CN114935513A - Method for predicting generation and expansion of concrete dam body crack based on microseismic signal characteristics - Google Patents
Method for predicting generation and expansion of concrete dam body crack based on microseismic signal characteristics Download PDFInfo
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Abstract
The invention discloses a method for predicting the generation and expansion of cracks of a concrete dam body based on microseismic signal characteristics, which comprises the following steps: loading a graded load on the concrete beam to be tested by adopting a graded maintenance load method, and collecting a bending damage micro-seismic signal of the concrete beam in the load loading process; transforming the microseismic signal by S to obtain an S matrix, performing module solving on each element of the S matrix to obtain an S mode matrix, and obtaining the time-frequency spectrum characteristic of the microseismic signal according to the S mode matrix; acquiring the time-frequency spectrum characteristics of the concrete beam at the deformation stage in the loading process according to the time-frequency spectrum characteristics of the microseismic signals; and collecting the micro-seismic signals of the concrete dam body, comparing the time-frequency spectrum characteristics of the micro-seismic signals of the concrete dam body with the obtained time-frequency spectrum characteristics, and predicting the deformation stage of the concrete dam body. The method can predict and identify the generation and expansion of the concrete dam crack.
Description
Technical Field
The invention relates to the field of data processing, in particular to a method for predicting the generation and expansion of cracks of a concrete dam body based on microseismic signal characteristics.
Background
The microseismic monitoring technology has more successful application cases in the fields of petroleum fracturing, mine safety monitoring, dam slope monitoring, tunnel advanced prediction and the like. The dam concrete belongs to brittle materials, when micro-cracks occur in the dam concrete, the appearance displacement is generally small, the released energy is gradually increased along with the increase of the concrete micro-shock, a large number of micro-cracks are generally formed around potential cracks before a large crack zone is formed, and the micro-crack signals are monitored through the micro-shock so that the occurrence time, the position and the properties of the concrete micro-cracks can be inverted. At present, a microseismic monitoring technology is not applied to monitoring cracks of a huge concrete dam at home and abroad, and the difficulty of monitoring the microseismic cracks of the dam is how to reasonably define the identification principle of precursors and formation of the concrete cracks according to received microseismic events of the concrete.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for predicting the generation and expansion of cracks of a concrete dam body based on microseismic signal characteristics, which comprises the following steps:
step one, loading a graded load on a concrete beam to be tested by adopting a graded maintenance load method, and collecting a bending damage micro-seismic signal of the concrete beam in the load loading process;
step two, obtaining an S matrix after the microseismic signal is subjected to S transformation, performing module calculation on each element of the S matrix to obtain an S mode matrix, and obtaining the time-frequency spectrum characteristic of the microseismic signal according to the S mode matrix;
dividing the deformation stage of the concrete beam in the loading process into an elastic deformation stage, a plastic deformation stage and a damage deformation stage according to a strain curve of the concrete beam in the damage process, and respectively acquiring the time-frequency spectrum characteristics of the micro-seismic signal in the elastic deformation stage, the time-frequency spectrum characteristics of the plastic deformation stage and the time-frequency spectrum characteristics of the damage deformation stage;
and step four, acquiring microseismic signals of the concrete dam body, carrying out S transformation on the microseismic signals of the concrete dam body to obtain an S matrix, solving a model for each element of the S matrix to obtain an S-mode matrix, obtaining the microseismic signal time-frequency spectrum characteristic of the concrete dam body according to the S-mode matrix, comparing the microseismic signal time-frequency spectrum characteristic of the concrete dam body with the time-frequency spectrum characteristic of the elastic deformation stage, the time-frequency spectrum characteristic of the plastic deformation stage and the time-frequency spectrum characteristic of the damage deformation stage obtained in the concrete beam damage process, and predicting the deformation stage of the concrete dam body.
Further, the step of loading the graded load to the concrete beam to be tested by adopting a graded maintenance load method comprises the following steps:
firstly, obtaining the maximum load of a concrete beam to be tested, horizontally placing one side of the concrete beam to be tested on a left support and a right support which are symmetrically arranged, applying the load at the geometric center of the concrete beam to be tested at the other side, and according to the distance between the two supports of the concrete beam to be tested
Maximum bending moment value of beam
Width of concrete beam to be tested
The height of the concrete beam to be tested is
The bending resistance section coefficient is
Maximum bending moment of the concrete beam to be tested under the action of midspan total load
From the formula:
bending resistance section coefficient of rectangular section
Substituting the formula to obtain:
conversion is carried out to obtain:
therein are
The standard value of the tensile strength of the concrete axle center is obtained; p is the maximum load;
and loading the graded load to the maximum load by adopting a graded maintenance load method, loading the load from the maximum load until the concrete beam to be tested is fractured, and acquiring the micro-seismic signals in the graded load loading process.
