolidation pressurizing device is connected to the top of the LVDT displacement sensor, and the bottom of the LVDT displacement sensor is connected to the top of the pressurizing piston.

[0013] Preferably, the bracket includes a top plate, a bottom plate and a connecting rod, the connecting rod connects the top plate and the bottom plate in parallel, and the consolidation pressure device and the sleeve are arranged between the top plate and the bottom plate.

[0014] Furthermore, a latex membrane is arranged between the connecting rod and the bottom plate.

[0015] Furthermore, the connecting rod adopts a lead screw, and the lead screw is threadedly connected to the top plate.

[0016] A damping ratio signal processing method for consolidation equipment based on any one of the above-mentioned devices, measuring the material damping ratio by a spectrum ratio method:

[0017]

[0018] Among them, U(f) is the amplitude of the signal at the displacement r, D is the damping ratio, β is the geometric diffusion constant, T is the transmission coefficient, V is the wave velocity, and f is the frequency;

[0019] The amplitude of the propagating wave, U(f), is represented by the output voltage produced by the receiving bending element, Y(f):

[0020] Y(f)=H R (f)U(f) (2)

[0021] HR(f) is the bend element sensor transfer function;

[0022] Perform two signal conduction processes, positive and negative, to offset the conduction function;

[0023] When doing the forward pass:

[0024]

[0025] When passing in reverse:

[0026]

[0027] Substituting formula (2), (3), (4) into formula (1), the conduction functions of formula (3) (4) cancel each other out and the result is:

[0028]

[0029] Where T a , T b is the transmission coefficient of the two-wave transmission. Y is the output voltage of the bending element sensor.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention arranges two signal sensors at the bottom and top of the consolidation instrument respectively. The sensor at the bottom serves as a signal transmitting source and a receiving source, and the sensor at the top serves as a signal receiving and transferring device, thereby solving the near-field effect generated when receiving the signal. The two sensors at the bottom serve as signal transmitting sources respectively, and transmit the signal twice in the positive and negative directions. During the signal processing, the positive and negative signals are offset and processed, and the interference signal is discharged, thereby achieving the accuracy of the damping ratio measurement in the reconsolidation process.

[0032] Furthermore, the bending element sensor is placed in the middle of the top plate of the oedometer to minimize the influence of interference signals from the boundary and periphery of the oedometer.

[0033] Furthermore, the two sensor brackets arranged on the same side are not connected to each other, and two latex films are placed under each bracket to cut off all signal interference from the connection frame and the bottom of the container. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the present invention;

[0035] Figure 2 It is a schematic diagram of the positive and negative signal conduction processes of the present invention.

[0036] Among them: 1-top plate; 2-screw rod; 3-bottom plate; 4-LVDT displacement sensor; 5-consolidation pressurization device; 6-fixing bolt; 7-pressurization piston; 8-vertical rod; 9-fixing disc; 10-sleeve; 11-connecting rod; 12-support block; 13-pressure sensor; 14-bending element sensor; 15-O-ring; 16-insulating bracket; 17-support plate 17. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0038] like Figure 1 As shown, the damping ratio measuring device suitable for consolidation equipment according to the present invention includes a bracket, a consolidation pressurizing device 5 and a sleeve 10.

[0039] The bracket includes a top plate 1, a connecting rod and a bottom plate 3 arranged in sequence from top to bottom. The top plate 1 and the bottom plate 3 are parallel to the horizontal plane and fixed by the connecting rod. The sleeve 10 is arranged between the top plate 1 and the bottom plate 3; the top plate 1 and the bottom plate 3 are fixed to the connecting rods on both sides by fixing bolts 6. The preferred connecting rod in this embodiment is a screw rod 2.

[0040] A consolidation pressurizing device 5 is fixed at the bottom of the top plate 1 for applying normal pressure. The consolidation pressurizing device 5 is connected to the vertical rod 8 and the pressurizing piston 7 through a connecting rod 11. The diameter of the pressurizing piston 7 is the same as the inner diameter of the sleeve 10.

[0041] The free end of the armature of the LVDT displacement sensor 4 is fixed to the top of the piston 7 , and the measuring range of the LVDT displacement sensor 4 is the same as the maximum depth of the sleeve 10 .

[0042] Two support blocks 12 are arranged on the bottom plate 3, and a support plate 17 is arranged on the top surface. The support plate 17 has the same inner diameter as the sleeve 10. The bottom of the sleeve 10 is sleeved on the outside of the support block 12, and the bottom of the sleeve 10 is suspended. When a soil sample is placed inside the sleeve 10, a pressurizing piston 7 is placed above the soil sample, and the piston diameter is the same as the inner diameter of the sleeve 10.

