Method for monitoring structural damage of stone retaining wall

Abstract

The invention discloses a method for monitoring structural damage of a stone-laying retaining wall. The method comprises the following steps: exciting the stone-laying retaining wall regularly and acquiring signals; wavelet packet decomposition is carried out on the collected signals; performing wavelet packet frequency band energy spectrum analysis on the decomposed signal, establishing an energy ratio spectrum, creating a characteristic frequency band vector spectrum, and constructing a wavelet packet damage characteristic vector spectrum; according to the wavelet packet damage feature vector spectrum, a monitoring index is defined; and internal relations among the monitoring indexes, the soil pressure and the retaining wall stability coefficient are analyzed, and the stability state of the stone-laying retaining wall is determined. According to the method, the retaining wall stability is monitored through monitoring indexes for the first time, and the method has the characteristics of simplicity, convenience, real-time monitoring, rapidness, high efficiency, modern intelligence and the like; the internal relation among the monitoring index, the soil pressure and the retaining wall stability coefficient is analyzed, when the monitoring index reaches a threshold value, the retaining wall enters a critical stable state, and therefore the damage condition of the stone-laying retaining wall can be judged through the monitoring index.

Description

Technical Field

[0001] The invention belongs to a damage monitoring method, in particular to a method for monitoring damage of a stone retaining wall structure. Background Art

[0002] Retaining walls are mainly used to support roadbed fill and prevent deformation and instability. They have the advantages of simple structure, convenient construction, small footprint and low cost, and are widely used in highway and water conservancy projects. However, large-scale natural disasters in recent years have caused damage inside retaining walls, and excessive damage may lead to their destruction. Therefore, it is necessary to monitor the damage of retaining wall structures regularly or in real time so that damage can be detected as early as possible and handled in a timely manner.

[0003] Existing methods for damage monitoring of retaining wall structures usually use traditional methods such as drilling or slotting for sampling and verification. These traditional methods generally have the disadvantages of low efficiency, incompleteness, destruction of the integrity of the structure itself, and no quantitative indicators. They belong to destructive test damage monitoring technology. Summary of the invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a simple, convenient, real-time, fast and efficient method for monitoring damage of masonry retaining wall structures.

[0005] Technical solution: A method for monitoring damage of a stone retaining wall structure according to the present invention comprises the following steps:

[0006] S1, regularly stimulate the stone retaining wall and collect signals;

[0007] S2, performing wavelet packet decomposition on the collected signal;

[0008] S3, performing wavelet packet frequency band energy spectrum analysis on the decomposed signal, establishing an energy ratio spectrum, creating a characteristic frequency band vector spectrum and constructing a wavelet packet damage characteristic vector spectrum;

[0009] S4. Define monitoring indicators based on the wavelet packet damage feature vector spectrum;

[0010] S5. Analyze the intrinsic relationship between monitoring indicators, soil pressure and retaining wall stability coefficient to determine the stability status of the stone retaining wall.

[0011] Furthermore, in step S1, the masonry retaining wall is regularly stimulated by a force hammer and signals are collected. Before the test, steel brackets are arranged in advance at various measuring points of the masonry retaining wall, and the horizontal acceleration sensor is horizontally placed on the steel bracket. After the force hammer is excited, the response generated by the masonry retaining wall is transmitted to the signal acquisition device through the horizontal acceleration sensor, and then transmitted to the computer through the wireless gateway.

[0012] Furthermore, in step S2, the wavelet packet decomposition specifically includes: selecting an appropriate scale to perform wavelet packet decomposition and reconstruction on the masonry retaining wall signals measured at each period to obtain the energy ratio of each frequency band, that is, the constructed characteristic frequency band vector spectrum must be within 10th order to facilitate subsequent calculations.

[0013] Furthermore, step S3 is specifically as follows: sorting each frequency band from high to low according to the energy ratio, establishing an energy ratio spectrum, merging the last 5% of the energy ratio frequency bands into a remaining frequency band, and forming a characteristic frequency band vector spectrum with the first 95% of the frequency bands, and on the basis of the characteristic frequency band vector spectrum, calculating the energy ratio deviation on the characteristic frequency band before and after the retaining wall, and constructing a wavelet packet damage characteristic vector spectrum.