Further, the method includes the following steps of transforming the microseismic signal by S to obtain an S matrix, performing modulo calculation on each element of the S matrix to obtain an S-mode matrix, and obtaining the time-frequency spectrum characteristic of the microseismic signal according to the S-mode matrix:
the S transform is defined as:
the inverse S-transform is defined as:
in the formula: h (t) represents the microseismic signal,
and f respectively represent time and frequency,
is an S matrix of the microseismic signals after S transformation, t is microseismic signal time, and i is an imaginary number; and transforming the concrete microseismic signal by S to obtain an S matrix, solving a model of each element of the S matrix to obtain an S-mode matrix, wherein the S-mode matrix represents the change condition of the amplitude along with time and frequency, and the S-mode matrix determines the time frequency spectrum distribution characteristic of the concrete microseismic signal.
Furthermore, according to the strain curve of the concrete beam in the failure process, the deformation stage of the concrete beam in the loading process is divided into an elastic deformation stage, a plastic deformation stage and a failure deformation stage, and the elastic deformation stage, the plastic deformation stage and the failure deformation stage are divided according to the slope of the strain curve of the concrete beam in the failure process.
The invention has the beneficial effects that: the method takes the micro-seismic monitoring data of the three-point bending failure test of the concrete beam as a research object, researches the fracture mechanism of the concrete beam through the time-frequency spectrum characteristics of micro-seismic signals, establishes a method for identifying the fracture precursor and the fracture moment of the concrete beam, and predicts and identifies the generation and expansion of the concrete dam body crack according to the identification method.
Drawings
FIG. 1 is a schematic flow chart of a method for predicting crack generation and expansion of a concrete dam based on microseismic signal characteristics;
FIG. 2 is a schematic diagram of a concrete beam failure test;
FIG. 3 is a characteristic diagram of the number of microseismic events during the failure of a concrete beam;
FIG. 4 is a diagram of the spectral characteristics of microseismic signals during the concrete beam failure process.
Detailed Description
The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following.
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention. It is noted that relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.
Furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element identified by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element.
The features and properties of the present invention are described in further detail below with reference to examples.
As shown in fig. 1, the method for predicting the generation and expansion of the crack of the concrete dam body based on the microseismic signal characteristics comprises the following steps:
step one, loading a graded load on a concrete beam to be tested by adopting a graded maintenance load method, and collecting a bending damage micro-seismic signal of the concrete beam in the load loading process;
step two, obtaining an S matrix after the microseismic signal is subjected to S transformation, performing module calculation on each element of the S matrix to obtain an S mode matrix, and obtaining the time-frequency spectrum characteristic of the microseismic signal according to the S mode matrix;
dividing the deformation stage of the concrete beam in the loading process into an elastic deformation stage, a plastic deformation stage and a damage deformation stage according to a strain curve of the concrete beam in the damage process, and respectively acquiring the frequency spectrum characteristics of the micro-seismic signal in the elastic deformation stage, the frequency spectrum characteristics of the plastic deformation stage and the frequency spectrum characteristics of the damage deformation stage;
and step four, acquiring microseismic signals of the concrete dam body, performing S transformation on the microseismic signals of the concrete dam body to obtain an S matrix, performing module calculation on each element of the S matrix to obtain an S-mode matrix, obtaining microseismic signal time-frequency spectrum characteristics of the concrete dam body according to the S-mode matrix, comparing the microseismic signal time-frequency spectrum characteristics of the concrete dam body with the time-frequency spectrum characteristics of the elastic deformation stage, the plastic deformation stage and the damage deformation stage obtained in the concrete beam damage process, and predicting the deformation stage of the concrete dam body.