[0043] There are threaded through holes on both sides of the top plate 1, and screw holes are opened at corresponding positions of the bottom plate 3. Two vertical screw rods 2 pass through the holes respectively, and the bottom plate 3 and the top plate 1 are fixedly connected by tightening nuts; the top plate 1 and the bottom plate 3 are made of 2-3 cm thick steel plates to ensure the strength and rigidity required for the test; the threaded screw rod 2 is made of steel screw rod, and its length should be left with surplus to facilitate adjustment of the distance between the top plate 1 and the bottom plate 3.

[0044] The sleeve 10 is surrounded by a steel plate with a thickness of 3 cm to provide sufficient vertical support force to prevent radial deformation during the consolidation process; the columnar sleeve 10 is not fixed to the top plate 1, and two detachable support blocks 12 are fixed to the bottom of the sleeve 10. The inner wall of the sleeve 10 is as smooth as possible to reduce the generation of greater side wall friction.

[0045] The bottom of the sleeve 10 and the top of the bottom plate 3 are both provided with U-shaped grooves for accommodating O-rings 15, so that the soil sample consolidation area is in a sealed state to prevent the soil sample from being squeezed out during the consolidation process.

[0046] A displacement sensor is fixed at the bottom of the top plate 1. The displacement sensor is located directly above the pressurizing piston 7, with the sensing head facing the pressurizing piston. This embodiment preferably uses an LVDT displacement sensor 4, the free end of the armature of the LVDT displacement sensor 4 is fixed to the pressurizing piston 7 to measure the consolidation settlement deformation of the soil sample.

[0047] Three pressure sensors 13 are installed on the left and right side walls of the sleeve 10 and the bottom of the support plate 17, specifically installed on the outer wall or embedded in the side wall, for collecting the pressure changes of the inner wall of the sleeve 10 during the consolidation test.

[0048] Two bending element sensors 14 are arranged on the top of the support plate 17 and the bottom of the pressurizing piston 7 respectively, for transmitting and receiving signal waves and measuring the damping characteristics of the test material. The bending element sensor 14 is connected to the device through an insulating bracket 16 to isolate external signal interference.

[0049] When using this device to consolidate soil samples and measure damping, first connect the top plate 1, the bottom plate 3 and the two lead screws to assemble a support frame, and fix the LVDT displacement sensor 4 on the top plate 1 with bolts, fix the bracket 12 on the bottom plate 3, place the sleeve 10 on the bracket 12, place the O-ring 15 on the inside of the sleeve 10, fix two isolation brackets 16 on the bottom plate of the sleeve 10 and the bottom plate of the pressurizing piston 7, and fix the isolation brackets 16 to the sleeve wall 3cm apart. Fix the bending element sensor 14 on the isolation bracket 16, connect the pressure sensor 13 and the signal collector to the computer, open the data acquisition software, set the pressure parameters, and prepare for data acquisition. Then start sample preparation, place the soil samples in three layers, and compact them layer by layer. After the sample preparation is completed, the permeable stone plate, O-ring 15, piston 7 and consolidation pressurizing device 5 are placed on the top of the soil sample from bottom to top, the free end of the armature of the LVDT displacement sensor 4 is fixed to the top of the pressurizing piston 7, and the bending element sensor 14 is connected to the sine pulse transmitter and the signal receiver respectively to generate and collect electrical signals. Consolidation begins. During the consolidation and settlement process, the floating pressurizing piston 7 moves accordingly, greatly reducing the relative displacement between the soil sample and the sleeve 10, and reducing the side wall friction of the soil sample.

[0050] Peripheral electronic equipment, the pulse signal is transmitted by a single sinusoidal pulse transmitter, amplified by a power amplifier, and the received signal is enhanced by a filter and an amplifier. All signals are recorded by an oscilloscope with the same sampling frequency to ensure the stability of signal transmission during the entire test process.

[0051] The present invention also discloses a signal processing method in a damping ratio measurement test, and uses a spectrum ratio method to measure the soil damping ratio. During the signal transmission process, the damping characteristics exhibited by the material itself are different due to different initial signal intensities. When the initial amplitude is small, the damping is usually linear. At this time, the damping ratio D is usually determined by the signal wave frequency and has nothing to do with the displacement; when the amplitude is in the middle and high ranges, the damping gradually becomes nonlinear. The relevant damping ratio D is usually independent of the frequency and is related to the conduction displacement and friction. Based on the above three factors that cause signal conduction attenuation, the amplitude attenuation function is summarized:

[0052]

[0053] Where U(f) is the amplitude of the signal at a displacement of r; β is the geometric diffusion constant, which is 0 when the signal wave propagates in a plane, 1.0 when it propagates in a sphere, and 0.5 when it propagates in a cylinder; T is the transmission coefficient; α represents the attenuation coefficient related to the damping ratio D;

[0054]

[0055] Where λ is the wavelength; V is the wave speed; f is the frequency

[0056] Substitute the formula into the equation, take the natural logarithm of both sides, and sort out each term to get;

[0057]

[0058] The damping ratio D can be simply obtained from the slope of the ratio graph of the spectrum ratio ln[U1(f) / U2(f)] and the frequency f. This is the measurement of the material damping ratio using the spectrum ratio method.