[0014] Furthermore, the energy ratio deviation is calculated as: DI k =|I k u -I k d |, where I k u is the energy ratio of the kth characteristic frequency band in the initial test, I k d is the energy ratio of the kth characteristic frequency band in the subsequent test, DI k is the energy ratio deviation.

[0015] Furthermore, in step S4, the monitoring index is the energy ratio variation coefficient, and the calculation formula is:

[0016]

[0017] Among them, IVC is the energy ratio variation coefficient, DI k is the energy ratio deviation, I k u is the energy ratio of the kth characteristic frequency band in the initial test.

[0018] Furthermore, when the energy ratio variation coefficient is 0, it indicates that the masonry retaining wall has no damage; when the energy ratio variation coefficient is not 0, damage exists in the masonry retaining wall; the larger the energy ratio variation coefficient value, the more serious the damage in the structure.

[0019] Furthermore, in step S5, the retaining wall stability coefficient includes the anti-sliding stability coefficient K s and anti-overturning stability coefficient K t , the calculation formula of anti-slip stability coefficient is Anti-overturning stability coefficient K t The calculation formula is, Among them, P A is the resultant earth pressure acting on the back of the wall, A is the distance from the point of action of the resultant force to the toe of the wall, P BThe resultant force of the earth pressure in front of the wall, B is the distance from the point of action of the resultant force to the toe of the wall.

[0020] Further, in step S5, the stability states of the stone retaining wall include stable, basically stable and unstable; when the anti-slip stability coefficient is greater than 1.3 and the anti-overturning stability coefficient is greater than 1.6, it is stable; when 1.0≤anti-slip stability coefficient<1.3 or 1.0≤anti-overturning stability coefficient<1.6, it is basically stable; when the anti-slip stability coefficient is less than 1.0 or the anti-overturning stability coefficient is less than 1.0, it is unstable.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0022] 1. It is the first time to propose monitoring the stability of retaining walls through monitoring indicators, which has the characteristics of simplicity, convenience, real-time monitoring, rapidity, efficiency, and modern intelligence;

[0023] 2. Focusing on the masonry retaining wall that lacks integrity, the inherent relationship among monitoring indicators, earth pressure and retaining wall stability coefficient is analyzed. When the monitoring indicators reach the limit value, the retaining wall enters a critical stability state. Therefore, the damage of the masonry retaining wall can be judged through the monitoring indicators.

[0024] 3. Although retaining wall structures are diverse, their simplified mechanical models, finite element models and monitoring coefficient calculation formulas are not exactly the same. They can be widely promoted and applied to damage monitoring of various types of rock and soil retaining structures, and have great application space in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the present invention;

[0026] Figure 2 is a flow chart of the present invention;

[0027] Figure 3 It is the wavelet packet characteristic frequency band vector spectrum of the masonry retaining wall structure under the initial test of the present invention;

[0028] Figure 4 It is the wavelet packet characteristic frequency band vector spectrum of the masonry retaining wall structure under subsequent tests of the present invention;

[0029] Figure 5 It is the wavelet packet damage feature vector spectrum of the present invention;

[0030] Figure 6 It is the damage monitoring principle diagram of the present invention;

[0031] Figure 7 It is a relationship diagram between the monitoring index and the structural stability of the present invention. DETAILED DESCRIPTION

[0032] like Figure 1There are measuring points, horizontal acceleration sensors 2 and force hammer excitation points 3 in the masonry retaining wall 1. The horizontal acceleration sensors 2 are arranged in order at the corresponding measuring points and try to cover the entire test wall surface. The force hammer excitation point 3 should be selected at the center of the retaining wall measuring point to ensure that the distance of the excitation signal transmitted to each measuring point is basically the same, so as to control the sensitivity of each measuring point to damage. Behind the masonry retaining wall 1 is the soil behind the wall.