The method for loading the graded load to the concrete beam to be tested by adopting a graded maintenance load method comprises the following steps:
firstly, obtaining the maximum load of a concrete beam to be tested, horizontally placing one side of the concrete beam to be tested on a left support and a right support which are symmetrically arranged, applying the load at the geometric center of the concrete beam to be tested on the other side, and applying the load according to the distance between the two supports of the concrete beam to be tested
Maximum bending moment value of beam
Width of concrete beam to be tested
The height of the concrete beam to be tested is
Bending resistance section modulus of
Maximum bending moment of the concrete beam to be tested under the action of midspan total load
From the formula:
bending resistance section coefficient of rectangular section
Substituting the formula to obtain:
conversion is carried out to obtain:
therein
The standard value of the tensile strength of the concrete axle center is obtained; p is the maximum load;
and loading the graded load to the maximum load by adopting a graded maintenance load method, loading the load from the maximum load until the concrete beam to be tested is fractured, and acquiring the micro-seismic signals in the graded load loading process.
The method comprises the following steps of transforming the microseismic signals to obtain an S matrix, performing modulus calculation on each element of the S matrix to obtain an S mode matrix, and obtaining the time-frequency spectrum characteristics of the microseismic signals according to the S mode matrix, wherein the method comprises the following steps:
the S transform is defined as:
the inverse S-transform is defined as:
in the formula: h (t) represents the microseismic signal,
and f respectively represent time and frequency,
is an S matrix of the microseismic signals after S transformation, t is microseismic signal time, and i is an imaginary number; and transforming the concrete microseismic signal by S to obtain an S matrix, solving a model of each element of the S matrix to obtain an S mode matrix, wherein the S mode matrix represents the change condition of the amplitude along with time and frequency, and the S mode matrix determines the time frequency spectrum distribution characteristics of the concrete microseismic signal.
According to the strain curve of the concrete beam in the failure process, the deformation stage of the concrete beam in the loading process is divided into an elastic deformation stage, a plastic deformation stage and a failure deformation stage, and the elastic deformation stage, the plastic deformation stage and the failure deformation stage are divided according to the slope of the strain curve of the concrete beam in the failure process.
Specifically, the concrete microseismic data acquisition system adopts an IHMS (induction heating system) microseismic monitoring system, and the main use parameters of the microseismic data acquisition of the three-point bending test of the concrete beam are as follows: sampling frequency (40kHz), sensor sensitivity (30V/g), gain (1 db), sensor threshold (1 mv).
The dimensions of the rolled concrete beam are 300cm x 50cm (length x width x height), the design strength rating is C25(90 days), and the beam age is over 400 days when tested.
The loading mode of the concrete beam failure test adopts a graded maintenance loading method, and the graded loading follows the following principle: (1) loading 20KN on each stage at the stage of 0-60 KN, and pausing for 5 minutes; (2) loading 10KN on each stage at the stage of 60-140 KN, and pausing for 5 minutes; (3) loading 5KN on each stage at the stage of 140-155 KN, and pausing for 10 minutes midway; (4) and adjusting according to the real-time monitoring data of the microseismic and the strain, and performing next-stage loading after the change of the strain data and the microseismic data is kept stable. A concrete beam failure test schematic is shown in fig. 2.
(1) Concrete beam microseismic signal time frequency spectrum characteristics
The characteristic curve of the number of the micro-seismic events of the concrete beam against bending failure is shown in fig. 3, and the curve of the loading process, the cumulative number curve of the micro-seismic events in unit time and the strain curve are comprehensively analyzed to obtain:
the variation trend of the microseismic event cumulative curve of the concrete beam in unit time is basically consistent with that of the strain curve;
according to the slope change rule of the strain curve and the unit time microseismic event cumulative number curve, the concrete beam damage process is divided into three stages: elastic deformation stage (OC section), plastic deformation stage (CF section), destruction deformation stage (FI section), FIG. 4 is a typical microseismic signal time-frequency spectrum characteristic diagram of each stage in the concrete beam destruction process, and the time-frequency spectrum characteristics of the three deformation stages of the concrete beam are as follows:
1) elastic deformation phase (OC section): the applied load at the stage is 0 kN-90 kN, and the corresponding stress (the stress is calculated when the concrete beam is broken) is obtained. A typical micro-seismic signal time-frequency spectrum characteristic diagram of concrete at an elastic deformation stage is shown as A, B, C in figure 4, and it can be seen that a micro-seismic signal of a concrete beam is mainly a single-seismic type micro-seismic signal, the duration time of the single-seismic type micro-seismic signal on a time axis of a time-frequency spectrum is about 5ms, the frequency distribution range is 6 kHz-18 kHz, the single-seismic type micro-seismic signal is intensively distributed at 6 kHz-12 kHz, the amplitude value of an amplitude spectrum is relatively weak, and high-frequency components of the micro-seismic signal tend to be attenuated along with the increase of load and stress. The concrete microseismic signal at the stage is mainly sent out by the fact that primary cracks (cementing materials) with smaller sizes are compacted or tensioned to different degrees (single-seismic microseismic signals) in the pressurizing process of the concrete beam.