[0059] On this basis, the present invention further optimizes the above signal processing method by rearranging the oedometer damping sensor. The above signal processing method is based on the assumption that the two signal receiving sensors process the received signals in exactly the same way. However, even if two sensors of the same model have different signal processing processes, they will produce inherent deviations in the measurement of the damping ratio. Further optimization is performed based on this.

[0060] In the bender test, the amplitude of the propagating wave U(f) is represented by the output voltage generated by the receiving bender Y(f). R (f), these two parameters can be related to each other:

[0061] Y(f)=H R (f)U(f)

[0062] Because different sensors process the received signals differently, that is, the transfer function H R (f) are different, so the present invention performs two signal transduction processes, forward and reverse, such as Figure 2 As shown, the conduction functions are cancelled.

[0063] When doing the forward pass:

[0064]

[0065] When passing in reverse:

[0066]

[0067] Substituting into , the conduction functions cancel each other out and we get:

[0068]

[0069] Where T a , T b is the transmission coefficient of the twice-transmitted wave. Y is the output voltage of the bending element sensor 14. Through the optimization process, the damping ratio D is still obtained by the slope of the above-mentioned spectrum ratio and frequency graph, without relying on the frequency transfer function, that is, it is not affected by the inherent differences of the sensor. At the same time, this method can also eliminate the noise influence generated by peripheral electronic devices.

[0070] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A damping ratio measuring device suitable for consolidation equipment, characterized in that: It comprises a bracket, a consolidation and pressurizing device (5) and a sleeve (10); The consolidation pressurizing device (5) is arranged at the top of the bracket, the output direction of the consolidation pressurizing device (5) is facing directly downward, the bottom of the consolidation pressurizing device (5) is connected to a pressurizing piston (7), and a displacement sensor is arranged on the pressurizing piston (7); the sleeve (10) is arranged directly below the consolidation pressurizing device (5), the pressurizing piston (7) extends from the top of the sleeve (10), the diameter of the pressurizing piston (7) is the same as the inner diameter of the sleeve (10), the bottom of the sleeve (10) is sealedly connected to a support plate (17), and two bending element sensors (14) are respectively arranged on the top of the support plate (17) and the bottom of the pressurizing piston (7); A pressure sensor (13) is provided on both sides of the sleeve (10) and at the bottom of the support plate (17); the pressure sensor (13) at the bottom of the support plate (17) is located at the center of the support plate (17); The bending element sensor (14) is arranged close to the axis of the sleeve (10).

2. The damping ratio measuring device suitable for consolidation equipment according to claim 1, characterized in that: The sleeve (10) and the support plate (17) are connected by an O-ring (15).

3. The damping ratio measuring device suitable for consolidation equipment according to claim 1, characterized in that: Two support blocks (12) are arranged at the bottom of the support plate (17), and the support blocks (12) are arranged eccentrically with respect to the support plate (17).

4. The damping ratio measuring device suitable for consolidation equipment according to claim 1, characterized in that: The displacement sensor adopts an LVDT displacement sensor (4); the bottom of the consolidation pressurizing device (5) is connected to the top of the LVDT displacement sensor (4); and the bottom of the LVDT displacement sensor (4) is connected to the top of the pressurizing piston (7).

5. The damping ratio measuring device suitable for consolidation equipment according to claim 1, characterized in that: The bracket comprises a top plate (1), a bottom plate (3) and a connecting rod, wherein the connecting rod connects the top plate (1) and the bottom plate (3) in parallel, and the consolidation pressure device (5) and the sleeve (10) are arranged between the top plate (1) and the bottom plate (3).

6. The damping ratio measuring device suitable for consolidation equipment according to claim 5, characterized in that: A latex film is provided between the connecting rod and the bottom plate (3).

7. The damping ratio measuring device suitable for consolidation equipment according to claim 5, characterized in that: The connecting rod adopts a lead screw (2), and the lead screw (2) is threadedly connected to the top plate (1).

8. A damping ratio signal processing method for consolidation equipment based on the device according to any one of claims 1 to 7, characterized in that: Measure the material damping ratio using the spectrum ratio method: （1） Among them, U(f) is the amplitude of the signal at the displacement r, D is the damping ratio, β is the geometric diffusion constant, T is the transmission coefficient, V is the wave velocity, and f is the frequency; The amplitude of the propagating wave, U(f), is represented by the output voltage produced by the receiving bending element, Y(f): （2） HR(f) is the bend element sensor transfer function; Perform two signal conduction processes, positive and negative, to offset the conduction function; When doing the forward pass: （3） When passing in reverse: （4） Substituting formula (2), (3) and (4) into formula (1), the conduction functions of formula (3) and (4) cancel each other out and the result is: Where T a 、T b is the transmission coefficient of the two-wave transmission, and Y is the output voltage of the bending element sensor.

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