[0033] like Figure 2 A method for monitoring structural damage of a stone retaining wall 1 comprises the following steps:

[0034] S1. Regularly stimulate the masonry retaining wall 1 by a force hammer and collect signals.

[0035] S11. The vibration test under hammer pulse excitation is to use the vibration caused by the force hammer as the excitation, and take factors such as time, temperature, and rainfall into consideration. The hammer pulse excitation vibration test is performed on the masonry retaining wall 1. The device for applying the pulse excitation is the JMF400uu series impact hammer. When the force hammer is connected to the JM3841 dynamic and static signal test and analysis system, the hammer pulse signal can be recorded synchronously.

[0036] S12. The vibration test will be affected by the position of the hammer point. The sensitivity of the damage characteristic vector spectrum of different measuring points to damage is not exactly the same. The measuring point far away from the pulse excitation point is relatively weak in sensitivity to damage, while the measuring point close to the excitation point has good damage sensitivity. Therefore, the force hammer excitation point should be selected at the center of the measuring point layout to ensure that the distance from the excitation signal to each measuring point is basically the same, so as to control the consistency of the sensitivity of each measuring point to damage.

[0037] S13. Except for the reserved force hammer excitation point 3 area, 15 horizontal acceleration sensors 2 are arranged at the other positions of the masonry retaining wall 1. The model is V003 electromagnetic velocity sensor (sampling frequency 0.17-100Hz). Before placing the horizontal acceleration sensor 2, it is necessary to install an L-shaped steel mounting bracket at the corresponding measuring point. The bracket and the masonry retaining wall 1 can be fixed by expansion screws. The contact surface between the bracket and the wall can be bonded with AB glue to ensure that the horizontal acceleration sensor 2 can be placed horizontally on the bracket.

[0038] S14, the collected signals are transmitted to the computer through the dynamic and static signal test and analysis system and the wireless gateway. The signal acquisition system is the JM3841 dynamic and static signal test and analysis system, and the sampling frequency is set to 500Hz. The vibration test system transmits the recorded signals to the computer through the gateway for processing. The gateway is the JM1803 USB wireless dynamic gateway.

[0039] S2. Performing wavelet packet decomposition on the collected signals by computer, which specifically includes: performing wavelet packet decomposition on the signals of the initial masonry retaining wall 1 and the subsequent test masonry retaining wall 1 to obtain the energy ratio of each frequency band, and sorting the energy ratios from high to low to form a wavelet packet frequency band energy ratio spectrum.

[0040] S3. Perform wavelet packet band energy spectrum analysis on the decomposed signal, establish an energy ratio spectrum, create a characteristic frequency band vector spectrum and construct a wavelet packet damage characteristic vector spectrum.

[0041] S31. Due to the influence of observation noise, not all frequency bands can reflect the damage information of masonry retaining wall 1. Therefore, based on the wavelet packet frequency band energy ratio spectrum, in order to effectively reflect the change of energy ratio in the frequency band, a threshold ε is introduced. o (take 0.85~0.95), and exceed the threshold ε o The remaining frequency bands are combined into a new frequency band, called the remaining frequency band.

[0042] S32. If a three-layer wavelet packet transform is performed on the virtual impulse response function signal of an intact retaining wall, 2 3 =8 sub-bands. Figure 3 This is the characteristic frequency band vector spectrum of the masonry retaining wall 1 structure tested for the first time. Figure 4 Characteristic frequency band vector spectrum for subsequent testing of retaining wall structure.

[0043] S33. When the retaining wall structure is damaged, the energy ratio of the same characteristic frequency band before and after the damage will be different. The damage reduces the energy ratio of some characteristic frequency bands, or increases the energy ratio of other characteristic frequency bands, that is, the energy ratio of the corresponding frequency band before and after will have a difference, such as Figure 5 It can be considered that the energy of the kth characteristic frequency band obtained by wavelet packet transform of the signal collected in the initial test is I k u represents an average level, and the energy ratio I corresponding to the kth characteristic frequency band obtained by the wavelet packet transform of the signal collected in the subsequent test k d of, around I k u Float, in order to construct the wavelet packet damage eigenvector spectrum.