2) Plastic deformation phase (CF section): the applied load at this stage is 90kN to 140kN, corresponding to the stress. The typical microseismic signal time-frequency spectrum characteristic diagram of the concrete at the plastic deformation stage is shown as D, E, F in fig. 4, and it can be seen that the microseismic signal time-frequency spectrum characteristic diagram of the concrete beam at the plastic deformation stage is spread for about 15ms on a time axis, and 2 main frequency bands and a low-frequency part exist: around 3kHz, medium-high frequency part: 6 kHz-10 kHz, along with the increase of load and stress, the high-frequency component in the micro-seismic signal is in an attenuation trend, and the low-frequency component of the micro-seismic signal is in an enhancement trend.
The concrete microseismic signal at the stage is a double-seismic microseismic signal (2 main frequencies exist in a time-frequency spectrum characteristic diagram), and compared with the elastic deformation stage of the concrete, the low-frequency (3kHz) component is added, and is mainly generated by local falling off of concrete beam aggregate and a cementing material; but simultaneously with medium-high frequency (6 kHz-10 kHz) components, the concrete beam aggregate and the cementing material are partially fallen off, and the cementing material is compacted or tensioned. And defining the low-frequency (3kHz) and medium-high-frequency (6 kHz-10 kHz) components of the frequency spectrum of the concrete microseismic signal at the stage as the concrete beam fracture precursor.
3) Breaking deformation phase (FI stage): the applied load at this stage is 145 kN to 155KN corresponding to the stress. The typical microseismic signal time-frequency spectrum characteristic diagram of the concrete at the stage of damage deformation is shown as G, H, I in fig. 4, and it can be seen that the microseismic signal time-frequency spectrum characteristic diagram at the stage of plastic deformation of the concrete beam spreads for about 15-20 ms on a time axis, and 2 main frequency bands and low-frequency parts exist: around 3kHz, medium-high frequency part: 6 kHz-10 kHz (the moment of destruction is high frequency 6 kHz-18 kHz). With the increase of load and stress, the medium frequency (6 kHz-10 kHz) component of the microseismic signal continues to show an attenuation trend, the low frequency (3kHz) component of the microseismic signal obviously shows an enhancement trend, and the low frequency signal is stronger than the high frequency signal (figure 4H).
The concrete microseismic signal at the stage is a double-seismic microseismic signal (2 dominant frequencies exist in a time-frequency spectrum characteristic diagram), compared with the elastic-plastic deformation stage of the concrete, the low-frequency (3kHz) component of the microseismic signal obviously dominates, and is represented as that the concrete aggregate and the cementing material partially or completely fall off to cause micro-fracture and through, but simultaneously the middle-high frequency (6 kHz-10 kHz) component is also accompanied, so that the cementing material is compacted or tensioned when the concrete beam aggregate and the cementing material fall off. The amplitudes of high-frequency (6 kHz-18 kHz) and low-frequency (3kHz) components of a time-frequency spectrum of a microseismic signal at the moment of breakage of a concrete beam are obviously enhanced (I in figure 4), and when the frequency spectrum of the microseismic signal is defined to take the low-frequency (3kHz) and high-frequency (6 kHz-18 kHz) components as main components, the frequency spectrum is taken as a concrete damage sign.
As can be seen from FIG. 4, the spectral characteristics of the microseismic signals during the concrete beam failure process reproduce the three processes of concrete beam failure and the mechanism for generating the microseismic signals. The method comprises the following steps:
the elastic deformation stage is that the microscopic primary crack defects are compacted or tensioned (single-shock type microseismic signals);
in the plastic deformation stage, the micro-fracture gradually expands under the action of load and is locally communicated (double-shock type micro-seismic signals);
in the failure deformation stage, the micro-cracks are expanded under the action of load and communicated to form macrocracks, and the beam is broken after the macrocracks are expanded (double-shock type micro-seismic signals).