[0044] S4. Define monitoring indicators based on the wavelet packet damage feature vector spectrum.

[0045] Defining monitoring indicators based on wavelet packet damage characteristic vector spectrum Defining monitoring indicators based on wavelet packet damage characteristic vector spectrum specifically includes: introducing energy ratio variation coefficient Define monitoring indicators, IVC reflects I k d Around Ik u When IVC = 0, the structure of the masonry retaining wall 1 is not damaged; when IVC is not 0, there is damage in the structure of the masonry retaining wall 1; and the larger the value of IVC, the more serious the damage in the structure of the masonry retaining wall 1. Therefore, IVC can be used to monitor the damage of the structure of the masonry retaining wall 1.

[0046] S5. Analyze the internal relationship among the monitoring index, earth pressure and retaining wall stability coefficient to determine the stability state of the stone retaining wall 1. Once it is found that the stone retaining wall has entered a critical steady state, the retaining wall needs to be reinforced.

[0047] S51. Before the vibration test, earth pressure boxes need to be buried along the wall height in the soil behind and in front of the wall, and then multiple regular vibration tests are performed. The monitoring indicators will change during each test, and the soil pressure in front of the wall and the soil pressure behind the wall will also change accordingly, resulting in changes in the stability coefficient of the masonry retaining wall 1. Therefore, the change in soil pressure becomes a bridge or link between the monitoring indicators and the stability coefficient. Each monitoring indicator corresponds to a stability coefficient. The data after multiple tests are fitted to obtain a quantitative relationship between the monitoring indicator and the stability coefficient.

[0048] S52. For retaining wall structures, the stability state of the masonry retaining wall 1 is generally determined by the anti-slip stability coefficient and the anti-overturning stability coefficient. Taking the pile-board retaining wall as an example, its anti-slip stability coefficient Ks can be calculated as follows:

[0049]

[0050] The anti-overturning stability coefficient Kt is calculated as follows:

[0051]

[0052] P A is the resultant earth pressure acting on the back of the wall, A is the distance from the point of action of the resultant force to the toe of the wall; P B The resultant earth pressure in front of the wall, B is the distance from the point of action of the resultant force to the toe of the wall, such as Figure 7 shown.

[0053] S53. According to the Code for Design of Building Foundations, the stability status of masonry retaining walls 1 can be divided into three levels: stable, basically stable and unstable. The stability level is determined by the stability coefficient:

[0054] (1) When the anti-slip stability coefficient Ks>1.3 and the anti-overturning stability coefficient Kt>1.6, the stone retaining wall 1 is stable;

[0055] (2) When the anti-slip stability coefficient is 1.0≤Ks<1.3 or the anti-overturning stability coefficient is 1.0≤Kt<1.6, the stone retaining wall 1 is basically stable;

[0056] (3) When the anti-slip stability coefficient Ks < 1.0 or the anti-overturning stability coefficient Kt < 1.0, the stone retaining wall 1 is unstable.

[0057] As the soil pressure changes, the stability coefficient of the retaining wall will increase or decrease, and the collected retaining wall signal will also change accordingly, that is, the monitoring index will also change. When the monitoring index reaches a certain limit value, the retaining wall enters a critical stable state. The stability of the retaining wall can be monitored by monitoring the index, such as Figure 6 shown.

[0058] By monitoring the indicators, the stability of the masonry retaining wall can be determined and the stability of the masonry retaining wall can be monitored. The changes in the collected signals will lead to changes in the monitoring indicators. On the other hand, the soil pressure acting on the retaining wall will change, causing changes in the stability of the retaining wall. When the monitoring indicators reach the limit value, the retaining wall enters a critical stability state, such as Figure 7 shown.

Claims

1. A method for monitoring damage of a stone retaining wall structure, characterized in that: The following steps are involved: S1, regularly stimulate the stone retaining wall and collect signals; S2, performing wavelet packet decomposition on the collected signal; S3, performing wavelet packet frequency band energy spectrum analysis on the decomposed signal, establishing an energy ratio spectrum, creating a characteristic frequency band vector spectrum and constructing a wavelet packet damage characteristic vector spectrum; S4. Define monitoring indicators based on the wavelet packet damage feature vector spectrum; S5. Analyze the intrinsic relationship between monitoring indicators, soil pressure and retaining wall stability coefficient to determine the stability status of the stone retaining wall.

2. A method for monitoring damage of a stone retaining wall structure according to claim 1, characterized in that: In the step S1, the masonry retaining wall is regularly stimulated by a force hammer and signals are collected. Before the test, steel brackets are arranged in advance at various measuring points of the masonry retaining wall, and the horizontal acceleration sensor is horizontally placed on the steel bracket.

3. A method for monitoring damage of a stone retaining wall structure according to claim 2, characterized in that: After the force hammer is excited, the response generated by the masonry retaining wall is transmitted to the signal acquisition device through the horizontal acceleration sensor, and then transmitted to the computer through the wireless gateway.

4. A method for monitoring damage of a stone retaining wall structure according to claim 1, characterized in that: In step S2, the wavelet packet decomposition specifically includes: selecting an appropriate scale to perform wavelet packet decomposition and reconstruction on the masonry retaining wall signals measured at each period, and obtaining the energy ratio of each frequency band.

5. The method for monitoring damage of a stone retaining wall structure according to claim 1, characterized in that: The step S3 is specifically as follows: sorting each frequency band from high to low according to the energy ratio, establishing an energy ratio spectrum, merging the last 5% of the energy ratio frequency bands into a remaining frequency band, and forming a characteristic frequency band vector spectrum with the first 95% of the frequency bands; on the basis of the characteristic frequency band vector spectrum, calculating the energy ratio deviation on the characteristic frequency band of the retaining wall before and after the period, and constructing a wavelet packet damage characteristic vector spectrum.

6. A method for monitoring damage of a stone retaining wall structure according to claim 5, characterized in that: The energy ratio deviation is calculated as follows: DI k =|I k u -I k d |, where I k u is the energy ratio of the kth characteristic frequency band in the initial test, I k d is the energy ratio of the kth characteristic frequency band in subsequent tests, DI k is the energy ratio deviation.

7. A method for monitoring damage of a stone retaining wall structure according to claim 1, characterized in that: In step S4, the monitoring index is the energy ratio variation coefficient, and the calculation formula is: Among them, IVC is the energy ratio variation coefficient, DI k is the energy ratio deviation, I k u is the energy ratio of the kth characteristic frequency band in the initial test.

8. A method for monitoring damage of a stone retaining wall structure according to claim 7, characterized in that: When the energy ratio variation coefficient is 0, it indicates that the masonry retaining wall has no damage; when the energy ratio variation coefficient is not 0, damage exists in the masonry retaining wall; the larger the value of the energy ratio variation coefficient is, the more serious the damage in the structure is.

9. A method for monitoring damage of a stone retaining wall structure according to claim 1, characterized in that: In step S5, the retaining wall stability coefficient includes the anti-sliding stability coefficient K s and anti-overturning stability coefficient K t , the calculation formula of the anti-slip stability coefficient is: The anti-overturning stability coefficient K t The calculation formula is, Among them, P A is the resultant earth pressure acting on the back of the wall, A is the distance from the point of action of the resultant force to the toe of the wall, P B The resultant force of the earth pressure in front of the wall, B is the distance from the point of action of the resultant force to the toe of the wall.

10. A method for monitoring damage of a stone retaining wall structure according to claim 1, characterized in that: In step S5, the stability states of the stone retaining wall include stable, basically stable and unstable; when the anti-slip stability coefficient is greater than 1.3 and the anti-overturning stability coefficient is greater than 1.6, it is stable; when 1.0≤anti-slip stability coefficient<1.3 or 1.0≤anti-overturning stability coefficient<1.6, it is basically stable; when the anti-slip stability coefficient is less than 1.0 or the anti-overturning stability coefficient is less than 1.0, it is unstable.

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