The method for researching the concrete beam fracture mechanism through the microseismic signal time-frequency spectrum characteristics comprises the following steps of:
1) the spectral characteristics of the microseismic signals in the concrete beam damage process reappear the three processes of concrete beam damage and the mechanism for generating the microseismic signals. The method comprises the following steps:
the elastic deformation stage is that the microscopic primary crack defects are compacted or tensioned (single-shock type micro-shock signals);
the plastic deformation stage is that the micro-fracture gradually expands and is partially communicated under the action of load (double-shock type micro-fracture)Seismic signals);
in the failure deformation stage, the micro-cracks are expanded under the action of load and communicated to form macrocracks, and the beam is broken after the macrocracks are expanded (double-shock type micro-seismic signals).
2) A concrete beam failure precursor: the microseism signal of concrete beam entering plastic deformation stage is mainly two type microseism signals, and the time frequency spectrum is spread on the time axis for about 15ms, has 2 main frequency bands, the low frequency part: around 3kHz, medium-high frequency part: 6kHz to 10 kHz. In short, the microseismic signal time spectrum is mainly composed of low-frequency (3kHz) and medium-high frequency (6 kHz-10 kHz) components and is a concrete fracture precursor.
(2) Concrete dam crack micro-seismic signal time frequency spectrum characteristic
In order to apply the micro-seismic signal time-frequency spectrum characteristics in the concrete beam damage process to the concrete dam body and predict the generation and the expansion of the concrete dam body cracks, a micro-seismic monitoring system is built in a dam corridor, micro-seismic signals in the concrete dam crack generation and expansion process are monitored in real time, and the deformation stage of the concrete dam body cracks is predicted according to the micro-seismic signal time-frequency spectrum characteristics. Specifically, the concrete dam body microseismic event frequency spectrum is typically characterized as follows:
event A is a concrete microseismic event at the depth of 1.2m below the bottom plate of the existing gallery, the microseismic signal is a multi-seismic signal, the duration is about 10-15 ms, and 2 main frequency bands and low-frequency parts exist: 2-3 kHz or so, high frequency part: 5kHz to 14 kHz. The typical concrete microseismic event belongs to a microseismic signal sent by the gradual expansion of the microcracks and the local penetration (the cementing material is compacted or tensioned, and the aggregate and the cementing material are partially fallen off) in the plastic deformation stage of the concrete by combining the spectral characteristics of the microseismic signal in the elastic deformation stage, the plastic deformation stage and the damage deformation stage of the concrete model.
The event B, C, D is a concrete microseismic event at a depth of 3-7 m below the bottom plate of the existing gallery, the microseismic signal is a single-seismic signal, the duration time is about 5-7 ms, the frequency is distributed at 6 kHz-20 kHz, and the main frequency is distributed at about 8-10 kHz. The typical concrete microseismic event belongs to a microseismic event sent out when a colloid material is compacted or stretched in the elastic deformation stage of the concrete by combining the time-frequency spectrum characteristics of microseismic signals in the elastic deformation stage, the plastic deformation stage and the damage deformation stage of a concrete model.
According to the micro-seismic events monitored before and after water storage, the frequency spectrum characteristics are respectively calculated, and the proportion of high-frequency (single-seismic type) events and low-frequency + high-frequency (multi-seismic type) events is counted, as shown in the following table.
Spectrum characteristic comparison table for on-site monitoring microseismic event before water storage
Before water storage: in 3-10 months of 2014, the high-frequency single-shock type microseismic signals of the microseismic event signals account for 92.3 percent of the total event number, and the low-frequency and high-frequency superposed multi-shock type and high-frequency single-shock type microseismic mixed signals account for 7.7 percent of the total event. The frequency component of the micro-seismic signal is in inverse proportion to the fracture scale, namely the high frequency corresponds to the small-scale cracks, the low frequency corresponds to the large-scale cracks, the concrete micro-seismic signal before water storage is mainly of a high-frequency single-seismic type, and the phenomenon that the low-frequency micro-seismic signal is abnormally increased does not occur.
After water storage: during 11 months-2015 10 months in 2014, the high-frequency single-seismic microseismic signals of the microseismic event signals account for about 90% of the total event number, and the mixed signals of the multi-seismic single-seismic and high-frequency single-seismic microseismic signals with the superposed low frequency and high frequency account for about 10% of the total event. The frequency component of the microseismic signal is in inverse proportion to the fracture scale, namely, the high frequency corresponds to small-scale cracks, the low frequency corresponds to large-scale cracks, the concrete microseismic signal after water storage is still mainly of a high-frequency single-shock type, and the phenomenon of abnormal increase of the low-frequency microseismic signal does not occur.
The major dam concrete microseismic events before and after water storage are mainly high-frequency single-seismic type, and the proportion is more than 90%, which indicates that the microseismic events generated by the dam concrete are in an elastic deformation stage and do not generate plastic deformation and destructive deformation.
The foregoing is illustrative of the preferred embodiments of this invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and that various other combinations, modifications, and environments may be resorted to, falling within the scope of the concept as disclosed herein, either as described above or as apparent to those skilled in the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (4)
1. The method for predicting the generation and expansion of the concrete dam body crack based on the microseismic signal characteristics is characterized by comprising the following steps:
step one, loading a graded load on a concrete beam to be tested by adopting a graded maintenance load method, and collecting a bending damage micro-seismic signal of the concrete beam in the load loading process;
step two, obtaining an S matrix after the microseismic signal is subjected to S transformation, performing module calculation on each element of the S matrix to obtain an S mode matrix, and obtaining the time-frequency spectrum characteristic of the microseismic signal according to the S mode matrix;
dividing the deformation stage of the concrete beam in the loading process into an elastic deformation stage, a plastic deformation stage and a damage deformation stage according to a strain curve of the concrete beam in the damage process, and respectively acquiring the time-frequency spectrum characteristics of the micro-seismic signal in the elastic deformation stage, the time-frequency spectrum characteristics of the plastic deformation stage and the time-frequency spectrum characteristics of the damage deformation stage;
and step four, acquiring microseismic signals of the concrete dam body, performing S transformation on the microseismic signals of the concrete dam body to obtain an S matrix, performing module calculation on each element of the S matrix to obtain an S-mode matrix, obtaining microseismic signal time-frequency spectrum characteristics of the concrete dam body according to the S-mode matrix, comparing the microseismic signal time-frequency spectrum characteristics of the concrete dam body with the time-frequency spectrum characteristics of the elastic deformation stage, the plastic deformation stage and the damage deformation stage obtained in the concrete beam damage process, and predicting the deformation stage of the concrete dam body.
2. The method for predicting the generation and expansion of the crack of the concrete dam body based on the microseismic signal characteristics as claimed in claim 1, wherein the step of loading the graded load to the concrete beam to be tested by adopting a graded maintenance load method comprises the following steps:
firstly, obtaining the maximum load of a concrete beam to be tested, horizontally placing one side of the concrete beam to be tested on a left support and a right support which are symmetrically arranged, applying the load at the geometric center of the concrete beam to be tested on the other side, and applying the load according to the distance between the two supports of the concrete beam to be tested
Maximum bending moment value of beam
Width of concrete beam to be tested
The height of the concrete beam to be tested is
Bending resistance section modulus of
Maximum bending moment of the concrete beam to be tested under the action of midspan total load
From the formula:
bending resistance section coefficient of rectangular section
Substituting the formula to obtain:
conversion is carried out to obtain:
therein
Is a standard value of the tensile strength of the concrete axle center; p is the maximum load;
and loading the graded load to the maximum load by adopting a graded maintenance load method, loading the load from the maximum load until the concrete beam to be tested is fractured, and acquiring the microseismic signal in the graded loading process.
3. The method for predicting the generation and expansion of the cracks of the concrete dam body based on the microseismic signal characteristics as claimed in claim 2, wherein the method comprises the following steps of transforming the microseismic signal to obtain an S matrix, performing modulo calculation on each element of the S matrix to obtain an S mode matrix, and obtaining the microseismic signal time-frequency spectrum characteristics according to the S mode matrix:
the S transform is defined as:
the inverse S-transform is defined as:
in the formula: h (t) represents the microseismic signal,
and f respectively represent time and frequency,
is an S matrix of the microseismic signals after S transformation, t is microseismic signal time, and i is an imaginary number; transforming the concrete microseismic signal to obtain S matrix, and matchingAnd (3) solving a mode of each element of the S matrix to obtain an S mode matrix, wherein the S mode matrix represents the change condition of the amplitude along with time and frequency, and the S mode matrix determines the frequency spectrum distribution characteristics of the concrete microseismic signal.
4. The method for predicting the generation and expansion of the crack of the concrete dam body based on the microseismic signal characteristics as claimed in claim 3, wherein the deformation stage of the concrete beam in the loading process is divided into an elastic deformation stage, a plastic deformation stage and a failure deformation stage according to the strain curve of the concrete beam failure process, and the elastic deformation stage, the plastic deformation stage and the failure deformation stage are divided according to the slope of the strain curve of the concrete beam failure process.
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